CHF

• Common in vet med, congenital or acquired (usu acquired)
• Southeast caused by Heartworm
• everywhere caused by vavular and myocardial disease (particularly mitral valve)
• Careful monitoring and cooperation and compliance of owner

• four chambered pump (2 pumps)
• Responsible for moving blood through vascular system.
• Composed of myocardium, VERY strong, thick muscle

Vena cava, right atrium, tricuspid valve, right ventricle, pulmonic valve, pulmonary artery, lungs, pulmonary vein, left atrium, mitral valve, left ventricle, aortic valve

chamber filling

chamber contraction

quantity of blood pumped by left ventricle into the aorta with each ventricular contraction

• quantity of blood pumped by the left ventricle into the aorta each minute
• stroke volume x heart rate

• stretch of the walls of the left ventricle after passive filling and atrial contraction
• Measured by left ventricular end diastolic volume (LVEDV)

volume of blood in the left ventricle at the end of diastole

pressure exerted on walls of left ventricle at the end of diastole

• impedance to blood flow through the systemic arteries determined by the tone of vascular smooth muscle and blood vessel diameter
• Increased by constriction of systemic arteries

resistance against which the left ventricle must eject its volume of blood during contraction (determined by aortic pressure, determined by PVR)

• Failure of the heart to pump sufficient blood to meet the metabolic needs of the body and/or prevent blood from pooling in pulmonary venous circulation
• Right CHF, fluid overload into vena cava, third-spacing into abdomen, ascites
• Left CHF, more common, fluid overload into lungs, pulmonary edema
• Sets off coping mechanism that makes things worse by retaining H2O and Na

• Dilated area in heart, lumen large and muscles thinner.  Usually left ventricle to start. Myocardium weak, inadequate contraction, decreased stroke volume
• Acquired common in large and giant breed middle aged dogs (left and right sided dilation, left first most common, can be both)
• Ventricle can't pump properly, backflow into atrium, atrium stretches, can't pump properly, backflow causing CHF
• Was common in cats before taurine

• Common in cats
• myocardial walls (esp left ventricle) thick and stiff, decreased diastolic filling (DIASTOLIC DYSFUNCTION), increase in atrial backup and pressure lead to LA enlargement/dilation, hydrostatic pressure, pleural effusion and pulmonary edema

fluid in parenchyma of lungs

fluid outside lungs, within thorax

turbulence in blood flow

• inadequate closure of mitral (left AV) valve.  mostly seen in small, older dogs
• 50% of stroke volume regurgitated into left atrium during systole initially, can go to 75-90%
• Leads to left atrial dilation, decreased stroke volume, decreased CO, increased pressure, pulmonary edema, CHF

Pulmonary veins can't take as much fluid overload before symptoms.  Abdomen can take fluid before there's a problem.

fluid in interstitial space increase diffusion distance, so less O2.  May be increased CO2 because it is more soluble in water

• decreased CO
• CO x PVR = BP, so decreased BP
• reflex tachycardia and renin secretion
• aldosterone secretion retains water and sodium, making problem worse
• Baroreceptor reflex attempts to normalize BP, reflex tachycardia, heart enlarges, lower CO

• decreased CO leads to decreased blood flow to myocardium
• reflex tachycardia leads to lower CO (shortens filling time)
• Increased heart rate increases workload, increasing O2 consumption (necrosis/fibrosis/ischemia/attack)
• lowered BP causes increased sympathetic, vasoconstriction to increase BP, increases workload of heart.  
• Renin-angiotensin system increases fluid retention, increases preload, increases workload

• quantity of blood flowing from vena cava into right atrium each minute
• Increase of venous return increases ventricular preload

• stretch of the walls of the left ventricle after passive filling and atrial contraction
• Increased preload increases workload

• Myocardium gets inadequate blood flow
• workload increases, O2 consumption increases
• ischemia worsens heart failure

• tachycardia
• dyspnea +/- tachypnea (pulmonary edema, pleural effusion in cats)
• exercise intolerance
• mild-to-moderate ascites
• cough (enlarged heart presses on trachea, rare in cats)
• Dogs can have murmur, only 30% of cats do

• respiratory distress, dyspnea
• severe exercise intolerance, collapse
• profound muscle fatigue, no O2
• marked ascites (cats, R side)

• inhibit compensation of body
• improve contraction of left ventricle

• Cardiac (digitalis) glycosides
• Pimobendan
• Catecholamines (ER only)

• positive inotrope, increases CO, decreases dyspnea and HR (only one)
• increases contractile force of myocardium
• used in supraventriculartachyarrhythmias and myocardial failure. Not good for HCM, DCM, pericardial disease or tumors.
• Toxicity common, narrow TI
• Signs of toxicity: arrhythmias, electrolyte imbalance, anorexia, vomiting, lethargy, depression

• increases force of contraction without increasing HR
• withdrawal of sympathetic tone decreases HR
• Increases Ca in heart, increases contraction

• positive inotrope, increase sensitivity of myocardial cells to Ca
• dilates arterioles and veins, decreases afterload, decreases PVR, decreases preload (pooling in veins), heart works less, less back pressure, less third-spacing.
• Only prolonged survival in DCM and mitral insufficiency (indications).
• Entire tablet must be used in one day if split, empty stomach, causes diarrhea.  
• Contra in outflow obstruction, causes hypotension.

