Abstract Background The prognosis of patients in whom the right coronary artery (RCA) arises from the left coronary sinus (LCS) is unequal. An initial intramural course of the coronary artery within the aortic media is considered to cause myocardial ischemia in cases of coronary anomalies. Methods Clinicopathological findings in five autopsy cases where the RCA arose from the LCS with an intramural course were examined. Comparison between sudden cardiac death and noncardiac death was also performed. Results Two of five cases were sudden cardiac death, and the other three cases were noncardiac death. In one case of sudden death, the person collapsed during light exercise, and in the other case, the person was under the effect of methamphetamine. Both of the cases of sudden death showed an RCA-dominant pattern in distribution of the coronary artery, atherosclerotic narrowing of the RCA, and acute ischemic necrosis in the posterior basilar ventricular septum around the atrioventricular conduction system, which is considered to be the territory of the RCA. Conclusions An intramural course within the aortic media may be an accelerating factor of decreased blood flow in cases with an origin of the RCA arising from the LCS because of compression from the aortic lumen. However, this finding may not be an independent predictor of pathological ischemia. Additional factors that diminish blood flow in the intramural segment may be required to cause significant myocardial ischemia. Additionally, inciting factors, which can increase blood pressure, may also play a role in causing symptomatic myocardial ischemia by initiating mechanical compression from the aorta to the intramural segment of the RCA.
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