QT dispersion and sudden unexpected death in chronic heart failure

Exploring the association of natriuretic peptides with QTc interval in hemodialysis patients

BACKGROUND

In patients undergoing hemodialysis (HD), cardiovascular (CV) disease, particularly sudden cardiac death (SCD), is a major cause of mortality. Independent predictors of SCD include a prolonged QT interval on electrocardiography (ECG) and elevated levels of natriuretic peptides (NPs). This study explores the association between the QTc interval and NPs in HD patients.

METHODS

This cross-sectional study involved 207 HD patients, having a heart rate of 57 to 103 bpm, displaying sinus rhythm and no extrasystoles in ECG reports. Before the 2nd HD of the week, we conducted ECG and blood tests for atrial NP (ANP), brain NP (BNP), and N-terminal proBNP (NT-proBNP). The heart rate-corrected QT (QTc) was calculated using Bazett formula. Our analysis focused on the association between QTc and each NP, along with evaluating clinically relevant variables related to the QTc interval.

RESULTS

Univariate analyses indicated robust correlations among the NPs, with each NP significantly associated with the QTc interval. Multiple regression analyses of the three NPs revealed that NT-proBNP demonstrated the strongest predictive ability for the QTc interval. Independent predictors of prolonged QTc included lower corrected calcium (cCa) levels (p = 0.001), lower potassium (K) levels (p < 0.001), and higher log NT-proBNP (p = 0.004).

CONCLUSION

In HD patients, NT-proBNP shows a stronger link with the QTc interval than BNP or ANP. Integrating clinical management considering both QTc and log NT-proBNP levels might help reduce CV events. Additionally, vigilance regarding low K or cCa levels is recommended from the perspective of the QTc interval.

Using a Failing Human Ventricular Cardiomyocyte Model to Re-Evaluate Ca2+ Cycling, Voltage Dependence, and Spark Characteristics

Previous studies have observed alterations in excitation-contraction (EC) coupling during end-stage heart failure that include action potential and calcium (Ca2+) transient prolongation and a reduction of the Ca2+ transient amplitude. Underlying these phenomena are the downregulation of potassium (K+) currents, downregulation of the sarcoplasmic reticulum Ca2+ ATPase (SERCA), increase Ca2+ sensitivity of the ryanodine receptor, and the upregulation of the sodium-calcium (Na=-Ca2+) exchanger. However, in human heart failure (HF), debate continues about the relative contributions of the changes in calcium handling vs. the changes in the membrane currents. To understand the consequences of the above changes, they are incorporated into a computational human ventricular myocyte HF model that can explore the contributions of the spontaneous Ca2+ release from the sarcoplasmic reticulum (SR). The reduction of transient outward K+ current (Ito) is the main membrane current contributor to the decrease in RyR2 open probability and L-type calcium channel (LCC) density which emphasizes its importance to phase 1 of the action potential (AP) shape and duration (APD). During current-clamp conditions, RyR2 hyperphosphorylation exhibits the least amount of Ca2+ release from the SR into the cytosol and SR Ca2+ fractional release during a dynamic slow-rapid-slow (0.5-2.5-0.5 Hz) pacing, but it displays the most abundant and more lasting Ca2+ sparks two-fold longer than a normal cell. On the other hand, under voltage-clamp conditions, HF by decreased SERCA and upregulated INCX show the least SR Ca2+ uptake and EC coupling gain, as compared to HF by hyperphosphorylated RyR2s. Overall, this study demonstrates that the (a) combined effect of SERCA and NCX, and the (b) RyR2 dysfunction, along with the downregulation of the cardiomyocyte's potassium currents, could substantially contribute to Ca2+ mishandling at the spark level that leads to heart failure.

Is the development of arrhythmia predictable in rheumatoid arthritis?

Objectives

This study aimed to determine whether there is a difference in the electrocardiography (ECG) measurements of healthy controls and rheumatoid arthritis (RA) patients and to predict whether they can be used to determine the risk of arrhythmia in patients.

Patients and methods

The prospective study included 50 cardiac asymptomatic RA patients (38 males, 12 females; mean age: 46.8±9.1 years; range, 18 to 60 years) who met the 2010 American College of Rheumatology/European Alliance of Associations for Rheumatology RA criteria and 50 healthy volunteers (34 males, 16 females; mean age: 43.4±10.4 years; range, 18 to 60 years) as a control group between June 1, 2022, and August 31, 2022. Disease activity of the patients was calculated with the Disase Activity Score (DAS28). Heart rate, minimum and maximum QT intervals, QT dispersion, minimum and maximum P waves, P wave dispersion (Pd), minimum and maximum Tp-e intervals, Tp-e dispersion, minimum and maximum corrected QT (QTc) intervals, QTc dispersion, and the Tp-e/QTc ratio in ECGs were calculated.

Results

The mean disease duration of the RA group was 9.09±5.74 years. The mean C-reactive protein level was 9.83±8.29, the mean erythrocyte sedimentation rate was 26.12±16.28 mm/h, and the mean DAS28 was 3.03±0.37. There was a statistically significant increase in the maximum P wave, Pd, maximum QT, QT dispersion, maximum QTc, QTc dispersion, maximum Tp-e, Tp-e dispersion, and Tp-e/QTc dispersion parameters in the RA group compared to the control group, while there was a significant decrease in the minimum P wave, minimum QT, and minimum QTc parameters.

Conclusion

In our study, the Pd, QTc dispersion, Tp-e dispersion, and Tp-e/QTc dispersion values of our patients, which indicate the risk of atrial and ventricular arrhythmia, were found to be significantly higher. This finding suggests that our patients had an increased risk of cardiac morbidity and mortality. Arrhythmias are the likely source of the increase in sudden cardiac death in RA, and these new indicators measured on ECG can be used as standardized cardiovascular morbidity and mortality indicators in the future.

Cardiac Arrhythmias in Pulmonary Arterial Hypertension and Chronic Thromboembolic Pulmonary Hypertension: Mechanistic Insights, Pathophysiology, and Outcomes

Arrhythmias are increasingly recognized as severe complications of precapillary pulmonary hypertension, encompassing pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). Despite their significant contribution to symptoms, morbidity, in-hospital mortality, and potentially sudden death in PAH/CTEPH, there remains a lack of comprehensive data on epidemiology, pathophysiology, and outcomes to inform the management of these patients. This review provides an overview of the latest evidence on this subject, spanning from the molecular mechanisms underlying arrhythmias in the hypertrophied or failing right heart to the clinical aspects of epidemiology, diagnosis, and treatment.

Cardiac Arrhythmia Risk after Anti-Cancer Drug Exposure and Related Disease Molecular Imaging Outlook: A Systematic Review, Meta-Analysis, and Network Meta-Analysis

BACKGROUND

Chemotherapy is the main first-line treatment, but there is a problem of adverse reactions to systemic drugs. Chemotherapeutic agents may cause adverse effects on the body, influencing the prognosis. Whether the clinical application of anthracyclines is associated with an increased arrhythmic risk remains controversial. To evaluate the arrhythmic risk of anthracyclines as a class, and the comparative risk for each drug, we conducted a systematic review, meta-analysis, and network meta-analysis.

METHODS

PubMed, Web of Science, EMBASE, and the Cochrane Library were searched, up to March 2022, for randomized controlled trials, cohort studies, and case-control studies that investigated the association between anthracyclines treatment and the risk of arrhythmia. We followed the PRISMA 2020 guidelines for data selection and extraction. Outcomes were pooled using fixed effects models in cohort studies and randomized controlled studies, and random models in single-arm studies. Direct and indirect comparisons in network meta-analysis were performed using frequentist methods.

RESULTS

In total, 4 cohort studies, 8 RCTs, and 18 single-arm studies were included in our analysis. Anthracyclines' use was associated with a statistically significant 90% increase in the risk of arrhythmia (odds ratio [OR] 1.90; 95% confidence interval [CI] 1.62-2.24) and a 114% increase in the risk of supraventricular arrhythmia (OR 2.14; 95% CI 1.18-3.89). And the single-arm studies also indicated that the incidence of arrhythmia rate is 20% and the 95% CI is 15/100-25/100. Epirubicin ranked most likely to have the highest risk of arrhythmia compared with non-anthracycline antineoplastic drugs in the analysis (OR 43.07 [95% CI 2.80-2105.83]) by network meta-analysis.

CONCLUSIONS

Our findings show a significant association between anthracyclines' use and an increased risk of arrhythmia, especially supraventricular arrhythmia. Epirubicin ranked with the highest probability of arrhythmia. These results indicated that cardiac rhythm should be strictly monitored during the application of anthracyclines in clinical practice, and a possible therapy for anthracycline-associated arrhythmia should be explored. Molecular imaging technology is an important means to study the mechanism of drug action on cardiac electrophysiology in the future. By imaging molecular targets in cardiac cells, the effects of drugs on the electrophysiological properties of cardiac cells can be understood, which provides information for the development of safer and more effective drugs.

Acute Mesenteric Ischemia: The Diagnostic Value of QT Parameters and their Relationship with CT Findings

BACKGROUND

One of the greatest challenges in the diagnosis of acute mesenteric ischemia (AMI) is the lack of specific laboratory tests that support multidetector computed tomography (CT). Our aim is to investigate the diagnostic value of electrocardiographic QT parameters in AMI and their relationship with CT findings.

MATERIALS AND METHODS

Patients who were admitted to the emergency department with abdominal pain were recruited retrospectively from the hospital information system. Grouping was carried out on the basis of AMI (n=78) and non-AMI (n=78). In both groups, the corrected QT (QTc) and QT dispersion (QTD) were measured on electrocardiographs, and the qualitative and quantitative CT findings were evaluated on CT examinations.

