Acute Coronary Syndrome

Aka: Acute Coronary Syndrome, Myocardial Infarction

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II. Risk Factors

  1. See Cardiac Risk Factors

III. Epidemiology

  1. Prevalence of CAD in U.S.: 27.6 million (11.5%) in U.S. (2014)
  2. Mortality: 370,000 per year in U.S. (2014)
  3. Incidence of Acute MI: 735,000/year in U.S. (2014), 7 million/year worldwide
    1. STEMI accounts for 30% of cases (typically younger patients)
    2. NSTEMI accounts for 70% of cases (typically older patients)
    3. Steg (2002) Am J Cardiol 90(4): 358-63 [PubMed]
  4. No prior coronary symptoms in >50% with fatal acute MI
  5. Coronary deaths account for up to 20% of all deaths in U.S.
  6. Average age of first Myocardial Infarction in U.S.
    1. Men: 65 years old
    2. Women: 72 years old
  7. References
    1. https://www.cdc.gov/nchs/fastats/heart-disease.htm
    2. https://www.cdc.gov/heartdisease/facts.htm

IV. Pathophysiology: Atherosclerotic Plaque

  1. Form over 10-15 years in response to vascular injury
    1. Significant Plaque present in 75% of age >25 years
  2. Lipid core (atheroma)
    1. Injured endothelium attracts Macrophages
    2. Macrophages resorb LDL Cholesterol fatty streaks
    3. Lipids transform Macrophages into foam cells
  3. Surrounding wall (fibroatheroma)
    1. Surrounds lipid core
    2. Composed of fibroblasts and Smooth Muscle Cells
  4. Acute MI or Acute Coronary Syndrome
    1. Occurs on Plaque rupture; results in vessel Occlusion

V. Pathophysiology: Postinfarction remodeling

  1. Early Phase (<72 hours)
    1. Infarct zone expansion
    2. Myocardial wall thinning and ventricular dilation
    3. Increased elevated myocardial wall stress throughout Cardiac Cycle
    4. Renin-Angiotensin System activated (increased BNP)
  2. Late Phase (>72 hours)
    1. Left ventricle generalized effects and ventricular dilation over time resulting in distorted ventricular shape
    2. Mural hypertrophy occurs in response to ventricular load (decreases rate of dilation, preserves contractility)
    3. Fibrous tissue replaces necrotic Myocytes in the first 4 weeks after Myocardial Infarction
    4. Ventricular effects do not improve with revascularization
  3. References
    1. Sutton (2000) Circulation 101(25):2981-8 [PubMed]

VI. History: Present Illness

  1. See Chest Pain
  2. Chest Pain
    1. Use the term "Chest Discomfort" in place of "Chest Pain" when asking the patient about symptoms
      1. Many patients will deny Chest Pain, but admit to chest pressure, chest tightness or discomfort
    2. Chest Pain characteristics (sharp, dull, pressure, tightness, tearing)
    3. Onset
    4. Duration
    5. Location (e.g. substernal, left or right, upper or lower)
    6. Radiation (right arm, left arm, neck, jaw or back)
    7. Severity (at onset, at worst, and now)
      1. Perceived pain intensity does not always correlate with disease severity
    8. Palliative (e.g. rest, Nitroglycerin)
    9. Provocative (e.g. walking or other physical exertion, deep breathing, eating, torso movement, direct pressure)
  3. Shortness of Breath
    1. Shortness of Breath on exertion
    2. Shortness of Breath at rest
    3. Orthopnea
  4. Nausea or Vomiting
  5. Near Syncope or Light Headedness
  6. Other Associated Symptoms
    1. Abdominal Pain
    2. Back pain
    3. Black stools (Melana) or Vomiting blood

VII. History: Past History

  1. See Chest Pain
  2. Coronary Artery Disease (prior PTCA or CABG?)
  3. Peripheral Arterial Disease
  4. Prior abnormal stress test
  5. Diabetes Mellitus
  6. Other risk factors
    1. See Coronary Artery Disease Risk Factors
    2. Hypertension
    3. Hyperlipidemia
    4. Tobacco Abuse
    5. Premature heart disease Family History (age <55 in father or brother, age <65 in mother or sister)

VIII. Symptoms

  1. See TIMI Risk Score
  2. See HEART Score
  3. See Angina Diagnosis
    1. Reviews the likelihood that Chest Pain is due to cardiovascular cause
    2. ACS is asymptomatic in 25% of Myocardial Infarctions
    3. Elderly, women and patients with diabetes may present atypically (see Chest Pain, as well as below)
      1. Dyspnea or vague Abdominal Pain may be the chief complaint
  4. Findings that most increase the likelihood of Acute Coronary Syndrome
    1. See Chest Pain
    2. Crushing, substernal Chest Pain
    3. Chest Pain radiation to the right chest or bilateral arms (or Shoulders)
    4. Exertional Chest Pain
    5. Chest Pain with diaphoresis
    6. Chest Pain associated with Vomiting (not only Nausea)
  5. Chest Pain due to Myocardial Infarction is similar to Angina
    1. Deep, poorly localized chest ache
      1. Worse with activity
      2. Better with rest and Nitroglycerin
    2. Radiation
      1. Arm, Shoulder, hand or upper back
      2. Radiation to right arm or bilateral arms is more suggestive of coronary syndrome
      3. May also radiate to neck, jaw or throat (less specific)
  6. Distinguishing features of Chest Pain due to Myocardial Infarction
    1. More intense Chest Pain than Angina (e.g. "Crushing" Chest Pain)
    2. More persistent than Angina (>30 minutes)
    3. Not fully relieved by palliative measures
      1. Rest
      2. Nitroglycerin (3 consecutive doses)
    4. Accompanied by systemic symptoms
      1. Vomiting
      2. Diaphoresis
      3. Apprehension
  7. Elderly Presentations of Acute Coronary Syndrome
    1. Most common presentations
      1. Dyspnea
      2. Syncope
      3. Generalized weakness
    2. Chest Pain is presenting symptom in only 24% of Acute Coronary Syndrome (ACS) age >75 years
      1. Contrast with 48% of younger adults who present with Chest Pain in ACS
    3. References
      1. Brieger (2004) Chest 126(2): 461-9 [PubMed]

