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

Clinical applications of intra-cardiac four-dimensional flow cardiovascular magnetic resonance: A systematic review

Background: Four-dimensional flow cardiovascular magnetic resonance (4D flow CMR) is an emerging non-invasive imaging technology used to visualise and quantify intra-cardiac blood flow. The aim of this systematic review is to assess the literature on the current clinical applications of intra-cardiac 4D flow CMR. Methods: A systematic review was conducted to evaluate the literature on the intra-cardiac clinical applications of 4D flow CMR. Structured searches were carried out on Medline, EMBASE and the Cochrane Library in October 2016. A modified Critical Skills Appraisal Programme (CASP) tool was used to objectively assess and score the included studies. Studies were categorised as ‘highly clinically applicable’ for scores of 67–100%, ‘potentially clinically applicable’ for 34–66% and ‘less clinically applicable’ for 0–33%. Results: Of the 1608 articles screened, 44 studies met eligibility for systematic review. The included literature consisted of 22 (50%) mechanistic studies, 18 (40.9%) pilot studies and 4 (9.1%) diagnostic studies. Based on the modified CASP tool, 27 (62%) studies were ‘highly clinically applicable’, 9 (20%) were ‘potentially clinically applicable’ and 8 (18%) were ‘less clinically applicable’. Conclusions: There are many proposed methods for using 4D flow CMR to quantify intra-cardiac flow. The evidence base is mainly mechanistic, featuring single-centred designs. Larger, multi-centre studies are required to validate the proposed techniques and investigate the clinical advantages that 4D flow CMR offers over standard practices