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A 61 year old man presented with a three hour history of chest pain consistent with myocardial ischaemia. Initial ECG (below) demonstrated ST elevation/high take-off in lead V1 with ST depression in leads V2–V6, I, II, and tall R waves in leads V2–V3. These changes were not felt to meet criteria for thrombolytic treatment and this was withheld.
The patient was transferred to the coronary care unit (CCU) with a diagnosis of unstable angina. A portable chest x-ray (right, upper panel) showed that there was left diaphragmatic eventration with displacement of the heart to the right side of the mediastinum. Subsequent right sided and posterior lead ECGs (right, lower panel) were performed which showed ST elevation of 2 mm in leads V2–V3 consistent with anterior infarction. Thrombolytic treatment was not given because of the time which had elapsed from symptom onset.
Displacement of the heart within the thorax may obscure the classic 12 lead ECG changes of acute myocardial infarction and lead to misdiagnosis and inappropriate withholding of thrombolytic treatment. In such cases, the initial use of non-standard ECG lead positions is recommended for accurate diagnosis and treatment.