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

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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

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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

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  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

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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

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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.

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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)

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  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.

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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)

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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

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13

What can the main consequences of HTN lead to?

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  • 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)

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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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