ST ELEVATION Question: what causes acute myocardial infarction? Answer: An occlusive thrombus that is recognized on an electrocardiogram by ST-segment elevation.

Learning Objective Recognize ST segment elevation in conditions other than acute MI Question: how is ST elevation determined? Answer: Level of the ST segment should be measured in relation to the end of the PR segment, not the TP segment

Significance Unwarranted thrombolytic therapy Unnecessary emergency angiography Unnecessary anxiety (for intern)

Case 25y/o healthy male presents with chest pain and the following EKG findings Pt is a normal healthy 25y/o MALE with no significant past medical history and no history of drug use. Question: should this pt be sent to the cath lab? Answer: The correct answer is NO and the reason for this will be explained in the following examples. This case will then be brought up again at the end of this presentation for further discussion.

Example 1: Normal ST elevation 1 - 3mm elevation in one or more precordial leads in relation to the end of the PR segment (male pattern) ST segment is concave In a study of 6014 healthy men in the U.S. Air Force who were 16 to 58 years old, 91 percent had ST-segment elevation of 1 to 3 mm in one or more precordial leads. Since the majority of men have ST elevation of 1 mm or more in precordial leads, it is a normal finding, not a normal variant, and is designated as a male pattern; ST elevation of less than 1 mm is designated as a female pattern. In these patterns, the ST segment is concave.

Example 2: Early Repolarization Most commonly the ST-segment elevation is most marked in V4 with a notch at the J point, and the ST segment is concave T waves are tall and are not inverted Clinical studies have failed to demonstrate an earlier-than-normal onset of ventricular recovery. Thus, we see this elevation of the ST segment.

Example 3: T-wave Inversion This normal variant differs from the early- repolarization pattern in that the T waves are inverted and the ST segment tends to be coved Combination of an early-repolarization pattern and a persistent juvenile T-wave pattern. Often, the findings are so suggestive of acute myocardial infarction that an echocardiogram is necessary to differentiate them, especially if one is not aware of this normal variant. In most cases of this normal variant, the QT interval is short, whereas it is not short in acute infarction or pericarditis.

Example 4: LV Hypertrophy Deep S wave QS pattern in leads V1 through V3 Elevated ST segment is concave in a pt with uncomplicated LV hypertrophy as compared with convex in a pt with acute concomitant MI FYI: EKG example is found on the next page.

Things to point out: Deep S wave 2) QS pattern in leads V1 through V3 3) Elevated ST segment is concave in a pt with uncomplicated LV hypertrophy as compared with convex in a pt with acute concomitant MI 4) Contrast this with convexity seen in Column 5 and 6(RBBB + true ST elevation MI), lack of deep S

Example 5: Left Bundle Branch Block Making the dx of acute infarction in the presence of LBBB can be problematic, since the ST segment is either elevated or depressed secondarily, simulating or masking an infarction pattern Sgarbossa’s criteria is controversial and has not been validated NOTE: If you are seeing a new LBBB, you should treat like an acute MI because there is no good evidence or criteria to differentiate if this is not an MI. FYI: EKG example is found on the next page.

Things to point out: LBBB pattern Concavity of ST elevation Again, LBBB is tricky and if this is a new finding from previous EKGs, this should be treated as ST elevation MI.

Example 6: Pericarditis +Myocarditis ST segment is elevated diffusely in the precordial leads as well as in the limb leads, indicating involvement of more than one coronary vascular territory, which rarely happens in acute myocardial infarction In addition, the PR segment is depressed, and such depression is the atrial counterpart of ST- segment elevation ST-segment elevation in patients with acute pericarditis does not result in reciprocal ST depression Physiology: Diffuse pericarditis involves not only the subepicardial layer of the ventricular wall, which is responsible for the ST-segment elevation, but also the subepicardial layer of the atrial wall, which causes an atrial injury pattern. Depression of the PR segment, however, is not specific for acute pericarditis, since early repolarization or atrial infarction can also cause the depression. FYI: EKG example is found on the next page.

Things to point out: 1) ST-segment elevation in patients with pericarditis seldom exceeds 5 mm, whereas it may in patients with acute infarction 2) ST segment is elevated diffusely in the precordial leads as well as in the limb leads 3) PR segment is depressed, and such depression is the atrial counterpart of ST-segment elevation 4) ST-segment elevation in patients with acute pericarditis does not result in reciprocal ST depression

Example 7: Hyperkalemia Tall, pointed, and tented T waves Widened QRS complexes Low-amplitude or no P waves Elevated ST segment is often downsloping, a finding that is somewhat unusual in acute myocardial infarction, which is more likely to be characterized by an ST segment that has a plateau or a shoulder or is upsloping FYI: EKG example is found on the next page.

Things to point out: 1) Tall, pointed, and tented T waves seen most significantly in V3 2) Widened QRS complexes 3) Low-amplitude or no P waves 4) Elevated ST segment is often downsloping

Example 8: Brugada Syndrome Right bundle-branch block and ST- segment elevation in the right precordial leads in the absence of long QT intervals and any structural heart disease ST-segment elevation is primarily limited to leads V1 and V2 FYI: EKG example is found on the next page.

Things to point out: 1) Right bundle-branch block and ST-segment elevation in the right precordial leads 2) ST-segment elevation is primarily limited to leads V1 and V2

Case 25y/o healthy male presents with chest pain and the following EKG findings Pt is a normal healthy 25y/o MALE with no significant past medical history and no history of drug use. Question: should this pt be sent to the cath lab? Answer: The answer is clearly no. Here, we see a male with ST elevation but the ST elevation is notably concave, in the precordial leads, and consistent with normal ST elevation seen in >90% of the population. Other considerations for the etiology of the chest pain should be explored.

Here is simply a summary table of the different etiologies of ST elevation other than MI.

Summary The shape of the ST-segment elevation, the leads involved, other features of the EKG, the clinical setting, and most important, awareness of the conditions that mimic infarction can help differentiate the conditions

References Kyuhyun Wang, Richard W. Asinger, and Henry J.L. Marriott. ST-Segment Elevation in Conditions Other Than Acute Myocardial Infarction N Engl J Med 2003; 349:2128-2135