Difficulties in the electrocardiographic diagnosis of a previous posterior myocardial infarct

: A retrospective study was carried out of 39 cases of posterior m.i. from 8 months to 6 years after acute episode. In each case the diagnostic reliability of the standard derivations of a series of parameters was evaluated (duration of Q D3 and Q aVF, Q.100/R ratio in aVF, R/S ratio in V1 and R V1/R V6) and of the following accessory derivations: De Maria, III P of Pescador (classical and in two personal modifications), dorsal and sternal derivations. It is concluded that in many cases, standard derivations do not enable previous posterior m.i. to be diagnosed. The De Maria and III P of Pescador derivations (with the proposed personal modifications) are advisable. In isolated cases, the sternal derivation may also be very useful.