Management of severe pulmonary hypertension in patients undergoing mitral valve surgery.

Pulmonary hypertension (PH) is simply defined as a mean pulmonary artery pressure greater than 25 mmHg at rest; however, may result from varying combinations of abnormal pulmonary artery (PA) blood flow, pulmonary vascular resistance (PVR), PA compliance, and pulmonary venous pressure. Mitral regurgitation (MR) allows for partial transmission of systemic arterial pressure into the pulmonary venous system. Mitral stenosis (MS) prevents pulmonary venous drainage into the left ventricle. In either case, the direct result is marked pressurization of the pulmonary venous system, with the primary cause of PH in significant mitral valve disease (PHMVD) being pulmonary venous hypertension (PVH). Chronic and severe PVH may then lead to muscularization of the pulmonary arterial bed, with a rise in PVR and loss of pulmonary arterial compliance that follows ("reactive" pulmonary vascular disease). Right heart dysfunction ensues once the PVR rises and the compliance falls to a point in which the right ventricle (RV) cannot overcome the increased afterload. However, it is worth emphasizing that in the setting of PHMVD, no matter the degree of mismatch between RV afterload and RV function, the root condition in the patient and cause of the PH remains severe MV disease. Without correction of the primary condition, the patient's heart failure (HF), PH, PVR, and RV dysfunction will remain or progress. Moreover, direct PH medical therapies are ineffective and may actually worsen left heart congestion in the setting of unremediated MVD. Therefore, although surgery may be a higher risk in some patients with PHMVD, the potential benefits justify the risks in the majority of cases. If needed, direct medical management of PH is far simpler and more effective once the MVD is corrected, given the degree of left heart congestion often improves dramatically. Therefore, corrective mitral valve intervention should be considered as the main and definitive treatment for these patients.