This patient has an anomalous right coronary artery (ARCA) originating from the anterior side of the ascending aorta and coursing between the pulmonary trunk and ascending aorta (= inter-arterial course).  

An ARCA with an inter-arterial course has a severe prognosis and is therefore referred to as malignant. 

Symptomatology is thought to be caused by the rising pressure within both the aorta and pulmonary artery during exercise, thereby compressing the anomalous coronary artery by a scissor-like mechanism.