Effects of proximal ventricular septal pacing on hemodynamics and ventricular activation

Recently the use of alternate site pacing to improve cardiac-function in pa tients with bradyarrhythmias has increased. In the present study: hemodynam ics of right ventricular septal pacing were studied in seven dogs. A bipola r screw-in lead and endocardial lead were placed in the proximal right vent ricular septum and right ventricular apex, respectively. The right ventricl e was paced from each site. A conductance catheter and Millar catheter were inserted into the left ventricle to determine the left ventricular pressur e and the pressure-volume loop. Cardiac output was measured using the therm odilution method. In five of the seven dogs, ventricular activation was doc umented by isochronal epicardial activation mapping during each pacing mode . Mean arterial pressure and cardiac output during septal pacing were signi ficantly higher than during apical pacing (110 +/- 17 mmHg vs 100 +/- 18 mm Hg; 1.00 +/- 0.39 L/min vs 0.89 +/- 0.33 L/min). The positive dp/dt during septal pacing was significantly higher than during apical pacing (2137 +/- 535 mmHg/s vs 1911 +/- 404 mmHg/s). End-systolic elastance during septal pa cing was significantly higher compared to apical pacing (13.1 +/- 0.3 mmHg/ mL vs 8.9 +/- 4.0 mmHg/mL). The ventricular activation time during septal p acing was significantly shorter than during apical pacing. The epicardial m aps generated during septal pacing were similar to those from atrial pacing . We conclude that hemodynamics and interventricular conduction are less di sturbed by proximal right ventricular septal pacing than apical pacing in d ogs with normal hearts.