Loss of electrically active myocardium during inferior infarction in man.

Serial 72 point praecordial electrocardiographic maps were recorded in 19 patients who suffered from uncomplicated inferior myocardial infarction.The natural history of ST segment elevation and of regional loss of R waves and development of Q waves were recorded.Plasma MB creatine kinase activity was measured at intervals during the first four days after the onset of chest pain.The electrocardiographic maps showed that the praecordial area of ST segment elevation reached a maximum within 1 hour then diminished rapidly and disappeared in 18 of the 19 patients within 7 days after the onset of chest pain.The regional loss of R waves occurred within 6 hours from the onset ofpain.The praecordial area of Q waves appeared in the second hour and was fully developed within 12 hours after the onset of chest pain.Electrocardiographic changes indicating loss of electrically active myocardium were almost complete before MB creatine kinase activity appeared in the plasma.The timing of electrocardiographic events in relation to the onset of symptoms and to the detection of cardiospecific enzyme activity in the blood may be important in deciding when to make therapeutic interventions and how to assess their effects on the progressive loss of active myocardium during acute infarction of the heart.There were reciprocal and complicated electrocardiographic manifestations of posterior and/or lateral myocardial involvement in these patients.In addition the praecordial area of ST segment elevation showed rapid resolution in the 4 hours after the onset of pain.For these reasons there was no simple relation between areas of ST segment elevation, the loss of R wave amplitude, and the appearance of Q waves in these patients with inferior myocardial infarction.