Coronary artery anomalies--current clinical issues: definitions, classification, incidence, clinical relevance, and treatment guidelines

Abstract

The study of coronary artery anomalies would benefit from the clarification of various fundamental issues, including the definitions, classification, incidence, pathophysiologic mechanisms, and clinical relevance of each anomaly. The greatest challenge is to identify the abnormality and determine its clinical relevance so that appropriate treatment can be instituted. Currently, the coronary anatomy is essentially defined by the features of the (conductive) epicardial coronary tree and its dependent territory. Therefore, one must consider all the possible and observed variations in anatomic features that are used to describe the coronary arteries. We propose that the left anterior descending, circumflex, and right coronary arteries be considered the essential elementary units of coronary anatomy. We also suggest that the coronary arteries be defined not by their origin or proximal course, but by their intermediate and distal segments or dependent microvascular bed. A strict classification system is necessary before meaningful data can be gathered about the incidence of coronary anomalies. With respect to clinical relevance, the greatest challenge is presented by anomalies that only occasionally cause critically severe clinical events and are otherwise compatible with a normal life. In such cases, it is not known whether the specific features of a given anomaly cause adverse clinical consequences, or whether additional episodic factors are required. To correlate subclassifiable anatomic and functional features with clinical events and prognoses, a large, multicenter database, relying on prospective, coordinated protocols, is urgently needed. In the absence of established official guidelines, we present practical protocols for diagnosing and treating coronary anomalies.

Fig. 1 The most common coronary artery anatomic patterns in 44 cases of double-outlet right ventricle. A) Normal coronary origination as seen in all 17 cases (39%) with normally related great vessels. B) Coronary artery pattern seen in 11 (73%) of the 15 patients with transposition of the great arteries (34% of the 44 cases). C) Coronary artery pattern seen in 4 (33%) of the 12 cases with side-by-side arrangement of the great arteries. Five other coronary patterns were less frequently observed. (From Angelini P, editor. Coronary artery anomalies: a comprehensive approach. Philadelphia: Lippincott Williams & Wilkins; 1999. p. 85. [Modified from Gordillo L, Faye-Petersen O, de la Cruz MV, Soto B. Coronary arterial patterns in double-outlet right ventricle. Am J Cardiol 1993;71:1108–10.] Reprinted with permission from Lippincott Williams & Wilkins.)

Fig. 2 Histologic longitudinal cross-section at the right ventricular outflow tract and the aortic root (closest point) obtained at necropsy from a 17-year-old basketball player who died suddenly during a game. The patient had reported no symptoms and had undergone several medical examinations that were negative for cardiovascular disease. Note that the right coronary artery (RCA) is intussuscepted into the aortic wall, which has a thickness that is 50% of normal inside the RCA, and 25% of normal outside the RCA. Also note the wide space between the aorta and the pulmonary artery (PA) at the closest site, which makes scissors-like compression of the RCA unlikely. IVS = interventricular septum (Photo courtesy of Dwayne A. Wolf, MD, PhD; Office of the Medical Examiner of Harris County, Texas.)

Fig. 3 Angiographic appearance of an ectopic right coronary artery (RCA) originating at the left sinus of Valsalva, next to the left coronary artery (left anterior oblique projection).

Fig. 4 A) Intravascular ultrasonographic (IVUS) view of the RCA ostium. The wall of the aorta (Ao) contains the RCA, and the inner wall of the aorta is interrupted (at the ostium), showing the tangential origination of the ectopic vessel. B) Proximal RCA, at the level of the intramural segment, as shown by IVUS during systole. The aortic lumen is on the right and the pulmonary artery (PA) on the left. The aortic wall has a total thickness of about 4.3 mm, including an inner layer of <0.02 mm and an outer layer of 1.3 mm. In this intramural segment, no intimal thickening is present. However, distal to this intussusception, the intima is quite thick and is accompanied by diffuse calcification. C) End-diastolic appearance of the RCA at the same site as shown in view B, which was during systole. In this IVUS image, the transverse diameter is wider and the luminal area rounder than in view B, proving that lateral compression is worse during systole. The luminal area was indeed 30% and 50% narrower during diastole and systole, respectively, in the intramural segment than in the distal reference vessel. D) Intravenous ultrasonographic image at the RCA, just distal to the intramural segment. Atherosclerotic intimal thickening and calcifications are clearly visible: note that they are absent at the intramural segment (see A–C). Comm = commissure; RCA = right coronary artery

Fig. 5 Proposed diagnostic protocol for adult patients who are at risk for coronary artery anomalies. − = negative test result; + = positive test result; CXR = chest x-ray; echo = echocardiogram; EKG = electrocardiogram; F/U = follow-up; IVUS = intravascular ultrasound; N = no; PTCA = percutaneous transluminal coronary angioplasty; Rx = treatment; TMT = treadmill test; TTE = transthoracic echocardiogram; Y = yes