The blood flow of the heart is supplied by a wide myocardial trabecular gap composed of many endothelial cells in the myocardium, and this sinus-like gap is connected with the heart chambers and epicardial vessels. The sinus gaps are gradually compressed and evolve into tiny ducts, which gradually form part of the normal coronary blood circulation. If a wide localized sinus gap remains during the developmental disorders of the heart, so that abnormal traffic exists between the coronary artery system and the heart chambers, a coronary artery is formed that communicates directly with the heart chambers through an abnormal fistula, which is called a coronary artery fistula.
The fistula becomes progressively larger with age. The hemodynamic impact of a coronary fistula depends mainly on the size of the fistula and the site of entry. Fistulas into the atria have a larger fractional flow than fistulas into the ventricles because of the low intra-atrial pressure, thin atrial walls, and high volume expansion. Fistulas into the right ventricle tend to have more fractional flow than those into the left ventricle.
If a coronary artery fistula communicates with the right ventricle, there is a left-to-right shunt during both systole and diastole, which increases the right heart load and increases pulmonary blood flow, and long-term left-to-right shunts can lead to pulmonary hypertension. It can be complicated by congestive heart failure with age. Coronary artery fistulas do not produce a left-to-right shunt when they communicate with the left heart, and both systolic and diastolic flow through the fistula into the left atrium or diastolic flow into the left ventricle only increases the left heart load.
This phenomenon of coronary artery “stealing” may reduce myocardial perfusion, resulting in localized myocardial insufficiency in some patients; or due to combined coronary aneurysm formation, blood may accumulate in the aneurysm during diastole and may This can lead to myocardial ischemia due to compression of the myocardium and distal coronary arteries. Thrombus may also form in the aneurysm, and blockage or dislodgement of the thrombus may cause embolism of the distal coronary artery and myocardial infarction.
In congenital coronary artery fistulas, the heart may have varying degrees of enlargement, particularly left ventricular enlargement and hypertrophy, and dilatation of the ascending aorta. On the surface of the heart, the proximal portion of the abnormally trafficked coronary artery is enlarged and varicose, the wall is thinned, and sometimes a spindle-shaped aneurysm may form.
The heart enlarges to varying degrees due to the effects of abnormal blood flow in the coronary artery fistula. Patients experience reduced blood flow in the distal coronary arteries as the coronary artery faces a high-resistance myocardial vascular bed that turns into a low-resistance fistula and flows directly back into the connecting heart chambers, resulting in coronary artery steal and corresponding myocardial ischemic manifestations. Fistulas into the left ventricle can lead to increased left heart load and, in severe cases, left heart insufficiency.
Natural closure of congenital coronary fistulae is rare. Complications such as bacterial endocarditis can occur. In an analysis by Liberthson et al. of 173 cases (mean age 24 years), 6% died due to coronary artery fistula, with a mortality rate of 1% in patients under 20 years of age and 14% in adults over 20 years of age (mean age 43 years). Surgical treatment of coronary artery fistulas is effective, with an operative mortality rate of less than 2%, a postoperative myocardial infarction rate of about 3%, and a postoperative residual leak or recurrence rate of about 4%.
It has been shown that only 19% of patients develop symptoms before the age of 20 and 63% develop symptoms of varying degrees after the age of 20; up to 59% are asymptomatic before the age of 20 and only 21.8% are asymptomatic after the age of 20. Coronary fistulas occasionally close spontaneously, and the mechanism may be local myocardial closure of the vessel, fibrosis surrounding the fistula tract, or thromboembolic closure.
There are three clinical types of fistulae: 1 single fistula, 2 multiple fistulae, 3 fistulae located lateral to the main branch of the coronary artery forming a lateral traffic with the heart cavity, or coronary arteries that are significantly dilated and form a coronary aneurysm, where the exact location and size of the fistula cannot be determined from the surface of the heart. Fistulas are classified according to their coronary artery origin as right coronary artery fistula, left coronary artery fistula, single coronary artery fistula, multiple coronary artery fistula, and unspecified coronary artery fistula.
According to the location of fistula drainage, they are classified as coronary artery-right atrial or coronary sinus fistula, coronary artery-right ventricular fistula, coronary artery-pulmonary artery fistula, coronary artery-left atrial fistula, and coronary artery-left ventricular fistula. According to the presence or absence of other intracardiac malformations, there are isolated coronary artery fistulas, including traffic between the coronary artery and the heart chambers and pulmonary arteries, and secondary coronary artery fistulas with aortic or pulmonary artery root atresia and intact ventricular septum. Secondary coronary arteriovenous fistulas account for approximately 20% of congenital coronary arteriovenous fistulas.
Clinical features
1. Symptoms
The timing and severity of clinical symptoms are closely related to the size of the fracture, the abnormal traffic location of the fistula, and the presence of other congenital cardiovascular malformations. A large shunt can lead to pulmonary hypertension and heart failure; some patients with a small shunt may even be asymptomatic for life. Clinical symptoms are not specific, but infants have irritability and sweating. Adults generally have palpitations after activity, upper respiratory tract infection, pulmonary hypertension, etc.; in severe cases, congestive heart failure occurs, with an incidence of 18.3%, mostly in patients aged 40 to 50 who are engaged in heavy physical labor; even syncope and sudden death. Clinical right coronary artery fistula is common, about 50-60%. More than half of the patients may be asymptomatic and only have a heart murmur on physical examination, but those with a large left-to-right shunt may have palpitations, angina and heart failure symptoms after physical activity. Atrial fibrillation is likely to occur in patients with fistulas into the coronary sinus.
