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Background Left bundle branch block (LBBB) leads to prolonged left ventricular (LV) total activation time (TAT) and ventricular electrical uncoupling (VEU; mean LV activation time minus mean right ventricular [RV] activation time); both have been shown to be preferential targets for cardiac resynchronization therapy (CRT). Whether right ventricular apical pacing (RVAP) produces similar ventricular activation patterns has not been well studied. Objective The purpose of this study was to compare electrical ventricular activation patterns during RVAP and LBBB. Methods We performed ECG mapping during sinus rhythm, RVAP, and CRT in 24 patients with LBBB. Results We observed differences in the electrical activation pattern with RVAP compared to LBBB. During LBBB, RV activation occurred rapidly; in contrast, RV activation was prolonged during RVAP (46 ± 21 ms vs 69 ± 17 ms, P <.001). There was no significant difference in LVTAT; however, differences in conduction pattern were observed. During LBBB, LV activation was circumferential, whereas with RVAP, LV activation proceeded from apex to base. Differences in the number, size, and orientation of lines of slow conduction also were observed. With LBBB, VEU was nearly twice as long as during RVAP (73 ± 12 ms vs 38 ± 21 ms, P <.001). CRT resulted in a greater reduction in VEU relative to LBBB activation (P <.001). Conclusion RVAP produces significant differences in ventricular activation characteristics compared to LBBB. Significantly less VEU occurs with RVAP, and as a result CRT produces a smaller relative reduction in VEU. This may explain the finding that CRT appears to be more effective in patients with LBBB than in those who were upgraded because of high percentages of RV pacing. [ABSTRACT FROM AUTHOR]

Background Although proposed to facilitate pulmonary vein isolation (PVI), high-power ablation may favor extracardiac damage. Negative component abolition of the unipolar signal reflects lesion transmurality. The present study sought to evaluate the safety and efficacy of high-power ablation using unipolar signal modification as a local end point. Methods High power and standard power were compared in 4 swine and 100 consecutive patients referred for PVI. The first 50 patients were included in the control group (25-30 W) and the last 50 patients in the study group (40-50 W). Atrial radiofrequency applications were stopped 2 s (study group and swine) or 5 s (control group) after unipolar signal modification. Ventricular radiofrequency applications of 500 J (25 W·20 s versus 50 W·10 s) were performed at the swine epicardium. Results Swine gross necropsy did not show any extracardiac damage related to atrial lesions. At equal energy of 500 J, 50 W lesions were deeper (3±0.9 versus 2.6±1.1 mm; P=0.03) and wider (6.2±2 versus 5±2.3 mm; P=0.006) than 25 W lesions. No complications occurred during the clinical study, whatever the power output used for PVI. For a similar sinus rhythm maintenance at 12 months (90% versus 88%; P=0.75), the study group displayed higher first-pass PVI (92% versus 73%; P<0.001), lower acute pulmonary vein reconnection (2% versus 17%; P<0.001), reduced procedure time (73.1±18.2 versus 107.4±21.2 min; P<0.001), and ablation time (13±2.9 versus 30.3±8.8 min; P<0.001). Conclusions High-power PVI guided by unipolar signal modification safely decreases procedural burden while ensuring robust 12-month outcomes. [ABSTRACT FROM AUTHOR]