Case of a Missing Right Coronary Artery Origin

Interventional cardiologists are able to read X-ray angiography lumingrams because they have an intimate knowledge of the coronary anatomy. However, this vessel template does not apply to all patients, and when arteries are out of place it can be very confusing to interpret. 

This was the rare case when a 44-year-old male presented with sudden chest pain and inferior ST-segment elevations and underwent angiography at Northside Hospital and Tampa Bay Heart Institute. Coronary angiography revealed an anomalous origin of the right coronary artery (RCA) as a branch off the left anterior descending (LAD) artery distal to the first diagonal branch.

Right coronary artery anomalies appear more common than left coronary aberrancies.[1] Split RCA, ectopic RCA — either off the right or left cusp — account for the majority of anomalous coronary artery origins.[1]  Ischemia is generally absent in split right coronary artery ostium, ectopic right coronary artery from the left coronary sinus and right coronary artery aberrantly from the right coronary sinus.[1]  Anomalous origin of a right coronary artery from the left coronary sinus that courses between the aorta and main pulmonary artery was reported for the first time by White and Edwards in 1948.[2]  The incidence of this anomaly is less than 1 percent so it is considered an infrequent coronary anomaly.[3] Origin of the RCA arising aberrantly from the LAD distal to the first diagonal branch is rarely described in literature. Saravanan et al described one of the first reported cases in 2006 of the right coronary artery off the mid-left anterior descending artery.[4]

In this article, we report a very rare case of a patient with the origin of a right coronary artery arising aberrantly from the left anterior descending coronary artery distal to the first diagonal branch in the setting of inferior ST-segment elevations.

Case report

     The patient has myotonic muscular dystrophy (MMD), systemic hypertension, a family history of premature coronary artery disease and cardiac conduction defects presented with acute crushing anterior sub-sternal chest pain of 25-minutes duration. ECG revealed inferior Q-waves and 1-2 mm concave ST-segment elevations in the emergency room.  The patient had a left heart catheterization at another facility two years prior without reported coronary intervention. Coronary angiography revealed the anomalous origin of the right coronary artery from the LAD, which gave rise to a posterior descending branch that supplied the inferior apex of the heart. All coronary segments were visualized with moderate stenosis in LAD distal to the origin of anomalous right coronary artery. Fractional flow reserve (FFR) determined the lesion to be hemodynamically insignificant with a ratio of 0.91. Left ventricular systolic function was grossly normal and the only abnormality detected was the aberrant origin of right coronary artery.

Cardiac computed tomography (CCT) more clearly showed the RCA anomalously LAD origin and its anterior course around the main pulmonary trunk before supplying the usually right coronary artery vascular distribution in a dominant course. The RCA did not course between the main pulmonary artery and aortic root. 

The prevalence of an anomalous origin of a RCA from the left coronary sinus of Valsalva, by itself, is less than 1 percent.[2,3,5] 

Clinical symptoms and course of patients with aberrant origin and abnormal course of RCA may be benign. Some patients present with dizziness, syncope, angina, myocardial infarction and even sudden cardiac death in up to 30 percent, including young athletes.[5,6,7]  Roberts et al described justifying the misnomer of “malignant origin” of the right coronary artery depending on the anterior or posterior course of the vessel.[8] Often it is not easy to explain the possible mechanisms of ischemia presented by these patients without overt coronary stenosis. Clinical explanations include: compression of the coronary artery between the great vessels, particularly during exercise, or acute angle take-off of the coronary artery as it emerges from the aorta.[5] Generally, this is seen with an interarterial course between the aortic root and main pulmonary artery, which was not the case with our patient.[9-11]

In our patient, coronary ischemia was not documented despite having moderate range LAD disease. Previous ECG’s later confirmed inferior Q-waves and ST-segment changes likely representing the abnormal axis or possible from the muscular dystrophy. MMD is known to have defects in cardiac conduction, including high-degree atrioventricular, bi- or trifascicular block.[12,13]  An annual screening ECG is recommended, and most are reported to require permanent pacing.[12,13]  There is limited data on anomalous coronary artery anatomy associated with MMD.

We suspect the anomalous RCA was an incidental finding and unlikely related to the acute symptoms referred by the patient. Medical treatment was initiated with beta-blockers, aspirin, HMG-CoA reductase inhibitors and an angiotensin-converting enzyme inhibitor. He was advised of risks and will be followed by ambulatory consultation.  

Editor’s Note: The authors Thomas Waggoner, D.O., Robert Sanchez, M.D., Peter Wassmer, M.D., Andrew Rosenthal, M.D.,are from Northside Hospital and Tampa Bay Heart Institute, departments of graduate medical education and cardiology in St. Petersburg, Fla.

References

1. “Braunwald’s Heart Disease.” 9th ed. Volume 1. Libby, Bonow, Mann. Saunders. 2011.

2. White N, Edwards J. “Anomalies of the coronary arteries. Report of four cases.” Arch Pathol 1948; 45: 766–771. 

3. Angelini P. “Coronary Artery Anomalies. Clinical Issues. Definitions, Classification, Incidence, Clinical Relevance and Treatment Guidelines.” Tex Heart Inst J 2002; 29: 271-278. 

4. Saravanan P, Mennim P, Hancock H. “Anomalous origin of right coronary artery from the mid left anterior descending coronary artery.” Heart 2006; 92 (9): 1212.

5. Angelini P. “Coronary artery anomalies: an entity in search of an identity.” Circulation 2007; 115: 1296-1305. 

 6. Ichikawa S, Komatsu S, Hirayama A, Kodama K, Saito S. “Multislice computed tomographic findings of the anomalous origins of the right coronary artery: evaluation of possible causes of myocardial ischemia.” Int J Cardiovasc Imaging. 2007; 23: 353–360.