Masking Inferior Infarction by Anterior Myocardial Injury
A 64-year-old female with a history of myocardial infarction (MI) after angioplasty presented with jaundice, abdominal distention, and 6-week weight loss. The initial work-up revealed an old inferior Q-wave MI on the admission ECG (Figure 1) and evidence of a malignant obstruction at the common bile duct. On day 7, while waiting for surgery, the patient developed chest pain and myocardial injury pattern in leads V2 through V6, causing disappearance of the old inferior Q-wave MI pattern (Figure 2). Four hours later, the myocardial injury pattern in leads V2 through V6 resolved, and the inferior Q-wave MI pattern reappeared (Figure 3). Her troponin I levels during and after the resolution of the myocardial injury were normal.
It is a well known electrocardiographic principle that electrical forces in one zone reciprocally change the QRS vector on the opposite myocardial zone. The masking of an old inferior Q-wave MI by acute anterior MI has been reported.1 Separately, the unmasking of an inferior infarction was also observed after the surgical revascularization of an anterior infarct.2 This case is an elegant proof to the above principle, as it provides a rare opportunity to observe in one patient the masking of inferior Q-wave MI upon the development of an anterior myocardial injury, and the reappearance of an inferior Q-wave MI on a spontaneous resolution of the anterior ischemia.