Correction of the QT interval for heart rate: review of different formulas and the use of Bazett's formula in myocardial infarction

Impact of Electrocardiographic Parameters on Sudden Death in Patients Receiving Maintenance Hemodialysis: Ten-Year Outcomes of the Q-Cohort Study

AIM

Sudden death is one of the most common causes of death among hemodialysis patients. Electrocardiography (ECG) is a noninvasive and inexpensive test that is regularly performed in hemodialysis clinics. However, the association between abnormal ECG findings and the risk of sudden death in hemodialysis patients is yet to be fully elucidated. Thus, the aim of this study was to determine the ECG parameters linked to sudden death in patients undergoing hemodialysis.

METHODS

The Q-Cohort Study is a multicenter, longitudinal, observational study of hemodialysis patients. In this study, 1,153 Japanese hemodialysis patients aged ≥ 18 years with ECG data recorded within 1 year of study enrollment were followed up for 10 years. Cox proportional hazards models were used to estimate the multivariate-adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) for the association between ECG parameters and sudden death.

RESULTS

During the median follow-up period of 9.0 years, 517 patients died, 76 of whom exhibited sudden death. After adjusting for confounding factors, higher heart rate, QT prolongation, and left ventricular hypertrophy as per the Sokolow-Lyon voltage criteria were found to be independently associated with an increased risk of sudden death. The adjusted HRs [95% CIs] for each abnormal ECG parameter were 2.02 [1.05-3.89], 2.10 [1.30-1.77], and 1.91 [1.18-3.09], respectively.

CONCLUSIONS

Higher heart rate, QT prolongation, and left ventricular hypertrophy on ECG have been determined to be associated with an increased risk of sudden death. Therefore, regular ECG recording could enable medical practitioners to identify hemodialysis patients who require intervention to prevent lethal arrhythmia.

Consecutive treatments of methamphetamine promote the development of cardiac pathological symptoms in zebrafish

Chronic methamphetamine use, a widespread drug epidemic, has been associated with cardiac morphological and electrical remodeling, leading to the development of numerous cardiovascular diseases. While methamphetamine has been documented to induce arrhythmia, most results originate from clinical trials from users who experienced different durations of methamphetamine abuse, providing no documentation on the use of methamphetamine in standardized settings. Additionally, the underlying molecular mechanism on how methamphetamine affects the cardiovascular system remains elusive. A relationship was sought between cardiotoxicity and arrhythmia with associated methamphetamine abuse in zebrafish to identify and to understand the adverse cardiac symptoms associated with methamphetamine. Zebrafish were first treated with methamphetamine 3 times a week over a 2-week duration. Immediately after treatment, zebrafish underwent electrocardiogram (ECG) measurement using an in-house developed acquisition system for electrophysiological analysis. Subsequent analyses of cAMP expression and Ca2+ regulation in zebrafish cardiomyocytes were conducted. cAMP is vital to development of myocardial fibrosis and arrhythmia, prominent symptoms in the development of cardiovascular diseases. Ca2+ dysregulation is also a factor in inducing arrhythmias. During the first week of treatment, zebrafish that were administered with methamphetamine displayed a decrease in heart rate, which persisted throughout the second week and remained significantly lower than the heart rate of untreated fish. Results also indicate an increased heart rate variability during the early stage of treatment followed by a decrease in the late stage for methamphetamine-treated fish over the duration of the experiment, suggesting a biphasic response to methamphetamine exposure. Methamphetamine-treated fish also exhibited reduced QTc intervals throughout the experiment. Results from the cAMP and Ca2+ assays demonstrate that cAMP was upregulated and Ca2+ was dysregulated in response to methamphetamine treatment. Collagenic assays indicated significant fibrotic response to methamphetamine treatment. These results provide potential insight into the role of methamphetamine in the development of fibrosis and arrhythmia due to downstream effectors of cAMP.

Evaluating the effect of Roxadustat on ventricular repolarization in patients undergoing peritoneal dialysis

BACKGROUND

Roxadustat is a novel oral medication used to treat anemia in CKD patients. Several studies have shown that Roxadustat can alleviate anemia in CKD patients by increasing hemoglobin levels and regulating iron metabolism. We aimed to evaluate the effect of Roxadustat on ventricular repolarization in PD patients. This study may provide a new integrated approach to the assessment and treatment of CKD.

METHODS

The present prospective cohort study enrolled 65 CKD patients who were treated with Roxadustat and 31 CKD patients who received conventional therapy between January 2021 and June 2022. All patients were examined for ECG in the absence of clinical symptoms and compared the ECG indicators. Demographic and clinical data of all patients were collected. All data used SPSS 18.0 for statistical analyses.

RESULTS

The T peak-to-end (Tpe) of PD patients in the Roxadustat group was remarkably slower than that of patients in the conventional group. Additionally, the Tpe/QT ratio in the conventional group was significantly elevated than that in the Roxadustat group. The results of logistic regression analysis showed that Tpe (95%CI 1.191 ~ 2.141, P = 0.002) and Roxadustat treatment (95%CI 1.357 ~ 42.121, P = 0.021) were the risk factors of PD patients with high Tp-e/QT ratio.

CONCLUSION

In summary, we found that Roxadustat could improve ventricular repolarization in peritoneal dialysis patients, which indicated a potential cardiovascular protective effect of Roxadustat. This study might provide a new integrated approach to the assessment and treatment of CKD.

Left ventricular morphologic progression in apical hypertrophic cardiomyopathy

BACKGROUND

Left ventricular (LV) morphologic progression in apical hypertrophic cardiomyopathy (AHC) has not been well studied. We evaluated serial echocardiographic changes in LV morphology.

METHODS

Serial echocardiograms in AHC patients were assessed. LV morphology was categorized according to the presence of an apical pouch or aneurysm, and LV hypertrophic severity and extent; relative, pure, and apical-mid type defined as mild (<15 mm thickness) apical hypertrophy, significant (≥15 mm) apical hypertrophy, and both apical and midventricular hypertrophy, respectively. Adverse clinical events and late gadolinium enhancement (LGE) extent on cardiac magnetic resonance were evaluated for each morphologic type.

RESULTS

In 41 patients, 165 echocardiograms (maximal interval: 4.2 [IQR, 2.3-11.8] years) were evaluated. Morphologic changes were observed in 19 (46%) patients. Eleven (27%) patients displayed the progression of LV hypertrophy toward pure or apical-mid type. Five (12%) and 6 (15%) patients developed new pouches and aneurysms. Patients with progression tended to be younger (50 ± 15.6 vs 59 ± 14.4 years, P = 0.058) and had a longer period of follow-up (12 [5-14] vs 3 [2-4] years, P < 0.001). During a follow-up of 7.6 (IQR 3.0-12.1) years, 21 (51%) experienced clinical events. The relative, pure, and apical-mid types showed different LGE extents (2%, 6%, and 19%, P = 0.004). Patients with severe hypertrophic and apical involvement showed higher clinical event rates.

CONCLUSIONS

About half of AHC patients had a progression of LV morphology to more hypertrophic involvement and/or an apical pouch or aneurysm formation. Advanced AHC morphologic types were associated with higher event rates and scar burdens.

Effect of reperfusion strategy on QT dispersion in patients with acute myocardial infarction: Impact on in-hospital arrhythmia

BACKGROUND

Myocardial ischemia and ST-elevation myocardial infarction (STEMI) increase QT dispersion (QTD) and corrected QT dispersion (QTcD), and are also associated with ventricular arrhythmia.

AIM

To evaluate the effects of reperfusion strategy [primary percutaneous coronary intervention (PPCI) or fibrinolytic therapy] on QTD and QTcD in STEMI patients and assess the impact of the chosen strategy on the occurrence of in-hospital arrhythmia.

METHODS

This prospective, observational, multicenter study included 240 patients admitted with STEMI who were treated with either PPCI (group I) or fibrinolytic therapy (group II). QTD and QTcD were measured on admission and 24 hr after reperfusion, and patients were observed to detect in-hospital arrhythmia.

