Atrial septostomy represents an additional, promising strategy in the treatment of severe PPH. Experience with this procedure still is limited; however, based on analyses of the worldwide experience, several general conclusions and recommendations can be made. 1. Atrial septostomy can be performed successfully in selected patients with advanced pulmonary vascular disease. 2. Patients with primary pulmonary hypertension who have undergone successful AS have shown: a significant clinical improvement beneficial and long-lasting hemodynamic effects at rest a trend toward improved survival 3. The procedure-related mortality of the collective experience is high (16%). Several recommendations can be made to minimize the risk: [figure: see text] Atrial septostomy should be attempted only in institutions with an established track record in the treatment of advanced pulmonary hypertension, where septostomy is performed with low morbidity. Atrial septostomy should not be performed in patients in whom death is impending or who have severe right ventricular failure and are on maximal cardiorespiratory support. An mRAP greater than 20 mm Hg, PVR index greater than 55 u/m2, and a predicted 1-year survival less than 40% are significant predictors of procedure-related death. Before cardiac catheterization, patients should have an acceptable baseline systemic oxygen saturation (> 90% in room air) and optimized cardiac function (adequate right heart filling pressure, additional inotropic support if necessary). During cardiac catheterization, the following are mandatory: Supplemental oxygen Mild sedation to prevent anxiety Careful monitoring of variables (left atrial pressure, SaO2, and mRAP) Step by step procedure After AS, it is important to optimize oxygen delivery. Transfusion of packed red blood cells or erythropoietin (before and following the procedure, if needed) may be necessary to increase oxygen content. 4. Because the disease process in PPH is unaffected by the procedure (late deaths), the long-term effects of an AS must be considered to be palliative. 5. Despite its risk, AS may represent a viable alternative for selected patients with severe PPH. Indications for the procedure may include: Recurrent syncope or right ventricular failure, despite maximal medical therapy, including oral calcium-channel blockers or continuous intravenous prostacyclin (Fig. 11) As a bridge to transplantation When no other option exists.