Reduction in QT interval dispersion by successful thrombolytic therapy in acute myocardial infarction. TEAM-2 Study Investigators

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 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.

Can QT dispersion improve the accuracy of stress ECG TMT in detecting myocardial ischemia in chronic stable CAD patients? A stress myocardial perfusion imaging study

BACKGROUND

QT dispersion (QTd) is related to regional variations in myocardial repolarization. Our study aims to assess the value of QTd in prediction of myocardial ischemia and its severity during stress imaging. We enrolled one hundred patients having stable coronary artery disease (CAD) and fulfilling the "Appropriateness criteria for cardiac radionuclide imaging" (MPI). They were divided into group I including patients with MPI-detected ischemia (50 patients) and group II including patients with normal perfusion scan (50 patients). We excluded unstable CAD and all other causes affecting QTd. During isotope scan, ECGs were taken and QTd was calculated at rest and at maximum heart rate.

RESULTS

QTd was significantly higher in the ischemic group both at rest and exercise (P = 0.000). QTd difference, the difference between QTd at rest and stress, was calculated. QTd difference was significantly lower in normal than in ischemic group (P = 0.003). There was a significant positive correlation between QTd difference and defect size (P = 0.04).

CONCLUSION

QTd increases in ischemia and the QTd difference (between rest and stress) correlates positively with severity of ischemia. QTd and QTd difference could be used to improve the accuracy of stress imaging test.

ECG Changes in Melanoma Patients Undergoing Cancer Therapy-Data From the ECoR Registry

We aimed to evaluate whether therapy with immune checkpoint inhibitors (ICI) leads to changes in electrocardiogram (ECG) parameters in melanoma patients. We retrospectively examined 41 patients (46% women, age 61 ± 12years) with advanced melanoma (stage III/IV) before and during ICI treatment from our “Essen Cardio-oncology Registry” (ECoR). ECGs were analyzed before and 4–12 weeks after therapy started (follow-up, 90 ± 51 days). Heart rate, PR time, QRS duration and duration of the corrected QT (QTc) interval were recorded. QT dispersion (QTd) was calculated. Heart rate, PR time, QRS and QTc did not differ when comparing values before and after therapy started. QTd was prolonged after therapy started (32 ± 16 ms vs. 47 ± 19 ms, n = 41, p < 0.0001). Subgroup analyses revealed prolonged QTd in patients that received a combination immunotherapy with ipilimumab and nivolumab (31 ± 14 ms vs. 50 ± 14 ms, n = 21, p < 0.0001), while QTd in patients with anti–programmed death 1 (PD-1) inhibitor monotherapy did not change after therapy started. QTd is prolonged in patients under ICI combination therapy, potentially signaling an increased susceptibility to ventricular arrhythmias.

Evaluation of Tp-e interval and Tp-e/QT ratio in major burn patients

INTRODUCTION

Major burn injury is an acute stress reaction with systemic effects. Major burn injury has been associated with a number of cardiovascular dysfunctions, including ventricular arrhythmias. The mechanism of increased ventricular arrhythmias in burn patients uncertain. The aim of the present study was to evaluate the ventricular repolarization by using the Tp-e interval, Tp-e/QT ratio, and Tp-e/QTc ratio as candidate markers of ventricular arrhythmias in patients with major burn patients. In addition, the relationship between the repolarization parameters and the CRP(C-reactive protein) and ABSI(Abbreviated Burn Severity Index) score was investigated.

METHODS

55 major burn patients, 55 age and sex matched healthy subjects were included in the study between January 2017 and September 2019. The risk of ventricular arrhythmias was evaluated by calculating the electrocardiographic Tp-e and QT interval, corrected QT(QTc), Tp-e/QT and Tp-e/QTc ratios. ABSI score was calculated in burn patients. Left ventricular functions were evaluated by echocardiography.

RESULTS

Tp-e interval (80.7 ± 5.7 vs. 67.4 ± 5.7; p < 0.001), Tp-e/QT ratio (0.21 ± 0.01 vs. 0.18 ± 0.01; p < 0.001) and Tp-e/QTc ratio (0.20 ± 0.01 vs.0.17 ± 0.01; p < 0.001) were significantly higher in major burn patients than the control group. There was a significant positive correlation between Tp-e interval, Tp-e/QTc ratio and ABSI score in major burn patients (r = 0.870, p < 0.001, r = 0.312, p = 0.020 consecutively).

CONCLUSION

Our study showed for the first time in literature that the Tp-e interval, Tp-e/QT ratio, and Tp-e/QTc ratio, which were evaluated electrocardiographically in major burn patients, were prolonged compared with normal healthy individuals. A positive correlation was determined between repolarization parameters and ABSI score. Whether these changes increase the risk of ventricular arrhythmia deserve further studies.

TAKE-HOME MESSAGE

Tp-e interval, Tp-e/QT ratio, and Tp-e/QTc ratio, which were evaluated electrocardiographically in major burn patients, were prolonged compared with normal healthy individuals and a positive correlation was found between these repolarization parameters and burn severity.

Delayed Reperfusion-Coronary Artery Reperfusion Close to Complete Myocardial Necrosis Benefits Remote Myocardium and Is Enhanced by Exercise

The present study aimed to analyze the effects of reperfusion of a distant coronary artery on cardiac function, the ultrastructure, and the molecular environment of the remote myocardium immediately after the completion of myocardial regional necrosis: delayed reperfusion (DR). Additionally, the effects of prior exercise on the outcomes of DR were investigated. Female rats with permanent occlusion or delayed reperfusion were randomly assigned to an exercise (swimming, 1 h/day, 5 days/week for 8 weeks) or sedentary protocol. Thus, the study included the following four groups: sedentary permanent occlusion, exercise permanent occlusion, sedentary delayed reperfusion, and exercise delayed reperfusion. The descending coronary artery was occluded for 1 h. Reperfusion was confirmed by contrast echocardiography, and the rats were observed for 4 weeks. Permanent occlusion and DR caused similar myocardial infarction sizes among the four groups. Interestingly, exercise significantly decreased the mortality rate. Delayed reperfusion resulted in significant benefits, including enhanced hemodynamics and papillary muscle contraction, as well as reduced apoptosis and collagen content. Protein calcium kinetics did not change. Meanwhile, developed tension and the Frank–Starling mechanism were enhanced, suggesting that calcium sensitivity was intensified in myofilaments. Remarkable remote myocardial benefits occurred after distant DR, and prior exercise intensified cardiac recovery. Our findings provide valuable information about DR. Our data might explain the better clinical outcomes in recent studies showing that late reperfusion could improve heart failure in patients with myocardial infarction. In conclusion, DR has remote myocardial benefits, including inotropism enhancement, pulmonary congestion reduction, and collagen and apoptosis attenuation, which are enhanced by prior exercise.

Regional QT Interval Dispersion as an Early Predictor of Reperfusion in Patients with Acute Myocardial Infarction after Fibrinolytic Therapy

BACKGROUND

Patients with ST-elevation acute myocardial infarction attending primary care centers, treated with pharmaco-invasive strategy, are submitted to coronary angiography within 2-24 hours of fibrinolytic treatment. In this context, the knowledge about biomarkers of reperfusion, such as 50% ST-segment resolution is crucial.

OBJECTIVE

To evaluate the performance of QT interval dispersion in addition to other classical criteria, as an early marker of reperfusion after thrombolytic therapy.

