Acute coronary syndromes

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Acute Coronary Syndrome Chapters

Heart Attack Patient Information

Unstable Angina Patient Information



Unstable Angina
Non-ST Elevation Myocardial Infarction
ST Elevation Myocardial Infarction



Risk Factors

Differential Diagnosis


AHA/ACC Guidelines for Acute Coronary Syndrome

Guideline for Risk Stratification in ACS
Guideline for Pre-Hospital Evaluation and Care
Guidelines for Initial Management of ACS
Guidelines for Patients with Atrial Fibrillation Complicating ACS

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Yamuna Kondapally, M.B.B.S[2]; Tarek Nafee, M.D. [3]; Sabawoon Mirwais, M.B.B.S, M.D.[4]

Synonyms and Keywords: ACS


Acute coronary syndrome (ACS) refers to any group of symptoms attributed to obstruction of the coronary arteries. The most common symptom prompting diagnosis of ACS is chest pain, often radiating to the left arm or angle of the jaw, pressure-like in character, and associated with nausea and sweating. Acute coronary syndrome usually occurs as a result of one of three problems: ST-elevation myocardial infarction (30%), non ST-elevation myocardial infarction (25%), or unstable angina (38%). These types are named according to the appearance of the electrocardiogram. There can be some variation as to which forms of myocardial infarction (MI) are classified under acute coronary syndrome.

ACS should be distinguished from stable angina, which is chest pain which develops during exertion and resolves at rest. New onset angina however should be considered as a part of acute coronary syndrome, since it suggests a new problem in a coronary artery.Though ACS is usually associated with coronary thrombosis, it can also be associated with cocaine use. Cardiac chest pain can also be precipitated by anemia, bradycardias or tachycardias.



The symptoms of acute coronary syndrome include:

  • Chest discomfort described as:
    • pain
    • pressure
    • tightness
    • burning.
  • In contrast to the pain described in stable angina as deep, poorly localized retrosternal chest discomfort that is reproducible with activity or emotional stress and relieved promptly (within less than 5 minutes) by rest and/or short-acting nitroglycerin, ACS patients tend to experience the episodes that are more severe and prolonged, may occur at rest, or may be precipitated by less exertion than the patient's previous experiences.
  • Pain frequently radiates to the left arm, left shoulder, back, jaw, neck, or epigastric region
  • Some patients may not have chest pain and present with other symptoms, known as "anginal equivalents", including:
  • Syncope may be a rare presentation of ACS.

The following features are usually in favor of the non-ischemic nature of pain:

  • Pleuritic pain: sharp or stabbing pain increased in intensity by respiration or cough
  • Pain reproduced with movement or palpation
  • Pain which can be localized by the tip of 1 finger
  • Brief episodes of pain (lasting a few seconds)
  • Pain with maximal intensity at onset
  • Primary or the only location of pain in the middle or lower abdomen
  • Pain radiating to lower extremities


For more information on atherosclerotic plaque, click here.

The pathophysiology of acute coronary syndromes depends on coronary atherosclerotic plaque which includes:

Initiation and Progression of Coronary Atherosclerotic Plaque

Plaque Vulnerability

The plaque vulnerability depends on the following factors:[1]


The pathogenesis of acute coronary syndrome depends on:

Following plaque rupture or endothelial erosion, the subendothelial matrix is exposed to the circulating platelets, which get activated leading to thrombus formation. Two types of thrombi can form:

  • White clots: Platelet-rich clots which partially occludes the artery
  • Red clots: Fibrin rich clots superimposed on white clots and cause total occlusion of the artery

Risk Factors

Common risk factors in the development of acute coronary syndrome are:[2]


  • Diagnosis of acute coronary syndrome needs a combination of:
    • careful history
    • physical examination
    • Electrocardiography (ECG)
    • serum markers of myocardial injury
  • According to the 2014 ACC/AHA guidelines for managing Non-ST-elevation ACS, clinical assessment and initial evaluation of patients with suspected ACS should include risk stratification based on the likelihood of ACS as well as adverse clinical outcomes. These assessments would help for the decision on the need for hospitalization and guide in choosing appropriate treatment strategies.
  • In all patients with suspected ACS these two questions should be answered:
    • 1) What is the likelihood that this patient is having ACS?
      • The likelihood that symptoms and signs represent an ACS can be assessed according to the table below.

