Systemic lobar shunting induces advanced pulmonary vasculopathy

Abstract

Objectives: We characterized the morphology and vasomotor responses of a localized, high-flow model of pulmonary hypertension. Methods: An end-to-side anastomosis was created between the left lower lobe pulmonary artery and the aorta in 23 piglets. Control animals had a thoracotomy alone or did not have an operation. Eight weeks later, hemodynamic measurements were made. Then shunted and/or nonshunted lobes were removed for determination of vascular resistance and compliance by occlusion techniques under conditions of normoxia, hypoxia (FIO2 = 0.03), and inspired nitric oxide administration. Quantitative histologic studies of vessel morphology were performed. Results: Eighty-three percent of animals having a shunt survived to final study. Aortic pressure, main pulmonary artery and wedge pressures, cardiac output, blood gases, and weight gain were not different between control pigs and those receiving a shunt. Six of 9 shunted lobes demonstrated systemic levels of pulmonary hypertension in vivo. Arterial resistance was higher (24.3 ± 12.0 vs 1.3 ± 0.2 mm Hg · mL-1 · s-1, P = .04) and arterial compliance was lower (0.05 ± 0.01 vs 0.16 ± 0.03 mL/mm Hg, P = .02) in shunted compared with nonshunted lobes. Hypoxic vasoconstriction was blunted in shunted lobes compared with nonshunted lobes (31% ± 13% vs 452% ± 107% change in arterial resistance, during hypoxia, P