Abstract
Exercise stress tests have been used for the diagnosis of pulmonary hypertension, but with variable protocols and uncertain limits of normal. The pulmonary haemodynamic response to progressively increased workload and recovery was investigated by Doppler echocardiography in 25 healthy volunteers aged 19-62 yrs (mean 36 yrs). Mean pulmonary artery pressure ((Ppa)) was estimated from the maximum velocity of tricuspid regurgitation. Cardiac output (Q) was calculated from the aortic velocity-time integral. Slopes and extrapolated pressure intercepts of (Ppa)-Q plots were calculated after using the adjustment of Poon for individual variability. A pulmonary vascular distensibility alpha was calculated from each (Ppa)-Q plot to estimate compliance. (Ppa) increased from 14+/-3 mmHg to 30+/-7 mmHg, and decreased to 19+/-4 mmHg after 5 min recovery. The slope of (Ppa)-Q was 1.37+/-0.65 mmHg x min(-1) x L(-1) with an extrapolated pressure intercept of 8.2+/-3.6 mmHg and an alpha of 0.017+/-0.018 mmHg(-1). These results agree with those of previous invasive studies. Multipoint (pa)-Q plots were well described by a linear approximation, from which resistance can be calulated. We conclude that exercise echocardiography of the pulmonary circulation is feasible and provides realistic resistance and compliance estimations. Measurements during recovery are unreliable because of rapid return to baseline.