RESULTS

The QTc and QTD values were higher in the AMI group. The median QTc values were 456.16 (IQR: 422.88-483.16) for the AMI group and 388.83 (IQR: 359.74-415.83) for the control group (p<0.001), and the median QTD values were 58 (IQR: 50.3-68.25) for the AMI group and 46 (IQR: 42-50) for the control group (p<0.001). In the CT analysis, the QTc values were significantly higher among AMI patients, with images of paper-thin bowel walls and the absence of bowel wall enhancement (p=0.042 and p=0.042, respectively). Meanwhile, the QTD values were significantly higher among patients with venous pneumatosis findings on CT (p=0.005). In the regression analysis, a significant relationship was found between the QT parameters and AMI (p<0.001). For QTc, an AUC of 0.903 (95% CI: 0.857-0.950, p<0.001), a sensitivity of 80.8%, and a specificity of 82.3% were found. For QTD, an AUC of 0.821 (95% CI: 0.753-0.889, p<0.001), a sensitivity of 73.1%, and a specificity of 82.3% were found.

CONCLUSION

We found the QTc and QTD values to be significantly higher among AMI patients. Furthermore, we found a significant relationship between the CT findings and QTc and QTD and a significant relationship between survival and QTc in the AMI group.

Electrocardiographic measurements in children with pre-dialysis chronic kidney disease and undergoing kidney replacement therapy

Cardiovascular diseases are the main causes of morbidity in children with chronic kidney disease (CKD). Electrocardiography (ECG) can provide important information about cardiac functions and parameters associated with sudden cardiac death. This study aims to evaluate the potentially dangerous changes in CKD and kidney replacement therapies by ECG and to determine the value of ECG in predicting cardiovascular outcome compared with echocardiography. 101 patients with CKD were divided into subgroups according to treatment modalities as pre-dialysis CKD, hemodialysis (HD), peritoneal dialysis (PD) and kidney transplantation (KTx). Differences in anthropometric measurements, laboratory results, blood pressures, ECG monitoring were compared within groups as well as with 40 healthy controls. Available echocardiographic findings were noted. In the patients, HD group had highest frequency of hypertension. ECG revealed prolonged QTc as more frequent (16.8% vs 0%, p = 0.006) and higher QTcD (56.7 ± 6.5 vs 39.9 ± 5.1 ms, p = 0.001) in the patients compared to controls, especially in dialysis patients, whereas lowest values were in KTx subgroup. Left ventricular (LV) hypertrophy (LVH) was more frequent (47.1%) in HD compared to other CKD subgroups in ECG (p = 0.052). Echocardiography also showed LV mass index as highest in HD and lowest in KTx (121.4 ± 55.7 vs 63.7 ± 18.3 g/m2, p = 0.000), with numerically highest LVH in HD (58.3%, p = 0.063).  Conclusion: ECG can be used to detect cardiovascular problems in patients with CKD, especially in HD. As ECG results were in line with echocardiography, patients with ECG abnormalities suggestive of LVH should be referred for echocardiographic assessment. What is Known: • Cardiovascular diseases such as coronary artery disease, congestive heart failure, arrhythmias and sudden cardiac death are major causes of morbidity and mortality in chronic kidney disease. • Electrocardiography has significant advantages in demonstrating cardiac functions in children because it is readily available, non-invasive and often non-experts can interpret the results. What is New: • The heart rate is higher, QTc is longer and QTcD is higher in dialysis patients and the prolonged QTc is more frequent in patients with underlying glomerular diseases. • Left ventricular hypertrophy is more common in HD patients and those with hypertension, hypercalcemia, anemia or glomerular etiology. The cardiovascular risky conditions are less frequent in the patients with kidney transplantation.

Mid-Term Electrical Remodeling after Percutaneous Atrial Septal Defect Closure with GCO Device in a Pediatric Population

BACKGROUND AND AIM

The GORE® CARDIOFORM (GCO) septal occluder is an atrial septal defect/patent foramen ovale closure device with theoretical advantages over other commercialized devices thanks to its softness and anatomical compliance. Our aim was to evaluate the short- and medium-term electrocardiographic changes after percutaneous ASD closure with GCO in a pediatric population.

METHODS

We enrolled 39 patients with isolated ASD submitted to trans-catheter closure from January 2020 to June 2021. ECG was performed before, at 24 h and 6 months after the procedure. P wave dispersion, QTc and QTc dispersion were calculated. ECG Holter was recorded at 6 months after implantation.

RESULTS

Patients' age and body surface area (BSA) were 8.2 ± 4.2 years and 1.0 ± 0.3 m2 respectively. At the baseline, mean P wave dispersion was 40 ± 15 msec and decreased at 24 h (p < 0.002), without any further change at 6 months. At 24 h, PR conduction and QTc dispersion significantly improved (p = 0.018 and p < 0.02 respectively), while the absolute QTc value considerably improved after 6 months. During mid-term follow-up, QTc dispersion remained stable without a significant change in PR conduction. The baseline cardiac frequency was 88.6 ± 12.6 bpm, followed by a slight reduction at 24 h, with a further amelioration at 6 months after the procedure (87.3 ± 14.2, p = 0.9 and 81.0 ± 12.7, p = 0.009, respectively). After device deployment, two patients developed transient, self-limited junctional rhythm. One of them needed a short course of Flecainide for atrial ectopic tachycardia. No tachy/brady-arrhythmias were recorded at the 6-month follow-up. ASD closure resulted in a marked decrease in right heart volumes and diameters at 6 months after percutaneous closure.

CONCLUSIONS

Percutaneous ASD closure with the GCO device results in significant, sudden improvement of intra-atrial, atrio-ventricular and intraventricular electrical homogeneity. This benefit persists unaltered over a medium-term follow-up. These electrical changes are associated with a documented positive right heart volumetric remodeling at mid-term follow-up.

Increased Dispersion of Ventricular Repolarization as an Arrhythmic Risk Marker in Drug-free Patients With Major Depressive Disorder: A Preliminary Comparative Study

OBJECTIVE

Drug-free patients with major depressive disorder (MDD) are understudied in terms of increased risk for arrhythmias. In this study, we compared changes in corrected QT interval (QTc), QTc dispersion (QTcd), Tpeak-Tend (Tp-e), Tp-e/QT ratio, corrected JT interval (JTc), and JTc dispersion (JTcd), which are considered to be among the risk factors for the emergence of ventricular arrhythmias in patients with MDD.

METHODS

The study involved 50 patients with MDD who had been free of psychotropic medications for at least 1 month and 52 age-matched and sex-matched healthy controls. Illness-related characteristics, including duration of illness and Beck Depression Inventory scores, were recorded. Electrocardiography recordings made under a standardized procedure were performed for all participants, and arrhythmia risk markers were calculated from the electrocardiograms.

RESULTS

The patient group had significantly higher QTcd, JTc, and JTcd values compared with the controls. Among electrocardiogram markers, only Tp-e/QTc was significantly and inversely correlated with the duration of illness, while none of the markers was associated with Beck Depression Inventory scores.

CONCLUSIONS

Alterations in electrocardiogram-derived markers of ventricular arrhythmia, which can be obtained easily and inexpensively, can be evaluated for the prediction and prevention of severe cardiac conditions in patients with MDD and considered in selecting the safest antidepressant options available.

Evaluation of the Corrected QT Interval with Bazett’s Method in Cavalier King Charles Spaniel Dogs with Myxomatous Mitral Valve Disease

Myxomatous mitral valve disease (MMVD) is one of the most common heart diseases in dogs. The disease progresses faster in Cavalier King Charles Spaniel (CKCS) dogs and occurs at an earlier age. QT interval length reflects abnormalities in ventricular repolarization which may predispose to the formation of fatal arrhythmias such as torsades de pointes. A fast and accurate assessment is therefore essential. The study aimed to examine the changes in QT duration in MMVD cases of CKCS and to calculate the corrected QT durations with Bazett’s formula in various stages of the disease. The study included 20 CKCS dogs of both genders, various ages and weights, and different stages of MMVD (n=6 in B1 stage, n=6 in B2 stage, and n=8 in C stage), and 5 healthy CKCS which were included in the control group. Clinical, radiological, hematological, biochemical, echocardiographic, and electrocardiographic examinations were performed. The corrected QT interval duration in the MMVD group was longer than the control (p<0.05). However, there was no significant difference between B1, B2, and C. It was concluded that the corrected QT interval can give a significant distinction between healthy and MMVD CKCS dogs.

QT interval instability and QRS interval dispersion in healthy cats and cats with a hypertrophic cardiomyopathy phenotype

OBJECTIVES

Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats. Electrocardiographic (ECG) analysis can help with the diagnosis of HCM and also in the investigation of the secondary consequences of the disease. This study investigated ECG markers of QT interval variability (total instability [TI], short-term instability [STI], long-term instability [LTI], QT variance [QTv]), mean QT interval (QTa) and QT interval corrected for heart rate (QTac), as well as the duration (QRSd) and dispersion (QRSv) of the QRS interval in healthy cats and in those with HCM.

METHODS

Data were collected from 63 domestic cats: 40 in the control group and 23 in the HCM group. Fifty consecutive QT intervals were recorded for all cats and then QTa, QTac, QTv, TI, LTI and STI were calculated. QRSd and QRSv were also obtained for all animals. A Mann-Whitney U-test was used for group comparison. Receiver operating characteristic curves were plotted to evaluate the sensitivity and specificity of all markers for HCM. Logistic regression analysis was performed to assess the risks of cats having HCM, based on the studied indexes.

RESULTS

QTa (P <0.01), QTac (P <0.01), QRSd (P <0.01) and STI (P = 0.02) were higher in the HCM group. QTa >158.8 ms, QTac >27.4 ms and QRSd >0.045 s had an accuracy of 77.4%, 68.2% and 80.9%, respectively, in detecting HCM. Logistic regression showed that cats with QTa >158 ms, QTac >27.4 ms and QRSd >0.045 s had a 1.58-, 1,23- and 6.5-fold higher risk, respectively, of developing HCM.

CONCLUSIONS AND RELEVANCE

Cats with HCM had higher ventricular instability as assessed by STI and showed a prolongation of the QT and QRS intervals via the QTa, QTac and QRSd markers. These markers show potential as ancillary screening tools for identifying the presence of HCM.

