A 13-year-old boy was admitted to our department after an out-of-hospital cardiac arrest during physical exertion. Transitory ST-segment elevation in the anterior chest leads was noted after defibrillation. At 48 h, initial evaluation was performed. Twelve-lead EKG and telemetry were normal. Transthoracic echocardiography showed normal left ventricle (LV) size and global function. Segmental two-dimensional (2D) longitudinal strain of the anterior wall was significantly decreased when compared with the other segments, and was associated with post-systolic shortening. Coronary angiography and 64-slice computed tomography revealed an anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA). ALCAPA is a rare congenital malformation. The usual clinical course is a severe left-sided heart failure and mitral valve insufficiency presenting during the first months of life. In some cases, collateral blood supply from the right coronary artery is sufficient and symptoms may be subtle or even absent. However, ventricular arrhythmias or sudden cardiac death during exercise may be the first clinical presentation in patients with ALCAPA. Indirect evidence suggests that myocardial ischaemia is the underlying aetiology of cardiac ventricular ischaemia in patients with ALCAPA. Post-systolic shortening and altered longitudinal strain have recently been described as potential useful markers of ischaemic dysfunction in patients with ischaemic heart disease. In this case report, we demonstrate the usefulness of 2D strain as a non-invasive tool to assess subclinical myocardial ischaemia in patients with an ALCAPA. This provides further supportive evidence for the role of cardiac ischaemia in aetiology of ventricular arrhythmia in this rare condition.