Cardiac resynchronization therapy in chronic XXXX with moderately reduced left ventricular ejection fraction: Lessons from the Multicenter InSync Randomized Clinical Evaluation MIRACLE EF study.

@entity1 @entity1479 @entity712 @entity2729 @entity204
BACKGROUND: The benefits of CRT for symptomatic @entity712 ( @entity712 ) @entity1 with a wide QRS and reduced left ventricular ejection fraction (LVEF  <=35%), are well established .Post-hoc subgroup analyses suggest that CRT benefit may extend to @entity1 with LVEF >35%. METHODS: The MIRACLE EF was a prospective, randomized, controlled, double-blinded study to evaluate CRT-P in @entity712 @entity1 with LBBB and with LVEF of 36%-50% and no previous pacing or @entity1479 . The primary endpoint was a composite of time to first @entity712 event or @entity204 . All @entity1 were implanted with a CRT-P and randomized 2:1 to @entity2729 OFF groups. The minimum follow up time was 24months. RESULTS: The MIRACLE EF study was stopped for enrollment futility after 13months and enrolling only 44 @entity1 . The main difficulties in recruiting @entity1 were lack of eligible @entity1 , previous @entity1479 implants, and the reluctance of institutions, @entity1 or physicians to enroll in the study which included a potential 5year CRT OFF period. CONCLUSION: Despite a careful design, identification and randomization of eligible @entity1 were challenging and a trial to assess morbidity and mortality trial was not feasible. The MIRACLE EF experience illustrates the difficulties of designing a scientifically robust but feasible study to assess potential new indications for implantable devices. Smaller randomized studies with surrogate endpoints may therefore be more reasonable, although the potential impact of such studies on clinical practice, guidelines, and reimbursement remain to be determined.
