Читать книгу Practical Cardiovascular Medicine - Elias B. Hanna - Страница 94

STEMI is a clinical syndrome of angina or angina equivalent along with:^1–3

 ST-segment elevation ≥2 mm in men or ≥1.5 mm in women in leads V2–V3, or ≥1 mm in two other contiguous chest or limb leads, with a shape consistent with ischemic ST elevation. The shape must be distinguished from early repolarization, pericarditis, or ST-segment elevation secondary to LVH or LBBB; emergent echo or coronary angiography may be performed in case of doubt.

or:

 Isolated or most prominent ST-segment depression in leads V1–V3 ≥ 0.5 mm, which is reciprocal to posterior ST elevation in leads V7-V9 (true posterior STEMI). In leads V7–V9, the ST-segment elevation cutoff is only 0.5 mm, as the distant location of these leads behind the heart minimizes ST-segment elevation.

ST-segment elevation below these cut-points may still imply myocardial injury when the clinical setting or the ST-segment morphology suggests ischemia. Emergent reperfusion may still be indicated in these patients, generally with PCI (thrombolysis is not an established therapy for mild degrees of ST elevation, <1 mm).

Conversely, ST-segment elevation that exceeds these cut-points may not represent STEMI. Careful attention to the morphology of the ST segment and the associated features (Q wave, inverted or ample T wave) is critical.

STEMI usually evolves into electrocardiographic Q waves (Q-wave MI) and is usually a transmural and large MI. NSTEMI usually evolves into a non-Q-wave MI and is usually a subendocardial, smaller MI. However, there is some overlap: STEMI may not generate Q waves while NSTEMI may generate Q waves.

Since it takes up to 3 hours for troponin to rise after the onset of infarction, it should not be relied upon for the diagnosis or initiation of emergent therapies.

Approximately 12.5% of MIs are totally silent and ~12.5% have a mild, atypical presentation (e.g., dyspnea, malaise, nausea).⁴ These cases go unrecognized, and patients may present with HF days or months after acute MI. This presentation is more common in diabetic and elderly patients.