Ahletic adaptations of thin-walled structures of the heart: a cross-sectional echocardiographic study of elite athletes

Abstract Background Cardiac adaptation to exercise is characterized by eccentric remodeling due to increased volume load[1], it is however unclear how systolic function is affected in all chambers. Endurance sports is a known risk factor for later onset atrial fibrillation[2]. Moreover, recent studies of the acute effects of exercise have reported reversable right ventricular (RV) dilation and reduced function in triathletes resembling ARVC, while the left ventricle (LV) was unchanged[3]. These findings have raised concern regarding the long-term adaptations in the thin-walled chambers of the heart. Purpose The aim of the current study was to assess atrial and RV remodeling by echocardiography in elite athletes. Methods A cross-sectional study of 482 healthy active elite athletes from 30 sports was investigated with a standard resting echocardiogram. Using the Mitchell sports classification, athletes were grouped according to levels of endurance demands for their sport into low (Mitchel 1A), intermediate (Mitchel 1B-C, 2A-B-C), and high endurance demand (3A-B-C). All measures were adjusted for body surface area (BSA), sex, and age. Analysis of Covariance models was used to allow for adjustments for categorical variables and continuous covariates. Results Left atrial minimum volume/BSA (LAminV/BSA) was higher in athletes who performed high endurance demanding sports than in the intermediate and low groups (High: 11.3 ml/m2, confidence interval (CI): 10.1-12.5; Int: 8.9 ml/m2, CI: 8.3-9.5, p<0.01; Low: 7.7 ml/m2, CI: 5.8-9.7, p<0.01). We found no difference between the low and intermediate groups. RV systolic area/BSA (RVsysA/BSA) was significantly higher in the high and intermediate groups compared to the low group (high 9.5 ml/m2, CI: 9.1-9.8, p=0,014; Int 9.3 ml/m2, CI: 9.1-9.5, p=0.04; Low: 8.3 ml/m2, CI: 7.7-9.0). The LA/RV minimum size ratio showed a larger size difference between the groups in the LA compared to the RV (High 1.183, CI: 1.063-1.303; Int 0.968, CI: 0.906-1.029, p<0.01, Low 0.921, CI: 0.726-1.116 p=0.02). A comparison of LA and LV size (LAminV/LVsysV) showed a significant decrease between high and intermediate groups, but not the low group (High: 0.366; Int: 0.296, p<0.01; Low: 0.302, p=0.16). The LA/RA size ratio was equal in all groups. LA strain analysis showed reduced contraction in the high and intermediate groups compared to the low group (High -10.2, CI: -10.9-(-9.4), p<0,01, Int -10.6, CI: -11.1-(-10.2), p<0.01, Low: -12.9, CI: -14.2-(-11.6)), the same pattern was not found in RA function, RV freewall and LV GLS (table 1). Conclusion We found a bilateral increase in atrial size while LA (but not RA) also showed reduced contraction in athletes from intermediate and high endurance demanding sports. Athletes from sports with high and intermediate endurance demands exhibited dilated ventricles but no decreased function was detected. Adaptations of atrial size and function were more pronounced than that of either ventricle.Table 1:Population characteristicsTable 2:Echocardiographic measures