METHODS

Observational study including 104 patients treated with tenecteplase (TNK), referred for a tertiary hospital. Electrocardiographic analysis consisted of measurements of the QT interval and QT dispersion in the 12 leads or in the ST-segment elevation area prior to and 60 minutes after TNK administration. All patients underwent angiography, with determination of TIMI flow and Blush grade in the culprit artery. P-values < 0.05 were considered statistically significant.

RESULTS

We found an increase in regional dispersion of the QT interval, corrected for heart rate (regional QTcD) 60 minutes after thrombolysis (p = 0.06) in anterior wall infarction in patients with TIMI flow 3 and Blush grade 3 [T3B3(+)]. When regional QTcD was added to the electrocardiographic criteria for reperfusion (i.e., > 50% ST-segment resolution), the area under the curve increased to 0.87 [(0.78-0.96). 95% IC. p < 0.001] in patients with coronary flow of T3B3(+). In patients with ST-segment resolution >50% and regional QTcD > 13 ms, we found a 93% sensitivity and 71% specificity for reperfusion in T3B3(+), and 6% of patients with successful reperfusion were reclassified.

CONCLUSION

Our data suggest that regional QTcD is a promising non-invasive instrument for detection of reperfusion in the culprit artery 60 minutes after thrombolysis.

Prolonged QT and myocardium recovery after primary PCI: a cMRI study

BACKGROUND

The presence of viable stunned myocardium recovering after primary angioplasty is not easy to identify in the early phase of acute myocardial infarction (AMI) by noninvasive bed-side methods. We therefore aimed to assess whether a simple electrocardiogram parameter may be of help in identifying the presence of stunned viable myocardium recovering after reperfusion with primary angioplasty.

MATERIALS AND METHODS

A total of 14 consecutive patients with ST-elevation AMI (STEMI) were enrolled in the study and underwent QT duration assessment after admission: the difference between QT corrected (QTc) in the ischaemic areas and QTc values in nonischaemic areas was therefore calculated and compared with the presence and the extension of viable stunned myocardium, assessed by comparing akinetic/dyskinetic areas at admission echocardiography with akinetic/dyskinetic areas and extension of scar at 6-month cardiac magnetic resonance imaging (cMRI).

RESULTS

In subjects with viable recovering myocardium, 75% had a QTc max > 440 ms (vs. 17%, P = 0·03); higher differential QTc values and smaller scar areas were found (33 ms vs. -17 ms, 14% vs. 27%, P = 0·03, 0·06 respectively). Differential QTc values > 0 were able to identify the presence of viable myocardium with an odds ratio of 35 (P < 0·05, sensitivity 88%, specificity 83%, positive predictive power 88%, negative predictive power of 83%). Differential QTc values were related to the extension of viable recovering myocardium (P < 0·001).

CONCLUSION

Viable myocardium recovering after primary angioplasty in STEMI may be predicted by the presence of increased QTc values in ischaemic areas in comparison with nonischaemic areas.

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.

Review: Diabetes and the QT interval: time for debate

The electrocardiographic QT interval has been extensively studied in ischaemic heart disease. Recently, there has been increasing interest in the relationship between diabetes and QT abnormalities. QT prolongation and increased QTd have been shown to predict cardiac death in both type 1 and type 2 diabetes mellitus. Although there is general agreement that QT interval is affected by cardiac ischaemia, the effect of hyperglycaemia on QT measures is controversial. There are also problems surrounding QTd. First, there is controversy as to whether the measure has any physiological meaning; secondly, there is no universally accepted method of measurement and hence no consensus about the upper limit of normal. Nevertheless, several studies have shown increased QTd in diabetic patients suggesting that assessment of the QT interval could be a cost effective way of stratifying aggressive treatment could be directed appropriately to such patients according to cardiovascular risk so that improve outcome.

M1- and M2-Type Macrophage Responses Are Predictive of Adverse Outcomes in Human Atherosclerosis

Atherosclerosis is an inflammatory disease caused by endothelial injury, lipid deposition, and oxidative stress. This progressive disease can be converted into an acute clinical event by plaque rupture and thrombosis. In the context of atherosclerosis, the underlying cause of myocardial infarction and stroke, macrophages uniquely possess a dual functionality, regulating lipid accumulation and metabolism and sustaining the chronic inflammatory response, two of the most well-documented pathways associated with the pathogenesis of the disease. Macrophages are heterogeneous cell populations and it is hypothesized that, during the pathogenesis of atherosclerosis, macrophages in the developing plaque can switch from a pro-inflammatory (MΦ1) to an anti-inflammatory (MΦ2) phenotype and vice versa, depending on the microenvironment. The aim of this study was to identify changes in macrophage subpopulations in the progression of human atherosclerotic disease. Established atherosclerotic plaques from symptomatic and asymptomatic patients with existing coronary artery disease undergoing carotid endarterectomy were recruited to the study. Comprehensive histological and immunohistochemical analyses were performed to quantify the cellular content and macrophage subsets of atherosclerotic lesion. In parallel, expression of MΦ1 and MΦ2 macrophage markers were analyzed by real-time PCR and Western blot analysis. Gross analysis and histological staining demonstrated that symptomatic plaques presented greater hemorrhagic activity and the internal carotid was the most diseased segment, based on the predominant prevalence of fibrotic and necrotic tissue, calcifications, and hemorrhagic events. Immunohistochemical analysis showed that both MΦ1 and MΦ2 macrophages are present in human plaques. However, MΦ2 macrophages are localized to more stable locations within the lesion. Importantly, gene and protein expression analysis of MΦ1/MΦ2 markers evidenced that MΦ1 markers and Th1-associated cytokines are highly expressed in symptomatic plaques, whereas expression of the MΦ2 markers, mannose receptor (MR), and CD163 and Th2 cytokines are inversely related with disease progression. These data increase the understanding of atherosclerosis development, identifying the cellular content of lesions during disease progression, and characterizing macrophage subpopulation within human atherosclerotic plaques.

Ventricular repolarization markers for predicting malignant arrhythmias in clinical practice

Malignant cardiac arrhythmias which result in sudden cardiac death may be present in individuals apparently healthy or be associated with other medical conditions. The way to predict their appearance represents a challenge for the medical community due to the tragic outcomes in most cases. In the last two decades some ventricular repolarization (VR) markers have been found to be useful to predict malignant cardiac arrhythmias in several clinical conditions. The corrected QT, QT dispersion, Tpeak-Tend, Tpeak-Tend dispersion and Tp-e/QT have been studied and implemented in clinical practice for this purpose. These markers are obtained from 12 lead surface electrocardiogram. In this review we discuss how these markers have demonstrated to be effective to predict malignant arrhythmias in medical conditions such as long and short QT syndromes, Brugada syndrome, early repolarization syndrome, acute myocardial ischemia, heart failure, hypertension, diabetes mellitus, obesity and highly trained athletes. Also the main pathophysiological mechanisms that explain the arrhythmogenic predisposition in these diseases and the basis for the VR markers are discussed. However, the same results have not been found in all conditions. Further studies are needed to reach a global consensus in order to incorporate these VR parameters in risk stratification of these patients.

Survey of the effect of streptokinase on ventricular repolarization by examining the QT dispersion in patients with acute myocardial infraction in Seyed-Al-Shohada hospital, Urmia

Cardiovascular events are the most common cause of morbidity and mortality throughout the world and myocardial infarction is the most common cause of these accidents. Myocardial infarction impairs the mechanical and electrical activity of the heart that these disorders predispose the patient to cardiac arrhythmias including ventricular tachycardia. QT dispersion is an important parameter to evaluate the heterogeneity of ventricular repolarization that minimal and the maximum interval is QTc in 12-lead EKG. In this study, 200 patients with the diagnosis of acute myocardial infraction with ST-segment elevation were hospitalized and treated with streptokinase. Patient records were extracted from the medical records department. EKG was studied before receiving streptokinase, an hour after receiving streptokinase and 4 days later for calculating and comparing QTd. It was concluded that QTd mean in EKG one hour after receiving streptokinase is decreased compared to pre-operation but this decline is not statistically significant. QTd mean in EKG day 4 after MI is slightly increased compared to the baseline, which is not statistically significant.