• Crisis treatment, short-term
• dobutamine (increases force of contraction more than HR, drug of choice, indirect B1 increase)
• dopamine (for HF due to anesthetic ER or after cardiac resusitation, after the fact, dose-related modulation)
• Epi, Isoproterenol are arrhythmogenic.  Epi for arrest/anaphalaxis, Iso in atropine refractory bradycardia (vagal bradycardia, unresponsive)

• Arterial dilation lowers PVR to increase CO. Aortic pressure decreases, afterload decreases, stroke volume increases, cardiac output increases.
• Causes hypotension. 
• Pimobendan (dilates V&A, increases survival)
• Prazosin (a1 block, dilates V&A)
• Hydralazine (dilates A, decreases afterload, inhibits movement of Ca, can't contract)

• venodilators decrease preload
• dilation of vein increases capacitance, decrease venous return, decreases preload, decreases third spacing. 
• Nitroglycerin (dynamite!), topical only.

• venodilator. CHF treatment in crisis and short-term.  Decreases volume ASAP.  
• applied topically to hairless skin (ears)
• dose determined by strip
• significant first pass biotransformation, metabolites 10x less potent
• wear gloves, cover site with tape

• increase volume of urine secreted by kidneys (anti-aldosterone)
• Furosemide most common, interferes in loop of Henle, makes hypokalemia.
• spironolactone is an aldosterone receptor antagonist.  Keeps potassium (hyperkalemia)

• lasex. Intereferes with Na transport in loop of Henle.  Diuretic.  Secretes water, Na and K.  Lasts 6 hours, very potent.
• Lowers volume, lowers preload

• aldosterone receptor antagonist diuretic, potassium sparing
• Useful in early aldosterone escape
• lowers volume
• lowers preload

• increase volume of urine excreted
• decrease plasma volume
• decrease venous return
• decrease ventricular preload
• decrease third spacing.

• Pimobendan, V&A, decreases preload and afterload
• Prazosin, V&A, decreases preload and afterload
• Hydralazine, A only, decreases afterload
• Nitrogylcerine, V only, decreases preload

• vasodilators increase CO and decrease preload
• a-adrenergic antagonists (prazosin)
• ACE inhibitors (enalapril, benazepril) balanced venodilators prevent angiotensin II which is an artery and venous constrictor
• Dilate arterioles and veins equally.
• arterial dialation - decreased PVR - decreased afterload - increased CO
• venodilation - decreased venous return - decreased preload - decreased pulmonary edema

• a-adrenergic receptor antagonist
• vasodilator, increases CO and decreases preload

• Angiotensin Converting Enzyme (ACE) inhibitor, eliminated entirely in kidneys.
• balanced vasodilator (equal a and v)
• dilate arteries, decrease PVR, decrease AFTERLOAD, increase CO
• dilate veins, decrease veinous return, DECREASE PRELOAD, decrease pulmonary edema
• Makes people cough but not animals.  Idiopathic

• Angiotensin Converting Enzyme (ACE) inhibitor, eliminated in kidneys and bile
• balanced vasodilator (equal a and v)
• dilate arteries, decrease PVR, decrease AFTERLOAD, increase CO
• dilate veins, decrease veinous return, DECREASE PRELOAD, decrease pulmonary edema

• Vasodilators of choice in CHF
• inhibit angiotensin converting enzyme (ACE), decreasing angiotensin II, which causes vasoconstriction, water/Na retention, aldosterone release and ADH release
• Improves survival time, but must monitor renal function (perfusion)
• Enalapril, benazepril

• decreased SV = decreased CO = decreased arterial BP
• Reflex decreased parasympathetic and increased sympathetic = increased HR and increased arterial vasoconstriction = increased PVR, = increased AFTERLOAD
• Increases workload of heart, causing heart to enlarge and use more O2 it doesn't have, causing decreased ventricular contractility and more decreased CO

• decreased SV = decreased CO = decreased BP
• decreased BP in kidney = renin release = angiotensin pathway =
• angiotensin II = vasoconstriction (increased PVR), increased water and Na retention, increased aldosterone and increased ADH, all causing increased plasma volume = increased venous return = increased PRELOAD
• increasing workload of heart = enlargement and hypoxia = decreased ventricular contractility and decreased CO

use them early in disease to slow progression and delay heart failure (even asymptomatic)

• at beginning of administration of ACE inhibitors, aldosterone is released anyway (another mechanism?)
• Spironolactone

• few.
• Initial steep decrease in arterial BP
• Potential for renal failure.  Drops pressure in glomerular capillaries, decreases GFR, increases BUN and creatinine causing azotemia.  Must decrease furosimide first, then ACE.