IX. Signs

  1. Pallor
  2. Diaphoresis
  3. Tachycardia
  4. Signs of Congestive Heart Failure may also be present (higher risk findings)
    1. Rales on Lung Examination
    2. S3 Gallup Rhythm
    3. Jugular Venous Distention (esp. Right Ventricular Infarction)

X. Differential Diagnosis

  1. See Chest Pain
  2. Critical acute diagnoses
    1. Aortic Dissection
    2. Pulmonary Embolism
    3. Tension Pneumothorax
    4. Esophageal Rupture
  3. Other important causes
    1. Congestive Heart Failure
    2. Pneumonia
    3. Pericarditis
    4. Cholecystitis
    5. Pancreatitis
    6. Peptic Ulcer Disease
  4. Diagnoses of exclusion
    1. Gastroesophageal Reflux disease
    2. Chest Wall Pain (e.g. Costochondritis)
    3. Anxiety Disorder

XI. Diagnosis

  1. Serum Cardiac Markers
    1. Serial Troponin
  2. Electrocardiogram
    1. See Electrocardiogram in Myocardial Infarction
    2. See Immediate Myocardial Infarction Management
    3. Goal first EKG On ED arrival within 10 minutes
      1. Repeat EKG based on patient symptoms and other findings
      2. Dynamic EKG changes are common with serial EKGs in Acute Coronary Syndrome
    4. Evaluate Electrocardiogram carefully
      1. Ischemic changes (e.g. ST segment Depression or T Wave Inversion) are commonly missed
      2. Hyperacute T Waves (Peaked T Waves) precede ST Elevation
  3. Echocardiogram
    1. See Echocardiogram in Myocardial Infarction

XII. Types

  1. Type 1
    1. Myocardial Infarction with Plaque rupture or erosion with thrombus formation (classic)
  2. Type 2
    1. Myocardial Infarction with imbalance between oxygen supply and oxygen demand WITHOUT Plaque rupture
    2. Examples
      1. Vasospasm or endothelial dysfunction
      2. Fixed atherosclerosis with increased demand
      3. Marked increased in demand (e.g. Significant Arrhythmia, Severe Anemia)
  3. Type 3
    1. Sudden Cardiac Death before Troponins have time to rise (postmortem diagnosis)
  4. Type 4 and 5
    1. Cardiac procedure (e.g. PCI, ) related Troponin elevation
  5. References
    1. Thygesen (2018) Circulation 138(2):e618-51 +PMID:30571511 [PubMed]

XIII. Management

  1. See Immediate Myocardial Infarction Management
  2. See Goldman Criteria for ICU Chest Pain Admission
  3. Myocardial Infarction Stabilization
  4. Cardiac Rehabilitation

XIV. Complications

  1. Arrhythmia
    1. See Arrhythmia Following Myocardial Infarction
    2. Ventricular Tachycardia
    3. Ventricular Fibrillation
    4. Accelerated Idioventricular Rhythm
    5. Bradyarrhythmia
    6. Atrioventricular Block
  2. Congestive Heart Failure
  3. Cardiogenic Shock
  4. Acute Mechanical Complications
    1. Ventricular Septal Rupture or Ventricular Wall Rupture
    2. Acute Mitral Regurgitation (<0.5% of cases)
      1. Results from acute papillary Muscle rupture (typically within the first week of MI)
      2. May progress to Cardiogenic Shock and Acute Pulmonary Edema with 5% mortality rate
      3. Emergent cardiothoracic surgery Consultation for mitral valve repair is indicated
      4. Hamid (2022) Ann Cardiothorac Surg 11(3):281-9 +PMID: 35733722 [PubMed]
  5. Dressler's Syndrome
  6. Post-MI Pericarditis
  7. Ventricular aneurysm
  8. Recurrent Angina
  9. Recurrent Acute Coronary Syndrome (20% within 4 years)
  10. References
    1. Damluji (2021) Circulation 144(2):e16-e35 +PMID: 34126755 [PubMed]

XV. References

  1. Mattu in Swadron (2022) EM:Rap 22(5): 13-5
  2. Barstow (2017) Am Fam Physician 95(3): 170-77 [PubMed]
  3. Switaj (2017) Am Fam Physician 95(4): 232-40 [PubMed]
  4. Nohria (2024) Am Fam Physician 109(1): 34-42 [PubMed]

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