Relationship Between Athlete's Heart And Blunted Left Ventricular Untwist During Orthostasis

Abstract

It is known that the orthostatic tolerance is attenuated in the endurance athletes (Fit). We have shown that an impaired increase in left ventricular (LV) untwist against the orthostatic stress may be underlying mechanism of orthostatic intolerance in Fit. Although this impaired response of the LV untwist may be related to athlete’s heart, its details are still unclear. PURPOSE: To clarify cardiac function and morphology that would affect LV peak untwisting rate at the pre-syncope. METHODS: Twelve male college level competitive athletes (Fit, 23 ± 8 years old) and 12 male non-athletes (Unfit, 25 ± 5 years old) underwent maximal exercise test on a bicycle ergometer to assess maximal oxygen consumption (VO2max) and graded lower body negative pressure (LBNP) up to presyncope to assess a cumulative stress index (CSI) as a measure of orthostatic tolerance. LV end-diastolic volume/BSA (EDVi), end-systolic volume/BSA (ESVi), torsion, peak untwisting rate and sphericity index (LV length/ LV diastolic internal diameter) were evaluated by 3D speckle tracking echocardiography during the LBNP test. Pearson's correlation analysis was performed between peak untwisting rate and the other parameters of 3D echocardiography at the presyncope. In addition, multiple linear regression was performed between LV peak untwisting rate vs. age and the other parameters of 3D echocardiography. RESULTS: VO2max was higher (59 ± 4 vs. 36 ± 8 ml·kg-1·min-1, p < 0.05) and CSI was lower (1010 ± 472 vs. 1467 ± 596 mmHg·min, p < 0.05) in Fit than in Unfit. LV peak untwisting rate was slower in Fit than in Unfit at the presyncope ( -161 ± 51 vs. -245 ± 88 °/cm, p < 0.05). EDVi (r = 0.50, p = 0.013), ESVi (r = 0.58, p = 0.003), torsion (r = -0.57, p = 0.004) and sphericity index (r = -0.54, p = 0.007) were moderately related to LV peak untwisting rate. In multiple linear regression, torsion (β = -0.454, p = 0.029) and sphericity index (β = -0.454, p = 0.029) were independently correlated with LV peak untwisting rate. CONCLUSION: The more spherical LV was associated with the slower peak untwisting rate at the presyncope. This finding suggests that athlete’s heart is related with blunted increase in peak untwisting rate at the presyncope given that the athlete’s heart is characterized by a spherical shape of the heart.