P839Independent association of sinus bradycardia and three-dimensional increased myocardial systolic deformation in athletes

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Purpose: To assess features and determinants of supernormal contractility of the athlete's heart by using real-time 3-D echocardiography (RT3DE) in a population including both top-level athletes and normals.Methods: Twenty top-level competitive rowers (R) and 20 healthy young controls (C), matched for age (28 ± 6 years and 28 ± 8 years respectively) underwent RT3DE assessment of left ventricular (LV) structure and function. Attention was provided to obtain a frame rate of at least 40% of the individual heart beating during the full volume recording. For this reason, consecutive 4-beat ECG-gated subvolumes were acquired during apnea (multibeat acquisition) to generate the full-volume. Care was also taken to encompass the entire LV cavity and wall in the data set. LV end-diastolic volume, LV end-systolic volume and ejection fraction (EF), sphericity index, LV mass index (LVMi), global longitudinal strain (GLS), global circumferential strain (GCS), global area strain (GAS) and global radial strain (GRS) were determined off-line.Results: The 2 groups were comparable for body mass index and diastolic blood pressure while systolic blood pressure was higher (p<0.002) and heart rate lower (p<0.005) in R. LV end-diastolic volume and LV end-systolic volume were greater in R (both p<0.0001), without significant difference of EF and sphericity index. LVMi was higher in R (75 ± 7 g/m2) than in C (66 ± 7 g/m2) (p<0.0001). GLS (-23.8 ± 3% in R and -21 ± 3% in C, p<0.005) and GAS (-36.7 ± 5% vs. -33.2 ± 4%, p<0.01) were higher in R than in C, while GCS and GRS did not differ significantly between the 2 groups. In the pooled population heart rate was inversely related with LVMi (r = -0.49, p<0.0001) and both GLS (r = -0,43, p<0.005) and GAS (r = -0.34, p<0.01). After adjusting for body mass index, systolic blood pressure and LVMi by separate multiple linear regression analyses, heart rate was an independent contributor of both GLS (standardized β coefficient = -0.44, p=0.008) (cumulative R2 =0.22, p<0.02) and of GAS (standardized β coefficient = -0.37, p=0.03) (cumulative R2 = 0.20, p<0.05).Conclusions: Real time 3-D echocardiography allows to identify an inverse association between heart rate and myocardial deformation in the athlete's heart. In absence of significant changes of ejection fraction, both global longitudinal strain and area strain are increased at rest in rowers. Bradycardia sustains also the increase of LV mass but its effect on components of systolic deformation is independent on LV hypertrophy.

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