Effects of physical exercise on cardiac dyssynchrony in patients with impaired left ventricular function

The purpose of this study was to determine the effect of exercise on dyssynchrony in patients with left ventricular dysfunction.

Sixty patients with a left ventricular ejection fraction (LVEF) ≤ 35% were studied. Interventricular mechanical delay (IVMD), intraventricular mechanical delay [Ts-(lateral-septal)], and left ventricular filling ratio were measured at rest and during exercise. Significant IVMD was defined as a difference between aortic and pulmonary pre-ejection times of >40 ms. Intraventricular dyssynchrony was defined as a Ts-(lateral-septal) >65 ms. Forty-five patients with no dyssynchrony at rest were analysed (age 62 ± 14; LVEF 28 ± 6%) and compared with a control group of 15 patients with known dyssynchrony at rest. None of the 45 patients without dyssynchrony at rest developed dyssynchrony during exercise based on IVMD and Ts-(lateral-septal). In the control group, IVMD decreased from 65 ± 19 to 33 ± 11 ms (P< 0.001) during exercise, whereas Ts-(lateral-septal) did not change. Persistence of dyssynchrony during exercise (decrease of IVMD <60%) was significantly associated with response to cardiac resynchronization therapy (CRT). Whereas all 10 responders had persistent dyssynchrony during exercise, 4 of the 5 non-responders (80%) had an exercise-induced decrease of IVMD >60% (P< 0.004).

Exercise does not elicit mechanical dyssynchrony in patients without dyssynchrony at rest. In patients with significant dyssynchrony at rest, exercise-induced decrease of IVMD is common. Persistence of dyssynchrony during exercise might be a novel predictor of response to CRT.