PAVF refers to the fact that the pulmonary artery and pulmonary vein do not communicate through the capillary network, but directly through the enlarged tortuous blood vessels or hemangioma, which incidence is low. PAVF can be divided into three types: single type, complex type and diffuse type. More than 80% of PAVF patients belong to single type: one artery and one vein are connected, and the cystic tumor is not divided; Complex type refers that the lesion is not limited to one artery and one vein, and the cystic tumor is usually separated; Diffuse type refers to the presence of extensive small pulmonary arteriovenous fistulas without cystic tumor formation [4–5]. The severity of PAVF is directly related to fistula size. A single fistula less than 2cm in diameter usually does not cause symptoms. When the right-to-left shunt volume increases with the enlargement of the fistula, the symptoms such as dyspnea and cyanosis may gradually appear, and the patient's exercise tolerance gradually decreases. About 25% of patients also experience neurological symptoms such as cerebral embolism, transient ischemic attack, migraine, and brain abscess. Pulmonary artery CTA is the preferred method for the diagnosis of PAVF, which can reveal the overall situation of the lesion and measure the diameter of the diseased vessels. Pulmonary vascular DSA is the gold standard for the diagnosis of PAVF, which can observe the fistulas, feeding arteries and draining veins of PAVF.
After diagnosis, most PAVF patients need treatment. The mortality rate of untreated PAVF patients could be as high as 50%, while it could be reduced to 3% after treatment [6]. Current treatments for PAVF include surgery and interventional therapy. The recurrence rate of surgical treatment is low, but it is limited to the treatment of single lesion, and the trauma is large. Interventional therapy could retain more lung tissue and has less trauma, but it is not suitable for more lesions and diffuse lesions. Interventional therapy was the first successful treatment for PAVF in 1978. With the continuous improvement of surgical techniques and interventional materials, interventional treatment of PAVF has been proved to be safe and effective, and has become the first choice in clinical practice [7–10]. Interventional therapy for PAVF is mainly divided into coil occlusion and occluder occlusion. For PAVF patients with feeding artery diameter < 5 mm, coil closure is recommended. For PAVF with the diameter of feeding artery ≥ 5 mm, the use of coil will increase the risk of its detachment and displacement or even ectopic embolism, and the use of occluder is more effective and safe [11]. At present, the conservative treatment of diffuse PAVF is mainly to improve the symptoms of hypoxia. In this case, the the narrowest diameter of the feeding artery was about 10mm through pulmonary vascular DSA. Therefore the Shenzhen Xianjiang patent ductus arteriosus occluder (XJFD1618) was used for occlusion. After occlusion, the shunt was significantly reduced and the patient's blood oxygen saturation increased rapidly. In the end, the patient's symptoms were significantly improved.
The main clinical manifestations of this patient were chest tightness and shortness of breath after activities which accorded with the common symptoms of CHD. And the primary clinical diagnosis was CHD. Coronary angiography showed that the patient had severe stenosis of the anterior descending artery and the right coronary artery which were consistent with the symptoms, and interventional treatment was given. However, the patient was also complicated with type Ⅰ respiratory failure, and pulmonary artery CTA showed arteriovenous malformation in the right lower lobe of the lung, which was considered to have PAVF. Pulmonary vascular DSA was performed to confirm the diagnosis of right PAVF, and the patient was treated with occlusion. After the operation, the patient's hypoxemia and symptoms were significantly improved.
PAVF is a rare disease, and its symptoms are lack of specificity. For elderly patients with CHD, hypertension and other common cardiovascular diseases, PAVF is easy to be ignored. Therefore, for patients with unexplained hypoxemia, the possibility of PAVF should be considered, and various auxiliary examinations should be improved to avoid missed diagnosis. On this basis, intervention treatment should be carried out to improve the prognosis of patients as much as possible.