PULMONARY PRESSURE RESPONSE TO SUBMAXIMAL EXERCISE IN MIDDLE-AGED ENDURANCE ATHLETES

The importance of right ventricular (RV) function in both health and disease is increasingly recognized, and the ‘athletic heart’ is of particular interest, in light of recent observations of disproportionate RV remodeling in endurance athletes. RV afterload can be assessed by calculating the pulmonary vascular resistive and pulsatile components, resistance (Rp) and compliance (Cp) respectively. The relationship between Rp and Cp are also affected by the pulmonary artery wedge pressure (PAWP). It has been suggested that pulmonary artery (PA) pressures increase approximately linearly with cardiac output as exercise intensity increases. However, directly-measured pulmonary hemodynamic data to support this hypothesis are sparse. Accordingly, our objective was to directly measure the response of PA hemodynamics to submaximal exercise in endurance-trained athletes. We studied 16 healthy endurance-trained athletes (54±6 years) who underwent exercise right-heart catheterization. PA systolic, diastolic, and mean pressures (PASP, PADP and mPAP, respectively) and PAWP were directly measured. Participants were studied on a semi-upright cycle-ergometer at rest and during consecutive 8-10 minute stages of steady-state exercise at an intensity eliciting heart rates of 100 bpm (EX1), 130 bpm (EX2), and 150 bpm (EX3). Pressure tracings were analyzed offline. PAWP was indexed to work rate (PAWR), and expressed relative to body weight (PAWRwt). We calculated the ratio of the transpulmonary gradient (TPG) to pulmonary pulse pressure (PP) multiplied by R-R interval as an index of steady-flow to pulsatile-flow arterial load (RpCp-time). Pulmonary pressures increased significantly at the onset of exercise, without further rise as exercise intensity progressed (Figure 1). PAWP also increased from CON to EXI with no further change at EX2 and EX3. PAWR and PAWRwt demonstrated a significant decrease from EX1 to EX2 that was sustained for EX3 (Table 1). Despite progressive increases in systemic pulse pressure with increasing exercise intensity, pulmonary pulse pressure rose at EX1 and remained stable through EX2 and EX3. RpCp-time decreased at EX1 without any further change for EX2 and EX3. We observed a remarkably constant PA and PAWP pressure response to increasing submaximal exercise intensity, with a stable change in RpCp-time. These observations in exercise hemodynamics suggest the ability of the PA and pulmonary venous, along with left atrial compartments, to accommodate high conduit flows. These responses appear to limit marked increases in the pulsatile RV afterload during exercise in this population of highly trained, middle-aged endurance athletes.View Large Image Figure ViewerDownload Hi-res image Download (PPT)