Electrocardiographic patterns of acute coronary occlusion that do not meet STEMI criteria

How can you identify patients who need an immediate trip to the cath lab if they do not meet STEMI criteria? 

We're all familiar with the guideline based metric for door to balloon time of 90 minutes or less for ACS patients who meet criteria for ST segment elevation MI. STEMI is a surrogate for acute epicardial coronary occlusion and therefore the need for immediate reperfusion therapy. In this paradigm, ACS cases that do not meet STEMI criteria are designated as non-ST segment elevation myocardial infarction (NSTEMI). Less well appreciated, however, is that up to 30% of ACS cases not meeting STEMI criteria actually have acute coronary occlusion. Because these occlusions tend to go unrecognized and are not under the CMS “quality” metric of door to balloon time, these are patients with acute coronary occlusions who are often deprived of timely reperfusion. Multiple studies indicate that such patients have a higher mortality even compared to STEMI patients who do get timely reperfusion. Most of these patients can be recognized electrocardiographically as they generally fall into several patterns listed below. However, these can be subtle and require a certain degree of electrocardiographic interpretation skill.

Hyperacute T waves:  these are upright T waves of high amplitude and increased width such that they have an increased area under the curve. They may be the earliest signs of coronary occlusion and may be present without ST segment elevation

DeWinter T waves: these are hyperacute T waves preceded by J point ST segment depression. This pattern is diagnostic of acute LAD occlusion although not meeting STEMI criteria.

Wellens syndrome:  this is a pattern of anterior precordial T wave inversion that occurs after resolution of chest pain. It indicates a proximal LAD occlusion that has recently reperfused. Such patients have a very high incidence of catastrophic anterior STEMI within the coming two weeks and do not respond to medical management.

Precordial swirl pattern:. this is a pattern of ST elevation in V1 and V2 combined with lateral precordial ST segment depression. The ST segment elevation may be subtle and not meet STEMI criteria. This is indicative of proximal LAD occlusion.

South African flag sign: this is a combination of ST elevation in Leeds 1 and AVL and depression in lead 3. There is concomitant ST segment elevation in V2. The pattern is indicative of acute diagonal branch occlusion.

Aslanger pattern:. this is a variant of inferior MI but the ST segment elevation is in lead 3 only. It is accompanied by ST segment depression in any of V4-6. There is also subtle ST elevation in  V1 greater than V2, not enough to meet STEMI criteria. This is indicative of inferior MI, usually circumflex occlusion but occasionally RCA occlusion. It is seen in patients with multivessel disease and is indicative of a large infant.

Terminal QRS distortion:. this is generally seen in LAD occlusions and is manifested by disappearance of the S wave in the anterior precordial leads. It is often accompanied by hyperacute T waves and occasionally may occur before ST segment elevation is seen and therefore not meet STEMI criteria.

Subtle anterior ST segment elevation not meeting STEMI criteria: this pattern can be confused with either normal variant anterior ST elevation, particularly in males, or benign early repolarization. There are a couple of formulas that involve the QT interval, the R&S wave amplitude and the degree of ST elevation in V3 which have good test characteristics for differentiation between early anterior STEMI and these normal variants.

Posterior infarction: because we generally do not employ posterior leads this is a mirror image of posterior current of injury and is seen as ST segment depression in V1-4. It does not meet STEMI criteria and is often missed.

Sgarbossa criteria in left bundle branch block and right ventricular pacing: this consists of concordant ST segment changes. Remember that in left bundle branch block and RV pacing ST segment changes should normally be discordant from the major portion of the QRS. 

Northern OMI pattern: this pattern consists of ST segment elevation in aVL and aVR  accompanied by by T wave inversion in those same leads, and ST segment depression in other leads. It is often indicative of occlusion at the takeoff of the diagonal branch.  It does not meet STEMI criteria.

Right bundle branch block, with or without left anterior fascicle block, not known to be old:  in the context of suspected acute myocardial ischemia, this finding indicates proximal LAD occlusion and a very large infarct with high mortality and high risk of acute complications including pulmonary edema, cardiogenic shock, septal rupture and complete heart block with asystole.  The downward secondary ST segment forces in the anterior leads (due to the RBBB) may obscure the ST elevation and thus fail to meet STEMI criteria.  Moreover, the RBBB itself may be a distractor from what is really going on.

Inferior infarction with only minimal STE not meeting STEMI criteria with reciprocal aVL depression as the principal abnormality.

These patterns are detailed in the paper linked below:

ECG Patterns of Occlusion Myocardial Infarction: A Narrative Review

Tables and Graphics from the paper are displayed here.