Objective: Increased pulmonary blood flow is believed to contribute to the development of pulmonary hypertension. We investigated the effect of overcirculation via an aortocaval fistula, on the development of monocrotaline-induced pulmonary hypertension in rats. Monocrotaline was administered 1 wk after the creation of an aortocaval fistula.
Design: Randomized, controlled study.
Setting: Research laboratory of an academic institution.
Subjects: Male Sprague-Dawley rats.
Interventions: Overcirculation was induced by pneumonectomy and by surgical creation of aortocaval fistula. Pulmonary artery hypertension was induced by administration of monocrotaline.
Measurements and main results: Aortic blood flow, Pao(2), and pulmonary arterial pressure were measured 4 wks later. A blinded investigator quantified pulmonary arterial neointimal formation in small pulmonary arteries. Compared with animals that received monocrotaline and/or underwent pneumonectomy but did not undergo aortocaval fistula, the presence of a surgical aortocaval fistula was associated with increased aortic blood flow (p <.001), increased Pao(2) (p <.001), and lower mean pulmonary arterial pressure (p <.001). In addition, rats with aortocaval fistula had less pulmonary arterial neointimal formation than matched animals without an aortocaval fistula (p =.034).
Conclusions: The presence of a surgical aortocaval fistula attenuates, rather than worsens, the development of monocrotaline-induced pulmonary hypertension in rats.