RESULTS

There were significant reductions in QTD and QTcD from admission to 24 hr in both group I and group II patients. QTD and QTcD were found to be shorter in group I patients at 24 hr than those in group II (53 ± 19 msec vs 60 ± 18 msec, P = 0.005 and 60 ± 21 msec vs 69+22 msec, P = 0.003, respectively). The occurrence of in-hospital arrhythmia was significantly more frequent in group II than in group I (25 patients, 20.8% vs 8 patients, 6.7%, P = 0.001). Furthermore, QTD and QTcD were higher in patients with in-hospital arrhythmia than those without (P = 0.001 and P = 0.02, respectively).

CONCLUSION

In STEMI patients, PPCI and fibrinolytic therapy effectively reduced QTD and QTcD, with a higher observed reduction using PPCI. PPCI was associated with a lower incidence of in-hospital arrhythmia than fibrinolytic therapy. In addition, QTD and QTcD were shorter in patients not experiencing in-hospital arrhythmia than those with arrhythmia.

Comparison of different QT correction methods for nonclinical safety assessment in ketamine-anesthetized Indian rhesus monkeys (Macaca mulatta)

Rhesus monkeys are a non-rodent species employed in the preclinical safety evaluation of pharmaceuticals and biologics. These nonhuman primate species have been increasingly used in biomedical research because of the similarity in their ionic mechanisms of repolarization with humans. Heart rate and QT interval are two primary endpoints in determining the pro-arrhythmic risk of drugs. As heart rate and QT interval have an inverse relationship, any change in heart rate causes a subsequent change in QT interval. This warrants for calculation of a corrected QT interval. This study aimed to identify an appropriate formula that best corrected QT for change in heart rate. We employed seven formulas based on source-species type, clinical relevance, and requirements of various international regulatory guidelines. Data showed that corrected QT interval values varied drastically for different correction formulas. Equations were compared on their slope values based on QTc versus RR plots. The rank order of the slope for different formulas was (closest to farthest from zero) QTcNAK, QTcHAS, QTcBZT, QTcFRD, QTcVDW, QTcHDG, and QTcFRM. QTcNAK emerged to be the best correcting formula in this study. It showed the least correlation with the RR interval (r = -0.01) and displayed no significant difference amongst the sexes. As there is no universally recognized formula for preclinical use, the authors recommend developing a best-case scenario model for specific study designs and individual organizations. The data from this research will be helpful in deciding an appropriate QT correction formula for the safety assessment of new pharmaceuticals and biologics.

Metformin and Dapagliflozin Attenuate Doxorubicin-Induced Acute Cardiotoxicity in Wistar Rats: An Electrocardiographic, Biochemical, and Histopathological Approach

Doxorubicin is a widely used anticancer drug whose efficacy is limited due to its cardiotoxicity. There is no ideal cardioprotection available against doxorubicin-induced cardiotoxicity. This study aimed to investigate the anticipated cardioprotective potential of metformin and dapagliflozin against doxorubicin-induced acute cardiotoxicity in Wistar rats. At the beginning of the experiment, cardiac screening of experimental animals was done by recording an electrocardiogram (ECG) before allocating them into the groups. Thereafter, a total of thirty healthy adult Wistar rats (150-200 g) were randomly divided into five groups (n = 6) and treated for eight days as follows: group I (normal control), group II (doxorubicin control), group III (metformin 250 mg/kg/day), group IV (metformin 180 mg/kg/day), and group V (dapagliflozin 0.9 mg/kg/day). On the 7th day of the treatment phase, doxorubicin 20 mg/kg was administered intraperitoneal to groups II, III, IV, and V. On the 9th day (immediately after 48 h of doxorubicin administration), blood was collected from anesthetized animals for glucose, lipid profile, CK-MB & AST estimation, and ECG was recorded. Later, animals were sacrificed, and the heart was dissected for histopathological examination. We found that compared to normal control rats, CK-MB, AST, and glucose were significantly increased in doxorubicin control rats. There was a significant reversal of doxorubicin-induced hyperglycemia in the rats treated with metformin 250 mg/kg compared to doxorubicin control rats. Both metformin (180 mg/kg and 250 mg/kg) and dapagliflozin (0.9 mg/kg) significantly altered doxorubicin-induced ECG changes and reduced the levels of cardiac injury biomarkers CK-MB and AST compared to doxorubicin control rats. Metformin and dapagliflozin protected the cellular architecture of the myocardium from doxorubicin-induced myocardial injury. Current study revealed that both metformin and dapagliflozin at the FDA-recommended antidiabetic doses mitigated doxorubicin-induced acute cardiotoxicity in Wistar rats. The obtained data have opened the perspective to perform chronic studies and then to clinical studies to precisely consider metformin and dapagliflozin as potential chemoprotection in the combination of chemotherapy with doxorubicin to limit its cardiotoxicity, especially in patients with comorbid conditions like type II diabetes mellitus.

QT prolongation is over-estimated by Bazett compared to Friderica in Japanese child and adolescent inpatients

Recent researches suggested that the risk of drug-induced QTc prolongation is low in child and adolescent psychiatry setting. However, these cohorts enrolled mainly of Caucasian background. We aimed to assess the prevalence of QTc prolongation and its association with antipsychotic use in Japanese youth. The medical records of inpatients were reviewed. Two different definitions of QT prolongation, Bazett's corrected QT interval (QTcB) >450 msec and Fridericia's corrected QT interval (QTcF) >450 msec, were adopted. In 220 participants [age: 13.4 ± 2.3 years, antipsychotics according to the chlorpromazine equivalence: 50 (25th-75th percentiles; 0-150) mg/day], the prevalence of QTcB and QTcF prolongation was 13.6 and 2.3%, respectively. Patients with QTcB >450 msec had a significantly higher heart rate than those with QTcB ≤450 msec (91.2 ± 20.6 bpm vs. 76.1 ± 15.2 bpm; P < 0.001). The other variables, except potassium level (4.1 ± 0.4 mEq/L vs. 4.2 ± 0.3 mEq/L; P = 0.030), showed no significant difference. Clinically meaningful QTc prolongation was rare even in this Japanese cohort. This study also suggested that if QTcB is used, clinicians should be aware of possible overdiagnosis of QTc prolongation due to accelerated heart rate.

The negative effects of obesity on heart, especially the electrophysiology of the heart

Obesity is associated with ventricular arrhythmia and sudden cardiac death. Numerous studies have shown that obesity may have effects on the heart by affecting the ventricular re-polarisation (VR). As an effective detection method for VR the measurement of the QT interval has been extensively studied in obese patients (OP). This review aims to investigate the relationship between obesity and obesity-related diseases; including diabetes, hypertension and cardiovascular diseases (CVD). This review compares the advantages and disadvantages of different QT interval measurement methods, as well as explores the possible mechanisms of obesity leading to heart disease. Finally, it also reviews the feasibility of various weight loss methods to reverse the risk of obesity leading to heart disease is discussed.

Postural changes in blood pressure among patients with diabetes attending a referral hospital in southwestern Uganda: a cross-sectional study

BACKGROUND

Orthostatic hypotension (OH) and orthostatic hypertension (OHT) are often unrecognized in clinical care for diabetic individuals, yet they are associated with increased risk for adverse cardiovascular outcomes. We aimed to determine the prevalence of the abnormal orthostatic blood pressure (BP) responses, and associated factors among diabetic individuals in ambulatory care for diabetes in southwestern Uganda.

METHODS

We conducted a cross-sectional study among diabetic individuals aged 18-65 years at Mbarara Regional Referral Hospital, southwestern Uganda from November 2018 to April 2019. We obtained demographic and clinical data including a detailed medical history, and glycemic profile. BP measurements were taken in supine position and within 3 min of standing. We defined OH in participants with either ≥ 20 mmHg drop in systolic BP (SBP) or ≥ 10 mmHg drop in diastolic BP (DBP) after assuming an upright position. OHT was defined in participants with either a ≥ 20 mmHg rise in SBP, or ≥ 10 mmHg rise in DBP after assuming an upright position. Multivariate logistic regression was used to identify factors associated with OH and OHT.

