Isolated Posterior Myocardial Infarct: The Deadly Nightshade of the Electrocardiography

Author : B.D.Guntoro, D.Ilmasari, M.G.Soewandi
Upload Date : 19-04-2018

Background: Isolated posterior myocardial infarct (PMI) is less common to occur, only 3-11% of myocardial infarcts. Patients with isolated PMI is commonly missed or delayed in diagnosis in Emergency Department because the electrocardiography (ECG) showed no “typical” pattern of myocardial infarct such as ST-segment elevation in common 12-lead of ECG. These patient usually diagnosed as non ST-Elevation (NSTEMI) myocardial infarct, in fact, those depression are the “shadow” of a lethal isolated posterior ST-Elevation myocardial infarct.

Case Report: A 62-year-old man was admitted to the Emergency Department. He complained of chest pain with no radiating pain followed by epigastric pain, nausea and vomitting. On physical examination, blood pressure was 160/70 mmHg and heart rate was 77 beats/min. On auscultation normal heart sounds and no murmur heart sound was heard. He was an active smoker since adolescent. The first 12-leads of ECG showed normal sinus rhythm. Serial 12-lead of ECG was taken every 15 minutes. Two hours later there were changes in ECG with atypical ST-segment depression and R wave elevation in lead V1-V3 (figure 1.A). At first examination of ECG, he was diagnosed as NSTEMI. He was given with aspirin 320 mg, clopidogrel 300 mg, atorvastatin 40 mg, lansoprazole 30 mg. Then, the posterior lead was taken 15 minutes later. There were ST-segment elevations in the posterior leads V7 to V9 (figure 1.B). Then, he was diagnosed as isolated posterior ST-segment elevation myocardial infarction. After that, he received thrombolysis. Thrombolysis was followed by rapid normalization of ST-segment depression in lead V1-V3 and the ST-segment elevation in lead V7-V9 (figure 2) accompanied by cessation of chest pain. Laboratory results confirmed the diagnosis of MI: CK-MB was 48 U/L.

Conclusion: Isolated posterior myocardial (PMI) is still a challenging predicament to be diagnosed in emergency department (ED). The depression of ST-segment in lead V1-V3 is atypical and looks more like a shadow of posterior ST-segment elevation. These atypical depression in lead V1-V3 described as: a horizontal or downsloping ST depression, a wide and tall R wave, a tall and upright T wave, and R/S ratio >1. The additional posterior ECG leads V7-V9 is needed to confirm these “deadly nightshade” in the lead V1-V3 in order to diagnose an isolated PMI with ST-elevation. Therefore, the ability to diagnose PMI is  important especially for general practitioner related to patient management.

KEYWORDS : Isolated posterior myocardial infarction (PMI), electrocardiography

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