Post partum creatine phosphokinase and its muscle-brain isoenzyme elevation and transient Q-wave in a patient with idiopathic hypertrophic subaortic stenosis.

A primigravida with idiopathic hypertrophic subaortic stenosis, New York Heart Association Classification III, developed acute chest pain with significant ST segment depression together with a new Q-wave in chest lead V6 on the electrocardiograph following delivery under lumbar epidural analgesia. An intrapartum myocardial infarct was suspected because serial creatine phosphokinase and its muscle-brain isoenzyme levels were elevated in the postpartum period. However, the ST segment and the Q-wave changes returned to baseline within 4 h, thus eliminating the possibility of acute myocardial infarction. The uterus and placenta release creatine phosphokinase and its muscle-brain isoenzyme substantially during normal vaginal delivery, thus mimicking acute myocardial infarction. Consequently, the elevations of creatine phosphokinase and its muscle-brain fraction alone are not diagnostic of myocardial infarction in the postpartum period. The diagnosis of myocardial infarction must be based on the clinical picture, serial electrocardiogram recording and determination of lactate dehydrogenase and aspartate amino transferase.