Identifying the J point (defined as the end of the QRS) can be challenging in the presence of R′. The end of the QRS can be identified in a sequentially recorded limb lead. The intersect (B) identifies the J point and C is the degree of ST elevation, from the isoelectric line (PQ and TP segments excluding any U wave) and J point. V1 and V2—fourth intercostal space, V3 and V4—third intercostal space, and V5 and V6—second intercostal space.⁴³