Congestive heart failure

11-arid-926Adeel Baig11-arid-927Arkim Mirza

Defination

• Any heart with a reduced ability to contract is considered a failing heart.

• Heart failure and congestive heart failure are medical syndromes in which a dog exhibits signs related to a complex interaction between a failing heart and the blood vessels.

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

• In congestive heart failure, blood dams up in organs—usually the lungs but occasionally in the body's other major organs—and causes the congested organs to function abnormally,

Types of Heart Failure

• systolic myocardial failure

• impedance to cardiac inflow

• pressure overload

• volume overload.

Systolic myocardial failure

• General reduction in the ability of the heart muscle to contract.

• Identified with echocardiography (ultrasonography). There is reduced wall motion during contraction of the ventricles (normal blood flow cannot be maintained)

• Etiology = trauma, infection, drugs or poisons, electric shock, heat stroke, tumors. Some cases have no known cause

impedance (obstruction) to cardiac inflow

• Result in a decrease in blood flow.

• Etiology = external compression of the heart (for example, fluid in the sac surrounding the heart), diastolic dysfunction resulting in a stiff ventricle and reduced ventricular filling, or abnormalities to physical structures of the heart.

Pressure overload

• Result of long-term increases in stress to the heart wall during contraction

• Result from the obstruction of blood flow from the heart or increased blood pressure throughout the body or in the arteries of the lungs.

Volume overload

• Result of any disease that increases volume of blood in the ventricle(s), thus increasing blood flow this can bring on signs of congestive heart failure.

• Diseases = valve disease (for example, degenerative valve disease of the atrioventricularvalves), left-to-right shunts (for example, patent ductus arteriosus, ventricular septal defect), or high-output states (such as those caused by hyperthyroidism or anemia).

Systolic or diastolic dysfunction.

• Heart failure may involve systolic or diastolic dysfunction.

• Diastolic dysfunction = not enough blood is able to fill the heart before pumping.

• Systolic dysfunction = the heart is too weak to pump out enough blood.

• Both conditions lead to poor circulation.

Compensatory Mechanisms

• Specific mechanisms to attempt to normalize functions and offset negative effects disease is having on the body.

• In animal with dilated cardiomyopathy, blood flow is slowed by heart's reduced ability to contract leading to a reduced BP because less blood is pumped with each beat, body compensates by SNS to increase ability of the heart muscle to contract and increase heart rate. These responses increase cardiac output and blood pressure. longterm use of SNS in this way damages heart muscle and other organs.

• Damage again reduces ability of heart muscle to contract leading to cascade of actions, including release of various hormones, that result in another increase in blood volume and blood flow.

cont

• Blood volume can increase as much as 30% in pets with severe congestive heart failure

• progressive heart muscle failure and longtermactivation of these hormones in an effort to normalize blood flow result in continued heart muscle failure.

• Blood flow becomes further compromised with progressive signs of congestive heart failure

Signs of Heart Failure

• Signs depend on causes of heart failure and the heart chamber that is affected.

• Left-sided congestive heart failure = signs associated with a backup of pressure in the vessels delivering blood to the left ventricle. Fluid in the lungs and congestion (coughing, difficulty breathing) are the most common signs.

• Many dogs with left-sided congestive heart failure faint due to lack of blood flow to brain.

• They may also have a low heart rate and low blood pressure and may collapse.

Right-sided congestive heart failure

• Results in increased pressure in the vessels delivering blood to right ventricle and body's veins and capillaries.

• This may cause fluid to build up in the abdomen (ascites), the chest cavity, and the limbs.

Biventricular failure

• Arise when both right and left ventricles are not working properly, such as in dogs with heart muscle failure resulting from dilated cardiomyopathy or poisoning.

• Signs attributable to both forms of congestive heart failure can be noted, although it is common for signs of one to outweigh other.

Treatment

• Treat heart failure in order to improve heart muscle performance

• Control arrhythmias and blood pressure, improve blood flow, and reduce the amount of blood filling the heart before contraction.

• All of these can further damage heart and blood vessels if not controlled. It is also necessary to reduce amount of fluid in lungs, abdomen, or chest cavity.

Drugs

• Specific drugs, dosage, and frequency used vary depending on cause and severity of heart failure and other factors.

• Diuretics are usually prescribed for managing fluid overload in animals.

• Digitalis and digoxin, part of a group of drugs known as positive inotropes, may be used to help heart muscle contract.

• ACE inhibitors ( angiotensin-converting enzyme) and vasodilators can widen blood vessels and thus lower blood pressure.

• Beta-adrenergic blocking drugs (beta-blockers) and calcium channel blockers are helpful in some cases of congestive heart failure.

Nutrition

• Heart failure caused by a deficiency of a nutrient can be treated by supplementation with the missing nutrient.

• This type of heart failure is rare.

Low-sodium diet

• For dogs with severe congestive heart failure that does not respond well to conventional treatment.

• Dogs with mild to moderate congestive heart failure, severe sodium restriction is not needed, but diets high in salt should be avoided.

• Sodium-free snacks should also be given in place of regular treats. Salt should not be restricted in dogs with heart disease that have no sign of congestive heart failure(early activation of certain hormones)

Other Treatments

• Dogs with severe left-sided congestive heart failure and fluid in the lungs (pulmonary edema) may not get enough oxygen. Oxygen can be given by way of an oxygen cage, tight-fitting mask, or nose tube.

Thoracentesis and abdominocentesis

• surgical procedures in which a needle is inserted into the chest cavity or abdomen, respectively, to withdraw excess fluid used to treat dogs with congestive heart failure that have an accumulation of fluid in these areas.

• Can lead to rapid improvement in signs, has no significant adverse effects, and can be performed on a regular basis, if needed.

Bronchodilator treatment

• Reserved for patients with longterm airway disease.

• It is not typically used to treat congestive heart failure exception to this is for dogs that faint as a result of a brief cardiac arrhythmia associated with heart disease such as degenerative valve disease.

Cough suppressants

• Generally not recommended in the treatment of congestive heart failure, because masking signs of cough can worsen the underlying fluid in the lungs. If, however, a dog diagnosed with severe heart disease is coughing, and heart enlargement on chest x-rays shows no fluid in the lungs, the coughing may be caused by the enlarged heart pressing on the airways. Cough suppressants may be helpful for these dogs.