PRE-UNIT STUDY TIPS

• The key to understanding heart diseases lies in its anatomy——how the heart functions. Once you understand how the heart works normally, it is very likely that you can figure out what’s going on in different diseases.
• Heart diseases often come with referred pain. For example, if a patient complains of abdominal pain, while considering gastrointestinal issues, you should also rule out potential cardiac conditions. Try to look for these clues in the practice questions.
• Make sure to understand the differences between angina and myocardial infarction, and the differences between cor pulmonale and pulmonary edema (what are the differences in their cause-and-effect relationships).
• For cardiac signal conduction, I recommend watching crash course videos for a more intuitive and understandable explanation.
• Congenital heart diseases are relatively complex. It helps by using anatomical diagrams of the affected heart to visualize how blood flows and what symptoms might result.

1. Coronary Artery Disease (CAD)

• narrowed by atherosclerotic deposits, causing temporary cardiac ischemia and eventually MI (or heart attack)

• signs & symptoms:

  • asymptomatic initially
  • first: pain of angina pectoris
  • advance:
    • burning, squeezing, crushing; radiating to the arm, neck, jaw
      • due to diminished blood flow and lower O2 saturation
    • Nausea, vomiting, and weakness

• etiology:

  • atherosclerosis: deposit of plaque (fat-containing substances) in the lumen
    • the arteries lose elasticity, resulting in cardiac ischemia
    • replacement scar tissue forms, resulting in heart failure

• risk factors:

  • 40+, men, postmenopausal women, Caucacians
  • smoking, residence in urban societies, presence of hypertension, diabetes, obesity
  • history of elevated serum cholesterol or reduced serum high-density lipoprotein (HDL) levels
  • lack of exercise, stress

• diagnosis:

  • ECG: ischemia, arrhythmias
  • treadmill testing, thallium or Cardiolite scan, CT, stress echo-cardiograms, cardiac catheterization, and angiograms: insufficient O2 supply
  • electron beam computerized testing (noninvasive): Ca buildup in arteries

• treatment:

  • vasodilators
  • angioplasty with a balloon or stenting
  • hypolipemic drug
  • first line drugs: angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), calcium channel blockers (CCBs), thiazide diuretics or vasodilators
    • beta-blockers and anticoagulants: prevent blood clots from breaking off & lodging in cerebral arteries
  • if severe & no respond: coronary artery bypass surgery
  • gene therapy: injection of DNA into cardiac muscle to stimulate new growth of blood vessels

  1.1 Angina Pectoris

  • chest pain due to ischemia: reduced O2 supply to myocardium

  • signs & symptoms:

    • onset of left-sided chest pain during or shortly after exertion
    • pain may radiate to the left arm or back

    

    • dyspnea
    • pain usually is relieved by ceasing the strenuous activity and placing nitroglycerin tablets sublingually or using nitroglycerin spray sublingually

  • etiology:

    • atherosclerosis
    • spasms of the coronary arteries
    • severe prolonged tachycardia, anemias, and respiratory disease

  • diagnosis:

    • ECG taken during the angina episode may show ischemia; a normal ECG does not preclude the diagnosis of angina
    • those described for CAD are performed

  • treatment:

    • cessation of the strenuous activity
    • placing nitroglycerin tablets sublingually
    • transdermal 经皮的 nitroglycerin

  1.2 Myocardial infarction (MI)

  • death of myocardial tissue caused by ischemia

  • signs & symptoms:

    • sudden severe substernal 胸骨下的 or left-sided chest pain
    • the pain may be crushing, causing a feeling of massive constriction of the chest, may be burning, or may just be a vague discomfort
    • the pain may be radiating to the left or right arm, back, jaw

    

    • the pain is not relieved by rest or the administration of nitroglycerin

    • irregular heartbeat, dyspnea; diaphoresis 发汗, nausea

    • patients usually exhibits denial & experiences severe anxiety, sometimes with the feeling of impending doom

    • MI occasionally is clinically silent, especially in diabetics.

      *Why does diabetes lead to heart disease?

      Type 2 diabetes, in particular, is closely associated with cardiovascular diseases. High blood sugar damages the walls of blood vessels, reducing their elasticity and potentially causing inflammation. Diabetic patients often have lipid metabolism disorders, leading to lipid accumulation on the inner walls of blood vessels, which can easily result in atherosclerosis.

      *Why are clinical symptoms often subtle?

      Diabetes is often accompanied by neuropathy. High blood sugar can interfere with the pain transmission system, causing reduced or absent pain perception. Additionally, diabetes can lead to microvascular disease, and when myocardial infarction occurs in microvessels, the symptoms may be subtle or not easily noticeable.

  • etiology: insufficient O2 supply caused by atherosclerotic plaque, thrombus, or myocardial muscle spasm

    • if ischemia is not reserved within about 6 hours, the cardiac muscle dies.
    • Coronary thrombosis is the most common cause of MI.

  • diagnosis: history, chest radiograph

    • ECG
      • changes in the P-R and QRS complexes and in the ST segment
    • lab test for cardiac enzyme levels (confirm)
      • creatine phosphokinase (CPK) and troponin: elevated in the 1st 6~24hr after MI
      • lactate dehydrogenase (LDH): peaks at 48 hours after MI
      • aspartate aminotransferase (AST): elevated
    • blood tests
      • altered isoenzyme levels (confirm)

  • treatment:

    • O2, morphine for pain
    • aspirin given ASAP: reduce the risk for additional damage to the heart and tissue by ischemia
    • nitroglycerin drip: vasodilation
    • Lidocaine or amiodarone are given by IV drip after a loading bolus: helps to ctrl arrhythmias
    • thrombolytic drugs such as tissue plasminogen activator (TPA), streptokinase, or alteplase (Activase) administered ASAP after dia
    • within the 6hr window: open the occulusion by angioplasty, thrombolytic drugs, or coronary artery bypass

  • prevention:

1. Cardiac Arrest

• sudden, unexpected cessation of cardiac activity
• signs & symptoms:
• etiology:
• diagnosis: