abnormal heart electrocardiography waveform feature abnormal J wave 2026-04-20T12:07:14Z abnormal Osborn wave any anomaly in the positive convex deflection that occurs at the junction of the QRS complex and ST segment, the J-point MP:0031721 MPheno.ontology The J wave is a deflection with a dome or hump morphology that appears on the ECG after the QRS complex or as a small secondary R wave (R′). J waves are commonly associated with hypothermia but also seen in other conditions, including myocardial ischemia, hypercalcemia, brain injury, and sepsis. Their most critical implication is their arrhythmogenic potential, particularly as precursors to malignant ventricular arrhythmias including ventricular fibrillation.