The Comparison of QTc Dispersion Between Renal Transplant Recipients and Healthy Individuals

Introduction Cardiovascular diseases are the most common cause of death in patients with end-stage renal failure. The increase in QTc interval time and QT dispersion increases the risk of cardiac arrhythmia and mortality. In our study, QT and QTc dispersions (QTcd) of patients who underwent renal transplantation were compared with normal healthy individuals. Methods Electrocardiograms (ECGs) of 80 renal transplant recipients and 70 healthy individuals were taken. QTc dispersion was calculated by using the longest and the shortest QT interval and QT dispersion and Bazett's formula. Results When the groups were compared, similar QT dispersion and QTc dispersion were observed (control group and renal transplant recipient patients: 35 ± 17 ms and 36 ± 16 ms and 52 ± 18 ms and 54 ± 22 ms, respectively). Conclusion No statistical difference was observed between QT and QTc dispersions of renal transplant patients compared to healthy individuals. This result shows that the increase in QT dispersion and pathophysiological mechanisms observed frequently in uremic patients can be reversed by renal transplantation.

Oral Adrenergic Agents Produced Ventricular Fibrillation and QT Prolongation in an Elderly Patient Carrying an RYR2 Variant

Mutant cardiac ryanodine receptor channels (RyR2) are "leaky," and spontaneous Ca²⁺ release through these channels causes delayed afterdepolarizations that can deteriorate into ventricular fibrillation. Some patients carrying RYR2 mutations in type 1 catecholaminergic polymorphic ventricular tachycardia exhibit QT prolongation and are initially diagnosed with long QT syndrome. However, none have been reported to cause drug-induced ventricular fibrillation in patients with RYR2 variants. We describe the first case of an elderly woman with drug-induced QT prolongation and ventricular fibrillation who carried a novel RYR2 variant but no other mutations related to long QT syndrome. Oral adrenergic agents might induce QT prolongation and subsequent ventricular fibrillation in patients carrying an RYR2 variant. Screening for RYR2 could be valuable in patients with suspected drug-induced long QT syndrome.

Comparison of QT dispersion before and after PDA device closure in pediatrics

Background

Numerous studies have shown that QT dispersion (QTd) can be a suitable criterion for risk assessment of arrhythmia in patients with congenital heart disease. Pulmonary arterial hypertension (PAH) increases the risk of cardiac arrhythmia by changing ventricular repolarization homogeneity. In this study, we assessed QTd changes after PDA device closure and the effect of PAH on these changes.

Methods

Between October 2018 and March 2021, 97 patients (48 males; 49 females; mean age 31.36 ± 4.26 months; range 3 months to 14 years) who satisfied the primary inclusion criteria and did not meet the exclusion criteria and underwent PDA device closure intervention were included in the study. Echocardiography was performed before the procedure. QT corrected (QTc), and QTd and PR intervals were measured according to the patients’ standard 12‐lead ECGs in two periods, preoperative (1 day) and after (3 months).

Results

In the general group, QTc and QTd decreased significantly after PDA closure. Based on our classification of the patients in two groups of high PAP and normal PAP, the three parameters QTc, QTd, and PR interval were assessed separately in the two groups. All three parameters decreased significantly in the normal PAP and high PAP groups.

Conclusions

However, a left‐to‐right shunt through the patent ductus arteriosus can affect ventricular repolarization; this effect seems to be particularly more significant when there is pulmonary hypertension.

Estimation of cardiac QTc intervals in people prescribed antipsychotics: a comparison of correction factors

BACKGROUND

A prolonged electrocardiogram (ECG) QT interval is associated with cardiac events and increased mortality. Antipsychotics can prolong the QT interval. The QT interval requires correction (QTc) for heart rate using a formula or QT-nomogram. The QT and QTc can be calculated automatically by the ECG machine or manually; however, machine-measured QT(c) intervals may be inaccurate.

OBJECTIVE

We aimed to investigate the mean QTc and proportion of prolonged QTc intervals in people taking antipsychotic medicines.

METHODS

We conducted an observational retrospective chart review and data analysis of all consecutive patients taking antipsychotics, with an ECG record, admitted to the psychiatric unit of a large tertiary hospital in Brisbane, Australia, between 1 January 2017 and 30 January 2019. We investigated the mean QTc of people taking antipsychotics to determine differences using (a) machine versus manual QT interval measurement and (b) QTc correction formulae (Bazett, Fridericia, Framingham, Hodges and Rautaharju) and the QT-nomogram. We also determined the number of people with a prolonged QTc using different methods and compared rates of prolonged QTc with antipsychotic monotherapy and polypharmacy.

RESULTS

Of 920 included people, the mean (±SD) machine-measured, Bazett-corrected QT interval (recorded from the ECG) was 435 ms (±27), significantly longer (p < 0.001) than the mean manually measured corrected QT intervals with Fridericia 394 ms (±24), Framingham 395 ms (±22), Hodges 398 ms (±22) and Rautaharju 400 ms (±24) formulae. There were significantly more people with a prolonged QTc using machine-measured QT and the Bazett formula (12.0%, 110/920) when compared with manually measured QT and the Fridericia formula (2.2%, 20/920) or QT-nomogram (0.7%, 6/920). Rates of QTc prolongation did not differ between people taking antipsychotic polypharmacy compared with monotherapy.

CONCLUSION

Machine-measured QTc using the Bazett formula overestimates the QTc interval length and number of people with a prolonged QTc, compared with other formulae and the QT-nomogram. We recommend manually measuring the QT and correcting with the Fridericia formula or QT-nomogram prior to modifying antipsychotic therapies.

Relationship Between Disease Severity and Resting Electrocardiograms of Adults With Sickle Cell Anemia in a Tertiary Institution in Southern Nigeria

Introduction

Sickle cell anemia (SCA) in adults has many clinical manifestations. These manifestations are due to effects of recurrent hemolysis, anemia, and ischemia-reperfusion injury on various organs, including the heart. These factors determine the severity of the disease.

Objectives

The aim of the study was to assess the severity of SCA using a scoring system consisting of clinical and laboratory parameters. In addition, the study aimed to determine the electrocardiographic abnormalities in the adult SCA population.

Study design

This was a cross-sectional, observational study conducted in the medical outpatient clinic of Irrua Specialist Teaching Hospital, Irrua, Nigeria.

Methodology

Sixty SCA patients who were older than 18 years old were recruited for this study between February 2017 and January 2018. Sixty healthy individuals matched for age and sex were recruited to serve as controls. Patients who were pregnant or having an acute crises were excluded from the study. Each participant had an electrocardiogram and a SCA severity score was calculated using their clinical history and complete blood count. Data analysis was carried out using the IBM Statistical Package for Social Sciences Statistics® software, version 21 (IBM SPSS Statistics for Windows, Armonk, NY) and statistical significance assigned to p-values less than 0.05.

Results

Severity scores for SCA ranged between 7 and 24, with a mean score of 14.5 ± 4.04. Out of the 60 patients, 14 (23.3%), 39 (65%), and seven (11.7%) participants met criteria for mild, moderate, and severe disease, respectively. Tachycardia, prolonged QTc, and the presence of ST-segment and T-wave abnormalities were significantly associated with severe SCA (p = 0.024, p = 0.027, and p = 0.018, respectively). There was positive correlation between SCA severity scores and P-wave duration (r = 0.327, p = 0.011), QRS dispersion (r = 0.298, p = 0.021), QTc interval (r = 0.332, p = 0.010), and QTc dispersion (r = 0.320, p = 0.013).

Conclusion

This study demonstrated that moderate and severe forms of SCA are common in our region. Tachycardia, left atrial abnormality, prolonged corrected QT interval, and the presence of ST-segment and T-wave changes are electrocardiographic findings associated with more severe forms of the disease. These abnormalities are significant etiologies of cardiac morbidity and mortality in SCA.

Effect of chelation therapy on arrhythmogenic and basal ECG parameters of lead exposed workers

Lead exposure has etiological role on cardiovascular system diseases as hypertension, atherosclerosis, stroke, and arrhythmic events. In this study, we aimed to compare the basal and arrhythmogenic ECG parameters of lead exposed workers before and after chelation therapy and to evaluate the effect of acute change of blood lead levels on ECG. Fourty consecutive occupationally lead exposed workers were enrolled, demographic, blood, echocardiographic, and electrocardiographic data's were analyzed before and after chelation therapy. Pmax, P min, P Wave Dispersion, and QT Dispersion values which are arrhythmia predictors were significantly lower after chelation therapy compared to values before chelation therapy. Lead exposed workers are under the risk of ventricular and atrial arrythmias and chelation treatment has a positive effect on these parameters.

T-wave peak-end interval and ratio of T-wave peak-end and QT intervals: novel arrhythmogenic and survival markers for dogs with myxomatous mitral valve disease

INTRODUCTION/OBJECTIVES

In the past few years, novel markers such as the interval between the peak and the end of T-wave (Tpte) and Tpte/QT ratio have been shown to have high sensitivity for ventricular arrhythmias and mortality. We analyzed these and other parameters of ventricular repolarization, such as QT interval, QT interval corrected for heart rate (QTc), and QT dispersion (QTd) in dogs with myxomatous mitral valve disease (MMVD). Additionally, we investigated their relationship with the progression of the disease, echocardiographic parameters, and ventricular arrhythmias and assessed their prognostic value with development of clinical signs or mortality as the final outcome.

ANIMALS, MATERIALS AND METHODS

Epidemiological, clinical, echocardiographic, and electrocardiographic data were obtained from 236 dogs with MMVD and 15 healthy dogs. Prognostic and survival information was also recorded for the MMVD group. All ventricular repolarization indices were measured in 10 lead electrocardiographic recordings.

RESULTS

With the exception of the QT interval, most repolarization markers increased along with the frequency of arrhythmias and with the progression of MMVD. The parameters that best identified ventricular arrhythmias (AUC > 0.7) were Tpte (aVR, rV2, average rV2-V10, average rV2-V4) and Tpte/QT (II, aVR, rV2). In survival analysis, statistically significant markers with the highest differences in median survival were Tpte (maximum of any lead, maximum rV2-V10), QTc aVR, and Tpte rV2.