RESULTS

We enrolled 299 participants, with a mean age of 50 years (SD ± 9.8), and mean HbA1c of 9.7% (SD ± 2.6); 70% were female. Of the 299 participants, 52 (17.4%; 95% CI 13.3-22.2%) met the definition of OH and 43 (14.4%; 95% CI 10.6-18.9%) were classified as having OHT. In multivariable models, factors associated with diabetic OH were older age (OR = 2.40 for 51-65 years vs 18-50 years, 95% CI 1.02-5.67, P = 0.046), diabetic retinopathy (OR = 2.51; 95% CI 1.14-5.53, P = 0.022), higher resting SBP ≥ 140 mmHg (OR = 3.14; 95% CI 1.31-8.7.56, P = 0.011), and history of palpitations (OR = 2.31; 95% CI 1.08-4.92, P = 0.031). Self-report of palpitations (OR = 3.14; 95% CI 1.42-6.95, P = 0.005), and higher resting SBP ≥ 140 mmHg (OR = 22.01; 95% CI 1.10-4.42, P = 0.043) were associated with OHT.

CONCLUSION

OH and OHT are common among diabetic individuals in ambulatory diabetes care in southwestern Uganda. Orthostatic BP measurements should be considered as part of routine physical examination to improve detection of OH and OHT, especially among older diabetics with complications of the disease. Future studies to assess the health and prognostic implications of OH and OHT among diabetics in the region are warranted.

Methyl Gallate Attenuates Doxorubicin-Induced Cardiotoxicity in Rats by Suppressing Oxidative Stress

Doxorubicin-induced cardiotoxicity is the leading cause of morbidity and mortality among cancer survivors. The present study was aimed to investigate the cardioprotective potential of methyl gallate; an active polyphenolic nutraceutical, against doxorubicin-induced cardiotoxicity in Wistar rats. Twenty-four female Wistar rats (150-200 g) were divided into four groups (n = 6) which consist of normal control (group I), doxorubicin control (group II), test-A (group III), and test-B (group IV). Group III and group IV animals were prophylactically treated with methyl gallate 150 mg/kg/day and 300 mg/kg/day orally, respectively, for seven days. Doxorubicin (25 mg/kg; single dose) was administered through an intraperitoneal route to group II, III, and IV animals on the seventh day to induce acute cardiotoxicity. On the 8^th day, besides ECG analysis, serum CK, CK-MB, LDH, AST, MDA, and GSH were assayed. Following gross examination of isolated hearts, histopathological evaluation was performed by light microscopy. A significant (p < 0.05) cardiac injury, as well as oxidative stress, was observed in doxorubicin control rats in comparison to normal control rats. Methyl gallate at both the doses significantly (p < 0.05) reduced doxorubicin-induced ECG changes, dyslipidaemia, and elevation of CK, CK-MB, LDH, AST, MDA and increased GSH level. Methyl gallate reversed the doxorubicin-induced histopathological changes in the heart. The present study revealed that methyl gallate exerts cardioprotection against doxorubicin-induced cardiotoxicity in female Wistar rats by suppressing oxidative stress. Our study opens the perspective to clinical studies for consideration of methyl gallate as a potential chemoprotectant nutraceutical in the combination chemotherapy with doxorubicin to limit its cardiotoxicity.

Evaluation of inflammatory and cardiac-electrophysiological markers in patients undergoing peritoneal dialysis

Background: The Tp-e/QT (peak to end of T-wave duration/QT interval) ratio is a promising marker of myocardial repolarization and ventricular arrhythmogenesis. Its elevation is associated with sudden cardiac death in different clinical conditions. This study was designed to assess the possible association between increased Tp-e/QT ratio and clinical factors in peritoneal dialysis patients. Materials & methods: We devised a prospective cross-sectional study, which included 107 patients who were divided into groups according to their Tp-e/QT ratio. The association of an increased Tp-e/QT ratio with related factors was analyzed with multivariate logistic regression. Results: Thirty-one patients, who had an elevated Tp-e/QT ratio, showed higher values of IL-6, left ventricular end-systolic diameter, Tp-e, percentage of diabetes mellitus, coronary artery calcification, and left ventricular ejection fraction. Multivariate analysis revealed that IL-6 was an independent risk factor for a higher Tp-e/QT ratio after adjustments. Conclusion: Our study revealed that a high serum IL-6 level in peritoneal dialysis patients increased the risk of a higher Tp-e/QT ratio, which indicated a potentially hazardous interplay between inflammation and arrhythmogenesis.

Safety, tolerability, and clinical outcomes of hydroxychloroquine for hospitalized patients with coronavirus 2019 disease

BACKGROUND

Severe acute respiratory coronavirus 2 (SARS-CoV-2) has caused a devastating worldwide pandemic. Hydroxychloroquine (HCQ) has in vitro activity against SARS-CoV-2, but clinical data supporting HCQ for coronavirus disease 2019 (COVID-19) are limited.

METHODS

This was a retrospective cohort study of hospitalized patients with COVID-19 who received ≥1 dose of HCQ at two New York City hospitals. We measured incident Grade 3 or 4 blood count and liver test abnormalities, ventricular arrhythmias, and vomiting and diarrhea within 10 days after HCQ initiation, and the proportion of patients who completed HCQ therapy. We also describe changes in Sequential Organ Failure Assessment hypoxia scores between baseline and day 10 after HCQ initiation and in-hospital mortality.

RESULTS

None of the 153 hospitalized patients with COVID-19 who received HCQ developed a sustained ventricular tachyarrhythmia. Incident blood count and liver test abnormalities occurred in <15% of patients and incident vomiting or diarrhea was rare. Eighty-nine percent of patients completed their HCQ course and three patients discontinued therapy because of QT prolongation. Fifty-two percent of patients had improved hypoxia scores 10 days after starting HCQ. Thirty-one percent of patients who were receiving mechanical ventilation at the time of HCQ initiation died during their hospitalization, compared to 18% of patients who were receiving supplemental oxygen but not requiring mechanical ventilation, and 8% of patients who were not requiring supplemental oxygen. Co-administration of azithromycin was not associated with improved outcomes.

CONCLUSIONS

HCQ appears to be reasonably safe and tolerable in most hospitalized patients with COVID-19. However, nearly one-half of patients did not improve with this treatment, highlighting the need to evaluate HCQ and alternate therapies in randomized trials.

Prevalence and Correlates of Cardiovascular Autonomic Neuropathy Among Patients with Diabetes in Uganda: A Hospital-Based Cross-sectional Study

Background:

Cardiovascular autonomic neuropathy (CAN) is a common complication in individuals with diabetes mellitus (DM) but often overlooked in clinical practice. The burden and correlates of CAN have not been extensively studied in low-income countries, particularly in sub-Saharan Africa.

Objectives:

To determine the prevalence and correlates of CAN among adults in ambulatory diabetes care in southwestern Uganda.

Method:

We conducted a cross-sectional study among adults with diabetes from November 2018 to April 2019. CAN was assessed using the five autonomic function tests: deep breathing, Valsalva maneuver, postural index on standing, change in blood pressure during standing and diastolic blood pressure response to isometric exercise. We estimated the prevalence of CAN and fit regression models to identify its demographic and clinical correlates.

Results:

We enrolled 299 individuals. The mean age was 50.1 years (SD ± 9.8), mean HbA1c was 9.7 (SD ± 2.6) and 69.6% were female. CAN was detected in 156/299 (52.2%) of the participants on the basis of one or more abnormal cardiovascular autonomic reflex tests. Out of 299 participants, 88 (29.4%) were classified as early CAN while 61/299 (20.4%) and 7/299 (2.3%) were classified as definite and severe (advanced) CAN respectively. In multivariable regression models, age over 50 years (aOR 3.48, 95%CI 1.35 –8.99, p = 0.010), duration of diabetes over 10 years (aOR 4.09, 95%CI 1.78 –9.38, p = 0.001), and presence of diabetic retinopathy (aOR 2.25, 95%CI 1.16 –4.34, p = 0.016) were correlated with CAN.

