Relation Between Variability of Ventricular Response Intervals and Exercise Capacity in Patients With Non-Valvular Atrial Fibrillation

Abstract

trial fibrillation (AF) is the most common arrhythmia, with a prevalence of 0.4-0.5% for the overall population, and is associated with increased mortality and morbidity. 1 With regard to treatment, the heart rate control strategy is as effective as the rhythm control strategy, 2,3 but the target heart rate in this strategy is as yet unclear, although the heart rate during AF may be related to the prognosis and/or the quality of the patient's life. A heart rate less than 90 beats/min at rest and 115 beats/min during moderate exercise has been recommended, 4 but is based on clinical experience.In patients with sinus rhythm, heart rate variability has been used to evaluate the vagal and sympathetic influences on the heart and to identify patients at risk for a cardiovascular event or death. [5][6][7][8][9][10][11][12] In patients with AF, recent studies have reported that reduced variability of the ventricular response interval (VRI) during AF might predict an adverse prognosis. 13,14 VRI variability is known to be dependent on the increased parasympathetic tone in AF, as well as in sinus rhythm, 15 which may be related to an active life of AF patients. On the basis of these facts, we hypothesized that analysis of VRI variability during AF might be useful as an assessment of exercise capacity as a representative of quality of life in AF patients. To test this hypothesis, we examined whether or not VRI variability is related to exercise capacity in AF patients. If it holds true, it could be a new maker for the management of AF patients. Methods Study PatientsThirty-one patients with persistent AF for more than 6 months were included (29 men, 2 women; age 60±7.4 years; left ventricular ejection fraction (LVEF): 61.2±6.5%, left atrial dimension: 44.9±7.0 mm). None of the patients had structural heart disease or had been prescribed any drugs for the control of heart rate, including antiarrhythmic agents. VRI Variability and Exercise ToleranceTwenty-four-h ambulatory electrocardiographic (ECG) recording was performed during the patients' usual daily activities and the VRI variability was analyzed by the time domain method. Two parameters were adopted as the expression of total and 5 min-term VRI variability: the standard deviation of all the R-R intervals (SDNN) and of the 5-min mean R-R interval (SDANN). To evaluate the exercise capacity of the patients, Bruce's multi-stage maximal treadmill protocol was performed with 3-min periods to allow achievement of a steady state before workload was increased. Exercise was continued until the patients complained of shortness of breath, the endpoint of exercise in the present study. We determined the relation between the VRI variability during 24-h ambulatory ECG monitoring and exercise capacity in the treadmill exercise testing. Statistical AnalysisAll values are expressed as mean ± SD. Data were ana- Background Reduced variability of the ventricular response interval (VRI) has been reported to predict adverse prognosis in patients with atrial fibrillation (AF). To examine whe...

Additional Physical Activity During Cardiac Rehabilitation Leads to an Improved Heart Rate Recovery in Male Patients After Coronary Artery Bypass Grafting

“…[13][14][15] The results of the present study, in which increasing the out-of-program activity resulted in marked improvement of the HRR, suggest that lifestyle activity can effect an adequate increase in vagal reflex. Indeed, CR staff should advise sedentary post-CABG patients to increase their level of ordinary physical activity when they are not attending the structured program.…”

Event‐Recorder Monitoring in the Diagnosis of Atrial Fibrillation in Symptomatic Patients: Subanalysis of the SOPAT Trial

“…Although the prevalence of symptoms during AF correlates with an increased heart rate, reduction of the heart rate by antiarrhythmics might not be the only important mediator for the reduction of symptoms since sotalol reduces the heart rate most effectively but showed only a trend but no significant reduction of symptomatic versus asymptomatic AF, compared with placebo. One might speculate that these differences between sotalol and Q+V could be explained by other influencing factors, such as a reduced contractility under sotalol as a beta‐blocking agent, changes in the heart rate variability during AF, 15 or by influencing the duration of an AF episode. These factors could not be assessed in this study.…”