Hemodynamic Benefits of Atrio-Biventricular Pacing in Open Chest Dogs

Background and Objectives:Ventricular pacing electrodes are customarily placed into the right ventricular muscle because it is easily accessible. However, detailed physiologic studies have demonstrated that the single stimulation of right ventricular sites causes dysynchronous ventricular contraction due to early depolarization of the right ventricle and a 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 may confer hemodynamic benefits greater than those of conventional right ventricular pacing. The purpose of this study was to evaluate the acute hemodynamic changes of the 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 α-chloralose, sinus node crushing was accomplished and the hemodynamic data (QRS width, femoral arterial pressure:FAP, pulmonary arterial pressure:PAP, and cardiac output:CO) was acquired following 5 minutes of pacing at a fixed rate during each pacing mode. Results:The results were as follow:1) BV pacing significantly increased cardiac output as compared with RV pacing (p<0.01). BV pacing significantly shortened the QRS width as compared with RV pacing (p<0.01). 2) A-BV pacing significantly increased cardiac output as compared with A-RV pacing (p<0.01). A-BV pacing significantly shortened the QRS width as compared with A-RV pacing (p<0.01). 3) A-RV pacing significantly increased systolic pulmonary arterial pressure and cardiac output as compared with BV pacing (p<0.01). Conclusion:These results support the use of atrio-biventricular pacing to improve acute hemodynamic performance. (Korean Circulation J 2001;31(4):420-426)