Conclusions:

Our findings reveal a high prevalence of CAN among individuals in routine outpatient care for diabetes mellitus in Uganda. Older age, longer duration of diabetes and coexistence of retinopathy are associated with CAN. Future work should explore the clinical significance and long term outcomes associated with CAN in this region.

Pharmacokinetics and Ex Vivo Antimalarial Activity of Artesunate-Amodiaquine plus Methylene Blue in Healthy Volunteers

High rates of artemisinin-based combination therapy (ACT) failures in the treatment of Plasmodium falciparum malaria in Southeast Asia have led to triple-drug strategies to extend the useful life of ACTs. In this study, we determined whether methylene blue [MB; 3,7-bis(dimethylamino)phenothiazin-5-ium chloride hydrate] alters the pharmacokinetics of artesunate-amodiaquine (ASAQ) and enhances the ex vivo antimalarial activity of ASAQ. In an open-label, randomized crossover design, a single oral dose of ASAQ (200 mg AS/540 mg AQ) alone or with MB (325 mg) was administered to 15 healthy Vietnamese volunteers. Serial blood samples were collected up to 28 days after dosing. Pharmacokinetic properties of the drugs were determined by noncompartmental analysis. After drug administration, plasma samples from seven participants were assessed for ex vivo antimalarial activity against the artemisinin-sensitive MRA1239 and the artemisinin-resistant MRA1240 P. falciparum lines, in vitro MB significantly increased the mean area under the curve of the active metabolite of AS, dihydroartemisinin (1,246 ± 473 versus 917 ± 405 ng·h/ml, P = 0.009) but did not alter the pharmacokinetics of AQ, AS, or desethylamodiaquine. Comparing the antimalarial activities of the plasma samples from the participants collected up to 48 h after ASAQ plus MB (ASAQ+MB) and ASAQ dosing against the MRA1239 and MRA1240 lines, MB significantly enhanced the blood schizontocidal activity of ASAQ by 2.0-fold and 1.9-fold, respectively. The ring-stage survival assay also confirmed that MB enhanced the ex vivo antimalarial activity of ASAQ against MRA1240 by 2.9-fold to 3.8-fold, suggesting that the triple-drug combination has the potential to treat artemisinin-resistant malaria and for malaria elimination. (This study has been registered in the Australian New Zealand Clinical Trials Registry [https://anzctr.org.au/] under registration number ACTRN12612001298808.).

Automated QT Interval Measurement Using Modified Pan-Tompkins Algorithm with Independent Isoelectric Line Approach

The QT interval on the electrocardiogram (ECG) signal is known to have an important role in monitoring heart’s electrical activity because the presence of QT interval prolongation can be associated with life-threatening cardiac events. This interval can be identified and measured using either manual or automated techniques. Currently, studies on automated QT interval measurement algorithms are becoming a growing field, as they can provide the best solution to overcome misdiagnosis and timely issues resulting from manual identification. However, the physiological variability of the QRS complex and the fluctuation of the isoelectric line are prevalent issues that need to be considered in the automatic method. In this report, an algorithm to identify the QRS onset and T-wave offset for measuring the corrected QT interval (QTc) is proposed. This method uses an improved Pan-Tompkins algorithm from the previous work with independent of the isoelectric line approach for detecting the QRS onset and the T offset. The algorithm was implemented in Matlab and applied to the 60 seconds duration of 27 records in the PPUKM database with a sampling frequency of 500 Hz. The performance of the algorithm achieved a sensitivity of 100% for QRS onset detection and 100% for T offset detection. As for the accuracy, the algorithm’s performance obtained 100% for QRS onset detection and 99.56% for T offset detection. The mean error results with respect to manual annotation were 37±18.5 ms for QRS onset detection and 32±22.3 ms for T offset detection which was within ANSI/AAMI-EC57:1998 standard tolerance. The proposed algorithm exhibits reliable automated QTc measurement. Besides insensitive to morphological variations of ECG waves, the computational method is simple and possibly implemented as the basis for future software development for portable device applications.

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.

The Pattern of Tpeak-Tend Interval and QTdis, and Pdis in Children with Brucellosis

OBJECTIVE

To investigate the effect of inflammation on the conducting system of the heart in patients diagnosed with brucellosis.

METHODS

A total of 42 patients diagnosed with brucellosis and 39 age and sex-matched healthy children were enrolled into the study. Pre- and post-treatment electrocardiographic parameters in brucellosis and control group were recorded from an electrocardiogram for each patient.

RESULTS

The results indicated that the parameters including Pmax, Pdis, QTmax, QTdis, QTcdis, Tp-edis interval and Tp-emax/QTmax and Tp-emax/QTcmax ratios, which are known to be key indicators for the prediction of severe atrial or ventricular arrhythmia and sudden cardiac death and also important parameters used as the indicators for the non-invasive evaluation of the transmural heterogeneity were significantly longer in the study group compared with the control group (p < 0.05).

CONCLUSION

In this study, it was determined that the brucella disease had more cardiac involvement than thought, and this was more in the subclinical form of cardiac involvement.

Can QT interval prolongation or dispersion detected in a positive exercise ECG test predict critical coronary artery disease?

Introduction

Exercise electrocardiography (EET) is frequently used in coronary artery disease, but the specificity of this test is very low. In the literature, parameters such as QT prolongation and QT dispersion which show coronary artery disease and arrhythmia were not sufficiently investigated using EET. The aim of this study was to investigate whether QT interval prolongation or dispersion (QT disp) in a positive EET test could predict critical coronary artery disease (CAD).

Material and methods

Patients with a positive exercise test were included in the study. Data regarding QT, QTc (corrected QT interval) and QT disp values before, during and after EET were noted. Critical coronary artery occlusions (≥ 70%) was recorded from coronary angiographic images. Patients were divided into two groups (critical CAD and non-critical CAD).

Results

A total of 192 patients were found to be eligible for the study. There were 126 patients in the non-critical CAD group (group 1) and 66 patients in the critical CAD group (group 2). Recovery QTc, peak QT disp, and recovery QT disp were significantly increased in group 2 (p < 0.001 for each). Also, target heart rate (p = 0.012), basal systolic blood pressure (p = 0.005) and diastolic blood pressure (p < 0.001) were significantly higher in group 1. Recovery QTc (OR = 1.051) and recovery QT disp (OR = 1.117) were determined as the independent predictors for critical CAD. The ROC analysis results indicated that critical CAD could be diagnosed with 90% sensitivity when the recovery QTc cut-off value was set as 404 ms.

Conclusions

In patients with positive EET, prolonged QTc and QT disp values measured during the recovery period would predict critical CAD. Thus, the clinical accuracy of EET may be enhanced.

ECG conduction disturbances and ryanodine receptor expression levels in occupational lead exposure workers

Objectives

A significant number of researches have evidenced that occupational lead (Pb) exposure increased risks of cardiovascular disease. However, evidences about the potential effects of Pb on the cardiac conduction system are sparse and inconclusive. Besides, ryanodine receptors (RyRs) induced dysfunction of cardiac excitation contraction coupling which is considered to be one of the mechanisms in cardiovascular diseases. Therefore, we examined the association between occupational Pb exposure and ECG conduction abnormalities, as well as RyRs in Pb-induced ECG abnormalities.

Methods

We investigated 529 Pb smelter workers, and measured blood lead (BPb), zinc protoporphyrin (ZPP), ECG outcomes and RyR expression levels. Based on BPb levels, the workers were divided into three groups: the BPb not elevated group, the BPb elevated group and the Pb poisoning group. Descriptive and multivariable analyses were performed.

