Pulmonary arteriovenous malformations (PAVMs) are thin-walled abnormal vessels which provide direct capillary-free communications between the pulmonary and systemic circulations. Patients with PAVMs have usually have low blood oxygen levels and are at risk of other complications including strokes, brain abscesses, pregnancy-related complications and haemorrhage. We hypothesise that the complications of PAVM patients arise from their PAVMs and not the more recognised intracardiac forms of shunting. We propose to perform echocardiograms to enable assessment of the presence of other causes of capillary-free communications between the pulmonary and systemic circulations.