METABOLIC AND HEMODYNAMIC RESPONSES TO EXERCISE DURING ATRIAL FIBRILLATION AND SINUS RHYTHM

Circulatory, myocardial, and metabolic responses to exercise in terms of cardiac index, stroke index, and changes in blood lactate have been analyzed in 16 patients with atrial fibrillation before, and 24 hours after, conversion to sinus rhythm by synchronized D.C. shock. Circulatory response to exercise as measured by changes in the cardiac indexes showed a significant (22 per cent) improvement after restoration to sinus rhythm. Resting cardiac indexes also improved (15 per cent). Myocardial response to exercise, as estimated by stroke indexes, revealed a distinct improvement following defibrillation. This was demonstrated by absence of any increase during atrial fibrillation compared to a 21 per cent increase during sinus rhythm. Metabolic response to exercise, as measured by changes in blood lactate and lactate pyruvate ratios, indicated significant improvement after conversion to sinus rhythm in the patients with rheumatic heart disease, but not in patients with arteriosclerotic or hypertensive heart disease. These findings support the contention that converting atrial fibrillation to sinus rhythm will improve the circulatory, myocardial and metabolic responses to exercise. © 1968.