Is the left ventricular lateral wall the best lead implantation site for cardiac resynchronization therapy?

Short-term hemodynamic studies consistently report greater effects of cardiac resynchronization therapy (CRT) in patients stimulated from a LV lateral coronary sinus tributary (CST) compared to a septal site. The aim of the study was to compare the long-term efficacy of CRT when performed from different LV stimulation sites. From October 1999 to April 2002, 158 patients (mean age 65 years, mean LVEF 0.29, mean QRS width 174 ms) underwent successful CRT, from the anterior (A) CST in 21 patients, the anterolateral (AL) CST in 37 patients, the lateral (L) CST in 57 patients, the posterolateral (PL) CST in 40 patients, and the middle cardiac vein (MCV) CST in 3 patients. NYHA functional class, 6-minute walk test, and echocardiographic measurements were examined at baseline, and at 3, 6, and 12 months. Comparisons were made among all pacing sites or between lateral and septal sites by grouping AL + L + PL CST as lateral site (134 patients, 85%) and A + MC CST as septal site (24 patients, 15%). In patients stimulated from lateral sites, LVEF increased from 0.30 to 0.39 (P < 0.0001), 6-minute walk test from 323 to 458 m (P < 0.0001), and the proportion of NYHA Class III-IV patients decreased from 82% to ;10% (P < 0.0001). In patients stimulated from septal sites, LVEF increased from 0.28 to 0.41 (P < 0.0001), 6-minute walk test from 314 to 494 m (P < 0.0001), and the proportion of NYHA Class III-IV patients decreased from 75% to 23% (P < 0.0001). A significant improvement in cardiac function and increase in exercise capacity were observed over time regardless of the IV stimulation sites, either considered singly or grouped as lateral versus septal sites.