Heart Failure Flashcards
Causes of increased afterload (pressure overload):
Aortic or subaortic stenosis
Pulmonary valve stenosis
Tetrology of fallot
pulmonary ot systemic hypertension
Causes of volume overload:
Valve insufficiencies
Shunting lesions (VSD, ASD, PDA)
Causes of impaired contractility (myocardial disease)
DCM phenoctype
Causes of impaired diastolic filling:
HCM phenotype
Restrictive cardiomyopathy
Pericardial effusion
Constrictive pericarditis
What is the Frank-Starling mechanism for compensation?
Increased stretch on the myofibers induces greater stoke volume on subsequent contraction
Helps empty enlarged ventricle and preserve forward CO
How does neurohormonal activation help in HF compensation?
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
How does the sympathetic nervous system help in HF?
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
How does short term vs long term sympathetic compensatory activation vary?
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)
What do ACE-inhibtors do?
Inhibit the cleave of angiotensin I to angiotensin II
Can beta blockers be used in dogs and cats?
No proven to be helpful
What kind of hypertrophy do pressure and volume overloads cause?
Pressure: concentric
Volume: eccentric
What is the purpose of ventricular remodeling:
Enhancement of cardiac performance
Decrease wall stress (decreased MVO2)
Maintain stroke volume
CS of HF
Decreased CO and tissue perfusion:
-exercise intolerance/weakness
-syncope
-pale or gray mm, prolonged CRT
-decreased arterial pulse quality
-cool periphery
-arrythmias
What causes pulmonary edema?
Left sided heart failure
hydrostatic pressure overwhelms lymphatics
fluid accumulation in interstitium (and alveoli when severe)
What does NT-proBNP measure?
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
What causes ascites?
Ascites from: Right sided CHF
Increased hydrostatic pressure in systemic veins: leaky hepatic capillaries
Increased formation of hepatic lymph
What does systemic venous pressure cause in right sided CHF?
Jugular vein distension
Hepatomegaly
Ascites (palpable fluid wave)
Pleural effusion (muffled lung sounds)
Small vol pericardial effusion
SQ edema: large animals
What causes biventricular HF?
Concurrent right and left sided disease
Severe left sided heart disease such as DCM or MMVD complicated by atrial fibrillation
Diagnosis of CHF
History
PE
Thoracic Rads
+/- POCUS/ NT-proBNP, echo
What are ECG findings that are very indicative of HF?
Atrial fibrillation
left bundle branch block
What are radiographic findings that are very indicative of HF?
Distended pulmonary veins or caudal vena cava
How do diuretics work in HF?
Promotes increased production of urine
GOAL: Reduce preload
-Loop diuretics
-K sparing diuretics
-Thiazide diuretics
Loop diuretics
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)
Potassium Sparing Diuretics
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
Thiazide diuretics
Hydrochlorothiazide
Inhibits Na/Cl transporter in convoluted tubule
Side effects: hypokalemia, hypercalcemia, ventricular arrhythmia, nausea
What are examples of positive inotropes?
Calcium sensitizers
Digitalis glycosides
Catecholamines
Pimobendan
Inodilator: inotrope + vasodilator
Calcium sensitizer: increases interaction between calcium and and troponin C
Phosphodiesterase-3 inhibitor (peripheral vasodilation)
-Assymptomatic MMVD and DCM adn CHF
Dobutamine
Potent positive inotrope
Increase CO and decr edema formation
Improve arterial BP
Digoxin
Digitalis glycoside/positive inotrope
Inhibits Na/K ATPase
Indications: rate control of a-fib
excreted by kidney, narrow therapeutic index
Vasodilators
Venodilators: decr preload
Ateriodilators: decr afterload
Amlodipine
Hydralazine
Sodium nitroprusside
Nitroglycerin
ACE-inhibitors
Enalapril, benazopril
Inhibits conversion of angiotensin I to angiontensin II
Decr AT II mediated vasoconstriction and volume retention
Used in chronic CHF
Acute CHF therapy:
FOPS
Furosemide: diuretic
Oxygen supplementation
Pimobendan -inodilator
Sedation (if needed) -butorphanol
Cats: add clopidogrel (antiplatelet)
Acute thromboliortic thromboembolism tx in cats
Analgesia
Anti-coag (heparin)
Clopidogrel (antiplatelet)
+/- tx of CHF
poor prognosis
Chronic CHF therapy
Dogs are for special people
Diet: low sodium
ACE inhibitor (enalapril or benazepril)
Furosemide
Spironolactone
Pimobendan
What might you also need to do in chronic right sided CHF?
Thoracocentesis/abdominocentesis
Chronic CHF management in cats
Furosemide
Clopidogrel
+/- pimobendan (LV outflow obstruction)
CHF managment in horses
Furosemide
Digoxin
Pimo/ACE maybe
Pronosis is poor
Treatment of refractory CHF in dogs (stage D):
Increase pimo dose
Furosemide > torsemide (more potent)
Vigorous afterload reduction: amlodipine, nitropursside, hydralazine
+/- sildenafil if concurrent pulmonary hypertension
Refractory CHF tx in cats (Stage D):
Furosemide > torsemide
Spironolactone
+/- taurine if systolic dysfunction
What is diuretic resistance?
decreased renal responsiveness to natriuretic peptides due to chronic RAAS and SNS activation
> leads to increased Na retention
How do you overcome diuretic resistance?
Add ACE inhibitor and/or spironolactone
Sequential nephron blockade (add additional diuretics)
Torsemide
Dietary Recs for CHF:
Adequate calorie intake, high quality protein
Low sodium
K+ supplementation if needed
