Ischemic Heart Disease

Question 1

Ischemic Heart Disease

Answer 1

Group of four syndromes related to myocardial ischemia usually due to atherosclerosis of the coronary arteries

Question 2

Stable Angina

Answer 2

• Chest pain that is reversible
  
  • does not arise at rest
  • arises with exertion or emotional stress
  • radiates to the L arm or jaw
  • lasts < 20 minutes
  • accompanied by diaphoresis and SOB
  • relieved by rest or nitroglycerin
• Due to atherosclerosis of coronary aa. with greater than 70% stenosis (if less than, patients are relatively asymptomatic)
• Represents reversible injury to the myocytes
  
  • hallmark of reversible injury = cellular swelling
• ​EKG findings:
  
  • ST segment depression (hallmark of subendocardial ischemia)

Question 3

Unstable Angina

Answer 3

• Chest pain that occurs at rest
  
  • relieved by nitroglycerin
• Due to rupture of atherosclerotic plaque with thrombosis and incomplete occlusion of a coronary artery
• Represents reversible injury to myocytes
• EKG findings:
  
  • ST segment depression (again, subendocardial ischemia)
• High risk of progression to MI
  
  • very easy for thrombus to grow and eventually occlude the entire vessel

Question 4

Prinzmetal Angina

Answer 4

• Due to coronary a. vasospasm (vasoconstriction)
• Leads to episodic chest pain unrelated to exertion
  
  • relieved by nitroglycerin or calcium channel blockers
• Represents reversible injury to the myocytes
• EKG findings:
  
  • ST segment elevation due to transmural ischemia [since coronary a. clamps down, none of the layers of heart (epi-, myo-, or endocardium) receive blood flow from the artery]

Question 5

Myocardial Infarction

Answer 5

• Necrosis of cardiac myocytes
• Due to rupture of atherosclerotic plaque with thrombosis and complete occlusion of a coronary artery for >20 minutes
• Other causes include coronary a. vasospasm, embolis, or vasculitis.
• CP:
  
  • Severe, crushing chest pain for >20 minutes that radiates to the left arm or jaw
  • Diaphoresis
  • Dyspnea (b/c the heart is not pumping as well → pulmonary congestion and edema)
  • Symptoms are not relieved by nitroglycerin
• Treatment:
  
  • Aspirin or heparin to limit additional thrombosis
  • Supplemental O2 for the ischemia
  • Nitrates → venodilation → ⇣preload
  • Beta blockers → slow the heart rate → ⇣demand for oxygen and risk for arrhythmia
  • ACE inhibitor

Question 6

Phases of MI

Answer 6

• Initial Phase = subendocardial necrosis involving <50% of myocardial thickeness
• EKG shows ST segment depression
• Cardiac enzyme tests:
  
  • Troponin I most sensitive and specific marker
    
    • rises 2-4 hours after infarction
    • peaks at 24 hours
    • normal again within 7-10 days
  • CK-MB
    
    • Useful for detecting reinfarction days after MI
    • rises 4-6 hours after
    • peaks at 24 hours
    • normal again by 72 hours