Cardiothoracic Surgery: Acute Coronary Syndrome (ACS)

Definitions

Definitions

  • Acute Coronary Syndrome (ACS) – A Constellation of Clinical Symptoms Consistent with Acute Myocardial Ischemia
    • Includes Myocardial Infarction (MI) & Unstable Angina (UA)
  • Coronary Artery Disease (CAD) – Diseased/Damaged Coronary Blood Vessels
  • Angina Pectoris – Severe Chest Pain Due to Inadequate Heart Blood Supply
  • Myocardial Infarction (MI/Heart Attack) – Death of Myocardium Cells Due to Obstruction of Blood Flow

Types of Angina Pectoris

  • Stable Angina – Brief Episodes Associated with Exercise or Stress & Relieved with Rest
  • Unstable Angina (UA)
    • Prolonged Angina at Rest (> 20 Minutes)
    • New-Onset Severe Angina
    • Worsening Angina (More Frequent, Severe or Longer Duration)
  • Variant/Prinzmetal Angina – Angina Due to Coronary Artery Spasm

Types of Myocardial Infarction (MI)

  • ST-Segment Elevation Myocardial Infarction (STEMI) – MI Associated with ST-Segment Elevation
    • Indicates a Full-Thickness Injury
  • Non-ST-Segment Elevation Myocardial Infarction (NSTEMI) – MI Not Associated with ST-Segment Elevation
    • Indicates a Subendocardial (Not Full-Thickness) Injury
    • Type 1 NSTEMI – Spontaneous from Atherothrombotic Plaque Rupture or Erosion
    • Type 2 NSTEMI – Due to Oxygen Supply-Demand Imbalance
    • Type 3 NSTEMI – Cardiac Death without Biomarker Samples or Detected at Autopsy
    • Type 4 NSTEMI – Associated with Revascularization Procedures
      • 4a: Related to Percutaneous Coronary Intervention (PCI) within 48 Hours
      • 4b: Related to Stent Thrombosis
      • 4c: Restenosis After Percutaneous Coronary Intervention (PCI)
    • Type 5 NSTEMI – Related to CABG Procedure within 48 Hours

Acute Coronary Syndrome (ACS)

Basics

  • Coronary Artery Disease is the Most Common Cause of Death in the United States
  • 95% of Myocardial Ischemia is Due to Underlying Atherosclerotic CAD
  • Most Atherosclerosis is Proximal
  • Risk Factors for Increased Mortality:
    • Cardiogenic Shock – Strongest Risk Factor
    • Emergency Setting
    • Increased Age
    • Low Ejection Fraction

Presentation

  • Chest Pain/Discomfort – Most Common Symptom
    • Classic Description: Substernal Chest Tightness/Pressure with Radiation to Left Arm or Jaw
  • Shortness of Breath
  • Diaphoresis
  • Weakness
  • Anxiety

Complications of Myocardial Infarction (MI)

  • Reinfarction
    • Occurs Within 48 Hours
  • Postinfarct Angina
  • Mechanical Complications:
    • Interventricular Septum Rupture
    • Left Ventricular Free Wall Rupture
    • Papillary Muscle Rupture
  • Conduction Abnormality
  • Left Ventricular Aneurysm
  • Post-Cardiac Injury Syndrome (PCIS)
    • Also Known As:
      • Dressler’s Syndrome
      • Post-Pericardiotomy Syndrome
      • Post-Myocardial Infarction Syndrome
    • Definition: Pericarditis from Injury to the Pericardium
    • Develops Weeks-Months After Myocardial Infarction (MI)
    • Presentation:
      • Pericardial Friction Rub
      • Fever
      • Pleuritic Chest Pain
      • Shortness of Breath
      • Can Cause Pericardial Effusion
    • EKG Findings: Diffuse ST-Segment Elevation
    • Treatment: NSAIDs, Colchicine & Steroids

Diagnosis

Diagnosis of Myocardial Infarction (MI)