Results

Compared with the BPb not elevated group, the Pb poisoning group had a higher incidence of high QRS voltage, and a lower level of RyR1 gene expression (p<0.05). Further unconditional multivariable logistic regression analyses showed that high QRS voltage was positively related to BPb (OR=1.045, 95% CI 1.014 to 1.078) and inversely associated with RyR1 expression (OR=0.042, 95% CI 0.002 to 0.980) after adjusting for potential confounders. In addition, multiple linear regression analyses showed that the QTc interval was positively associated with ZPP (β=0.299, 95% CI 0.130 to 0.468) after adjusting for potential confounders.

Conclusions

Our study provided evidences that occupational exposure to Pb may be associated with worse ECG outcomes (high QRS voltage), which might be related to decreased levels of RyR1.

Metabolic syndrome and its components as risk factors for prolonged corrected QT interval in apparently healthy Korean men and women

BACKGROUND

Metabolic syndrome (MetS) is clinically important because of its association with increased risk of sudden cardiac death, as well as cardiovascular disease-related mortality. Data between MetS and prolonged corrected QT (QTc) intervals, a useful predictor of sudden cardiac death, are limited in apparently healthy adults.

OBJECTIVE

This study determined the association between MetS and QTc interval in apparently healthy Korean men and women.

METHODS

We examined the association between MetS and QTc interval in 2157 Korean adults (1317 men and 840 women) in a health examination program but excluded participants with a history of ischemic heart disease, stroke, cardiac arrhythmia, cancer, thyroid, respiratory, renal, hepatobiliary, or rheumatologic disease. The QTc interval was calculated using Bazett's formula (QTc = QT/√RR). Multivariate-adjusted mean QTc values by the number of MetS components were calculated after sex stratification and compared using analysis of covariance test.

RESULTS

The overall prevalence of MetS was 30.5% in men and 19.8% in women. The QTc interval positively correlated with age, body mass index, blood pressure, fasting plasma glucose, triglycerides, and potassium level in both men and women and negatively correlated with calcium and potassium levels and smoking status in men. The multivariate-adjusted mean QTc value increased proportionally with increasing number of MetS components (P values < 0.001 for both men and women).

CONCLUSION

We confirmed the arrhythmogenic potential of MetS in apparently healthy Korean men and women. These findings suggest that careful monitoring of electrocardiography is necessary to evaluate possible arrhythmic risk in individuals with MetS.

The dispersion of myocardial repolarization in ischemic stroke and intracranial hemorrhage

BACKGROUND

Markers of dispersion of myocardial repolarization have been proposed to identify the patients at higher risk of malignant arrhythmic events. The aim of the present study is to assess a possible association of the electrocardiografic (ECG) markers of the dispersion of repolarization with the type of stroke, involvement of insula, neurological severity (National Institutes of Health Stroke Scale, NIHSS score), and disability (modified Rankin Scale, mRS score) in patients with a cerebrovascular event.

METHODS

We conducted a retrospective analysis based on data prospectively collected from consecutive patients with a cerebrovascular event who underwent 12‑lead ECG at admission to the Verona Stroke Unit.

RESULTS

Of the 63 patients included in the study, 55 had ischemic stroke and 8 intracranial hemorrhage. TpTe (time between the peak and the end of the T wave) and TpTe/QTc (TpTe/corrected time between the start of the Q wave and the end of the T wave) in lead V5 were higher in intracranial hemorrhage than in ischemic stroke (p = 0.03 and p = 0.04, respectively) and QT max (the longest QT calculated in the 12 leads) was higher in patients with involvement of insula (p ≤ 0.01). A correlation was found between QTc max and NIHSS score at admission (p = 0.02), QT max and NIHSS score at discharge (p = 0.05), and QT max and mRS score at discharge (p = 0.02).

CONCLUSIONS

TpTe and TpTe/QTc in V5 lead were associated with intracranial hemorrhage and QT max was associated with involvement of insula. The prolongation of QT was correlated with neurological severity and disability.

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.

Myocardial bridging is associated with exercise-induced ventricular arrhythmia and increases in QT dispersion

BACKGROUND

A myocardial bridge (MB) has been associated with ventricular arrhythmia and sudden death during exercise. QT dispersion (QTd) is a measure of abnormal repolarization and may predict ventricular arrhythmia. We investigated the frequency of ventricular arrhythmias during exercise and the QTd at rest and after exercise, in patients with an MB compared to a normal cohort.

METHODS

We studied the rest and stress ECG tracings of patients with an MB suspected by focal septal buckling on exercise echocardiography (EE) (Echo-MB group, N = 510), those with an MB confirmed by another examination (MB group, N = 110), and healthy controls (Control group, N = 198).

RESULTS

The frequency of exercise-induced premature ventricular contractions (PVCs) was significantly higher in the Echo-MB and MB groups compared with the Control group (both p < .001). In all, 25 patients (4.9%) in the Echo-MB group, seven patients (6.4%) in the MB group and no patients in the Control group had exercise-induced non-sustained ventricular tachycardia (NSVT). There was no difference in the baseline QTd between the groups. In the Echo-MB and MB groups, QTd postexercise increased significantly when compared with baseline (both p < .001). Patients with NSVT had a higher frequency of male gender and an even greater increase in QTd with exercise compared with the non-NSVT group.

DISCUSSION

There is an increased frequency of exercise-induced PVCs and NSVT in patients with MBs. Exercise significantly increases QTd in MB patients, with an even greater increase in QTd in MB patients with NSVT. Exercise in MB patients results in ventricular arrhythmias and abnormalities in repolarization.

Normal Ventricular Repolarization and QT Interval: Ionic Background, Modifiers, and Measurements

The QT interval on surface electrocardiogram represents the sum of depolarization and repolarization process of the ventricles. The ventricular recovery process, reflected by ST segment and T wave, mainly depends on the transmembrane outward transport of potassium ions to reestablish the endocellular electronegativity. Outward potassium channels represent a heterogeneous family of ionic carriers, whose global kinetics is modulated by heart rate and autonomic nervous activity. Several cardiac and noncardiac drugs and disease conditions, and several mutations of genes encoding ionic channels, generating distinct genetic channellopathies, may affect the ventricular repolarization, provoke QT interval prolongation and shortening, and increase the susceptibility to ventricular arrhythmias.

Reduced functional connectivity between ventromedial prefrontal cortex and insula relates to longer corrected QT interval in HIV+ and HIV- individuals

OBJECTIVE

Prolongation of the QT interval, i.e., measure of the time between the start of the Q wave and the end of the T wave, is a precursor to fatal cardiac arrhythmias commonly observed in individuals infected with the Human Immunodeficiency Virus (HIV), and is related to dysregulation of the autonomic nervous system. We investigated the relationship between QT interval length and resting state functional connectivity (rsFC) of the ventromedial prefrontal cortex (VMPFC), a core region of the brain that is involved with cardio-autonomic regulation.

METHOD

Eighteen HIV+ men on antiretroviral therapy and with no history of heart disease were compared with 26 HIV-negative control subjects who had similar demographic and cardio-metabolic characteristics. A seed-based rsFC analysis of the right and left VMPFC was performed at the individual subject level, and 2nd-level analyses were conducted to identify the following: group differences in connectivity, brain regions correlating with corrected (QTc) interval length before and after controlling for those group differences, and regions where seed-based rsFC correlates with CD4 count and QTc interval within HIV+ individuals.

RESULTS

HIV-negative adults showed greater rsFC between the VMPFC seed regions and several default mode network structures. Across groups greater rsFC with the left anterior insula was associated with shorter QTc intervals, whereas right posterior insula connectivity with the VMPFC correlated with greater QTc intervals. HIV patients with lower CD4 counts and higher QTc intervals showed greater rsFC between the right VMPFC and the right posterior insula and dorsal cingulate gyrus.

CONCLUSIONS

This study demonstrates that QTc interval lengths are associated with distinct patterns of VMPFC rsFC with posterior and anterior insula. In HIV patients, longer QTc interval and lower CD4 count corresponded to weaker VMPFC connectivity with the dorsal striatrum.

