Nonatherosclerotic Coronary Artery Disease

Anomalous Aortic Origin of Coronary Arteries

Approximately one third of all coronary artery anomalies are an anomalous aortic origin. Although multiple variations have been reported, with each of the three major coronary arteries arising from any of the three sinuses of Valsalva, most are benign. The exceptions to this include the right coronary artery arising from the left aortic sinus, and the left main coronary artery arising from the right aortic sinus, both of which are associated with a risk of sudden death.

The incidence of sudden death associated with a left main coronary artery arising from the right sinus of Valsalva has been reported to be as high as 57% and is most commonly seen with exercise. When symptomatic, patients will present with angina, myocardial infarction, congestive heart failure, or syncope. From its origin in the right sinus of Valsalva, the left main coronary artery may pass anterior to the pulmonary artery, posterior to the aorta, between the great vessels, or through the conal septum. This anatomic position is believed to result in ischemia because of acute angulation resulting in a narrowed coronary orifice, compression of the artery from the adjacent great vessels, and compression by the intercoronary commissure.

The incidence of sudden death from the right coronary artery arising from the left sinus of Valsalva has been reported to be as high as 25% and, as with the left main coronary artery arising from the right sinus, is often exercise related. When symptomatic, patients will present with angina, myocardial infarction, conduction disturbances, or syncope. The risk of ischemia is felt to result from ostial obstruction or arterial compression by the aortic root during diastole.

The most common variation in anomalous aortic origin of the coronaries is a circumflex arising from the right sinus of Valsalva, or from the right coronary artery ( Fig. 94-1 ). This condition in general does not manifest with symptoms and is diagnosed incidentally. Because the risk of sudden death is minimal, intervention is not needed.

For all anomalous aortic origins of the coronaries, angiography is needed to delineate anatomy and for surgical planning. In the presence of symptoms, surgery is indicated for all patients. For an anomalous left main coronary artery originating from the right sinus of Valsalva, coronary unroofing is recommended regardless of the presence of symptoms and should be performed urgently if symptoms are present. For patients with an anomalous right coronary artery from the left sinus of Valsalva ( Fig. 94-2 ), surgery should be performed for symptoms, but there remains debate about surgery for the asymptomatic patient. Surgical options include unroofing of the coronary with intimal tacking, aortic reanastomosis, or patch arterioplasty. Proximal ligation of the anomalous coronary with distal bypass grafting is also used but is limited by durability of bypass grafts.

Coronary unroofing with intimal tacking is the currently favored method for correcting an anomalous aortic origin of the left main coronary artery or right coronary artery from the contralateral sinus. After cardiopulmonary bypass grafting is begun, care must be taken when dissecting the aorta from the main pulmonary artery because the aberrant artery may be injured during this dissection. After establishment of cardioplegic arrest, an oblique aortotomy is generally used, but a “hockey-stick” (vertical followed by oblique) aortotomy may be used if there is uncertainty about the course of the aberrant artery to avoid injury. Upon identifying the abnormal origin, a coronary probe is placed in the artery to confirm its course. With the probe in the arterial lumen, the artery is unroofed, using the probe to prevent inadvertent back wall injury. The edges of the unroofed segment are then tacked to the aortic wall with interrupted fine polypropylene suture, thereby creating a new ostium in a more anatomic position ( Fig. 94-3 ).

Anomalous Pulmonary Origin of Coronary Arteries

Single Coronary Artery

Single coronary artery is an extremely rare coronary anomaly, with an incidence ranging from 0.002% to 0.06%, and is associated with other congenital heart defects in as much as 40% of patients. The anomaly can be classified into three types: type 1 describes a single artery supplying the entire heart, type 2 describes a single artery that divides into a right and left coronary artery, and type 3 covers all other variations. Patients will present either with symptoms related to concomitant congenital defects or with angina. Diagnosis is made with coronary angiography. Although some patients will remain asymptomatic, sudden death has been reported secondary to compression between the great vessels, and concerns over angulation and accelerated atherosclerosis have been reported. Percutaneous coronary intervention and coronary artery bypass grafting have been used successfully for the treatment of patients with ischemic symptoms, although no guidelines exist for intervention in asymptomatic patients.

Left Main Coronary Artery Atresia

Congenital atresia of the left main coronary artery is quite rare, with only limited case reports found in the literature. The anomaly may present in infancy with rhythm disturbances, syncope, or sudden death, whereas if there is sufficient collateralization from the right coronary artery, patients may not present until adulthood, at which time ischemic symptoms will manifest. Diagnosis is made with echocardiography and coronary angiography, which allow for differentiation from a single coronary artery and ALCAPA. Surgery is recommended at the time of diagnosis and may consist of distal revascularization with coronary artery bypass grafting or reattaching the proximal left main coronary artery to the aortic sinuses.

