Randomized trial results subgroup analyses

PAVE and OPSITE stand out among the published randomized trials of CRT in enrolling patients irrespective of pre-implant ejection fraction. In fact, nearly half of the patients in PAVE had a left ventricular ejection fraction above 45%. Post hoc analysis of PAVE suggests that the majority of the benefit in the trial was confined to the subgroup with a pre-implant ejection fraction of less than 45% (39). However, the opposite pattern was observed in OPSITE. In that trial, the comparative benefit to biventricular pacing was greatest in those patients with normal baseline left ventricular function (40). It is possible that these discordant results reflect the play of chance. A larger trial is necessary to resolve the issue. 

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