CONGENITAL CORONARY ARTERY FISTULA
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An asymptomatic three year old male child was referred for investigation of a cardiac murmur discovered accidentally by his general practitioner. He was the only child of non-consanguinous parents. The ante-natal and post-natal periods were uneventful and developmental milestones were normal. On clinical examination hypertelorism, a flat nose and nasal bridge depression were noted. The pulse rate was 80/min. and blood pressure 90/60 mm of Hg. Heart sounds were normal. An early systolic and holo-diastolic murmur were heard over the left 3rd intercostal space just lateral to the sternum.
On chest x-ray an increased cardiothoracic ratio and left ventricular enlargement were detected. ECG was within normal limits with no evidence of ischaemia. Echocardiography demonstrated a dilated right coronary artery and normal cardiac chambers. Doppler studies showed turbulent flow within the left ventricle cavity.
Cardiac catheterization and cine-angiography was performed by right femoral artery puncture and a selective right coronary angiogram in RAO and LAO done. It showed a dilated right coronary artery measuring one third of the size of the aorta, draining into the left ventricular cavity. The opening into the left ventricular cavity was being intermittently narrowed. The left coronary ostium could not be engaged. On aortic root injection, there was no aortic regurgitation and the LCA was not well visualised.
A diagnosis of coronary artery fistula from RCA to left ventricle was made and the patient referred for surgery.
Congenital fistulae between a coronary artery and a cardiac chamber is an uncommon anomaly, the incidence of which has apparently increased with the more frequent performance of selective coronary catheterization. When the fistula drains into a left sided cardiac chamber, it is designated an aorto-systemic fistula, since aortic blood flows into a systemic cardiac chamber.
KRAUSE in 1865 first described a coronary artery fistula (CAF). ABBOTT in 1908 and TREVOR in 1912 published early accounts of this condition. BJORK and CRAFOORD in 1947 first successfully performed surgical closure of a CAF draining into the pulmonary artery in a patient with a preoperative diagnosis of patent ductus arteriosus !
Congenital coronary artery fistulae have been estimated to occur in 1 in 50,000 patients with congenital heart disease, and in 1 in 500 patients undergoing coronary arteriography. Around 90% of these fistulae drain into the right heart chambers, and many reports have found a prevelance rate of only 6 to 8% for CAF draining into the left heart. The condition is found with equal incidence in males and females and is frequent below 10 years of age. 10% of CAF have angiomatous changes and 19% show aneurysmal dilatation.
Why CAF occur is still quite a mystery. Many theories have been proposed. Multiple CAF may be a persistence of embryonic intra trabecular sinusoids, due to a developmental arrest in localized areas of embryonic myocardium. This permits coronary vessels to communicate through Thebesian vessels with the cardiac chambers. Another explanation is the faulty development of the distal branches of the involved coronary artery (the rectiform vascular network). Acquired CAF are seen in varied conditions including trauma, surgery, endomyocardial biopsy and acute myocardial infarction.
CAF draining into the left ventricle are usually small in size, owing to the similar diastolic pressures in the coronary artery bed and the left ventricle cavity. Aneurysmal dilatation however may occur due to structural weakening of the vessel wall due to increased blood flow, and in extreme cases even lead to rupture of the dilated vessel. The hemodynamic burden of CAF to LV is diastolic overload of the LV, a condition analogous to aortic valve regurgitation. More dangerous, and of clinical importance, is the propensity of these fistulae to deprive the distal coronary bed of antegrade perfusion, leading to myocardial ischemia - the so-called "steal" phenomenon.
The clinical presentation of LV-CAF is highly varied. Most of the patients are asymptomatic, and the lesion is detected on routine examination by a physician. The factors determining the behaviour of CAF are the size of the communication, the amount of blood drained through it, the resistance of the recepient chamber and development of myocardial ischemia. Dysnea on exertion, or frank congestive cardiac failure is a frequent presentation, especially in patients above 40 years of age. CAF-LV causing CCF has been described even in a neonate, and is a correctable cause of failure necessitating early diagnosis. Exertional angina is a manifestation of shunting of blood away from the coronary circulation causing the development of a pressure gradient across the capillaries. There is also a questionable association between CAF and LV dysfunction. Atrial fibrillation, palpitations, frequent respiratory infections and infective endocarditis are uncommon manifestations of the condition. Catastrophic hemorrhage following rupture and sudden death are fatal complications.
