The impact of exercise-induced changes in intraventricular dyssynchrony on functional improvement in patients with nonischemic cardiomyopathy.

Abstract

BACKGROUND: The assessment of dynamic intraventricular dyssynchrony has been reported to be feasible in a clinical setting. However, its prognostic implication in functional improvement has not yet been investigated.

METHODS: Symptom-limited, supine bicycle exercise was performed on 41 patients with nonischemic cardiomyopathy (52 +/- 12 years, ejection fraction < 40%). Using Doppler tissue imaging, the average of peak systolic velocities at 6 basal segments was obtained at rest and peak exercise. Dyssynchrony index (Ts-SD12) was defined as the SD of the time to peak systolic velocities at 12 left ventricular segments. The percent change of end-systolic volume (%Delta ESV) was calculated at follow-up. A 15% or greater reduction in end-systolic volume (%Delta ESV < -15%) was considered as functional improvement.

RESULTS: During exercise, changes in dyssynchrony (Delta Ts-SD12) were individually variable. Average of peak systolic velocities (V) at 6 basal segments at peak exercise independently correlated with Ts-SD12 at peak exercise (beta = -0.541, P < .001). Follow-up echocardiography was performed on 35 patients after medical treatment for 13.0 +/- 4.9 months. There was significant association of %Delta ESV with the change in mitral regurgitation (r = 0.434, P = .009), disease duration (r = 0.343, P = .045), QRS interval (r = 0.347, P = .041), and Delta Ts-SD12 (r = 0.511, P = .002). Multivariate analysis identified Ts-SD12 measured at peak exercise as the strongest predictor for functional improvement (%Delta ESV: beta = 0.577, P < .001; and Delta ejection fraction: beta = -0.563, P < .001).

CONCLUSION: In patients with heart failure, dynamic dyssynchrony can be assessed during exercise. Ts-SD12 at peak exercise may be an independent predictor for reverse remodeling with medical treatment.