"The likelihood that Signs and symptoms reflect an underlying ACS"

Feature High

(Any of the Following)


(Absence of High-Likelihood Features and Presence of Any of the Following)


(Absence of High- or Intermediate-Likelihood Features but May Have the Following)

  • Chest or left arm pain or discomfort as chief symptom
  • Known history of CAD, including MI
  • Chest or left arm pain or discomfort as chief symptoms
  • Age older than 70 yr, male gender
  • Probable ischemic symptoms in absence of any of the intermediate likelihood characteristics
  • Recent cocaine use
Physical examination
  • Transient MR murmur
  • Hypotension
  • Diaphoresis
  • Pulmonary edema or rales
  • Extracardiac vascular disease
  • Chest discomfort reproduced by palpation
  • New, or presumably new, transient ST-segment deviation (1 mm or more)


  • T-wave inversion in multiple precordial leads
  • Fixed Q waves
  • ST depression 0.5 to 1 mm


  • T-wave inversion more than 1 mm
  • T-wave flattening or inversion less than 1 mm in leads with dominant R waves
  • Normal ECG
Cardiac markers
  • Elevated cardiac TnI, TnT, or CK-MB levels
  • Normal
  • Normal
    • 2) What is the likelihood of adverse clinical outcome(s) in this patient?
      • Several risk assessment scores and clinical prediction algorithms have been used to identify patients who are at high risk of developing adverse outcomes.
      • These risk scores and algorithms use an integration of clinical history, physical examination findings, ECG, and cardiac troponins.
      • The most common risk assessment tools include:
        • TIMI (Thrombolysis In Myocardial Infarction) risk score
        • PURSUIT (Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy) risk score
        • GRACE (Global Registry of Acute Coronary Events) risk score
        • NCDR-ACTION (National Cardiovascular Data Registry-Acute Coronary Treatment and Intervention Outcomes Network) registry (
      • The following risk scores have been designed to specifically assess patients presenting to the ED with chest pain:
        • Sanchis score
        • Vancouver rule
        • Heart (History, ECG, Age, Risk Factors, and Troponin) score
        • HEARTS3 score
        • Hess prediction rule

Differential Diagnosis

Diagnosis of ACS is initiated by a clinical suspicion based on a thorough history of the patient's symptoms. Subsequently, confirmatory tests should be ordered to confirm the diagnosis, identify the specific cause of ACS, or to rule out other possible differentials. In some circumstances, utilizing a clinical prediction tool may be beneficial in guiding the clinician's diagnosis. View the page on diagnosis using the clinical prediction rule for ACS for more detail. Acute Coronary Syndrome (ACS) may be differentiated from other diseases as follows:

Organ System Diseases Presentation Diagnostic Tests Past Medical History Other Findings
Chest Pain GI Symptoms Pulmonary Neck
On Palpation On inspiration Radiating to Extremeties Radiating to Back With Movement Nausea or Vomitting Epigastric Pain Odynophagia or Dysphagia Shortness of Breath Jugular


Cardiac Biomarkers CBC Findings ESR D-Dimer EKG


CXR Findings DM Hyperlipidemia Obesity Trauma Inxn* Htn
Cardiovascular Acute Coronary Syndrome + + + + + + + + + + + Palpitations


Aortic Dissection + + + - + + - + •Pain maximal upon onset •Pain difficult to treat with opiates

Weak pulse in one arm compared to other


•Symptoms similar to stroke


Brugada Syndrome No chest pain + Syncope

Cardiac arrest

ST-segment elevation

•F/H of sudden cardiac death

Takotsubo carditis Sudden onset of chest pain mimicking myocardial infarction + + + + + - •Extreme emotional or physical stresssyncope


