© Borgis - Postępy Nauk Medycznych 4/2017, s. 183-188
*Maryla Kuczyńska, Anna Drelich-Zbroja, Michał Sojka, Krzysztof Pyra, Łukasz Światłowski, Tomasz Jargiełło
Revision of facts on pulmonary arteriovenous malformations – experience with embolization techniques
Przegląd aktualnej wiedzy dotyczącej malformacji płucnych – doświadczenia własne w embolizacji przetok tętniczo-żylnych
Department of Interventional Radiology and Neuroradiology, Medical University in Lublin
Head of Department: Professor Małgorzata Szczerbo-Trojanowska, MD, PhD
Streszczenie
Wstęp. Przetoki tętniczo-żylne krążenia płucnego stanowią bezpośrednie połączenia pomiędzy naczyniami tętniczymi i żylnymi, z pominięciem naczyń mikrokrążenia. Powstający w konsekwencji przeciek prawo-lewy może prowadzić do hipoksemii systemowej oraz utraty właściwości filtracyjnych płucnego łożyska naczyniowego, co z kolei stwarza zagrożenie pojawienia się zagrażających życiu komplikacji neurologicznych, wywołanych obecnością zatorów paradoksalnych. Spośród płucnych malformacji tętniczo-żylnych około 60-90% pojawia się w przebiegu dziedzicznej teleangiektazji krwotocznej. Celem leczenia przetok jest zapobieganie potencjalnie śmiertelnym powikłaniom natury krwotocznej lub neurologicznej, a metody embolizacji naczyniowej stanowią metodę z wyboru.
Cel pracy. Celem niniejszego opracowania było przedstawienie aspektów technicznych i skuteczności wybranych, aktualnych metod leczenia przetok tętniczo-żylnych krążenia płucnego w odniesieniu do ich angioarchitektury, w oparciu o przegląd dostępnej litearatury i doświadczenia własne.
Materiał i metody. Przeprowadzono retrospektywną ocenę 5 przypadków klinicznych pacjentów z radiologicznie potwierdzonym rozpoznaniem malformacji tętniczo-żylnej w łożysku płucnym. W każdym z powyższych przypadków zastosowano leczenie w formie embolizacji naczynia doprowadzającego z wykorzystaniem zatyczek AMPLATZER i/lub spiral oraz mikrospiral. Ocenę sukcesu technicznego przeprowadzonych interwencji oraz ewentualną obecność powikłań zabiegowych i okołozabiegowych oceniono w odniesieniu do zastosowanej techniki zabiegu oraz struktury naczyniowej malformacji. Angiografia przed- i pozabiegowa zostały wykonane u wszystkich pacjentów, aby odpowiednio: uwidocznić patologiczne zmiany oraz ocenić stopień powodzenia procedury.
Wyniki. We wszystkich przypadkach osiągnięto pełny sukces techniczny. Nie zaobserwowano wystąpienia powikłań podczas przeprowadzanych zabiegów ani powikłań okołozabiegowych.
Wnioski. Embolizacja tętnicy doprowadzającej jest wysoce efektywną metodą zaopatrywania płucnych przetok tętniczo-żylnych, a okludery AMPLATZER stanowią wygodne rozwiązanie, gwarantujące niemal natychmiastowe zamknięcia naczynia zaopatrującego malformację. Jednakże, ze względu na ograniczony wybór specyfikacji (zwłaszcza średnicy) ww. urządzeń, embolizacja z użyciem spiral jest podstawową metodą zaopatrywania tętnic doprowadzających o średnicy poniżej 3 mm.
Summary
Introduction. Pulmonary arteriovenous malformations are pathological direct connections between arterial and venous circulation, bypassing capillary networks. The consequences of the occurring right-to-left shunt comprise systemic hypoxemia and loss of pulmonary vascular filtration properties, which pose a risk of serious life-threatening neurologic complications because of paradoxical embolism. 60-90% of PAVMs appear to be a manifestation of the underlying Hemorrhagic Hereditary Telangiectasia. Treatment is introduced as protective measures against life-threatening hemorrhagic or neurologic symptoms, and presently transcatheter embolization proved to be a method of choice.