Repeated Aborted Sudden Cardiac Death with Long QT Syndrome in a Patient with Anomalous Origin of the Right Coronary Artery from the Left Coronary Cusp

A 15-year-old female with a prior history of aborted cardiac death and surgical correction of anomalous origin of the right coronary artery (RCA) presented with polymorphic ventricular tachycardia. Her electrocardiogram after defibrillation was suggestive of congenital long QT syndrome (LQTS). The patient was treated with a β-blocker and remained free from ventricular arrhythmia during the follow-up of more than 6 months. Here, we present the case of a young female with repeated aborted cardiac death accompanied by anomalous origin of the RCA and congenital LQTS for the first time.

Decreases in electrocardiographic R-wave amplitude and QT interval predict myocardial ischemic infarction in Rhesus monkeys with left anterior descending artery ligation

Clinical studies have demonstrated the predictive values of changes in electrocardiographic (ECG) parameters for the preexisting myocardial ischemic infarction. However, a simple and early predictor for the subsequent development of myocardial infarction during the ischemic phase is of significant value for the identification of ischemic patients at high risk. The present study was undertaken by using non-human primate model of myocardial ischemic infarction to fulfill this gap. Twenty male Rhesus monkeys at age of 2–3 years old were subjected to left anterior descending artery ligation. This ligation was performed at varying position along the artery so that it produced varying sizes of myocardial infarction at the late stage. The ECG recording was undertaken before the surgical procedure, at 2 h after the ligation, and 8 weeks after the surgery for each animal. The correlation of the changes in the ECG waves in the early or the late stage with the myocardial infarction size was analyzed. The R wave depression and the QT shortening in the early ischemic stage were found to have an inverse correlation with the myocardial infarction size. At the late stage, the R wave depression, the QT prolongation, the QRS score, and the ST segment elevation were all closely correlated with the developed infarction size. The poor R wave progression was identified at both the early ischemic and the late infarction stages. Therefore, the present study using non-human primate model of myocardial ischemic infarction identified the decreases in the R wave and the QT interval as early predictors of myocardial infarction. Validation of these parameters in clinical studies would greatly help identifying patients with myocardial ischemia at high risk for the subsequent development of myocardial infarction.

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.

Selection of patient for cardiac resynchronization therapy: role of QT corrected dispersion

AIMS

About 30 to 50% of patients undergoing cardiac resynchronization therapy (CRT) may not show clinical or echocardiographic improvement, despite fulfilling guidelines recommendations for CRT. For this reason, we need a more accurate method to assess CRT eligibility. The aims of this study were to verify, on a 12-month follow-up, the usefulness of QT corrected dispersion (QTcD) in a patient's selection for CRT.

METHODS

We stratified 53 patients who underwent CRT, into two groups based on the estimation of QTcD, that is, QTcD > 60 ms and QTcD ≤ 60 ms. In all patients were performed New York Heart Association (NYHA) class determination, six-minute walking test, QtcD, and QRS measurements, and complete echocardiographic assessment at 1, 3, 6, and 12 months after implantation.

RESULTS

At baseline, there were no significant differences in clinical, echocardiographic, and electrocardiographic parameters duration between two groups. At 12-month follow-up between the two groups, there were significant differences in NYHA (1.2 ± 0.4 vs 2 ± 0.6; P < 0.01), six-minute walking distance (422 ± 68 vs 364 ± 68; P < 0.01), left ventricular (LV) ejection fraction (34 ± 7% vs 28 ± 6%; P < 0.01), LV end-diastolic diameter (57 ± 7 vs 63 ± 8; P < 0.01), and LV intraventricular dyssynchrony (24 ± 14 vs 39 ± 23; P < 0.01).

CONCLUSION

This study suggests that QTc dispersion in addition to QRS duration could improve the sensitivity of electrocardiogram in a patient's selection for CRT.

Marked QT prolongation and ventricular tachycardia of a transient nature in young children with cardiomyopathy

Significant prolongation of the QT interval in pediatric patients with cardiomyopathy is rare. We report two cases of dilated myopathy with transient and dramatic QT prolongation. Both had associated ventricular arrhythmias, with one having torsade de pointes, and the other nonsustained ventricular tachycardia. Normalization of their QTc occurred as their ventricular function improved.

Specific electrocardiographic features associated with Cushing's disease

OBJECTIVE

Hypercortisolaemia is associated with an increased risk of cardiovascular disease (CVD), either through a direct action on the myocardium or by increased traditional cardiovascular risk factors. The aim of this study was to investigate whether the alterations in the ECG in Cushing's disease (CD) are predictable from risk factor analysis alone.

DESIGN

In 79 patients with a diagnosis of CD, retrospectively recruited, ECG features [corrected for heart rate QT (QTc), QTc dispersion (QTcd), left ventricular hypertrophy (ECG-LVH), right ventricular hypertrophy (ECG-RVH)], systolic (SBP) and diastolic (DBP) blood pressure were assessed. Biochemical, hormonal (cortisol at 09·00 h or cortisol day curve, CDC) and carbohydrate abnormalities (CHA), history of hypertension and cardiovascular disease were recorded. For comparison reasons, a group of 42 healthy subjects matched for gender, age and body mass index previously subjected to ECG assessment were selected.

RESULTS

In patients with CD, we noted the following prevalence: metabolic syndrome 39%, hypertension 81%, CVD 21·5%, hypercholesterolaemia 37%, hypertriglyceridaemia 29%, CHA 41%, but a history of cardiac dysrhythmia was only noted in a single patient. No difference in QTc or QTcd was shown between patients with normal or low potassium levels. QTcd >50 ms was associated with both increased ECG-LVH and ECG-RVH. When compared to the control group, patients had longer QTcd (P < 0·001), more prevalent LVH (P < 0·001) and RVH (P = 0·001), and higher SBP and DBP (P < 0·001), but similar QTc. Both CD and ECG evidence of LVH predicted prolonged QTcd, but the association of CD with a prolonged QTcd was independent of other risk factors, including hypertension.

CONCLUSIONS

Prolonged QTcd in association with ECG evidence of LVH appears to be the specific feature of CD. This may be relevant in the choice of medical therapy for CD and for consideration of treatment of the comorbidities that are associated with hypercortisolaemia.

Angioplasty decreases prolonged QT dispersion in patients with angina pectoris but not in patients with prior myocardial infarction

BACKGROUND AND HYPOTHESIS

Prolonged QT dispersion (QTd) is shortened by successful percutaneous transluminal coronary angioplasty (PTCA) in patients with ischemic heart disease. Particularly, QTd plays an important role in the prognostication in patients with prior myocardial infarction (MI). However, whether the effect of PTCA on QTd differs in patients with and without prior MI is not clear, and this study sought to clarify this question.

METHODS

In 41 consecutive patients with ischemic heart disease, we measured QTd from a routine 12-lead electrocardiogram taken at 72 h before and after successful PTCA. Patients were divided into two groups based on the presence or absence of prior MI: Group 1 consisted of 24 patients with angina (61 +/- 11 years old) without prior MI and Group 2 was comprised of 17 patients (69 +/- 10 years old) with prior MI. QTd was calculated as the difference between the maximum and minimum QT and QT corrected for heart rate (QTc), using Bazett's formula for calculating QTcd. All measurements were obtained manually and blindly.

