No abstract

Pulmonary artery (PA) stenosis is a difficult obstructive defect to manage since clinicians cannot know a priori which obstructions to treat and when. Prognosis of PA stenosis and its chronic effects on lung development are poorly understood. This study aimed to characterize the hemodynamic and structural effects of PA stenosis during development. Fourteen male Sprague-Dawley rats underwent left PA (LPA) banding at age 21 days, and 13 underwent sham operation. Hemodynamic and structural impacts were studied longitudinally at 20, 36, 52, 100, and 160 days. Chronic LPA banding resulted in a significant reduction in LPA flow (P < 0.0001) and size of both proximal LPA (P < 0.0001) and distal LPA (P < 0.01), as well as a significant increase in flow and size of the right PA (P < 0.05) throughout development. Flows and sizes adapted such that normal levels of wall shear were restored after banding. At 160 days, LPA banding resulted in a significant decrease in left lung volume and an increase in right lung volume but no significant differences in total lung volume. There was an elevation of proximal LPA pressure as well as right ventricular hypertrophy in the banded animals. The banded lung exhibited arterial disorganization, loss of vessels, and enlargement of its bronchial arteries, whereas the contralateral lung showed signs of vascular pathology. There are consequences on development of both lungs in the presence of an LPA stenosis at young age. These results suggest that early intervention may be necessary to optimize left lung growth and minimize right lung vascular pathology.

Malformations of the pulmonary arteries can increase right heart workload and result in morbidity, heart failure, and death. With the increased use of murine models to study these malformations, there is a pressing need for an accurate and noninvasive experimental technique that is capable of characterizing pulmonary arterial hemodynamics in these animals. We describe the growth trends of pulmonary arteries in 13 male Sprague-Dawley rats at 20, 36, 52, 100, and 160 days of age with the introduction of phase-contrast MRI as such a technique. PCMRI results correlated closely with cardiac output measurements by ultrasound echocardiography and with fluorescent microspheres in right-left lung flow split (flow partition). Mean flow, average cross-sectional area, distensibility, and shear rates for the right and left pulmonary arteries (RPA and LPA) were calculated. The RPA was larger and received more flow at all times than the LPA (P < 0.0001). Right-left flow split did not change significantly with age, and arterial distensibility was not significantly different between RPA and LPA, except at 160 days (P < 0.01). Shear rates were much higher for the LPA than the RPA (P < 0.0001) throughout development. The RPA and LPA showed different structure-function relationships but obeyed similar allometric scaling laws, with scaling exponents comparable to those of the main pulmonary artery. This study is the first to quantitatively describe changes in RPA and LPA flows and sizes with development and to apply phase-contrast MRI techniques to pulmonary arteries in rats.

No abstract

Congenital heart defects are structural problems with the heart and/or major blood vessels which in the U.S. alone affect as many as 1.3 million people [1]. A common form of abnormality is a stenosis or narrowing of the pulmonary arteries. Chronic pulmonary artery stenosis may lead to differential lung growth and reduced cardiac performance. Treatment, however, may result in no significant improvements in flow distribution or pressure because of the properties of the vascular bed downstream of the stenosis.