Congenital Coronary Anomalies

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CHAPTER 33 Congenital Coronary Anomalies

Anomalies of the coronary arteries are uncommon, but sometimes can be clinically significant. Most coronary artery anomalies are benign and clinically insignificant; however, some may lead to compromise to coronary flow causing ischemia, heart failure, and death. Clinical presentation depends on the specific anomaly.

Noninvasive imaging has emerged as the preferred way to image coronary anomalies. Electron-beam CT and MR angiography are valuable for the diagnosis of anomalous coronary arteries. More recently, multidetector CT also has been shown to be very useful in the detection and characterization of anomalous coronary arteries. This chapter reviews the appearance of the most commonly encountered coronary anomalies on noninvasive imaging using CT and MRI.

DEFINITION

Anomalous coronary arteries can be grouped into three general categories. Angelini and colleagues1 have written one of the most complete works on this subject, and this text can serve as an excellent reference for additional study. Anomalies generally can be divided into three general classifications: (1) anomalies of origin and course (ectopic ostium within proper sinus, ostium outside normal sinus, and absent vessel); (2) anomalies of intrinsic coronary arterial anatomy (congenital stenosis of ostium, congenital aneurysms, and myocardial bridging); and (3) anomalies of coronary termination (fistulas) (Table 33-1).

TABLE 33-1 Classification of Coronary Anomalies

Anomalies of origin and course

Anomalies of Intrinsic Coronary Arterial Anatomy Anomalies of Termination Coronary artery fistula

One of the most commonly encountered anomalies of origin and course is that of a retroaortic circumflex coronary artery that arises from the right sinus of Valsalva. This has an anomalous ectopic ostium (right sinus of Valsalva) and course (retroaortic), but terminates in the usual location (left atrioventricular groove). Myocardial bridging is a commonly encountered anomaly of intrinsic coronary anatomy. Although the artery, which is almost always the left anterior descending (LAD) artery, arises from the usual sinus and travels in the usual course (anterior interventricular groove), but it takes an unusual temporary dip into the myocardium of the anterior wall before re-emerging in the epicardial fat.

Finally, anomalies of coronary termination include coronary artery fistulas. These are coronary arteries that arise from the proper sinus, but eventually terminate in an unusual location. The coronary artery blood flow does not supply the myocardium, but may flow into the pulmonary artery, coronary sinus, cardiac chamber, or superior vena cava. Small fistulas are incidental findings; however, large fistulas may have serious hemodynamic and clinical consequences.

IMAGING TECHNIQUE AND FINDINGS

DIFFERENTIAL DIAGNOSIS

Anomalies of Origin and Course

Anomalous Origin of a Coronary Artery from the Opposite Sinus of Valsalva

One of the most commonly encountered potentially serious anomalies involves the anomalous origination of a coronary artery from the opposite sinus of Valsalva. Either the right coronary artery (RCA) or the left coronary artery (LCA) can arise from the opposite sinus, and then traverse across the heart to resume a normal position. Alternatively, a single branch of the LCA, the LAD artery, or the left circumflex artery can arise from the opposite sinus, whereas the remainder of the LCA may arise from the correct sinus.

There are several potential courses for an anomalous LCA arising from the right sinus of Valsalva or the RCA (Fig. 33-1). Diagnosis of the exact course is important because it determines if intervention is necessary. There are four possible pathways for the anomalous LCA: (1) between the aortic root and the pulmonary artery (interarterial course), (2) a transseptal (intraseptal or subpulmonic) course, (3) anterior to the right ventricular outflow tract (anterior or prepulmonic course), and (4) posterior to the aortic root (retroaortic course). Although the anterior, posterior, and septal (subpulmonic) courses are benign, an interarterial course carries a high risk for sudden cardiac death.29,30

Axial reconstructions from a multidetector CT coronary angiogram can depict the anatomic course. The exact position and course of the anomalous artery can be viewed in relation to the aortic root and pulmonary artery (Fig. 33-2). The LCA arises from the right sinus of Valsalva or directly from the RCA in 0.10% of patients, and an interarterial course is present in approximately 75% of these patients.31

Three-dimensional volume rendered multidetector CT images of the coronary arteries and aortic root can also be helpful in depicting the course and anatomic relationships. An anomalous coronary artery originating from the opposite sinus of Valsalva can cause syncope, myocardial infarction, and sudden death in the absence of critical, fixed stenosis. Patients with an anomalous LCA that takes an interarterial course have a high risk for sudden cardiac death because of the acute angle of the ostium, the stretch of the intramural segment of the anomalous artery, or the compression between the commissures of the right and left coronary cusps.1,31 This anomalous LCA may narrow the origin or proximal aspect of the vessel and limit flow. An anomalous interarterial coronary artery is frequently an underlying cause for sudden death in young athletes. Often, MRI can also show an anomalous coronary artery with an interarterial course (Fig. 33-3).