RESULTS

In Group 1, 15 of 24 patients (63%) demonstrated multivessel disease and 16 of 24 (67%) patients had high QTd > 60 ms. Percutaneous transluminal coronary angioplasty decreased QTd and QTcd in Group 1 (QTd, from 83 +/- 35 to 57 +/- 19 ms, p < 0.05 ; QTcd, from 89 +/- 37 to 63 +/- 33 ms, p < 0.05), whereas no changes were observed in Group 2 (QTd, from 73 +/- 25 to 69 +/- 22 ms, NS; QTcd, from 80 +/- 30 to 79 +/- 28 ms, NS). QTd is more sensitive to decrease by successful PTCA in patients with angina than in patients with prior MI.

CONCLUSIONS

The effect of successful PTCA on inhomogeneity of ventricular repolarization reflected by QTd in patients with prior MI is different from that in patients without prior MI.

Effect of balloon inflation-induced acute ischemia on QT dispersion during percutaneous transluminal coronary angioplasty

BACKGROUND

QT dispersion (QTd = QTmax-QTmin) measured as interlead variability of QT interval reflects the spatial inhomogeneity of ventricular repolarization times, and increased QTd may provide a substrate for malignant ventricular arrhythmias. Ischemia is associated with regional abnormalities of conduction and repolarization.

HYPOTHESIS

This study aimed to investigate the effect of acute ischemia on QTd during successful percutaneous transluminal coronary angioplasty (PTCA).

METHODS

Forty-three patients (10 women, 33 men, mean age 56 years) were enrolled in the study. Electrocardiogram (ECG) recordings were taken before PTCA and during balloon inflation period. QT maximum (QTmax), QT minimum (QTmin), and QTd (QTmax-QTmin) values were calculated from the surface ECG.

RESULTS

There was no difference among QTmax values (p = 0.6). Mean QTmin during balloon inflation was lower than before PTCA (368 +/- 45 vs. 380 +/- 41 ms, p = 0.002). The difference between QTd values before and during balloon inflation was statistically important (65 +/- 9 vs. 76 +/- 10 ms, p = 0.001). This difference is caused by a decrease in QTmin during balloon inflation.

CONCLUSION

Acute reversible myocardial ischemia induced by balloon inflation causes an increase in QTd value, and this increment is the result of a decrease in QTmin interval. Therefore, QTd may be a marker of reversible myocardial ischemia.

Laparoscopic surgery: does it increase the probability of atrial and ventricular arrhythmias in children?

PURPOSE

Despite the minor physiologic changes those occur during laparoscopic procedures, pneumoperitoneum with CO2 insufflation may induce alterations in electrocardiographic (ECG) variables, which may predict severe atrial and ventricular arrhythmias. This study aims to assess QT dispersion (QTD) and P wave dispersion (PWD) changes in children who have undergone laparoscopic appendectomy.

PATIENTS AND METHODS

Sixteen patients (12 males and 4 females) who had preoperative diagnosis of appendicitis were included in the study. As laparoscopic exploration revealed appendicitis in all patients, laparoscopic appendectomy was performed. Preinsufflation (ECG1), postinsufflation (ECG2), predesufflation (ECG3), and postdesufflation (ECG4) ECGs were achieved at a speed of 25 mm/s for QTD and PWD analyses.

RESULTS

Although mean corrected QTD and PWD at ECG2 and ECG3 were significantly greater than ECG1 and ECG4, those changes induced by insufflation of CO2 were reversible.

CONCLUSIONS

The clinical significance of pneumoperitoneum, which causes an increase in corrected QTD and PWD in children, remains to be determined with further studies.

Torsades de pointes related to transient marked QT prolongation following successful emergent percutaneous coronary intervention for acute coronary syndrome

We report 2 patients in whom transient marked QT prolongation occurred after successful emergent percutaneous coronary intervention (PCI) for acute coronary syndrome. One patient developed torsades de pointes. In both cases, the QT interval became markedly prolonged within 24 hours after PCI, and this prolongation persisted for 4 days. The T waves had a giant and bizarre negative shape with a prolonged T-wave peak to T-wave end interval. No new-onset ischemia or congenital long QT syndrome was related to the episodes. The patients had not taken any drugs that could have prolonged the QT interval, and their serum potassium levels were within normal limits. Torsades de pointes following successful PCI for acute coronary syndrome is uncommon, but acquired long QT syndrome should be considered and treated in patients in whom giant and bizarre negative T waves and QT prolongation develop after PCI.

Surgery for myocardial salvage in acute myocardial infarction and acute coronary syndromes

This article addresses the pathophysiology, the treatment options, and their rationale in the setting of life-threatening acute myocardial infarction and acute on chronic ischemia. Although biases may exist between cardiologists and surgeons, with this review, we hope to provide the reader with information that will shed light on the options that best suit the individual patient in a given set of circumstances.

Changes in QT dispersion after thrombolysis for stroke

BACKGROUND

QT dispersion (QTD) reflects heterogeneity of myocardial repolarization, which is modulated by the central nervous system. Although largely studied in patients with cardiovascular disease, QTD is increased in acute stroke and this finding is an independent predictor of functional outcome and mortality following acute neurological events.

HYPOTHESIS

The hypothesis of this study was to determine whether changes in QTD in patients presenting with ischemic stroke parallel changes in neurologic function.

METHODS

We retrospectively studied 30 consecutive patients (76+/-9 years, 50% male) who received thrombolytic therapy for acute ischemic stroke between September 1996 and August 2002, and had multiple electrocardiograms (ECGs). QTD was calculated from the admission ECG and the last available ECG (median 3 days) during hospital admission as the absolute difference between the maximum and minimum QT intervals in at least 11 of 12 leads. The National Institute of Health Stroke Scale (NIHSS) was used to assess neurological status on admission and discharge. DeltaQTD was calculated as the absolute difference between QTD measured on admission and on the last available ECG. Absolute changes in heart rate corrected QTD (DeltaQTDc) and NIHSS scores (DeltaNIHSS) were also calculated.

RESULTS

DeltaQTD was significantly higher in the 27% of patients who died as compared to the survivors (44+/-26 ms vs. -2+/-21 ms, p<.001). DeltaNIHSS correlated directly with DeltaQTD (r=0.57, p<0.001) and with DeltaQTDc (r=0.60, p<0.001). The NIHSS score changed in the same direction 3.1 units (95% CI: 2.0, 4.2) for every 10 ms change in QTD.

CONCLUSION

DeltaQTD are associated with changes in neurological function in patients treated with thrombolytic therapy for acute ischemic stroke.

Evaluation of serial QT dispersion in patients with first non-Q-wave myocardial infarction: relation to the severity of underlying coronary artery disease

BACKGROUND

Increased QT dispersion (QTD) has been correlated with ventricular arrhythmias. Recent reports suggest that it may serve as a marker of the severity of underlying coronary artery disease (CAD).

HYPOTHESIS

The aim of this study was to examine in-hospital changes of QTD and their possible correlation with the severity of underlying CAD in patients with first non-Q-wave myocardial infarction.

METHODS

In 62 patients we estimated QTD, precordial QTD, as well as their values corrected for heart rate on Days 3 and 7 after admission. The severity of underlying ischemic burden was estimated by means of the number of diseased vessels as well as by the jeopardy score.

