Small coronary artery-pulmonary artery fistula

Anyone with a little medical knowledge knows that pulmonary arteriovenous fistula is a congenital pulmonary vascular malformation, which is extremely harmful to the human body. Pulmonary arteriovenous fistula can be understood as the enlargement and tortuosity of blood vessels or the formation of cavernous hemangioma. In short, it is a short circuit caused by the direct connection between the vein and the pulmonary artery without passing through the alveoli. This disease is extremely harmful to the patient's physical and mental health. This deformity is related to the direct connection between various veins and pulmonary arteries.

The blood from the pulmonary artery flows directly into the pulmonary vein without passing through the alveoli, and the pulmonary artery and vein are directly connected to form a short circuit. It was first discovered and described by Churton in 1897 and is called multiple pulmonary artery aneurysms. In 1939, Smith confirmed this disease using cardiovascular angiography. There are many names in the literature, such as pulmonary arteriovenous aneurysm, haemagiectasis of the lung, and haemonreac telangiectasia with pulmonary artery aneurysm. In addition, this disease is familial and related to genetic factors, such as hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber disease).

This malformation consists of direct connections between the pulmonary arteries and veins of varying sizes and numbers. The most common ones are 1 artery and 2 veins. There is no capillary bed between the two. The muscular layer of the diseased blood vessel wall is poorly developed and lacks elastic fibers. The pulmonary artery pressure causes the diseased blood vessels to progressively dilate. Pulmonary arteriovenous aneurysm is a type of direct connection between pulmonary arteriovenous branches, characterized by twisted and dilated blood vessels, thin arterial walls, thick venous walls, cystic enlargement of the aneurysm, septa of the aneurysm, and visible thrombus. The lesions can be located in any part of the lungs, with thickening of the tumor wall, but the reduction, degeneration or calcification of the cortex in a certain area may lead to rupture. There is also a rare and special type in which the right pulmonary artery communicates directly with the left atrium.

The lesions are distributed in one or both lungs, single or multiple, and can be 1 mm in size or involve the entire lung. They are commonly found in the subpleural area of ​​the right and both lower lobes and the right middle lobe. About 6% of this disease is accompanied by Rendu-Osler-Weber syndrome (multiple arteriovenous fistulas, bronchiectasis or other malformations, absence of the right lower lobe of the lung and congenital heart disease).

The main pathophysiology is the shunting of venous blood from the pulmonary artery into the pulmonary artery, with the shunting volume reaching 18% to 89%, resulting in a decrease in arterial oxygen saturation. There is generally no ventilation disorder and PCO2 is normal. In most cases, hypoxemia leads to polycythemia, and due to the direct communication between the lungs and systemic circulation, it is prone to complications such as bacterial infection and brain abscess.

Performance

This disease is more common in young people. Those with small shunt flow may be asymptomatic and only discovered during lung X-ray examination. Those with a large shunt may experience tachypnea and cyanosis after activity, but these symptoms usually occur in childhood and are occasionally seen in newborns. Hemoptysis is caused by lesions of telangiectatic lesions located in the bronchial mucosa or rupture of pulmonary arteriovenous fistula. Chest pain may be caused by rupture of the lesion and bleeding under the pleura in the lung layer or hemothorax. About 25% of cases experience neurological symptoms, such as convulsions, speech disorders, diplopia, temporary numbness, etc., which may be caused by polycythemia, hypoxemia, vascular embolism, brain abscesses, and bleeding from cerebral capillary dilation lesions. Patients with familial hemorrhagic telangiectasia often have bleeding symptoms, such as epistaxis, hemoptysis, hematuria, vaginal and gastrointestinal bleeding. Bacterial endocarditis may also occur due to the presence of fistula. Careful auscultation of the affected area may reveal a systolic murmur or a biphasic continuous murmur in about 50% of cases, which is characterized by the murmur increasing with inspiration and decreasing with expiration. Other features include clubbing of fingers and toes, polycythemia, increased hematocrit, and decreased arterial oxygen saturation.

Classification

Type I multiple telangiectasia: diffuse and multiple, formed by the anastomosis of capillary terminals, with a large short-circuit shunt volume.

Type II pulmonary artery aneurysm: formed by the anastomosis of larger blood vessels closer to the center, it expands like a tumor due to pressure factors, and the short-circuit shunt volume is greater.

Type III communication between pulmonary artery and left atrium: The pulmonary artery is significantly enlarged, the short-circuit shunt volume is extremely large, and the right-to-left shunt volume can account for 80% of the pulmonary blood flow, often accompanied by abnormalities of the lung lobes and bronchi.

41. Coronary Sinus Rhythm

Under the fast-paced lifestyle, cardiovascular disease has become a common disease among modern people. Cardiovascular pain is generally characterized by rapid onset and great harm. It is generally believed that coronary sinus rhythm is a special atrioventricular junctional escape rhythm. So what are the signs of coronary sinus rhythm? Can the coronary sinus rhythm be accurately observed through electrocardiogram? Let us learn about the knowledge related to coronary sinus rhythm through this article.

The coronary sinus is the entrance of the coronary vein into the right atrium. If the automaticity of the tissue near the coronary sinus increases and there are more than three consecutive coronary sinus beats, it is called coronary sinus rhythm.

definition

Coronary sinus rhythm is considered to be a special type of escape rhythm originating from the atrioventricular junction of the coronary sinus and the left atrium, respectively. Their common electrocardiographic characteristics are retrograde P wave (Ⅱ, Ⅲ, aVF, inverted P wave), PR interval >0.12s, and heart rate 40-50 beats/min.

symptom

Signs:

Coronary sinus rhythm is more common in normal people, presenting as short bursts, and will turn into sinus rhythm when the sinus rate accelerates. The clinical significance is the same as escape rhythm. Some scholars believe that coronary sinus rhythm is more common in patients with venous malformations such as persistent left superior vena cava and absence of inferior vena cava.

ECG features:

The P wave, II, III, and aVF are inverted, the P wave and aVR are upright (occasionally flat or biphasic), the QRS complex duration is normal (such as without intraventricular aberrant conduction or bundle branch block), and the PR interval is >0.12 seconds. This is because the impulses emitted near the coronary sinus must pass through the atrioventricular junction to reach the ventricles, and the distance is longer, so the PR interval is also normal. The impulse sent from the junction reaches the ventricles, which has a shorter distance to travel and takes less time, so the PR interval is less than 0.12 seconds. If the impulse emitted from the junction is accompanied by forward block, the PR interval may also be >0.12 seconds, which makes it difficult to distinguish it from coronary sinus rhythm.

Common causes:

Clinically, coronary sinus rhythm is common in acute rheumatic fever, digitalis poisoning, and acute inferior myocardial infarction.

Disease identification:

Coronary sinus rhythm should also be distinguished from left atrial rhythm. The P wave, I, and V6 of the left atrial rhythm are inverted, while the previous and next P waves, I, and V6 are upright.