Heart Failure

Question 1

Causes of increased afterload (pressure overload):

Answer 1

Aortic or subaortic stenosis
Pulmonary valve stenosis
Tetrology of fallot
pulmonary ot systemic hypertension

Question 2

Causes of volume overload:

Answer 2

Valve insufficiencies
Shunting lesions (VSD, ASD, PDA)

Question 3

Causes of impaired contractility (myocardial disease)

Answer 3

DCM phenoctype

Question 4

Causes of impaired diastolic filling:

Answer 4

HCM phenotype
Restrictive cardiomyopathy
Pericardial effusion
Constrictive pericarditis

Question 5

What is the Frank-Starling mechanism for compensation?

Answer 5

Increased stretch on the myofibers induces greater stoke volume on subsequent contraction
Helps empty enlarged ventricle and preserve forward CO

Question 6

How does neurohormonal activation help in HF compensation?

Answer 6

Increases systemic vascular resistance (SVR) when decr CO to maintain BP
BP = CO x SVR
sympathetic, RAAS, ADH
Acute: compensatory and beneficial
Chronic: maladaptive and harmful

Question 7

How does the sympathetic nervous system help in HF?

Answer 7

Decr CO sensed by baroreceptors in carotid sinus and aortic arch
> signal transmitted to control center in the medulla
> decr inhibitory input from baroreceptors
> Incr sympathetic tone and decr parasymp = NE release and stim of alpha and beta receptors
> incr HR, incr Na reabsorption, incr peripheral vascular resistance

Question 8

How does short term vs long term sympathetic compensatory activation vary?

Answer 8

Short term: Compensatory
- ^ HR and contractility
- Vasoconstriction, RAAS activation (Na retention)
Long term: maladaptive
- ^ myocardial oxygen demand (MVO2)
- Chronic RAAS activation (cardiac fibrosis, arrhythmias, hypertrophy)

Question 9

What do ACE-inhibtors do?

Answer 9

Inhibit the cleave of angiotensin I to angiotensin II

Question 10

Can beta blockers be used in dogs and cats?

Answer 10

No proven to be helpful

Question 11

What kind of hypertrophy do pressure and volume overloads cause?

Answer 11

Pressure: concentric
Volume: eccentric

Question 12

What is the purpose of ventricular remodeling:

Answer 12

Enhancement of cardiac performance
Decrease wall stress (decreased MVO2)
Maintain stroke volume

Question 13

CS of HF

Answer 13

Decreased CO and tissue perfusion:
-exercise intolerance/weakness
-syncope
-pale or gray mm, prolonged CRT
-decreased arterial pulse quality
-cool periphery
-arrythmias

Question 14

What causes pulmonary edema?

Answer 14

Left sided heart failure
hydrostatic pressure overwhelms lymphatics
fluid accumulation in interstitium (and alveoli when severe)

Question 15

What does NT-proBNP measure?

Answer 15

Released in response to increased ventricular wall stress:
useful for differentiating cardiac nad non-cardiac causes of dyspnea/screening for cardiomyopathy
Cardiopet: send out test on plasma, dogs and cats
ELISA SNAP: whole blood of pleural effusion, cats only

Question 16

What causes ascites?

Answer 16

Ascites from: Right sided CHF
Increased hydrostatic pressure in systemic veins: leaky hepatic capillaries
Increased formation of hepatic lymph

Question 17

What does systemic venous pressure cause in right sided CHF?

Answer 17

Jugular vein distension
Hepatomegaly
Ascites (palpable fluid wave)
Pleural effusion (muffled lung sounds)
Small vol pericardial effusion
SQ edema: large animals

Question 18

What causes biventricular HF?

Answer 18

Concurrent right and left sided disease
Severe left sided heart disease such as DCM or MMVD complicated by atrial fibrillation

Question 19

Diagnosis of CHF

Answer 19

History
PE
Thoracic Rads
+/- POCUS/ NT-proBNP, echo

Question 20

What are ECG findings that are very indicative of HF?

Answer 20

Atrial fibrillation
left bundle branch block

Question 21

What are radiographic findings that are very indicative of HF?

Answer 21

Distended pulmonary veins or caudal vena cava

Question 22

How do diuretics work in HF?