RESULTS

On Day 3, patients with jeopardy score > or = 6 exhibited greater QTD, corrected QTD, precordial QTD, and corrected precordial QTD (p = 0.001, p = 0.003, p = 0.02, p = 0.036, respectively); patients with multivessel disease had greater QTD (p = 0.007). On Day 7, patients with jeopardy score > or = 6 and multivessel disease exhibited greater QTD, corrected QTD, precordial QTD, and corrected precordial QTD (p < 0.001 for all). Multiple regression analysis revealed a jeopardy score of > or = 6 as the most significant independent predictor for QTD variables. From Days 3 to 7, only patients with none or one diseased vessel orjeopardy score < 6 had shortened QTD (p = 0.01 and p = 0.015, respectively) and corrected QTD (p < 0.001 for both).

CONCLUSIONS

In patients with first non-Q-wave myocardial infarction, QTD variables and their in-hospital changes reflect the severity of underlying CAD.

QT-interval dispersion in acute myocardial infarction is only shortened by thrombolysis in myocardial infarction grade 2/3 reperfusion

BACKGROUND

Increased QT interval dispersion (QTd) has been found in patients with acute myocardial infarction (AMI). In previous studies this has been shown to decrease with thrombolysis.

HYPOTHESIS

The aim of this study was to compare the effects of reperfusion by primary percutaneous transluminal coronary angioplasty (PTCA) and by thrombolysis on QTd and correlate these results with the degree of reperfusion.

METHODS

We studied 60 patients with a first AMI. The study cohort included 40 consecutive patients who had received thrombolysis (streptokinase or rt-PA); 20 additional consecutive patients with successful primary PTCA, all with preselected Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow by predefined selection criteria (12 stents); and 20 controls. A 12-lead ECG for QTd calculation was recorded before thrombolysis or PTCA and immediately after the procedure. All values were corrected according to Bazett's formula (QTcd). QTd and QTcd values before and after each procedure in three groups and the respective percent changes of deltaQTd and deltaQTcd were compared separately.

RESULTS

QTd and QTcd were significantly increased before thrombolysis/PTCA versus normals. An angiogram performed after thrombolysis showed adequate reperfusion (TIMI grade 2/3) in 20 patients, while in the other 20 only TIMI 0/1 reperfusion was achieved. Thrombolysis-TIMI flow 2/3 and PTCA significantly reduced QTd (from 68 +/- 10 to 35 +/- 8 ms, p < 0.001, deltaQTd = 48 +/- 11%, in the Thr-TIMI flow 2/3 group,and from 79 +/- 11 to 38 +/- 9 ms, p < 0.001, deltaQTd = 52 +/- 9%, in the PTCA group), while in the Thr-TIMI flow 0/1 group no significant changes were recorded. A percent QTd decrease > 30 s had 96% sensitivity, 85% specificity, and 93% positive and 94% negative predictive value, respectively, for TIMI 2/3 flow.

CONCLUSIONS

A significant decrease in QT dispersion may provide an additional electrocardiographic index for successful (TIMI 2/3) reperfusion.

QT dispersion and viable myocardium in patients with prior myocardial infarction and severe left ventricular dysfunction

BACKGROUND

QT dispersion (QTd) has been found to correlate to the amount of viable myocardium in patients with Q-wave myocardial infarction and well-preserved LV function. However, this relationship is unknown in patients with severe left ventricular dysfunction.

METHODS

Thirty-four patients with prior large myocardial infarction and severe left ventricular dysfunction underwent Tc-99m sestamibi single photon emission cardiac tomography (SPECT) and F-18 fluorodeoxyglucose (FDG) SPECT. Viability was defined as a defect relative count density (DCD) of at least 20% greater on FDG SPECT. QTd, corrected QT dispersion (QTcd), and QT coefficient of variation (cv) in patients with viable myocardium was compared to those without viable myocardium in the infarct area.

RESULTS

Thirteen patients were excluded from analysis for poor FDG images or inadequate ECG tracings. Of the remaining patients, 10 (48%) were found to have viability on FDG SPECT. QTd, QTcd, and QTcv in patients with viability were: 58 +/- 22 ms, 61 +/- 23 ms, and 4.81 +/- 1.76%, respectively, which did not differ significantly from those in patients without viability (QTd = 56 +/- 14 ms, QTcd = 70 +/- 16 ms and Qtcv = 5.06 +/- 1.20% [P = NS]). Moreover, neither FDG defect size, nor LVEF correlated with QTd.

CONCLUSIONS

This study indicates no relationship between QTd and viability in patients with myocardial infarction and severe left ventricular dysfunction.

The immediate and short-term effect of successful percutaneous coronary intervention on repolarization in acute myocardial infarction patients

OBJECTIVES

The primary objective was to assess the immediate and short-term impact of successful percutaneous coronary intervention (PCI) on QT dispersion (QT disp) and corrected QT dispersion (QTc disp). Secondarily, the impact of PCI on QT and QTc disp within different infarct-related arteries and the impact of successful PCI in these different arteries were evaluated.

METHODS

Patients (n = 140, age 61.6 +/- 12.9, 69% male) undergoing direct primary PCI for acute MI were evaluated. Twelve-lead ECGs were obtained before (baseline), immediately after (0 h), 24hours after, and 3 days after PCI. The QT and QTc interval in each of the 12-leads were measured and the shortest interval was subtracted from the longest to derive the QT disp and QTc disp, respectively.

RESULTS

Angiography showed blockages in the left anterior descending, right coronary artery, and circumflex in 37.1, 48.9, and 15.0% of patients, respectively. Overall, 97 patients achieved successful reflow. QT and QTc disp were significantly improved in the group with successful reflow at each follow-up time after PCI versus baseline and corresponding values in the unsuccessful reflow group. QT disp was improved among patients with successful reflow irrespective of which infarct artery was responsible for the acute myocardial infarction.

CONCLUSIONS

Successful reflow with PCI is associated with a rapid reduction in QT disp and QTc disp that is maintained for at least 3 days after the event. Conversely, unsuccessful reflow was not associated with significant reductions in QT or QTc disp.

QT dispersion and left ventricular function after stent placement in acute myocardial infarction

BACKGROUND

QT dispersion is increased in acute myocardial infarction (AMI), but the relation of QT dispersion to left ventricular (LV) function has not yet been fully elucidated. The purpose of this study was to evaluate the relationship between QT dispersion and LV function in patients with successful coronary stenting in AMI.

METHODS

Seventy five patients with AMI who underwent percutaneous transluminal coronary angioplasty (PTCA) were enrolled in this study. Corrected QT dispersion was measured before, immediately after, 24 h after, 48 h after, and 6 months after PTCA. Left ventricular ejection fraction (LVEF) was evaluated by left ventriculography at 6 months after PTCA.

RESULTS

Corrected QT dispersion at 24 h after and 48 h after PTCA were significantly related to LVEF by univariate analysis (r=-0.282, p<0.05 and r=-0.326, p<0.01, respectively). In multiple regression model, corrected QT dispersion at 24 h after and 48 h after PTCA revealed significant associations with LVEF (R(2)=0.441, coefficient=-0.283, p=0.006 and R(2)=0.411, coefficient=-0.225, p=0.039, respectively), but corrected QT dispersion before, immediately after, and 6 months after PTCA were not associated with LVEF.

CONCLUSIONS

Corrected QT dispersion at 24 h after and 48 h after PTCA in AMI correlate with LVEF at 6 months after PTCA.

