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Pharmacology > Cardiac pharmacology > Flashcards

Cardiac pharmacology Flashcards

1
Q

List five causes of heart failure

A
  • sustained pressure overload
  • sustained volume overload
  • depressed or altered contractility, or loss of, myofibres
  • reduced ventricular compliance (diastolic dysfunction)
  • abnormal heart rate or rhythm
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2
Q

List three primary causes of reduction of myocardial contractility

A
  • dilated cardiomyopathy
  • taurine deficiency
  • chronic myocarditis (rare)
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3
Q

List two causes of pressure overload in the heart

A
  • sub/aortic or pulmonary stenosis
  • pulmonary hypertension
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4
Q

List four causes of volume overloading

A
  • chronic degenerative valve disease
  • mitral or tricuspid dysplasia
  • aortic or pulmonary insufficiency
  • congenital L>R shunts (e.g. patent ductus arteriosis, ventricular septal defects)
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5
Q

List two causes of diastolic mechanical inhibition

A

Pericardial disorders (pericarditis, neoplasia)

Ventricular myocardial disorders (feline hypertrophic and restrictive cardiomyopathies)

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6
Q

List a cause of dysrhythimia

A

Altered electrical function

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7
Q

Which ions are important in cardiac muscle contraction?

A

Ca++, Na+, K+

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8
Q

List two endogenous compensatory mechanism in congestive heart failure

A

Intrinsic cardiac compensatory mechanisms

Systemic compensatory mechanisms

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9
Q

What are the issues with the compensatory mechanisms in congestive heart failure?

A

Compensatory mechanisms are temporary and aimed at increasing O2 to meet metabolic demands

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10
Q

List two intrinsic compensatory mechanisms for CHF

A

hypertrophy

dilation

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11
Q

List two systemic compensatory mechanisms for response to inadequate cardiac function

A
  • activation of sympathetic nervous system (+ inotrope and chronotrope: increased HR, contractility, vasoconstriction, BP)
  • Activation of RAAS system
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12
Q

What is the effect of the sympathetic response on alpha 1 receptors on the blood vessels

A

Constriction of smooth muscle (espeically at periphery): increased BP

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13
Q

What is the effect of sympathetic stimulation on Beta2 receptors in blood vessels?

A

Dilation of smooth muscle (especially skeletal muscle): decreased BP

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14
Q

What is the effect of adrenaline on blood vessels?

A

Alpha and Beta agonist: combination of vasodilation (sk. m) and vasoconstriction (periphery)

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15
Q

What is the effect of noradrenaline on blood vessels?

A

Predominantly alpha agonist: vasoconstriction (esp periphery), increased systolic and diastolic BP, reflex bradycardia (decreased HR)

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16
Q

What is the effect of isoprenaline on the cardiac system?

A

Predominately Beta agonist: vasodilation, increased cardiac force and rate, fall in mean arterial pressure

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17
Q

Briefly describe the RAAS system

A

Liver: releases angiotensinogen
Kidney: releases renin
Renin: angiotensinogen -> angiotensin 1
Lung: releases angtiotensin-converting enzyme (ACE)
ACE: angiotensin 1 -> angiotensin 2
Angitotensin 2: Increases release of aldosterone from adrenal cortex

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18
Q

What are the functions of angiotensin II?

A

+ vasopressin: + reabsorption by kidney tubules

+ thirst: increased fluid intake

+ arteriolar vasoconstriction

+ aldosterone: + Na+ reabsorption by kidney tubules

= conservation of Na+, H20
overall - NaCl, ECF fluid volume, arterial blood pressure

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19
Q

What are four main treatment principles in cardiac disease?

A
  1. Reduce excessive compensatory mechanisms
  2. Promote perfusion of tissue
  3. Control ECF volume (- oedema)
  4. Correct any arrhythmias
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20
Q

Name 5 general methods that might be considered in combination for treating CHF

A
  • diuretics
  • vasodilators
  • digoxin
  • beta blockers
  • dietary modification (-salt, -obesity)
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21
Q

What is the overall outcome of using diuretics?

A

decrease Na retention

increase water loss

= reduce preload

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22
Q

What are the three main clases of diuretic used in CHF?

A

Loop

Thiazides

Potassium sparing

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23
Q

Name a loop diuretic

A

Frusemide (or furosemide)

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24
Q

What is the mechanism of action of frusemide (furosemide)

A

Inhibit Na, Cl, K reabsoprtion in thick ascending loop

Increase PGE2 = vasodilation

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25
Q

What is an alternative use of furosemide besides as a loop diuretic?

