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J Thorac Cardiovasc Surg 2004;128:98-102
© 2004 The American Association for Thoracic Surgery

Cardiopulmonary support and physiology

Load dependence of cardiac output in biventricular pacing: Right ventricular volume overload in pigs

^a Department of Surgery, Columbia University College of Physicians and Surgeons, New York, NY, USA
^b Department of Biostatistics, Columbia University College of Physicians and Surgeons, New York, NY, USA

Received for publication August 5, 2003; revisions received December 10, 2003; accepted for publication January 21, 2004.

^* Address for reprints: Henry M. Spotnitz, MD, Department of Surgery, Columbia University College of Physicians and Surgeons, 622 W 168th St, PH 14-103, New York, NY 10032, USA
hms2{at}Columbia.edu

BACKGROUND: Previous work from our laboratory has demonstrated that optimization of biventricular pacing is load dependent. During acute pulmonary stenosis and right ventricular pressure overload in swine, cardiac output was maximized by pacing the right ventricle 40 ms before the left ventricle. To extend those studies, this experiment examined biventricular pacing optimization during right ventricular volume overload.

METHODS: After median sternotomy in 6 anesthetized domestic pigs, complete heart block was induced by ethanol ablation. A conduit was grafted from the right ventricle to the right atrium to simulate tricuspid insufficiency. During epicardial, atrial tracking DDD biventricular pacing, atrioventricular delay was varied between 60 and 180 ms in 30-ms increments. Right ventricular–left ventricular delay was varied at each atrioventricular delay from +80 ms (right ventricle first) to –80 ms (left ventricle first) in 20-ms increments. Aortic flow, right ventricular pressure, and electrocardiogram were measured at each pacemaker setting with the graft clamped and unclamped.

RESULTS: Atrioventricular and right ventricular–left ventricular delays had no significant effect on cardiac output with the graft clamped. With the graft unclamped, however, there was a statistically significant (P = .003 by mixed modeling repeated measures analysis of variance) trend toward higher cardiac output with left ventricle–first pacing.

CONCLUSION: Left ventricle–first biventricular pacing in swine significantly increased cardiac output during acute tricuspid insufficiency but not during the control state. Trials are warranted to develop clinical biventricular pacing for treatment of perioperative right ventricular dysfunction.

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				T. A. Quinn, G. Berberian, S. E. Cabreriza, L. J. Maskin, A. D. Weinberg, J. W. Holmes, and H. M. Spotnitz Effects of sequential biventricular pacing during acute right ventricular pressure overload Am J Physiol Heart Circ Physiol, November 1, 2006; 291(5): H2380 - H2387. [Abstract] [Full Text] [PDF]

				Load dependence of cardiac output in biventricular pacing: left ventricular volume overload in pigs. J. Thorac. Cardiovasc. Surg., March 1, 2006; 131(3): 666 - 670.