Relationship between acute improvement in left ventricular function to 6-month outcomes after cardiac resynchronization therapy in patients with chronic heart failure.

The long-term impact of cardiac resynchronization therapy (CRT)-induced acute improvement in left ventricular (LV) function is largely unknown. The goal of this study was to evaluate the significance of acute improvement in LV function resulting from CRT in patients with chronic heart failure (HF). The authors compared 6-month clinical composite score (CCS) and LV end-systolic (ESV) reduction (≥15% from baseline) response rates of CRT-treated patients enrolled in the Predictors of Response to CRT (PROSPECT) trial who showed an acute increase (≥15% from baseline) in LV ejection fraction (EF) vs those who did not show a similar change in EF. Of the 396 patients who had pre-implant and post-implant EF measurements, 78 (19.7%) had an increase in EF and 318 (80.3%) did not. Acute reduction of mitral regurgitation by at least one grade occurred in 26% and 23% of patients with and without an acute increase in EF, respectively. Patients with an acute increase in EF had significantly lower baseline EF and smaller LV volumes but otherwise similar characteristics. At 6 months, LVEF and LV volumes were significantly higher and lower in the increased EF group, respectively; however, CCS improvement (70.5% vs 69.5%) and LVESV reduction (57.1% vs 54.9%) response rates were comparable in the two groups. An acute ≥15% increase in LVEF with CRT does not predict 6-month effects of CRT on patient outcomes or LV reverse remodeling. That such findings occur in patients with smaller LV volumes, however, may provide additional insight into the mechanisms responsible for CRT-induced long-term improvement in LV function and clinical benefit.