A

Bronchidlator in humans, horses, guinea pigs

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26
Q

What are some considerations when using furosemide?

A

Blocked by NSAIDs

Beware otoxicty and digitalis

May result in hypokalaemia, hyponatremia, dehydration > can affect heart function

Use minimal dose to relieve clinical signs

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27
Q

What are the indications for use of furosemide?

A

Acute heart failure with pulmonary oedema

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28
Q

What are the indications for thiazide diuretics?

A

Resistance developed to loop diuretics (‘rescue dieuretic)

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29
Q

What is the mechanism of action for thiazide diuretics

A

Prevent reabsorption of Na, Cl, K

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30
Q

Name three thiazide diuretics

A

Chlorothizide, hydrochlorthiazide, spironolactone

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31
Q

Name two potassium sparing diuretics

A

Triamterene, amiloride

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32
Q

What is the mechanism of action of triamterene, amiloride?

A

Inhibits reabsorption of Na and Cl in distal tubular cells and collecting duts by inhibiting Na/K ATPase pump

(Spares K+)

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33
Q

What are the indications of using traimeterene, amiloride?

A

Weak efficacy, so used in conjunction with loop diuretics or thiazides in CHF.

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34
Q

What is the mechanism of action of spironolactone?

A

Aldosterone antagonist + weak Ca++ channel blocker

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35
Q

What is the purpose of using vasodilators in CHF?

A

To reduce pre and/or afterload

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36
Q

Name three arterial dilators

A

Hydralazine

Amlodipine

Nitroglycerin

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37
Q

Name four balanced dilators

A

Prazosin

Enalapril, Benazepril (ACE inhibitors

Nitroprusside

Pimobendan

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38
Q

Name one venodilator

A

Nitroglycerine

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39
Q

What are two potential problems with the overuse of vasodilators in CHF therapy?

A

Hypotension

Reflex tachycardia

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40
Q

Name two ACE inhibitors

A

Enalapril, enazepril

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41
Q

What is the mechanism of action of enalapril, benazepril?

A

Activated by liver -> Angiotensin converting enzyme inhibitors -> reduce angiotensin II

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42
Q

What are the outcomes of therapy with enalapril, benazepril?

A

Reduction in vasoconstriction

Reduction in sodium and water retention

Improved baroreceptor response

Reduced sympathetic tone

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43
Q

What are some side effects of ACE inhibitors?

A

Reduced BP

GIT upset

Increased potassium

Effect on GFR

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44
Q

Which ACE inhibitor is a better choice in the case of renal dysfunction?

A

Benazepril

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45
Q

Which is considered the best drug of choice for hypertension in cats?

A

Amlodipine

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46
Q

What is the mechanism of action of Amlodipine

A

Ca++ channel antagonist

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47
Q

What is the mechanism of action of pimobendin?

A

Sensitizes contractile proteins to Ca (positive inotrope)

Inhibition of phosphodiesterase III&V (balanced vasodilator)

Cytokine modulation, antiplatelet, positive lusitrope (cardiac relaxation)

48
Q

What is an indication for pimobendin?

A

Valve insufficiency

49
Q

What is the mechanism of action of digoxin?

A

Inhibition of Na/K ATP pumps in myocardium -> increased intracellular Na -> decreased extracellular Na / Ca++ exchange -> Increased Ca++ available during contraction (positive inotrope: beats slower, stronger)

50
Q

What are the other effects of digoxin?

A

Increases sensitivity of baroreceptors -> increased vagal tone, decreased symathetic tone, decreased renin levels

Slow AV nodal conduction and prolong refractory periods (slow HR)

51
Q

What are the indications for digoxin?

A

Arrhythmia e.g. supraventricular tachycardia, atrial fibrillation

52
Q

What are the side effects of digoxin

A

LOW margin of safety

Toxicity = vomiting, diarrhoea, depression, cardac arrhythmia

53
Q

What is the mechanism of action of propranalol?

A

Non-selective beta blocker (beta 1 &2)

54
Q

What is the mechanism of action of atenolol?

A

Selective Beta 1 blocker

55
Q

What is the use for Beta blockers in heart failure?

A

Arrhythmias, hypertension

56
Q

Name three beta blockers

A

Propranalol
Atenolol
Carvedilol

57
Q

What are the potential side effects of Beta blockers in CHF?

