Effect of concordance between sites of left ventricular pacing and dyssynchrony on acute electrocardiographic and echocardiographic parameters in patients with heart failure undergoing cardiac resynchronization therapy

Background: Wide QRS complexes are associated with left ventricular (LV) dyssynchrony, but an optimal site of LV pacing has not been established. Hypothesis: We hypothesized that concordance between the sites of LV pacing and of latest LV mechanical activation during cardiac resynchronization therapy (CRT) is associated with more favorable acute echocardiographic changes. Methods: An analysis of 28 consecutive patients (64 ± 15 years, 46% male, 52% ischemic heart disease, LV ejection fraction 0.24 ± 0.07, QRS 163 ± 22 ms, New York Heart Association ≥ 3 93%) implanted with biventricular (BIV) defibrillators was performed. Sites of latest LV activation were determined by tissue Doppler imaging (TDI) and speckle tracking (ST). The site of LV pacing was determined by fluoroscopy in two views. A concordance score (0-5) was created to describe the proximity of the pacing site to the site of the latest mechanical activation. Results: Compared with the worst concordance score, a perfect score was associated with shorter QRS width with LV (187 ± 40 vs. 246 ± 8 ms, p = 0.048) and BIV (134 ± 19 ms vs. 179 ± 39 ms, p = 0.05) but not with right ventricular pacing. A perfect concordance score was also associated with a greater acute reduction in LV volumes in systole (42 ± 36 ms 16 ± 22 ms, p = 0.068) and diastole (47 ± 37 vs. 8 ± 31 ml, p = 0.043) 24 h after CRT device implantation. Conclusions: A high concordance is associated with shorter QRS width with LV and BIV pacing and greater acute reduction in LV volumes. The effect of concordance on the intermediate and long-term response to BIV pacing deserves further evaluation.