Cardiac Output by External Radioisotope Counting in Patients Reverted from Atrial Fibrillation

¹ Assistant Professor of Medicine, Ohio State University
² Staff Physician, Veterans Administration Center
³ Biochemist, Radioisotope Laboratory, Veterans Administration Center

1. Eleven of 14 patients were converted from atrial fibrillation to normal sinus rhythm by quinidine. Cardiac output at rest was performed before and after reversion and the cardiac output was repeated in five patients after a half-Master exercise test.

2. Cardiac output was low initially at rest, but improved significantly after restoration of sinus rhythm in nine of the 11 patients. The mean increase of 35 per cent in the 11 was accomplished without any material change in pulse rate, and was due to the similar increase in stroke volume.

3. In the five patients studied, the cardiac output initially showed little response to exercise, but after reversion, a greater response to exercise occurred. Cardiac output after exercise showed a mean rise of 48 per cent by reversion.

4. A simple method of cardiac output by external radioisotope counting requiring only venipuncture may be used to evaluate each patient regarding the efficacy of conversion from atrial fibrillation to sinus rhythm. A decision may thus be made with regard to continuation of quinidine therapy.