A

Slow the heart - should be used with caution
May remove the sypathetic compensation keeping the animal alive

58
Q

Name three calcium channel blockers

A

Verapamil, nifedipine, diltiazem

59
Q

What is the mechanism of action of verapamil?

A

Ca++ channel blocker in vascular and cardiac muscle

60
Q

What is the mechanism of action of nifedipine?

A

Ca++ channel blocker in vascular and cardiac muscle

61
Q

What is the mechanism of action of diltiazem?

A

Calcium channel blocker in smooth and cardiac muscle

62
Q

What are the indications for Ca channel blockers?

A

Hypertension, arrhythmias

63
Q

What are some important dietary considerations in CHF

A

Weight loss (reduce load on heart and reduce blood volume)

Reduce Na content

Ensure adequate energy intake

Ensure adequate vitamin intake

Taurine in cats

64
Q

Which ion is involved in the first step of cardiac depolarisation in non-nodal tissue?

A

Na+

65
Q

Which ion is involved in the first step of depolarisation in nodal cardiac tissue?

A

Ca++

66
Q

What effect do drugs that decrease intracellular Na have on the heart?

A

Useful in treating arrhythmias

67
Q

What effects do drugs that increase intracellular Ca++ have on the heart?

A

Useful in treating arrhythmia, but will also

  • decrease HR
  • decrease AV conduction
  • decrease myocardial contractility
68
Q

Name and describe the ion movement of phase 4

A

Resting potential (equilibrium)

69
Q

Name and describe the ion movement of phase 0

A

Rapid depolarization, Na+ in

70
Q

Name and describe the ion movement of phase 1

A

Partial repolarization, K+ out

71
Q

Name and describe the ion movement of phase 2

A

Plateau; Ca++ in and K+ out (balanced)

72
Q

Name and describe the ion movement of phase 3

A

Repolarization. K+ out

73
Q

Name two places where arrhythmias originate

A

Supraventricular

Ventricular

74
Q

Name two ways in which arrhythmias may arise

A

Ectopic foci with spontaneous activity

Abnormal propagation of impulses

75
Q

What changes might you expect on an ECG of a FLUTD cat?

A

Hyperkalaemia =

Suppression of P waves

Widened QRS

Narrowing and peaking of T waves

Bradycardia

76
Q

How do cardiac arrhythias impact heart function

A

Reduce CO:

  • asynchronous atrial/ventricular contraction
  • inefective premature contractions (low SV)

Decreased cardiac efficiency

  • High heart rate (decreased CO)
  • short diastolic period

i.e. increased cardiac oxygen demand, but decreased cardiac output

77
Q

What is the mechanism of action of Class I antiarrhythmic drugs?

A

Block voltage gated Na+ channels

78
Q

What is the mechanism of action of Class II antiarrhythmic drugs

A

Block Beta 1 receptors

79
Q

What is the mechanism of action of Class III antiarrhythmic drugs

A

Block K+ channels

80
Q

What is the mechanism of action of Class IV drugs

A

Block voltage gated Ca++ channels

81
Q

List three class Ia antiarrhythmics

A

Discopyramide

Procainamide

Quinidine

82
Q

What are the effects of Class Ia antiarrhythmics?

A

Block vgNa+ channels:

Decreased rate of depolarization

Decreased AV conduction

Decreased contractility

Increased action potential duration

Increased effective refractory period

83
Q

What are the effects of class Ib antiarrhythmics?

A

Block vgNa+ channels:

Decreased rate of depolarization

Decreased AP duration

Increased effective refractory period

84
Q

What are the effects of Class Ic antiarrhythmics?

A

Block vgNa+ channels:

Decreased rate of depolarization

Decreased AV conduction

Decreased contractility

85
Q

Name two class Ib antiarrhythmics

A

Lignocaine

Mexiletine

86
Q

Name one Class Ic antiarrhythmic

A

Flecainide

87
Q

What are the effects of Class II antiarrhythmics

A

Beta blockers

Decreased AV conduction

Decreased contractility

Decreased heart rate

88
Q

Name 2 class III antiarrhythmics

A

Amiodarone

Sotalone

89
Q

What are the effects of Class III antiarrhythmics?

