Wall morphology of the pulmonary artery--intravascular ultrasound imaging and pathological evaluations

The pathological assessment of the pulmonary vascular bed is essential for the diagnosis and management of congenital heart disease with pulmonary hypertension. To investigate the relationship between intravascular ultrasound (IVUS) findings and the Heath-Edwards (H.E.) grade of human pulmonary arteries, 40 pulmonary arterial segments from 17 autopsies and 5 patients with pulmonary hypertension were evaluated using a high-frequency IVUS imaging system. Histological observations were carried out at the same sites that were examined with IVUS and at the distal pulmonary arterioles of the same branches. The subjects were subdivided into 3 groups-group I: 7 patients with pulmonary hypertension (20 segments); group II: 10 patients without pulmonary hypertension (20 segments); and group III: 5 patients with pulmonary hypertension who were studied in vivo. All 20 segments from group I had a three-layered appearance, and 3 patients with H.E. grade < 3 had an increased thickness of the echolucent zone due to media hypertrophy without an intimal reaction. In contrast, IVUS findings from patients with severe pulmonary hypertension (H.E. grade > or = 3) showed an increased thickness with a bright inner layer due to intima hyperplasia. Evidence for a plaque-like lesion was defined in one patient with severe pulmonary hypertension. The percentage of wall thickness derived from IVUS was significantly correlated with that determined by histological examination in group I. The pulmonary artery walls in group II had a one-layer appearance. Similar IVUS findings were obtained from the in vivo study regardless of whether pulmonary hypertension was present. These findings indicate that the IVUS may be an unique technique for evaluating the morphology of the pulmonary artery or arteriole in pulmonary hypertension and may provide objective and quantitative evaluation without a lung biopsy.