ABSTRACT
AIMS: Right ventricular (RV) septum is a non-apical site targeted during lead implantation. Electrocardiographic (ECG) recognition of mid-septal lead location is challenging. The aim of the study is to determine ECG correlates of RV mid-septal pacing. METHODS AND RESULTS: The present study is a pre-specified analysis of a prospective, multicenter study, which randomized recipients of an implantable cardioverter defibrillator to an apical vs. mid-septal RV lead positioning. Following implantation, a 12-lead ECG was recorded during intrinsic rhythm and RV pacing. In total, 227 patients, 121 in the apical group (76.9% males, 67.1 ± 11.3 years) and 106 in the mid-septal group (82.1% males, age 64.7 ± 12.7 years) were included. Apically as compared with septally paced patients had significantly longer paced QRS duration (177.0 ± 25.0 vs. 170.4 ± 21.7, respectively, P = 0.03) and significantly more leftward paced QRS axis (-71.6 ± 33.3° vs. 9.4 ± 86.5°, respectively, P < 0.001). A significantly higher proportion of patients in the mid-septal as compared with the apical group displayed predominantly positive QRS in lead V6 (62.3 vs. 4.1%, P < 0.001), predominantly positive QRS in any of the inferior leads (53.8 vs. 4.1%, P < 0.001), and a QR pattern in lead aVL (53.3 vs. 3.3%, P < 0.001). These ECG correlates were incorporated in a stepwise algorithm with total sensitivity of 87% and specificity of 90% for the identification of a mid-septal lead location. CONCLUSION: A mid-septal lead location may be identified using a simple stepwise algorithm, based on the presence of positive QRS in lead V6, positive QRS in any of the inferior leads, and a QR pattern in lead aVL.
