Objective-To study the influence of atrial fibrillation on peak oxygen uptake (peak ṼO 2 ) in chronic heart failure. An unfavourable eVect of atrial fibrillation has been shown in several patient populations, but the results have not been consistent in chronic heart failure. Methods-Data were analysed from male heart transplant candidates who were able to perform graded bicycle ergometry until exhaustion with respiratory gas analysis and measurement of heart rate. Patients in atrial fibrillation (n = 18) were compared with patients in sinus rhythm (n = 93). Results-Age, weight, height, and aetiology of chronic heart failure did not diVer significantly between the two groups. Cardiac catheterisation at supine rest showed that heart rate was comparable, but that stroke volume and cardiac output were lower (p < 0.05) in atrial fibrillation. Systolic and diastolic left ventricular function, assessed by radionuclide angiography at rest, were not significantly diVerent. Peak ṼO 2 (mean (SD): 13.8 (3.6) v 17.1 (5.6) ml/kg/min; p < 0.01) and peak work load (78 (27) v 98 (36) W; p < 0.05) were lower in the patients with atrial fibrillation, though respiratory gas exchange ratio and Borg score were similar in the two groups. Patients with atrial fibrillation had a higher heart rate sitting at rest before exercise (93 (16) v 84 (16) beats/min) and at peak eVort (156 (23) v 140 (25) beats/min) (p < 0.05). Conclusions-Atrial fibrillation is associated with a 20% lower peak ṼO 2 in patients with chronic heart failure, suggesting that preserved atrial contraction or a regular rhythm, or both, are critical to maintain cardiac output and exercise performance.

In 1994, we ascertained the outcome of 143 hypertensive men in whom invasive hemodynamic measurements were performed at rest and during graded bicycle exercise during the period 1972-1982 to assess (1) which of the hemodynamic components of blood pressure is associated with the incidence of cardiovascular events and total mortality, and (2) whether the hemodynamic response to dynamic exercise adds prognostic precision to the data at rest. During 2186 patient years of follow-up, 38 patients suffered at least one fatal or nonfatal cardiovascular event and 17 patients died. Cox regression analysis showed that systolic pressure and systemic vascular resistance measured at rest, during submaximal exercise (50 W), and at peak effort were significant (P < .01) predictors of the age-adjusted incidence of cardiovascular events and total mortality. However, exercise blood pressure did not significantly predict the incidence of cardiovascular events over and above pressure at rest; by contrast, exercise systemic vascular resistance added prognostic precision to vascular resistance at rest (P < .01). As for total mortality, systolic pressure and systemic vascular resistance at peak exercise carried prognostic information that was independent of the results at rest (P < .05); this was not the case for measurements during submaximal exercise. We conclude that the prognostic importance of blood pressure is related to systemic vascular resistance. The prognostic precision of exercise pressure, on top of pressure at rest, is limited. Exercise systemic vascular resistance, however, provides prognostic information beyond that available from measurements at rest, particularly for the incidence of cardiovascular events.

Age, gender and/or some lifestyle factors significantly affect heart rate and various components of its variability in the supine position and in response to standing. The results are similar for autoregressive modelling and fast Fourier transform, but may differ according to the units in which the spectral components are expressed.

Background-Many studies have focused on the prognostic power of peak oxygen uptake (V O 2 ) in patients with chronic heart failure, but maximal exercise testing is not without risk. The purpose of the present study was, therefore, to assess the prognostic significance of the steepness of changes in ventilation and carbon dioxide output (V CO 2 ) during submaximal exercise in comparison with V O 2 . Methods and Results-The study population consisted of 284 adult heart transplant candidates who performed a graded maximal bicycle ergometer test with respiratory gas analysis. Using the respiratory data up to a gas exchange ratio of 1.0, 3 submaximal slopes were calculated in each patient. During follow-up (median, 1.33 years), 57 patients died and 149 had Ն1 cardiovascular event. When using Cox proportional hazards analysis, both peak V O 2 and submaximal respiratory slopes predicted outcome before and after accounting for age, sex, and body mass index. However, whereas the prognostic power of peak V O 2 was independent of submaximal respiratory data, the prognostic significance of the slopes was lost after controlling for peak V O 2 . Stepwise regression analysis even selected peak V O 2 as an independent prognostic index among the following factors: cause of heart failure, ejection fraction, pulmonary vascular resistance, natremia, and the forced expiratory volume in 1 s. Conclusions-Respiratory data during submaximal exercise are significant predictors of outcome in patients with chronic heart failure, but their prognostic power is inferior to that of peak V O 2 . However, these data may be useful when maximal exercise is contraindicated or not achievable.

Objective: The aim of this study was to investigate the effects of an acute exercise bout in the morning in the post-absorptive or postprandial state on the glycemic and insulinemic response to three standardized meals throughout the day. It is hypothesized that post-absorptive exercise enhances fat oxidation rate during exercise and thereafter attenuates the glucose and insulin response to subsequent meals. Research Methods and Procedures: Seven sedentary males with metabolic syndrome (age, 45 Ϯ 11 years; BMI, 34 Ϯ 3 kg/m 2 ) were studied in a crossover design comparing three conditions: no exercise, postprandial and post-absorptive exercise (at ϳ60% of the individual V O 2max for 45 minutes). Substrate use was evaluated by indirect calorimetry during exercise. Venous blood samples were taken at regular (30-to 60-minute) intervals throughout the day, and glucose, insulin, and triglyceride concentrations were determined. Results: During exercise, a higher fat oxidation rate was observed in the post-absorptive than the postprandial state. The glycemic response to a standardized high-carbohydrate breakfast was lower when exercising after breakfast than when exercising before breakfast. There was no effect of either exercise mode on glucose and insulin response to lunch and supper. Discussion: Post-absorptive exercise has the advantage of promoting fat use, whereas postprandial exercise can attenuate the glycemic response to breakfast. Neither exercise mode acutely induces improved glucoregulation later during the day. The impact of meal timing on the effects of regular exercise training on glycemic control in this population remains to be studied.