Exercise-induced Changes in Cardiac Function & Morphology

Overview

Until now it has been assumed that regular endurance training has a positive influence on cardiac function and that the positive effect increases with increasing intensity. However, little is known about the effects of intense endurance stress on the heart. According to current knowledge repeated exposure to strenuous endurance activity may lead to minor but possibly irreversible damage to the heart with resultant scarring of the heart's muscle. Within this study we attempt to find out by different analytical methods - in particular magnetic resonance imaging (MRI) and ultrasound of the heart - to what extent the heart muscle is affected by an intense endurance exercise, i.e. the "Jungfrau-Marathon", and which changes can possibly be found. Due to repeated measurements we will obtain further information on the short-term course of possible changes. Hypotheses: A single bout of prolonged strenuous exercise (PSE) leads to transient alteration in cardiac function accompanied by the appearance of biomarkers for myocardial damage.

Background Despite the well documented cardio-protective effects of aerobic exercise of moderate intensity, short- and long-term consequences of strenuous exercise are less clear. There is increasing evidence that maintaining a high cardiac workload over a prolonged duration may result in transient impairment of cardiac function. Recent studies have also reported a transient increase in cardiac biomarkers after prolonged strenuous exercise. While in patients with cardiac disease the presence of cardiac dysfunction and increased cardiac biomarkers generally reflects myocardial damage, the impact of these observations in athletes is ill defined. It is a matter of concern whether in athletes such findings simply reflect a reversible response or whether repetitive events may lead to an accumulative cardiac damage. Traditional echocardiographic methods used to determine potential cardiac changes in morphology or function are investigator-dependent and may be subject to interference by cardiac pre- and afterload. Cardiac magnetic resonance imaging provides an investigator-independent and objective method to quantify cardiac dimensions and function. Delayed contrast enhancement MR imaging is a highly reproducible cardiovascular magnetic resonance imaging technique to directly visualize myocardial edema, necrosis and fibrosis. Objective To use cardiac and delayed contrast enhancement magnetic resonance imaging in combination with echocardiographic methods to quantify cardiac dysfunction after a single competitive PSE event and to study post-exercise changes in morphology and function as well as the post-exercise dynamics of specific markers of myocardial damage. Methods Cardiac and delayed contrast enhancement magnetic resonance imaging will be used in combination with echocardiographic methods to repetitively investigate post-exercise cardiac function and morphology in 10 elite athletes finishing the "Jungfrau Marathon". Biomarkers of myocardial damage are assessed simultaneously. Post-exercise dynamics of the outcome parameters are followed over a minimum of 7 days after the exercise.