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 less than 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 less than 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 less than 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.