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Degree of Reduction in Functional Pulmonary Microvascular Surface Area in Pulmonary Arterial Hypertension Related to CTD is Proportional for Two Pulmonary Metabolic Activities

SE Orfanos

David Langleben

J. Dupuis

A. M. Hirsch

M. Baron

J. L. Senecal

M. Giovinazzo

J. D. Catravas


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Conference: 2008 International PHA Conference and Scientific Sessions

Release Date: 06.20.2008

Presentation Type: Abstracts

Orfanos S.E., Langleben D., Dupuis J., Hirsch A. M., Baron M., Senecal J.L., Giovinazzo M., Catravas J.D.

Jewish General Hospital, Canada, Attikon Hospital, Greece, Montreal Heart Institute, Canada, Hopital Notre Dame - CHUM, Canada, Medical College of Georgia, USA

BACKGROUND: Pulmonary arterial hypertension related to connective tissue disease (PAH-CTD) causes pulmonary microvascular narrowing and loss of perfused distal capillary bed. The lung microcirculation normally metabolizes angiotensin-1 via capillary endothelium-bound angiotensin converting enzyme (PCEB-ACE) and clears circulating endothelin-1 (ET-1) via the endothelial ETB receptor. We have previously described reduced functional pulmonary microvascular surface area in PAH-CTD patients for one or both of these metabolic activities, but it is unknown whether the degree of reduction for both is proportional. The objective of the present study was to see whether the degree of reduction in functional surface area is proportional for ACE metabolism and ET-1 clearance in a population of patients with PAH-CTD.

METHODS: At cardiac catheterization for evaluation of PAH-CTD in 13 patients (6 limited SSc, 3 diffuse SSc, 1 SLE, 2 MCTD, 1RA), first-pass pulmonary vascular metabolic and clearance studies were performed using radiolabelled substrates for ACE metabolism and ET-1 clearance injected into right atrial blood. Functional surface area was calculated as Amax/Km/BSA for ACE metabolism, and Permeability Surface product/BSA for ET-1 clearance. Linear regression was performed for analysis of a relationship. BSA is body surface area, and both activities were normalized for BSA.

RESULTS: There was a significant (Spearman Rho= 0.65, p=0.015) linear relationship between Amax/Km/BSA and PS/BSA. The equation for the regression line was:
Amax/Km/BSA = 0.52 * PS/BSA + 866.

CONCLUSION: In a population of patients with PAH-CTD, the degree of reduction of functional vascular surface area is proportional for these two clinically important pulmonary microvascular metabolic activities. The correlation is not perfect, indicating that there is variation in this proportionality in individual patients. Moreover, the slope of the line being 0.52 suggests that PAH-CTD may affect one metabolic function more than the other.