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Ann Thorac Surg 1984;38:260-264
© 1984 The Society of Thoracic Surgeons
Department of Surgery, State University of New York at Buffalo, School of Medicine, and the Buffalo General Hospital, Buffalo, NY
Accepted for publication March 3, 1984.
* Address reprint requests to Dr. Raza, Department of Surgery, The Buffalo General Hospital, 100 High Street, Buffalo, NY 14203
To determine the advantages of atrioventricular (AV) sequential pacing over ventricular demand pacing, paired cardiovascular hemodynamic studies were performed in each pacing mode at a constant heart rate. The paired studies included determination of ejection fraction (EF) by echocardiography and gated blood pool radionuclide scanning, and of cardiac output (CO) by the indicator-dilution method.
There was no significant difference in EF with either pacing mode. Determined by echocardiography, EF with AV sequential pacing was 57% compared with 56% with ventricular demand pacing; by the gated blood pool method, EF with AV sequential pacing was 58% compared with 57% in the ventricular mode. Significant improvement with AV sequential pacing was seen in CO (4.75 L/min from 3.75 L/min; p < 0.01); stroke volume (58 ml from 48 ml; p < 0.02); arteriovenous oxygen content difference (4.9 vol% from 5.6 vol%; p < 0.01); total peripheral resistance (1,724 dynes sec cm-5 from 2,025 dynes sec cm-5; p < 0.01); and cardiac contractility, as reflected by mixing time (6.9 seconds from 8.0 seconds; p < 0.02). No significant changes were noted in mean arterial or atrial pressure or in systemic oxygen consumption.
In a second group of 6 patients, similar paired studies were done in AV sequential pacing modes before and after therapeutic reduction of total peripheral resistance. A significant increase in CO (43%) was observed following reduction in total peripheral resistance. We conclude that AV sequential pacing improves CO more effectively than ventricular demand pacing. Cardiac output can be further enhanced in patients with congestive heart failure by pre-treatment with agents to reduce total peripheral resistance.
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