  • Elevated Troponin with ≥ One Of:
    • Symptoms of Myocardial Ischemia
    • New Ischemic Changes on EKG
    • Development of Pathologic Q Waves
    • New Loss of Viable Myocardium or Regional Wall Motion Abnormality Consistent with Ischemic Etiology on Imaging
    • Identification of a Coronary Thrombus by Angiography or Autopsy
  • Coronary Angiogram is the Standard Tool for Describing Surgical Anatomy of CAD

Differentiation

  • STEMI: Elevated Troponin with ST-Elevation on EKG
  • NSTEMI: Elevated Troponin without ST-Elevation on EKG
  • UA: Normal Troponin

EKG Changes

  • ST-Segment Changes (Elevation or Depression)
  • Left Bundle Branch Block (LBBB)
  • T Wave Inversion
  • Q Waves
  • Lead Laterality:
    • Anterior: V1-V4 (Indicates Left Anterior Descending (LAD) Artery Disease)
    • Posterior: V1 & V2 (Indicates Right Coronary Artery or Left Circumflex Artery Disease)
    • Lateral: I & aVL (Indicates Left Circumflex Artery Disease)
    • Inferior: II, III & aVF (Indicates Right Coronary Artery Disease)

Cardiac Enzymes

  • Troponin I
    • Best Test for Detecting Acute MI
    • Highest Sensitivity & Specificity
    • Remains Elevated for 5-14 Days
    • Generally Trended Every 3-6 Hours
  • Creatine Kinase-MB (CK-MB)
    • Remains Elevated for 2-3 Days
    • Best for Detecting Recurrence

Treatment

Treatment

  • Medical Managements:
    • Oxygen Supplementation
    • Antiplatelet Therapy (Aspirin or Clopidogrel (Plavix))
      • Other NSAIDs Should Be Discontinued – Increased Risk of Cardiovascular Events
    • Beta Blockers
      • Contraindicated in Heart Failure, Heart Block or Cardiogenic Shock
    • Statin Therapy
    • Sublingual Nitroglycerin – Vasodilation to Relieve Chest Pain
      • Contraindicated in Hypotension or Cardiogenic Shock
    • Consider Morphine for Persistent Severe Pain
  • Reperfusion
    • Fibrinolysis
    • Percutaneous Coronary Intervention (PCI) – Goal Door-to-Balloon Time < 90 Minutes
    • Coronary Artery Bypass Graft (CABG)

Cardiogenic Shock

Coronary Artery Bypass Graft (CABG) Indications

  • Left Main Disease > 50% Stenosis
  • Triple-Vessel Disease > 70% Stenosis (Right Coronary Artery, Left Anterior Descending Artery & Circumflex Artery)
  • Double-Vessel Disease with Proximal Left Anterior Descending (LAD) Artery Disease
  • At Least One Vessel with Significant (> 70%) Stenosis with Unacceptable Angina Despite Medical Therapy
    • May Also Consider Percutaneous Coronary Intervention (PCI)
  • Survivors of Sudden Cardiac Death with Ischemia-Mediated Ventricular Tachycardia
  • Emergency CABG:
    • After Failed Percutaneous Coronary Intervention (PCI) with Ongoing Ischemia or Threatened Occlusion of Substantial Myocardium
    • Cardiogenic Shock Due to Myocardial Infarction (MI)
  • Undergoing Noncoronary Cardiac Surgery with Left Main Disease (> 50%) or Any Other CAD (> 70%)

Percutaneous Coronary Intervention (PCI)

  • Radial Access Generally Preferred Over Femoral Access (Decreased Risk of Bleeding Complications)
  • Stents:
    • Drug-Eluting Stents (DES) – Generally Preferred
      • Decreased Risk of Restenosis
    • Bare Metal Stent (BMS)
  • Dual Antiplatelet Therapy (DAPT)
    • Agents: Aspirin & Clopidogrel (Plavix)
    • Duration of Therapy:
      • Drug-Eluting Stents (DES) – One Year
      • Bare Metal Stent (BMS) – One Month