Objectives: QRS complex width is not an accurate marker of cardiac asynchrony. Our aims were to determine the prevalence of cardiac asynchrony by Doppler echocardiography for patients with left ventricular (LV) dysfunction and to evaluate whether QRS width is a reliable method for detecting asynchrony.
Methods: In all, 316 consecutive patients with a LV ejection fraction less than 40% from 13 hospitals comprised the study group. Interventricular asynchrony was defined by the interventricular mechanical delay. Intraventricular asynchrony was evaluated using the calculation of the septal-to-posterior wall motion delay, the difference between time from Q wave to LV ejection end, and time from Q wave to the end of the systolic wave of the most delayed basal segment by Doppler tissue imaging, the SD of the time from the Q wave to the end of the systolic wave of 4 basal segments, and the maximum difference in the time from the Q wave to the end of the systolic wave of all 4 basal segments.
Results: Mean age was 62.14 +/- 13.5 years (234 men; 74.1%). Interventricular asynchrony was present in 50 (26.2%) patients in the narrow QRS group and in 57 (55.3%) patients in the prolonged QRS group (P < .001). Intraventricular asynchrony was present in 40 (20.8%) to 136 (72.8%) patients in the narrow QRS group and in 27 (26.2%) to 82 (79.6%) in the prolonged QRS group, depending on the method used.
Conclusions: Cardiac asynchrony is highly prevalent for patients with LV dysfunction but there is a very poor agreement among the different methods used to detect it. Interventricular asynchrony is more prevalent for patients with prolonged QRS but intraventricular asynchrony is irrespective of the QRS duration. Further studies are needed to evaluate which method is the best to detect cardiac resynchronization therapy responders.