CONCLUSION

Tpte and Tpte/QT are good non-invasive markers for clinical risk stratification in dogs with MMVD.

QT Dispersion and Drug-Induced Torsade de Pointes

Background

Amiodarone causes less drug-induced torsade de pointes (TdP) compared to other class III antiarrhythmics. Two theories proposed for this finding include that amiodarone has less repolarization heterogeneity, and/or decreases early after depolarization (EADs). Corrected QT (QTc) dispersion as measured on a surface electrocardiogram (ECG) represents spatial heterogeneity of ventricular repolarization.

Objective

The purpose of this study was to analyze the difference in QT dispersion between amiodarone and other class III antiarrhythmics and to determine the etiology of TdP.

Methods

This was a retrospective, observational study at Montefiore Medical Center between January 2005 and January 2015. Inclusion criteria were adults >18 years on amiodarone, dofetilide, or sotalol with prolonged QT interval on 12-lead ECG. ECGs were reviewed by three blinded observers. QTc was calculated using the Bazett and Framingham formulas. QTc dispersion was calculated by subtracting the shortest from the longest QTc. Analysis of variance (ANOVA) was applied for comparison between antiarrhythmic groups with Bonferroni correction for multiple comparisons.

Results

A total of 447 ECGs were reviewed and 77 ECGs met inclusion criteria. The average QT dispersion for amiodarone, dofetilide, and sotalol was 0.050, 0.037, and 0.034, respectively (p=0.006) and the average QTc dispersion by Bazett was 0.053, 0.038, and 0.037 (p=0.008) and by Framingham was 0.049, 0.036, and 0.035 (p=0.009), respectively.

Conclusion

Our results show that given the increase in QT dispersion seen with amiodarone, heterogeneous ventricular repolarization as measured by QTc dispersion likely does not account for the lower incidence of drug-induced TdP seen with amiodarone. The ability of amiodarone to decrease EADs via sodium-channel blockade is more likely the explanation for its lower incidence of drug-induced TdP.

Assessment of Ventricular Repolarization in Sickle Cell Anemia Patients: The Role of QTc Interval, Tp-e Interval and Tp-e/QTc Ratio and Its Gender Implication

Background

Many specific and non-specific electrocardiographic abnormalities including ventricular arrhythmias have been reported in subjects with sickle cell anemia (SCA). In SCA patients, cardiac electrical abnormalities may be the leading cause of increased risk of arrhythmias. The corrected QT (QTc) interval, peak to the end of the T wave (Tp-e) interval and associated Tp-e/QTc ratio are promising measures of altered ventricular repolarization and increased arrhythmogenesis risk.

Aim

This study assessed ventricular repolarization abnormalities in subjects with SCA using the QTc interval, Tp-e interval and Tp-e/QTc ratio, and also evaluated the gender differences in these parameters, as well as their determinants.

Methods

Sixty subjects with SCA and 60 healthy control subjects, matched for age and gender, were studied. All participants underwent physical examination, hematological and biochemical evaluation, and 12-lead electrocardiography (ECG) recording. QT and Tp-e intervals were measured from the ECG, and the QTc interval was calculated using Bazett’s formula. Tp-e/QT and Tp-e/QTc ratios were also derived.

Results

QT and QTc intervals were prolonged in subjects with SCA. Tp-e interval, Tp-e/QT ratio and Tp-e/QTc ratio were prolonged in male SCA subjects, with a paradoxical shortening in female SCA subjects. Plasminogen activator inhibitor-1 (PAI-1) was an independent determinant of QTc, while body mass index (BMI) was an independent determinant of both Tp-e interval and Tp-e/QTc ratio.

Conclusion

Our results suggest an elevated risk for ventricular arrhythmogenesis in male SCA subjects. Furthermore, increased BMI and PAI-1 level are possible markers of ventricular repolarization abnormalities in SCA subjects.

Qt Dispersion and Signal-Averaged Electrocardiogram in Hemodialysis and Capd Patients

Objective

The aim of this study was to compare QT dispersion (QTd) and signal-averaged electrocardiogram (SA-ECG) parameters that may predict risk of malignant arrhythmias in patients on hemodialysis (HD), on continuous ambulatory peritoneal dialysis (CAPD), and in controls.

Setting

Controlled cross-sectional study in a tertiary- care setting.

Patients

28 HD (M/F 18/10; mean age 32 ± 9 years), 29 CAPD (M/F 17/12; mean age 34 ± 10 years), and 29 healthy controls (M/F 17/12; mean age 32 ± 8 years) were included.

Interventions

On ECG, minimum (QTmin) and maximum (QTmax) QT duration and their difference (QTd) were measured. In SA-ECG, duration of filtered QRS, HFLA signals less than 40 μV, and RMS voltage (40 ms) were also measured.

Results

Higher serum Ca2+ and lower K+ levels were found in CAPD compared to HD. All QT parameters were increased in HD and CAPD compared to controls. QT dispersion was significantly prolonged in HD compared to CAPD. In HD, QTd was correlated with left ventricular (LV) mass index ( r = 0.53, p = 0.004), but not in CAPD ( r = -0.09, p = 0.63). QT dispersion was significantly prolonged in patients with LV hypertrophy compared to patients without hypertrophy on HD (68 ± 18 ms vs 49 ± 18 ms, p = 0.008). In the analysis of SA-ECG, 3 of the 28 (11%) HD and 2 of the 29 (7%) CAPD patients had abnormal late potentials. Patients on HD and CAPD had significantly higher filtered-QRS duration compared to controls (105 ± 15 ms and 104 ± 12 ms vs 95 ± 5 ms, respectively, p = 0.04). Patients with LV hypertrophy had higher filtered-QRS duration compared to patients without hypertrophy (109 ± 12 ms vs 95 ± 8 ms, p < 0.001).

Conclusion

Dialysis patients had prolonged QTd and increased filtered-QRS duration in SA-ECG compared to controls. Patients on HD had longer QTd than patients on CAPD. QTd has been correlated to LV mass index in HD, but not in CAPD. This difference might be due to the effect of different dialysis modalities on electrolytes, especially the higher serum Ca2+ levels.

Association of QT dispersion with mortality and arrhythmic events-A meta-analysis of observational studies

BACKGROUND

The risk stratification of coronary heart disease (CHD) and/or heart failure (HF) patients with easily measured electrocardiographic markers is of clinical importance. The aim of this meta-analysis is to indicate whether increased QT dispersion (QTd) is associated with fatal and nonfatal outcomes in patients with CHD and/or HF.

METHODS

We systematically searched MEDLINE and Cochrane databases without restrictions until August 15, 2018 using the keyword "QT dispersion". Studies including data on the association between QTd and all-cause mortality, sudden cardiac death (SCD) or arrhythmic events in patients with HF and/or CHD were classified as eligible.

RESULTS

In the analysis including patients with CHD and/or HF, we found that QTd did not differ significantly in patients with SCD compared to no SCD patients while QTd was significantly greater in the group of all-cause mortality patients and in patients who experienced a sustained ventricular arrhythmia. Subgroup analysis showed that in myocardial infarction studies, QTd was significantly higher in patients with an arrhythmic event compared to arrhythmic event-free patients while a nonsignificant difference was found in QTd in patients who died from any cause compared to survivors. Similarly, in HF patients, the QTd was significantly greater in patients with an arrhythmic event while a nonsignificant difference was found regarding all-cause mortality and SCD outcomes.

CONCLUSIONS

QTd has a prognostic role for stratifying myocardial infarction or HF patients who are at higher risk of arrhythmic events. However, no prognostic role was found regarding all-cause mortality or SCD in this patient population.

Increased QT Interval Dispersion is Associated with Coronary Artery Involvement in Children with Kawasaki Disease

Objectives

Coronary artery (CA) involvement is the most well known complication of Kawasaki disease (KD). Previous studies have suggested that QT dispersion has a predictive value in diagnosing cardiac ischemia, ventricular arrhythmia, and sudden cardiac death. However, limited data exits regarding the application of QT dispersion in KD. Therefore, we sought to determine whether there is a relationship between QT dispersion and CA involvement in patients with KD.

Methods

We performed a cross-sectional study of all consecutive patients with KD who were followed-up at the Pediatric Rheumatology Department (Pediatrics Center of Excellence affiliated to Tehran University of Medical Sciences, Tehran, Iran) from September 2013 to November 2015. Patients who met the criteria for KD, based on the American Heart Association guideline, were enrolled in the study. We collected data regarding patients' demographics, clinical manifestations, laboratory, and echocardiographic findings.

Results

A total of 70 KD patients were identified, including 43 males (61.4%) and 27 females (38.6%). The median age of patients was 21.0 (11.0-48.0) months. We found statistically significant differences between age, gender, and platelet count among patients with and without CA involvement (p < 0.050). Median corrected QT dispersion in patients with CA involvement calculated from 12 leads in the acute phase was significantly higher compared to the non-CA involvement group (108.0 (89.5-138.5) ms vs. 63.0 (54.0-74.5) ms, respectively (p < 0.001)).

Conclusions

Prolonged QT dispersion (corrected or non-corrected) during the acute and convalescence phases in patients with KD is associated with coronary involvement.

Abnormal Dispersion of Ventricular Repolarization as a Risk Factor in Patients with Human Immunodeficiency Virus: Tp-e Interval, Tp-e/QTc Ratio

OBJECTIVE

In recent years, there has been worldwide recognition of the problems associated with Human Immunodeficiency Virus (HIV) infection and Acquired Immune Deficiency Syndrome (AIDS). The prevalence of cardiovascular disease in the HIV-infected population is increasing. Repolarization abnormalities, the significant contributor to life-threatening arrhythmias and mortality, are the most frequent electrocardiographic changes in this population. This study aimed to evaluate the changes in Tp-e interval, Tp-e/QT and Tp-e/corrected QT (QTc) ratios, and traditional electrocardiographic features of electrical dispersion in adults infected with HIV.

