Effects of abnormal activation on the time course of the left ventricular pressure pulse in dilated cardiomyopathy.

OBJECTIVE

To investigate the effects of QRS duration on characteristics of the left ventricular pressure pulse derived from the time course of functional mitral regurgitation by continuous wave Doppler.

DESIGN

Retrospective and prospective study of 50 patients with dilated cardiomyopathy, by electrocardiography, echocardiography, and Doppler cardiography.

SETTING

Tertiary cardiac referral centre.

PATIENTS

50 patients (mean age (SD) 58 (16)) with dilated cardiomyopathy, all with functional mitral regurgitation.

RESULTS

The values of QRS duration ranged widely, from 70 to 190 ms with a mean value of 110 ms, and were unimodally distributed. The overall duration of mitral regurgitation correlated positively with QRS time (r = 0.65) over the entire range of values. When the duration of mitral regurgitation was divided into contraction, aortic ejection, and relaxation times, increased QRS duration prolonged contraction (r = 0.51) and relaxation (r = 0.52) times. Aortic ejection time was affected by RR interval (r = 0.74). Duration of QRS correlated negatively with peak rate of rise in left ventricular pressure (+dP/dt) (r = -0.48), and positively with the time intervals from Q to peak pressure (r = 0.49) and to peak +dP/dt (r = 0.72), and also with those from the start of mitral regurgitation to peak pressure (r = 0.49) and to peak +dP/dt (r = 0.76). Duration of QRS did not directly affect the peak rate of left ventricular pressure fall (-dP/dt), or the isovolumic relaxation period.

CONCLUSIONS

Values of QRS duration are unimodally distributed in patients with dilated cardiomyopathy, without evidence of a discrete group of patients with left bundle branch block. Prolonged QRS duration reduces peak +dP/dt, prolongs overall duration of the pressure pulse, the time to peak +dP/dt, and relaxation time. Duration of QRS must therefore be taken into account in assessing standard measurements of myocardial function in patients with dilated cardiomyopathy.