Time Course of Effects of Cardiac Resynchronization Therapy in Chronic Heart Failure: Benefits in Patients with Preserved Exercise Capacity

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Abstract

Objectives

To assess in patients with chronic heart failure the effect of cardiac resynchronization therapy (CRT) over 12 months' follow-up the time course of the changes in functional and neurohormonal indices and to identify responders to CRT.

Methods

Eighty-nine patients (74.1 ± 1 years, left ventricular ejection fraction [LVEF] < 35%), QRS complex duration >150 ms, in stable New York Heart Association (NYHA) class III or IV on optimal medical treatment were prospectively randomized either in a control (n = 45) or CRT (n = 44) group and underwent clinical evaluation, cardiopulmonary exercise testing (CPET), 2D-Echo, heart rate variability (HRV), carotid baroreflex (BRS), and BNP assessments before and at 6- and 12-month follow-up.

Results

In the CRT group, improvement of cardiac indices and BNP concentration were evident at medium term (over 6 months) follow-up, and these changes persisted on a longer term (12 months) (all P < 0.05). Instead CPET indices and NYHA class improved after 12 months associated with restoration of HRV and BRS (all P < 0.05). We identified 26 responders to CRT according to changes in LVEF and diameters. Responders presented less depressed hemodynamic (LVEF 25 ± 1.0 vs 22 ± 0.1%), functional (peak VO2 10.2 ± 0.2 vs 6.9 ± 0.3 ml/kg/min), and neurohormonal indices (HRV 203.6 ± 15.7 vs 147.6 ± 10.ms, BRS 4.9 ± 0.2 vs 3.6 ± 0.3 ms/mmHg) (all P < 0.05). In the multivariate analysis, peak VO2 was the strongest predictor of responders

Conclusions

Improvement in functional status is associated with restoration of neurohormonal reflex control at medium term. Less depressed functional status (peak VO2) was the strongest predictor of responders to CRT.

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