SUBJECTS AND METHODS

A total of 235 participants were selected in the current study. The HIV group consisted of 85 subjects (median age 36 years [25-48], and the control group included 150 individuals (median age 39 years [27-51]). Tp-e interval, Tp-e/QT and Tp-e/QTc ratios were measured by the 12-lead electrocardiogram.

RESULTS

Tp-e interval, cTp-e interval, and Tp-e/QT and Tp-e/QTc ratios were significantly higher in HIV patients compared to the control group (p = 0.006, p = 0.004, p = 0.003, and p = 0.002, respectively). In correlation analysis, there was inverse correlation between the mean cTp-e interval and CD4 count and Tp-e/QTc ratios and CD4 count (r = - 0.407, p < 0.001, r = - 0.416, p < 0.001, respectively). Besides, there was correlation between the mean cTp-e interval and high-sensitivity C-reactive protein (hsCRP) and Tp-e/QTc ratios and hsCRP (r = 0.403, p = 0.001, r = 0.406, p = 0.001, respectively).

CONCLUSION

Our study revealed that the cTp-e interval, Tp-e/QT and cTp-e/QT ratios were prolonged and correlated to the severity of the disease in HIV-infected patients. Our findings may shed light on the cTp-e interval and Tp-e/QTc ratio and lead to further studies showing a relationship with ventricular arrhythmias and mortality in HIV-infected individuals.

Evaluation of the Tp-Te interval, Tp-Te/QTc ratio, and QT dispersion in patients with Turner syndrome

Objective:

To evaluate ventricular repolarization parameters using the interval from the peak to the end of the T wave (Tp–Te), together with QT and corrected QT (QTc) intervals, QT dispersion (QTd), and Tp-Te/QTc ratio in patients with Turner syndrome (pwTS) and to compare the results with those from healthy controls.

Methods:

In total, 38 patients previously diagnosed with Turner syndrome (TS) and 35 healthy girls (controls) were included in our cross-sectional study. Twelve-lead electrocardiography (ECG) and echocardiography after a 30-min rest were performed. The QT, QTc, QTd, Tp-Te interval, and Tp-Te/QTc ratio were determined.

Results:

No differences in age or sex were observed between the groups. QT intervals were similar in both groups [pwTS: 354.76±25.33 ms, controls (C): 353.29±17.51 ms, p=0.775]. pwTS had significantly longer QTc and QTd than controls (411.87±22.66 ms vs. 392.06±13.21 ms, p<0.001 and 40.31±2.02 ms vs. 37.54±1.83 ms, p<0.001, respectively). Similarly, the Tp-Te interval and Tp-Te/QTc ratio were significantly longer in pwTS than in controls (71.89±3.39 ms vs. 65.34±2.88 ms, p<0.001 and 0.17±0.01 vs. 0.16±0.01, p=0.01).

Conclusion:

As pwTS have longer QTc, QTd, Tp–Te interval, and Tp-Te/QTc ratio, an annual follow-up with ECG can provide awareness and even prevent sudden death in them. Also avoiding the use of drugs that makes repolarization anomaly and having knowledge about the side effects of these drugs are essential in pwTS.

Associations of serum and dialysate electrolytes with QT interval and prolongation in incident hemodialysis: the Predictors of Arrhythmic and Cardiovascular Risk in End-Stage Renal Disease (PACE) study

Background

Prolonged QT interval in hemodialysis patients may be associated with sudden cardiac death, however, few studies examined the longitudinal associations of modifiable factors such as serum and dialysate concentrations of calcium, potassium, and magnesium with corrected QT (QTc) prolongation in incident hemodialysis patients.

Methods

In 330 in-center hemodialysis participants from the PACE study who were followed up for one year, we examined the associations of predialysis serum electrolytes (total calcium [Ca], corrected Ca [cCa], ionized Ca [iCa], potassium [K], magnesium [Mg]), dialysate (dCa and dK), and serum-to-dialysate gradient measures with QTc interval and prolongation (≥460 ms in women and ≥ 450 ms in men).

Results

At the first study visit, 47% had QTc prolongation. Lower iCa and K were associated with longer QTc interval independent of potential confounders (QTc difference = 8.55[95% CI: 2.13, 14.97] ms for iCa; QTc difference = 9.89[1.58, 18.20] ms for K). Lower iCa was also associated with a higher risk of QTc prolongation. At 1 year of follow-up, 31% had persistent QTc prolongation. In longitudinal analyses, the associations of iCa and K with QTc interval remained significant, and lower K was associated with a higher risk of QTc prolongation while the association of iCa with QTc prolongation was borderline statistically significant. Serum Mg, dCa or dK, and respective gradients were not associated with QTc interval or prolongation.

Conclusion

Prolonged QTc is very common in incident hemodialysis participants and persists over follow-up. Ionized Ca and K are consistently inversely associated with QTc prolongation, which suggests closer monitoring for a low calcium or potassium level to mitigate risk.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1282-5) contains supplementary material, which is available to authorized users.

Effects of interval training on risk markers for arrhythmic death: a randomized controlled trial

Objective:

To compare the effects of high-intensity interval training versus moderate-intensity continuous training on risk markers of arrhythmic death in patients who recently suffered from an acute coronary syndrome.

Design:

Double-blind (patient and evaluator) randomized controlled trial.

Setting:

Cardiovascular Prevention and Rehabilitation Centre (EPIC Centre) of the Montreal Heart Institute, Montreal, Canada.

Subjects:

A total of 43 patients were randomized following an acute coronary syndrome.

Interventions:

Patients were assigned to either high-intensity interval training (n = 18) or isocaloric moderate-intensity continuous training (n = 19), three times a week for a total of 36 sessions.

Main measures:

Heart rate recovery for 5 minutes, heart rate variability for 24 hours, occurrence of ventricular arrhythmias, and QT dispersion were measured before and after the 36 sessions of training.

Results:

Among the 43 patients randomized, 6 participants in the high-intensity interval training group stopped training for reasons unrelated to exercise training and were excluded from the analyses. Heart rate recovery improved solely in the high-intensity interval training group, particularly at the end of recovery period ( p < 0.05). There were no differences in heart rate variability, occurrence of ventricular arrhythmias, or QT dispersion parameters between the groups at study end.

Conclusion:

Despite the lack of power to detect any large difference between the two interventions with respect to risk markers of arrhythmic death, high-intensity interval training appears safe and may be more effective at improving heart rate recovery relative to moderate-intensity continuous training in our patients following acute coronary syndrome.

Predictive value of P-wave and QT interval dispersion in children with congenital heart disease and pulmonary arterial hypertension for the occurrence of arrhythmias

OBJECTIVES

To evaluate P-wave dispersion (PWD) and QT dispersion (QTd) in children with congenital heart disease and pulmonary arterial hypertension (PAH-CHD) and to investigate the predictive value of both PWD and QTd for prediction of arrhythmias in such children.

MATERIALS AND METHODS

We included 40 children with PAH-CHD as Group I. Forty other children with CHD and no PAH were included as Group II. Forty healthy children of matched age and sex served as a Control group. Electrocardiography was performed to determine PWD and QTd. Furthermore, 24-hour Holter monitoring was performed to detect the presence of arrhythmias. Echocardiographic evaluation was also performed.

RESULTS

QTd and PWD were significantly higher in Group I than in Group II and Control group. A significant positive correlation was present between both QTd and PWD and mean pulmonary artery pressure, right ventricular diameter, pulmonary vascular resistance (PVR), and PVR to systemic vascular resistance ratio. QTd showed 93% sensitivity, 80% specificity, and 85% accuracy for prediction of occurrence of arrhythmias in patients with PAH-CHD at a cutoff point of 61 ms, whereas PWD showed 87% sensitivity, 80% specificity, and 85% accuracy for prediction of arrhythmias at a cutoff point of 32.5 ms in such patients. Logistic regression analysis showed that both QTd and PWD were good predictors for the occurrence of arrhythmias in children with PAH-CHD (p = 0.003 and p = 0.01, respectively).

CONCLUSIONS

PWD and QTd were good predictors for the occurrence of various arrhythmias in children with PAH-CHD.

Increased QT and P-wave dispersion during attack-free period in pediatric patients with migraine attacks

INTRODUCTION

Migraine is a common neurovascular disease characterised with recurrent attacks by pain-free periods. It has been suggested that both sympathetic and parasympathetic dysfunctions play a role in its pathophysiology.

AIM

The aim of our study was to investigate the ECG changes during attack-free period in children with migraine, in terms of QTc interval, QTc, and P-wave dispersion to evaluate the autonomic nervous system disturbance.

METHODS

Sixty children who were diagnosed with migraine were included as patient group and 50 healthy, age- and body mass index-matched children who were examined for innocent murmur were included as control group. The patients' routine ECG records were screened from the outpatient clinic files. The durations of P-wave, QT, and QTc intervals and dispersion values and heart rates (beats/minute) were compared between the patient and control groups.

RESULTS

P maximum and P dispersion were significantly higher, and P minimum was significantly lower in the migraine group compared with the control group. QT-QTc maximum and QT-QTc dispersion were significantly higher and QT-QTc minimum was significantly lower in the migraine group compared with the control group.

CONCLUSION

According to our findings, although migraine patients were asymptomatic and no arrhythmia was detected in the surface ECG, sympathovagal balance in the sympathetic system, which may be disrupted in favour of the sympathetic system, should continue even in the attack-free period, and we should be careful in terms of serious arrhythmias that may develop in these patients.

Pathophysiology, incidence, management, and consequences of cardiac arrhythmia in pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension

Arrhythmias are increasingly recognized as serious, end-stage complications of pre-capillary pulmonary hypertension, including pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). Although arrhythmias contribute to symptoms, morbidity, in-hospital mortality, and possibly sudden death in PAH/CTEPH, there remains a paucity of epidemiologic, pathophysiologic, and outcome data to guide management of these patients. This review summarizes the most current evidence on the topic: from the molecular mechanisms driving arrhythmia in the hypertrophied or failing right heart, to the clinical aspects of epidemiology, diagnosis, and management.

