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Heart Failure

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Department of Veterinary Medicine

Bihar Veterinary College, Patna

(Bihar Animal Sciences University, Patna)

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By

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Dr. Pallav Shekhar

Asstt. Professor

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Heart Failure

• Heart failure is not a specific disease.

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•  It is a syndrome in which severe dysfunction results in failure of the cardiovascular system to maintain adequate blood circulation. 

•  Heart failure, the blood flow is insufficient to supply organs with enough oxygenated blood for proper function.

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• Depending on the degree of severity, signs of heart failure may appear while the dog is at rest.

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• During mild exertion,

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•  during moderate or extreme exercise.

Heart Failure

• Chronic Heart Failure

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• Acute Heart Failure

Chronic Heart Failure

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• Heart failure is the most common clinical presentation of dogs and cats with heart disease.

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• Congestive heart failure (CHF) implies that there is a damming back of blood behind the failing heart, into the pulmonary or systemic circulations.

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• Congestive heart failure is a sequel to many of the various causes of heart failure

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Etiology

• Valvular disease

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• Endocarditis resulting in either valvular stenosis or valvular insufficiency

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• Congenital valvular defects – most commonly valvular stenosis, Rupture of valve or valve chordae.

• Myocardial disease

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• Myocarditis - bacterial, viral, parasitic or toxic

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• Myocardial degeneration - nutritional

toxic

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• TRP

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• Congenital or hereditary

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Types of CHF

LEFT CONGESTIVE HEART FAILURE

• Left backward failure will result in increased pulmonary venous pressures and ultimately pulmonary oedema.

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• Breathlessness is therefore a very sensitive index of left backward failure.

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RIGHT CONGESTIVE HEART FAILURE

• Right backward failure will result in increased pressure in the vena cava, jugular distension, liver congestion, ascites and pleural effusion.

Right Congestive Heart Failure

• The right atrium receives systemic and cardiac venous and lymphatic drainage via the cranial and caudal vena cavae and the coronary sinus.

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• Right atrial pressure increases as right heart disease worsens due to diseases such as tricuspid valve insufficiency and pulmonary hypertension

Backward Failure

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• Backward (congestive) failure refers to the damming back of blood behind the failing heart.

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Backward Failure

Clinical Signs

• Distended Jugular Vein

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• Pleural effusion

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• Hepatomegaly

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• Ascites

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Forward Failure

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• Forward failure refers to the inability of the heart to pump blood in a forward direction, i.e. out through the aorta. This results in a reduction in systemic blood pressure, which acts as the primary stimulus to inciting the reflex compensatory mechanisms

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Clinical finding Pathophysiological mechanism

Exercise intolerance Poor muscle perfusion

Pale mucous membranes and cold extremities

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Peripheral vasoconstriction

(sympathetic and angiotensin activation)

Tachycardia Sympathetic activation

Weak femoral pulses (most marked with the systolic failure seen in dilated cardiomyopathy)

Poor left ventricular contractility

and reduced stroke volume

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Elevated blood urea and creatinine, and oliguria Poor renal perfusion

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Increased thirst Angiotensin II stimulation

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• Left backward failure will result in increased pulmonary venous pressures and ultimately pulmonary oedema.

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• Breathlessness is therefore a very sensitive index of left backward failure.

LEFT HEART FAILURE

Foreward Failure

Clinical Signs

• Mainly pulmonary components, which on exertion causes
• Cough
• Paroxysmal dyspnea or cardiac asthma
• Cyanosis
• Hemoptysis
• Varying degrees of pulmonary edema

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Diagnosis

• History

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• Clinical Signs

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• Physical Examination SRR

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• ECG

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• X ray

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• Echocardiography

Treatment

1. Reduce cardiac work

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• Reduce excessive volume overload (preload) and cardiac dilation

(3) Improve cardiac efficiency

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Reduce cardiac Work

• Rest
• Cardiac work can be reduced by rest, reducing arterial pressure (afterload) by counteracting the excessive vasoconstriction and reducing the filling pressure (preload).

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• Arterial and venous pressures can be reduced by the use of vasodilator drugs, e.g. hydralazine, nitroglycerine (glyceryl trinitrate), enalapril or benazepril.

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• Preload is also reduced by reducing the volume overload, e.g. by diuresis.

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Vasodilators

• Vasodilators exert a positive effect in CHF through dilating systemic arterioles and Veins

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• Nitrates( Nitroglycerin, Sodium nitroprusside):

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• Dramatically reduce Preload and after load

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• Sodium nitroprusside is used as 5mcg/kg/hr

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• Amlodipine(Calcium Channel Blockers)

Eg; Atenolol: 6.25-12.5mg/kg/day

Reducing Volume Overload

• These can be reduced by cutting sodium intake, e.g. low salt diets, diuresis and inhibition of angiotensin converting enzyme (thus production of angiotensin II and aldosterone)

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• ACE inhibitor
• Enalapril 0.5mg/kg orally twice

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• Benazepril 0.25mg-0.5mg/kg/day

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Diuretics

• Useful in Oedema and Effusion in HF.

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• Loop Diuretics

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• Furosemide

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• IV onset of action is 5 min, oral 60 min

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• Emergency treatment of Pulmonary edema require high doses IV or IM 4-8mg/kg for dogs and 2-4mg/kg for cats.

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• Spironolactone: 1-3 mg/kg body Wt. one or twice

Improving myocardial efficiency

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• Improving myocardial efficiency may be attempted with

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• Positive inotropic drugs.

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• Positive lusitropes

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• Antiarrhthymics

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Positive inotropes

• Pimobendan: AV valve insufficiency and DCM
• 0.2-0.3mg/kg body wt bid

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• Digoxin: Weak positive inotropes
• 0.003-0.005mg/kg body weight