A

Block K+ channels

Increased action potential duration

Increased effective refractory period

Decreased AV conduction

Decreased contractility (sotalol)

90
Q

Name two Class IV antiarrhythmics

A

Verapamil

Diltiazem

91
Q

What are the effects of class IV antiarrhythmics

A

Block vgCa++ channels:

Decreased action potential duration

Decreased AV conduction

Decreased contractility

92
Q

What are the uses of Class I antiarrhythmics

A

Ventricular tachycardia

Ventricular premature contractility

Procainamide for re-entrant supraventricular tachycardia

93
Q

Briefly describe the re-entry phenomenon in cardiac muscle

A

Normal: Two pathways continue in the same direction

Re-entry: Damaged tissue causes slow propagation in one pathway; Refractory period blocks next depolarisation

Fast pathway depolarises damaged tissue, depol occurs in wrong direction

94
Q

What are the uses of Class II antiarrhythmics

A

Ventricular tachycardia,

Supraventricular tachycardia

Hypertrophic cardiomyopathy in cats

Hypertension

Used with Class I for VT in dogs

95
Q

What are the considerations/cautions with class II antiarrhythmics

A

Chronic use results in up-regulation of receptors: withdraw treatment slowly

Illegal in horse racing

96
Q

What are the uses for Class III antiarrhythmics?

A

Anti-fibrillatory

97
Q

What are the cautions with Class III antiarrhythmics?

A

Side effects poorly documented in animals

Amiodarone: several drug intreactions, particularly with heart medications (e.g. digoxin, quinidine, procainamide)

Sotalol: sudden withdrawal

98
Q

What is the main difference between verapamil and diltiazem?

A

Verapamil: relatively selective for Ca++ channels in cardiac muscle

Diltiazem: Blocks Ca++ channels in cardiac and vascular smooth muscle (fewer cardiac effects, decreased peripheral resistance)

99
Q

What are the uses for Class IV antiarrhythmics?

A

Supraventraicular tachycardia

Hypertrophic cardiomyopathy

Atrial flutter/fibrillation?

Reduce afterload (vasodilate)

100
Q

What are the cautions with Class IV antiarrhythmias

A

Bradycardia, circulatory collapse

Esp in combination with Beta blockers (both slow heart rate)

Verapamil with high first pass effect

101
Q

How is digoxin used as an antiarrhythmic?

A

Supraventricular arrhythmias (atrial fibrillation)

102
Q

Name three other drug classes that might be useful in treating arrhythmias?

A

Anticholinergics

Sympathomimetics

Anticoagulants

103
Q

Name two anticholinergic drugs that might be useful in treating arrhythmias

A

Atropine, glycopyrrolate

104
Q

What are the effects of anticholinergics in treating arrhythmias?

A

Increase sinus rate in AV conduction in bradycardia/bradyarrhythmias, heart block

105
Q

Name a sympathomimetic that might be useful in treating arrhythmias

A

Isoprenaline

106
Q

What are the effects of isoprenaline in treating arrhythmias?

A

Beta selective: increases sinus node rate, AV conduction

107
Q

Name four anticoagulants

A

Warfarin, heparine, aspirin, clopidogrel

108
Q

Why are anticoagulants useful in treating cardiomyopathies?

A

Used for prevention of thromboembolism in cats with HCM and other cardiomyopathies

109
Q

When should treatment of arrhythmias be considered?

A

Treat if haemodynamically signficant: most antiarrhythmics can induce arrhythmias as well as suppress them

  • to restore CVS function
  • to prevent sudden death

TREAT UNDERLYING CAUSE FIRST

110
Q

What three questions should you ask when considering treatment of arrhythmias?

A
  1. Is the arrhythmia compromising the circulovascular system?
  2. Is the arrhythmia a sign of a more life threatening rhythm disturbance?
  3. Is the arrhythmia indicative of underlying cardiac or systemic disease?
111
Q

What treatment would you consider for atrial fibrilation?

A

E.g. in dogs with DCM or MV insufficency
- Digoxin or diltiazem

Treat enlarged atria/CHF: diuretics, ACE inhibitor, pimobenden, anticoagulant

112
Q

Which treatments might you consider for rate control of the heart?

A

Diltiazem +/- digoxin

Beta blockers

113
Q

What treatment might you consider for rhythm control?

A

Electrical cardioversion

Pharmacological cardioversion with amiodarone

Treat enlarged atria/CHF: Diuretics, ACE inhibitor, Pimobenden, anticoagulant

114
Q

What treatment might you consider for re-entrant supraventricular tachycardia?

A

Procainamide

115
Q

What treatment would you consider for ventricular tachycardia?

A

If significant, treat or correct underlying disease

Beta blockers for cats

Lignocain or sotalol for dogs

Pharmacology (12 decks)

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