Pulmonary arteriovenous fistula

Introduction to pulmonary arteriovenous fistula Pulmonary arteriovenous fistula is a congenital pulmonary vascular malformation. The blood vessels are enlarged or distorted or form a cavernous hemangioma. The pulmonary blood flows directly into the pulmonary vein without passing through the alveoli, and the pulmonary artery directly communicates with the vein to form a short circuit. First described in 1897 by Churton, known as multiple pulmonary aneurysms. In 1939, Smith applied cardiovascular angiography to confirm the disease. There are many literature names, such as pulmonary arteriovenous tumor, pulmonary vasodilatation (haemagiectasisoft helung), telangiectasia with pulmonary aneurysm (haemonreactelangiectasia with pulmonaryarteryaneurysm). In addition, the disease is familial and is associated with genetic factors such as hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber disease). basic knowledge The proportion of illness: 0.0003% Susceptible people: no special people Mode of infection: non-infectious Complications: atelectasis

Causes of pulmonary arteriovenous fistula

Vascular wall muscular dysplasia (30%):

This malformation is directly connected by a variety of different sizes and unequal numbers of pulmonary arteries and veins. Commonly, one artery and two veins. There is no capillary bed between the two. The muscular wall of the diseased vessel wall is poorly developed, lacking elastic fibers, and the pulmonary artery pressure promotes the progressive expansion of the diseased blood vessels. Pulmonary arteriovenous sinus is a type of direct arteriovenous branch, which is characterized by vascular distortion, dilatation, thin arterial wall, thick vein wall, cystic enlargement of the tumor, and tumor separation. The lesion can be located in any part of the lung, and the wall of the tumor is thickened, but the endothelial layer is reduced, denatured or calcified in a certain area, which is the cause of the rupture.

Lung lesions (25%):

The lesions are distributed on one or both sides of the lung, single or multiple, and may be 1 mm in size or involving the entire lung, the subpleural area of the right and second lower lobe, and the right middle lobe. About 6% of the disease is associated with Rendu-Osler-Weber syndrome (multiple arteriovenous fistula, bronchiectasis or other malformations, lack of right lower lobe and congenital heart disease).

Pulmonary arteriovenous fistula prevention

The disease is a group of congenital pre-diseases, so the prevention of this disease is mainly the prevention of its complications. The main complications after pulmonary arteriovenous fistula resection can occur before, during and after surgery, as long as positive measures can be taken to prevent or reduce. Therefore, patients should be treated with antibiotics before surgery to reduce cough and expectoration. Train patients to have effective cough and expectoration. After surgery, encourage and assist patients to effectively cough and reduce complications to a minimum.

Pulmonary arteriovenous fistula complications Complications of atelectasis

1. The complications of pulmonary surgery after pulmonary arteriovenous fistula are as follows:

(1) atelectasis

Mainly due to postoperative cough and weakness, bronchial endocrine secretions and small clots are not well discharged, causing bronchial obstruction, patients feel shortness of breath or hernia, auscultation of local lungs is weak or disappear, the trachea can be biased to the affected side, bedside chest X-ray Perspective can be confirmed. Postoperatively, patients should be encouraged and assisted to have effective cough, and coughing up the bronchial bloody thick sputum. The sputum is not easy to cough up. The mucosolvan 15mg plus distilled water 30ml can be inhaled twice a day.

(2) empyema

(1) Inadvertent operation during operation makes the cancer, abscess or tuberculosis cavity collapse and contaminate the chest cavity. If the chest cavity is not completely flushed before the chest is closed, the patient's body is very weak, the resistance is low, and the pleural cavity can be infected into empyema.

(2) After the lung resection, the bronchospasm on the surface of the residual lung, such as the rough surface after the lung segment resection and the lung suture edge after the wedge resection, does not close the healing for a long time, it is easy to infect the pleural cavity to form empyema. In particular, postoperative respiratory insufficiency requires a ventilator for continuous assisted breathing. Because of the certain pressure in the lungs, the fistula is less likely to heal, and it is easy to form an empyema for a long time. Once a hyperthermia forms an empyema, a closed drainage or a thoracic puncture should be performed as soon as possible to re-expand the lung and close the abscess.

