Management of canine CHF (Yr 3)

Question 1

what are the four main consequences of heart failures?

Answer 1

vasoconstriction
tachycardia
myocardial remodelling/fibrosis
oedema/effusions

Question 2

what is the immediate life threatening issue associated with left sided CHF?

Answer 2

pulmonary oedema

Question 3

what is the main immediate problem associated with CHF?

Answer 3

sodium and water retention

Question 4

what effects does the sodium/water retention in right sided CHF?

Answer 4

ascites, hepatomegaly, pleural effusion

Question 5

what is the first choice treatment for oedema and effusions?

Answer 5

diuretics (furosemide)

Question 6

what is the first choice diuretic?

Answer 6

furosemide

Question 7

how much furosemide should be given in chronic cases?

Answer 7

lowest dose possible to control the clinical signs

Question 8

how do you titrate furosemide to effect?

Answer 8

owner monitors the sleeping/resting respiratory rate and then can reduce dose if there is no increase in respiratory rate (very sensitive way of monitoring how controlled CHF is)

Question 9

what are the main two side effects of furosemide?

Answer 9

pre-renal azotaemia
hypokalaemia
(must monitor renal function)

Question 10

what needs to be monitored when a patient is on diuretics such as furosemide?

Answer 10

renal function (urea, creatinine, electrolytes)

Question 11

should furosemide be used on its own?

Answer 11

should be used as monotherpay long term as it activates RAAS (leading to more remodelling/fibrosis)

Question 12

what should be done if furosemide is no longer working and you have reached the maximum dose?

Answer 12

ensure optimised use of ACE inhibitors
consider parenteral administration (GIT oedema in right sided CHF can inhibit absorption)
resistance can develop so consider other diuretics (sequential nephron blockade)
consider swapping for another loop diuretic (torasemide)

Question 13

what diuretics can be added to furosemide for sequential nephron blockade?

Answer 13

spironolactone
amiloride/hydrochlorothiazide
(need to monitor renal function)

Question 14

what type of drug is spironolactone?

Answer 14

aldosterone antagonist
potassium sparing diuretic

Question 15

is thoracocentesis indicated with pleural effusions caused by CHF?

Answer 15

yes (don’t wait until diuretics take effect!!)

Question 16

how do ACE inhibitors work?

Answer 16

counteract adverse effects of angiotensin II

Question 17

what do ACE inhibitors do?

Answer 17

vasodilators
reduced aldosterone release (reduced sodium/water retention)
prevent angiotensin 2 mediated myocardial fibrosis/remodelling
anti-adrenergic effects
vasopressin release
endothelin release
increased bradykinin and vasodilatory prostaglandins
prevent glomerular capillary hypertension

Question 18

what are some ACE inhibitors available?

Answer 18

enalapril
benazepril
ramipril
imidapril

Question 19

when should ACE inhibitors be avoided?

Answer 19

if the animal is severely hypotensive as they may compromise renal function

Question 20

what are the potential side effects of ACE inhibitors?

Answer 20

hypotension
renal impairment
hyperkalaemia
anorexia, diarrhoea, vomiting…

Question 21

what needs to be monitored when a patient is on ACE inhibitors?

Answer 21

blood pressure
renal function and electrolytes

Question 22

what angiotensin 2 receptor blocker is licensed?

Answer 22

telmisartan (in cats but not licensed for CHF)

Question 23

when would venodilators be used for CHF?

Answer 23

rapid control of pulmonary oedema

Question 24

what venodilators can be used for rapid control of pulmonary oedema?

Answer 24

IV furosemide
topical nitroglycerine ointment (apply to hairless well perfused area)

Question 25

what is the use of arteriodilators in CHF cases?

Answer 25

reduced myocardial workload by reducing systemic blood pressure and hence afterload (reduces myocardial oxygen consumption)

Question 26

what are some arteriodilator drugs?

Answer 26

pimobendan (balanced vasodilator)
amlodipine
hydralazine
ACE inhibitors

Question 27

what is the mode of action of pimobendan?

Answer 27

positive inotrope (calcium sensitiser and phosphodiesterase inhibitor)
vasodilator (phosphodiesterase inhibitor)

Question 28

how is pimobendan administered?

Answer 28

orally (inhibited by food so should be given on an empty stomach)

Question 29

how can we counteract the high sympathetic drive in CHF?

Answer 29

mainly use drugs to improve haemodynamic status to indirectly reduce sympathetic drive

Question 30

should beta blockers be used in CHF?

Answer 30

no never use them in uncontrolled CHF especially if there is poor contractility

Question 31

what is a good treatment for high sympathetic drive in CHF cases?

Answer 31

digoxin (enhance vagal tone, reduce sympathetic drive)

Question 32

what are the main functions of digoxin?

Answer 32

negative chronotrope
weak positive inotrope
favourable autonomic effects

Question 33

when is digoxin use indicated?

Answer 33

atrial fibrillation - main indication
supraventricular tachyarrhythmias
if impaired systolic function
(vagomimetic)

Question 34

what effects dose digoxin have as it is a vagomimetic?

Answer 34

stimulates vagal centres in CNS, sensitises baroreceptors to BP changes, enhance pacemaker response to acetylcholine
all of these result in slowed rate of discharge through SAN, slowed conduction through AVN and increased refractory period in AVN

Question 35

what are some signs of digoxin toxicity?

Answer 35

excessive borborygmi
depression
anorexia
vomiting/diarrhoea
cardiac arrhythmias

Question 36

what patients are more predisposed to digoxin toxicity?

Answer 36

thin, obese, ascites, hypoproteinaemia, hypothyroidism, impaired renal function, dobermans, hypoxia, hypokalaemia

Question 37

what is the standard treatment therapy of CHF in dogs (for either MVD or DCM)?

Answer 37

furosemide
pimobendan
ACE inhibitor (benazepril)
spironolactone

Question 38

can you start treatment for preclinical myxomatous mitral valve disease or DCM?

Answer 38

yes - at risk animals can be given pimobendan (can prolong their life before they go into CHF)

Question 39

what drug can be used to delay the onset of CHF in potential DCM and MMVD?

Answer 39

pimobendan