Acute STEMI in the setting of a single coronary artery anomaly

Abstract

We report a case of a patient admitted with an acute ST elevation myocardial infarction following occlusion of his right coronary artery, successfully treated with thrombectomy and percutaneous coronary intervention (PCI). Coronary angiography and multislice CT revealed a single right coronary artery with two anomalous branches (constituting the left coronary system); one branch passed between the pulmonary trunk and the aorta before dividing into three separate branches, while the other anomalous branch passed anterior to the pulmonary trunk, consistent with a Yamanaka R-IIIC classification. The course of this Yamanaka R-IIIC subtype is unusual as both anomalous branches combine to form a dual origin left anterior descending artery. The course of these anomalous branches places the patient at an increased risk of future myocardial ischaemia, infarction and sudden cardiac death. As symptoms typically develop on exertion, this cohort may benefit from exercise myocardial perfusion imaging to identify high-risk patients.

Background

With a prevalence of 0.024–0.066% in patients undergoing coronary angiography, a single coronary artery (SCA) is considered an extremely rare coronary anomaly. The course of the Yamanaka R-IIIC subtype SCA in our case is unusual and has not previously been described, as the anomalous branch passing anterior to the pulmonary trunk unites with a branch of the anomalous artery that passes between the aorta and the pulmonary artery, to form a dual origin left anterior descending (LAD) artery. The case will be interesting and informative from a management perspective, highlighting the management of a ST elevation myocardial infarction (STEMI) in this cohort of patients. It will raise awareness among physicians that the course of these anomalous branches places the patient at an increased risk of future myocardial ischaemia, infarction and sudden cardiac death. It also highlights the follow-up course after the initial presentation and the management options in this particular patient.

Case presentation

A 59-year-old man with a history of smoking (20 cigarettes/day for 40 years) and elevated body mass index (BMI) developed severe persistent central chest pain at rest. He was brought by ambulance directly to the catheterisation laboratory for primary percutaneous coronary intervention (PCI). En route to hospital he was given aspirin 300 mg and clopidogrel 600 mg orally by the ambulance crew.

Investigations

ECG was performed on arrival and showed inferior STEMI with reciprocal changes in the anterolateral leads. Coronary angiography was performed to identify the presence and location of the blockage. It showed a single right coronary artery (RCA) with two anomalous arteries originating from its proximal third. There was extensive thrombotic occlusion of the RCA from the mid third level with thrombolysis in myocardial infarction 0 flow distally (figure 1; video 1). Left ventriculography was performed to assess contractile function of the myocardium, which showed inferior akinesia and an ejection fraction of 45% (video 2).

Figure 1.

Coronary angiography showing occluded right coronary artery (RCA) before primary percutaneous coronary intervention. Note the anomalous left coronary artery (LCA) originating from the proximal part of RCA.

Video 1.

Download video file ^{(3.6MB, mp4)}

DOI: 10.1136/bcr-2015-210002.video01

Coronary angiogram showing occluded right coronary artery before percutaneous coronary intervention.

Video 2.

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DOI: 10.1136/bcr-2015-210002.video02

Coronary angiogram showing occluded right coronary artery after percutaneous coronary intervention.

Differential diagnosis

The patient’s ECG findings of inferior ST elevation with reciprocal changes in the anterolateral leads, combined with his risk factors of heavy smoking and elevated BMI, led to a working diagnosis of STEMI.

Differential diagnosis included:

• Acute pericarditis

• Left ventricular hypertrophy

• Hyperkalemia

• Early repolarisation

Treatment

The RCA obstruction was recanalised with balloon angioplasty followed by thrombus aspiration and deployment of two overlapping drug-eluting stents (DES). The stents were postdilated using a balloon, with the achievement of a good final angiographic result (figure 2 and video 3).

Figure 2.

Coronary angiography showing occluded right coronary artery (RCA) after percutaneous intervention.

Video 3.

Download video file ^{(3.6MB, mp4)}

DOI: 10.1136/bcr-2015-210002.video03

Left ventriculography showing inferior akinesia and mildly reduced left ventricular systolic function.

