Small Animal Medicine: Cardiology: Management Of Heart Failure

Front 1

What are the general goals of heart failure treatment?

Back 1

The primary goal of treatment is a cure.
When this is not possible:
1. Improve quality of life (exercise capacity, comfort at rest)
2. Increase survival time if the quality of life is acceptable to the owner
These goals are generally accomplished by improving pump function, resolving congestion, and reducing the work of the heart.

Front 2

What is the general approach to treating heart failure?

Back 2

Control of edema, Na and water retention
Reduce cardiac work
Improve pump function
Antagonize adverse neurohormonal alterations

Front 3

What are some factors that aggravate heart failure and make treating it more difficult?

Back 3

Arrythmias
Thromboembolism
High output states
Cardiac depressants
Hypertension
Increased blood volume
Infection
Poor owner compliance

Front 4

What are the treatment strategies for control of salt and water retention (relief of edema)?

Back 4

1. Diuretics (acute and chronic CHF)
2. Low sodium diets (acute and chronic CHF)
3. Venous and mixed vasodilators (acute and chronic CHF)
4. Angiotensin converting enzyme inhibitors (chronic CHF)
5. Physical removal of fluid (acute and chronic CHF)

Front 5

What are the treatment strategies for reduction of cardiac workload?

Back 5

1. Reduce activity (acute and chronic CHF)
2. Weight reduction in the obese (chronic CHF)
3. Arterial, mixed vasodilator (acute and chronic CHF)

Front 6

What are some treatment strategies for antagonizing adverse neurohormonal alterations?

Back 6

1. Angiotensin converting enzyme inhibition (chronic CHF)
2. Aldosterone antagonism (chronic CHF)
3. Beta receptor blockers (chronic CHF)

Front 7

What are some treatment strategies for improving pump function?

Back 7

1. Improve diastolic function (diastolic filling)
a. Improve ventricular relaxation
b. Control heart rate
c. Abolish arrhythmias (maintain AV synchrony)
2. Improve systolic function (contractility)
a. Calcium sensitizers (acute and chronic CHF)
b. Digitalis glycosides (chronic CHF)
c. Phosphodiesterase inhibitors (acute CHF)
d. Sympathomimetics (acute CHF)

Front 8

What is the FAD treatment for heart failure?

Back 8

Furosemide, ACE inhibitor, Digoxin

Front 9

Are positive ionotropes better for treating systolic or diastolic failure?

Back 9

Beneficial for systolic failure
Not beneficial for diastolic failure because they have a critically limited ability to increase cardiac output and often have congestive signs already.

Front 10

What conditions can be treated with digoxin?

Back 10

CHF + pathologic supraventricular tachycardia
Systolic pump failure (DCM)
Chronic volume overload (mitral regurg, L to R shunting defects)

Front 11

Which disorders is digoxin contraindicated for?

Back 11

Pericardial dz
Obstructive forms of cardiomyopathy
Restrictive myocardial dz
Exception: if any of the above is accompanied by a supraventricular tachycardia

Front 12

What are the signs of "digitalization"?

Back 12

Slowed HR
Relief of clinical signs of heart failure
Increased PR interval
Demonstration of therapeutic blood levels of digoxin

Front 13

True or false:
Digoxin toxicity is rare due to the wide margin of safety.

Back 13

False.
Digoxin has a vary NARROW margin of safety.

Front 14

What are the clinical signs of digoxin toxicity?

Back 14

Anorexia
Nausea
Vomiting
Diarrhea
Depression
Weakness
GI symptoms often occur first

Front 15

What rhythm disturbances can digoxin toxicity cause?

Back 15

First and second degree heart block
Accelerated junctional rhythms
Ventricular premature contractions
Ventricular tachycardia
AV dissociation

Front 16

What happens if digoxin is given too rapidly IV?

Back 16

Vasoconstriction that results in increased afterload and could worsen congestive signs.

Front 17

True or false:
Digoxin toxicity is augmented by electrolyte disturbances.

Back 17

True

Front 18

What are three types of positive inotropic drugs?

Back 18

Beta 1 agonists
Phosphodiesterase inhibitors
Calcium sensitizers

Front 19

Name the beta 1 agonist drugs

Back 19

Dobutamine
Dopamine
Isoproterenol

Front 20

Name some phosphodiesterase inhibitors

Back 20

Pimobendan
Bipyridines (amrinone, milrinone)

Front 21

Name two drugs that are calcium sensitizers and inodilators

Back 21

Pimobendan
Levosimendan

Front 22

What is the mechanism of action of beta 1 agonists?

Back 22

Stimulation of beta 1 receptors --> increased cAMP via adenylate cyclase --> increase in slow inward Ca currents and Ca storage b the SR --> increased Ca availability for contraction

Front 23

What is the mechanism of action of phosphodiesterase inhibitors?