Does the Magnitude of the Electrocardiogram QT Interval Dispersion Predict Stroke Outcome?

BACKGROUND

QT dispersion, maximal interlead difference in QT interval on 12-lead electrocardiogram (ECG), measures cardiac repolarization abnormalities. Data are conflicting whether QT dispersion predicts adverse outcome in acute ischemic stroke (AIS) patients. Our objective is to determine if QT dispersion predicts: (1) short-term clinical outcome in AIS, and (2) stroke location (insular versus noninsular cortex).

METHODS

Admission ECGs from 412 consecutive patients with acute stroke symptoms from 2 university-based stroke centers were reviewed. QT dispersion was measured. A neuroradiologist reviewed brain imaging for insular cortex involvement. Favorable clinical outcomes at discharge were modified Rankin Scale (mRS) score of 0-1, discharge National Institutes of Health Stroke Scale (NIHSS) score less than 2, and discharge to home. Multiple logistic regressions were performed for each outcome measure and to determine the association between insular infarct and QT dispersion.

RESULTS

Of 145 subjects in the final analysis, median age was 65 years (interquartile range [IQR] 56-75), male patients were 38%, black patients were 68%, median QT dispersion was 78 milliseconds (IQR 59-98), and median admission NIHSS score was 4 (IQR 2-6). QT dispersion did not predict short-term clinical outcome for mRS score (odds ratio [OR] = 1.001, 95% confidence interval [CI] .99-1.01, P = .85), NIHSS at discharge (OR = .994, 95% CI .98-1.01, P = .30), or discharge disposition (OR = 1.001, 95% CI .99-1.01, P = .81). Insular cortex involvement did not correlate with QT dispersion magnitude (OR = 1.009, 95% CI .99-1.02, P = .45).

CONCLUSIONS

We could not demonstrate that QT dispersion is useful in predicting short-term clinical outcome at discharge in AIS. Further, the magnitude of QT dispersion did not predict insular cortical stroke location.

Obstructive sleep apnea is associated with increased QT corrected interval dispersion: the effects of continuous positive airway pressure

Introduction

Severe obstructive sleep apnea is associated with increased QT corrected interval dispersion and continuous positive airway pressure is thought to improve this arrhythmogenic marker.

Objective

The aim of the study was to determine the decrease of ratio of cardiovascular risk in patients with obstructive sleep apnea.

Methods

The study included 65 patients with severe obstructive sleep apnea who had an apnea-hypopnea index score of >30. Each patient underwent 12-channel electrocardiogram monitoring and polysomnography. Patients with an apnea-hypopnea index score of <5 were used as the control group. The control group also underwent electrocardiogram monitoring and polysomnography testing. The QT corrected interval dispersion levels of both groups were calculated. Three months after continuous positive airway pressure treatment, electrocardiogram recordings were obtained from the 65 patients with severe obstructive sleep apnea again, and their QT corrected interval dispersion values were calculated.

Results

There were 44 male and 21 female patients with severe obstructive sleep apnea syndrome. The age, gender, body mass index, initial saturation, minimum saturation, average saturation, and desaturation index were determined in both groups. The QT corrected intervals of the obstructive sleep apnea patients (62.48 ± 16.29 ms) were significantly higher (p = 0.001) than those of the control group (29.72 ± 6.30 ms). There were statistically significant differences between the QT corrected values before and after the continuous positive airway pressure treatment, with pretreatment QT corrected intervals of 62.48 ± 16.29 ms and 3-month post-treatment values of 41.42 ± 16.96 ms (p = 0.001). There was a positive and significant correlation between QT corrected interval dispersion periods and the apnea-hypopnea index and hypopnea index in obstructive sleep apnea patients (p = 0.001; r = 0.71; p = 0.001; r = 0.679, respectively).

Conclusion

Continuous positive airway pressure treatment reduced the QT corrected interval dispersion in patients with severe obstructive sleep apnea. In addition, shortening the QT corrected interval dispersion periods in patients with severe obstructive sleep apnea may reduce their risk of arrhythmias and cardiovascular disease.

Safety of Low-calcium Dialysate and its Effects on Coronary Artery Calcification in Patients Undergoing Maintenance Hemodialysis

To determine the safety of low-calcium-dialysate in patients undergoing maintenance hemodialysis (MHD) and its effects on coronary artery calcification (CAC) and analyze clinical risk factors for CAC. A total of 174 MHD patients were recruited and randomly divided into two groups: high-calcium dialysate (HCD, 1.5 mmol/L Ca²⁺) and low-calcium dialysate (LCD, 1.25 mmol/L Ca²⁺). Changes in CAC score (CACS) and cardiac function were evaluated using spiral computed tomography and echocardiography, respectively. Clinical and laboratory parameters were measured. Intra-dialysis adverse reactions were recorded and compared between the two groups. CACS was significantly lower in the LCD group than in the HCD group by the end of the study. Cardiac E/A_max was significantly higher in the LCD group than in the HCD group by the end of the study. There was no significant difference in the frequency of any intra-dialysis adverse reactions between the two groups during the study. LCD is helpful in maintaining cardiac diastolic function and postponing CAC progression. LCD does not increase intra-dialysis adverse reactions. Age may be the most important factor impacting CAC in MHD patients.

Improvement of increased cQTd is associated with heart function in patients with ischemic heart failure

Background

Chronic heart failure (CHF) is life-threatening without timely or effective intervention. In this study, we investigated the association between QT dispersion corrected for heart rate (cQTd) and heart function in patients with CHF.

Methods

From January 2013 to December 2015, we continuously enrolled 240 patients categorized as New York Heart Association functional class (NYHA) III-IV with a left ventricular ejection fraction (LVEF) < 40%. Based on the etiology, the patients were divided into a dilated cardiomyopathy (DCM) group (n = 120) and an ischemic cardiomyopathy (ICM) group (n = 120). Then, based on the cQTd width, the ICM group was divided into two subgroups: a QS group (cQTd ≤ 60 ms, n = 70) and a QL group (cQTd > 60 ms, n = 50). All patients were examined by echocardiography and 12-lead electrocardiography (ECG) at 1, 3, 6, and 12 months after enrollment.

Results

After one year of optimized medical treatment, patients in both groups showed significant improvement in LVEF and NYHA classification from baseline. However, the cQTd in the ICM group, especially the QL, was significantly shorter than that in the DCM group at each time point. In addition, the cQTd was negatively correlated with LVEF and 6-min walking test and positively correlated with NYHA class in the ICM group.

Conclusions

The present findings clearly demonstrate that cQTd is a meaningful parameter for assessing heart function in the follow-up of ICM patients.

Prediction of sudden death in elderly patients with heart failure

Most heart failure (HF) related mortality is due to sudden cardiac death (SCD) and worsening HF, particularly in the case of reduced ejection fraction. Predicting and preventing SCD is an important goal but most works include no or few patients with advanced age, and the prevention of SCD in elderly patients with HF is still controversial. A recent reduction in the annual rate of SCD has been recently described but it is not clear if this is also true in advanced age patients. Age is associated with SCD, although physicians frequently have the perception that elderly patients with HF die mainly of pump failure, underestimating the importance of SCD. Other clinical variables that have been associated to SCD are symptoms, New York Heart Association functional class, ischemic cause, and comorbidities (chronic obstructive pulmonary disease, renal dysfunction and diabetes). Some test results that should also be considered are left ventricular ejection fraction and diameters, natriuretic peptides, non-sustained ventricular tachycardias and autonomic abnormalities. The combination of all these markers is probably the best option to predict SCD. Different risk scores have been described and, although there are no specific ones for elderly populations, most include age as a risk predictor and some were developed in populations with mean age > 65 years. Finally, it is important to stress that these scores should be able to predict any type of SCD as, although most are due to tachyarrhythmias, bradyarrhythmias also play a role, particularly in the case of the elderly.

Altered Repolarization Reserve in Failing Rabbit Ventricular Myocytes: Calcium and β-Adrenergic Effects on Delayed- and Inward-Rectifier Potassium Currents

BACKGROUND

Electrophysiological remodeling and increased susceptibility for cardiac arrhythmias are hallmarks of heart failure (HF). Ventricular action potential duration (APD) is typically prolonged in HF, with reduced repolarization reserve. However, underlying K+ current changes are often measured in nonphysiological conditions (voltage clamp, low pacing rates, cytosolic Ca2+ buffers).

METHODS AND RESULTS

We measured the major K+ currents (IKr, IKs, and IK1) and their Ca2+- and β-adrenergic dependence in rabbit ventricular myocytes in chronic pressure/volume overload-induced HF (versus age-matched controls). APD was significantly prolonged only at lower pacing rates (0.2-1 Hz) in HF under physiological ionic conditions and temperature. However, when cytosolic Ca2+ was buffered, APD prolongation in HF was also significant at higher pacing rates. Beat-to-beat variability of APD was also significantly increased in HF. Both IKr and IKs were significantly upregulated in HF under action potential clamp, but only when cytosolic Ca2+ was not buffered. CaMKII (Ca2+/calmodulin-dependent protein kinase II) inhibition abolished IKs upregulation in HF, but it did not affect IKr. IKs response to β-adrenergic stimulation was also significantly diminished in HF. IK1 was also decreased in HF regardless of Ca2+ buffering, CaMKII inhibition, or β-adrenergic stimulation.

CONCLUSIONS

At baseline Ca2+-dependent upregulation of IKr and IKs in HF counterbalances the reduced IK1, maintaining repolarization reserve (especially at higher heart rates) in physiological conditions, unlike conditions of strong cytosolic Ca2+ buffering. However, under β-adrenergic stimulation, reduced IKs responsiveness severely limits integrated repolarizing K+ current and repolarization reserve in HF. This would increase arrhythmia propensity in HF, especially during adrenergic stress.

