Silent Single Coronary Artery Anomaly Depicted by Magnetic Resonance Angiography

Coronary artery anomalies are rare and represent about 1.3% of coronary angiograms.1,2 They are usually asymptomatic. They can be clinically significant in a case of single coronary artery anomaly, as the left main artery (LMA) courses in between the origin of the ascending aorta and the pulmonary trunk. We report an unexpected case of single coronary artery anomaly, diagnosed in a 72-year-old patient. Magnetic resonance (MR) angiography was performed to pinpoint the type of anomaly prior to surgical planning. Case Report. A previously symptom-free 72-year-old patient presented with a first episode of left cardiac failure and atrial fibrillation, combined with a right bundle branch block. No cardiac enzymes appeared in subsequent blood samples. Echocardiography diagnosed an important tricuspid aortic valve stenosis, associated with a severe left ventricular dysfunction. A selective coronary angiogram demonstrated that the LMA originated from the proximal part of the right coronary artery (RCA). Significant stenosis on the proximal left circumflex artery (LCX) and distal RCA were demonstrated (Figure 1). A left ventricular (LV) angiogram revealed moderate aortic valve stenosis (1.28 cm2 with a gradient of 35 mmHg), an ejection fraction of 37% and severe LV dysfunction. Due to this unsuspected anomaly, a breath-holding coronary MR angiography was performed to depict the course of the coronary anomaly. The patient was examined in a supine position with a Symphony Quantum 1.5 T System (Siemens, Erlangen, Germany). A body array surface coil was positioned at the level of the heart. Electrocardiogram (ECG)-triggered HASTE sequences during a breath-hold technique were obtained in sagittal oblique sections, which allowed us to recognize the coronary anomaly (20 sections of 4 mm with a 10% gap; matrix of 150 x 256 with a field of view (FOV) of 400 x 450 mm; TE = 48 ms; TR = RR). Twelve contiguous ECG-triggered 2-dimensional breath-holding segmented gradient echo images were obtained from the root of the ascending aorta down to the left ventricular apex (Figure 2) (single slice technique of 5 mm; matrix of 144 x 256 mm with a FOV of 245 x 280 mm; TE = 7.4 ms; TR = RR). The ECG-triggered end-diastolic data acquisitions were segmented over 17 heartbeats, during breath holding. The epicardial fat signal was suppressed using a spectral selective radiofrequency pulse. A 3-dimensional ECG-triggered breath-holding gradient echo sequence with an interpolation in the slice selective direction was performed (48 sections of 1.33 mm; matrix of 150 x 256 mm with a FOV of 263 x 300 mm; TE = 1.6 ms; TR = 4.0 ms) prior to and during a bolus injection of intravenous gadolinium (Figure 3). The course of the single coronary artery anomaly was precisely depicted. The LMA anomaly originated from the proximal part of the RCA and coursed in between the roots of the aorta and the pulmonary trunk. It then reached the proximal left anterior descending artery (LAD). The LCX coursed backward from the proximal LAD and its proximal stenosis was also demonstrated. The patient benefited from combined aortic valve and bypass surgery. The radiological diagnosis was confirmed during surgery. A 1-month post-operative echocardiography showed normalization of the LV function, without kinetic trouble. Follow-up at 6 months was event free. Discussion. Single coronary artery anomaly is classified according to its right (R) or left (L) coronary origin.2 Type L means that the RCA arises from the LMA and courses between the aorta and the pulmonary artery. Type R means that the left coronary system originates from the RCA. In type R/I, the RCA, LAD and LCX originate from the right sinus of Valsalva. In type R/II, the LMA originates from the proximal RCA and courses either anteriorly (type R/II/A) or posteriorly (type R/II/P) to the pulmonary artery. In type R/II/P, mechanical compression of the LMA can occur, especially during exercise, and induce myocardial ischemia or sudden death.3,4 Bicuspid aortic valve has been demonstrated to be associated with single coronary artery anomaly in humans and animals,5 but this association was not observed in our case. We report a case of unexpected single coronary artery anomaly in a previously asymptomatic 72-year-old patient, diagnosed during catheterization. The left cardiac failure episode presented by the patient was probably due to the association of atrial fibrillation and aortic valve stenosis, and not related to the coronary anomaly. In our case, selective coronary angiography could not determine whether it was a type R/II/A or R/II/P. The surgical and general anesthesia planning will be affected by this distinction. MR angiography has been shown to be accurate in depicting the origin and course of the coronary anomaly,6–8 as well as their relations with surrounding anatomic structures, allowing differentiation between type A or P. Specific advantages of MR imaging, compared to transesophageal echocardiography, are its noninvasive property, non-operator dependence and high spatial resolution. Coronary artery angiograms still have the advantage of depicting the entire course of the vessels in one frame, but similar images can be obtained with post-processing MR angiography techniques.9 In our case, MR angiography clearly demonstrated this unsuspected single coronary anomaly to be type R/II/P.

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