SIGNIFICANCE

A forebrain control mechanism may be implicated in the suppression of cardiovagal influence that confers risk for ventricular arrhythmias and sudden cardiac death in HIV+ individuals.

The evaluation of a new marker of transmyocardial repolarization parameters in ischemic stroke patients; T peak-T end (T p-e), T p-e/QTc

The cardiovascular manifestations of acute ischemic stroke have been well known. Several electrocardiography (ECG) abnormalities have been reported in patients following acute stroke, including QT interval prolongation, ST segment deviation and T-wave changes. This study aimed to investigate the changes in transmyocardial repolarization parameters, in ischemic stroke patients. The study is a prospective, blind, and controlled clinical study. The patients without cardiac disease who received ischemic stroke diagnoses were included in the study. ECG was received from the patients in the first hour and 72 h. The P, QT, T _p-e, T _p-e dispersion, and the T _p-e/QT ratio were calculated. Moreover, fifty-five stroke patients and 35 control subjects were included to the study. All dispersion values and T _p-e/QT_c ratio in patients group were higher than those of control group (p < 0.05 for all values). When evaluated between ECGs' on first and third days, it was found that decreasing on all dispersion values and T _p-e/QT_c ratio in ECGs on third day than ECGs on first day (p < 0.05 for all values). QT, QT_c, and T _p-e dispersions values in patients who have insular lobe involvement were higher than those of patients who do not have insular lobe involvement (p < 0.001 for all values). In this study, we showed that acute stroke increases that P _d, QT_d, QT_cd and new repolarization markers T _p-e and T _p-e/QT_c, during first 24 and 72 h in acute stroke patients without cardiovascular disease compared with the control group. The physicians should be aware about ventricular dysrhythmias in patients with ischemic stroke and these patients closely observed with cardiac monitoring, especially within first 24 h, and especially patients with insular lobe involvement.

Impact of atrial fibrillation on the clinical course of apical hypertrophic cardiomyopathy

BACKGROUND

Apical hypertrophic cardiomyopathy (ApHCM) is considered a 'benign' form of hypertrophic cardiomyopathy, with limited data on the long-term outcome. However, the clinical impact of atrial fibrillation (AF) in ApHCM is largely unknown. The hypothesis was that AF is common and has a prognostic implication in ApHCM.

METHODS

The occurrence of AF and outcome was assessed in 306 consecutive patients with ApHCM (68% male, 62±11 years).

RESULTS

AF occurred in 77 patients with ApHCM (prevalence, 25.2%; annual incidence, 4.6%/year) and was independently predicted by old age and large left atrium (>45 mm). Among 70 AF patients indicated with anticoagulation, 53 patients (76%) received warfarin. During a follow-up of 5.5±2.0 years, the patients with AF had a higher incidence of all-cause death, cardiovascular death and strokes (11.7% vs 1.3%, 6.5% vs 0.9% and 19.5% vs 2.6%, respectively, all p<0.05) than those without AF. When adjusted by the age and gender, those with AF still had an increased risk for all-cause death (HR 6.58; 95% CI 1.65-26.16, p=0.007) and strokes (HR 5.13; 95% CI 1.85 to 14.18, p=0.002). AF was detected before the time of stroke in 8 (53%) out of 15 patients with both AF and stroke. In addition, six out of eight patients were on anticoagulation at the time of stroke. The cause of death was a stroke in three (33%) out of nine patients with AF.

CONCLUSION

In patients with ApHCM, AF was common and was associated with a substantial risk for strokes and mortality suggesting that AF should be carefully managed in ApHCM.

New approach for visualization of relationships between RR and JT intervals

This paper presents the concept of perfect matrices of Lagrange differences which are used to analyze relationships between RR and JT intervals during the bicycle ergometry exercise. The concept of the perfect matrix of Lagrange differences, its parameters, the construction of the load function and the corresponding optimization problem, the introduction of internal and external smoothing, embedding of the scalar parameter time series into the phase plane—all these computational techniques allow visualization of complex dynamical processes taking place in the cardiovascular system during the load and the recovery processes. Detailed analysis is performed with one person’s RR and JT records only—but the presented techniques open new possibilities for novel interpretation of the dynamics of the cardiovascular system.

Associations of the serum long-chain omega-3 polyunsaturated fatty acids and hair mercury with heart rate-corrected QT and JT intervals in men: the Kuopio Ischaemic Heart Disease Risk Factor Study

PURPOSE

Long-chain omega-3 polyunsaturated fatty acids (PUFA) from fish have been associated with risk of cardiovascular diseases (CVD), especially sudden cardiac death (SCD). Mercury exposure, mainly due fish consumption, has been associated with higher risk. However, the impact of PUFAs or mercury on the ventricular cardiac arrhythmias, which often precede SCD, is not completely known. We investigated the associations of the serum long-chain omega-3 PUFAs and hair mercury with ventricular repolarization, measured by heart rate-corrected QT and JT intervals (QTc and JTc, respectively).

METHODS

A total of 1411 men from the prospective, population-based Kuopio Ischaemic Heart Disease Risk Factor Study, aged 42-60 years and free of CVD in 1984-1989, were studied.

RESULTS

Serum long-chain omega-3 PUFA concentrations were inversely associated with QTc and JTc (multivariate-adjusted P trend across quartiles = 0.02 and 0.002, respectively) and, during the mean 22.9-year follow-up, with lower SCD risk. However, further adjustments for QTc, JTc or hair mercury did not attenuate the associations with SCD. Hair mercury was not associated with QTc, JTc or SCD risk, but it slightly attenuated the associations of the serum long-chain omega-3 PUFA with QTc and JTc.

CONCLUSIONS

Higher serum long-chain omega-3 PUFA concentrations, mainly a marker for fish consumption, were inversely associated with QTc and JTc in middle-aged and older men from Eastern Finland, but QTc or JTc did not attenuate the inverse associations of the long-chain omega-3 PUFA with SCD risk. This suggests that prevention of prolonged ventricular repolarization may not explain the inverse association of the long-chain omega-3 PUFA with SCD risk.

Electrocardiography in rats: a comparison to human

Electrocardiography (ECG) in rats is a widely applied experimental method in basic cardiovascular research. The technique of ECG recordings is simple; however, the interpretation of electrocardiographic parameters is challenging. This is because the analysis may be biased by experimental settings, such as the type of anesthesia, the strain or age of animals. Here, we aimed to review electrocardiographic parameters in rats, their normal range, as well as the effect of experimental settings on the parameters variation. Furthermore, differences and similarities between rat and human ECG are discussed in the context of translational cardiovascular research.

The Prognostic Role of QTc Interval in Acute Myocarditis

BACKGROUND

Acute myocarditis is an inflammatory disease of the myocardium. Although a fulminant course of the disease is difficult to predict, it may lead to acute heart failure and death. Previous studies have demonstrated that reduced left ventricular systolic function and prolonged QRS duration can predict the fulminant course of acute myocarditis. This study aimed to identify whether prolonged QTc interval could also be predictive of fulminant disease in this population.

METHODS

We retrospectively included 40 patients diagnosed with acute myocarditis who were admitted to our hospital between 2002 and 2013. They were divided into the fulminant group (n = 9) and the non-fulminant group (n = 31). Clinical symptoms, laboratory findings, electrocardiographic, and echocardiographic parameters were analyzed. Multivariate logistic regression analysis was used to identify the independent factors predictive of fulminant disease.

RESULTS

Patients with fulminant myocarditis had a higher mortality rate than those with non-fulminant disease (55.6% vs. 0%, p < 0.001). Multivariate analysis revealed that wider QRS durations (133.22 ± 45.85 ms vs. 92.81 ± 15.56 ms, p = 0.030) and longer QTc intervals (482.78 ± 69.76 ms vs. 412.00 ± 33.31 ms, p = 0.016) were significant predictors associated with a fulminant course of myocarditis.

CONCLUSIONS

Prolonged QRS duration and QTc interval, upon patient admission, may be associated with an increased risk of fulminant disease and increased in-hospital mortality. Therefore, early recognition of fulminant myocarditis and early mechanical support could provide improved patient outcomes.

