L6.3 Drugs used to treat hypertension I

Question 1

What factors determine the preload and afterload

Answer 1

• Filling = Preload
• TPR = afterload

Question 2

Primary causes of hypertension

Answer 2

• Primary = No apparent cause (90-95%)
• Patients > 40
• Genetic
• Diet
• Obesity/Inactivity
• Psychological (stress/anxiety)

Question 3

Secondary causes of hypertension

Answer 3

• Secondary = identifiable cause (5-10%)
• Renal disease (↑RAS), renal artery stenosis
• Endocrine disorders (↑[A] from adrenal medulla tumour)
• Preeclampsia in pregnancy

Question 4

Laplace’s Law

Answer 4

• Wall tension (T) = Internal radius x transmural pressure
  
  • Transmural pressure = difference b/w distending force (from BV) & constricting force (from SM)
• Wall stress = T/wall thickness (W)
  
  • Thinner walls → ↑stress
  • Arteriole walls hypertrophy to compensate for ↑BP
    
    • Medial layer of SM is the one that hypertrophies (grows inwards)
  • Well adapted to withstand wall tension, but not transmural P

Question 5

What is the most important change affecting BV

Answer 5

• Circumferential changes (from S.M)
  
  • Basal level of vascular SM contraction
  • Arteriolar diameter determines resistance to local BF

Question 6

Reversibility of advance sclerotic plague

Answer 6

Irreversible

Question 7

Poiseuille’s law: Correlation of BP and flow

Answer 7

• Greatest ↓BP as blood traverses arterioles (main site of vascular resistance)
  
  • So capillaries won’t burst
• Poiseuille’s law = R directly proportional to 1/r^4
  
  • Vessels ↓R → ↑res

Question 8

Control of arteriolar diameter

Answer 8

• Local: NO, endothelin-1, PGI2
• SNS
• Blood: Catecholamine hormones (ANGII…)
• Passive: pressure

Question 9

Hypertensive treatment

Answer 9

• Goal <80mmHg DBP
• 1st choice therapy is lifestyle modifications
• Drugs: most are lifelong and have SE