High Takeoff Coronary Ostia

The left main and right coronary arteries generally originate from their respective sinuses of Valsalva below the sinotubular junction. Although the incidence varies significantly between series, the coronary arteries may be located significantly above the sinotubular junction in 0.01% to 0.8% of patients. The origin will generally occur within 1 to 2 cm of the sinotubular junction but has been reported to be as high as 5 cm above the sinotubular junction. The clinical significance of this anomaly remains controversial because cases of sudden death with this condition have been reported in patients with concomitant coronary pathology, which may have been responsible for the mortality. In the asymptomatic patient with an isolated high takeoff coronary in whom an incidental finding is made, observation may be warranted.

Coronary Artery Fistula

Coronary artery fistulae may be congenital or acquired, with an incidence ranging from 0.2% to 0.85%. The fistulae consist of a direct precapillary communication between a major coronary artery and a cardiac chamber, a major vessel, or a vein. When drainage occurs into a cardiac chamber, the term coronary-cameral fistula may be used. Currently, approximately two thirds of coronary artery fistulae are congenital and may be associated with additional congenital heart defects in one third of patients. These are thought to develop because of the persistence of sinusoidal connections between the lumens of the tubular heart in early development. Acquired fistulae may develop after trauma, coronary angiography or other catheter-based intervention, myocardial biopsy, vasculitis, or cardiac surgery. Most commonly, fistulae will be single in approximately 80% of cases, with multiple fistulae occurring in 10% to 15% of patients, and dual right-left coronary fistulae occurring in less than 10% of patients. The left anterior descending and right coronary arteries are the most common sites of origin for fistulae, with the circumflex being an infrequent site. Drainage runs into the low-pressure right heart or pulmonary artery in greater than 90% of cases but may rarely run into the left atrium or ventricle. Fistulae may be classified as type A or type B based on the system proposed by Sakakibara and colleagues. In type A fistulae, the coronary artery proximal to the fistula site is dilated, whereas in type B, the coronary is dilated over its entire length, terminating in the right heart. This distinction is of significance clinically because type A fistulae may be ligated on the epicardial surface of the heart, whereas type B should be ligated intracamerally. If fistulae are large, symptoms may appear during childhood, with angina and dyspnea being the most common complaints. Echocardiography is able to identify a fistula, but catheterization is required for surgical planning and obtaining hemodynamic measurements. Although fistulae rarely close spontaneously, intervention (catheter-based or surgical) is favored by most clinicians in younger patients, even if they are asymptomatic, to prevent complications such as ischemia, endocarditis, aneurysm, or pulmonary hypertension. No consensus exists for the management of asymptomatic older patients with incidentally discovered small fistulae, but observation may be appropriate. Successful catheter-based interventions include stenting or coiling and have not been compared with surgical techniques. Surgical techniques are varied and may be performed with or without the use of cardiopulmonary bypass (dependent upon technique). If the coronary artery can be mobilized on the epicardial surface, the fistula may be ligated without the use of cardiopulmonary bypass. Pledgeted mattress sutures may be passed deep into the artery to occlude the fistula without the use of bypass. Internal closure can be performed via arteriotomy if the patient can tolerate temporary proximal and distal occlusion of the coronary artery. Alternatively, the coronary artery may be ligated both proximally and distally with bypass grafting to preserve distal perfusion. Closure can be performed from within the draining chamber with a purse-string suture or patch, both of which require cardiopulmonary bypass.

Muscle Bridge

The “epicardial” coronary arteries are normally located superficially on the epicardial surface of the heart, but in certain patients they may course through the myocardium for varying lengths, with the overlying muscle termed a bridge . Although there exists debate regarding the contribution of muscle bridges to myocardial ischemia, multiple reports demonstrate ischemia secondary to systolic narrowing of the coronary artery from the overlying muscle. In addition to the direct mechanical effects of the bridge, there may be some increase in progression of atherosclerosis proximal to the bridge, which may also contribute to ischemia. The incidence of muscle bridging varies tremendously, from 0.5% to 85%, and is dependent upon the type of study done (angiography versus computed tomography versus autopsy), but muscle bridging with arterial compression is seen in only approximately 0.5% of patients undergoing coronary angiography for evaluation of chest pain. If muscle bridging is suspected, coronary angiography with intravascular ultrasonography should be used to confirm the diagnosis ( Fig. 94-4 ). Although some degree of vessel compression is likely benign, reduction of the coronary diameter by greater than 70% during systole and 35% during diastole suggests significant coronary compression. Medical management remains the first-line treatment for symptomatic muscle bridging and consists primarily of beta blockade. Via reducing heart rate and prolonging diastole, beta blockers are able to reduce compression and improve flow. Calcium channel blockers and nitrates may also provide some relief if vasospasm is a concern. For symptoms refractory to medical management, percutaneous coronary intervention with stenting or surgery may be offered. Coronary stenting with drug-eluting stents has demonstrated favorable midterm results, but long-term data are pending. Surgical options for failure of medical management include supra-arterial myotomy or coronary artery bypass grafting. Supra-arterial myotomy has yielded good long-term results, but care must be taken to avoid entry into the right ventricle, which may be vulnerable during unroofing. As an alternative to myotomy, coronary artery bypass distal to the muscle bridge may also be considered for patients with atherosclerotic disease proximal to the bridge and in patients with a thick muscle bridge, because this may increase the risk of inadvertent coronary injury or ventricular entry.