Left Ventricular Stimulation With Electrical Latency Predicts Mortality in Patients Undergoing Cardiac...

This study sought to evaluate the prognostic value of the time interval from left ventricular (LV) pacing to the earliest onset of QRS complex (S-QRS) for long-term clinical outcomes in patients who underwent cardiac resynchronization therapy (CRT).

The electrical latency during LV pacing evaluated by S-QRS is associated with local tissue property, and the S-QRS ≥37 ms has been previously proposed as an independent predictor of mechanical response to CRT.

This study included 82 consecutive patients with heart failure with reduced LV ejection fraction (≤35%) and a wide QRS complex (≥120 ms) who underwent CRT. Patients were divided into a short S-QRS group (SS-QRS; <37 ms) and a long S-QRS group (LS-QRS; ≥37 ms). The primary endpoint was total mortality, including LV assist device implantation or heart transplantation, whereas the secondary endpoint was total mortality or HF hospitalization.

S-QRS was 25.9 ± 5.3 ms in SS-QRS and 51.5 ± 13.7 ms in LS-QRS (p < 0.01), and baseline QRS duration and electrical activation at the LV pacing site (i.e., Q-LV) were similar. During mean follow-up of 44.5 ± 21.1 months, 24 patients (29%) reached the primary endpoint, whereas the secondary endpoints were observed in 47 patients (57%). LS-QRS had significantly worse event-free survival for both endpoints. LS-QRS was an independent predictor of total mortality (hazard ratio: 2.6; 95% confidence interval: 1.11 to 6.12; p = 0.03) and the secondary composite events (hazard ratio: 2.4; 95% confidence interval: 1.31 to 4.33; p < 0.01).

The S-QRS ≥37 ms at the LV pacing site was a significant predictor of total mortality and HF hospitalization. S-QRS-guided optimal LV lead placement is critical in patients who receive CRT.