Background One of the reasons for patient nonresponse to cardiac resynchronization therapy is a suboptimal left ventricular (LV) pacing site. LV electric delay (Q-LV interval) has been indicated as a prognostic parameter of cardiac resynchronization therapy response. This study evaluates the LV delay for the optimization of the LV pacing site. Methods and Results Thirty-two consecutive patients (23 men; mean age, 7111 years; LV ejection fraction, 30 +/- 6%; 18 with ischemic cardiomyopathy; QRS, 181 +/- 25 ms; all mean +/- SD) underwent cardiac resynchronization therapy device implantation. All available tributary veins of the coronary sinus were tested, and the Q-LV interval was measured at each pacing site. The hemodynamic effects of pacing at different sites were evaluated by invasive measurement of LV dP/dt(max) at baseline and during pacing. Overall, 2.9 +/- 0.8 different veins and 6.4 +/- 2.3 pacing sites were tested. In 31 of 32 (96.8%) patients, the highest LV dP/dt(max) coincided with the maximum Q-LV interval. Q-LV interval correlated with the increase in LV dP/dt(max) in all patients at each site (AR1 =0.98; P95 ms corresponded to a >10% in LV dP/dt(max). An inverse correlation between paced QRS duration and improvement in LV dP/dt(max) was seen in 24 patients (75%). Conclusions Pacing the LV at the latest activated site is highly predictive of the maximum increase in contractility, expressed as LV dP/dt(max). A positive correlation between Q-LV interval and hemodynamic improvement was found in all patients at every pacing site, a value of 95 ms corresponding to an increase in LV dP/dt(max) of 10%.
- cardiac resynchronization therapy
- heart failure