Atrial Fibrillation (AF) in Dogs Page 2
Diagnosis In-depth of Atrial Fibrillation in Dogs
Diagnostic tests are needed to recognize all AF, and exclude all other diseases. These tests may include: Complete medical history and physical examination Physical examination and examination of the heart and lungs with a stethoscope. This will identify the chaotic rhythm and prompt an electrocardiogram (EKG). The presence of congestive heart failure can also be determined from this examination. An EKG is needed to diagnose the rhythm with certainty and to exclude other electrical disturbances of the heart. This study is done in a manner similar to that used in people. Chest X-rays are important to gauge the size of the heart and detect congestive heart failure. This will appear as fluid accumulation in the lungs, called pulmonary edema, or fluid accumulation in the chest cavity, called pleural effusion. An echocardiogram, or ultrasound of the heart, is needed to diagnosis the underlying heart disease with certainty. This noninvasive, painless examination can display heart size, disease (lesions) and heart muscle function. Serum biochemical tests (blood tests) and a urinalysis should be obtained with special interest directed to kidney function and blood electrolytes. Thyroid function should be measured in dogs receiving supplementation with thyroxine. An heartworm(HW) antigen test should be done if appropriate for geographic area. Your veterinarian may recommend additional diagnostic tests or refer you to a specialist to insure optimal medical care. These are selected on a case-by-case basis.
Treatment In-depth of Atrial Fibrillation in Dogs
The principles of therapy for AF include the following: Control congestive heart failure if present Control the heart rate to prevent excessively rapid heart beats Provide home therapy to slow the progression of heart disease
Initial treatment for heart failure may require hospitalization with administration of a diuretic, oxygen and other treatments. Vasodilator drugs such as nitroglycerine or , which cause dilatation of blood vessels, 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). Additional treatment may include: A diuretic such as the drug furosemide (Lasix®). Diuretics prevent the kidney from retaining excessive salt (sodium) and water leading to increased volume of urine 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. Most patients with atrial fibrillation are treated with an angiotensin converting enzyme inhibitor such as enalapril (Enacard®) or benazepril. Enalapril, benazepril and related drugs block some of the harmful hormones that circulate in heart failure, prolong life and reduce clinical symptoms in canine heart failure. This class of drug treatment, sometimes called ACE-inhibitors, prevents salt retention as well. Dosing is critical as these drugs can lower blood pressure excessively 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. Fish oil supplements may be of value in dogs with weight loss – ask your veterinarian about these. Dietary supplements are used in some forms of cardiomyopathy. The amino acids taurine is sometimes prescribed for cardiomyopathy in spaniel breeds. L-carnitine is sometimes recommended for treatment of dilated cardiomyopathy. Other nutritional supplements such as vitamin E and coenzyme Q10 are recommended by some veterinarians, but there is no evidence of their benefit for heart failure in dogs. The drug digoxin (Lanoxin®, Cardoxin®) is prescribed to improve heart function and reduce the heart rate. The dose of this drug must be critically determined to prevent side effects such as loss of appetite and vomiting. Beta-blockers such as metoprolol, propranolol or atenolol are usually be prescribed to control heart rate, to control arrhythmias and protect the heart muscle in atrial fibrillation, but these must be dosed very carefully – doses must be started low and gradually increased. The calcium channel blocker, diltiazem, is used by some in place of beta-blockers to slow the heart rate. Complications of blood clots are not a big problem in dogs with AF.
Follow-up Care for Dogs with Atrial Fibrillation