Effects of rehabilitation on QT dispersion and double product in patients after coronary artery bypass graft surgery and reduced left ventricular ejection fraction: is there age difference?
V Stoickov, I Tasic, S Kostic, D Marinkovic, D Simonovic, F Stoickov, I StoickovAbstract
Background/Introduction
Patients after coronary artery bypass graft surgery (CABG) are at risk of new cardiovascular and arrhythmic events. QT dispersion is a measure of inhomogeneous repolarization of myocardium and it is used as an indicator of arrhythmogenicity.
Purpose
The aim of this study was to establish the influence of cardiovascular rehabilitation (CR) on QTd and double product (DP) in patients after CABG and reduced left ventricular ejection fraction (RLVEF ≤ 40%) and the impact of age on the benefit.
Methods
The study involved 143 patients after CABG and RLVEF, in the sinus rhythm without AV blocks or branch blocks. Average age of patients was 56.7 years. In relation to age, patients were divided into two groups: A (n=79, <60 years) and B (n=64, ≥ 60 years). In all patients clinical examination, echocardiographic examination, standard ECG and exercise test on treadmill according to Bruce protocol, were performed and after that patients were included in the program of CR for three weeks. Patients were instructed to follow a CR program using the bicycle ergometer (10 min, 2 times a day), gymnastic exercises and walking. The patients continued to take the same medicaments in same doses. After CR, patients performed a second exercise test. From standard ECG corrected QT dispersion (QTdc) was calculated.
Results
Before starting with the program of CR, patients in group A had significantly lower values of QTdc (58.3 ± 17.2 vs 66.1 ± 21.6 ms; p<0.02) and DP (11875.4 ± 1223.4 vs 12503.2 ± 1396.8 beat/min x mmHg; p<0.005), and achieved a significantly longer time on the first exercise test (p<0.005) compared to group B. After CR, significant reduction of QTdc was found (from 58.3 ± 17.2 to 52.9 ± 15.9 ms; p<0.05) in group A, while no significant difference was found in group B (P- NS). After CR, significant reduction of DP was found in group A (from 11875.4 ± 1223.4 to 10693.8 ± 1198.6 beat/min x mmHg; p<0.001) and group B (from 12503.2 ± 1396.8 to 11893.1 ± 1275.8 beat/min x mmHg; p<0.01). After CR, we have found significant reduction of total cholesterol (p<0.025), of LDL cholesterol (p<0.05) and of glycemia (p<0.01) in group A and significant reduction of total cholesterol (p<0.05), of LDL cholesterol (p<0.05) and of glycemia (p<0.025) in group B. Both groups of patients achieved significantly longer time on the second exercise test (p<0.001 in group A and p<0.005 in group B).
Conclusions
The study showed that CR has favorable effects on QTd and DP in patients after CABG and RLVEF. In patients younger than 60 years CR has more favorable effects on the followed parameters. CR led to a significant increase in exercise tolerance, a significant decrease of myocardial oxygen uptake at rest, a and probably reduces the possibility of arrhythmia events, especially in patients younger than 60 years.