Percutaneous creation of an atrial shunt to alleviate acute circulatory compromise in pulmonary hypertensive crisis was applied more than 50 years ago in the Rashkind procedure. In left-sided heart failure (HF), shunting blood from a pressure-overloaded left atrium to a compliant, lower-pressure right atrium gained interest as a therapeutic principle about a decade ago. Historically, it was known that patients with severe mitral stenosis and a concomitant atrial septal defect were less symptomatic than patients with severe mitral stenosis and an intact atrial septum. Furthermore, it was known that percutaneous closure of an atrial septal defect, especially in older adults, could sometimes unmask severe left ventricular diastolic dysfunction leading to acute pulmonary oedema because the shunting possibility was lost owing to closure of the defect.