Pulmonary hypertension following mitral valve repair in a dog

Abstract

Postoperative pulmonary hypertension upon weaning off from cardiopulmonary bypass occurs due to lung ischemia-reperfusion injury. Ischemic injury from deprivation of blood flow to the lungs, stimulation of neutrophils by the cardiopulmonary bypass, and complement activation leading to systemic inflammatory response contribute to the pathogenesis of lung ischemia-reperfusion injury. We report a canine patient that developed a severe pulmonary hypertension following mitral valve repair. On postoperative day 3, respiratory rate had increased and chest x-ray revealed increased opacity. Echocardiographic findings were severe tricuspid regurgitation and severe pulmonary hypertension. Clinical signs improved following the administration of sildenafil, diuretics and pimobendan, and the patient was discharged. However, upon discontinuation of sildenafil, respiratory distress has returned so the patient was placed back on sildenafil. Sildenafil has been used to decrease pulmonary hypertension after open heart surgery in humans. This patient developed severe pulmonary hypertension despite the marked reduction in mitral valve regurgitation postoperatively, the following factors were considered: endothelial cell dysfunction, hypoxic pulmonary vasoconstriction, pulmonary vasoconstriction mediated by sympathetic stimulation following general anesthesia. This patient responded well to oral sildenafil and we can suggest that sildenafil is an effective agent for treatment of pulmonary hypertension following cardiac surgery in dogs.