Aim. The aim of this study was to discuss the efficacy and technical details of the selected current approaches to PAVM treatment with respect to the angioarchitecture of the fistulae, based on the literature review and clinical experience.
Material and methods. We performed a retrospective investigation of 5 patients with radiologically confirmed presence of pulmonary arteriovenous malformations. In each case, transcatheter embolization of the feeding artery with use of AMPLATZER vascular plug and/or coils and micro coils was executed. Technical success and presence of procedural and periprocedural complications were assessed with respect to technique of embolization and angioarchitecture of lesions. Pre- and post-procedural selective pulmonary angiographies were implemented to visualize lesions and assess technical success, respectively.
Results. Technical success was achieved in all cases. No procedural or periprocedural complications were observed.
Conclusions. Embolization of the feeding artery is a highly-effective treatment option in case of pulmonary vascular malformations. AMPLATZER vascular occluder is a convenient device allowing for almost immediate occlusion of the supplying vessel to the PAVM. However, limited selection of device characteristics (i.e. diameter) favors coil embolization in case of feeding artery size less than 3 mm.
INTRODUCTION
Pulmonary arteriovenous malformations (PAVMs) are pathological direct connections between arterial and venous circulation, bypassing capillary networks that occur with estimated prevalence of 1 in 100,000 (1). The consequences of the occurring right-to-left shunt comprise not only impaired blood oxygenation mechanisms leading to systemic hypoxemia (more pronounced if diameter of the feeding artery exceeds 5 mm), but even more importantly, loss of pulmonary vascular filtration properties which pose a risk of serious life-threatening neurologic complications because of paradoxical embolism (2, 3).
Occurrence
A considerable majority of PAVMs (i.e. 60-95%) appear to be a manifestation of the underlying Hemorrhagic Hereditary Telangiectasia (HHT), otherwise known as Osler-Weber-Rendu syndrome (2-5). Conversely 15 to 50% of patients diagnosed with HHT develop PAVMs over lifetime (6). In this autosomal dominant, often underdiagnosed condition, with estimated prevalence of 1 in 5000 individuals, vascular malformations are often multiple and occur not only in the setting of pulmonary circulation, but also within brain, gastrointestinal tract and liver. The diagnosis of HHT is typically based upon clinical appearance as approximately 90% of patient will meet Curaçao Criteria (tab. 1) by the age of 40 (3, 5). However, these require presence of epistaxis and/or teleangiectases – symptoms that rarely occur in children and young adults. Genetic testing is therefore the most suitable diagnostic tool in those groups of patients. Despite some particular genes involvement in development of certain HHT types (tab. 2), there are no common mutations that can be easily distinguished. A unique, private mutation is rather present among members of each of the affected families. The remaining 10% of PAVMs are acquired fistulae, mostly associated with development of hepatopulmonary syndrome in cirrhotic patients. However, their appearance may also be attributed to mitral valve stenosis, trauma, actinomycosis, tuberculosis and schistosomiasis. No differences were observed in terms of radiologic and histologic appearance between idiopathic and hereditary PAVMs (3, 5, 7).
Tab. 1. Curaçao Diagnostic Criteria for Hereditary Hemorrhagic Telangiectasia (HHT)
| Criteria | epistaxis | spontaneous, recurrent nose bleeds |
| teleangiectases | multiple at characteristic sites (lips, oral cavity, nose, fingers) |
| visceral lesions | gastrointestinal telangiectasia, pulmonary arteriovenous malformation (AVM), hepatic/cerebral/spinal AVM |
| family history | first degree relative with HHT according to these criteria |
| Diagnosis | definite | 3 or more criteria are fulfilled |
| possible/suspected | 2 criteria are present |
| unlikely | 1 or none criteria are present |
Tab. 2. Genes involved in Hereditary Hemorrhagic Telangiectasia
| HHT 1 | ENG | endoglin gene |
| HHT 2 | ACVRL1 | activin A receptor like type 1 gene |
| HHT with juvenile polyposis | SMAD4 | SMAD family member 4 gene |
Angioarchitecture and classification
80-85% of PAVMs present with simple angioarchitecture. It means that there is only one feeding artery (FA) to the arteriovenous sac, and a single draining vein. In 15-20% cases multiple feeding and/or draining vessels are present – these PAVMs are referred to as complex malformations. In the above mentioned, the simple sac may be septet or multichanneled, or replaced with plexiform tangle of tortuous, dilated vessels (2, 5, 6, 8).
