Background: Cardiac resynchronization therapy (CRT) has been accepted as an established
therapy for advanced systolic heart failure. Electrical and mechanical dyssynchrony are usually
evaluated to increase the percentage of CRT responders. We postulated that QRS notch can
increase mechanical LV dyssynchrony independently of other known predictors such as left
ventricular ejection fraction and QRS duration.
Methods: A total of 87 consecutive patients with advanced systolic heart failure and QRS
duration more than 120 ms with an LBBB-like pattern in V1 were prospectively evaluated.
Twelve-lead electrocardiogram was used for detection of QRS notch. Complete
echocardiographic examination including tissue Doppler imaging, pulse wave Doppler and
M-mode echocardiography were done for all patients.
Results: Eighty-seven patients, 65 male (75%) and 22 female (25%), with mean (SD) age of
56.7 (12.3) years were enrolled the study. Ischemic cardiomyopathy was the underlying heart
disease in 58% of the subjects, and in the others it was idiopathic. Patients had a mean (SD)
QRS duration of 155.13 (23.34) ms. QRS notch was seen in 49.4% of the patients in any of
two precordial or limb leads. Interventricular mechanical delay was the only mechanical
dyssynchrony index that was significantly longer in the group of patients with QRS notch.
Multivariate analysis revealed that the observed association was actually caused by the effect of
QRS duration, rather than the presence of notch per se.
Conclusions: QRS notch was not an independent predictor of higher mechanical
dyssynchrony indices in patients with wide QRS complex and symptomatic systolic heart
failure; however, there was a borderline association between QRS notch and interventricular
delay