Outcome and follow-up

The patient's postprocedural hospital stay was complicated by left ventricular dysfunction, pulmonary oedema and hypotension, requiring initial inotropic support (dobutamine infusion). Initial echocardiography showed inferoposterior akinesia with ejection fraction of 35–40%. The patient's pulmonary oedema was treated with diuretics and his inotropic support was gradually weaned off. β-Blocker (bisoprolol), ACE inhibitor (ramipril) and aldosterone antagonist (eplerenone) were started with gradual increments to support his heart failure. At day 10 post-STEMI, the patient was discharged on optimal triple antifailure therapy for further follow-up in the outpatient clinic.

To further evaluate the anatomy of the coronary arteries, CT coronary angiography and three-dimensional construction (figure 3) were performed. These showed an anomalous branch originating from the RCA, and passing between the aorta and pulmonary trunk in an anomalous malignant fashion. The anomalous artery then trifurcated into LAD, ramus intermedius and left circumflex arteries. There was also a second anomalous vessel arising from the RCA just after the origin of the first anomalous artery, which had not been visualised during the primary PCI procedure. The second anomalous artery was a smaller calibre vessel that passed anterior to the pulmonary trunk before joining the LAD artery immediately distal to the trifurcation described (figure 4). The anomalous arteries showed only mild non-obstructive disease.

Figure 3.

Three-dimensional CT angiography (spider view) showing the anomalous origin of the left coronary artery (LCA; seen on coronary angiography) from proximal right coronary artery (RCA) and its interarterial course between aorta and pulmonary artery (not shown on this CT image). The anomalous LCA then trifurcates into left anterior descending (LAD), ramus intermedius and left circumflex arteries. A second anomalous artery was seen on CT (but not on coronary angiography) originating from proximal RCA just distal to the origin of the first anomalous artery and taking an anterior course to the pulmonary artery to merge with the anterior branch of the first anomalous artery to form a dual origin LAD artery.

Figure 4.

Three-dimensional CT angiography (right anterior oblique view) showing RCA with two anomalous branches (LCA, left circumflex artery; RCA, right coronary artery).

To assess exercise capacity and to risk stratify the malignant route of the anomalous left coronary artery (LCA), a treadmill exercise stress was performed 6 months post-STEMI. Despite a baseline ECG of right bundle branch block pattern, the test was progressed to assess the functional capacity of the patient. During the exercise test the patient developed persistent atrial fibrillation without any chest pain. His functional capacity was adequate during the exercise. He was started on apixaban (oral anticoagulant) and had successful elective direct current cardioversion 4 weeks later. He was advised to continue taking aspirin for life. Clopidogrel was stopped 6 months following DES insertion.

It was decided to proceed with an exercise myoview test to assess for myocardial ischaemia once he had been successfully cardioverted. However, shortly following cardioversion, the patient developed further angina-like symptoms over a period of 1 week requiring admission and further evaluation with coronary angiography. The angiogram showed progression of the left coronary system disease from mild-to-moderate severity. Additionally, there was new significant disease in the posterior descending artery (PDA) branch of the RCA. The RCA stents were widely patent. The patient's anginal symptoms were attributed to the progression of coronary artery disease. After discussion with the cardiothoracic surgeons, it was decided to proceed to coronary artery bypass grafting of the RCA as well as the left coronary lesions based on disease progression, malignant course of left coronary system and the patient’s new symptoms. He received a left internal mammary artery graft to the LAD and a saphenous vein graft to the PDA, and had an uneventful recovery from surgery.

Discussion

Coronary artery anomalies, which represent substantial deviations from the normal coronary anatomy, are rare, with an incidence of 0.6–1.3%.¹ While the majority of these anomalies are benign, 20% of cases have been associated with more serious complications such as arrhythmias, syncope, myocardial infarction or sudden death.² Perhaps one of the best-known cases of a single RCA is that of the American professional basketball player, Peter Maravich, who collapsed and died while playing a pickup basketball game at the age of 40. It is remarkable to know that for over 10 years his successful professional career in National Basketball Association was uneventful until he died suddenly of cardiac arrest.³

A valuable classification system for SCAs was introduced in 1979 by Lipton et al,⁴ describing the origin and course of these single coronary anomalies. The anomalous artery was first labelled ‘R’ or ‘L’, depending on which sinus of Valsalva the SCA arose from. It was then divided into group I, II or III. Group I has an anatomical course corresponding to either a right or a LCA. Group II anomalies arise from the proximal part of the normal right or left artery and then cross the base of the heart before assuming the normal position of the absent coronary artery. Group III describes the LAD and the circumflex artery arising separately from the proximal part of the normal RCA. The final label refers to the relationship between the anomalous coronary artery, the aorta and the pulmonary artery, with the letters ‘A’ referring to the anomalous artery passing anterior to the pulmonary artery, ‘B’ referring to a course between the aorta and the pulmonary artery, and ‘P’ referring to the artery passing posterior to the aorta. This classification was modified by Yamanaka and Hobbs¹ with the addition of the ‘septal’ subtype designated ‘S’, describing the passage of the anomalous artery across the crista supraventricularis and through the septum, and the ‘combined’ subtype designated ‘C’, as a combination of the other subtypes.

