Anomalous Left Circumflex Artery From the Right Coronary Cusp
Anomalous Left Circumflex Artery From the Right Coronary Cusp
Large case series identifying the frequency of anomalous circumflex arteries in a population have suggested that perhaps due to the unique retro-aortic position of this vessel, it is more prone to atherosclerosis. In this paper, we compiled one of the largest cohorts with this anomaly and sought to determine if indeed the ALCx had a higher incidence of single-vessel CAD or whether CAD in the ALCx simply marked a population with multivessel disease. In this selective, mainly male veteran population with a high number of cardiac risk factors, it was found that atherosclerosis of the ALCx is common. However, in contrast to other studies, we found in the majority of our patients that any atherosclerosis was actually present in the other two coronaries as well. In fact, only a single patient had isolated obstructive disease of the ALCx that happened also to be a CTO. In that isolated case, CAD was also concomitantly present in the other vessels.
Similar to large studies done on the ALCx, the majority of ALCx in this cohort originated from a common/adjacent ostium in the right coronary sinus and took a posterior course to the great vessels before supplying the posterolateral surface of the left ventricle. It is this retro-aortic posterior course that has been proposed to be a contributing factor in the development of atherosclerosis in the ALCx. The hypothesis behind this is that there is increased sheer stress at the ostium and proximal aspect of this vessel given its unique ostial angulation and retro-aortic course. When analyzed by location of disease, the majority of obstructive CAD involving the ALCx appears to be confined to the proximal to mid body of the vessel versus ostial, suggesting that the proposed increased sheer forces are not a factor. Our study suggests that this common anomalous vessel does not have a higher propensity to develop atherosclerosis. What is evident is that these vessels are generally small, with a mean vessel diameter of only 2.20 mm. We only found 3 patients with a vessel size greater than 2.75 mm.
PCI was successfully performed in 5 cases with obstructive disease involving the ALCx, and these stents were small, consistent with the small size of the vessel. The outcome at a mean of 18 months following cardiac catheterization for the 13 patients undergoing medical management and the 5 patients undergoing PCI showed low rates of MACE endpoints with similar survival rates in terms of deaths attributed to cardiac events, and both groups were free of MACEs.
This study is limited by its singlecenter, retrospective design. It includes only patients with a high pretest probability of diffuse CAD, which may differ from the general population. Our patients are older and systemically have a large atherosclerotic burden and all of our patients were referred for coronary catheterization for either symptoms of angina or had presented with ACS. Hence, a selection bias is present and this could explain why we found more diffuse CAD in our cohort. Therefore, it would be helpful to know more about asymptomatic patients who have ALCx and whether there is increasing incidence of atherosclerosis compared to the normal variant.
Discussion
Large case series identifying the frequency of anomalous circumflex arteries in a population have suggested that perhaps due to the unique retro-aortic position of this vessel, it is more prone to atherosclerosis. In this paper, we compiled one of the largest cohorts with this anomaly and sought to determine if indeed the ALCx had a higher incidence of single-vessel CAD or whether CAD in the ALCx simply marked a population with multivessel disease. In this selective, mainly male veteran population with a high number of cardiac risk factors, it was found that atherosclerosis of the ALCx is common. However, in contrast to other studies, we found in the majority of our patients that any atherosclerosis was actually present in the other two coronaries as well. In fact, only a single patient had isolated obstructive disease of the ALCx that happened also to be a CTO. In that isolated case, CAD was also concomitantly present in the other vessels.
Similar to large studies done on the ALCx, the majority of ALCx in this cohort originated from a common/adjacent ostium in the right coronary sinus and took a posterior course to the great vessels before supplying the posterolateral surface of the left ventricle. It is this retro-aortic posterior course that has been proposed to be a contributing factor in the development of atherosclerosis in the ALCx. The hypothesis behind this is that there is increased sheer stress at the ostium and proximal aspect of this vessel given its unique ostial angulation and retro-aortic course. When analyzed by location of disease, the majority of obstructive CAD involving the ALCx appears to be confined to the proximal to mid body of the vessel versus ostial, suggesting that the proposed increased sheer forces are not a factor. Our study suggests that this common anomalous vessel does not have a higher propensity to develop atherosclerosis. What is evident is that these vessels are generally small, with a mean vessel diameter of only 2.20 mm. We only found 3 patients with a vessel size greater than 2.75 mm.
PCI was successfully performed in 5 cases with obstructive disease involving the ALCx, and these stents were small, consistent with the small size of the vessel. The outcome at a mean of 18 months following cardiac catheterization for the 13 patients undergoing medical management and the 5 patients undergoing PCI showed low rates of MACE endpoints with similar survival rates in terms of deaths attributed to cardiac events, and both groups were free of MACEs.
Study Limitations.
This study is limited by its singlecenter, retrospective design. It includes only patients with a high pretest probability of diffuse CAD, which may differ from the general population. Our patients are older and systemically have a large atherosclerotic burden and all of our patients were referred for coronary catheterization for either symptoms of angina or had presented with ACS. Hence, a selection bias is present and this could explain why we found more diffuse CAD in our cohort. Therefore, it would be helpful to know more about asymptomatic patients who have ALCx and whether there is increasing incidence of atherosclerosis compared to the normal variant.