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Chapter 39: Evaluation and Management of Non–ST-Segment Elevation Myocardial Infarction

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Which of the following factors is associated with a low likelihood that chest pain is caused by myocardial ischemia attributable to obstructive coronary artery disease (CAD)?

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A. Known coronary disease (particularly recent PCI)

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B. Typical angina reproducing prior documented angina

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C. Hemodynamic or ECG changes during pain

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D. Dynamic ST-segment elevation or depression of ≥1 mm

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E. T waves flat or inverted < 1 mm

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The answer is E. (Hurst’s The Heart, 14th Edition, Chap. 39) T wave flattening or low-level inversion (< 1 mm) is associated with a lower likelihood of obstructive CAD as the basis for chest symptoms, whereas more marked symmetric T-wave inversion in multiple precordial leads is highly suggestive of CAD. A number of factors increase or decrease the likelihood of CAD (Table 39-1; answers A through D are incorrect).

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Table 39-1. Likelihood that Chest Symptoms Are Caused by Myocardial Ischemia Attributable to Obstructive Coronary Artery Disease

High likelihood

Known coronary disease (particularly recent PCI)

Typical angina reproducing prior documented angina

Hemodynamic or ECG changes during pain

Dynamic ST-segment elevation or depression of ≥1 mm

Marked symmetric T-wave inversion in multiple precordial leads

Elevated cardiac enzymes in a rising and falling pattern

Intermediate likelihood

Absence of high-likelihood features and any of the following:

Typical angina in a patient without prior documented angina

Atypical anginal symptoms in diabetics or in nondiabetics with two or more other risk factors

Male gender

Age older than 70 y

Extracardiac vascular disease

ST depression 0.5-1.0 mm or T-wave inversion of ≥1 mm

Low-level troponin elevation that is “flat” and does not rise or fall

Low likelihood

Absence of high- or intermediate-likelihood features but may have:

Chest discomfort reproduced by palpation

T waves flat or inverted < 1 mm

Normal ECG

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A 55-year-old woman with a history of hypertension and obstructive sleep apnea presents with two days of an intermittent “squeezing” sensation in her chest. The last episode was approximately six hours ago. Which of the following is true about the use of the electrocardiogram to diagnosis an acute coronary syndrome?

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A. Persistent 0.5 mm ST segment depression is strongly suggestive of an acute coronary syndrome

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B. T-wave inversions do not localize well the territory of myocardial ischemia

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C. The presence of ST depressions confers a higher risk of 30-day mortality

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D. The presence of isolated T-wave inversions confers a worse prognosis compared with ST depression

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E. None of the above are true

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The answer is C. (Hurst’s The Heart, 14th Edition, Chap. 39) Even minor ST depression is associated with a markedly increased mortality rate. Among ...

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