Heart and Sports – a Never-Ending Story

Herbert Reindell from Freiburg set a sports cardiological milestone in 1960 with his monograph „Heart, Circulatory Diseases and Sports“ (10). As a clinical cardiologist with personal involvement in sports, he recognized and scientifically investigated the physiological and pathophysiological interactions between cardiology and sports medicine at an early stage. In 1985, his student and colleague Joseph Keul succeeded in establishing a working group on „ Sports Medicine“ in the German Society for Heart and Circulation Research, now the German Cardiac Society (GCS). The topic of the first session was „Physical exercise in patients following heart surgery.“

„The working group “Physical Exercise Tolerance in non-coronary Heart Diseases” was established in 1995 by the GCS. The speakers were Hans-Hermann Dickhuth from Tübingen and Wilfried Kindermann from Saarbrücken. In constructive cooperation with Gunther Arnold, the GCS Director at that time, the new AG32 “Sports Cardiology” was successfully founded in 2005. Jürgen Scharhag from Saarbrücken, now Vienna, has contributed substantially to the establishing of AG32, both in terms of organization and content. The first meeting, which took place during the Spring conference of the GCS in 2006, dealt with cardiovascular preparticipation screenings and was held in an over-filled auditorium (figure 1).

The cooperation between cardiology and sports medicine peaked in the additional qualification „Sports Cardiology“. The three-level qualification is a cooperation between the GCS and the German Association for Sports Medicine and Prevention (DGSP). Physical activity and sports require cardiological and sports-medical expertise in both primary and secondary prevention as well as in high-performance sports. The sports cardiological care should be optimized on the basis of uniform standards. What began with Reindell more than half a century ago has now reached a provisional formal conclusion.

From a content viewpoint, a lot has happened in the meantime. The preventive effect of regular physical activity, including the criteria to be met, is now well-proven (Level IA). Sports Cardiology has also profited from the further development of imaging diagnostics. On the other hand, findings were generated of which the dignity was sometimes a matter of controversial discussion. Molecular-genetic examinations have simplified the risk assessment of various cardiac diseases, molecular autopsies help in explaining sudden cardiac deaths in sports.

Sports cardiological studies/recommendations of recent years are noted as examples and as pars pro toto. Although most physiological changes in the ECG of athletes were already described by Reindell in 1960, the published international recommendations for the interpretation of athlete’s ECGs (11) have practical relevance, especially with respect to misdiagnoses. Several consensus recommendations had been made earlier to decrease the rate of false-positive findings. The more frequent repolarization changes in black athletes have also been also included. Analogous to the ECG, left-ventricular hypertrophy is also more pronounced in black athletes than in whites (5, 8).

The current guidelines of the European Society of Cardiology (ESC) 2020 for Sports Cardiology (9) are less restrictive than the earlier ones. Patients/athletes should be involved in the decisions („shared decision making“). I overlook nearly six decades as a physician and have yet to see patients on strict bed rest for six weeks after a heart attack. Today that would be malpractice. Meanwhile, even high-performance sports are permitted in some heart diseases under certain conditions.

In some heart diseases, one could even speak of a paradigm change. This applies for example to hypertrophic cardiomyopathy (HCM), which was considered earlier as an absolute contraindication for high-performance sports. Remember the HCM of the former national soccer player Gerald Asamoah, whose permission to play was discussed back and forth in both lay and medical media for years. Meanwhile there are smaller studies which have apparently led to cautious opening. A positive genotype is no longer considered as contraindication in phenotypical negative athletes. In contrast, in arrhythmogenic cardiomyopathy, competitive sports remain prohibited, as this can accelerate the course of the disease. The sports break after myocarditis used to be almost dogmatically set at six months. The currently recommended individualized procedure can result in a marked shortening of the break.

The corona pandemic led to a general uncertainty, medically as well. Sports cardiological expertise was needed; the pandemic cut a swath across sports. Movement, leisure sport activities and high-performance sports all suffered. After initial sports-medical overprotection, the realization grew that physically fit persons tolerated the infection better. There is no evidence of a greater cardiac involvement in athletes. Even the initially assumed high numbers of myocarditis, induced by the corona virus, could not be confirmed later. Most of the corona infections were asymptomatic or mild. After two years of scientific and practical knowledge, earlier recommendations were revised. Only a three-day break from sports is recommended after diagnosis or absence of
symptoms (13).

What remains to be done in the future? From the multitude of challenges in sports cardiology, a few should be briefly mentioned. The terms „athletes“ or even „elite athletes“ are still used generously, even in publications of high-ranking journals (1). Not everyone engaging in competitive sports can be categorized like this. Prerequisite should be participation in at least interregional championships, in the ideal case (elite athletes) in national/international championships up to the Olympic Games. The required athletic performance demands high training volumes and intensities, which in many sports leads to maximum physiological adaptations. Competitive sports at a lower level do not always meet these conditions. The second essential criterion is the type of sports. Endurance sports (prototype distance running) and strength sports (prototype weight lifting) are the limits of the sport-type spectrum. From a cardiological point of view, attention to these criteria facilitates differentiation of physiological from pathological changes. Findings from studies with mixed athlete populations should be interpreted with caution. In studies with exclusively elite athletes, the number of participants is limited a priori.

The exercise ECG, a domain of sports medicine, has lost ground in this millennium. Current guidelines downgrade exercise ECG in the noninvasive diagnostics of coronary heart disease or chronic coronary syndrome (6). It is not surprising that modern imaging procedures have overtaken the exercise ECG in the diagnostics of ischemia. But at what price? From an economical point of view, a coronary CT cannot be first-line diagnostics as part of primary prevention. The especially lower sensitivity of the exercise ECG (12) should heighten our awareness to perform additional diagnostic measures, despite a negative finding, when a corresponding clinical suspicion is given.

But the exercise ECG is more than an ischemia test. Ventricular arrhythmias have been described with a frequency of 5% despite normal anamnesis, clinical finding and resting ECG (14) and can indicate an arrhythmogenic myocardial substrate. Furthermore, blood pressure behavior in exercise is an important indication in the diagnostics of hypertension. A recently published study reported on the prevalence of exercise hypertension among athletes of 6.8-19.6% (4). There are sufficient grounds to predict that the exercise ECG will retain its value. However, prospective longitudinal studies are missing to evaluate the cardiovascular risk of exercise-induced arrhythmias and hypertensive blood pressure increase in athletes.

Is extensive endurance sport healthy? More coronary calcification and myocardial fibrosis among endurance athletes, especially marathon runners (2, 3); these were alarming messages at first. The atherosclerotic plaques in the coronary vessels of athletes are mostly calcified, that is more stable, so that the risk of a plaque rupture is probably lower. Plaque stabilization is compared to the effect of statins. A ten-year observational study on men of various ages found that the participants who were most active in sports had the lowest mortality, independent of coronary calcification (7). The causes of increased coronary calcification and fibrosis in endurance athletes can so far only be speculated. A subclinical myocarditis is assumed as a possible cause of non-ischemic myocardial fibrosis. The clinical relevance of the focal fibrosis demonstrated in the cardio-MRT is doubted (2). Thus far there is no evidence that excessive endurance training results in an increase in all-cause or cardiovascular mortality. Considerable research is needed with respect to the mechanisms and their prognostic relevance. As Baggish so aptly put it, there are „…more questions than answers“(2).

There is plenty to do in sports cardiology. With the newly-created additional qualification, cardiological know-how can be effectively combined with sports-medical experience in high-performance sports, including the development of study designs.