Determination of the Longest Intrapatient Left Ventricular Electrical Delay May Predict Acute Hemodynamic Improvement in Patients After Cardiac Resynchronization Therapy

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%.