Pulmonary arteriovenous malformations and other pulmonary aspects of hereditary haemorrhagic telangiectasia

Pulmonary arteriovenous malformations (PAVMs) are vascular structures that provide a direct capillary-free communication between the pulmonary and systemic circulations. The majority of patients have no PAVM-related symptoms, but are at risk of major complications that can be prevented by appropriate interventions. More than 90% of PAVMs occur as part of hereditary haemorrhagic telangiectasia (HHT), the genetic condition most commonly recognised by nosebleeds, anaemia due to chronic haemorrhage, and/or the presence of arteriovenous malformations in pulmonary, hepatic or cerebral circulations. Patients with HHT are also at higher risk of pulmonary hypertension and pulmonary embolic disease, management of which can be compounded by other aspects of their HHT. This chapter primarily addresses PAVMs and pulmonary HHT in the clinical setting, in order to improve patient care. Clinical presentation patterns, diagnostic strategies and management options are presented in detail. Relevant pathophysiological mechanisms discussed include new topics for the PAVM literature, such as the alveolar transit of venous bubbles during diving and contrast echocardiography.