VPH 300 Cardiovascular system

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Name the 4 groups of positive inotropic drugs and name an example of each.

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1

Name the 4 groups of positive inotropic drugs and name an example of each.

Cardiac glycosides (i.e. Digoxin) Methylxanthines (i.e. Theophylline) Catecholamines (i.e. Adrenaline) Inodilators (i.e. Pimobendan)

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2

Name the 3 types of vasodilators.

  1. Afterload reducers (arteriodilators)

  2. Preload reducers (venodilators)

  3. Dual effect (preload & after load reducers)

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3

Vasodilators reduce what in the treatment of CHF?

Cardiac load

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4

Name the 3 types of dual effect vasodilators and an example of each.

Alpha blockers (i.e. Prasozin) Angiotensin-converting enzyme (ACE) inhibitors (i.e. Benazepril) Calcium-channel blocking drugs (i.e. Amlodipine/Diltiazem)

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5

Example of an afterload reducer vasodilator?

Hydralazine

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6

Example of an preload reducer vasodilator?

Nitrates (nitroglycerine)

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7

How do afterload reducers help treat congestive heart failure (MOA)?

Reduce blood flow impedance (i.e. aortic flow & pressure) Increase forward stroke volume Decrease myocardial O2 demand Decrease regurgitant flow in i.e. mitral valve insufficiency

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8

What vasodilator drug decreases regurgitant flow caused by valvular insufficiencies to treat CHF?

Afterload reducers, i.e. hydralazine

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9

How do preload reducers help treat congestive heart failure (MOA)?

Dilate systemic veins ā†’ reduce venous return ā†’ reduce LV filling pressure ā†’ reduce preload

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10

Name 4 catecholamines which are used in the treatment of hypotension.

Adrenaline Isoproterenol Dopamine Dobutamine

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11

Administration of catecholamines in the treatment of hypotension?

I/V (due to short half-life) Single bolus/continuous infusion

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12

T/F: Dobutamine is used in the treatment of hypotension in shock AND improving renal perfusion in renal failure.

False, dopamine (dobutamine has no effect on kidney)

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13

Catecholamines: side effects?

Arrthymogenic esp. in conditions of hypoxia or acidosis

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14

Catecholamines should not be administered with what general anaesthetic agent and why?

Halothane (sensitises the heart to catecholamines)

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15

Catecholamine administration is contra-indicated if what other positive inotropic drug is currently prescribed to a patient?

Cardiac glycosides

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16

What are the 2 most important vasodilator drugs used in the treatment of cardiac failure and other forms of cardiac insufficiency?

ACE inhibitors (i.e. Benazepril) Ca-channel blockers (i.e. Amlodipine, diltiazem)

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17

Define inodilator.

Agent with inotropic effects that also causes vasodilation, leadings to decreased systemic and/or pulmonary vascular resistance (INOTROPY + VASODILATION)

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18

Give an example of an inodilator.

Pimobendan

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19

Pimobendan: MOA?

Positive inotrope via Ca sensitisation of cardiac muscle (via inhibition of phosphodiesterase III and increase sensitivity to intracellular Ca)

  • Peripheral vasodilator (arterial & venous)

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20

Pimobendan: Clinical indications?

  1. Dog with CHF (dilated cardiomyopathy/DCM)

  2. Dog with chronic mitral valve insufficiency

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21

T/F: Greater survival times are observed in CHF dogs treated with ACE inhibitors and furosemide vs. those of dogs treated with pimobendan.

FALSE, greater survival times seen with treatment with pimobendan

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22

ACE inhibitors: list the different classes and drugs in each.

Class 1: Captopril Class 2: Enalapril / Benazepril Class 3: Lisinopril

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23

Explain how heart failure stimulates the RAA axis and results in the production of angiotensin II.

Heart failure: decreased renal perfusion ā†’ renin release Renin acts on angiotensinogen ā†’ angiotensin I ACE (angiotensin-converting enzyme) acts on angiotensin I ā†’ angiotensin II

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24

Effects of angiotensin II?

Potent vasoconstrictor Aldosterone release (Na reabsorption, water retention) ADH release (water reabsorption in collecting ducts)

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25

How does high angiotensin II increase preload?

Fluid retention and reabsorption due to ADH & aldosterone

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26

How does high angiotensin II increase afterload?

Vasoconstrictor effects

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27

How do ACE inhibitors decrease afterload and preload to treat CHF?

Reduce angiotensin II concentrations

  • Vasodilation = decrease afterload

  • Diuresis (less ADH, aldosterone) = decrease fluid retention = decrease preload

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28

Anti-hypertensive effects of ACE inhibitors are potentiated by what?

Low-Na diet

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29

ACE inhibitors: MOA?

Heart failure: ā†“ renal perfusion, āˆ“ renin release Angiotensin I + ACE ā†’ angiotensin II

  • Potent vasoconstrictor

  • Aldosterone release: Na reabsorption & water retention

  • ADH release: Water reabsorption in collecting ducts

ACE inhibitors: reduce amount of angiotensin II āˆ“ Vasodilation ā†’ decrease bp/afterload āˆ“ Diuresis ā†’ decrease fluid retention/preload

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30

ACE inhibitors: Clinical uses?

Congestive heart failure

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31

ACE inhibitors are usually administered concurrently with which other 2 drugs in the treatment of CHF?

Furosemide Diuretics

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32

ACE inhibitors: side effects?

Hypotension Azotemia Increased risk of hyperkalaemia Increased risk of kidney failure (if pre-existing renal disease)

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33

Calcium channel blockers: MOA?

Suppresses Ca2+ influx through plasma membrane channels in cardiac tissues/vascular smooth muscle āˆ“ Decrease intracellular Ca2+ concentrations = Decreased contractility = Vasodilation = Lower myocardial O2 demand = Slow AV demand = Lower impedance to LV ejection

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34

Name the 2 most commonly used calcium channel blocker drugs?

Amlodipine Diltiazem

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35

Calcium channel blockers: Clinical indications?

Diltiazem: hypertrophic cardiomyopathy in cats

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36

What drug is used to specifically treat hypertrophic cardiomyopathy in cats?

Diltiazem (Ca-channel blocker)

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37

Example of anti-arrhythmic drug in Class IA?

Quinidine

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38

Example of anti-arrhythmic drug in Class IB?

Lignocaine

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39

Class I of anti-arrhythmic drugs: MOA?

Blocks fast inward sodium currents of myocardial cells IA: Quinidine IB: Lignocaine

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40

Class II of anti-arrhythmic drugs: MOA? Example?

Block Ī²-adrenoreceptors i.e. Propanolol

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41

Class III of anti-arrhythmic drugs: MOA? Example?

Block K channel = prolong repol and extend refractor periods i.e. Amiodarone

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42

Class IV of anti-arrhythmic drugs: MOA? Example?

Block Ca channel i.e. Amlodipine, diltiazem

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43

Quinidine is used to treat what in horses?

Atrial fibrillation

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44

Treatment procedure of using quinidine in horses to treat atrial fibrillation?

Test dose: 20 mg/kg dissolved in water by stomach tube (to test sensitivity to SE) Starting next day: 20 mg/kg dissolved in water every 2 hrs until rhythm returns to sinus rhythm Once arrthymia stops: Continue treatment for 2-3 days at 20 mg/kg twice daily DO ECG BEFORE EACH ADMINISTRATION TO SEE IF SINUS RHYTHM PRESENT

  • Oral dose safer

  • Urgent treatment? Can give I/V as infusion + I/V fluids simultaneously to overcome hypotensive effects

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