Cardiac Resynchronization Therapy Reduces Left Atrial Volume and the Risk of Atrial Tachyarrhythmias in MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy)

Oct 03, 2011
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Authors:
Brenyo A, Link MS, Barsheshet A, et al.
Citation:
J Am Coll Cardiol 2011;58:1682-1689.
Summary By:
Ragavendra R. Baliga, MBBS, FACC

Study Questions:

Does cardiac resynchronization therapy (CRT) result in reductions in left atrial volume (LAV) and in turn translate into a subsequent reduction in the risk of atrial tachyarrhythmias (ATs)?

Methods:

The MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy) investigators compared percent reduction in LAV at 1 year following CRT-D implantation (prespecified as low [lowest quartile: <20% reduction in LAV] and high [≥20% reduction in LAV] response to CRT-D) with the risk of subsequent AT (including atrial fibrillation, atrial flutter, atrial tachycardia, and supraventricular tachyarrhythmias) study participants.

Results:

The investigators found that cumulative probability of AT 2.5 years after assessment of echocardiographic response was lowest among high LAV responders to CRT-D (3%) and significantly higher among both low LAV responders to CRT-D (9%) and implantable cardioverter defibrillator–only patients (7%; p = 0.03 for the difference among the three groups). Their multivariate analysis demonstrated that high LAV responders to CRT-D experienced a significant 53% (p = 0.01) reduction in the risk of subsequent AT as compared with implantable cardioverter defibrillator–only patients, whereas low LAV responders did not derive a significant risk reduction with CRT-D therapy (hazard ratio [HR], 1.05; 95% confidence interval [CI], 0.54-2.00; p = 0.89). They also found that study participants who developed in-trial AT experienced significant increases in the risk for both the combined endpoint of heart failure or death (HR, 2.28; 95% CI, 1.45-3.59; p < 0.001) and the separate occurrence of all-cause mortality (HR, 1.89; 95% CI, 1.08-3.62; p = 0.01).

Conclusions:

The investigators concluded that favorable reverse remodeling of the left atrium with CRT-D therapy was associated with significant reduction in risk of subsequent AT.

Perspective:

This is an important study because it brings to the forefront the importance of the atria in the reverse remodeling of the heart in cardiac failure. It also suggests that CRT may reduce the likelihood of future atrial fibrillation in heart failure patients. Given the increased incidence of sleep apnea associated with heart failure, it would be interesting to know whether CRT has favorable impact on right atrial size and function. Incremental benefits in heart failure therapies in the future may come from those treatments that focus not only on improving left ventricular function, but also size and function of the atria.

Keywords: Risk, Defibrillators, Heart Conduction System, Sleep Apnea Syndromes, Tachycardia, Cardiac Resynchronization Therapy, Heart Diseases, Incidence, Death, Cardiac Pacing, Artificial, Heart Failure, Ventricular Function, Echocardiography


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