Evaluation of the Tp-Te Interval, QTc and P-Wave Dispersion in Patients With Coronary Artery Ectasia

Background

Coronary artery ectasia (CAE) is defined as a diffuse dilatation of the diameter of the ectatic segment of the coronary artery, 1.5 times greater than that of the adjacent segment. The Tp-Te interval, P-wave and QTc dispersions are relatively new electrocardiographic markers associated with an increased risk of developing arrhythmias. Despite CAE increasing in prevalence in recent years, there is a sparsity of data available about its arrhythmogenic effect. The aim of the study was to evaluate QTc, P-wave dispersion and Tp-Te and Tp-Te/QT ratio in patients with CAE.

Methods

A retrospective comparative study was designed for consecutive age- and sex-matched patients. Twenty patients with isolated CAE (group 1) and 20 control subjects (group 2), with normal coronary arteries, were included. All patients presented with chest pain and coronary angiogram was indicated. Outcome measures included Tp-Te interval, Tp-Te/QT ratio, QTc dispersion and P-wave dispersion. Measurement of electrocardiogram (ECG) parameters was conducted using standardized digital online software. Descriptive and inferential statistics were performed.

Results

Mean Tp-Te (95.5 ± 9.01 ms) and Tp-Te/QT ratio (0.22 ± 0.02) were significantly prolonged in CAE group (Tp-Te: 84 ± 5.62 ms, P = 0.00009; Tp-Te/QT ratio: 0.20 ± 0.01, P = 0.00004). In addition, QTc (31.2 ± 3.71 ms) and P-wave dispersion (31.9 ± 5.46 ms) were significantly increased in comparison to the control group (QTc: 27.6 ± 2.82 ms, P = 0.00532 and 20 ± 3.77 ms, P = 0.00003 respectively). However, there was no difference in ventricular activation time (VAT) between groups.

Conclusions

CAE ECGs were found to be associated with increased Tp-Te, Tp-Te/QT ratio, QTc intervals and P-wave dispersions. This may suggest that CAE existence has a pro-arrhythmogenic nature.

Cardiovascular consequences of myocardial bridging: A meta-analysis and meta-regression

Myocardial bridging, a congenital abnormality in which a coronary artery tunnels through the myocardial fibres was usually considered a benign condition. Many studies suggested a potential hemodynamic significance of myocardial bridging and some, usually case reports, implied a possible correlation between it and various cardiovascular pathologies like acute myocardial infarction, ventricular rupture, life-threatening arrhythmias, hypertrophic cardiomyopathy, apical ballooning syndrome or sudden death. The main objective of this article is to evaluate whether myocardial bridging may be associated with significant cardiac effects or if it is strictly a benign anatomical variation. To this purpose, we performed a meta-analysis (performed using the inverse variance heterogeneity model) and meta-regression, on scientific articles selected from three main databases (Scopus, Web of Science, Pubmed). The study included 21 articles. MB was associated with major adverse cardiac events - OR = 1.52 (1.01–2.30), and myocardial ischemia OR = 3.00 (1.02–8.82) but not with acute myocardial infarction, cardiovascular death, ischemia identified using imaging techniques, or positive exercise stress testing. Overall, myocardial bridging may have significant cardiovascular consequences (MACE, myocardial ischemia). More studies are needed to reveal/refute a clear association with MI, sudden death or other cardiovascular pathologies.

T-wave changes in patients with Wellens syndrome are associated with increased myocardial mechanical and electrical dispersion

Some patients with unstable angina and critical stenosis of the left anterior descending coronary artery (LAD) present with Wellens syndrome (WS), i.e., inverted or biphasic T-waves in the anterior precordial leads. We assessed clinical, angiographic, electro- and echocardiographic characteristic of patients with WS. In this retrospective study, clinical, angiographic, electro- and echocardiographic characteristic of 35 patients with WS were compared to 57 patients with critical LAD stenosis and normal resting electrocardiogram (ECG), and 45 subjects with normal coronary angiogram. QTc dispersion was measured from the 12-lead ECG as the difference between longest and shortest QTc intervals. Mechanical dispersion was defined as the time difference between the longest and shortest contraction durations which were measured as the time from the first deflection of the QRS complex to maximum myocardial shortening of each 18 segmental longitudinal strain curves derived by speckle tracking echocardiography. There were no significant differences in the complexity and location of the LAD lesion, anterograde and collateral flow in LAD and coronary artery dominance between patients with WS and normal ECG (P > 0.05, for all). Patients with WS had lower global longitudinal strain (GLS) and more pronounced both QTc and myocardial mechanical dispersion than patients with critical LAD stenosis and normal ECG, and control subjects (P < 0.05). T-wave changes in patients with WS are associated with more profound regional myocardial dysfunction and increased QTc and myocardial mechanical dispersion. Similar angiographic characteristics of the LAD lesion were seen in patients with WS and normal ECG.

Psychotropic drugs and ventricular repolarisation: The effects on QT interval, T-peak to T-end interval and QT dispersion

OBJECTIVE

We aimed to investigate in a clinical setting, the effects of different classes of psychotropic drugs on cardiac electrophysiological measures linked with an increased risk of sudden cardiac death.

METHODS

We conducted a cross-sectional study in a population of 1059 psychiatric inpatients studying the effects of various psychotropic drugs on the T-peak to T-end (TpTe) interval, QT dispersion and QT interval.

RESULTS

Methadone use showed a strong association with TpTe prolongation (odds ratio (OR)=12.66 (95% confidence interval (CI), 3.9-41.1), p<0.001), an effect independent from action on QT interval. Mood stabilisers showed significant effects on ventricular repolarisation: lithium was associated with a TpTe prolongation (OR=2.12 (95% CI, 1.12-4), p=0.02), while valproic acid with a TpTe reduction (OR=0.6 (95% CI, 0.37-0.98), p=0.04). Among antipsychotics, clozapine increased TpTe (OR=9.5 (95% CI, 2.24-40.39), p=0.002) and piperazine phenothiazines increased QT dispersion (OR=2.73 (95% CI, 1.06-7.02), p=0.037).

CONCLUSIONS

Treatment with psychotropic drugs influences TpTe and QT dispersion. These parameters might be considered to better estimate the sudden cardiac death risk related to specific medications. Beyond antipsychotics and antidepressants, mood stabilisers determine significant effects on ventricular repolarisation.

Novel therapeutic effects of sesamin on diabetes-induced cardiac dysfunction

Diabetes is a risk factor that increases the occurrence and severity of cardiovascular events. Cardiovascular complications are the leading cause of mortality of 75% of patients with diabetes >40 years old. Sesamin, the bioactive compound extracted from Sesamum indicum, is a natural compound that has diverse beneficial effects on hypoglycemia and reducing cholesterol. The aim of this study is to investigate sesamin effects to diabetes-inducing cardiac hypertrophy. In the present study bioinformatics analysis demonstrated cardiac hypertrophy signaling may be the most important pathway for upregulating genes in sesamin-treated groups. To verify the bioinformatics prediction, sesamin was used as the main bioactive compound to attenuate the impact of diabetes induced by streptozotocin (STZ) on cardiac function in a rat model. The results revealed that oral administration of sesamin for 4 weeks (100 and 200 mg/kg body weight) marginally improved blood glucose levels, body weight and significantly ameliorated the effects on heart rate and blood pressure in rats with type 1 diabetes relative to control rats. The QT interval of sesamin was also reduced relative to the control group. The findings indicated that sesamin has potential cardioprotective effects in the STZ-induced diabetes model. This suggested that this can be used as a novel treatment for patients with diabetes with cardiac dysfunction complication.

Understanding the impact of hypoglycemia on the cardiovascular system

INTRODUCTION

Hypoglycemia occurs commonly in insulin requiring individuals with either Type 1 or Type 2 Diabetes.

AREAS COVERED

This article will review recent information on the pro-inflammatory and pro-atherothrombotic effects of hypoglycemia. Additionally, effects of hypoglycemia on arrhythmogenic potential and arterial endothelial dysfunction will be discussed. Effects of hypoglycemia on cardiovascular morbidity and mortality from large clinical studies in Type 1 and Type 2 DM will also be reviewed.

EXPERT COMMENTARY

The relative and absolute risk of severe hypoglycemia leading to death and serious adverse events in both cardiovascular and other organ systems has been highlighted following the publication of recent large clinical trials focused on glucose control and outcomes. It would be helpful if future studies could develop broader end points to include minor and moderate hypoglycemia as well as more robust methods for capturing hypoglycemia contemporaneously with adverse events. In addition, perhaps consideration of including hypoglycemia as a primary outcome, may help identify the possible cause and effect of hypoglycemia on cardiovascular morbidity and mortality.

Baseline-Corrected QT (QTc) Interval Is Associated with Prolongation of QTc during Severe Hypoglycemia in Patients with Type 2 Diabetes Mellitus

BACKGROUND

We investigated an association between baseline heart rate-corrected QT (QTc) interval before severe hypoglycemia (SH) and prolongation of QTc interval during SH in patients with type 2 diabetes mellitus (T2DM).

METHODS

Between January 2004 and June 2014, 208 patients with T2DM, who visited the emergency department because of SH and underwent standard 12-lead electrocardiography within the 6-month period before SH were consecutively enrolled. The QTc interval was analyzed during the incidence of SH, and 6 months before and after SH. QTc intervals of 450 ms or longer in men and 460 ms or longer in women were considered abnormally prolonged.

RESULTS

The mean age and diabetes duration were 68.1±12.1 and 14.1±10.1 years, respectively. The mean QTc intervals at baseline and SH episodes were 433±33 and 460±33 ms, respectively (P<0.001). One hundred and fourteen patients (54.8%) had a prolonged QTc interval during SH. There was a significant decrease in the prolonged QTc interval within 6 months after SH (QTc interval prolongation during SH vs. after recovery, 54.8% vs. 33.8%, P<0.001). The prolonged QTc interval was significantly associated with baseline QTc interval prolongation (odds ratio, 2.92; 95% confidence interval, 1.22 to 6.96; P=0.016) after adjusting for multiple confounders.

