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In our article, we describe the clinical course, echocardiographic and angiographic findings of 33 consecutive patients with acute myocardial infarction and ST segment elevation in posterior chest leads V7–9 but without significant ST segment elevation on the standard 12-lead ECG. Because these ST segment elevations are not presented on the classically performed 12-lead ECG, we called them “hidden” (in quotation marks).
Like Dr. Hurst, who taught all of us through his textbook, we were also much inspired by the vectorcardiographic approach to electrocardiography so beautifully presented in Grant’s book (1). However, the chest with the lungs full of air is not an ideal volume conductor, and the heart is not in the exact middle of it. Most of the time, whenever there is ST segment elevation in leads V7–9, ST segment depression will be detected in the anterior chest leads. However, there will always be cases, as we show here, where the nonuniformity of the chest and other factors will result in distorted spread of potential, leading to the absence of reciprocal changes in leads V1–3, despite QRS–ST-T segment changes in leads V7–9.
We fully agree with the general statement by Dr. Hurst that there are two ways to interpret the ECG: one is to memorize patterns and the other is to use basic principles of electrocardiography. But they are not mutually exclusive, and sometimes the principles of volume conduction and nonuniformity and distorted spread of potential will result in the changes we presented.
The posterior chest leads V7–9 ECG recording is simple and feasible, and the appearance of ST segment elevations in posterior chest leads V7–9 can be detected easily by any physician, even without a deep understanding of basic ECG principles.
We believe that the early detection of ST segment elevation posterior myocardial infarction in the era of reperfusion is crucial for the identification of patients with acute posterior myocardial infarction, who may benefit from reperfusion therapy.
- American College of Cardiology
- ↵Grant RP. Clinical electrocardiography: The spatial vector approach. McGraw Hill Book Company: New York, 1957.