The incidence of primary congenital coronary anomalies varies from 0.95–2% in the adult population undergoing coronary angiography (CAG).^1–4 The majority of these are reported to be anomalies of origin or distribution, with separate ostia of the left anterior descending artery and left circumflex artery being the most common. Coronary artery anomalies are divided into those that cause and those that do not cause myocardial ischemia.^5,6 We describe a rare benign anomaly, a double right coronary artery (RCA) presenting as acute inferior wall myocardial infarction due to thrombotic occlusion of one of the two RCAs that was managed with primary percutaneous coronary intervention. This is the first case in the literature of this rare anomaly presenting with acute myocardial infarction.

Case Report. A 53-year-old male was hospitalized in our emergency department with complaints of severe chest pain suggestive of acute coronary syndrome of 12 hours’ duration. He was a chronic smoker and had hypertension for the past 10 years. The blood pressure and pulse rates were 130/80 mmHg and 86 beats per minute, respectively. The physical examination was completely normal. Electrocardiography showed ST-elevation in leads II, III and aVF, with ST-elevation III > II and 0.5–1 mm ST-segment depression in leads V 4–6. Cardiac enzymes and troponin I were found to be increased. The patient’s chest X-ray was normal, while transthoracic echocardiography revealed regional wall motion abnormality in the RCA territory with an ejection fraction of 50%. There was no mitral regurgitation. With a diagnosis of acute inferior wall myocardial infarction (MI), he was taken for primary percutaneous coronary intervention (PCI). Coronary angiography revealed a normal left coronary artery systemwith a nondominant left circumflex artery. The RCA was selectively cannulated with a 6 Fr Judkins right diagnostic catheter. Injection in the right coronary orifice resulted in selective opacification of the RCA with near-total occlusion of one of its early branches (Figure 1). Left ventricular angiography showed posterobasal segment hypokinesia with a normal left ventricular ejection fraction. In view of the electrocardiographic changes of acute inferior wall MI suggestive of RCA territory involvement and echocardiographic evidence of regional wall motion abnormality in the same arterial territory, significant vascular territory involvement had to explain these findings. Hence, a possibility of total occlusion of either a high takeoff of a large right ventricular branch of the RCA or one of the two RCAs of a double right coronary artery was considered. RCA injection in the right cranial oblique view (RAO 60^º, cranial 20^º) raised suspicion of a double RCA because of the unusual course of the occluded branch in this view (Figure 2). The patient was taken for coronary revascularization after a bolus dose followed by infusion of abciximab. The RCA was engaged with a right Judkins 6 Fr guiding catheter and the lesion in the infarct-related artery was crossed with a 0.014 inch Cross- IT intermediate guidewire (Guidant Corp., Santa Clara, California). A lesion in the artery was predilated with a Voyager^™ (Abbott Vascular, Santa Clara, California) 2.0 x 12 mm balloon at 10 atm (Figure 3). Post balloon dilatation injection in the right coronary orifice resulted in selective opacification of two different RCAs from a common main trunk. The superior RCA after the origin of the conus artery and two right ventricular (RV) branches descended beyond the acute margin of the heart and terminated as the posterior descending coronary artery (PDA) (Figure 4). The second, more inferior RCA after giving rise to one small RV branch ended at the crux, giving rise to the PDA and a small posterolateral branch (PLB) (Figure 4). Both RCAs coursed down the right atrioventricular groove, which was confirmed in the RAO cranial (Figure 5A) and lateral views (Figure 5B). The inferior RCA showed a tubular eccentric maximum 90% stenosis in the proximal segment (Figure 5). A Driver 3.0 x 18 mm stent was successfully deployed across the lesion at 10 atm for 30 seconds (Figure 6). The post-interventional period was uneventful and the patient was discharged the following day.

Discussion. A double RCA is an extremely rare coronary artery variation, with only a few cases being reported previously.^7–9 Origin from separate ostia in the right coronary sinus has also been described.¹¹ The largest series on coronary anomalies, which analyzed 127,000 odd angiograms, did not describe this anomaly.¹ In another study, only 1 case was found in a series of 7,400 patients.² The first report in the literature was by Barthe et al⁷ who defined this anomaly after injecting the contrast into the right coronary orifice, which disclosed selective opacification of two different right coronary arteries arising from a common ostium, coursing down the right atrioventricular groove. After the origin of a conus artery and a ventricular branch, the most anterior RCA descended toward the acute margin of the heart and terminated in a small PDA. The second RCA ended up with a small posterior descending and posterolateral branches. At surgery for aortic stenosis, the presence of a single right coronary ostium was confirmed. The correct diagnosis of double RCA is not easily made based on conventional coronary angiography because it is difficult to differentiate this variation from a high takeoff of a large right ventricular branch.⁹ Barthe et al showed that careful examination of the left ventriculogram might disclose two retro-aortic points, suggesting the presence of a double RCA.⁷ In addition, withdrawing the catheter during cine acquisition just before the end of coronary imaging might also be helpful for detecting these kinds of anomalies.¹² Nair et al have suggested in conventional coronary angiography that a dominant RCA should cross the crux, while a right ventricular branch will not.¹⁰ Orthogonal views can resolve whether the two vessels really cross the crux and qualify to be considered the RCA. Recently, Kunimasa et al demonstrated the usefulness of multidetector-row computed tomography to distinguish this variation from a right ventricular branch because of its ability to allow 3-dimensional comprehension of the coronary arterial system.¹³

This extremely unusual abnormality is generally considered benign, however, it has been reported to be associated with atherosclerosis and life-threatening arrhythmia.^12,14 Ours is the first case in the literature to describe presentation with acute inferior wall MI due to involvement of a double RCA and its successful management by PCI. The initial dilemma regarding differentiation from high takeoff of the right ventricular branch was resolved by utilizing the orthogonal views as suggested by Nair et al.¹⁰ The branching pattern and distribution of the RCA in the above-described case is very similar to that reported in the literature.^7,8
In conclusion, a double RCA does not necessarily signify a rare benign entity. It addition, alternative diagnostic possibilities like high takeoff of the right ventricular branch must be considered before making a diagnosis of a double RCA.