Depolarization, Repolarization Inhomogeneity and Late Potential after Surgical Repair of Tetralogy of Fallot

PURPOSE: After repair of tetralogy of Fallot(TOF), ventricular arrhythmia and sudden death remain as serious late complications which are due to right ventricular systolic and diastolic overloading, exposure to hypoxia and surgical scar. Among the various methods for predicting the risk of such complications, we evaluated signal average ECG(SAECG), QRS duration, QT and JT dispersion, cardiothoracic(CT) ratio, age at repair and follow-up duration. METHODS: Patients were divided into 3 groups : repaired TOF patients(group 1, n=22), patients with complete right bundle branch block(CRBBB) after ventricular septal defect and/or atrial septal defect repair(group 2, n=16) and normal controls(group 3, n=13). There were no significant differences in mean age at presentation, mean age at repair, or at mean follow up among the 3 groups. RESULTS: QRS duration was significantly prolonged in group 1 and 2(121+/-29ms, 119+/-17ms, respectively) compared to group 3(81+/-4ms)(P<0.01). In group 1, QRS duration showed significant positive correlations with age at repair(r=0.43, P<0.05) and follow-up duration(r=0.46, P<0.05). QT dispersion was significantly increased in group 1 and 2(88+/-38ms, 71+/-27ms, respectively) compared to group 3(37+/-20ms)(P<0.01). JT dispersion showed significant differences among groups, being 96+/-38ms in group 1, 68+/-25ms in group 2, 44+/-18ms in group 3(group 1 vs 2 : P<0.05, group 2 vs 3 : P<0.05, group 1 vs 3 : P<0.01). CT ratio was significantly increased in group 1(59+/-6%) compared to group 2 and 3(50+/-3%, 50+/-2%, respectively)(P<0.01). There were no significant differences in parameters of SAECG among the 3 groups. CONCLUSION: We concluded that abnormality of JT dispersion, in repaired TOF pateints indicating inhomogeneity of repolarization, can be a cause of ventricular arrhythmia.

Effect of Coronary Angioplasty on QT and JT Dispersion

BACKGROUND: QT dispersion, reflecting inhomogenous ventricular repolarization, increases in myocardial ischemia. In addition, Many studies reported that prolonged QT dispersion reduced to normal after reperfusion treatment. We have carried out this study to evaluate the QT and JT dispersion before and after the angioplasty in patients with coronary artery diseases. METHOD AND MATERIALS: Seventy-two patients (55 men and 17 women:18 acute myocardial infarction, 9 unstable angina and 45 stable angina) who underwent percutaneous transluminal coronary angioplasty were evaluated. Standard 12-lead electrocardiograms were recorded 24 hours before and 24 hours after angioplasty at a paper speed of 25 mm/sec. RESULTS: There was no significant change in heart rate or the maximum or minimum QT interval after angioplasty. QT dispersion significantly decreased after angioplasty (p<0.05). And QTc dispersion (QTcd) also similary reduced (p<0.01). JT dispersion (JTc) and JTc dispersion (JTcd) were not changed significantly. There were significant reduction in QTd and QTcd in the group of patients without acute myocardial infarction (p=0.005, 0.004, respectively) but not in JTd and JTcd. However, in patients with acute myocardial infarction, all four dispersion were not reduced significantly. And in patients with multivessel angioplasty, there were significant reduction of QTd, QTcd, JTd and JTcd (p=0.016, 0.014, 0.036, 0.030, respectively). CONCLUSIONS: As changes in QT and JT dispersion reflect successful reperfusion by angioplasty, they can be accepted as promising test for assessing the effectiveness of angioplasty clinically. However the methodology still has several unresolved issues and larger, prospective clinical studies are needed.

Diagnostic Value of QT and JT Dispersion in Exercise ECG

BACKGROUND: QT dispersion(QTD : QTmax-QTmin) or JT dispersion(JTD:JTmax-JT-min)in 12 leads ECG has been known to reflect regional variations in ventricular repolarization and has been reported to bel one of the marker of regional myocardial ischemia. To evaluate the significance of QTD or JTD of exercise ECG in diagnosis of coronary artery disease, we studied 106 patients(mean age, 56.9 years old, male 63) who were referred for the evaluation of chest pain on exertion. METHOD: Treadmill exercise stress test with modified Bruce protocol and coronary angiography were performed in 106 patients with chest pain on exertion. ST-segment depression by >1.0 mm 0.08 second after J-point during or after exercise in exercise test and >50% stanosis of epicardial artery in coronary angiogram were defined as positive. Of 106 patients, 41 had positive exercise ECG and positive coronary angiogram(true positive, TP), 20 had positive exercise ECG and negative coronary angiogram(false positive, FT), 20 had negative exercise ECG and positive coronary angiogram(faalse negative, FN), and 23 had negative exercise ECG and negative coronary angiogram(true negative, Tn). QT and JT interval in 12 leads were measured at baseline and peakexercise and were corrected for heart rate using Bazett's formula. QTD and JTD were measured by calculation the difference between the maximum QT and mininum QT and that between maximum JT and minumum JT. RESULTS: QTD at baseline for TP(72.8ms)was prolonged compared to Tn(52.2ms,P<0.01), but was not different from that for FT(70.2 ms). At peak exercise, QTD for TP(81.3 msec) was significantly prolonged(p<0.01), while QTD for FP(71.2 msec) was not different from that for TN(56.8 msec). JTD at baseline(78.4 msec) and at peak exercise(88.2 msec) for TP were significantly prolonged compared to those for TN(55.2msec and 55.1msec p<0.01,p<0.01, respectively), but those for FP were not porlonged(77.0msec and 79.0msec, respectively). QTD and JTD at peak exercise were more markedly prolonged in patients with sever stenosis of coronary artery(p=0.053 and p<0.05, repectively) and multivessels diseases(p<0.01, 0<0.05) than those with less severe disease and single vessel disease. Patients with left anterior descending artery lesion had greater QTD and JTD at peak exercise than those with other vessels lesion(p<0.01). In addition to standard criteria with ST segment displacement in exercise EGC, inclusion of exercise induced QTD of more than 60msec increased the sensitivity of exercise ECG from 66.7% to 83.3%, and JTD of more than 70msec increased the specificity from 52% to 76.0%. CONCLUSION: Measurement of QT dispersion and JT dispersion of exercise ECG may be useful method to identify the severity of coronary artery disease and to improve diagnostic accuracy of exercise ECG in coronary artery disease.