PAVMs may be also classified as single and multiple focal or diffuse (up to 5% of patients). Whereas the former two definitions are quite clear and intuitive, the latter had been subject to discussion. Diffuse PAVMs were first characterized by Faughnan et al. as a condition in which all segmental branches of one or more lobes were diffusely involved by small malformations (3). However, this interpretation was questioned a few years later by Pierucci et al. who described the diffuse pattern of involvement in a more restrictive manner. The new definition simply required reporting on diffuse involvement of particular segments. This was due to the fact, that except for diffusely engaged segmental arteries, many patients simultaneously presented with normal segmental arteries in the same lobe. Such modification allows to distinguish between multiple focal and diffuse lesions, which has its implications in treatment approach and clinical outcomes (9).
Clinical presentation and complications
PAVMs is a pathology with unpredictable natural history. Although the majority of lesions – simple in nature and of small size – remain asymptomatic for a long time, the associated mortality risk reaches 15%. A considerable risk of morbidity associated with neurologic complications persists as well. The peak of clinical manifestations of PAVMs occurs at four to six decade in as many as 70% of patients, who often require treatment at this point (4, 5, 10). Symptoms of systemic hypoxemia, including dyspnea, cyanosis, fatigue, exercise intolerance and eventual heart failure predominate, but do not pose the most danger to health and life of the affected individual (5). The greatest risk is associated with hemorrhagic consequences of PAVM rupture (i.e. hemoptysis, hemothorax) and/or neurologic manifestations of paradoxical emboli (i.e. transient ischemic attack (TIA), ischemic stroke or brain and systemic abscesses) (2, 5). It had been proven as well that pregnancy is a significant risk factor for development of complications (11, 12). As stated above, patients with diffuse patter of PAVM involvement are more prone to occurrence of serious, life-threatening complications, especially when lesions are located bilaterally (9).
Diagnosis and treatment
According to the latest international guidelines on diagnosis and management of HHT, the reference diagnostic tests for pulmonary malformations comprise unenhanced thin-cut computed tomography (CT) and angiography. However, it has been postulated that transthoracic contrast echocardiography (TTCE) with agitated saline may be a useful screening tool in suspected patients. The examination is considered positive in case of detection of air bubbles within left atrium due to existence of intrapulmonary shunt. All positive outcomes must be confirmed with reference CT (3, 7, 11).
The aforementioned high incidence of PAVMs among patients with HHT implies careful screening for the disease in individuals with PAVMs who have not been previously diagnosed with Osler-Weber-Rendu syndrome (3, 7, 11).
Treatment is introduced as protective measures against life-threatening hemorrhagic or neurologic symptoms (5, 13, 14). This implies that even asymptomatic lesions are managed in adult patients, contrary to children and individuals with diffused pattern of the disease – in these two cases treatment is delayed until symptoms occur. Because PAVMs are classified as high-flow malformations, the greater diameter of FA results in greater risk of dislodgement of thrombotic material. Therefore, it is generally accepted that all PAVMs with diameter of FA exceeding 3 mm are treated (2, 3, 9, 14). However, some of the authors argue that smaller diameter of the supplying vessel fails to prevent from migration of bacteria and, as a result – cranial and systemic abscesses (3, 14).
Historically, all PAVMs were treated by surgical means, however, presently transcatheter embolization proved to be highly-effective, organ-sparing first-line treatment and surgery is reserved only to PAVMs amenable to embolization. In many sites, the procedure is carried out under local anesthesia, on outpatient basis (4, 10, 11). Several minimally invasive approaches to embolization have been proposed depending mostly on PAVM angioarchitecture, with feeding artery embolization serving as the gold standard. The embolic materials used nowadays include pushable and interlocking detachable coils (IDC), as well as AMPLATZER Vascular plugs. The mechanism of action and hemodynamic effects of the latter resemble mechanism of detachable balloons which were withdrawn from the market. The results of procedures carried out with AMPLATZER devices are very promising, with the reported rates of immediate technical success of 100%, low reperfusion rates of 0-7% and rare occurrence of serious complications (6, 10, 15).
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Piśmiennictwo
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