Cardiac resynchronization therapy may benefit patients with left ventricular ejection fraction >35%: a PROSPECT trial substudy

Cardiac resynchronization therapy (CRT) is currently limited to those with left ventricular ejection fraction (LVEF) < 35%. To evaluate whether patients with LVEF > 35% might benefit from CRT, we performed a retrospective analysis of the predictors of response to CRT (PROSPECT) database. PROSPECT was a prospective, multicentre study that enrolled CRT patients based on enrolling centre-evaluated LVEF < 35%, but all echocardiograms were subsequently analysed by a core laboratory. Patients with core laboratory-measured LVEF > 35% (OVER35) were compared with those whose LVEF was < 35% (UNDER35). Clinical composite score (CCS) and change in LV end systolic volume (LVESV) were analysed from baseline to 6-month follow-up. Of 361 patients, 86 (24%) had LVEF > 35%. At entry, OVER35 had smaller LV volumes, shorter QRS duration, shorter 6-min walk distance, and were more likely to have ischaemic aetiology than UNDER35. Outcomes were comparable between the groups, with 62.8% of OVER35 improved in CCS (70.2% in UNDER35) and 50.8% of OVER35 improved in LVESV (57.8% in UNDER35). Patients with LVEF > 35%, New York heart association functional Class III-IV status, and QRS > 130 ms appear to derive clinical and structural benefit from CRT. As CRT may offer a valuable option for these patients, this hypothesis should be formally tested in a prospective, randomized multicentre trial.