A reduction in total isovolumic time with cardiac resynchronisation therapy is a predictor of clinical outcomes

BackgroundTotal isovolumic time (t-IVT) reflects left ventricular (LV) asynchrony (when the ventricle is neither ejecting nor filling). It is prolonged in left bundle branch block (LBBB). Cardiac resynchronisation therapy (CRT) is a treatment for patients with heart failure, reduced LV ejection fraction and LBBB. CRT shortens t-IVT, but the long-term clinical benefit of such reduction after CRT has not been studied in this patient group.MethodsSeventy-three patients who underwent CRT had t-IVT measured before and after CRT implantation. The study end-point was a composite of unplanned heart failure hospitalisation and all-cause mortality.ResultsBaseline t-IVT showed considerable scatter: 30 patients had t-IVT values longer than 15 s/min (upper 95% limit of normal). The change in t-IVT with CRT was also variable: t-IVT shortened in 50 patients (from 16.2 ± 4.8 s/min to 11.7 ± 3.7 s/min: group A), and lengthened in 23 patients (from 11.7 ± 4.2 s/min to 14.5 ± 4.33 s/min: group B). The magnitude of change in t-IVT with CRT negatively correlated with baseline t-IVT (r = − 0.619, p < 0.001); thus t-IVT (significantly longer in group A than group B before CRT: 16.2 ± 4.8 s/min vs. 11.7 ± 4.2 s/min, p < 0.001) became significantly shorter in group A compared to group B after CRT (11.7 ± 3.7 s/min vs. 14.5 ± 4.3 s/min, p = 0.005). After follow-up of 30 months, 70% group A patients had event-free survival compared to 39% group B patients. The presence of any fall in t-IVT after CRT was an independent predictor of event-free survival.ConclusionT-IVT is a marker of global cardiac asynchrony that has predictive capacity on functional, symptomatic, and mortality endpoints in patients with advanced heart failure.