Collateral Circulation via a Rare, Anomalously Arising Right Ventricular Branch

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J INVASIVE CARDIOL 2008;20:E136-E137

Coronary collateral vessels are able to supply blood to a myocardial territory vascularized by severely stenosed or occluded epicardial arteries. They may contribute significantly to the limitation of ischemia and infarct size.^1,2 Improvement in left ventricular function^3,4 and prevention of left ventricular aneurysm formation⁵ also has been attributed to the presence of collateral vessels.
Variations in coronary anatomy are not uncommon. They are usually benign, but can be a cause of confusion to the angiographer and have no clinical significance in most situations. In this report, we present an unusual case of a chronically occluded proximal right coronary artery (RCA) with a separate anomalous right ventricular branch arising directly from the aortic root and serving as a large collateral vessel to the area beyond the occlusion. To our knowledge, this is the first report of this type of anatomic variation.

Case Report. A 68-year-old male with dyslipidemia and peripheral vascular disease was admitted with increasing shortness of breath. He was found to have moderate-to-severe aortic regurgitation and minimal aortic stenosis on echocardiography and underwent a cardiac catheterization study. Aortography revealed a grade 3 over 4 aortic regurgitation. Coronary arteriograms revealed severe triple-vessel coronary artery disease including total occlusion of the proximal RCA (Figure 1). The mid and the distal segments of the RCA were separately opacified via a right ventricular branch directly arising from the aorta and serving as a large collateral to a mid-RV branch of the RCA (Figure 2).

Discussion. Congenital coronary artery anomalies are seen in 0.6–1.3% of adults undergoing coronary arteriography.⁶ Though congenital anomalies of coronary artery origins have been implicated in chest pain, dyspnea, syncope, myocardial infarction, ventricular fibrillation, cardiomyopathy and sudden death, most anomalies are discovered incidentally during coronary arteriography.⁷ Aside from the RCA, the other vessels originating separately from the right aortic sinus include the conus branch,^6,7 the ectopic left circumflex artery,^6,7 the ectopic left main artery,8 the ectopic left anterior descending artery⁹ or the second RCA (dual RCA system).^10,11
To our knowledge, a separate right ventricular branch arising directly from the right aortic sinus has not been described previously in the literature. Harikrishnan et al detected 34 patients with coronary anomalies after evaluating 7,400 conventional angiographic studies¹² (0.46%). Among all right coronary artery anomalies, the most common type was the RCA originating from the left sinus of Valsalva followed by anomalous origin of the RCA from the posterior sinus of Valsalva. A double RCA was seen in only 1 patient, and no patients had a right ventricular branch arising directly from the right aortic sinus. Clear distinction between a double RCA and a separate origin of the right ventricular branch may be difficult. Recently, a double RCA was identified using multidetector computerized tomography.¹
The findings in our patient are unusual, not only because it was a rare anomaly involving the right ventricular branch, but also because this branch served as a collateral source to the occluded RCA. Detection of collateral channels is important when considering surgical or percutaneous revascularization procedures. One should think of the possibility of an anomalous source of such collateral vessels.

References

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