RELATIONSHIP BETWEEN HEMODYNAMICS AND MORPHOLOGY IN PULMONARY-HYPERTENSION - A QUANTITATIVE INTRAVASCULAR ULTRASOUND STUDY

Background Intravascular ultrasound imaging of the pulmonary arteries has been demonstrated to be a reliable method of quantifying vessel di ameter, luminal area and pulsatility. Simultaneous measurement of flow velocity and its response to vasodilators allows the relationship bet ween morphology and functional compromise to be studied, especially en dothelial dysfunction. Methods In 51 patients (mean age=49.8+/-12.6 ye ars, 17 female) we performed right heart catheterization and simultane ous intravascular ultrasound of pulmonary artery branches. The patient s were divided in two groups: group 1 with normal pulmonary artery pre ssure and pulmonary vascular resistance, and group 2 with pulmonary hy pertension (peak pulmonary artery pressure >30 mmHg and/or mean pulmon ary artery pressure >20 mmHg). Vessel wall and lumen were studied usin g a 2.9 F intravascular ultrasound catheter with a 30 MHz phased array transducer. Measurement of blood flow velocity was accomplished by a Doppler flow wire (0.018 inch). The maximal flow change during acetylc holine infusion (adjusted to 10(-6); 10(-5), and 10(-4)M concentration in the blood vessel) was measured. Results There were no significant differences between groups 1 and 2 with respect to age (48.5+/-14.3 ye ars vs 50.3+/-12.3 years; P=ns), gender (4 female/8 male vs 13 female/ 26 male; P=ns), luminal area of the vessel segment in which the intrav ascular ultrasound measurements were obtained (11.8+/-6.1 mm(2) vs 16. 7+/-14.3 mm(2); P=ns), internal diameter (3.9+/-1.2 mm vs 4.2+/-1.7 mm ; P=ns), and external diameter (6.1+/-1.3 mm vs 6.9+/-2.1 mm; P=ns). C ross-sectional images of the pulmonary artery wall demonstrated a sing le ring with high echodensity with a thin inner layer regarded as inti ma in group 1. In contrast, the majority of patients (n=35/39) in grou p 2 demonstrated a thickening of the intimal layer and/or a disturbanc e of layering of the echogenic arterial wall. The relative wall thickn ess was higher in group 2 than in group 1 (22.5+/-10.4% vs 15.3+/-6.5% ; P<0.05). There were no significant correlations between pulmonary ar tery pressure and wall thickness pulmonary artery pressure and area ch ange in the cardiac cycle, acetylcholine-dependent increase in pulmona ry flow and morphological changes in the vessel wall. Conclusion We co nclude that intravascular ultrasound is capable of detecting morpholog ical changes in the pulmonary vessel wall in pulmonary hypertension an d that vessel wall hypertrophy of small pulmonary segment arteries, as detected by intravascular ultrasound, is not predictive of functional vasodilatory response of resistance vessels of the same vessel area.