ST segment elevation

Left ventricular apical ballooning on echo

Normal coronary arteries

Pericarditis + + + •Relieving factor: Sitting up and leaning forward

•Aggravating factor: Lying down and breathing deep

+ + + + + + + •Other causes:Malignancy, autoimmune disorders, chest trauma

Pericardial friction rub

Organ System Diseases Presentation Diagnostic Tests Past Medical History Other Findings
Chest Pain GI Symptoms Pulmonary Neck
On Palpation On inspiration Radiating to Extremeties Radiating to Back With Movement Nausea or Vomitting Epigastric Pain Odynophagia or Dysphagia Shortness of Breath Jugular


Cardiac Biomarkers CBC Findings ESR D-Dimer EKG


CXR Findings DM Hyperlipidemia Obesity Trauma Inxn* Htn
Pulmonary Pleuritis
+ + + + Aggravating factor: Deep breathing + + + + + + •Other causesPulmonary embolism, malignancy, autoimmune diseases
Pulmonary Embolism + •Aggravating factors: Deep breathing, coughing, eating, bending and stooping + + + •Other causes: Immobility, pregnancy, oral contraceptive pills
Pneumonia + + + + + + •Complications: Sepsis, ARDS, Lung abscess
Gastrointestinal GERD + + + •Other symptoms: Hoarseness, Dry cough at night, Sensation of lump in throat etc
Esophageal Spasms + + + + + + + • Risk factors: Anxiety or depression and drinking wine, very hot or cold foods
Esophagitis + + + + + + + • Causes: Hiatal hernia, infection, medications, radiation therapy
Gastritis + + + + + + + • Causes: H.pylori infection, bile reflux, alcohol use, alcohol use
Organ System Diseases Presentation Diagnostic Tests Past Medical History Other Findings
Chest Pain GI Symptoms Pulmonary Neck
On Palpation On inspiration Radiating to Extremeties Radiating to Back With Movement Nausea or Vomitting Epigastric Pain Odynophagia or Dysphagia Shortness of Breath Jugular


Cardiac Biomarkers CBC Findings ESR D-Dimer EKG


CXR Findings DM Hyperlipidemia Obesity Trauma Inxn* Htn
Musculoskeletal Muscle sprain/Spasm + + + + • Causes: Over use, dehydration, electrolyte abnormalities
Costochondritis + + + + + + + + + + + • Risk factors: Rheumatoid arthritis, ankylosing spondylitis, Reiter's syndrome
Rib fracture/Trauma + + + + + + + + + + • Complications: Pneumothorax, hemothorax, surgical emphysema
Psychiatry Anxiety (Panic Attack) Chest tightness + + • Other symptoms: Palpitations, trembling, sweating, choking, light headed, hot or cold flashes.

The following table summarizes the significant history, and diagnostic test findings that will help differentiate the acute coronary syndromes from one another, as well as from other coronary artery diseases:

Acute Coronary Syndromes History and Symptoms Pathology Diagnostic tests Treatment Complications Prognosis
Chest pain Duration of Chest pain Coronary Artery Plaque Cardiac Biomarkers
(e.g.CK-MB, Troponins)
EKG Findings Medical Therapy Reperfusion
(e.g. PCI, CABG, or Medical)
At Rest Exertion
Unstable Angina + + <30 minutes Partial occlusion Erosion




Normal •Normal EKG findings (some cases)

•Flipped or inverted T waves

•ST segment depression

•Non-specific ST-T changes

+ Arrhythmias

Congestive heart failure


New mitral regurgitation


•Sudden death

•1 year mortality rate is 1.7%
NSTEMI + + >30 minutes Partial or complete occlusion Rupture




Elevated •No EKG findings (some cases)