Answer 22

Promotes increased production of urine
GOAL: Reduce preload
-Loop diuretics
-K sparing diuretics
-Thiazide diuretics

Question 23

Loop diuretics

Answer 23

Furosemide, torsemide, bumetanide
Strongest class of diuretics
Inhibits Na/K/Cl co transporter in the thick ascending loop of henle
Rapid onset of action
Affected by renal blood flow
(decr efficacy w/ renal failure and NSAIDs)

Question 24

Potassium Sparing Diuretics

Answer 24

Spironolactone
Mineralocorticoid receptor antagonist (MRA)
-blocks action of aldosterone at distal tubule
-antagonizes cardiotoxic effects of aldosterone
Weak diuretic effect
Adjuct tx for HF or acsites

Question 25

Thiazide diuretics

Answer 25

Hydrochlorothiazide
Inhibits Na/Cl transporter in convoluted tubule
Side effects: hypokalemia, hypercalcemia, ventricular arrhythmia, nausea

Question 26

What are examples of positive inotropes?

Answer 26

Calcium sensitizers
Digitalis glycosides
Catecholamines

Question 27

Pimobendan

Answer 27

Inodilator: inotrope + vasodilator
Calcium sensitizer: increases interaction between calcium and and troponin C
Phosphodiesterase-3 inhibitor (peripheral vasodilation)
-Assymptomatic MMVD and DCM adn CHF

Question 28

Dobutamine

Answer 28

Potent positive inotrope
Increase CO and decr edema formation
Improve arterial BP

Question 29

Digoxin

Answer 29

Digitalis glycoside/positive inotrope
Inhibits Na/K ATPase
Indications: rate control of a-fib
excreted by kidney, narrow therapeutic index

Question 30

Vasodilators

Answer 30

Venodilators: decr preload
Ateriodilators: decr afterload
Amlodipine
Hydralazine
Sodium nitroprusside
Nitroglycerin

Question 31

ACE-inhibitors

Answer 31

Enalapril, benazopril
Inhibits conversion of angiotensin I to angiontensin II
Decr AT II mediated vasoconstriction and volume retention
Used in chronic CHF

Question 32

Acute CHF therapy:

Answer 32

FOPS
Furosemide: diuretic
Oxygen supplementation
Pimobendan -inodilator
Sedation (if needed) -butorphanol
Cats: add clopidogrel (antiplatelet)

Question 33

Acute thromboliortic thromboembolism tx in cats

Answer 33

Analgesia
Anti-coag (heparin)
Clopidogrel (antiplatelet)
+/- tx of CHF
poor prognosis

Question 34

Chronic CHF therapy

Answer 34

Dogs are for special people
Diet: low sodium
ACE inhibitor (enalapril or benazepril)
Furosemide
Spironolactone
Pimobendan

Question 35

What might you also need to do in chronic right sided CHF?

Answer 35

Thoracocentesis/abdominocentesis

Question 36

Chronic CHF management in cats

Answer 36

Furosemide
Clopidogrel
+/- pimobendan (LV outflow obstruction)

Question 37

CHF managment in horses

Answer 37

Furosemide
Digoxin
Pimo/ACE maybe
Pronosis is poor

Question 38

Treatment of refractory CHF in dogs (stage D):

Answer 38

Increase pimo dose
Furosemide > torsemide (more potent)
Vigorous afterload reduction: amlodipine, nitropursside, hydralazine
+/- sildenafil if concurrent pulmonary hypertension

Question 39

Refractory CHF tx in cats (Stage D):

Answer 39

Furosemide > torsemide
Spironolactone
+/- taurine if systolic dysfunction

Question 40

What is diuretic resistance?

Answer 40

decreased renal responsiveness to natriuretic peptides due to chronic RAAS and SNS activation
> leads to increased Na retention

Question 41

How do you overcome diuretic resistance?

Answer 41

Add ACE inhibitor and/or spironolactone
Sequential nephron blockade (add additional diuretics)
Torsemide

Question 42

Dietary Recs for CHF:

Answer 42

Adequate calorie intake, high quality protein
Low sodium
K+ supplementation if needed