THE RELATIONSHIP OF RIGHT VENTRICULAR SYSTOLIC TO PULMONARY ARTERY SYSTOLIC PRESSURE DURING EXERCISE IN HEALTHY OLDER ADULTS

Abstract

There is renewed interest in the study of hemodynamic responses during aerobic exercise to understand the relationship between pulmonary arterial or venous hypertension and exertional breathlessness. A recent observation demonstrates that a systolic pressure gradient between the right ventricle (RV) and the pulmonary artery (PA) may develop with upright exercise in symptomatic patients. This has implications for the accuracy of quantitative methods to assess RV wall stress or PA hemodynamics. In this study we tested the hypothesis that an RV-PA gradient develops during exercise in healthy adults and examined its hemodynamic determinants. We studied healthy untrained (n = 10) and athletic (n = 5) older adults (mean age = 55±5 years) at rest and during exercise, using right-heart catheterization to measure RV and PA pressures simultaneously, as well as thermodilution cardiac output (CO). Subjects were studied at rest in the supine position, as well as on a cycle ergometer in a 25° semi-upright position and at 2 stages of submaximal exercise. Simultaneous RV and PA pressure tracings were analyzed offline over 8-10 beats, sampled within 1 minute of CO measurement. From these tracings, RV (RVSP) and PA (PASP) systolic pressures were measured. Pulmonic valve peak (PG) and mean (MG) gradients were also measured, as was mean right atrial pressure (RAP). Valve flow was calculated and the pulmonic valve orifice area was estimated by the Gorlin formula. The systolic tricuspid valve gradient (TG) was calculated as [RVSP – RAP]. No significant pulmonic valve gradients were observed at rest, and calculated valve area was 3.6±1.0 cm2. Both RVSP and PASP increased from semi-upright rest to light exercise, although the increase in RVSP was proportionately greater, and pulmonic valve gradients increased (Table 1). RVSP trended modestly upward with moderate exercise, but PASP did not, and so pulmonic valve gradients trended toward increase further at moderate exercise. The TG increased in keeping with RVSP, and so did not track the stability of PASP from light to moderate exercise (Figure 1). In healthy adults without pulmonic stenosis, RVSP and PASP dissociate during exercise stress. During moderate intensity exercise, the peak-to-peak RV-PA gradient exceeded 17 mmHg in over half of cases. This observation suggests that sonographic estimation based on the tricuspid regurgitation jet velocity may overestimate PASP as flow increases during exercise.View Large Image Figure ViewerDownload Hi-res image Download (PPT)