The relationship between the components of pulmonary artery pressure remains constant under all conditions in both health and disease.

BACKGROUND: The relationships among systolic pulmonary artery pressure (SPAP), diastolic pulmonary artery pressure (DPAP), and mean pulmonary artery pressure (MPAP) have been found to be constant in humans breathing air, at rest, while supine. It would be important for those studying the pulmonary circulation if this relationship were maintained under other circumstances, such as change in posture, during exercise, or after pharmacologic manipulation. In particular, it would be useful if the relationship were maintained when treating pulmonary hypertension because this would allow different methods of measurement to be compared, such as SPAP from echocardiography and MPAP from right heart catheterization. METHODS: Data were reviewed from both healthy subjects and those with pulmonary hypertension (n = 65) who had a micromanometer-tipped, high-fidelity pulmonary artery catheter inserted for between 6 and 36 h in the Scottish Pulmonary Vascular Unit between 1997 and 2003. The 5-min averages, while the patient was supine at rest, were analyzed by linear regression to compare the response of SPAP and DPAP with MPAP. RESULTS: There were linear relationships (measured in millimeters of mercury) of SPAP with MPAP (SPAP = 1.50 MPAP + 0.46), and DPAP with MPAP (DPAP = 0.71 MPAP - 0.66). These were maintained with a high degree of accuracy following changes in posture and activity. CONCLUSIONS: SPAP, MPAP, and DPAP were strongly related, and these relationships were maintained under varying conditions. This finding will allow comparison between invasive and noninvasive descriptions of pulmonary hemodynamics found in the literature.

Pulmonary arterial pulse pressure and mortality in pulmonary arterial hypertension.

In the Framingham studies, systemic arterial pulse pressure correlated linearly with morbidity and mortality. Right ventricular (RV) systolic dysfunction and pulmonary circulation stiffening result in abnormalities of pulmonary arterial (PA) pulse pressure in PA hypertension (PAH). We investigated the prognostic potential of PA pulse pressure in 67 patients with PAH diagnosed between January 1996 and March 2004 (33 idiopathic PAH, 34 PAH-connective tissue disease). The population was arbitrarily divided into tertiles of PA pulse pressure (= systolic-diastolic PA pressure) and 5-year mortality was assessed using the Kaplan-Meier method. The extent of RV systolic dysfunction and pulmonary circulation stiffening within each tertile was assessed by comparing the mean cardiac index and alpha (a recently described measure of pulmonary circulation distensibility) in each. Independent predictors of mortality were identified by Cox regression. Five-year mortality rates in patients with low, intermediate and high pulse pressures were 40%, 91% and 54%, respectively. Pulse pressure did not independently predict mortality, but cardiac index, 6-min walk test distance and mixed venous oxygen saturation did. Pulse pressure correlated with circulation stiffening (alpha) but did not correlate with cardiac index which tended to be lower in patients with intermediate pulse pressure and high mortality. PA pulse pressure correlated with pulmonary circulation stiffening but did not predict mortality in this study. RV dysfunction provided better prognostic information and probably explains the higher mortality seen in patients with intermediate pulse pressure.