Cardiac adaptation to endurance exercise training: Differential impact of swimming and running

Lack of cardiac remodelling in elite endurance athletes: an unexpected and not so rare finding

PURPOSE

Endurance elite athletes are expected to present a cardiac remodelling, characterized by eccentric hypertrophy (EH), may be associated with higher sportive performances. However, not all can present a cardiac remodelling. The study aimed to identify endurance athletes without cardiac remodelling characterizing their physiologic and clinical features.

METHODS

We studied 309 endurance athletes (cycling, rowing, canoeing, triathlon, athletics, long-distance swimming, cross-country skiing, mid-long distance track, pentathlon, biathlon, long-distance skating and Nordic-combined) examined during period of training, by clinical evaluation, ECG, echocardiogram and exercise-stress test. Sport career achievements (Olympic\World championship medals or national\world records) were recorded.

RESULTS

EH was found in most of athletes, (n = 126, 67% of males; n = 85, 68.5% of females). A significant proportion,, exhibited normal geometry (NG) ( n = 59, 31.3% in males; n = 39, 31.4% in females). At stress test, significant differences between EH and NG athletes were found in peak power (317.1 ± 71.2W in NG vs. 342.2 ± 60.6W in EH, p = 0.014 in males and 225.1 ± 38.7W in NG vs. 247.1 ± 37W in EH, p = 0.003 in females), rest heart rate (66.1 ± 13 in NG vs. 58.6 ± 11.6 in EH, p = 0.001 in males and 68 ± 13.2 in NG vs. 59.2 ± 11.2 in EH, p = 0.001 in females) with similar ventricular extrasystoles (p = 0.363 in males and p = 0.492 in females). However, no significant differences in athletic achievements were registered.

CONCLUSION

Our study demonstrates a relatively high prevalence of NG in endurance athletes, in addition to the expected EH. Athletes with NG perform worse in exercise-stress test and exhibit some less advantageous functional heart characteristics. However, the type of heart geometry is not associated with negative clinical findings.

The athlete's heart: insights from echocardiography

The manifestations of the athlete's heart can create diagnostic challenges during an echocardiographic assessment. The classifications of the morphological and functional changes induced by sport participation are often beyond 'normal limits' making it imperative to identify any overlap between pathology and normal physiology. The phenotype of the athlete's heart is not exclusive to one chamber or function. Therefore, in this narrative review, we consider the effects of sporting discipline and training volume on the holistic athlete's heart, as well as demographic factors including ethnicity, body size, sex, and age.

Certainties and Uncertainties of Cardiac Magnetic Resonance Imaging in Athletes

Prolonged and intensive exercise induces remodeling of all four cardiac chambers, a physiological process which is coined as the “athlete’s heart”. This cardiac adaptation, however, shows overlapping features with non-ischemic cardiomyopathies, such as dilated, arrhythmogenic and hypertrophic cardiomyopathy, also associated with athlete’s sudden cardiac death. Cardiac magnetic resonance (CMR) is a well-suited, highly reproducible imaging modality that can help differentiate athlete’s heart from cardiomyopathy. CMR allows accurate characterization of the morphology and function of cardiac chambers, providing full coverage of the ventricles. Moreover, it permits an in-depth understanding of the myocardial changes through specific techniques such as mapping or late gadolinium enhancement. In this narrative review, we will focus on the certainties and uncertainties of the role of CMR in sports cardiology. The main aspects of physiological adaptation due to regular and intensive sports activity and the application of CMR in highly trained athletes will be summarized.

Cardiac remodeling in ambitious endurance-trained amateur athletes older than 50 years–an observational study

Background

Data on cardiac remodeling in veteran athletes are conflicting but of clinical importance.

Methods

Sixty-nine clinically stable and healthy individuals >50 years were identified (median 55 (IQR 52–64), 26% female). Echocardiographic features were identified in individuals, who have performed endurance sports at 70% of their maximum heart rate for at least 1 hour 3 times/ week over the previous 5 years.

Results

Median training time in all participants was 6 hours per week. Therefore, based on these 6 hours of weekly training, participants were grouped into 45 ambitious endurance-trained amateur athletes (EAA) and 24 recreationally active endurance-trained athletes (RAP) training ≥6 hours (6–10) and <6 hours (3.5–5), respectively. Left ventricular (LV) diameters were slightly larger in EAA than in RAP (27 mm/m² (25–28) vs. 25 mm/m² (24–27), p = 0.023) and EAA showed preserved diastolic function (p = 0.028) with lower E/E’ ratio (7 (6–9) vs. 9 (7–10), p = 0.039). Interventricular septal thickness and relative wall thickness ratio were similar. Global right ventricular and LV strain were similar, but left atrial (LA) reservoir strain was higher in EAA than in RAP (27% (22–34) vs. 20% (15–29), p = 0.002).

Conclusions

Endurance training in healthy athletes >50 years is not associated with chamber dilatation or LV hypertrophy. A weekly training duration of ≥6 hours seems beneficial to preserve diastolic function associated with an increased LA reservoir function.

Cardiac and Pulmonary Vascular Remodeling in Endurance Open Water Swimmers Assessed by Cardiac Magnetic Resonance: Impact of Sex and Sport Discipline

Background: The cardiac response to endurance exercise has been studied previously, and recent reports have described the extension of this remodeling to the pulmonary vasculature. However, these reports have focused primarily on land-based sports and few data are available on exercise-induced cardio-pulmonary adaptation in swimming. Nor has the impact of sex on this exercise-induced cardio-pulmonary remodeling been studied in depth. The main aim of our study was to evaluate cardiac and pulmonary circulation remodeling in endurance swimmers. Among the secondary objectives, we evaluate the impact of sex and endurance sport discipline on this cardio-pulmonary remodeling promoted by exercise training.

Methods:Resting cardiovascular magnetic resonance imaging was performed in 30 healthy well-trained endurance swimmers (83.3% male) and in 19 terrestrial endurance athletes (79% male) to assess biventricular dimensions and function. Pulmonary artery dimensions and flow as well as estimates of pulmonary vascular resistance (PVR) were also evaluated.

Results:In relation to the reference parameters for the non-athletic population, male endurance swimmers had larger biventricular and pulmonary artery size (7.4 ± 1.0 vs. 5.9 ± 1.1 cm², p < 0.001) with lower biventricular ejection fraction (EF) (left ventricular (LV) EF: 58 ± 4.4 vs. 67 ± 4.5 %, p < 0.001; right ventricular (RV) EF: 60 ± 4 vs. 66 ± 6 %, p < 0.001), LV end-diastolic volume (EDV): 106 ± 11 vs. 80 ± 9 ml/m², p < 0.001; RV EDV: 101 ± 14 vs. 83 ± 12 ml/m², p < 0.001). Significantly larger LV volume and lower LV EF were also observed in female swimmers (LV EF: 60 ± 5.3 vs. 67 ± 4.6 %, p = 0.003; LV EDV: 90 ± 17.6 vs. 75± 8.7 ml/m², p = 0.002). Compared to terrestrial endurance athletes, swimmers showed increased LV indexed mass (75.0 ± 12.8 vs. 61.5 ± 10.0 g/m², p < 0.001). The two groups of endurance athletes had similar pulmonary artery remodeling.

Conclusions: Cardiac response to endurance swimming training implies an adaptation of both ventricular and pulmonary vasculature, as in the case of terrestrial endurance athletes. Cardio-pulmonary remodeling seems to be less extensive in female than in male swimmers.