THE EFFECT OF VENTRICULAR ACTIVATION SEQUENCE ON CARDIAC-PERFORMANCE DURING PACING

The aim of this study was to evaluate the importance of a normal ventr icular activation pattern for cardiac performance. in nine mongrel dog s, atrial pacing was compared to AV synchronous pacing at three differ ent AV delays (150, 100, and 60 ms). In six dogs, proximal septal AV s ynchronous pacing was compared to apical AV synchronous pacing at thre e different AV delays. AV synchronous pacing was performed after RF in duced complete heart block. Hemodynamics were evaluated by assessment of positive and negative dP/dt, cardiac output, and left ventricular a nd pulmonary pressures. Atrial pacing was superior to AV synchronous p acing with respect to positive and negative dP/dt and cardiac output. This difference was present at all AV delays. Proximal septal pacing w as associated with a higher positive and negative dP/dt compared to ap ical pacing at all AV delays. Left ventricular activation time was sig nificantly shorter during proximal septal pacing th an during apical p acing (88 +/- 4 vs 115 +/- 4 ms, P < 0.001). We conclude that atrial a nd proximal septal pacing improves cardiac function and shortens She v entricular activation time compared to apical AV synchronous pacing in dependent of the AV interval.