KEY WORDS

Fulminant myocarditis • Predictors • QRS complex • QTc interval.

Sudden Cardiac Risk Stratification with Electrocardiographic Indices - A Review on Computational Processing, Technology Transfer, and Scientific Evidence

Great effort has been devoted in recent years to the development of sudden cardiac risk predictors as a function of electric cardiac signals, mainly obtained from the electrocardiogram (ECG) analysis. But these prediction techniques are still seldom used in clinical practice, partly due to its limited diagnostic accuracy and to the lack of consensus about the appropriate computational signal processing implementation. This paper addresses a three-fold approach, based on ECG indices, to structure this review on sudden cardiac risk stratification. First, throughout the computational techniques that had been widely proposed for obtaining these indices in technical literature. Second, over the scientific evidence, that although is supported by observational clinical studies, they are not always representative enough. And third, via the limited technology transfer of academy-accepted algorithms, requiring further meditation for future systems. We focus on three families of ECG derived indices which are tackled from the aforementioned viewpoints, namely, heart rate turbulence (HRT), heart rate variability (HRV), and T-wave alternans. In terms of computational algorithms, we still need clearer scientific evidence, standardizing, and benchmarking, siting on advanced algorithms applied over large and representative datasets. New scenarios like electronic health recordings, big data, long-term monitoring, and cloud databases, will eventually open new frameworks to foresee suitable new paradigms in the near future.

Contribution of Electrocardiogram in the Differentiation of Cardiac Amyloidosis and Nonobstructive Hypertrophic Cardiomyopathy

Due to similar manifestations of hypertensive ventricular walls and abnormal ventricular compliance, it is difficult to differentiate cardiac amyloidosis (CA) and nonobstructive hypertrophic cardiomyopathy (NOHCM) clinically. The purpose of the study was to investigate the value of electrocardiography (ECG) in the differentiation of the two diseases.

METHODS

We enrolled 46 consecutive patients with CA and 64 patients with NOHCM and compared their ECG characteristics.Compared with NOHCM patients, the ECG of CA patients showed more low voltage on limb leads (50% versus 1.6%), atrioventricular block (21.7% versus 4.7%), pseudo-infarct pattern (84.8% versus 39.1%), and longer QRS duration (104 ± 25 versus 98 ± 14 ms) (all P < 0.05). The QRS complex voltage of avR demonstrated the highest diagnostic performance (sensitivity 89%, specificity 94%, cut-off value 0.45mV) as assessed by ROC analysis. The combination of the R wave voltage of I and avR reached a sensitivity of 95% and a specificity of 87% for the diagnosis of amyloidosis.Compared with NOHCM patients, CA patients showed more ECG characteristics of low voltage on limb leads, pseudo-infarct pattern, atrioventricular block, and longer QRS duration. The combination of the R wave voltage of I, avR, and QRS was of diagnostic value in the differentiation of CA from NOHCM.

High risk of abnormal QT prolongation in the early morning in diabetic and non-diabetic patients with severe hypoglycemia

BACKGROUND

Several studies have suggested that the occurrence of severe hypoglycemia during sleep may be more dangerous for cardiac arrhythmia than that in the day-time.

METHODS

We performed a retrospective study between January 2006 and March 2012 to assess electrocardiograms during severe hypoglycemia in patients with or without diabetes.

RESULTS

A total of 59,602 patients who visited the emergency room by ambulance were screened, and 287 patients with severe hypoglycemia were enrolled. The median blood glucose levels in patients with (DM, n = 192) and without diabetes (non-DM, n = 95) were 30 and 45 mg/dL, respectively. During severe hypoglycemia, the incidence of abnormal QT prolongation was significantly higher in the early morning (4-10 a.m.) than at other times (DM group, 74.3% versus 54.1%, P = 0.02; non-DM group, 78.3% versus 50.0%, P = 0.01). Multivariate logistic regression analysis identified the occurrence of severe hypoglycemia in the early morning as a strong factor for abnormal QT prolongation (DM group, odds ratio [OR] 2.80, 95% confidence interval [CI] 1.15-6.80, P = 0.02; non-DM group, OR 4.53, 95% CI 1.30-15.74, P = 0.01).

CONCLUSIONS

The incidence of abnormal QT prolongation during severe hypoglycemia was significantly higher in the early morning than at all other times, independent of the cause of severe hypoglycemia.

Cardiac and non-cardiac causes of T-wave inversion in the precordial leads in adult subjects: A Dutch case series and review of the literature

AIM: To describe the electrocardiographic (ECG) phenomena characterized by T-wave inversion in the precordial leads in adults and to highlight its differential diagnosis.

METHODS: A retrospective chart review of 8 adult patients who were admitted with ECG T-wave inversion in the anterior chest leads with or without prolongation of corrected QT (QTc) interval. They had different clinical conditions. Each patient underwent appropriate clinical assessment including investigation for myocardial involvement. Single and multimodality non-invasive, semi-invasive and invasive diagnostic approach were used to ascertain the diagnosis. The diagnostic assessment included biochemical investigation, cardiac and abdominal ultrasound, cerebral and chest computed tomography, nuclear medicine and coronary angiography.

RESULTS: Eight adult subjects (5 females) with a mean age of 66 years (range 51 to 82) are analyzed. The etiology of T-wave inversion in the precordial leads were diverse. On admission, all patients had normal blood pressure and the ECG showed sinus rhythm. Five patients showed marked prolongation of the QTc interval. The longest QTc interval (639 ms) was found in the patient with pheochromocytoma. Giant T-wave inversion (≥ 10 mm) was found in pheochromocytoma followed by electroconvulsive therapy and finally ischemic heart disease. The deepest T-wave was measured in lead V₃ (5 ×). In 3 patients presented with mild T-wave inversion (patients 1, 5 and 4 mm), the QTc interval was not prolonged (432, 409 and 424 msec), respectively.

CONCLUSION: T-wave inversion associated with or without QTc prolongation requires meticulous history taking, physical examination and tailored diagnostic modalities to reach rapid and correct diagnosis to establish appropriate therapeutic intervention.

Clinical profile of pediatric patients with long QT syndrome masquerading as seizures

OBJECTIVE

To study the clinical profile of patients with long QT syndrome presenting as seizures.

METHODS

Retrospective analysis of six pediatric patients admitted at authors' institute between October 2008 and January 2013 with seizures and a presumptive diagnosis of long QT syndrome (LQTS) was done. The diagnosis was made on the basis of updated Schwartz diagnostic criteria. Clinical data, investigation profile and follow up of patients was recorded in a standard format and analysed.

RESULTS

All the 6 patients in the study were boys with a mean age of 10.3 ± 2.8 y at the time of diagnosis. The lag period between symptom onset and diagnosis was 5.6 ± 3.14 y. All patients had history of seizures with a history of precipitating event in 4 patients. Average baseline QTc interval was 556 ± 41.31 ms. Mean Schwartz score was 6.66 ± 1.16. Polymorphic VT was documented in 4 patients. After initiating standard treatment with betablockers, nicorandil, spironolactone or pacemaker, all the six patients were asymptomatic at a mean follow up period of 17.5 mo, with no recurrence of seizures.

CONCLUSIONS

LQTS can cause seizures due to prolonged ventricular arrhythmias in high risk subgroup. Children, who present with LQTS and seizures, generally have a precipitating event causing seizures, and they respond well to drug therapy.

The association of prolonged QT interval on electrocardiography and chronic lead exposure

OBJECTIVES

The aim of this study was to examine the association of lead exposure with cardiac conduction disturbance among lead-exposed and nonexposed workers in Taiwan.

METHODS

The participants comprised 312 lead workers and 329 referents who had no known occupational lead exposure. During their annual health examination, they were invited to take part in the survey. Standard resting 12-lead electrocardiograms were obtained and the electrocardiographic features studied were related to blood lead levels (BLLs).

