Two Cases of ST-Segment Elevation

Case 1:
Middle-aged Man With Chest Pain and Dyspnea

A 51-year-old man with hypertension, type 2 diabetes mellitus, and hypercholesterolemiapresents with a 1-hour history of substernal chest discomfort anddyspnea. He was given sublingual nitroglycerin in the emergency department,but his symptoms did not resolve.Based on the presenting ECG, what is the most likely cause of hissymptoms?

A.

Inferior wall myocardial infarction (MI).

B.

Posterior wall MI.

C.

Anterior wall MI.

D.

Lateral wall MI.

E.

Anterolateral wall MI.

F.

Acute pericarditis.

Case 1: Middle-aged man with chest pain and dyspnea.

The ECG tracingshows an

anterolateral wall MI,

E.

The most striking abnormality is the markedST-segment elevation in the anterolateral leads (V

₂

through V

₆

and I,aVL).A useful tool for crude ECG localization of MI is a classification providedby the American Heart Association

¹

:

• Anterolateral: ST-segment elevation in leads V₃ through V₆ (occasionally Iand aVL).
• Anterior: ST-segment elevation in leads V₃ and V₄.
• Anteroseptal: ST-segment elevation in leads V₁ through V₄.
• Lateral: ST-segment elevation in leads V₅ and V₆ (occasionally I and aVL).
• Inferior: ST-segment elevation in leads II, III, and aVF.
• Posterior: Wide R wave in V₁ and V₂.

Patients with pericarditis may present with diffuse ST-segment elevationand PR-segment depression. Although this patient has ST-segment elevation ina number of leads, the ST segments in III and aVF are depressed. This inferiorST-segment depression represents

reciprocal

changes from the acute anterolateralinjury.In this patient, a total occlusion of the proximal left anterior descendingcoronary artery was successfully treated with intracoronary stenting.

REFERENCE:
1.

Surawicz B, Uhley H, Borun R, et al. The quest for optimal electrocardiography. Task Force I: standardizationof terminology and interpretation.

Am J Cardiol.

1978;41:130-145.

Case 2:
Middle-aged Woman With Abdominal Discomfort and Vague Chest Pain

A 60-year-old hypertensive woman presents with a 3-hour history of abdominaldiscomfort and vague chest pain that began after dinner. She experienced nauseaand vomiting an hour before admission.Which of the following does the ECG implicate as the most likely cause ofher symptoms?

A.

Inferior wall myocardial infarction (MI).

B.

Right ventricular MI.

C.

Anterior wall MI.

D.

Inferolateral wall MI.

E.

Anterolateral wall MI.

F.

Acute pericarditis.

Case 2: Middle-aged woman with abdominal discomfort and vague chestpain.

The ECG tracing shows an

acute inferolateral wall MI,

D.

The moststriking abnormality is the marked "tombstone" ST-segment elevation in theinferior leads (II, III, and aVF). There is ST-segment elevation in leads I andaVL, which represents lateral injury. This pattern is typical of inferolateral MI.There is also evidence of anterior

reciprocal

ST-segment depression, whichmay represent posterior wall involvement.The following are additional discriminating criteria for inferior MI:

• ST-segment elevation in I, aVL, V₅, and V₆ suggests lateral wall involvement.
• ST-segment depression in V₁ through V₃ suggests reciprocal changes and/orposterior wall subepicardial injury.
• ST-segment elevation in V₁ suggests right ventricular infarction (not presentin this patient's ECG).

In contrast, acute pericarditis would present with more diffuse ST-segmentelevation and PR-segment depression.It is very rare for acute MI to result from simultaneous occlusion of morethan 1 major coronary artery. The culprit may be a large right coronary arterythat supplies the posterolateral and distal anterior wall (by "wrapping around"the cardiac apex). A second possibility is a large left circumflex artery.In this patient, a total occlusion of the proximal right coronary artery wassuccessfully treated with intracoronary stenting.