• No clinical signs except with powerful exercise or severe CV challenges
• do not treat with drugs, just avoid high salt in diet

• Exhibit clinical sings with mild or moderate exercise
• ACE inhibitor (enalapril) and salt restricted diet
• monitor renal function

• Overt signs with mild exercise: cough, dyspnea, orthopnea, exercise intolerance, pulmonary edema, ascites in right sided disease
• Diuretics, ACE inhibitor, digoxin (tachyarrhythmias) or pimobenden, salt and exercise restriction

• Acute discompensation
• Require aggressive emergency therapy: vasodilators, IV diuretics, oxygen, inotropes.  Add ACE inhibitors once stabilized (can't pill a sick dog)

• non-selective IV B blocker, watch for asthmatics or breathing problems.  
• Used in early CHF to decrease HR and renin release, decrease pathological changes in heart, increase contractile force of heart muscle.  Seems worse for up to 3 months, but helps.

• cardio-selective PO B blocker
• Used in cats with HCM or hyperthyroid (T4 causes sympathetic increase) while waiting for methimazole to work.
• Used in early CHF to decrease HR and renin release, decrease pathological changes in heart, increase contractile force of heart muscle.  Seems worse for up to 3 months, but helps.

• cardio-selective PO B-blocker of choice in early CHF, decreasing ischemia and fibrosis.
• Used in early CHF to decrease HR and renin release, decrease pathological changes in heart, increase contractile force of heart muscle.  Seems worse for up to 3 months, but helps.

• Useful due to systolic dysfunction.  decreased BP causes maximum sympathetic outflow and therefore excessive catecholamine release
• decreases available B1 receptors in heart, decreasing tachycardia/arrhythmias and pathological changes (ischemia, fibrosis, enlarged chambers)

stretching neck out as far as possible in an effort to get a good breath.  Seen in CHF (class III)

• decrease HR and renin release
• decrease pathological changes to heart (ischemia, fibrosis, enlargement or dilated chambers
• Increases contractile force of heart muscle
• Feel worse for up to 3 months, then better.  Only use early in CHF when cardiac function is still okay

decreasing or increasing the numbers of receptors available

• Blood backs up into left atrium, eventual L atrial enlargement.  Blood backs up into pulmonary circulation, increases hydrostatic pressure, pulmonary edema and/or pleural effusion
• decreased SV, decreased CO, insufficient CO to meet needs of body, CHF.

• Diuretics to decrease preload (furosimide)
• decreases plasma volume, decreases VR, decreases pressure in L atrium, decreases hydrostatic pressure in pulmonary capillaries, decreasing pulmonary edema and pleural effusion.

• Diuretics: decrease preload (Furosimide)
• Calcium channel blockers: vasodilation, neg inotrope and dromotrope (diltiazem)
• Beta Blockers: increases diastolic filling and relaxes heart
• ACE inhibitors: decrease angiotensin II

vasodilation, negative dromotrope and inotrope. Does not decrease sympathetic sensitivity, so BP stays the same and HR increases (diltiazem, amlodipine)

Calcium channel blocker causing vasodilation.  Good for hypertension

calcium channel blocker used in feline HCM.  Vasodilator, relaxes heart, increases HR.  BP remains the same.

• used usually in cats with systolic anterior motion of the mitral valve (controversial).  
• Decrease ischemic disease

• Platelet aggregation inhibitor
• Prevents thrombi in cats, not permanent like aspirin.
• Adverse include vomiting and anorexia, give with food.
• watch for bleeding.

• Prevents thrombosis
• Preferentially inhibits Xa (regular heparin inhibits all). 
• Only minimally inhibits thrombin and clotting time, so less risk of hemorrhage
• Must be given SQ (regular IV only)
• Acute emergency, concern of DIC.  
• Enoxaparin (Lovenox), dalteparin (Fragmin)

• Low Molecular weight heparin
• Prevents thrombosis
• Preferentially inhibits Xa (regular heparin inhibits all). 
• Only minimally inhibits thrombin and clotting time, so less risk of hemorrhage
• Must be given SQ (regular IV only)
• Acute emergency, concern of DIC.

• Low Molecular weight heparin
• Prevents thrombosis
• Preferentially inhibits Xa (regular heparin inhibits all).
• Only minimally inhibits thrombin and clotting time, so less risk of hemorrhage
• Must be given SQ (regular IV only)
• Acute emergency, concern of DIC.