The association of QT dispersion and QT dispersion ratio with extent and severity of coronary artery disease

BACKGROUND

Although prolongation of the QT intervals in acute ischemic conditions, such as acute myocardial infarction, intracoronary balloon inflation, and exercise induced ischemia, has been shown, association of rest QT intervals with extent and severity of stable coronary artery disease (CAD) has not been assessed so far. The effects of extent and severity of stable CAD on rest QT interval were analyzed in this study.

METHODS

Rest 12-lead electrocardiograms (ECG) were recorded in 162 clinically stable subjects undergoing coronary angiography before the angiography for measurement of corrected QT dispersion (cQTd) and the QT dispersion ratio (QTdR) defined as QT dispersion divided by cycle length and expressed as a percentage. Angiographic "vessel score,""diffuse score," and "Gensini score" were used to evaluate the extent and severity of coronary atherosclerosis. Subjects were grouped as follows: those with normal angiogram (Group 1), those with insignificant (<50%) coronary stenosis (Group 2), and those with 1- (Group 3), 2- (Group 4), or 3-vessel disease (Group 5).

RESULTS

cQTd and QTdR were higher in Group 3 compared with Group 1 (P < 0.001 and P = 0.001, respectively), in Group 4 compared with Group 1 (P < 0.001 for both) and Group 2 (P = 0.001 and P = 0.003, respectively), and in Group 5 compared with Group 1 (P < 0.001 for both) and Group 2 (P < 0.001 and P = 0.003, respectively). cQTd and QTdR were positively correlated with the vessel score (r = 0.422, P < 0.001; r = 0.358, P < 0.001, respectively), diffuse score (r = 0.401, P < 0.001; r = 0.357, P < 0.001, respectively) and Gensini score (r = 0.378, P < 0.001; r = 0.373, P < 0.001, respectively). In multiple linear regression analyses, cQTd was found to be independently associated only with diffuse score (beta= 0.325, P = 0.038). Also, QTdR was independently associated with diffuse score (beta= 0.416, P = 0.006) and Gensini score (beta= 0.374, P = 0.011).

CONCLUSIONS

Rest cQTd and QTdR are increased, and related to the extent and severity of coronary atherosclerosis in patients with stable CAD.

QT interval dispersion as a new marker of restenosis after percutaneous transluminal coronary angioplasty of isolated single-vessel coronary artery stenosis

BACKGROUND

There are no reliable non-invasive markers of restenosis after percutaneous transluminal coronary angioplasty (PTCA). The aim of our study was to measure changes in QT interval dispersion after PTCA and to determine whether restenosis subsequently affects QT interval dispersion.

METHODS AND RESULTS

Fifty-six consecutive patients - 41 men and 15 women (mean age: 56.2 +/-8.3 years) - with isolated stenosis of the left anterior descending artery who underwent successful PTCA were studied. A symptom-limited treadmill exercise test was performed within 7 days after PTCA and then again before repeated angiography. Repeated coronary angiography revealed restenosis in 15 patients (26.8%) and no signs of significant stenosis in 41 patients (73.2%). QT interval dispersion in the group of patients with restenosis measured before exercise increased from baseline 34 +/- 7 to 49 +/- 15 ms after 6 months (p < 0.01) and QT interval dispersion measured immediately after exercise increased from baseline 38 +/- 4 to 68 +/- 21 ms after 6 months (p < 0.001). In contrast, patients without restenosis showed no significant changes in QT interval dispersion measured before (baseline: 34 +/- 9 ms; after 6 months 33 +/- 12 ms; p = NS) and immediately after exercise (baseline: 34 +/- 12 ms; after 6 months: 33 +/- 10; p = NS). When QT interval dispersion > or =60 ms (measured 6 months after PTCA procedure) was considered as a potential marker of restenosis, this indicator had very high sensitivity and specificity when measured immediately after exercise (80 and 95% respectively).

CONCLUSIONS

QT interval dispersion significantly increases in the group of patients with documented restenosis and may be a simple, non-invasive marker of restenosis. However, further studies are needed to confirm this observation.

QT peak dispersion, not QT dispersion, is a more useful diagnostic marker for detecting exercise-induced myocardial ischemia

BACKGROUND

The electrocardiographic indices of QT dispersion (QTd), QT peak dispersion (QTpd), and the principal component analysis ratio (PCAr) are related to the occurrence of fatal arrhythmia and are influenced by physical exercise.

OBJECTIVE

The purpose of this study was to investigate whether or not the QT parameters can be used as markers for exercise-induced myocardial ischemia.

METHODS

We measured these QT parameters at rest and at 3 minutes after exercise using exercise-stress thallium-201 scintigraphy (SPECT), compared with conventional ST segment changes in 161 patients with suspected or known coronary artery disease. The patients were classified into four groups (normal, redistribution, fixed defect, and redistribution with fixed defect) according to SPECT.

RESULTS

At rest, QTd and PCAr were greater in the fixed defect and redistribution with fixed defect groups. PCAr, however, increased after exercise in the redistribution and redistribution with fixed defect groups. Although QTpd at rest was not significantly different among the four groups, it increased in the redistribution and redistribution with fixed defect groups after exercise (QTpd after exercise: normal, 36 +/- 16 ms vs. redistribution, 51 +/- 23 ms, redistribution with fixed defect, 53 +/- 19 ms; P<.05). For myocardial infarction reflected by fixed defect, QTd at rest was the most useful indicator, while QTpd after exercise was the most useful indicator for exercise-induced myocardial ischemia according to multiple logistic regression analysis with receiver operating characteristic curves. In addition, the change in PCAr by exercise was an independent predictor for exercise-induced ischemia.

CONCLUSIONS

QTpd and PCAr could be useful indices for exercise-induced myocardial ischemia. Determining the QTpd of a patient after exercising can improve the diagnostic accuracy of ischemia in a routine clinical setting.

Effects of coronary revascularization and concomitant aneurysmectomy on QT interval duration and dispersion

A reduction in QT dispersion (QTd) has been previously shown in patients receiving thrombolytics and undergoing coronary artery bypass grafting (CABG). The purpose of the present study was to investigate changes occurring in corrected QT intervals or QT dispersion after CABG and concomitant aneurysmectomy in the same session. The study population included 43 patients with coronary artery disease with left ventricular aneurysm (LVA). The control group included 32 patients with coronary artery disease without LVA. The study patients underwent CABG and aneurysmectomy in the same surgical session. Corrected maximum and minimum QT interval duration (QTcmax and QTcmin) and corrected QT dispersion (QTcd) were measured in the study patients before and after surgery. QTcmax and QTcd in the patients with LVA were significantly higher than in the patients without LVA (P < .001 and P < .001, respectively). QTcmax and QTcd in the patients with LVA were significantly shortened after surgery (P < .001 and P < .001, respectively). This study showed that QTcmax and QTcd values are significantly reduced after CABG and concomitant aneurysmectomy. We have suggested that coronary revascularization and left ventricular reconstruction in the same session have beneficial effects on QT interval duration and dispersion.

Effect of percutaneous coronary intervention of nonacute total coronary artery occlusions on QT dispersion

BACKGROUND

Myocardial ischemia is one of several potential causes of increased QT dispersion (QTd) in patients with nonacute total coronary artery occlusions (TCOs). We sought to assess the effect of percutaneous revascularization (PCI) of TCO on QTd and the relationship between QTd and long-term vessel patency.

METHODS

Seventy patients enrolled in the TOSCA were analyzed. Patients were undergoing PCI of a TCO > 72 hours' duration. Two independent reviewers measured QTd from electrocardiograms done immediately before PCI (PRE), 12 to 18 hours after PCI (POST), and then at 6 months (6M). Follow-up angiography was performed at 6 months.

