Pulmonary arteriovenous malformations and other pulmonary aspects of HHT

Abstract

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.

2 Pulmonary arteriovenous malformations

“…A Danish epidemiological study demonstrated cerebral abscess rates of 0.4/100,000/yr in the general population but 155/100,000/yr in patients with HHT/PAVMs (38). Crosssectional rates of 7.8 to 19.0% are reported in different series (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)22), including 9.05% in 219 consecutive patients with PAVM/HHT, adjusting for ascertainment bias (22).…”

“…Current international guidelines recommend postembolization CT scans at 6 to 12 months, then every 3 years thereafter, with CT scans every 1 to 5 years for other patients with CTevident PAVMs or positive contrast echocardiographic studies (5). These recommendations were not adopted universally due to radiation concerns (6,7,20,22,88,89), and in the light of data from Reference 13, are likely to be revised in the future. Alternate follow-up strategies used include magnetic resonance imaging, noting resolution is currently limiting (88,89) …”

“…Amplatzer vascular plugs have rapidly become the preferred agent for embolization compared with coils (36,48,82,83). Advantages include the ability to occlude large-diameter feeding arteries with single plugs (thus reducing procedure time and radiation exposure), easier occlusion at the neck of the sac, and occlusion over a shorter length of vessel, thereby reducing the likelihood of occluding vessels supplying normal lung (6,7,48).…”

“…Paradoxical embolism of devices, thrombi, or air bubbles (leading to angina, strokes, or the need for retrieval) are rare and seem to have been reduced by technical advances reported in later series. Potential massive hemoptysis from systemic arterial collaterals that develop in the months after embolization remains a concern, requiring dual systemic (bronchial) and pulmonary angiographic approaches for embolization (7,9,36).…”

“…Previous review articles summarize the pathophysiology and management recommendations using evidence available in 1998 (2, 3), 2006 (4,5), and 2011 to 2013 (6)(7)(8)(9)(10)(11). As first proposed 60 years ago (12), treatment of asymptomatic patients with PAVMs is recommended to prevent later complications, with embolization now the standard of care ( Figure 3).…”