2. Physical signs
The fistula site varies, the pressure step difference across the fistula and the increased load on each atrium ventricle varies, so the atrial enlargement and hypertrophy varies, so the signs are variable. In most patients with coronary fistula, a continuous murmur with localized tremor or a double systolic and diastolic murmur can be heard in the precordial region. The loudest part of the murmur depends on the site of the coronary artery fistula into the heart and the end pressure difference.
(1) X-ray examination
The hemodynamic profile of coronary artery-right heart and pulmonary artery fistula is a left-to-right shunt at the base of the heart, and the x-ray shows different degrees of increase in pulmonary blood according to the size of the shunt, usually mild to moderate, and the enlargement of the heart is mainly in the left ventricle, often accompanied by enlargement of the left atrium or right ventricle, and the ascending arch of the aorta is often more convex. A small amount of shunt can be within the normal range.
In the case of coronary artery-left ventricular fistula, there are no signs of increased pulmonary blood. Coronary artery-left ventricular fistula is hemodynamically equivalent to aortic regurgitation. In the case of a large shunt flow, the heart is mostly of the “aortic” type, with a mid- to highly enlarged left ventricle, an enlarged ascending arch of the aorta, and an enhanced pulsation of the heart in the form of a “trapped pulse”.
(3) In some cases, the tortuous dilated coronary arteries (especially on the right side) may form the edge of the heart shadow or form an abnormal outward bulge. In a few cases, calcification can be seen in the aneurysmatically dilated coronary arteries.
(2) Echocardiography
Two-dimensional echocardiography can clearly show the dilated coronary artery and trace the course of the coronary artery, while color Doppler is used to observe and discover the location of the fistula, so the combination of two-dimensional echocardiography and color Doppler can accurately diagnose this disease.
(3) Electrocardiographic examination
Left ventricular hypervoltage, left ventricular hypertrophy and biventricular hypertrophy can be seen in cases of high fractional flow. In cases where the fistula is in the right ventricle, there is right ventricular hypertrophy. In those with shunt flow into the right atrium, atrial fibrillation is often present. Although coronary artery fistulas have potential myocardial ischemia, ST and T changes in the ECG are not uncommon.
(4) Cardiac catheterization
There is an increase in the oxygen level in the cardiac chambers of the shunt where the fistula is located. Especially in the right heart system, an increase in oxygen content in the right atrium, right ventricle, or pulmonary artery may be found, indicating the presence and level of the shunt. The size of the shunt can also be measured. It is also possible to measure whether there is an increase in pulmonary artery pressure.
(5) Cardiovascular angiography
Ascending aortography should be the first choice, while selective coronary angiography is required for coarse coronary fistulas. The main signs of angiography are.
(1) The affected coronary artery is obviously tortuous and dilated or aneurysmatically dilated to form a cystic aneurysm. The fistula is usually a single fistula that connects to the heart chambers or great vessels and is aneurysmatically dilated, but rarely two or more multiple fistulas are seen.
Some coronary artery fistulas are not dilated or are mildly tortuous and dilated, and the end lends itself to a network of multiple microvessels that connect to the heart chambers.
The diagnosis of this disease is not difficult, but it needs to be differentiated from ductus arteriosus, aortic sinus aneurysm, main-pulmonary septal defect, and ventricular septal defect combined with incomplete aortic valve closure. Atypical cases can be differentiated with the help of ascending aortography or selective coronary angiography.
Treatment
Coronary artery fistulas should be treated surgically once diagnosed. As patients age, they develop more complications, such as congestive heart failure, bacterial endocarditis, myocardial infarction or fistula rupture, and unexplained sudden death during strenuous exercise, so they should be treated surgically in childhood. This disease combined with other congenital heart disease can be treated surgically at the same time.
1. In asymptomatic infantile patients, surgery can be delayed or in those with small fractional flow, pulmonary circulation blood flow/body circulation blood flow below 1.3 and in asymptomatic patients of advanced age can be operated without surgery. Complications such as coronary aneurysm formation, bacterial endocarditis and heart failure will increase with age, and the safety of surgical treatment is high. Surgical treatment should be performed for confirmed cases.
Early treatment, especially in asymptomatic adolescent patients, and closure of the fistula can eliminate shunts, improve myocardial blood supply, and prevent later symptoms and complications. In addition, patients with coronary artery fistulas combined with coronary aneurysms should be treated with early surgery. The large aneurysm compresses the myocardium and the distal coronary artery causing myocardial ischemia, and the heart gradually enlarges and even heart failure occurs. If thrombus is formed in the aneurysm, thrombus dislodgement may lead to coronary embolism and myocardial infarction.
2, surgical methods: the purpose of surgical treatment of congenital coronary artery fistula is to selectively close the fistula without damaging the normal coronary circulation. In some cases, the fistula can be closed without extracorporeal circulation, and repair under extracorporeal circulation is usually required in the following cases.
(i) fistulas posterior to the heart that are difficult to visualize, such as right ventricular inflow tracts, coronary sinuses, or posterior ventricular wall fistulas;
(ii) If the coronary artery is significantly dilated or combined with a coronary aneurysm, the exact site of the fistula cannot be determined from the surface of the heart, and the fistula needs to be closed by dissecting the dilated coronary artery or dissecting the coronary aneurysm;
The fistula should be closed from inside the heart cavity.
The incidence of residual fistula and myocardial ischemia is the most common complication, which was about 4% and 3.7% in early years. In case of these complications, intraoperative echocardiography and electrocardiography can be used for diagnosis and then surgical treatment.
Interventional treatment
Transcatheter occlusion is an interventional procedure using a spring ring or umbrella to occlude a coronary artery fistula through a catheter. The procedure is less invasive, shorter, and can be discharged in 2 to 3 days with a quick recovery. Now that the technology is mature, a significant portion of these patients can avoid open-heart surgery, which brings a blessing to some patients.