EVALUATION OF THE PULMONARY VASCULATURE AND DYNAMICS WITH INTRAVASCULAR ULTRASOUND IMAGING IN CHILDREN AND INFANTS

The ability to assess the pulmonary vasculature in pulmonary vascular disease by hemodynamic or histologic evaluation is limited. We sought to determine the feasibility of intravascular ultrasound techniques in infants and children and to assess simultaneously the morphology and dynamics of pulmonary arteries. Patients were seen in the Department of Pediatrics, Division of Pediatric Cardiology, Sophia Children's Hospital, Rotterdam, The Netherlands. We performed intravascular ultrasound imaging in 11 pediatric patients with congenital heart disease undergoing cardiac catheterization. Luminal diameter, area, and pulsatility were determined at two to five sites in the pulmonary branches. Pulmonary vascular reaction to 100% oxygen inhalation was studied. Patients weighed 4.1-51.0 kg (21.8 +/- 16.3 kg, mean +/- SD). Luminal diameters, areas, and pulsatilities could be determined reproducibly in arteries with diameters from 1.6 to 9.3 mm. In total 39 sites were studied in 11 patients. Pulsatility was related to vessel size (r = 0.81), although a substantial interindividual variation was present. After 100% oxygen inhalation, pulsatility increased in all arteries (from 20.0 +/- 3.3% to 25.9 +/- 2.9%, p < 0.05), and vasodilatation could be directly visualized, most prominently in the smallest arteries (percentage change in diameter, mean 7.4 +/- 2.8% versus -2.8 +/- 3.1% in the largest arteries, p < 0.001). Measurement of wall thickness was not feasible, but specific changes in the appearance of the wail structure could be recognized in a patient with severely elevated pulmonary vascular resistance. The specific advantages of intravascular ultrasound in assessing pulmonary vascular disease are discussed. We conclude that intravascular ultrasound imaging of the pulmonary vasculature is feasible in infants and children and provides a unique opportunity to assess directly pulmonary dynamics in vivo. Therefore, it may be a valuable tool in evaluating the pulmonary vasculature and its responses to normal and pathologic conditions.