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(Circulation. 1968;37:II-173.)
© 1968 American Heart Association, Inc.

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Restoration of Sinus Rhythm After Mitral Valve Replacement

Correlations with Left Atrial Pressure and Size

R. DARRYL FISHER M.D.¹; DEAN T. MASON M.D.¹; ANDREW G. MORROW M.D.¹

¹ From the Clinic of Surgery and Cardiology Branch, National Heart Institute, Bethesda, Maryland 20014.

Factors relating to the successful and sustained restoration of sinus rhythm were examined in 100 patients following mitral valve replacement. Of the 30 patients who established sinus rhythm in the postoperative period, 24 were in sinus rhythm before operation and 6 converted spontaneously. All 30 had normal mean left atrial pressure at rest and only mild or moderate roentgenographic evidence of left atrial enlargement. All 70 patients with atrial fibrillation following valve replacement had been in atrial fibrillation preoperatively; in 24 of them cardioversion was not attempted. In the other 46 patients, electrical conversion was attempted on one or more occasions; in 31 (68%), sinus rhythm was maintained for at least 24 hours, but only 9 were in sinus rhythm 18 months later. Two additional patients maintained sinus rhythm on a long-term basis after conversion with maintenance quinidine.

Among the 15 patients refractory to countershock, the mean left atrial pressure averaged 11.1 ± 1.3 mm Hg, and among the 22 patients who reverted to atrial fibrillation it was 13.3 ± 0.9 mm Hg. In contrast, mean left atrial pressure was significantly less (8.1 ± 0.9 mm Hg) and left atrial enlargement only moderate in the patients who maintained sinus rhythm after cardioversion. Importantly, all patients with mean left atrial pressures greater than 12 mm Hg and/or marked left atrial enlargement were refractory to countershock or relapsed to atrial fibrillation, while 64% of patients with normal mean left atrial pressures sures and only moderate left atrial enlargement maintained sinus rhythm permanently. Right atrial pressures were normal in both groups.

Thus, elevated left atrial pressure and increased left atrial size both militate against the chronic establishment of sinus rhythm. This study indicates that following mitral valve replacement permanent maintenance of sinus rhythm can be anticipated in about two of three patients in whom the mean left atrial pressure is normal and in whom left atrial enlargement is only moderate.