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Pulmonary hypertension has been defi ned previously as a mean pulmonary artery pressure (mPAP) . 25 mm Hg at rest and . 30 mm Hg dur ing exercise. 1,2 Exercise measurements were withdrawn from the hemodynamic defi nition of pulmonary hypertension at an expert consensus conference held in 2008 in Dana Point. 3 This decision was based mainly on an analysis of the reported invasive pulmonary hemodynamic studies in healthy subjects at exercise revealing uncertainty about the exact upper limits of normal. 4 In the meantime, exercise-induced pulmonary arterial hypertension was validated as a clinical entity. 5 Thus, a robust defi nition of the limits of normal of the pulmonary circulation at exercise would be of great relevance. However, for ethical and practical reasons, it is unlikely that a large number of rightsided heart catheterizations in healthy subjects will be reported in the near future. Therefore, there is currently interest in noninvasive exercise stress echocardiography of the pulmonary circulation. 6 We previously reported a preliminary study on the feasibility of noninvasive echo-Doppler measurements of the normal pulmonary circulation at rest and at exercise. 7 From multipoint mPAP-fl ow coordinates in 25 healthy adults, we recovered pulmonary vascular resistance (PVR) and distensibility calculations

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 a 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?min -1 ?L -1 with an extrapolated pressure intercept of 8.2¡3.6 mmHg and an a of 0.017¡0.018 mmHg -1 . These results agree with those of previous invasive studies. Multipoint Ppa-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. KEYWORDS: Echocardiography, exercise stress test, pulmonary arterial compliance, pulmonary hypertension, pulmonary vascular resistance P ulmonary arterial hypertension (PAH) is currently defined by a mean pulmonary artery pressure (P pa) of .25 mmHg, a left atrial pressure (Pla) f15 mmHg and a pulmonary vascular resistance (PVR) of .3 Wood units [1]. Previous definitions included P pa of .30 mmHg at exercise [2], but this has been abandoned because of uncertain limits of normal and unknown symptomatic relevance.Recently, however, TOLLE et al.[3] reported on exercise-induced PAH as a new clinical entity, characterised by a sharp increase in P pa of .30 mmHg as a cause of decreased exercise capacity. In that study, haemodynamic measurements were presented as log-log plots of P pa as a function of oxygen uptake (V9O 2 ), with plateau patterns typical of PAH and takeoff patterns representing a normal response. Since V9O 2 is related to cardiac output (Q), these patterns would appear at variance. Numerous studies have shown multipoint P pa-Q plots to be best described by linear or slightly curvilinear approximations [4,5]. REEVES et al.[6] modelled P pa as a function of Q invasively measured in exercising normal volunteers, and indeed found a slight curvilinearity which they explained by the natural distensibility of the resistive pulmonary arterioles.Even though the procedure has still not been validated, Doppler echocardiography is a recommended screening test for PAH [1,2] and has been used in combination with exercise for the diagnosis of overt or latent PAH [7]. A systolic pulmonary artery pressure (Ppa,sys) of 40 mmHg is usually taken as the upper limit of ...