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WASHINGTON (FRONTLINE MEDICAL NEWS) – Patients with mild heart failure symptoms, left bundle branch block, and a left ventricular ejection fraction of 31% to 44% who received cardiac resynchronization therapy with a built-in defibrillator experienced a significant reduction in all-cause mortality, compared with those randomized to an implantable cardioverter-defibrillator alone during 7 years of follow-up.
These results from a new MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy) long-term follow-up substudy “suggest that patients with a relatively preserved ejection fraction greater than 30% benefit from CRT-D [cardiac resynchronization therapy defibrillator] and could potentially be considered for this therapy,” said Katherine Vermilye, MD, at the annual meeting of the American College of Cardiology.
This represents a broadening beyond the conclusions earlier reached in the landmark MADIT-CRT trial. In the primary report, MADIT-CRT investigators concluded that CRT-D significantly reduced the risk of heart failure events, compared with an implantable cardioverter defibrillator (ICD) alone during an average follow-up of 2.4 years in patients with mild symptoms of either ischemic or nonischemic cardiomyopathy, a wide QRS duration, an left ventricular ejection fraction (LVEF) of 30% or less, and left bundle branch block, but not in those who didn’t have left bundle branch block ( N Engl J Med. 2009 Oct 1;361:1329-38 ).
In a subsequent publication, the MADIT-CRT investigators reported that, with extension of follow-up to 7 years, CRT-D also provided a significant benefit in terms of all-cause mortality in addition to the reduced rate of heart failure events ( N Engl J Med. 2014 May 1;370:1694-701 ).
However, even though an LVEF of 30% or less was a requirement for participation in MADIT-CRT, it turned out that, when the initial screening echocardiograms were eventually analyzed in a central core laboratory, one-third of study participants actually had a baseline LVEF of 31% to 44%, with the majority of excessive values being in the 31%-35% range.
Dr. Vermilye, of the University of Rochester in New York, presented a post hoc analysis of long-term outcomes in the subgroup having a baseline LVEF greater than 30%. They totaled 450 of 1,224 MADIT-CRT participants with left bundle branch block. They were significantly older and more likely to be female than the 824 subjects with an LVEF of 30% or less. They also had a shorter QRS duration – an average of 160 ms, versus 165 ms in patients with an LVEF of 30% or lower – and a smaller baseline left ventricular end systolic volume of 151 mL, compared with 196 mL in patients with a lower LVEF.
In a multivariate Cox regression analysis adjusted for potential confounders, CRT-D in patients with a baseline LVEF greater than 30% was associated with a 54% reduction in the risk of all-cause mortality at 7 years of follow-up, compared with receipt of an ICD-only device and with a smaller yet significant 31% reduction in risk in those with an LVEF of 30% or less. Worsening heart failure events were reduced by 64% in patients with a baseline LVEF greater than 30% who received CRT-D, compared with ICD-only, and by 54% in those with a lower baseline LVEF.
The reduction in all-cause mortality seen with CRT-D was confined to patients who were high responders to CRT as defined echocardiographically by at least a 35% change in left ventricular end systolic volume 1 year post implantation. They had an 85% reduction in the risk of death during 7 years of follow-up with CRT-D if their baseline LVEF was greater than 30% and a 58% relative risk reduction if their LVEF was 30% or less.
In contrast, CRT-D brought a significantly reduced risk of heart failure events regardless of whether a patient was a low or high responder, although the magnitude of benefit was greater in the high responders. Among patients with a baseline LVEF greater than 30%, CRT-D low responders had a 52% reduction in risk of heart failure events, compared with ICD recipients, while CRT-D high responders had an 81% relative risk reduction. Similarly, in patients with a baseline LVEF of 30% or less, CRT-D low responders had 48% reduction in heart failure events and high responders had a 79% risk reduction, compared with the ICD-only group.
Because this is a post hoc analysis, these new MADIT-CRT findings require validation in future studies, Dr. Vermilye observed.
MADIT-CRT was supported by Boston Scientific. Dr.. Vermilye reported having no financial conflicts.