Case Presentation:

A 23 year-old man with no prior medical history presented with witnessed syncope.  Patient was playing basketball when he suddenly collapsed, initially unresponsive, regaining consciousness after minutes.  No seizure activity was observed.  VS were BP 116/71, HR 55, RR 16, O2sat 100% RA.  ECG showed sinus bradycardia with right axis deviation.  Physical exam was benign and neurological exam was non-focal.  Patient had retrograde amnesia, not able to recall the event.  CT head was negative, and chest x-ray revealed an enlarged cardiac silhouette.  Lab values, including troponin, were within normal limits.  Patient reported a similar syncopal episode a few months prior during a basketball game, however no medical care was sought.  Patient denied family history of cardiovascular disease.

A transthoracic echocardiogram (TTE) showed normal left and right ventricular size and systolic function, left ventricular hypertrophy, with no valvular abnormalities and no evidence of hypertrophic obstructive cardiomyopathy (HOCM).  Cardiac MRI (cMRI) revealed an anomalous right coronary artery (RCA) arising from left coronary cusp with interarterial course between the aorta and pulmonary artery, as well as a near transmural myocardial infarction involving the basal, mid and inferior apical walls.  Patient underwent successful unroofing of the RCA and an implantable cardiac monitoring device was placed for long term monitoring.  Repeat TTE showed improved inferior wall motion and coronary flow in the right coronary cusp, and patient was discharged without incident.


Following HOCM, anomalous coronary artery (ACA) represents the second most common cause of sudden cardiac death (SCD) among young people, particularly during high intensity exercise.  ACA is a rare clinical entity, with the RCA most commonly affected.  Most ACA are asymptomatic, discovered incidentally during imaging or angiography.  While often benign, ACA may manifest in a range of symptoms, including palpitations, chest pain, syncope, and infrequently, SCD.  The mechanism behind SCD in ACA is believed to involve an anomalous course of the coronary artery between the aorta and pulmonary artery, where an increase in cardiac output during exercise causes mechanical compression of the artery, resulting in increased resistance in the coronary artery and a decrease in coronary blood flow.

Because the clinical outcome of ACA is often benign, the decision to intervene depends on presentation.  When a patient is symptomatic or shows evidence of ischemia, either percutaneous coronary intervention or surgery is recommended.   The surgical options for ACA include unroofing of the artery or reimplantation of the anomalous vessel in the appropriate coronary sinus.  Unroofing is the preferred procedure in patients without concomitant coronary artery disease.   Most patients resume a normal unrestricted lifestyle after surgery.  

In this case, the abrupt syncopal events on exertion pointed towards a cardiac etiology, and after ruling out HOCM with TTE, cMRI was pursued, confirming ACA.  Given evidence of ischemia and RCA course through the great vessels, surgical unroofing was performed, leading to improvement in cardiac function. 

Conclusions: This case describes a rare condition with a potential fatal outcome. While arrhythmias are common causes of syncope, unexplained exertional syncope especially in a young adult can be caused by ACA.   In these cases, diagnostic imaging or angiography must be considered.