•Flipped or inverted T waves

•ST segment depression

•Non-specific ST-T changes

New left bundle branch block

+ + Arrhythmias

Congestive heart failure


New mitral regurgitation

Ventricular aneurysms

•Sudden death

•1 year mortality rate is 24.4%

•30 day mortality rate is about 2%

STEMI + + >30 minutes Complete occlusion Rupture

(50%-75%) or


Elevated •ST elevation in at least 2

contiguous leads in V2-V3

•ST depression in at least

two precordial leads V1-V4

•ST depression in several

leads plus ST elevation in

lead aVR (suggestive of occlusion of the left main or proximal LAD artery)

+ + Reinfarction


Left ventricular aneurysm


rupture of papillary muscle,

interventricular septum and LV free wall

•Sudden death

•30 day mortality rate is

1.1% in <45 yrs and 20.4% in >75 yrs patients

Other Coronary Artery Diseases
Chronic stable angina - + ≤ 5 minutes Severely narrowed

coronary vessels

Stable plaque Normal •Normal EKG in 50% of cases

•Down sloping, up sloping or

horizontal ST segment depression

•T wave inversion

+ Heart failure •Estimated annual mortality rate is 0.9%-1.4%

•Annual incidence of non-fatal MI between 0.5%-2.6%

•1 year mortality rate is 1.3%

Prinzmetal's angina •Occur at rest

(Mid night to early morning)

•Not associated with exertion

5-30 minutes Coronary artery vasospasm - Normal •Transient ST segment elevation + Arrhythmias


•5 year survival is excellent (90%-95%)

Differential Diagnoses of Acute Coronary Syndromes in the Setting of Chest Pain

Cardiac Pulmonary Vascular Gastrointestinal Orthopedic Other


Pulmonary embolism Aortic dissection Esophagitis, reflex or spasm Musculoskeletal disorders Anxiety disorders
Tachyarrhythmias (Tension)-Pneumothorax Symptomatic aortic aneurysm Peptic ulcer, gastritis Chest trauma Herpes zoster
Acute heart failure Bronchitis, pneumonia Stroke Pancreatitis Muscle injury/inflammation Anemia
Hypertensive emergencies Pleuritis Cholecystitis Costochondritis
Aortic valve stenosis Cervical spine pathologies
Tako-Tsubo cardiomyopathy
Coronary spasm
Cardiac trauma
Bold = Common and/or important differential diagnoses

aDilated, hypertrophic and restrictive cardiomyopathies may cause angina or chest discomfort


Coronary Angiography

Coronary angiography within 12 hours likely benefits high risk (elevated cardiac biomarkers at baseline or diabetes or a GRACE score more than 140) patients.

Recommendations for Anti-ischemic Drugs in the Acute Phase of Non-ST-elevation Acute Coronary Syndromes

Recommendations Class

of Recommendations


of Evidence

Early initiation of beta-blocker treatment is recommended

in patients with ongoing ischemic symptoms and without contraindications.

It is recommended to continue chronic beta-blocker therapy,

unless the patient is in Killip class III or higher.

Sublingual or i.v. nitrates are recommended to relieve angina;a intravenous treatment is recommended

in patients with recurrent angina, uncontrolled hypertension or signs of heart failure.

In patients with suspected/confirmed vasospastic angina, calcium channel blockers and

nitrates should be considered and beta-blockers avoided.

aShould not be administered in patients with recent intake of sildenafil or vardenafil (< 24 h) or tadalafil (< 48 h).


Primary Prevention

The primary prevention strategies include:

  • Dietary modifications:
  • Physical exercise
  • 30 minutes of moderate exercise

Secondary Prevention

The secondary prevention strategies include:


  1. Sukhova GK, Schönbeck U, Rabkin E, Schoen FJ, Poole AR, Billinghurst RC; et al. (1999). "Evidence for increased collagenolysis by interstitial collagenases-1 and -3 in vulnerable human atheromatous plaques". Circulation. 99 (19): 2503–9. PMID 10330380.
  2. Fuster V, Badimon L, Cohen M, Ambrose JA, Badimon JJ, Chesebro J (1988). "Insights into the pathogenesis of acute ischemic syndromes". Circulation. 77 (6): 1213–20. PMID 3286036.