Background
Total 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.
Methods
Seventy-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.
Results
Baseline 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.
Conclusion
T-IVT is a marker of global cardiac asynchrony that has predictive capacity on functional, symptomatic, and mortality endpoints in patients with advanced heart failure.
Publication information
Guha K, Mantziari L, Sharma R, McDonagh TA, Gibson D, Duncan AM. A reduction in total isovolumic time with cardiac resynchronisation therapy is a predictor of clinical outcomes. Int J Cardiol. 2013 Sep 20;168(1):382-7.