Effect of coronary artery bypass grafting and aneurysmectomy on QT dispersion in moderate or severe left ventricular dysfunction

Impact of cardiac rehabilitation on ventricular repolarization indices following coronary artery bypass grafting

Background

The aim of this study was to evaluate the effect of cardiac rehabilitation on electrocardiographic changes in patients undergoing isolated coronary artery bypass grafting.

Methods

Between January 2016 and July 2019, a total of 625 patients (485 males, 140 females; mean age: 59.6 years; range, 50.6 to 68.6 years) who underwent isolated coronary artery bypass grafting and survived were retrospectively analyzed. The patients were divided into two groups according to the participation in the cardiac rehabilitation program as follows: the Rehab(+) group (n=363) and the Rehab(-) group (n=262). Electrocardiographic parameters of both groups were compared.

Results

There was a significant decrease in the electrocardiographic findings of heart rate (p<0.001), QTc (p<0.001), Tpe duration (p<0.001), Tpe/QT ratio (p<0.001), and Tpe/QTc ratio (p<0.001) in the Rehab(+) group before and after surgery. There was a significant decrease in the Rehab(+) group, compared to the Rehab(-) group, in terms of parameters of QT interval (p=0.001), QTc (p=0.017), Tpe duration (p<0.001), Tpe/QT ratio (p<0.001), and Tpe/QTc ratio (p<0.001).

Conclusion

Cardiac rehabilitation program after coronary artery bypass grafting decreases ventricular repolarization indices of electrocardiography. Based on these changes, postoperative cardiac rehabilitation program may reduce the risk of ventricular arrhythmia and sudden cardiac death during follow-up.

QT dispersion before and after coronary artery angioplasty: a case study from Iran

AIM

In this study, we investigated the changes in QT dispersion (QTd) after successful coronary artery revascularization.

BACKGROUND

QTd, as a marker of regional variability of myocardial repolarization, increases following impaired myocardial perfusion and is associated with increased risk of ischemia-induced arrhythmia.

METHODS

In 45 consecutive patients (mean age 54.39±11.49 years) undergoing elective percutaneous coronary intervention (PCI), QTd was measured from a 12-lead electrocardiogram 6-12 hours before and 6 hours after the procedure. QTd was defined as the difference between maximum and minimum QT interval in the 12 leads. QT changes were analyzed regarding preoperative ejection fraction (EF), type and number of involved vessels, type and number of revascularized coronary arteries and history of Q-wave MI using SPSS software.

RESULTS

QTd significantly decreased postoperatively from 55.48±20.03 to 42.00±19.96 in the study population (P=0.001). Subgroup analyses showed that QTd did not decrease significantly in patients with two-vessel disease and those with low EF (<50%); however, the reduction was significant for other subgroups.

CONCLUSION

Successful PCI results in improved regional heterogeneity of myocardial repolarization, evidenced as decreased QTd after the procedure.

Elevated temporal lability of myocardial repolarization after coronary artery bypass grafting

INTRODUCTION

Ventricular arrhythmias are uncommon after coronary artery bypass grafting (CABG), but the incidence and mortality are high in certain subsets of patients during the early recovery after surgery. Elevated temporal lability of myocardial repolarization has been associated with sudden cardiac death. The aim of the current study was to explore temporal variability of myocardial repolarization during both early and longtime follow-up after CABG.

METHODS AND RESULTS

Patients (n = 61) who had undergone CABG and healthy subjects (HS, n = 33) were examined. Electrocardiogram and beat-to-beat blood pressure were recorded at 5 weeks and 5 months after surgery. The QT variability index (QTVI) was calculated as the log ratio between the temporal variabilities of the QT and RR intervals. The QTVI and QT variances were elevated by 40% and 44%, whereas RR variances were reduced by 40% among patients 5 weeks after CABG compared to HS (-0.90 +/- 0.59, 29 +/- 30, and 1223 +/- 1895 ms(2) vs -1.50 +/- 0.29, 15 +/- 16, and 2200 +/- 2877 ms(2) for HS; P < .01 for all). The QTVI and QT variances decreased by 38% and 31% between 5 weeks and 5 months after CABG, whereas the RR variances increased by 51% (P < .01 for all). The QTVI values remained elevated among patients compared to HS at 5 months after CABG (P < .01), whereas QT and RR variances did not differ.

CONCLUSION

Elevated temporal lability of myocardial repolarization prevails particularly during the early recovery phase after CABG and may reflect increased susceptibility to ventricular arrhythmia.