Endovascular treatment of pulmonary and cerebral arteriovenous malformations in patients affected by hereditary haemorrhagic teleangiectasia.
Hereditary Haemorrhagic Teleangiectasia (HHT) is a vascular disorder of angiogenesis transmitted in an autosomal dominant pattern, characterised by heterogeneity in clinical manifestations. One of the most important organ involved is lung, including pulmonary arteriovenous malformations (PAVM). PAVM occur in 20 to 30% of the HHT population and recently are considered a marker of disease. PAVM are direct artery-to-vein connections with low pressure and without an interveining capillary bed. PAVM are classified as simple (supplied by one feeding artery) or complex (receiving blood supply from two or more feeding artery). According to the international reports, treatment it's recommendable for all PAVM with feeding vessels 3mm or larger, in order to reduce the risk of cerebral ischaemia and neurologic manifestations frequently attributed to paradoxical embolisation. Transcatheter embolotherapy of PAVM is a form of treatment based on occlusion of the feeding artery to a PAVM by using platinum coils or detachable balloons. The technique of coil embolisation involves the exact localisation of PAVM by pulmonary angiography followed by superselective percutaneous caheterisation of feeding artery obtained by using a dedicated 7F guiding catheter, which coaxially allocates a 5F hydrophilic catheter advanced in order to perform both superselective angiography of feeding artery and embolisation itself. Inside the 5F catheter the platinum coils are advanced using a .035'' guide-wire and released until an optimal occlusion of feeding artery is achieved. At the end of the procedure angiographic control is performed in order to verify the occlusion of feeding artery. The use of platinum coils is preferable over detachable balloons when feeding artery are greater than 7 mm in diameter and have irregular anatomical configuration. On the other hand, the principal advantage of using detachable balloons is that the balloon itself can be deflated and repositioned if necessary. Transcatheter embolotherapy is technically safe and clinically effective and may represent the primary choice of treatment in HHT patients. On the other hand the most common complications of this treatment (pleurisy and air embolism) can be prevented by using some tips during the embolisation procedure like "anchor technique," "scaffold technique" and "balloon assisted technique." Cerebral arteriovenous malformations (CAVM) are present in 10-20% of patients with HHT and multiple in 50% of cases. Cortical surface is the most frequent localisation. Angiography is needed to diagnose all CAVM and to clarify the angioarchitecture of the lesion. In HHT CAVM are usually either micro-AVM, with a nidus not bigger than 1 cm, or small AVM, with a nidus between 1 and 3 cm. Quite frequently there are lesions characterised by arteriovenous fistulas. In the three patterns of CAVM usually found in HHT, small AVM are the most risky for bleeding although the risk is lower than that associated with sporadic ones. It is estimated from 0.38 to 0.69% per year in spite of the general incidence of bleeding in sporadic CAVM that ranges from 2 to 4% per year. In HHT patients, at present, the precise indications and timing of treatment are not established. Trend is to treat small AVM and AVF and to follow-up micro-AVM with MRI and angiography. As for sporadic CAVM, treatment of small AVM is usually referred to stereotactic radiosurgery. Endovascular embolisation is proposable if the lesion is easily reachable by microcatheterism and the position of the microcatheter is safe. Glue is used for embolisation and the technique is briefly discussed.