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.1 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.2 These observations led several groups of investigators3-7 (following early animal studies by Austen et al 8 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 effects 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.9 Several uncontrolled studies subsequently demonstrated clinical and haemodynamic improvement and suggested increased survival in selected patients with severe pulmonary vascular disease.3-6 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 …