The Effect of Pharmacological Stress on Intraventricular Dyssynchrony in Left Ventricular Systolic Dysfunction

Background Cardiac resynchronisation therapy (CRT) improves symptoms and exercise capacity in many patients with heart failure (HF) who have left ventricular systolic dysfunction (LVSD) and markers of dyssynchrony. LV dyssynchrony is conventionally measured at rest but the symptoms of heart failure occur predominantly on exercise. Induction or exacerbation of dyssynchrony during stress might identify additional patients who could benefit from CRT. Methods and results Seventy-seven patients (47 with QRSd<120 ms and 30 with QRSd>120 ms) with heart failure due to left ventricular systolic dysfunction and 22 normal subjects underwent dobutamine stress echocardiography using colour tissue Doppler imaging. Left intraventricular dyssynchrony was measured as the standard deviation of the time to peak velocity from the onset of the QRS (Ts-SD) and the difference between the maximum and minimum time to peak velocity (Tscor-diff) in the 12 non-apical segments at rest and during peak stress. Timings were corrected for heart rate. The mean values of these indices increased with stress in both groups of patients but not in control subjects (p < 0.001). The prevalence of conventionally-defined dyssynchrony also increased with stress. Conclusion In patients with heart failure, the severity and the prevalence of intraventricular dyssynchrony increase with stress. Whether stress-induced dyssynchrony will identify patients who might benefit from CRT awaits further research.