Acute myocardial infarction with isolated ST-segment elevation in posterior chest leads V_7-9: 'Hidden' ST-segment elevations revealing acute posterior infarction

OBJECTIVES: This study was done to determine whether electrocardiographic (ECG) isolated ST-segment elevation (ST ↑) in posterior chest leads can establish the diagnosis of acute posterior infarction in patients with ischemic chest pain and to describe the clinical and echocardiographic characteristics of these patients. BACKGROUND: The absence of ST ↑ on the standard 12-lead ECG in many patients with acute posterior infarction hampers the early diagnosis of these infarcts and thus may result in inadequate triage and treatment. Although 40% of all acute myocardial infarction (AMI) patients reveal the presence of isolated ST ↑ in posterior chest leads, the significance of this finding has not yet been determined. METHODS: We studied 33 consecutive patients with ischemic chest pain suggestive of AMI without ST ↑ in the standard ECG who had isolated ST ↑ in posterior chest leads V₇ through V₉. All patients had echocardiographic imaging within 48 h of admission, and 20 patients underwent coronary angiography. RESULTS: Acute myocardial infarction was confirmed enzymatically in all patients and on discharge ECG pathologic Q-waves appeared in leads V₇ through V₉ in 75% of the patients. On echocardiography, posterior wall- motion abnormality was visible in 97% of the patients, and 69% had evidence of mitral regurgitation (MR), which was moderate or severe in one-third of the patients. Four patients (12%), all with significant MR, had heart failure, and one died from free-wall rupture. The circumflex coronary artery was the infarct related artery in all catheterized patients. CONCLUSIONS: Isolated ST ↑ in leads V₇ through V₉ identify patients with acute posterior wall myocardial infarction. Early identification of those patients is important for adequate triage and treatment of patients with ischemic chest pain without ST ↑ on standard 12-lead ECG.