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Open Access 01-12-2018 | Letter
Letter on “Pre-hospital transthoracic echocardiography for early identification of non-ST-elevation myocardial infarction in patients with acute coronary syndrome”
Published in: Critical Care | Issue 1/2018
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We read with interest the manuscript by Bergmann et al. [1] but believe it is fraught by several conceptual and methodological flaws, the main ones being:-
The authors used interchangeably the terms “transthoracic echocardiography”, “focus echocardiography”, and “focus cardiac ultrasound”(FoCUS) without the clear distinction required by the potential major clinical implications [2]; the screening for regional wall motion abnormalities (RWMA) is in fact clearly considered by international consensus beyond the scope of the limited training and application that FoCUS entails [3, 4], and the level of echocardiographic education/competence of emergency physicians was not detailed.
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The authors state: “A diagnosis of NSTEMI was based on the combination of ACS symptoms, lack of ST-segment elevation, and RWMA. Myocardial infarction was excluded in the absence of the latter.” Non-transmural infarctions compromising a small amount of necrotic myocardium may not be detectable on 2D-echo. It has been shown that RWMA detectable by echocardiography occur if resting coronary flow is reduced by > 50%, if > 20% of myocardial thickness is jeopardized by actual ischemia/necrosis, or if at least 1–6% of the left ventricle mass is involved [5].
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Previous myocardial infarction is indicated as an exclusion criterion. But a screening for myocardial scars or signs of pre-existing left ventricle disease was omitted from the exam, and a subsequent re-reading of the images by a blinded expert was omitted too, which may have led to potential false positives in non-ST-segment myocardial infarction (NSTEMI) diagnosis.