Chest pain and MI comparison

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chest pain differential diagnosis myocardial infarction ECG ST elevation

Here is a comprehensive comparison of Chest Pain as a symptom versus Myocardial Infarction (MI) as a specific diagnosis, drawing from Goldman-Cecil Medicine, Robbins Pathology, and Ganong's Review of Medical Physiology.

Chest Pain vs. Myocardial Infarction — A Clinical Comparison

1. Overview

Feature	Chest Pain (Symptom)	Myocardial Infarction (Diagnosis)
Nature	Cardinal symptom — not a diagnosis	Specific disease entity with defined criteria
Definition	Discomfort/pain in the thoracic region	Necrosis of myocardium due to ischemia
Diagnostic criteria	None — it is a presenting complaint	Abnormal cardiac biomarkers + evidence of acute myocardial ischemia (2018 joint task force)
Causes	Broad — cardiac, pulmonary, GI, MSK, vascular	Coronary artery occlusion (≥90% thrombotic)

2. Causes of Chest Pain (Differential Diagnosis)

Chest pain has a vast differential. Clinicians must rule out life-threatening causes first:

Cardiac (ischemic)

Acute MI
Unstable angina / Acute Coronary Syndrome (ACS)
Stable angina pectoris

Cardiac (non-ischemic)

Pericarditis — pain may mimic MI; key finding is a pericardial rub; ECG shows diffuse concave ST elevation (vs. localized, convex "tombstone" in STEMI)
Aortic dissection — sudden, severe pain radiating to the back; hypertension, Marfan syndrome risk factors

Pulmonary

Pulmonary embolism — pleuritic pain + dyspnea ± hemoptysis
Pulmonary hypertension — exertional pain + severe dyspnea ± cyanosis
Pneumonia, pleuritis, pneumothorax

Gastrointestinal

Esophageal reflux or spasm
Peptic ulcer disease, cholecystitis

Musculoskeletal

Chest wall pain (most common in children)
Precordial catch syndrome (Texidor's twinge)

Women and older individuals may not experience classic anginal chest pain even with advanced coronary disease. — Goldman-Cecil Medicine

3. Myocardial Infarction: Pathogenesis

The typical MI sequence (Robbins Pathology):

Plaque disruption — atherosclerotic plaque erodes/ruptures due to endothelial injury, mechanical forces, or intraplaque hemorrhage
Platelet activation — adhesion, aggregation, release of TXA₂, ADP, serotonin → vasospasm
Coagulation cascade — tissue factor exposure → thrombus growth
Complete occlusion within minutes → ischemia → necrosis

Angiography within 4 hours of MI onset shows coronary thrombosis in ~90% of cases. By 12–24 hours, evidence drops to 60%, as some thrombi lyse spontaneously. — Robbins & Kumar Basic Pathology

Non-atherosclerotic causes (~10%): vasospasm (Prinzmetal angina), embolism from mural thrombi (e.g., AF), vasculitis, amyloid, sickle cell disease.

4. ACS Spectrum: Distinguishing MI from Other Chest Pain

Condition	Troponin	ST Changes	Definition
Unstable Angina	❌ Negative	No ST elevation	Cardiac chest pain at rest/worsening, no necrosis
NSTEMI	✅ Positive	No ST elevation	Cardiac pain + myonecrosis, no ST elevation
STEMI	✅ Positive	Persistent ST elevation (>20 min)	Full-thickness ischemia, acute occlusion

The chest discomfort of unstable angina is clinically indistinguishable from that of acute MI, except it may be more clearly precipitated by activity and more rapidly responsive to antianginal therapy. — Goldman-Cecil Medicine

5. ECG Changes in MI (Ganong's Physiology)

Three sequential electrical events occur after coronary occlusion:

Defect in Infarcted Cells	Current Flow	ECG Change
Rapid repolarization	Out of infarct	ST segment elevation
Decreased resting membrane potential	Into infarct	TQ depression → manifest as ST elevation
Delayed depolarization	Out of infarct	ST segment elevation

Evolution over time:

Acute (hours): ST elevation — the hallmark of STEMI
Days–weeks: ST normalizes; Q waves develop (electrically silent scar)
Non-Q-wave infarcts: less severe but higher risk of reinfarction

Acute inferior STEMI with tombstone ST elevation in II, III, aVF and reciprocal depression in V1–V3

Acute inferior STEMI: convex/tombstone ST elevation in inferior leads with reciprocal depression

Acute pericarditis ECG — diffuse concave ST elevation, no reciprocal changes

Acute pericarditis: diffuse concave ST elevation across multiple territories — key distinction from STEMI

6. Key Clinical Distinguishing Features

Feature	Suggests MI/ACS	Suggests Non-Cardiac
Quality	Pressure, squeezing, heaviness	Sharp, stabbing, pleuritic
Radiation	Neck, shoulder, arm, jaw	Localized, no radiation
Duration	>20 min (STEMI), variable (UA)	Seconds or reproduces on palpation
Triggers	Exertion or rest	Inspiration, movement, food
ECG	Localized ST elevation, Q waves	Diffuse ST (pericarditis), normal
Biomarkers	Troponin elevated	Normal troponin
Response to nitrates	Often improves	Variable
Associated symptoms	Diaphoresis, nausea, dyspnea	Fever (pericarditis), dyspnea (PE)

7. Therapeutic Implications

STEMI: Early thrombolysis and/or angioplasty (PCI) is highly effective in limiting necrosis — every minute counts
NSTEMI/UA: Antiplatelet therapy, anticoagulation, risk stratification with serial troponins
Type 2 MI: Treat the underlying cause (e.g., tachycardia, anemia, hypotension)
Aortic dissection: Thrombolytics are contraindicated — diagnosis must be excluded first
Pericarditis: NSAIDs/colchicine; steroids avoided in acute setting

Sources: Goldman-Cecil Medicine (International Ed.) · Robbins & Kumar Basic Pathology · Ganong's Review of Medical Physiology (26th Ed.) · Rosen's Emergency Medicine

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