Partial occlusion of a coronary arterial vessel results in an incomplete reduction of arterial supply to a region of myocardium. In the great majority of these cases, this does not result in ST segment elevation on the ECG. Myocardial ischaemia secondary to partial occlusion of a coronary arterial vessel manifests on the ECG in a number of different ways. The classical ECG abnormalities associated with ischaemia are depression of the ST segment below the isoelectric line or inversion of T waves in leads with dominant R waves (loss of concordance). On occasion, ischaemia manifests as a combination of both ST depression and T wave inversion.