Key result
Cardiac resynchronization therapy improved LV dyssynchrony and contractile function compared to ICD only; each 1% improvement in GLS reduced the risk of death or heart failure by 24% (P<0.001).
Why the study?
Does CRT-D improve left ventricular dyssynchrony and contractile function compared to ICD only, and are these improvements associated with reduced death or heart failure in patients with mild heart failure?
RCT (n=761)
Does CRT-D improve left ventricular dyssynchrony and contractile function compared to ICD only, and are these improvements associated with reduced death or heart failure in patients with mild heart failure?
Answers are grounded in this paper and cite their sources.
CRT-D improves left ventricular dyssynchrony and contractile function compared to ICD alone, and these echocardiographic improvements strongly predict a lower risk of subsequent death or heart failure.
AIMS: To assess long-term effects of cardiac resynchronization therapy (CRT) on left ventricular (LV) dyssynchrony and contractile function, by two-dimensional speckle-tracking echocardiography, compared with implantable cardioverter defibrillator (ICD) only in MADIT-CRT. METHODS AND RESULTS: We studied 761 patients in New York Heart Association I/II, ejection fraction ≤30%, and QRS ≥130 ms [n = 434, CRT-defibrillator (CRT-D), n = 327, ICD] with echocardiographic studies available at baseline and 12 months. Dyssynchrony was determined as the standard deviation of time to peak transverse strain between 12 segments of apical four- and two-chamber views, and contractile function as global longitudinal strain (GLS) by averaging longitudinal strain over these 12 segments. We compared changes in LV dyssynchrony and contractile function between treatment groups and assessed relationships between these changes over the first year and subsequent outcomes (median post 1-year follow-up = 14.9 months). Mean changes in LV dyssynchrony and contractile function measured by GLS in the overall population were, respectively, -29 ± 83 ms and -1 ± 2.9%. However, both LV dyssynchrony (CRT-D: -47 ± 83 ms vs. ICD: -6 ± 76 ms, P < 0.001) and contractile function (CRT-D: -1.4 ± 3.1% vs. ICD: -0.4 ± 2.5%, P < 0.001) improved to a greater extent in the CRT-D group compared with the ICD-only group. A greater improvement in dyssynchrony and contractile function at 1 year was associated with lower rates of the subsequent primary outcome of death or heart failure, adjusting for baseline dyssynchrony and contractile function, treatment arm, ischaemic status, and change in LV end-systolic volume. Each 20 ms decrease in LV dyssynchrony was associated with a 7% reduction in the primary outcome (P = 0.047); each 1% improvement in GLS over the 12-month period was associated with a 24% reduction in the primary outcome (P < 0.001). CONCLUSION: Cardiac resynchronization therapy resulted in a significant improvement in both LV dyssynchrony and contractile function measured by GLS compared with ICD only and these improvements were associated with better subsequent outcomes.
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Pouleur et al. (2011) conducted an RCT in Heart failure (n=761). Cardiac resynchronization therapy (CRT-D) vs. Implantable cardioverter defibrillator (ICD) only was evaluated on death or heart failure (24% reduction per 1% improvement in GLS, p=<0.001). Cardiac resynchronization therapy improved LV dyssynchrony and contractile function compared to ICD only; each 1% improvement in GLS reduced the risk of death or heart failure by 24% (P<0.001).
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