ST-elevation myocardial infarction (STEMI)

This page works the case through in full, answer included. If you would rather reason it out yourself: Play this case

How the diagnosis is reached

Exertional chest pain with sweating and nausea is acute coronary syndrome until an ECG says otherwise, and here the ECG settles it. Three millimetres of ST elevation across V2 to V4 is a contiguous anterior territory rather than the diffuse saddle-shaped elevation of pericarditis, and the reciprocal ST depression in the inferior leads is what separates a true infarct from the mimics that also elevate ST segments; the absent friction rub argues the same way. Those leads also localise the culprit before angiography does, since V2 to V4 is left anterior descending territory. The troponin is the trap. Forty minutes in, mildly elevated is exactly right, since the rise lags the occlusion by hours, and a normal value would have excluded nothing. Nobody waits for it. Muscle downstream of the proximal LAD is dying now, so the only question left is which method reopens the artery soonest. That is primary PCI wherever it can be reached in time: mechanical reopening with a stent, target under 90 minutes from first contact. Past about 120, transfer delay costs more than the drug does, so a fibrinolytic (tenecteplase, alteplase) is given and the patient sent for angiography afterwards regardless. It is a fallback rather than an equal, reopening roughly half of arteries against over ninety per cent, with a bleeding risk PCI lacks. Either way aspirin and a P2Y12 inhibitor such as ticagrelor start immediately, since the clot is platelet-rich and an opened vessel re-occludes without them.

Key clinical clues

• Crushing chest pain radiating to arm/jaw with diaphoresis, classic ACS presentation
• ST elevation in V2–V4 localizing to the anterior wall (LAD territory)
• Anterior wall motion abnormality on echocardiogram
• Angiography confirming proximal LAD occlusion
• Time-critical reperfusion is the priority, PCI preferred, fibrinolysis if unavailable

The case in full

1

Presenting complaint

Patient history

A 58-year-old man presents to the emergency department with crushing central chest pain that started 40 minutes ago while shoveling snow. The pain radiates to his left arm and jaw and is associated with sweating and nausea.

2

Physical examination

Physical examination

He appears pale and diaphoretic. Cardiac and respiratory exams are otherwise unremarkable, with no murmurs or friction rub.

Measurements

Parameter	Value	Reference
Heart rate	98 bpmRef 60–100	60–100
Blood pressure	152/94 mmHg	–
SpO₂ (room air)	96 %Ref 95–100	95–100

3

Cardiac biomarkers

Laboratory results

A high-sensitivity troponin is drawn on arrival.

Measurements

Parameter	Value	Reference
High-sensitivity troponin	Mildly elevatedRef Below assay cutoff	Below assay cutoff

4

12-lead ECG

ECG

The ECG shows 3 mm ST-segment elevation in leads V2 through V4, with reciprocal ST depression in the inferior leads.

5

Bedside echocardiogram

Imaging

A focused echocardiogram shows a regional wall motion abnormality of the anterior wall with reduced overall ejection fraction.

6

Cardiac catheterization

Clinical course

The catheterization lab is activated. Coronary angiography reveals a complete occlusion of the proximal left anterior descending (LAD) artery.