Acute Coronary Syndrome (ACS)

Risk factors

• Non-modifiable: age, male sex, family history of premature CAD (<55 men / <65 women)
• Modifiable: smoking, diabetes, hypertension, dyslipidemia, obesity, sedentary lifestyle
• Other: chronic kidney disease, autoimmune disease, cocaine/methamphetamine use

Pathophysiology

Atherosclerotic plaque rupture or erosion exposes thrombogenic material to circulating blood, triggering platelet aggregation and thrombus formation. Partial occlusion → UA/NSTEMI. Complete occlusion → STEMI. Resulting downstream ischemia → myocyte necrosis if not reperfused.

Clinical presentation

Differential diagnosis

• Aortic dissection — Sudden tearing or ripping chest pain radiating to the back, BP or pulse differential between arms, widened mediastinum on CXR — DO NOT anticoagulate before excluding
• Pulmonary embolism — Sudden pleuritic chest pain, dyspnea, hypoxia, risk factors (immobility, malignancy, OCPs); RV strain on ECG/echo; D-dimer / CTPA
• Pericarditis / myopericarditis — Sharp pleuritic pain improved leaning forward, diffuse concave ST elevation with PR depression, friction rub, recent viral illness
• Takotsubo (stress) cardiomyopathy — Postmenopausal women after major emotional/physical stressor; ECG and troponin mimic STEMI; apical ballooning on ventriculogram or echo
• Tension pneumothorax — Acute dyspnea, unilateral absent breath sounds, tracheal deviation, hypotension — clinical diagnosis; do not delay decompression for CXR
• Esophageal rupture (Boerhaave) — Severe chest/upper abdominal pain after forceful emesis, subcutaneous emphysema, pneumomediastinum on imaging
• GERD / esophageal spasm — Burning, postprandial, worse supine; may respond to nitrates and confuse the picture; PPI trial
• Costochondritis / musculoskeletal — Reproducible with chest wall palpation, no exertional pattern, normal ECG and troponin

Diagnostic workup

Diagnostic algorithm

flowchart TD
  A[Chest pain<br/>≥10 min, suggestive] --> B[12-lead ECG<br/>within 10 min]
  B --> C{ST elevation?}
  C -->|Yes| D[STEMI]
  D --> E[Primary PCI<br/>≤90 min]
  D --> F[Fibrinolysis<br/>if PCI delay]
  C -->|No| G[Troponin<br/>0 and 1-3 h]
  G --> H{Troponin<br/>elevated?}
  H -->|Yes| I[NSTEMI]
  I --> J[Risk stratify<br/>TIMI / GRACE]
  J --> K[Early invasive<br/>≤24 h if high risk]
  H -->|No| L{Ongoing<br/>ischemic Sx?}
  L -->|Yes| M[Unstable Angina]
  M --> N[Medical optimization<br/>+ stress test]
  L -->|No| O[Non-cardiac<br/>workup]

Treatment

Complications

• Arrhythmias: ventricular fibrillation (early, most common cause of death pre-hospital), AV blocks (especially inferior MI), atrial fibrillation
• Mechanical (days 3-7): papillary muscle rupture (acute MR), ventricular septal rupture, free wall rupture (tamponade)
• Heart failure (acute or chronic), cardiogenic shock
• LV thrombus → embolic stroke (especially large anterior MI)
• Dressler syndrome (post-MI pericarditis, 2-10 weeks): pleuritic chest pain, fever, friction rub

PANCE pearls

• Posterior MI = ST depression in V1-V3 with prominent R wave (mirror image). Obtain posterior leads V7-V9.
• Inferior MI (II, III, aVF) with RV involvement (V4R) — preload-dependent. NITRATES AND DIURETICS ARE CONTRAINDICATED. Give IV fluids.
• Wellens syndrome: biphasic or deep symmetric T-wave inversions in V2-V3 = critical proximal LAD stenosis. Often pain-free at presentation. Stress testing contraindicated; cath directly.
• New LBBB with chest pain is treated as STEMI equivalent if Sgarbossa criteria positive.
• Cocaine-induced MI: avoid beta-blockers (unopposed alpha vasoconstriction). Use benzodiazepines, nitrates, CCBs.

Images

References

• ACC/AHA/SCAI 2021 — 2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization (Lawton et al., Circulation 2022)
• AHA/ACC 2014 — AHA/ACC Guideline for the Management of Patients with Non-ST-Elevation Acute Coronary Syndromes (Amsterdam et al., JACC 2014)
• ACCF/AHA 2013 — ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction (O'Gara et al., JACC 2013)
• Universal Definition — Fourth Universal Definition of Myocardial Infarction (Thygesen et al., JACC 2018)