RESULTS

Mean QTd decreased from PRE (77 +/- 29 milliseconds) to POST (66 +/- 26 milliseconds, P < .001) and 6M (65 +/- 25 milliseconds, P < .001). Patients with the same or longer QTd at 6 months compared with POST (POST < or = 6M) had significantly higher risk of failed target-vessel patency (odds ratio 10.3, 95% CI 1.24-84.8) than patients with QTd reduction at 6M versus POST values.

CONCLUSION

Revascularization of TCO resulted in a decrease in QTd, which was sustained at 6M. This suggests that PCI to a TCO has a beneficial effect on stabilization of the underlying ischemic substrate. Furthermore, absence of QTd reduction at 6M versus POST was associated with increased risk of failed target-vessel patency.

QT dispersion is determined by the relative extent of normal, hibernating, and scarred myocardium in patients with chronic ischemic cardiomyopathy. A dobutamine stress echocardiography study before and after surgical revascularization

INTRODUCTION

The aim of the present study was to evaluate a possible association between QT dispersion (QTd) and the amount of viable and scarred myocardial tissue after revascularization in patients with coronary artery disease and impaired left ventricular (LV) function.

METHODS

Twenty-two patients with ischemic LV dysfunction underwent dobutamine stress echocardiography (DSE) before and 6 months after surgical revascularization. Mean corrected QT-interval value and QTd were calculated at baseline and follow-up. Segments consisting of transmural scar were determined as the segments that remained akinetic in all stages of DSE despite reperfusion. Patients were divided into 2 groups according to the number of definitive segments consisting of transmural scar (minor scar group, < or =2 scarred segments; major scar group, >2 scarred segments).

RESULTS

QTd was significantly lower in the minor compared with the major scar group at baseline and follow-up (mean [SD], 61 [22] vs 98 [33] milliseconds, P = .008, and 45 [18] vs 68 [21] milliseconds, P = .01, respectively). Segments consisting of transmural scar positively correlated to QTd at baseline (r = 0.53, P = .01) and follow-up (r = 0.62, P = .002).

CONCLUSIONS

QTd is positively correlated with the extent of scarred myocardial tissue assessed by DSE. Surgical revascularization results in reduction of QTd in all patients with hibernating myocardium and LV dysfunction.

Change with exercise in QT dispersion in infarct-related myocardium after angioplasty

BACKGROUND

The aim of this study was to evaluate the relationship between exercise-induced QT dispersion and condition of infarct-related myocardium including myocardial scar after angioplasty assessed with exercise perfusion single photon emission computed tomography (SPECT).

METHODS

Exercise thallium-201 SPECT was performed 6 months after successful direct angioplasty in 67 male patients (60.6 +/- 11.5 years), who had Q wave infarction resulting from single vessel disease, and the number of perfusion defect areas (DS) was measured at rest and exercise together with QT (QTc) dispersion.

RESULTS

In 52 patients with resting perfusion defects, the exercise-induced change in DS was correlated to the change in QT (or QTc) dispersion (r = -0.51 or r = -0.531, p < 0.0001). When the patients were grouped according to the patterns of transient perfusion defect, there were significant differences in DeltaQT dispersion and DeltaQTc dispersion among infarct-related three groups (reverse, fixed, and partial redistributions) and normal volunteers (DeltaQT dispersion; -5.7 +/- 12.7 ms in 13 patients with reverse redistribution, -16.3 +/- 13.1 ms in 30 patients with fixed redistribution, -28.9 +/- 29.5 ms in 9 patients with partial redistribution, and +3.4 +/- 20.9 ms in 12 normal volunteers, p = 0.0098; DeltaQTc dispersion; +18.2 +/- 20.8 ms, +1.4 +/- 16.7 ms, -15.4 +/- 30 ms, and +19 +/- 27.5 ms, p = 0.0017, respectively). DeltaQTc dispersion estimated the SPECT image patterns (p = 0.0002) with a sensitivity of 67.3%, a specificity of 83.7% and an accuracy of 78.2%.

CONCLUSIONS

The change with exercise in QT dispersion may help detect the condition of infarct-related myocardium after angioplasty.

Effects of reperfusion obtained two to six months after acute myocardial infarction on myocardial electrical stabilization in patients with an occluded infarct-related coronary artery

To assess the changes in electrical stability markers in patients with previous myocardial infarction after very late reopening of the infarct-related artery, we studied QT dispersion, corrected-QT dispersion, and late potentials before and 1, 3, and 6 months after an attempt at late percutaneous coronary intervention (PCI) in 31 consecutive patients with single-vessel disease (infarct-related artery occlusion or subocclusion) diagnosed > or = 4 weeks after the ST-elevation myocardial infarction. Patients underwent PCI 3.9 +/- 2 months after ST-elevation myocardial infarction. PCI was successful in 24 patients (group A) and unsuccessful in 7 (group B). The 2 groups were similar in clinical and angiographic characteristics, as well as the prevalence of basal late potentials, average QT dispersion, and corrected-QT dispersion. One month after PCI, the successful reperfusion group had a significant 67% decrease in the prevalence of late potentials and average QT dispersion and corrected QT dispersion (51 +/- 9 vs 72 +/- 11 ms, p <0.00001, and 51 +/- 10 vs 76 +/- 15 ms, p <0.00001, respectively). These benefits remained stable at 3 and 6 months after PCI. Conversely, the unsuccessful group did not show any improvement in electrical stability markers after PCI failed. Thus, reperfusion obtained very late after ST-elevation myocardial infarction confers significant electrical stabilization that may contribute to a better outcome in patients with patent infarct-related arteries.

Long term effects of hormone replacement therapy on heart rate variability, QT interval, QT dispersion and frequencies of arrhythmia

BACKGROUND

The aim of the study was to investigate the effects of a long term (1 year) hormone replacement therapy (HRT) on QT interval, QT dispersion (QTd) frequencies of arrhythmia and heart rate variability (HRV) parameters.

METHODS

Forty-six healthy postmenopausal women (mean age; 55.34+/-4.21) as a hormone replacement therapy group and 25 healthy premenopausal women (mean age; 35.36+/-6.06) as a control group were prospectively enrolled to the study. Hormone replacement therapy group was divided into two groups; estrogen replacement therapy (ERT) group (n=23) and progestin-estrogen replacement therapy (PERT) group (n=23). Standard 12 lead electrocardiograms and 24-h ambulatory Holter recording were obtained to evaluate the effects of one year of ERT and PERT on QT intervals, QTd, frequencies of arrhythmias and HRV parameters.

RESULTS

Long term use of ERT increases QT interval, QTd, in the frequencies of arrhythmia and HRV indexes of parasympathetic activity; however, the increase in frequencies of arrhythmia was not statistically significant (p>0.05). Long term use of PERT did not effected QT interval, QTd, frequencies of ventricular arrhythmia and HRV parameters (p>0.05). Frequency of supraventricular tachycardia increased in post-treatment PERT group was compared with pre-treatment PERT group.

CONCLUSION

These findings supported the hypothesis that estrogen may directly modulate ventricular repolarization. But progestin do not effect the ventricular repolarization. However, these findings must be supported with a large-scale study.

QT dispersion and myocardial viability in patients after acute myocardial infarction

BACKGROUND

In recent years QT dispersion (QTd) in post-infarct patients was estimated in many studies, but still little is known about its association with the presence of dysfunctional but viable myocardium.

AIM

We investigated the relation between dispersion of QT interval and myocardial viability in patients after acute myocardial infarction (AMI).

