In congestive heart failure, the heart is no longer able to provide blood with adequate oxygen to supply the body.
Without adequate oxygen, the body's cells become desperate and trigger a series of responses. Various hormones are released by several organs in an attempt to correct the problem. These hormones conserve and retain fluids in an effort to increase blood volume and the output of blood.
For several months, these compensatory responses help the situation. However, increased fluid retention eventually becomes harmful. More and more fluid leaks out of the capillaries, causing increased gagging and coughing, and reduced stamina. Fluid in the lungs is called pulmonary edema, fluid below the skin is called peripheral or limb edema, and fluid in the abdomen is called ascites. Peripheral or limb edema is much less common in dogs than in people with congestive heart failure.
Dogs in the later stages of congestive heart failure become much less active and tire easily. Their appetite usually falls of and they show signs of difficult respiration, panting and coughing while at rest. Their tummy enlarges and takes on a pear-shape as fluid accumulates in the liver and abdomen. Electrocardiograms taken of these dogs are always abnormal. When I examine these dogs, the color of the membranes of the mouth are grayish rather than healthy pink and blood vessels on the surface are abnormally congested with blood. These dogs often have a condition called a jugular pulse in which the beating of the heart can be seen in the large jugular veins of the neck. The sounds of heartbeat that I hear through my stethoscope are always abnormal to some degree.
By the time dogs become symptomatic with cardiomyopathy and congestive heart failure, they rarely live beyond a year. Many will die in six months. The disease is known to run in families so families with this problem should not be bred.
Doberman pinchers develop abnormal electrocardiograms up to four years before they develop clinical signs of heart failure. Many of these dogs die suddenly without warning. Owners often think these dogs have been poisoned. Others develop the cough and fluid retention characteristic of the heart failure along with muscle wasting and difficulty getting about.
In Boxers abnormal heart rhythms are often picked up as an incidental finding on routine health exams when no signs of illness are present. Later, the Boxers may have sudden incidents of collapse, fainting and weakness due to this irregular heart beat.
Dilated cardiomyopathy or congestive heart failure develops over many months or even years. Its effects on blood flow also develops slowly. As heart function declines, the body is able to compensate for several weeks or months. However, at some point, the body's ability to compensate is no longer effective. At this point, dogs go into severe heart failure in what appears to be a matter of hours. Rapid, heavy breathing, blue tongue, excessive drooling, or collapse may be the first signs that anything is wrong.
[no information in our database]
Cardiomyopathy responds best to a cocktail of medications. One of the oldest drugs used to treat this condition is digitalis (Digoxin, Cardoxin, Lanoxin). This medication belongs to a group called positive inotropic agents which increase the concentration of calcium in heart muscle cells. This increases the force of cardiac contractions and usually slows heart rate. I begin dogs under forty pounds on 0.0025 to 0.005 mg/pound body weight given twice a day. It takes about five days for the drug to reach stable blood levels and show its effect. Larger dogs are given 0.22mg/m2 of body surface. The drug must be used in caution in dogs with kidney or liver problems. If loss of appetite, vomiting, diarrhea or lethargy occur I lower the dose. One or two weeks after beginning digitalis, I order a blood digoxin test to see if therapeutic levels of the drug are present. Digoxin is eliminated from the dog’s body through the kidneys so dogs with kidney damage are less able to tolerate the drug. In these dogs the dose should be lowered or digitoxin should be used instead because it is metabolized and excreted through the liver.
Another helpful group of drugs for dogs in heart failure are diuretics. These drugs remove accumulation of fluids that occur in the lungs and abdomen of cardiac patients due to the sluggish flow of blood. The most common and best drug of this class is furosemide (Lasix). The dose of furosemide is 1-3mg/pound of body weight given two or three times a day. Dogs taking furosemide usually drink and urinate more frequently. While on this drug the dog should receive a potassium supplement such as Morton’s NuSalt.
Another important group of drugs used in treating dilated cardiomyopathy are blood vessel dilators called ACE inhibitors. These compounds decrease certain chemicals that tighten blood vessels so more blood flows smoothly through them allowing the heart to pump blood more efficiently. The most commonly used drug in this class is enalapril (Enacard, Vasotec, Lotensin, Prinavil, Zestril). I give dogs 0.25mg/pound body weight once or twice a day. Since this drug can cause kidney problems it is wise to have a BUN and creatinine serum level performed two weeks after starting the medication and then every three or four months. When side effects of enalapril occur, they are usually lack of appetite, vomiting and an increase in toxic waste products due to decreased blood flow through the kidney (azotemia).
Two other ACE inhibitors that are occasionally used are captopril (Capoten ® 0.5-1.0 mg three times a day) and benazepril (Lotensin 0.125mg/ pound once a day). Benazepril is recommended when blood tests show an elevated BUN and creatinine, which signifies poor kidney function.
Drugs used to treat heart beat abnormalities (ventricular arrhythmias) include mexiletine (Mexitil,2-4mg/pound three times a day) procainamide (5-10mg/lb every 6 hours) or its long acting form, Procan SR, (5-10mg/lb every 8 hours). Unfortunately this drug and a sister compound, quinidine, often cause depression and lack of appetite. Mexiletine is often given along with atenolol (0.25mg/pound once or twice a day).
Both Hills Prescription Diets (h/D) and Purina’s CNM (CV formula) make low sodium diets for use in dogs with heart disease. A recipe for a low sodium home-cooked diet is included in this series www.2ndchance.info/homemadediets.htm
There have been scientific studies that indicate that a few cases of cardiac failure, particularly in boxers, are due to a deficiency in the amino acid L-carnitine. If tests show an abnormally low carnitine level, supplementing the patient’s diet with this product can halt the disease (110mg/pound twice a day, maximum of 4 grams per day). Because of its expense, it is not usually given unless a deficiency can be documented. Another group of cocker spaniels have been found to develop heart failure when there are deficient in another amino acid, taurine. Since this amino acid is not toxic and inexpensive there is no harm in administrating it to heart patients (500mg twice a day).
In humans, Coenzyme Q supplementation has improved the strength of heart muscle contraction (30-90mg twice a day). We do not yet know if this compound helps dogs in cardiac failure.
[no breeds in our database]
[no information in our database]
