Veterinary care should include diagnostic tests and subsequent treatment recommendations.Diagnosis In-depth
Diagnostic tests are needed to properly diagnose congestive heart failure. Tests may include: Complete medical history and physical examination, with emphasis on stethoscope examination (auscultation) of the heart and lungs. Of particular importance is the identification of abnormal heart sounds such as heart murmurs or irregular heart rhythms (arrhythmia).
A chest radiograph (X-ray) is usually needed to identify heart enlargement, fluid accumulation in the lung and exclude some of the previously mentioned conditions that can mimic heart failure.
The blood pressure is usually measured. This is done with the special device that measures blood flow, noninvasively, through the legs. Both high and low blood pressure values usually need to be identified as either can occur in patients with heart failure.
An electrocardiogram (EKG) is often obtained to identify heart enlargement and determine the electrical activity of the heart. The electrocardiogram is a noninvasive test done by attaching to small contact electrodes to the limbs and body.
Ultrasound examination of the heart (echocardiogram) may be needed for a definitive diagnosis. This is especially true in cats where various forms of heart muscle disease (hypertrophic, restrictive and dilated forms of cardiomyopathy) can lead to heart failure. This noninvasive test requires sophisticated equipment that creates high frequency sound waves much like the sonar of a submarine. An image of the heart is created. The echocardiogram is usually the test of choice to establish the final diagnosis of the cause of congestive heart failure, but this examination may require referral to a specialist.
Laboratory (blood) tests are often recommended to evaluate other organ function, such as the kidney, and exclude anemia as a complicating factor. This can be critical to evaluate the effect of heart failure on other organs such as the kidneys and to monitor the effects of treatment. A blood test to detect heartworm infection may be recommended in some patients.
Your veterinarian may recommend additional diagnostic tests to insure optimal medical care. These are selected on a case-by-case basis. Examples may include:
Specialized blood tests such as blood taurine in cases of dilated cardiomyopathy.
Thyroid tests to exclude abnormal function of the thyroid gland.
Blood cultures in suspected infection of the heart valves.
Doppler studies, which are a special type of echocardiography and often require referral to a specialist. Doppler studies more accurately diagnosed blood flow disturbances.
Thoracocentesis (draining fluid from around the lung) or abdominal paracentesis (draining fluid from the abdominal cavity) may be necessary to provide relief from the excessive fluid and determine the cause of the abnormal fluid accumulation. Tests on the fluid can help determine its cause.
The principles of therapy for congestive heart failure include improving heart function, preventing fluid accumulation, preventing further deterioration of the heart muscle and antagonizing chemicals and hormones produced in excessive quantities in heart failure. Rarely is it possible to treat the heart disease. The most important cause of heart failure in cats is cardiomyopathy (heart muscle disease). Definitive treatment usually requires heart transplantation (not done currently). Heart failure caused by fluid accumulation in the sac around the heart (pericardial effusion) is not treated by drugs but instead requires drainage of the fluid or removal of a portion of the pericardial membrane. Congenital heart defects should be referred to a specialist for management.
Initial treatment for heart failure may require hospitalization with a diuretic, oxygen and other hospital-administered treatments. Vasodilator drugs, such as nitroglycerine or nitroprusside, may be administered. In some forms of heart failure, the use of dobutamine or other potent stimulators of the heart muscle may be necessary. Fluid accumulation around the lungs (pleural effusion) may require drainage with a needle (thoracocentesis).
Treatment usually includes a diuretic ("water-pill") such as the drug furosemide (Lasix). Diuretics prevent the kidney from retaining excessive salt (sodium) and water leading to increased volume of urine is produced. Diuretics are usually prescribed for home care to prevent fluid retention. The dose must be sufficient to prevent fluid retention but, at the same time, cannot be so high as to cause kidney failure or excessive loss of potassium.
Other diuretics may be prescribed in selected patients. For example, spironolactone prevents fluid retention and may protect the heart muscle for further damage in dilated cardiomyopathy.
A potassium supplement may be recommended in some patients, especially in cats with congestive heart failure.
Some patients with chronic heart failure are treated with an angiotensin converting enzyme inhibitor such as enalapril (Enacard) or benazepril. Enalapril, benazepril and related drugs can block some of the harmful hormones that circulate in heart failure, prolong life and reduce clinical symptoms in heart failure. This class of drug treatment, sometimes called ACE-inhibitors, prevents salt retention as well. Dosing is critical as these drugs can excessively lower blood pressure or lead to kidney failure.
The diet may be modified to limit sodium intake and prevent fluid retention. There are specialized diets available for this purpose though some senior diets are also relatively low in sodium.
The drug digoxin (Lanoxin; Cardoxin) is prescribed in some patients. The dose of this drug must be critically determined to prevent side effects such as loss of appetite and vomiting.
Dietary supplements are used in some forms of cardiomyopathy. The amino acid taurine is sometimes prescribed for cardiomyopathy. L-carnitine is sometimes recommended for treatment of dilated cardiomyopathy.
Special treatments are needed for some causes of heart failure. Antiarrhythmic drugs are used to control the heart rhythm. Beta-blockers, such as metoprolol, propranolol or atenolol, may be prescribed to control heart rate, to control arrhythmias and protect the heart muscle. Calcium channel blockers, such as the drug diltiazem or amlodipine, are used in some circumstances. For example, diltiazem is often prescribed to cats with heart failure caused by hypertrophic cardiomyopathy. There are special circumstances for the recommendation of these treatments and the use of some of these drugs is best guided by a specialist.