Successful Occlusion of Multiple Pulmonary Arteriovenous Fistulae Using Amplatzer® Vascular Plugs

Pulmonary arteriovenous fistulae, or malformations (PAVMs), are congenital or (rarely) acquired abnormal vascular connections between a pulmonary artery and a pulmonary vein. The fistula itself is typically a thin-walled aneurysmal vascular structure that tends to increase over time. Patients with this condition may be asymptomatic, with the diagnosis being suggested by the presence of a persistently abnormal image in the lung fields on repeat chest radiograms. Others present with symptoms such as cyanosis, dyspnea, high output heart failure, hemoptysis and paradoxical embolization.^1–3 PAVMs occur in isolation or in association with hereditary hemorrhagic telangiectasia, also known as Rendu-Osler-Weber syndrome. They can also be encountered in association with arteriovenous fistulae in other organs including the skin, liver, gastrointestinal tract, brain and mucous membranes.^3,4 Surgical treatment of this malformation by means of a wedge resection, partial or complete lobectomy, and complete pneumonectomy was the single method of therapy available until the early 1980s.^3,5,6 From then on, a variety of percutaneous embolization techniques have been successfully employed to address these lesions. Coils, coil bags, detachable balloons, double umbrellas and Amplatzer devices have been utilized with different degrees of success to occlude such fistulae over the last two decades.^7–10 In this report, we describe a case in which the new Amplatzer® Vascular Plug device (AGA Medical Corp., Golden Valley, Minnesota) was used to close multiple and large PAVMs in a child. Case Report. A 4-year-old boy weighing 18 kg was referred to our institution due to chronic cyanosis and increasing shortness of breath during the previous 6 months. He had been diagnosed with recurrent right lower lobe pneumonia the year before referral. His family history was negative for cardiac diseases. On physical examination, evident cyanosis (oxygen saturation: 79% on room air) and clubbing deformation of the fingers were noted. He had a hyperactive precordium and the first heart sound was normal. There was a 2/6 continuous murmur best heard over the lateral aspect of the right chest. A 12-lead ECG showed left atrial enlargement and left ventricular hypertrophy by voltage criteria, with a ventricular conduction delay. A chest radiogram revealed a slightly enlarged cardiac silhouette and an opaque image in the right lower lobe. An echocardiogram demonstrated an enlarged left atrium and left ventricle and a dilated vascular structure draining into the right side of the left atrium. Left ventricular function was qualitatively hyperdynamic, with an ejection fraction of 78%. The patient was referred for a diagnostic right heart catheterization for further assessment. Right atrial and ventricular pressures were normal, and a pulmonary arteriogram revealed multiple right-sided PAVMs located at the right lower lobe. Two main feeding vessels were identified, and a dilated right lower pulmonary vein draining normally into the left atrium was also noted (Figure 1). An abdominal ultrasound and head CT scan ruled out the presence of aneurysm/fistulae in other locations. Four months later, an interventional catheterization was performed to occlude the fistulae. Under general endotracheal anesthesia, the right femoral vein was cannulated and heparin sulphate administered (100 IU/kg). A 6 Fr Mullins sheath (Cook, Inc., Bloomington, Indiana) was positioned over a 0.035 inch exchange guidewire in the proximal right pulmonary artery. With the aid of a Glidewire^® (Terumo Medical Corp., Somerset, New Jersey) and a 5 Fr right coronary Judkins catheter, both feeding vessels were selectively probed and opacified with repeat contrast injections. At the most proximal site, the superior vessel measured 6 mm and the inferior vessel 9 mm. The long sheath was then positioned distally in the lower feeding vessel. To avoid air entry, special care was taken to remove the Judkins catheter and the Glidewire using a saline seal. A 16 mm Amplatzer Vascular Plug was advanced through the long sheath and exteriorized at the mid-portion of the abnormal larger vessel. While the device was still attached to the delivery cable, its position was checked by repeat contrast injections through the side arm of the long sheath, avoiding inadvertent closure of normal pulmonary arterial branches adjacent to the abnormal feeding vessel. After confirmation of proper positioning, the device was released by unscrewing the delivery cable. The more superior abnormal vessel was addressed with a 12 mm Amplatzer Vascular Plug using a similar deployment technique. A final angiogram demonstrated complete occlusion of both feeding vessels and preserved perfusion of the normal pulmonary arterial branches in the lower right lung (Figure 2). The peripheral oxygen saturation on room air immediately increased from 85% to 96% in the cardiac catheterization laboratory. Cefazolin (30 mg/kg/dose) was given during the procedure and for 2 additional doses. A continuous heparin infusion (20 IU/kg/hour) was maintained overnight, and low-dose aspirin was started the following morning. The patient’s postprocedure recovery was uneventful and he was discharged home 48 hours later. After 5 months, he is asymptomatic on aspirin (5 mg/kg/day), and his peripheral oxygen saturation is 95%. Repeat echocardiography showed a significant decrease in the size of the left atrium and left ventricle. Discussion Treatment of PAVMs is generally indicated when the feeding artery is larger than 3 mm because of a higher probability of paradoxical embolization and neurologic complications.