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Acute Coronary Syndrome (ACS)

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Acute coronary syndrome (ACS)

Commonly known as a heart attack — irreversible necrosis of myocardial tissue caused by prolonged ischemia, most often due to occlusion of a coronary artery.

Also called

sudden, heart-related emergencies

ICD-10

I24.9

Specialty

Cardiology

Onset

Acute

Reviewed

June 2026

On This Page

Overview

Acute coronary syndrome (ACS) is a group of conditions caused by acute myocardial ischemia resulting from partial or complete occlusion of a coronary artery.

Acute coronary syndrome (ACS) Includes :
• Unstable Angina (UA)
• Non-ST-Segment Elevation Myocardial Infarction (NSTEMI)
• ST-Segment Elevation Myocardial Infarction (STEMI)

Etiology & Risk Factors

Main Cause

  • Acute partial or complete coronary artery occlusion
  • Reduced coronary blood flow causes myocardial ischemia

Types

  • Partial occlusion → Unstable Angina or NSTEMI
  • Complete occlusion → STEMI

Pathophysiology

Mechanism:

Coronary Artery Occlusion
↓
Reduced Myocardial Blood Supply
↓
Myocardial Ischemia
↓
Acute coronary syndrome (ACS).

ACS TypeCoronary Artery StatusPathophysiological MechanismMyocardial InvolvementTroponin
Unstable Angina (UA)Partial coronary artery occlusionReduced coronary blood flow causes myocardial ischemia without infarctionNo myocardial necrosis/infarctionNormal
NSTEMIUsually partial coronary artery occlusionAcute myocardial ischemia leading to infarction of the inner myocardial layerSubendocardial infarctionElevated
STEMIUsually complete coronary artery occlusionComplete interruption of blood flow causing extensive myocardial infarctionTransmural infarction (full-thickness myocardium)Elevated

Clinical Presentation

  1. Symptoms Of Acute coronary syndrome (ACS)

    • • Acute retrosternal chest pain
    • • Dull pressure or chest tightness
    • • Angina at rest
    • • Angina with minimal exertion
    • • Persistent or worsening (crescendo) angina
    • • Usually not relieved by rest

     

Anginal Equivalents–>Shortness of breath

 

Associated Symptoms

    • • Diaphoresis (sweating)
    • • Nausea
    • • Vomiting
    • • Palpitations
    • • Syncope

History Taking

Diagnosis rests on the combination of clinical history, ECG findings, and cardiac biomarkers.

Key Questions

  • • Character of chest pain
  • • Onset and duration
  • • Radiation
  • • Presence at rest or with exertion
  • • Previous episodes
  • • Response to nitroglycerin
  • • Associated dyspnea
  • • Nausea or vomiting
  • • Syncope
  • • Palpitations

Red Flags

  • • Hemodynamic instability
  • • Acute pulmonary edema
  • • Tachyarrhythmias
  • • Bradyarrhythmia
  • • Cardiogenic shock

Physical Examination

General Examination

• Assess using the ABCDE approach.

Look For

• Signs of hemodynamic instability
• Signs of cardiogenic shock
• Pulmonary edema
• Arrhythmias

Monitoring
• Continuous telemetry
• Pulse oximetry

Long-term secondary prevention typically includes dual antiplatelet therapy, a high-intensity statin, a beta-blocker, an ACE inhibitor or ARB (especially with reduced ejection fraction), and structured cardiac rehabilitation.

Investigations

  • Essential Tests

    ECG

    • • Immediate 12-lead ECG

    Cardiac Biomarkers

    • • Cardiac troponin (cTn)
    • • Serial troponin measurements

    Laboratory Tests

    • • CBC
    • • BMP
    • • BNP or NT-proBNP
    • • Coagulation panel
    • • Lipid profile

    Monitoring

    • • Serial ECGs
    • • Continuous cardiac monitoring

Diagnosis

Diagnostic Criteria For Acute coronary syndrome (ACS)

STEMI

  • • ST-segment elevation in two contiguous leads or new LBBB
  • • Elevated troponin

NSTEMI

  • • No ST-segment elevation
  • • Elevated troponin

Unstable Angina

  • • No ST-segment elevation
  • • Normal troponin
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Management of Acute coronary syndrome (ACS)

Initial Management for All ACS Patients

Monitoring

  • • Continuous telemetry
  • • Serial ECGs
  • • Serial troponins

Oxygen

  • • Supplement oxygen as needed to maintain saturation ≥ 90%

Antiplatelet Therapy

  • • Aspirin
  • • P2Y12 inhibitor
  • • Dual antiplatelet therapy (DAPT)

Anticoagulation

  • • Parenteral anticoagulation (e.g., UFH)

Additional Medical Therapy

  • • Statins
  • • Beta blockers
  • • RAAS inhibitors
  • • Analgesia for chest pain

MONA-BASH Mnemonic

LetterTherapy
MMorphine
OOxygen
NNitroglycerin
AAntiplatelet drugs
BBeta blockers
AACE inhibitors
SStatins
HHeparin

Revascularization

STEMI

  • • Immediate revascularization
  • • Preferred: Primary PCI
  • • Fibrinolytic therapy if timely PCI unavailable

NSTE-ACS

  • • Timing determined by risk stratification
  • • Cardiology consultation required

PCI

  • • Preferred revascularization strategy
  • • Balloon dilation with stent implantation

CABG (Selected Cases)

  • • Large myocardium at risk
  • • Cardiogenic shock
  • • Hemodynamic instability
  • • Unsuccessful PCI
  • • Coronary anatomy unsuitable for PCI
  • • Mechanical complications

Complications of Acute coronary syndrome (ACS)

Serious Complications

  1. •Cardiogenic shock
  2. •Acute heart failure
  3. •Acute pulmonary edema
  4. •Ventricular tachycardia (VT)
  5. •Ventricular fibrillation (VF)
  6. •Complete heart block

 

Mechanical Complications

  • •Papillary muscle rupture
  • •Ventricular septal rupture

Prognosis of Acute coronary syndrome (ACS)

ACS subtype

  • Extent of myocardial injury
  • Presence of cardiogenic shock
  • Success and timing of revascularization
  • Hemodynamic stability

Key Points / Clinical Pearls of Acute coronary syndrome (ACS)

  • • ACS includes unstable angina, NSTEMI, and STEMI.
  • • Troponin differentiates MI from unstable angina.
  • • ECG differentiates STEMI from NSTEMI.
  • • STEMI usually results from complete coronary occlusion and requires immediate revascularization.
  • • NSTEMI and unstable angina are usually caused by partial coronary occlusion.
  • • Initial evaluation should include 12-lead ECG and cardiac troponin.
  • • Core therapies include DAPT, anticoagulation, statins, beta blockers, and RAAS inhibitors.
  • • PCI is the preferred revascularization strategy.
  • • Watch closely for cardiogenic shock, pulmonary edema, and life-threatening arrhythmias.