Incomplete ECG expression of acute true posterior myocardial infarction, owing to an antecedent anterior infarction.

摘要

We present a 75-year-old man with an inferior and true posterior (TP) myocardial infarction (MI), who showed disproportionately deeper ST-segment depression (decreased ST) in the precordial electrocardiogram (ECG) leads than the ST-segment elevation (increased ST) noted in leads 2, 3, and aVF. This suggested that the precordial decreased ST was not reciprocal to the inferior increased ST, but it was indicative of TP ischemic injury. However, the precordial decreased ST, in subsequent serial ECGs, was not followed up by R waves of increasing amplitude, or tall T waves in the V1 and V2 leads, as would be expected had this been a case of evolving TP MI. Nevertheless, TP MI was confirmed by echocardiography and dipyridamole/thallium SPECT myocardial perfusion scintigraphy. These last 2 modalities also revealed evidence of an anterior (A) MI, which had indeed occurred 11 years previously, and was confirmed by a history of hospitalization, serial ECGs, and enzymatic evidence of necrosis. This incomplete ECG expression of TP MI in our patient was felt to be owing to the previous large A MI, which had long ago deprived the heart from requisite healthy myocardium opposite the recent TP MI, for generation of tall R waves or R/S ratio greater than 1 in the V1 and V2 leads. This case is presented as an example of electrical cancellation affecting the QRS complexes.