Elsevier

Journal of Electrocardiology

Volume 44, Issue 5, September–October 2011, Pages 494.e1-494.e12
Journal of Electrocardiology

ST elevation: differentiation between ST elevation myocardial infarction and nonischemic ST elevation

https://doi.org/10.1016/j.jelectrocard.2011.06.002Get rights and content

Abstract

It is well accepted that early reperfusion is beneficial in patients with acute myocardial infarction presenting with ST elevation (STE). Earlier studies suggested lack of beneficial effects in patients presenting without STE and even with ST depression. Currently, time to reperfusion is considered to be a quality of care measure, and the latest American College of Cardiology/American Heart Association guidelines for the treatment of STE acute myocardial infarction (STEMI) emphasize that the physician at the emergency department should make reperfusion decisions within 10 minutes of performing the initial electrocardiogram (ECG). However, not all ECGs with STE necessarily reflect transmural infarction from acute thrombotic occlusion of an epicardial coronary artery, as a large number of patients presenting with compatible symptoms have baseline STE. In some cases a pattern of benign nonischemic STE (NISTE) can be recognized fairly easily. Other times, differentiating between true STEMI and NISTE may be difficult. It should be remembered that patients presenting with chest pain and showing benign pattern of NISTE (eg, “early repolarization” or STE secondary to left ventricular hypertrophy) may have true ischemic pain and non-STE myocardial infarction or even STEMI on top of the baseline benign pattern. It seems that, in the “real world,” the ability of physicians to differentiate NISTE from STEMI based on the presenting ECG pattern widely varies and depends on the prevalence of baseline NISTE in the patient population. Further studies are needed to assess the ability of various ECG criteria to accurately differentiate between STEMI and NISTE.

Section snippets

“Concave” versus “convex” pattern of STE

The ST segment reflects ventricular depolarization and is normally isoelectric with the PR and TP segments. It is commonly taught that STE in which the ST segment morphology is upwardly convex or straight is consistent with STEMI compared with a concave morphology, which is associated with NISTE. The ACC/AHA guidelines suggest that it is less likely that STEMI is present if the upward-directed ST-segment changes are concave rather than convex.1 However, Smith16 reported that 43% of patients

Early repolarization

The typical pattern of early repolarization NISTE shows STE of 1-4 mm in the lateral leads (mainly V5-V6). It may also involve the inferior leads. There is a characteristic notch at the J-point (Fig. 2). The ST segment is usually concave, and tall, peaked T waves may be present. Early repolarization NISTE is commonly seen in young males. In many cases, STE is transient and ameliorates or even disappears with tachycardia and hyperventilation. Thus, dynamic changes in the degree of STE are not

A “normal-variant” pattern of NISTE

A “normal-variant” STE is defined as ST elevation mainly in leads V1-V3 (Fig. 4).5 It is common in young males, mainly African American and Hispanic. In contrast to the NISTE seen in patients with left ventricular hypertrophy (LVH), there are no QRS criteria for LVH present and there is no concomitant ST depression in the lateral leads. Some investigators do not differentiate between a “normal variant” pattern and “early repolarization” pattern, lumping all together as “early repolarization.”

STE secondary to LVH

NISTE secondary to LVH is typically seen in leads V1-V3. Usually, there are QRS criteria for LVH and concomitant ST depression in the lateral leads V5-V6 (Fig. 5). In many cases, there is also STE in lead aVR. It is important not to confuse this pattern with the pattern reported to be related to left main related or global ischemia (STE in leads aVR and V1 with ST depression in the inferior and anterolateral leads). It should be remembered that, according to the “Universal Definition of

Acute pericarditis

The classical ECG pattern of acute pericarditis is diffuse STE in all leads, except leads V1 and aVR, which instead may show ST depression (Fig. 7). Typically, the pattern of STE in pericarditis does not fit a single vascular territory. Depression of the PR interval below the isoelectric line is commonly seen early in the course of pericarditis. However, focal pericarditis after STEMI or cardiac surgery may result in more localized and atypical forms of STE, which may manifest ST depression in

STE secondary to IVCD

LBBB is commonly associated with marked ST changes (Fig. 8). ST deviation is usually discordant to the direction of the major deflection of the QRS complex due to presence of secondary ST-T wave abnormalities. Acute myocardial infarction, on the other hand, is more likely to present with primary ST-T wave abnormalities (ie, deviation that is concordant to the QRS complex.) Because patients with LBBB usually have negative QRS deflections in leads V1-V3, they usually display prominent STE in

Brugada syndrome

The Brugada pattern of NISTE shows an RBBB pattern with STE in the anterior leads.31, 32 The Brugada syndrome is associated with a high risk for ventricular tachyarrhythmia and sudden cardiac death. Type 1 Brugada is characterized by a coved STE >0.2 mV, followed by a negative T wave in >1 right precordial leads (V1-V3) in the presence or absence of a sodium channel blocker and in conjunction with documented ventricular fibrillation, polymorphic ventricular tachycardia, a family history of

Takotsubo syndrome (apical ballooning syndrome)

Apical ballooning syndrome is more common in postmenopausal women and classically occurs following acute emotional or physiologic stress. Patients present with chest pain and/or shortness of breath, and their ECG may show STE (81.6% of the patients, mainly in the precordial leads), T-wave abnormalities (64.3%) and Q waves (31.8%). Mild elevation of cardiac markers has been reported in 86.2% of the patients.34 In many cases, the initial presentation is indistinguishable from anterior STEMI,

Spontaneously reperfused STEMI

The current guidelines for STEMI recommend that patients with suggestive symptoms of myocardial ischemia within the preceding 12 hours presenting with STE in ≥2 adjacent ECG leads (>0.1 mV at the J-point) should undergo immediate reperfusion therapy.1 The guidelines do not mention the entity of (spontaneously) reperfused STEMI at all, and they do not mention ongoing symptoms as a prerequisite for immediate reperfusion therapy. A large number of patients may have (partial) resolution of symptoms

Left ventricular aneurysm

Left ventricular aneurysm is another diagnosis to be aware of as it may cause persistent STE after a previous myocardial infarction that, at times, may be indistinguishable from acute STEMI. Diagnosis is especially difficult when previous ECG tracings are unavailable. At one hospital in Minnesota, a patient received systemic thrombolytics on 2 separate occasions in the emergency room because of chronic STE from a previous LV aneurysm after an old MI (//hqmeded-ecg.blogspot.com/2008/11/65-yo-male-with-recent-rule-out.html

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