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(Circulation. 1971;44:649.)
© 1971 American Heart Association, Inc.

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Hemodynamic Evaluation of Rate Augmentation Produced by Atrial Pacing and Isoproterenol in the Early Postoperative Phase of Cardiac Valve Surgery

PAUL W. ARMSTRONG M.D.¹; HERMAN K. GOLD M.D.¹; MORTIMER J. BUCKLEY M.D.¹; JAMES T. WILLERSON M.D.¹; CHARLES A. SANDERS M.D.¹

¹ From the Departments of Medicine and Surgery, Harvard Medical School, and the General Medical and Surgical Services of the Massachusetts General Hospital, Boston, Massachusetts.

The hemodynamic effects of atrial pacing were evaluated in a group of 19 patients soon after cardiac valve surgery. Atrial pacing at 30 beats/min above the control rate of 88 beats/min produced an increase in cardiac index of 600 ml/min/m².

Isoproterenol was infused into eight of these patients to produce an increment in heart rate identical to that during atrial pacing. In these patients atrial pacing produced an increment in cardiac index of 400 ml/min/m² as compared to an increment of 1400 ml/min/m² produced by isoproterenol.

It is concluded (1) that atrial pacing is a useful technique for augmenting cardiac index soon after cardiac valve surgery and (2) that isoproterenol provides a greater increment in cardiac index at identical heart rates and the major portion of its effect is directly inotropic.

Key Words: Rate treppe • Chronotropism • Inotropism

Submitted on May 27, 1971
Accepted on June 18, 1971