MATERIAL AND METHODS

In 52 patients (mean age 67.2+/-11.7) treated thrombolytically because of AMI 12-lead ECG and low dose-high dose dobutamine echocardiography was performed on 14th day after treatment. QTd and regional myocardial contractility were estimated three times: at baseline, low dose dobutamine (LDD) (10-15 microg/kg per min) and high dose dobutamine (HDD) infusion (up to 40 microg/kg per min).

RESULTS

Patients with viable myocardium had lower baseline QTd than patients with only necrosis in infarct zone. Significant increase in QTd was shown during LDD and HDD both in patients with and without myocardial viability. During infusion of HDD QTd was significantly higher in patients with myocardial ischemia. The greatest percentage increase of QTd at HDD was shown in patients with biphasic response to dobutamine infusion i.e. with myocardial viability evidenced at LDD and myocardial ischemia at HDD.

CONCLUSION

Patients with preserved myocardial viability had lower QTd values compared to those with similar left ventricular dysfunction but caused only by post-infarction necrosis. Ischemia evoked on 14th day after AMI was accompanied by greater increase in QTd in patients with myocardial viability in infarct region than in patients without. It may be one of the reasons of greater risk of serious ventricular arrhythmias in such patients during myocardial ischemia.

The effect of ST resolution on QT dispersion after interventional treatment in acute myocardial infarction

BACKGROUND

It has been reported that reperfusion treatment reduces QT dispersion (QTD) in cases of acute myocardial infarction (AMI). Successful myocardial perfusion is not synonymous with Thrombolysis in Myocardial Infarction (TIMI) III flow. It has been demonstrated that in AMI, the grade of ST-resolution correlates strongly with left ventricular (LV) function, enzyme elevation, and mortality after primary angioplasty.

HYPOTHESIS

This study investigated the relation between ST-resolution grade and QTD and the feasibility of using QTD as a determinant of successful myocardial tissue perfusion in patients in whom TIMI III flow in the infarct-related artery (IRA) is restored by interventional treatment for AMI.

METHODS

The study included 57 patients (38 men, 19 women, average age 54.4 +/- 11.6 years), whose IRA was perfused by primary angioplasty after the diagnosis of anterior AMI with ST elevation. Electrocardiograms of patients were taken 45 +/- 12 min post procedure, and patients were divided into three groups depending on the grade of ST resolution: Group 1, full ST resolution; Group 2, partial ST resolution; and Group 3, unsuccessful ST resolution.

RESULTS

Full ST resolution was seen in 19 cases (33%), partial resolution in 26 cases (47%), and unsuccessful resolution in 12 cases (20%). There were no differences among groups in terms of risk factors, stent diameters, symptom onset-balloon time, LV function, and preprocedure corrected QTD (QTcD) (p = 0.274). After the procedure, a significant reduction in QTcD was found within the groups (p = 0.0001 in Group 1, p = 0.004 in Group 2, and p = 0.011 in Group 3). Reductions in QTcD post procedure were 24.21 +/- 14.27, 11.85 +/- 16.18, and 12.50 +/- 11.58 ms in Groups 1, 2, and 3, respectively. There was a statistically significant difference of p = 0.015 between Groups 1 and 2 and a difference of p = 0.028 between Groups 1 and 3. There was no statistically significant difference between Groups 2 and 3 (p = 0.916).

CONCLUSION

In acute MI, TIMI III flow led to a reduction in QTcD, and full myocardial perfusion made an additional contribution to the electrical stability of the myocardium.

Correlation between dispersion of repolarization (QT dispersion) and ventricular ectopic beat frequency in patients with acute myocardial infarction: a marker for risk of arrhythmogenesis?

BACKGROUND

QT dispersion (QTd) has evoked a lot of interest in recent years as regards the basic concept of dispersion of repolarization, which it is supposed to reflect on a surface ECG, as being a marker or substrate for arrhythmogenesis. QTd has been shown to be high in patients with ventricular fibrillation and tachycardia. But there is still some debate about its possible role as a marker or substrate for arrhythmogenesis. We studied whether it has any correlation with simple benign ventricular ectopic beats (VEB) after acute myocardial infarction.

STUDY

We studied four different dispersion parameters (QTd, QTcd, JTcd, AQTd) on 2 different days after AMI and also obtained a 24-h ambulatory ECG on the 2nd day after admission in 64 out of a total of 90 patients. Patients were divided into five groups based on VEB frequency/h on a 24-h ambulatory ECG.

RESULTS

We found a gradual increase in dispersion parameters across the five groups with increasing frequency of VEB. A significant difference was noticed between group 1 (VEB 0.0-0.9/h) and group V (>30/h) on the day of admission: QTd 88.8+/-28.5 versus 123.3+/-23.4, P<0.02; QTcd 100.5+/-27.6 versus 160.3+/-30.7, P<0.01; JTcd 95.5+/-31.0 versus 160.4+/-30.9, P<0.01; AQTd 29.6+/-8.2 versus 48.6+/-13.7, P<0.01. We also noticed a significant positive correlation between VEB frequency and dispersion parameters on both days.

CONCLUSION

We hypothesize that with increasing dispersion of repolarization the chances or the frequency of ventricular arrhythmias increase. Our findings also point to a definite role of QTd as an arrhythmogenic marker or substrate.

Relation between QT dispersion and myocardial viability in ischemic cardiomyopathy

The aim of this study was to evaluate the relation between QT dispersion and myocardial viability as assessed by single-photon emission computed tomography. The study population included 97 consecutive patients with severely impaired left ventricular function secondary to chronic coronary artery disease. Patients with a low QT dispersion had a substantial amount of viable myocardium, whereas patients with a high QT dispersion had predominantly nonviable scar tissue.

Spatial distribution of repolarization times in patients with coronary artery disease

The potential clinical value of QT dispersion (QTd), a measure of the interlead range of QT interval duration in the surface 12-lead ECG, remains ambiguous. The aim of the study was the temporal and spatial analysis of the QT interval in healthy subjects and in patients with coronary artery disease (CAD) using magnetocardiography (MCG) and surface ECG. Standard 12-lead ECG and 37-channel MCG were performed in 20 healthy subjects, 23 patients with CAD without prior myocardial infarction (MI), 31 MI patients and 11 MI patients with ventricular tachycardia (VT). QTd was increased in CAD without MI compared to normals (ECG 46.1 +/- 6.0 vs 42.8 +/- 5.0, P < 0.05; MCG 66.8 +/- 20.3 vs 49.7 +/- 10.8, P < 0.01) and in VT compared to MI (ECG 66.8 +/- 16.5 vs 51.9 +/- 16.6, P < 0.05; MCG 93.6 +/- 29.6 vs 66.8 +/- 20.8, P < 0.005). In MCG, spatial distribution of QT intervals in patient groups differed from those in healthy subjects in three ways: (1) greater dispersion, (2) greater local variability, and (3) a change in overall pattern. This was quantified on the basis of smoothness indexes (SI). Normalized SI was higher in CAD without MI compared to normals (3.8 +/- 1.1 vs 2.7 +/- 0.6, P < 0.001) and in VT compared to MI (6.4 +/- 1.6 vs 4.2 +/- 1.4, P < 0.0005). For the normal-CAD comparison a sensitivity of 74% and a specificity of 80% was obtained, for MI-VT, 100% and 77%, respectively. The results suggest that examining the spatial interlead variability in multichannel MCG may aid in the initial identification of CAD patients with unimpaired left ventricular function and the identification of post-MI patients with augmented risk for VT.