CONCLUSION

A prolonged QTc interval at baseline was significantly associated with prolongation of the QTc interval during SH in patients with T2DM, suggesting the necessity of QTc interval monitoring and attention to those with a prolonged QTc interval to prevent SH.

Evaluation of inhomogeneities of repolarization in patients with psoriasis vulgaris

INTRODUCTION

The arrhythmia potential has not been investigated adequately in psoriatic patients. In this study, we assessed the ventricular repolarization dispersion, using the Tp-e interval and the Tp-e/QT ratio, and investigated the association with inflammation.

MATERIAL AND METHODS

Seventy-one psoriasis vulgaris patients and 70 age- and gender-matched healthy individuals were enrolled in the study. The severity of the disease was calculated using Psoriasis Area and Severity Index scoring. The QTd was defined as the difference between the maximum and minimum QT intervals. The Tp-e interval was defined as the interval from the peak of the T wave to the end of the T wave. The Tp-e interval was corrected for heart rate. The Tp-e/QT ratio was calculated using these measurements.

RESULTS

There were no significant differences between the groups with respect to basal clinical and laboratory characteristics (p > 0.05). The Tp-e interval, the corrected Tp-e interval (cTp-e) and the Tp-e/QT ratio were also significantly higher in psoriasis patients compared to the control group (78.5 ±8.0 ms vs. 71.4 ±7.6 ms, p < 0.001, 86.3 ±13.2 ms vs. 77.6 ±9.0 ms, p < 0.001 and 0.21 ±0.02 vs. 0.19 ±0.02, p < 0.001 respectively). A significant correlation was detected between the cTp-e time and the Tp-e/QT ratio and the PASI score in the group of psoriatic patients (r = 0.51, p < 0.001; r = 0.59, p < 0.001, respectively).

CONCLUSIONS

In our study, we detected a significant increase in the Tp-e interval and the Tp-e/QT ratio in patients with psoriasis vulgaris. The Tp-e interval and the Tp-e/QT ratio may be predictors for ventricular arrhythmias in patients with psoriasis vulgaris.

Diagnostic Value of Electrocardiogram in Predicting Exaggerated Blood Pressure Response to Exercise Stress Testing

INTRODUCTION

It is believed that an exaggerated blood pressure response (EBPR) to exercise stress test is associated with a higher risk of cardiovascular events. It is also assumed that QT dispersion (QT-d), which was originally proposed to measure the spatial dispersion of ventricular recovery times, may have a relationship to cardiovascular events. The objective of this study was to examine the difference of changes in QT-d, Maxi-QT, Mini-QT, and QT-c (corrected QT interval) of the electrocardiogram in two groups of patients with exaggerated blood pressure responses (EBPR group) and normal responses (control group) to exercise testing. Also, the diagnostic value of each of these criteria in the prediction of EBPR was studied.

METHODS

This cross-sectional study was conducted from May 2015 to February 2016 on patients suspected of coronary artery disease (CAD) undergoing exercise testing who had been referred to Ghaem and Imam Reza hospitals in Mashhad (Iran). All patients underwent a treadmill exercise test with the 12-lead ECG, which was optically scanned and digitized for analysis of QT-d, QT max, and QT min. Patients were divided into two groups of normal and EBPR to exercise testing. QT changes of ECG were compared between the two groups, and the diagnostic accuracy of QT variables for prediction of EBPR to exercise testing was studied. A multiple linear regression analysis (MLR), Pearson Chi-qquare, independent samples t-test, and receiver operating characteristic (ROC) curve were used as statistical methods in IBM SPSS version 19.

RESULTS

Sixty patients (55% male) with a mean age of 50.48 ± 10.89 years were studied in two groups of normal (n=30) and exaggerated blood pressure response (n=30) to exercise testing. Maximum QT and QT dispersion were statistically different in individuals' exaggerated blood pressure response to exercise stress test (p < 0.05). The logistic regression analysis revealed that none of our parameters predicted the EBPR. The ROC curve showed that 50 and 345 milliseconds for QT dispersion and Maxi-QT were the optimal cut-off points for the prediction of EBPR.

CONCLUSION

It seems that Maxi-QT and QT-d may be predictors of EBPR during exercise testing. Also, a significant difference in maxi-QT and QT-d was observed between two groups of patients with normal and EBPR during the exercise testing.

Prevalence and risk factors for prolonged QT interval and QT dispersion in patients with type 2 diabetes

AIMS

Prolonged QT interval is associated with cardiac arrhythmias and sudden death. The present study determined the prevalence of prolonged QT interval and QT dispersion and defined their clinical and metabolic predictors in patients with type 2 diabetes.

METHODS

Cross-sectional study included 501 patients with type 2 diabetes. A standard 12-lead electrocardiogram was recorded. QT corrected for heart rate (QTc) >440 ms and QT dispersion (QTd) >80 ms were considered abnormally prolonged. QTc ≥ 500 ms was considered a high-risk QTc prolongation. Demographic, clinical and laboratory data were collected. Independent risk factors for prolonged QTc and QTd were assessed using logistic regression analysis.

RESULTS

Prevalence of QTc > 440 ms and QTd > 80 ms were 44.1 and 3.6 %, respectively. Prevalence of high-risk QTc (≥500 ms) was 2 % only. Independent risk factors for QTc prolongation >440 ms were mean blood glucose (β = 2.192, p < 0.001), treatment with sulphonylurea (β = 5.198, p = 0.027), female gender (β = 8.844, p < 0.001), and coronary heart disease (β = 8.636, p = 0.001). Independent risk factors for QTc ≥ 500 ms were coronary heart disease (β = 4.134, p < 0.001) and mean blood glucose level (β = 1.735, p < 0.001). The independent risk factor for prolonged QTd was only coronary heart disease (β = 5.354, p < 0.001).

CONCLUSIONS

Although the prevalence of prolonged QTc > 440 ms is significant, the prevalence of high-risk QTc (≥500 ms) and QTd > 80 ms is very low in patients with type 2 diabetes. Hyperglycaemia and coronary heart disease are strong predictors of high-risk QTc.

Impacts of Glycoprotein IIb/IIIa Inhibition on QT Dispersion After Successful Percutaneous Coronary Intervention

Coronary ischemia augments inhomogeneity in ventricular repolarization. Decrease in the QT dispersion (QTd) following restoration of coronary blood flow to the ischemic myocardium by successful percutaneous coronary intervention (PCI) is an expected outcome. The purpose of the study was to seek whether glycoprotein IIb/IIIa (GP IIb/IIIa) inhibition has additional beneficial effects on QT dispersion after angiographically successful PCI. The study involved 111 consecutive patients scheduled for elective coronary balloon angioplasty with or without stent implantation. Sixty patients (mean age 58 ±9) were randomized to receive standard therapy including preprocedural aspirin, ticlopidine, and IV heparin, and 51 patients (mean age 54 ±10) were randomized to receive additional IV tirofiban infusion before the lesion was crossed with the guidewire. Standard 12-lead simultaneous ECG recordings for the measurement of QTd and corrected QTd (QTcd) (calculated by using Bazett’s formula) were obtained before and immediately after the procedure, and at the 6th, and 24th hours. Blood samples for detection of postprocedural myocardial damage (CK-MB and cTn-I) were taken before and immediately after the procedure, at the 6th, 12th, and 24th hours. In total, 128 stenoses were treated with PCI. Seventy of these lesions were in the standard therapy group and 58 in the tirofiban group. QTd and QTcd were not statistically different between the 2 groups before and immediately after the procedure and at the 6th hours, but at the 24th hour QTd and QTcd were significantly longer in the standard therapy group (p=0.047 and p=0.001, respectively). Postprocedural troponin-I elevation (B=0.692, p=0.037), maximum inflation pressure (B=0.182, p=0.001), and previous myocardial infarction (MI) (B=0.885, p=0.004) were defined as the predictors of the final QT dispersion at the 24th hour. QT dispersion significantly decreased after successful percutaneous coronary intervention. GP IIb/IIIa inhibition therapy was not superior by means of recovery of increased QT dispersion during the early hours of the intervention, but it prevented minor myocardial necrosis and provided more long-lasting recovery in QT dispersion as compared with heparin therapy. This impact of GP IIb/IIIa receptor inhibition on QTd may be a possible mechanism by which these drugs reduce cardiovascular events after PCI.

Effect of Direct Stent Implantation on QTc Dispersion

The aim of this study was to evaluate whether direct stenting is superior to conventional stent implantation technique with respect to QTc dispersion in prospectively selected patients with simple lesion morphology and class II stable angina undergoing elective coronary stenting. One hundred thirty-four consecutive patients were divided into 2 groups based on the stenting technique used: the direct stenting without predilation group, group I (n=64), and the stenting with predilation group, group II (n=70). All patients had single-vessel disease. The primary end point of the study was the QTc dispersion at the 24th hour and at the first month after the procedure and the secondary end point of the study was the major clinical events (MCEs) rate in the hospital period and up to 1 month. Baseline maximum QTc, minimum QTc, and QTc dispersion were not different between the 2 groups. QTc dispersion decreased from 47 ±8 msec before stent implantation to 41 ±11 msec at 24 hours and 37 ±7 msec 1 month after angioplasty in group I (p<0.006 and p<0.01, respectively), whereas QTc dispersion decreased from 49 ±9 msec before stent implantation to 46 ±8 msec at 24 hours and 42 ±10 msec 1 month after angioplasty in group II (p<0.03 and p<0.01, respectively). Compared with group II, the decrease in QTc dispersion was significantly greater at the 24th hour and at the first month after the procedure in group I (p<0.003 and p<0.001, respectively). There was a decreased trend toward MCE rate in group I in relation to that of group II, but the statistical difference was not significant. Direct stenting is a feasible and safe technique. It is superior to conventional stenting technique in decreasing the QTc dispersion at the 24th hour and at the first month after the procedure, whereas it is equivalent to single-vessel conventional stent implantation technique with respect to MCEs rate in the short-term period.