Back 23

Increase cAMP by PDE inhibition --> activation of cAMP dependent protein kinase --> phosphorylation of target proteins such as Ca channels in the plasma membrane --> increased Ca influx --> increased velocity and force of contraction
Also acts as a direct arterial vasodilator

Front 24

What is the mechanism of action of calcium sensitizing drugs?

Back 24

Increased Ca affinity of troponinC (Ca binding protein) or stabilization of the Ca-induced conformational change of troponin C --> increased sensitivity o myofilaments to a given Ca concentration

Front 25

What is the mechanism of action of digoxin?

Back 25

Inhibits Na/K pump --> more Ca into cell

Front 26

What is the mechanism of action of dobutamine?

Back 26

Beta 1 and weak beta 2 agonist --> increased contractility with little change in heart rate or afterload
Less chronotropic effect than dopamine

Front 27

What is the mechanism of action of dopamine?

Back 27

Beta 1 agonist --> NE release --> increased contractility with minimal increases in HR
Low doses: selective dilation of arterioles in the renal, mesenteric, coronary and cerebral vascular beds
High doses: generalized systemic vasoconstriction

Front 28

Name some calcium channel blocking drugs

Back 28

Verapamil
Ditiazem

Front 29

What are the indications for calcium channel blockers?

Back 29

Used mainly for anti-arrhythmic effects

Front 30

Name some Beta blockers

Back 30

Propanolol
Atenolol
Esmolol

Front 31

What are beta blockers used to treat?

Back 31

SV arrhythmias + ventricular arrhythmias induced by sympathetic tone

Front 32

What is the mechanism of action of beta blockers?

Back 32

Slows conduction of impulses through the AV node
Potent negative inotropes (can worsen CHF)

Front 33

Name some ACE inhibitors

Back 33

Enalapril
Captropril
Lisinopril

Front 34

How do ACE inhibitors work?

Back 34

Inhibits angiotensin converting enzyme from making more angiotensin II which in turn prohibits vasoconstriction which should lower afterload and congestive signs

Front 35

Name some vasodilators

Back 35

Nitroglycerine
Nitroprusside
Hydralazine
Amiodipine
Prazosin

Front 36

Which vasodilators are specifically arterial dilators?

Back 36

Hydralazine
Amlodipine
Nifedipine

Front 37

What are arterial dilators used for?

Back 37

Used to lower inappropriately high SVR in patients with severe CHF by reducing afterload and increasing cardiac output
Reduces myocardial O2 consumption
Increases CO
Decreases regurgitant volume
Increases forward output in patients with aortic insufficiency and mitral regurg.
Lessen magnitude of L to R shunts (VSD, PDA)
Hydralazine is most used as a short term treatment for dogs with heart failure due to mitral regurg

Front 38

Which vasodilators are specifically venous dilators?

Back 38

Nitroglycerine
Isosorbide dinitrate
Isosorbide mononitrate

Front 39

What are venous dilators used for?

Back 39

Used to reduce congestive symptoms by redistributing blood volume w/in circulatory system and lowering filling pressures

Front 40

Name three mixed dilators

Back 40

Nitroprusside (only direct acting mixed vasodilator available)
Prazosin
ACE inhibitors

Front 41

What emergency situation might you use nitroprusside?

Back 41

Nitroprusside mainly used to rescue dogs w/severe decompensated CHF caused by mitral regurg or DCM

Front 42

What is the most important class of neurohormonal antagonists currently available for CHF tx?

Back 42

ACE inhibitors

Front 43

How do ACE inhibitors help with CHF?

Back 43

Reduce angiotensin II --> less vasoconstriction and less circulating aldosterone ==> decreased atrial and ventricular filling pressures, decreased peripheral vascular resistance and increased CO

Front 44

What is "aldosterone escape"?

Back 44

Dogs that are on ACE inhibitors long term may still have high aldosterone

Front 45

What are 3 treatment protocols for acute CHF?

Back 45

FOND: Furosemide, Oxygen, Nitroprusside, Dobutamine (best for systolic failure)
FOAM: Furosemide, Oxygen, Amrinone or Milrinone
FOP: Furosemide, Oxygen, Pimobendan

Front 46

What is the FAD protocol?

Back 46

Treatment for chronic CHF
Furosemide, ACE inhibitor, Digoxin (or pimobendan) +/- spirinolactone
Digoxin is also used if systolic failure

Front 47

How do you treat severe, refractory, or recurrent, congestive heart failure?

Back 47

Maximize diuretic doses
Combination diuretic therapy: Loop + Thiazide + Spirinolactone
Mechanically remove fluid if needed