Role of atrial septostomy in the treatment of pulmonary vascular disease.

Primary pulmonary hypertension is characterised by a progressive increase in pulmonary artery pressure which eventually leads to right ventricular failure and death. Patients with severe right heart failure—for example, New York Heart Association functional class IV—have the worst prognosis. Although several haemodynamic parameters such as pulmonary artery pressure, right atrial pressure, and cardiac index have been shown to correlate with mortality, right atrial pressure reflecting right heart function correlates best with survival. Furthermore, patients with primary pulmonary hypertension in whom the foramen ovale is patent have been reported to live longer than those without a patent foramen ovale. These observations led several groups of investigators (following early animal studies by Austen et al which showed that an interatrial communication allowed decompression of a hypertensive right ventricle and augmentation of systemic blood flow, particularly during exercise) to evaluate the eVects of atrial septostomy on clinical signs and symptoms, haemodynamics, and survival in patients with severe primary pulmonary hypertension as well as pulmonary vascular obstructive disease associated with other conditions. Blade balloon atrial septostomy was first reported by Rich and Lam in 1983 as palliative treatment for refractory primary pulmonary hypertension. Several uncontrolled studies subsequently demonstrated clinical and haemodynamic improvement and suggested increased survival in selected patients with severe pulmonary vascular disease. The limitations of these studies were: (1) the series were all uncontrolled, (2) the indications for performing the procedures varied between the studies, (3) the aetiology of the pulmonary vascular disease was not the same in all patients, and (4) the medical treatment for pulmonary vascular disease has changed over the past 15 years. Despite the significant limitations in these published series, atrial septostomy appears to be a therapeutic modality for advanced pulmonary vascular disease when no other therapeutic options exist and a patient has persistent indications for performing an atrial septostomy. The acute haemodynamic eVect of creating an atrial septostomy is to increase systemic oxygen transport by increasing cardiac output. In addition, the decrease in right atrial pressure reduces systemic venous congestion thereby improving right heart failure. With exercise, right to left shunting will increase further with increased oxygen transport although at the expense of the systemic arterial oxygen saturation. Because the pulmonary vascular bed is unaVected by the procedure, the long term eVects of an atrial septostomy must be considered palliative. The reasons why patients improve clinically and haemodynamically following atrial septostomy remain incompletely understood. In addition to resolution of syncopal episodes and a decrease in right heart failure, patients report resolution of ischaemic chest pain following atrial septostomy, suggesting improved right ventricular coronary perfusion due to a decrease in right heart filling pressures. A therapeutic algorithm with suggested indications for performing an atrial septostomy is shown in fig 1. Whether or not a patient has recurrent syncope and/or right heart failure with an intact atrial septum or a restrictive patent foramen ovale, initial evaluation with acute vasodilator drug testing in order to initiate medical therapy with a chronic vasodilator agent is recommended rather than performing an atrial septostomy. If a patient is an acute “responder”, defined by a significant decrease in pulmonary artery pressure with no change or an increase in cardiac index, 11 chronic oral vasodilator therapy with, for example, calcium channel blockade usually results in clinical and haemodynamic improvement as well as resolution of recurrent syncope and/or right heart failure. For patients