Pictorial essay: Coronary artery variants and anomalies

Abstract CT coronary angiography has helped radiologists understand the variations and anomalies of the anatomy of the coronary arteries and, thus, to alert the cardiologist whenever such an anomaly is present. This can be of immense help to the clinician planning interventional procedures such as stenting, balloon dilatation, or graft surgery, particularly when there are secondary changes of calcification, plaque formation and stenosis.

We present an account and atlas of coronary artery variants and anomalies culled from a database of more than 15000 CT coronary angiographies (CTCA) carried out on a 16-slice Siemens scanner (Somatom 16, Erlangen, Germany) from November 2004 till March 2008 at our institute. Except for a few patients with a prior history of angina, established myocardial infarction, or intervention in the form of coronary stenting or bypass surgery, all the rest underwent the investigation as part of a health check-up package that off ered CTCA as an additional investigation.
Over the past few years, several workers have described coronary artery variants and anomalies as identiÞ ed on catheter angiographies. Angelino et al, [1] described various minor anomalies in the branching pattern of coronary arteries and in the location of the cusps and reported an incidence of anomalies in about 1% of the general population. From our own experience with CTCAs, most of which were performed on asymptomatic people rather than on symptomatic subjects, we too are of the opinion that the incidence of coronary variants and anomalies is under 1% in the general population.
Aft er the introduction and establishment of CTCA as an alternative to catheter angiography, a few articles have been published on the detection of such variations and anomalies. Recently, Cademartiri et al, [2] have reported 100 (18%) anomalies from 543 consecutive CTCAs done using a 64-slice CT scanner. According to him, catheter angiography cannot detect ectopic openings of coronary arteries since it is only a two-dimensional study. Oft en, a diagnosis of an anomaly is made when angiography fails to show the normal anatomy. On CTCA, 14 (16.5%) coronary anomalies were detected among the 85 patients who did not have signiÞ cant coronary artery disease in their study, while 86 coronary anomalies (18.8%) were detected among the 458 patients with signiÞ cant coronary artery disease. These anomalies included anatomical variations as well as aneurysms.
Variations in coronary anatomy are oft en seen in association with structural forms of congenital heart disease like Fallot's tetralogy, transposition of the great vessels, Taussig-Bing heart (double-outlet right ventricle), or common arterial trunk. [3] Importantly, coronary artery anomalies are a cause of sudden death in young athletes even in the absence of additional heart abnormalities. [4] Prior knowledge of such variants and anomalies is necessary for planning various interventional procedures.
It is estimated that nearly 5.6% of the total American population could have some kind of coronary anomaly and up to 15% of sudden deaths in young athletes are probably related to these anomalies. [4] The greatest advantage of CTCA is the high spatial and temporal resolution it provides, so that ectopic origins of anomalous arteries and their paths can be conÞ rmed with greater ease and conÞ dence.

Variants and anomalies
In the literature there are many terms that have been used to describe variations in coronary anatomy, e.g., abnormal, ectopic, atypical, anomalous, aberrant, accessory, etc.
A) Variants refer to simple variations in the structural anatomy.

Type of dominance
1. The posterior descending artery (PDA) may be supplied by the right coronary artery (RCA); this is referred to as RCA dominance. 2. The PDA may be supplied by the circumß ex (CX); this is referred to as left coronary dominance.  Figure 3} or separate origins of the LAD and the CX from the left aortic cusp [ Figure 4].

Myocardial bridging of LAD
It can be a normal variant. However, tunnelled LAD is reported in approximately 5% of field deaths among athletes [5] [ Figure 5].
B) Anomalies are those variations related to the origin and course of the coronary arteries; they may be benign or dangerous (the so-called malignant anomaly). The latt er predispose a person to early vascular compromise, ischemia, and fatal infarction. These are far less common (less than 1%). [5]