R-IIIC type: non-simple single coronary artery.

We read with great interest a report by Gallo et al. [1] on a very rare coronary artery anatomy. In a classification of single coronary artery (SCA) by Lipton et al. [2] with modifications by Yamanaka and Hobbs [3], this case refers to the R-IIIC type of SCA. Indeed, there is little discrepancy between terminology and anatomy in this type of SCA, which is very apparent in the present case. According to the foregoing classification, the R-IIIC type of SCA is an anomaly where the left anterior descending artery (LAD) and left circumflex artery (LCx) arise separately from the proximal part of the normal right coronary artery (RCA). Then, LCx passes the great vessels posteriorly and LAD crosses anteriorly the infundibulum of the right ventricle to reach their usual locations [2, 3]. This LAD supplies only the middle and distal portions of the anterior interventricular sulcus (AIVS), and the proximal portion of the AIVS receives blood from the ‘LCx’ (it is clearly seen in Fig. 2A from [1]). Thus, AIVS has two sources of blood supply and this anatomy refers to Type IV dual LAD [4]. In more detail, we have discussed this anatomy in a recent similar case by Saxena et al. [5, 6]. Hence, the R-IIIC type of SCA is a combination of two anomalies: Type IV dual LAD and left main stem (LM) originating from the RCA, and the correct description of coronary arteries in this type should apply the terms long LAD, short LAD and LM. Correct diagnosis of dual LAD in SCA may be important in planning the strategy of revascularization in the case of atherosclerotic lesions in the LM or short LAD.