Left Atrial Volume and the Benefit of Cardiac Resynchronization Therapy in the MADIT-CRT Trial
Does left atrial volume (LAV) correlate with clinical outcomes in those who receive cardiac resynchronization therapy (CRT) with a defibrillator (CRT-D), and is this parameter a predictor of risk in this population?
The study cohort was comprised of 1,785 patients enrolled in the MADIT-CRT study. In this study, patients either with ischemic cardiomyopathy and New York Heart Association (NYHA) class I-II or with nonischemic cardiomyopathy and NYHA class II, QRS duration of ≥130 ms, and an ejection fraction of <0.30 were randomized to receive either CRT-D or an implantable cardioverter-defibrillator (ICD) in a 3:2 ratio. LAV (dichotomized at the upper quartile of >52 ml/m2) was utilized to assess the benefit of CRT-D versus defibrillator-only therapy in reducing the risk of heart failure or mortality. The relationship between LAV response to CRT-D and subsequent clinical outcomes was determined utilizing landmark analysis.
Utilizing multivariate analysis, the authors found that a higher baseline LAV (independent of baseline left ventricular volume) was associated with a 69% (p < 0.001) and 59% (p = 0.02) increased hazard for heart failure or death and/or all-cause mortality, respectively. There was a significant reduction in LAV with CRT-D when compared with defibrillator-only therapy (-28% vs. -10%, respectively; p < 0.001). Each 1% reduction in LAV following CRT-D was independently associated with a corresponding 4% reduction in the hazard of subsequent heart failure or death (p < 0.001). There was improved prediction of clinical response to the device with assessment of changes in LAV following CRT implantation when compared with assessment of the corresponding variations in left ventricular volume.
The authors concluded that LAV is an independent predictor of clinical outcomes in mildly symptomatic heart failure patients treated with CRT-D. CRT exerts pronounced reverse remodeling effects on the LA that independently correlate with improved clinical outcomes following device implantation.
This is an important study because it supports reports from earlier studies about the value of monitoring LA size as a predictor of clinical risk in mild heart failure. The favorable impact of CRT-D on LA size is probably due to improved diastolic function. The improved prognosis noted with the reduction in LA size is also probably due to a decreased burden of atrial fibrillation. These data should provide the basis for prospective studies to determine whether reverse LA remodeling improves cardiac outcomes.
Keywords: Prognosis, Defibrillators, Multivariate Analysis, Death, Cardiac Pacing, Artificial, Cardiomyopathies, Heart Failure, Diastole, New York, Cardiac Resynchronization Therapy
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