Different effect of exercise on left ventricular diastolic time and interventricular dyssynchrony in heart failure patients with and without left bundle branch block

Background: In patients with idiopathic dilated cardiomyopathy (IDCM) a prolongation of left ventricular (LV) systole at the expense of diastolic time was demonstrated. Our study was aimed to evaluate the effect of exercise on heart rate corrected diastolic time in controls, IDCM with and without LBBB, and patients with LBBB and normal LV function. Methods: 47 patients with IDCM, 30 without LBBB, and 17 with LBBB as well as 11 with isolated LBBB were studied during exercise using a combined hemodynamic-radionuclide angiographic approach. The phases of the cardiac cycle were derived with high temporal resolution from the ventricular time-activity curve. The loss of diastolic time per beat (LDT) was quantified using a regression equation obtained from a control group (n=24). Results: A significant LDT was demonstrated at rest and during peak exercise in IDCM patients with LBBB (39.1±32 and 37.3±30 ms; p < 0.001). In IDCM patients with normal activation LDT was unaffected at baseline, but elevated during peak exercise. This response was paralleled by an increase in interventricular mechanical dyssynchrony. Conclusion: During exercise an abnormal shortening of LV diastolic time is a common characteristic of heart failure patients which can be explained by the high prevalence of mechanical dyssynchrony.