SPR L13 Pathophysiology of Hypertension Flashcards Preview

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Flashcards in SPR L13 Pathophysiology of Hypertension Deck (15):
1

Pathophysiology of Hypertension

What will be covered...

(for general perusal)

•Definition and causes of hypertension

•Pathophysiology of hypertension

•Symptoms and signs

•Principles of drug management of hypertension

2

  1. Define Hypertension
  2. What is the definition of 'normal' related to?

  1. >140 mmHg systolic and/or >90 mmHg diastolic (20-30% adult population)

  2. BP follows a classical ‘bell-shaped’ distribution, based on epidemiological evidence

3

What is blood pressure equal to?

 

What can lead to a high BP?

Cardiac Output X Total Peripheral Resistance

Raised CO or TPR or both

4

Primary Hypertension - 'Essential HTN'

What are the causal factors?

 

Multifactorial : Cause unknown in 80-90% cases

  • Genetic
  • Fetal factors (low birth weight)
  • Environmental factors
    • Obesity
    • Excess alcohol
    • Excess Na+ intake
  • Associated with diabetes (“insulin resistance”)

5

 Pathogenesis of Primary Hypertension

  1. Describe CO in primary HTN?
  2. Describe why Peripheral Resistance is elevated?
  3. Discuss the causes vs. consequences

  1. Normal
  2. decreased lumen diameter by resistance in arteries/arterioles, increased thickness of walls of 'resistance' vessels (sclerosis)
  3. Eg. the relationshop to Na+ uptake - increased Na+ gives increased ECF/BV and therefore increased CO
    1. Baroreceptor adaptation

6

Secondary Hypertension

What are the causes?

  • Renal disease
  • Endocrine diseases
    • Primary hyperaldosteronism (Conn’s syndrome)
    • Phaeochromocytoma
    • Cushing’s syndrome
  • Coarctation of the aorta
  • Pregnancy
  • Drugs

7

Decribe the Pathogenesis of Secondary Hypertension in the following causes...

Renal disease

 

  • Decreased glomerular function leads to fluid retention, increased BP and therefore CO 
  • Increased renin/angiotensin/aldosterone - increased TPR and therefore BP.

8

Decribe the Pathogenesis of Secondary Hypertension in the following causes...

Endocrine Disease

  1. Primary hyperaldosteronism (Conn's Syndrome)
  2. Phaeochromocytoma
  3. Cushing's Sydrome (Excess Glucocorticoid)

  1. Increased renal fluid absorption in DCT = increased BP and CO
  2. Increased Catcholamines = vasocontriction (increased TPR) and cardiac stimulation (increased CO)
  3. Increased renal fluid absorption in DCT, increaed BV and CO.

9

Decribe the Pathogenesis of Secondary Hypertension in the following causes...

Coarctation of the Aorta

Increased Resistance

  • Increased BP proximal to stricture
  • Decreased BP/perfusion distal to stricture (early)
  • renally mediated general HTN (renin/angiotensin/aldosterone)

10

Decribe the Pathogenesis of Secondary Hypertension in the following causes...

Pregnancy 

  • Increased CO + greatly decreased PR = decreased BP (usually)
  • Increased BP may be a risk to the mother (cause unclear)

11

Decribe the Pathogenesis of Secondary Hypertension in the following causes...

Drugs

Various mechanisms

12

Pathophysiology: consequences of hypertension

Outline some of the main consequences of HTN

  • Left ventricular hypertrophy/cardiac failure
    • Clinical examination, Chest X-ray and ECG
  • Arterial wall thickening and reduced vascular compliance

    • Increased pulse wave velocity

  • Atheroma

13

What can the main consequences of HTN lead to?

  • Endothelial dysfunction
    • Reduced dilators (NO/prostacyclins)
    • Increased constrictors (endothelins)
    • Increased risk atheroma/thrombosis
  • Renal damage (nephropathy)
    • Reduced perfusion/filtration
    • Positive feedback via renin/angiotensin/aldosterone
    • Further increase in BP
  • Cerebral vascular disease
    • Dementia
    • TIA
    • Stroke
  • Hypertensive retinopathy
    • Thickening arterial walls
    • Haemorrhages
    • ‘Soft’ exudates (infarcts)

14

What are the signs and symptoms of hypertension?

  • Headache/nosebleed (epistaxis)
  • Elevated BP
  • Hypertensive retinopathy
  • Symptoms signs of complications
    • Cardiac
    • Renal
    • Cerebrovascular
    • Coronary vascular disease
    • Peripheral vascular disease

15

What are the prinicples of Drug Management of hypertension?

Reduce Cardiac Output

  • Thiazide diuretics - reduce CO initially only, reduce PR long term

  • b-adrenoceptor blockers - reduced cardiac sympathetic stimulation

The following give reduced aldosterone production and also reduce vasoconstriction by angiotensin

  • ACE inhibitors
  • AII receptor blockers
  • Renin inhibitors

Reduce Peripheral Resistance

  • L-type Ca 2+ channel blockers - also reduces cardiac contractility
  • a1-adrenoceptor blockers

  • Other vasodilators, eg hydralazine, minoxidil

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