Prolonged total isovolumic time predicts cardiac events following coronary artery bypass surgery

Left ventricular (LV) systolic dysfunction may be associated with compromised stroke volume, which may be caused by asynchrony, reflected on the prolongation of isovolumic time (t-IVT). To assess the prognostic role of Doppler echocardiographic measurements in predicting cardiac events after coronary artery bypass grafting (CABG).

The study included 74 patients undergoing routine CABG. A pre-CABG Doppler echocardiographic assessment of LV dimensions, filling and ejection was performed and t-IVT was determined as [60 - (total ejection time + total filling time)]. Follow-up period was 18 +/- 12 months. Of the 74 patients (age 65 +/- 16 years, 59 males), 29 underwent hospital admission for a cardiac event or died. There were no differences in age, gender, incidence of previous infarct or mitral regurgitation, LV-EDD (left ventricular end-diastolic dimension), left atrial or right ventricular size in patients with cardiac events compared with those without events. Left ventricular end-systolic dimension (LV-ESD) was greater (4.5 +/- 0.9 vs. 3.9 +/- 0.9 cm, P = 0.003), fractional shortening (FS) was lower (21 +/- 4 vs. 32 +/- 8%), E:A ratio and Tei index were higher (2.1 +/- 0.8 vs. 1.0 +/- 0.6 and 0.9 +/- 0.3 vs. 0.6 +/- 0.3, all P < 0.001), and t-IVT was longer (16 +/- 5 vs.10 +/- 4 s/min, P < 0.001) in patients with events. Multivariate predictors of post-CABG events (odds ratio 95% confidence interval) were low FS [0.66 (0.50-0.87), P < 0.001], high E:A ratio [l4.13 (1.17-14.60), P = 0.028], large LV-ESD [0.19 (0.05-0.84), P = 0.029], and long t-IVT [1.37 (1.02-1.84), P = 0.035].

Despite satisfactory surgical revascularization, long t-IVT and systolic dysfunction suggest persistent ventricular dyssynchrony that contributes to post-CABG cardiac events. Early assessment of such patients for potential benefit from electrical resynchronization may optimize their cardiac performance and hence clinical outcome.