Chest
Recent Advances in Chest MedicinePulmonary Arteriovenous Malformations
Section snippets
Epidemiology
Population-based studies determining the incidence of PAVM in the general population do not exist, to our knowledge. PAVMs are rare, with initial autopsy reports describing only three in 15,000 autopsies performed.19 Despite limitations in epidemiologic studies, the approximate incidence of PAVM has been described to be two to three per 100,000,14, 20 with a male-to-female ratio of approximately 1:1.5 to 1.8.21, 22, 23 Most PAVMs are hereditary, with 80% to 95% occurring in patients with HHT.4,
Pathophysiology
PAVMs may be single or multiple, unilateral or bilateral, and simple or complex. Most solitary PAVMs are seen in the lower lobes, with the left lower lobe being the most common location followed by right lower lobe.4, 5, 11, 26 The majority of multiple PAVMs are also confined to the lower lobes, with the incidence of bilateral PAVMs ranging from 8% to 20%.2, 27 Simple PAVMs receive blood through a single artery, and complex PAVMs receive blood through two or more arteries (Figs 1B, 1C). The
Etiology
Most PAVMs are hereditary, with about 90% occurring in patients with HHT and in whom there is a 30% to 50% incidence.3, 34, 35, 36 The majority of the non-HHT-related PAVMs are idiopathic, but other causes have been described and include infections, such as schistosomiasis37 and actinomycosis27; trauma27; and Fanconi syndrome.38 PAVMs can also occur secondary to hepatopulmonary syndrome (HPS)39 or bidirectional cavopulmonary shunts (BCPSs).40
Clinical Manifestations and Complications
Clinical features seen in PAVM are not uniform in the different published series because of a significant overlap of disease entities. Signs and symptoms of patients with PAVM vary depending on the size, number, and flow through the PAVM. Patients may be completely asymptomatic or experience dyspnea on exertion. In general, a single PAVM of < 2 cm in size does not usually result in symptoms.4 Hypoxemia at rest or with exercise may be present, especially in the presence of a significant
Diagnostic Testing
A proposed algorithm for the screening and diagnosis of PAVM is presented in Figure 3. The diagnosis of PAVM often is made as a result of a chest roentgenogram or a chest CT (CCT) scan requested for investigation of respiratory symptoms such as dyspnea or hemoptysis or as part of a screening process in patients where right-to-left shunting is suspected, including, but not limited to, HHT, cerebral abscess, and unexplained embolic stroke. The presence of PAVM on chest roentgenogram classically
Treatment and Management
Data from observational studies regarding untreated PAVM mostly in HHT show considerable morbidity, including stroke, cerebral abscess, hypoxemia, migraine, and hemorrhage.82, 83 Surgical resection, with its inherent morbidity, was the only available therapy for PAVM before the advent of percutaneous transcatheter embolization (TCE).
Conclusions
PAVMs are abnormal vascular structures that most often connect a pulmonary artery to a pulmonary vein, bypassing the normal pulmonary capillary bed and resulting in an intrapulmonary right-to-left shunt. The main complications of PAVM result from intrapulmonary shunt and include stroke, brain abscess, and hypoxemia. These malformations may be idiopathic or genetic (eg, HHT) or relate to secondary conditions such as HPS and BCPS. The most common cause of PAVM is HHT. The preferred screening test
Acknowledgments
Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
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