Hemodynamic Benefits of Atrio-Biventricular Pacing in Open Chest Dogs

ABSTRACT

BACKGROUND AND OBJECTIVES: The ventricular pacing electrodes are customarily placed into the right ventricular muscle because there is easily accessible. However detailed physiologic studies have shown that the single stimulation of right ventricular sites causes dysynchronous ventricular contraction due to early depolarization of the right ventricle and delayed depolarization of the left ventricle. In contrast, normal human ventricular activation, which is conducted by the Purkinje system, spreads transmurally from the endocardium to multiple paraseptal epicardial regions and results in more synchronous contraction of the ventricle. Therefore, the hypothesis that producing biventricular activation by simultaneously pacing ventricles across the septum might confer hemodynamic benefits over those of conventional right ventricular pacing. The purpose of this study was to evaluate the acute hemodynamic changes of different pacing modes (right ventricular RV, biventricular BV, atrio-right ventricular A-RV, and atrio-biventricular A-BV pacing). MATERIALS AND METHOD: In 9 open chest dogs anesthetized with alpha-chloralose, sinus node crushing was done, and then hemodynamic data (QRS width, femoral arterial pressure FAP, pulmonary arterial pressure PAP, and Cardiac output CO) were acquired after 5 minutes of pacing at a fixed rate during each pacing mode. RESULTS: Results were as follow 1. BV pacing significantly increased cardiac output compared with RV pacing (P<0.01). BV pacing significantly shortened QRS width compared with RV pacing (P<0.01). 2. A-BV pacing significantly increased cardiac output compared with A-RV pacing (P<0.01). A-BV pacing significantly shortened QRS width compared with A-RV pacing (P<0.01). 3. A-RV pacing significantly increased systolic pulmonary arterial pressure and cardiac output compared with BV pacing (P<0.01). CONCULSION These results support the use of atrio-biventricular pacing to improve acute hemodynamic performance.