^8,11 Larger fistulae should also be treated due to significant right-to-left shunting resulting in chronic hypoxia with its attendant deleterious systemic effects or high-output heart failure. As such, the indication for treatment was straightforward for the patient described herein. Although percutaneous techniques have progressively replaced the surgical approach for the treatment of such lesions over the last two decades, recanalization of the embolized vessel may occur during follow up, requiring repeat interventional procedures. This is not uncommon when multiple coils have been utilized.¹² In order to minimize the risks of recanalization, larger devices with enhanced thrombogenic features, such as the Amplatzer devices for the occlusion of patent arterial ducts and atrial septal defects have been successfully used to close these fistulae.^10,13 However, these devices were not designed specifically to be used in the peripheral vasculature and are much more expensive than coils. To overcome these limitations, the Amplatzer Vascular Plug was developed as an alternative to implantable coils to treat common peripheral vascular disorders, and its use to occlude aortopulmonary collateral disorders has recently been described.¹⁴ The Amplatzer Vascular Plug is a self-expandable cylindrical device made from an ultra thin nitinol wire mesh and secured on both ends with platinum-iridium marker bands. A stainless steel microscrew welded on the proximal band allows attachment to a 135 cm long delivery cable. Its size ranges from 4 mm to 16 mm in diameter in 2 mm increments, and from 7 mm to 8 mm in length when completely expanded. This device is similar to others in the Amplatzer family in regard to handling, loading, positioning, recapturing and releasing. However, because the polyester fabric layer encountered inside the other Amplatzer devices is lacking in the new Amplatzer Vascular Plug, its flexibility is enhanced. This feature may be important when crossing tortuous peripheral vascular structures. In this regard, the thinner and more flexible stainless steel delivery cable may also be helpful in reaching the target location. Compared to the other Amplatzer devices, the number of nitinol wires was increased from 72 to 144 to promote high thrombogenicity and occlusion rates despite a lack of thinner fabric. It is recommended that the diameter of the device should be at least 50% larger than the diameter of the vessel to be occluded. This may be adjusted according to the intrinsic compliance of the vessel (veins are much more expandable than arteries), and the length of the segment to be treated (larger devices deployed in small vessels tend to elongate). The Amplatzer Vascular Plug comes preloaded in a plastic loader and can be delivered through standard 5 Fr (for 4–6 mm plugs), 6 Fr (for 10–12 mm plugs), and 8 Fr (for 14–16 mm plugs) guiding catheters. Even though it is possible to perform test contrast injections through the guiding catheter using a Touhy-Borst, better visualization of the target vessel may be achieved using a 6 Fr sheath. Due to its larger internal diameter, all plugs, including the 14 and 16 mm, can be advanced through a 6 Fr sheath, as described herein. If the device position is not satisfactory, recapturing and repositioning is possible, enabling precise final release. This is of paramount importance when closing undesired vessels adjacent to normal vascular structures, such as those described in this case. These devices are nonmagnetic and compatible with magnetic resonance imaging technology. Due to its advantageous features, the Amplatzer plugs may be an attractive alternative to close abnormal arterial and venous vessels, including aortopulmonary collaterals, surgical aortopulmonary shunts, anomalous venous-venous connections, peripheral vessels and other arteriovenous malformations or fistulae. In an initial clinical experience, vascular plugs were used in 25 patients to close a variety of undesired peripheral vessels (John Cheatham, MD, personal communication). Complete occlusion was achieved in 43 of 45 vessels (95.6%), with no adverse events. In summary, occlusion of hemodynamically significant multiple PAVMs with the new Amplatzer Vascular Plug was feasible, safe and effective in the case described herein. Longer follow up and larger numbers of patients are required to assess the rate of recanalization and its ultimate efficacy profile.

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