Exercise physiology and cardiac function. Aspects on determinants of maximal oxygen uptake

Although the athlete's heart has been of interest for over 100 years, further characterization of the athletes heart is needed in order to understand how training affects cardiac dimensions and function. Few studies have investigated the effects of training in female athletes and few have compared males and females. Therefore, the aim of this thesis was to characterize the physiologically enlarged athlete's heart and the healthy respiratory response to exercise in both males and females, in order to facilitate the differentiation between the physiologically enlarged heart and the pathologically enlarged heart. Paper I showed that the total heart volume (THV) increases with training in both males and females, with a balanced enlargement of the left and right ventricle. Furthermore, THV was a strong, independent predictor of peak oxygen uptake (VO2peak). Males had a larger left ventricular mass (LVM) normalized to THV when compared to females of similar fitness level. In Paper II, THV in relation to VO2peak was compared between 31 patients diagnosed with heart failure and a control group consisting of athletes and normal subjects. The ratio between VO2peak and THV (VO2peak/THV) was defined as the cardiac reserve index. Cardiac reserve index was significantly lower in patients when compared to athletes and controls. This difference also remained when only patients with normal ejection fraction were compared with the control group. Paper III investigated three different respiratory indices (Dx, Px and Pq) in triathletes and controls. The sequence in which the indices occurred during an incremental exercise test differed between well trained and untrained subjects. This difference was shown to be caused by the well trained subjects' ability to metabolize fat at high workloads. In Paper IV cardiac pumping mechanics was compared between athletes and controls matched for age and gender. Cardiac pumping was divided into longitudinal pumping and radial pumping. Except for the longitudinal contribution to the left ventricular stroke volume in males, the results of Paper IV showed that there were essentially no difference in cardiac pumping mechanics between males and females, and between athletes and controls. This emphasizes the results from Paper I that it is the total heart volume that is the dominant determinant for cardiac performance

Left ventricular AV-plane displacement is preserved with lifelong endurance training and is the main determinant of maximal cardiac output.

Age-related decline in cardiac function can be prevented or postponed by lifelong endurance training. However, effects of normal ageing as well as of lifelong endurance exercise on longitudinal and radial contribution to stroke volume are unknown. The aim of this study was to determine resting longitudinal and radial pumping in elderly athletes, sedentary elderly and young sedentary subjects. Furthermore, we aimed to investigate determinants of maximal cardiac output in elderly

Peak oxygen uptake in relation to total heart volume discriminates heart failure patients from healthy volunteers and athletes

Background: An early sign of heart failure (HF) is a decreased cardiac reserve or inability to adequately increase cardiac output during exercise. Under normal circumstances maximal cardiac output is closely related to peak oxygen uptake (VO(2)peak) which has previously been shown to be closely related to total heart volume (THV). Thus, the aim of this study was to derive a VO(2)peak/THV ratio and to test the hypothesis that this ratio can be used to distinguish patients with HF from healthy volunteers and endurance athletes. Thirty-one patients with HF of different etiologies were retrospectively included and 131 control subjects (60 healthy volunteers and 71 athletes) were prospectively enrolled. Peak oxygen uptake was determined by maximal exercise test and THV was determined by cardiovascular magnetic resonance. The VO(2)peak/THV ratio was then derived and tested. Results: Peak oxygen uptake was strongly correlated to THV (r(2) = 0.74, p < 0.001) in the control subjects, but not for the patients (r(2) = 0.0002, p = 0.95). The VO(2)peak/THV ratio differed significantly between control subjects and patients, even in patients with normal ejection fraction and after normalizing for hemoglobin levels (p < 0.001). In a multivariate analysis the VO(2)peak/THV ratio was the only independent predictor of presence of HF (p < 0.001). Conclusions: The VO(2)peak/THV ratio can be used to distinguish patients with clinically diagnosed HF from healthy volunteers and athletes, even in patients with preserved systolic left ventricular function and after normalizing for hemoglobin levels