Time course of hemodynamic changes and improvement of exercise tolerance after cardioversion of chronic atrial fibrillation unassociated with cardiac valve disease

This study prospectively assessed the time course, magnitude and mechanism of the hemodynamic changes after restoration of sinus rhythm in patients with chronic atrial fibrillation (AF) unassociated with valvular disease. Severe cardiac dysfunction may occur after chronic supraventricular tachycardia in patients with and without underlying cardiac disease. Improvement may follow abolishment of the arrhythmia or adequate slowing of the ventricular rate. Eight patients were studied with a mean previous duration of AF of 10 ± 9 months. Ejection fraction, exercise capacity and the atrial contribution to the left ventricular filling (only during sinus rhythm) were studied before cardioversion, after cardioversion and 1 week, 1 month and 6 months thereafter. A significant improvement in ejection fraction from 36 ± 13 to 53 ± 8% (p <0.05) occurred at 1 month after cardioversion. Concomitantly, peak oxygen consumption had increased at 1 month, from 20.1 ± 7 to 25.2 ± 6 ml/min/kg (p <0.05). Thereafter, no further improvement in hemodynamic parameters occurred. The atrial systole improved already at 1 week (from 3 ± 5 to 16 ± 11%, p <0.05) and remalned unchanged thereafter. Thus, restoration of sinus rhythm was associated with a delayed improvement in ejection fraction and maximal exercise capacity, preceded by an early restoration of atrial contractility and an acute slowing of the heart rate. The discrepancy in time course of restoration of atrial and ventricular function parameters suggests that an intrinsic left ventricular cardiomyopathy is present in patients with AF

Differential effects of high-frequency versus low-frequency exercise training in rehabilitation of patients with coronary artery disease

OBJECTIVES We sought to study the influence of frequency of exercise training during cardiac rehabilitation on functional capacity (i.e., peak oxygen consumption [VO2] and ventilatory anaerobic threshold [VAT]) and quality of life (QoL).BACKGROUND Although the value of cardiac rehabilitation is now well established, the influence of the different program characteristics on outcome has received little attention, and the effect of frequency of exercise training is unclear. Functional capacity is regularly evaluated by peak VO2 but parameters of submaximal exercise capacity such as VAT should also be considered because submaximal exercise capacity is especially important in daily living.METHODS Patients with coronary artery disease (n = 130, 114 men; mean age 52 +/- 9 years) were randomized to either a high- or low-frequency program of six weeks (10 or 2 exercise sessions per week of 2 h, respectively). Functional capacity and QoL were assessed before and after cardiac rehabilitation. Global costs were also compared.RESULTS Compared with baseline, mean exercise capacity increased in both programs: for high- and low-frequency, respectively: peak VO2 = 15% and 12%, Wmax = 18% and 12%, VAT = 35% and 12% (all p < 0.001). However, when the programs were compared, only VAT increased significantly more during the high-frequency program (p = 0.002). During the high-frequency program, QoL increased slightly more, and more individuals improved in subjective physical functioning (p = 0.014). We observed superiority of the high-frequency program, especially in younger patients. Mean costs were estimated at 4,455 and 2,273 Euro, respectively, for the high- and low-frequency programs.CONCLUSIONS High-frequency exercise training is more effective in terms of VAT and QoL, but peak VO2 improves equally in both programs. Younger patients seem to benefit more from the high-frequency training. (C) 2000 by the American College of Cardiology