EFFECTS OF RESPIRATION ON SIZE AND FUNCTION OF THE ATHLETIC HEART

This study compares the effects of quiet breathing on the heart structure and function of pentathlon athletes (n = 11) and a less-conditioned control group (n = 12). Two-dimensional echocardiography was employed to direct an M-mode beam through the heart to minimize measurement errors due to respiratory motion of the heart. Respiration was simultaneously recorded with M-mode echocardiograms from a minimum of five respiratory and an average of 25 cardiac cycles. Athletes had greater (p < 0.01) end-diastolic transverse dimensions (10%), and interventricular septal and left ventricular posterior wall thicknesses (25%). During inspiration right ventricular internal end-diastolic dimensions increased (8 vs 12%) and left ventricular end-diastolic dimension (LVIDd) decreased (7 vs 8%) in athletes and controls, respectively. Although significant reciprocal changes in LVIDd (p < 0.01) occurred during respiration, no respiratory change was noted in the transverse diameter of the heart, interventricular septal, posterior wall thickness, LV end-systolic volume or ejection fraction. Inspiration caused a 21% fall (p < 0.01) in LV stroke volume in both groups. Eighty-four to 92% of the inspiratory decrease in LV stroke volume in the subjects studied could be attributed to ventricular interdependence; no significant interaction was found between level of conditioning and respiration.