RESULTS

The mean BLLs were 26.05 (SD = 13.98) and 2.62 (SD = 1.42) μg/dL in lead-exposed and reference groups, respectively. Compared with the referents, lead workers had significantly shorter PR interval and longer QTc interval. Especially, workers with BLL > 30 μg/dL had the highest risk after adjusting for age, sex, body mass index, and other potential confounders.

CONCLUSION

The data suggest that lead exposure is positively associated with prolonged QTc interval.

The effect of aortic coarctation surgical repair on QTc and JTc dispersion in severe aortic coarctation newborns: a short-term follow-up study

Sudden death is a possible occurrence for newborns younger than 1 year with severe aortic coarctation (CoA) before surgical correction. In our previous study, we showed a significant increase of QTc-D and JTc-D in newborns with isolated severe aortic coarctation, electrocardiographic parameters that clinical and experimental studies have suggested could reflect the physiological variability of regional and ventricular repolarization and could provide a substrate for life-threatening ventricular arrhythmias. The aim of the current study was to evaluate the effect of surgical repair of CoA on QTc-d, JTc-d in severe aortic coarctation newborns with no associated congenital cardiac malformations. The study included 30 newborns (18M; 70+/-12 h old) affected by severe congenital aortic coarctation, without associated cardiac malformations. All newborns underwent to classic extended end-to-end repair. Echocardiographic and electrocardiographic measurements were performed in each patient 24 h before and 24 h after the interventional procedure and at the end of the follow-up period, 1 month after the surgical correction. All patients at baseline, 24 h and one month after CoA surgical repair did not significantly differ in terms of heart rate, weight, height, and echocardiographic parameters. There were no statistically significant differences in QTc-D (111.7+/-47.4 vs 111.9+/-63.8 ms vs 108.5+/-55.4 ms; P=0.4) and JTc-D (98.1+/-41.3 vs 111.4+/-47.5 vs 105.1+/-33.4 ms; P=0.3) before, 24 h and 1 month after CoA surgical correction. In conclusions, our study did not show a statistically significant decrease in QTc-D and JTc-D, suggesting the hypothesis that the acute left ventricular afterload reduction, related to successful CoA surgical correction, may not reduce the ventricular electrical instability in the short-term follow-up.

Iron deposition following chronic myocardial infarction as a substrate for cardiac electrical anomalies: initial findings in a canine model

Purpose

Iron deposition has been shown to occur following myocardial infarction (MI). We investigated whether such focal iron deposition within chronic MI lead to electrical anomalies.

Methods

Two groups of dogs (ex-vivo (n = 12) and in-vivo (n = 10)) were studied at 16 weeks post MI. Hearts of animals from ex-vivo group were explanted and sectioned into infarcted and non-infarcted segments. Impedance spectroscopy was used to derive electrical permittivity () and conductivity (). Mass spectrometry was used to classify and characterize tissue sections with (IRON+) and without (IRON-) iron. Animals from in-vivo group underwent cardiac magnetic resonance imaging (CMR) for estimation of scar volume (late-gadolinium enhancement, LGE) and iron deposition (T2*) relative to left-ventricular volume. 24-hour electrocardiogram recordings were obtained and used to examine Heart Rate (HR), QT interval (QT), QT corrected for HR (QTc) and QTc dispersion (QTcd). In a fraction of these animals (n = 5), ultra-high resolution electroanatomical mapping (EAM) was performed, co-registered with LGE and T2* CMR and were used to characterize the spatial locations of isolated late potentials (ILPs).

Results

Compared to IRON- sections, IRON+ sections had higher, but no difference in. A linear relationship was found between iron content and (p<0.001), but not (p = 0.34). Among two groups of animals (Iron (<1.5%) and Iron (>1.5%)) with similar scar volumes (7.28%±1.02% (Iron (<1.5%)) vs 8.35%±2.98% (Iron (>1.5%)), p = 0.51) but markedly different iron volumes (1.12%±0.64% (Iron (<1.5%)) vs 2.47%±0.64% (Iron (>1.5%)), p = 0.02), QT and QTc were elevated and QTcd was decreased in the group with the higher iron volume during the day, night and 24-hour period (p<0.05). EAMs co-registered with CMR images showed a greater tendency for ILPs to emerge from scar regions with iron versus without iron.

Conclusion

The electrical behavior of infarcted hearts with iron appears to be different from those without iron. Iron within infarcted zones may evolve as an arrhythmogenic substrate in the post MI period.

The comparison in reduction of QT dispersion after primary percutaneous coronary intervention according to existence of thrombectomy in ST-segment elevation myocardial infarction

BACKGROUND

Primary percutaneous coronary intervention (PPCI) is the standard treatment in patients with ST-segment elevation myocardial infarction (STEMI). Thrombectomy devices are used to remove thrombus or to prevent embolization of thrombus and plaque during PPCI. QT dispersion (the difference between maximal and minimal QT interval calculated on a standard 12-lead electrocardiogram) represents the regional nonuniformity of ventricular repolarization. It may reflect early coronary reperfusion in reducing electrophysiological instability by decreasing QT dispersion in the recovery phase after acute STEMI.

HYPOTHESIS

Our aim was to show whether an additional effect of thrombectomy on reducing QT dispersion will be seen in patients undergoing PPCI for STEMI.

METHODS

The study population included 80 consecutive patients who were admitted to the hospital within 12 hours after the onset of acute STEMI and angiographic evidence of intraluminal thrombus in the infarct-related artery. Patients with atrial fibrillation or flutter, intraventricular conduction abnormalities, pre-excitation, cardiogenic shock, cardiomyopathy, ventricular hypertrophy, and severe valvular heart disease were excluded from the study.

RESULTS

There were no significant differences between groups regarding gender, age, cardiovascular risk factors, and time from symptom onset to treatment, except for smoking, which was much higher in the PPCI plus thrombectomy group. Infarct-related artery distribution (left anterior descending artery [LAD] to non-LAD), and neither the rate of balloon predilatation nor stent implantation were different between groups. Successful coronary patency was achieved in each case. QT interval measurements were similar between groups at admission. However, at 24 hours, QT and QTc dispersions were less in the PPCI plus thrombectomy group (41 ± 9 vs 33 ± 7 ms, P < 0.05 and 45 ± 8 vs 35 ± 7 ms, P = 0.03, respectively), but not in the other QT interval measurements. When patients were divided into 2 groups according to infarct-related artery (LAD and non-LAD groups), QT interval measurement parameters did not show any significant differences.

CONCLUSIONS

Thrombectomy additional to PPCI helps more effective reperfusion at the microvascular level and provides additional prognostic information.

Cigarette Smoking Is Associated with Prolongation of the QTc Interval Duration in Patients with Type 2 Diabetes Mellitus

Aims. Aim of the study was to evaluate the effect of smoking on autonomic nervous system (ANS) activity and QTc interval duration in patients with Type 2 diabetes mellitus (T2DM). Methods. A total of 70 patients with T2DM (35 chronic smokers, 35 nonsmokers) treated with oral antidiabetic medications underwent continuous ECG Holter monitoring for 24 hours and analysis of time- and frequency-domain measures of heart rate variability (HRV). HRV over short time was also assessed using the deep breathing test. In addition, baroreflex sensitivity (BRS) was evaluated using the spontaneous sequence method. The mean QTc interval was measured from the 24-hour ECG recordings. Results. Smokers had lower body mass index (BMI) and exhibited higher 24-hour mean heart rate. There was no difference regarding all measures of ANS activity between the two groups. Smokers showed increased mean QTc duration during the 24 hours (439.25 ± 26.95 versus 425.05 ± 23.03 ms, P = 0.021) as well as in both day (439.14 ± 24.31 ms, P = 0.042) and night periods (440.91 ± 32.30 versus 425.51 ± 24.98 ms, P = 0.033). The association between smoking status and mean QTc interval persisted after adjusting for BMI. Conclusions. Cigarette smoking is associated with prolongation of the QTc interval in patients with T2DM by a mechanism independent of ANS dysfunction.