Pulmonary arteriovenous fistula symptoms Common symptoms Dizziness, shortness of breath, difficulty breathing, shortness of breath, chest pain, fatigue, convulsions, action wall

1 The disease is more common in young people, and the small flow rate can be asymptomatic, only found in the X-ray examination of the lungs. Those with large flow rate may have shortness of breath and cyanosis after the activity, but most of them appear in childhood, occasionally in newborns. Most patients have purpura from childhood, gradually increasing with age and have difficulty breathing.

225% of patients had neurological symptoms such as convulsions, ataxia, and diplopia.

335% to 50% of patients have familial hereditary hemorrhagic telangiectasia symptoms such as epistaxis, hemoptysis, hematuria, and gastrointestinal bleeding.

4 When the pulmonary arteriovenous fistula ruptures, the patient may have chest pain and hemothorax.

5 If the sputum is large, the systolic or continuous murmur can be heard at the location of the sputum.

Pulmonary arteriovenous fistula examination

(1) X-ray performance

It is characterized by isolated or multiple rounded shadows, varying diameters of shadows, uniform density, clear edges, or shallow lobes; dilated and thickened feeding arteries and drainage veins connected to the shadow, and the blood supply artery is connected to the hilar; The shadow generally does not increase or only increases slowly.

(2) pulmonary angiography

Pulmonary angiography is a reliable method for the diagnosis of PAVMs. Pulmonary angiography can determine the extent and extent of the lesion, morphology, and involvement, and provide a basis for the choice of clinical treatment methods. The contrast method is classified into selective or superselective pulmonary angiography. Generally, selective primary pulmonary angiography is performed first, and the right position is projected. The entire lung field of both lungs should be included in the projection to avoid missing the lesion.

(3) Cardiac catheterization and cardiovascular angiography

Arterial oxygen saturation decreased. There is no intracardiac shunt in the heart beat volume and heart chamber pressure. The pigment dilution test can be used to test the flow rate and location, taking care to avoid the catheter entering the sputum and alert to the risk of rupture. Intra-arterial injection of contrast agent can show the location and size of arteriovenous fistula, showing dilated, elongated, and distorted blood vessels.

Diagnosis and differentiation of pulmonary arteriovenous fistula

diagnosis:

In clinical terms, the disease can be divided into three types, namely:

Type I: multiple telangiectasia, diffuse, multiple, formed by capillary tip anastomosis, and its short-circuit flow is large.

Type II: Pulmonary aneurysm, which is formed by an anastomosis of a larger vessel near the central center. The tumor is dilated due to pressure factors, and the short-circuit flow is larger.

Type III: Pulmonary artery and left atrial communication, the pulmonary artery is significantly enlarged, the short-circuit flow is extremely large, and the right-to-left flow can account for 80% of the pulmonary blood flow, often accompanied by abnormalities of the lung and bronchus.

Differential diagnosis:

Clinically, the disease needs to be differentially diagnosed with the following diseases:

(1) intrapulmonary metastases

Pulmonary arteriovenous fistula, especially multiple pulmonary arteriovenous fistula, its chest CT shows multiple lesions in the lungs, which are easily misdiagnosed as intrapulmonary metastases. It should be identified according to its medical history and blood gas analysis. In particular, we must distinguish the difference between the two on CT.

(2) Tuberculosis

The main distinguishing points of PAVF and other types of tuberculosis are:

(1) Tuberculosis often has symptoms of fever, anorexia, fatigue, night sweats, etc., while PAVF is rare.

(2) The rate of red blood cell sedimentation and white blood cells in patients with active tuberculosis are mild to moderately elevated, while PAVF generally has no significant changes.

(3) PPD test in tuberculosis patients is more positive, while PAVF is generally negative.

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