Clinical recognition of CAF-LV is based on the presence of a cardiac murmur. Often it is the detection of a murmur that prompts further evaluation of an otherwise aysmptomatic individual. A continuous murmur may be present over the left precordium, causing confusion with other conditions like patent ductus arteriosus and ruptured sinus of Valsalva aneurysms. Sometimes only an early diastolic murmur is detectable because the fistulous opening closes when the ventricle contracts during systole. An atypical systolic murmur has also been reported. Many times, there may be no detectable murmur.
A chest x-ray may show left ventricular enlargement, cardiomegaly or may be normal. Very rarely calcification of the fistula is visible or enlargement of the tortuous coronary artery with a saccular aneurysm may be seen as a silhouette on the left cardiac margin. An electrocardiogram may reveal left ventricular hypertrophy. Stress Thallium imaging may demonstrate a persistent perfusion defect in the region of ischemia.
Until recently, coronary arteriography remained the only method to definitely diagnose this rare anomaly. By this procedure, the involved coronary artery can be radiologically demonstrated as can the recepient cardiac chamber and the exact site of communication, all of importance in planning surgical therapy.
Recently, the role of echocardiography in diagnosing CAF-LV has been emphasised. Combined two dimensional and pulsed Doppler echocardiography demonstrates the dilated coronary artery, turbulent flow in the fistula and the recipient chamber. Due to technical difficulties correct recognition has not always been possible. Trans-esophageal echocardiography, by opening a "new window to the heart", provides better image quality and helps detect CAF to the left ventricle.
The question of choice of treatment for CAF-LV has not been satisfactorily answered and raises a point for debate. No single series has been large enough to draw reasonable conclusions. The source most frequently quoted to justify surgical closure of CAF is the multi-center study of LIBERTHSON et al. According to this reviewer, as patient age increases to above 20 years, appreciably more problems related to the fistula occur and operative risk and postoperative complications increase. However, no specific recommendation regarding CAF-LV has been made, and many cases reported in the literature have not been definitively treated. Surgical treatment has been suggested for all patients to prevent congestive cardiac failure, angina, myocardial infarction, endocarditis, pulmonary hypertension, aneurysms of the coronary arteries, vessel rupture, dissection, premature atherosclerosis and thrombosis in the dilated artery. Any additional lesions present can be corrected simultaneously. Also, the risk of surgery is less than that of asymptomatic patients developing serious and potentially fatal complications.
The goals of treatment are obliteration of the fistula while preserving normal coronary blood flow. A spectrum of surgical procedures to correct CAF-LV have been reported.
Some operations may be done on the beating heart. When the fistula can be correctly localized, tangential arteriorrhaphy can be done by taking multiple horizontal mattress sutures under the area where the thrill can be felt. This is useful in lateral fistulae. Proximal and distal ligation of the involved coronary artery was done earlier, but is not advocated because of the risk of myocardial ischemia developing distally. Distal ligation alone is useful when the fistula arises from the terminal end of the involved coronary artery. Suture obliteration of the communication en masse or excision of the entire mass of vessels was also done in some cases.
In view of the improved and standardized technique of cardiopulmonary bypass, presently it should probably be employed routinely in most instances. It is usually needed in older patients and in those where the fistula is not easily detected intraoperatively or not accessible.
Internal closure , or suture closure from within the chamber of drainage, is now the preferred procedure in many cases. After cardioplegic arrest of the heart, the internal opening can be identified by temporarily releasing the aortic cross clamp. This technique is indicated when the fistula drains into a cardiac chamber, when identification on the surface is difficult or in case of multiple CAF.
Another option is to ligate or excise the fistula, and restore distal coronary perfusion by an aorto coronary bypass graft.
SYMBAS' operation is the ligation of the fistula by suturing within the dilated coronary artery. Through a coronary arteriotomy over the site of the fistula, the abnormal opening is sutured and the excess arterial wall is trimmed followed by closure of the arteriotomy.
Aneurysmal dilatation of the coronary artery can be dealt with similarly by a reduction arterioplasty and an aorto coronary bypass distally if required. Angiomatous masses may be treated by plication using horizontal mattress sutures and Teflon felt strips.
Complications of surgical closure include arrhythmias, perioperative ischemia and infarction, or thrombosis of the coronary artery with distal embolism. Usually there are no long term problems.
In accord with the current trend toward minimal intervention, transcatheter embolisation of CAF using detachable balloons and implantable trefoil coils has been tried in cases with drainage into the right heart chambers. Very rarely, spontaneous closure or stenosis of a previously documented fistula has been reported.
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