In the current case, the patient presented with an STEMI following an occlusion in his RCA; however, it is unlikely that the patient's STEMI was a consequence of his anomalous LCA, given the location of the atherosclerosis and thrombus in the distal RCA. Furthermore, studies suggest the incidence of coronary artery disease to be no different in patients with SCA compared with the rest of the population.^{5 6} Of note, if the patient's occlusion had been in his proximal RCA, it would likely have presaged more detrimental consequences, disrupting the entire blood supply to his heart.

The course of the SCA in this case is consistent with an R-IIIC classification described by Yamanaka and Bell.¹ While there have been previously reported cases of this ‘combined’ subtype of the R-III classification,^{7 8} the course of anomalous branches in our case is unusual. The anomalous branch travelling anterior to the pulmonary trunk unites with one of the branches of the anomalous artery that passes between the aorta and pulmonary artery to supply the territory commonly supplied by the LAD artery. To the best of our knowledge, this union has not been seen in previous published cases.

The course of the anomalous artery can have significant prognostic implications. The most serious variant occurs when the left main artery passes between the aorta and the pulmonary artery, as seen in our case. This ‘malignant’ course has been associated with increased risk of myocardial ischaemia, infarction and sudden cardiac death.⁹ However, there have also been reports of angina pectoris and myocardial infarction in patients with anomalous left main course anterior to the pulmonary artery, and posterior to the aorta, in the absence of atherosclerotic disease.^{10 11} As most of these patients experience adverse events during exercise, it has been suggested that exercise induced expansion of the aorta and pulmonary artery causes occlusion of the artery, causing symptoms and potentially fatal arrhythmias.¹²

In order to identify which patients are at higher risk of future events, exercise testing with myocardial perfusion scanning might be helpful. A study undertaken by De Luca et al¹³ on patients with coronary anomalies showed that 80% of patients with anomalous arteries coursing between the great vessels were associated with a reversible myocardial perfusion defect detected by stress–rest technetium-99m-methoxyisobutyl isonitrile single photon emission CT. Patients with perfusion defects detected by myocardial perfusion scanning may benefit from coronary artery bypass surgery.

Coronary artery bypass surgery is also recommended in patients with anomalous left main coronary artery coursing between the aorta and pulmonary artery according to American College of Cardiology/American Heart Association guidelines (class I, level of evidence B).¹⁴ The presented case has ‘dual’ LCA anomalous origins from the RCA, including one with malignant route passing through the great arteries. The patient eventually had surgical revascularisation following recurrent angina attributed to progression of coronary atherosclerotic disease, though it could also be related to compression of the anomalous origins of the LCA.

Patient's perspective.

• I initially thought that the heart attack was due to the abnormal course of the coronary artery but informed by the cardiologists that this is unlikely due to the location and the appearance of the blockage on angiography. I must stop smoking and reduce my weight. I was informed that the course of the artery increases the risk of future heart attacks and abnormal heart rhythms in the future.

Learning points.

• Single coronary arteries are extremely rare but have important prognostic implications placing the patient at increased risk of future myocardial ischaemia, infarction and sudden cardiac death.

• A valuable classification system for single coronary arteries was introduced in 1979 by Lipton et al, and modified by Yamanaka and Hobbs,¹ describing the origin and course of these single coronary anomalies.

• As most of these patients experience adverse events during exercise, it has been suggested that exercise induced expansion of the aorta and pulmonary artery causes occlusion of the anomalous artery, causing symptoms and potentially fatal arrhythmias.

• Exercise myocardial perfusion imaging may be used in the future to identify high-risk patients who would benefit from coronary bypass surgery.

• Coronary artery bypass surgery is recommended when an anomalous left main coronary artery takes a ‘malignant’ route between the aorta and pulmonary arteries due to risk of sudden death.