INTRAVASCULAR ULTRASONIC CHARACTERISTICS AND VASOREACTIVITY OF THE PULMONARY VASCULATURE IN CHILDREN WITH PULMONARY-HYPERTENSION

We sought to describe the morphologic characteristics of pulmonary art eries by intravascular ultrasound (IVUS) in children with and without pulmonary hypertension to compare these anatomic findings with those o f pulmonary wedge angiography, and to determine the relation between t hese structural findings and functional reactivity to pulmonary vasodi lators. Direct evaluation of pulmonary vascular structure in children with pulmonary hypertension with current imaging techniques has been l imited and little is known about the relation between structural and f unctional characteristics of the pulmonary vasculature. In 23 children undergoing cardiac catheterization (15 with pulmonary hypertension an d 8 controls) we performed IVUS and pulmonary wedge angiography of the distal pulmonary arteries in the same lobe. IVUS was performed in 44 pulmonary arteries measuring 2.5 to 5.0 mm internal diameter with a 3. 5Fr 30-MHz IVUS catheter. We assessed vasoreactivity to inhaled nitric oxide (NO) and oxygen in 13 of 15 children with pulmonary hypertensio n, Baseline pulmonary vascular resistance (PVR) was greater in the 15 children with pulmonary hypertension than in the 8 controls (9.5 +/- 1 .9 vs 1.5 +/- 0.3 U x m(2), p <0.05). NO lowered PVR in patients with pulmonary hypertension (p <0.05). IVUS studies in patients with pulmon ary hypertension showed a thicker middle layer, wall thickness ratio, and diminished pulsatility than did those in controls (p <0.05). The i nner layer was not visualized by IVUS in any control patient, but was seen in 9 of 15 patients with pulmonary hypertension. Pulmonary artery wedge angiography correlated with baseline mean pulmonary artery pres sure and PVR as well as with IVUS findings of wall thickness ratio and inner layer thickness. The inner layer was not visualized by IVUS in any patient with grade 1 wedge angiograms or in 86% of patients with g rade 2 wedge angiograms. All patients with grade 4 and 80% of patients with grade 3 wedge angiograms had a visible inner layer. Vasoreactivi ty to NO and oxygen did not correlate with structural assessment of th e pulmonary vasculature by IVUS, Structural changes in the pulmonary a rteries in children with pulmonary hypertension can be directly visual ized by IVUS, but are not predictive of NO-induced pulmonary vasodilat ion. IVUS examination of pulmonary arteries may complement current tec hniques utilized in the evaluation of children with pulmonary hyperten sion. (C) 1998 by Excerpta Medico, Inc.