Abstract 4372620: Pulmonary Vascular Endothelial Dysfunction is Induced by Non-Pulsatile Pulmonary Blood Flow in an Ovine Classic Glenn Model

Background: Pulmonary vascular disease in patients with single ventricular heart disease (SVHD) following the partial cavalpulmonary connection (Glenn) is a significant source of morbidity and shortened lifespan. Pulmonary vascular endothelial cell (EC) dysfunction, an established precursor to pulmonary vascular disease, is well characterized following the Fontan, but data are limited following the Glenn procedure. The role of potential drivers of this pathology, which include hypoxemia, polycythemia, and aberrant pulmonary blood flow patterns, are unclear. Hypothesis: Non-pulsatile blood flow is the primary driver of pulmonary EC dysfunction following the Glenn procedure. To study this hypothesis, we utilized an ovine classic Glenn model which induces passive, non-pulsatile blood flow to the right lung, independent of hypoxemia and polycythemia. Methods: Seven lambs (6-8 weeks old) underwent a classic Glenn procedure in which the right pulmonary artery (PA) and superior vena cava were anastomosed in an end-to-end fashion. 8 weeks after surgery, 7 Glenn and 7 age-matched controls were studied. The response to acetylcholine (Ach, an endothelium-dependent vasodilator) was determined in 5 th generation isolated PAs. Right lung tissues were obtained to measure nitric oxide (NO) metabolites (NOx, chemiluminescence), endothelin-1 (ET-1, ELISA) levels, endothelial nitric oxide synthase (eNOS) protein and Pre-pro ET-1 protein (Western blot). Pulmonary artery endothelial cells (PAECs) were cultured to determine cell proliferation, angiogenesis (Matrigel Assay), and apoptosis (ELISA). Comparisons were made by unpaired t-test and ANOVA. A p<0.05 was considered significant. Results: Baseline demographics were similar between the groups. Mean PA pressure (12.1±2.4vs. 16.7±3.1 mmHg) and left PA flow (0.039±0.01 vs. 0.064±0.01 L/kg/min) were higher in Glenn lambs (p<0.05). Glenn PAs had impaired relaxation to Ach (Fig. 1). Glenn PAECs had higher rates of proliferation (201%) and angiogenesis (164%), and decreased apoptosis (-14%) (p < 0.05). Glenn lung tissue eNOS protein expression was 1.7-fold lower; Prepro-ET-1 protein was 6.6-fold higher (p<0.05). Glenn lung tissue NOx was lower (Fig. 2) and ET-1 was higher than controls (Fig. 3). Conclusions: The initiation of non-pulsatile pulmonary blood flow following the Glenn procedure induces early EC dysfunction. Further investigation of these mechanisms could lead to important therapeutic targets for patients with SVHD.