Diastolic Ventricular Interactions in Endurance Athletes During Lower Body Positive and Negative Pressure

Abstract

Increased left ventricular (LV) compliance is one of many cardiovascular adaptations to aerobic exercise training. Enhanced LV compliance may lead to larger end-diastolic volumes and stroke volumes during exercise, ultimately allowing for greater aerobic performance. However, greater LV compliance may be detrimental during negative orthostatic stress, contributing to the reduced orthostatic tolerance seen in endurance athletes. Diastolic ventricular interactions may play an important role in determining LV compliance. Previous research has shown that the volume in one ventricle can directly influence the volume in the opposite ventricle during acute alterations of end-diastolic volume. PURPOSE: To simultaneously assess right (RV) and LV volumes during lower body positive (LBPP) and negative pressure (LBNP), and to compare the responses of endurance athletes with normally active individuals. METHODS: Eight male endurance athletes (VO2 max 65.4 ± 5.7 mL/kg/min) and eight normally active males (VO2 max 45.1 ±6.0 mL/kg/min) underwent three experimental days: 1) assessment of VO2 max, 2) an orthostatic tolerance test, and 3) LBPP (0 to +60 mmHg) and LBNP (0 to −80 mmHg) during which time echocardiographic assessment of LV and RV dimensions were made. ReSUlT S: Seven out of eight endurance athletes did not complete the orthostatic tolerance test due to signs of presyncope, whereas all of the normally active individuals completed the test. Echocardiographic analyses revealed that there were no group differences in the RV response to either LBPP or LBNP; both groups increased or decreased to the same extent. However, there was a differential group response in LV volume during lower body pressures (p<0.05). For example, during LBNP of-80 mmHg the endurance athletes had a reduction of end-diastolic volume of approximately 50 mL, whereas the normally active participants decreased by 25 mL. Conversely, during +60 mmHg the endurance athletes had an increase in LV end-diastolic volume of 25 mL compared to a 10 mL increase in the normally active individuals (p<0.05). CONCLUSIONS: The greater increase (or reduction) in LV volume found in the endurance athletes despite a similar group response in the RV indicates that less diastolic ventricular interaction occurred in the endurance athletes. Less interaction would contribute to the greater LV compliance found in endurance athletes. This finding may partially account for the ability of endurance athletes to utilize the Frank-starling mechanism to a greater extent during exercise, yet be less tolerant of negative orthostatic stress.