Heart Disease in Dogs
Heart disease in dogs may be either congenital (present at birth) or acquired. Congenital heart problems are varied, and depending on the severity, the problem may not become apparent for years. Acquired disease also varies in type and severity. Heart disease may be initially only detected based on auscultation (listening) of heart sounds upon regular examination. Heart changes may be detected from the auscultation of a heart murmur (abnormal sound), rhythm abnormality, or other related physical abnormalities. Other times, the dog may be showing clinical signs of heart disease that leads to a veterinary exam. Once heart disease is detected certain information obtained from diagnostic blood work, urinalysis, X-rays, ultrasound and blood pressure measurements will allow proper treatment to be started. Depending upon initial presentation and other restrictions, basic treatment may be initiated to stabilize the patient. In many cases, both heart and lung disease is present in the same pet. Heart disease can lead to lung problems, and lung problems can lead to heart disease. For instance, asthmatic cats may eventually develop cardiac failure.
The heart in dogs has two sides, just like in people. The right side of the heart has blood that is delivered from the body, and is pumped to the lungs. The left side of the heart has blood delivered from the lungs and is pumped to the body. Each side of the heart has two chambers, the initial chamber, is a collection chamber, the second chamber pushes, or pumps the blood to its destination. There are one-way valves that separate the two chambers on each side and another one-way valve that separates the second chamber from the vessels where the blood leaves the heart. Blood is supposed to only go in one way, and out the other. If a valve is not working of if the muscle is too flabby to close the valves, blood may start going back and forth from one chamber to the other. Murmurs are the noise produced when blood flows abnormally, and/or a valve is not functioning properly. Murmurs are graded by how easy they are to detect, from 1-6 with 6 being the worst/loudest. In general, acquired murmurs get worse as the condition worsens. There are characteristics of certain types of murmurs that give us an indication of what is causing the murmur/ heart disease.
If the left side of the heart is not functioning properly, the blood (which has come from the lungs) backs up. This increases the pressure of the blood in the lung vessels. When this pressure is strong enough, fluid will leak out of the lung vessels and enter into the lung tissues and airways. This is called pulmonary edema and is a life threatening condition. However, it may start and be a mild condition for a long time.
If the right side of the heart is not functioning properly, the blood (which has come from the body) backs up. Much of this blood has come from the abdomen and liver. This increases the blood pressure, including the pressure in the vessels coming from the liver. This can eventually cause problems with the liver. Excess fluid may be shed into the abdomen, a condition we call ascites. Ascites is not desire able, and can cause other problems, but is not immediately life threatening except in severe cases.
Once heart disease is suspected, a thorough physical examination, laboratory tests for blood and urine, chest and abdominal radiographs (x-rays), blood pressure evaluation and electrocardiograms may be necessary to devise a proper treatment program and echocardiography (ultrasound) is recommended. If your pet is not showing clinical signs of heart disease and a change is only detected during regular annual exam, you may elect to wait on these services but a follow up exam should be completed at least every 6 months. It is important to recognize, that heart disease is usually progressive and starting treatment may delay clinical signs. If heart disease is suspected, your pet will need special evaluation prior to anesthesia. Additionally, if heart disease is detected, good oral hygiene is important to help prevent further insult to the heart, lungs, liver and kidneys.
The following are some types of heart problems in dogs.
Cardiac arrhythmias are disturbances in the rate or rhythm of the heartbeat. There are many types of arrhythmias, and their consequences vary from mild to life-threatening. The causes of most arrhythmias are unknown.
Congestive Heart Failure
Congestive heart failure can result from heart-valve disease, heartworm infection, heart defects present at birth or other heart conditions. Congestive heart failure occurs when the heart does not pump enough blood to meet normal body needs. Pets with congestive heart failure tire easily, are short of breath, and cough deeply due to poor circulation through the lungs. They may actually lose weight, but the abdomen may enlarge due to fluid accumulation. The legs may also be swollen and puffy. Often these patients faint or collapse after excitement or exertion, and the tongue appears bluish-gray. Although congestive heart failure cannot be cured, many patients can continue to live a comfortable life with proper medical management. Treatment is aimed at removing accumulated fluids, improving the heart's pumping efficiency, and decreasing the heart's workload.
Dilative (Congestive) Cardiomyopathy
Dilative cardiomyopathy is the most common heart muscle disorder of dogs and usually affects large-breed dogs over 3 years of age. The heart muscle becomes severely weakened, and the heart enlarges (dilates). Enlargement of the heart reduces efficiency of the pumping action and results in heart failure.
Although the cause of primary dilative cardiomyopathy is unknown, some cases are due to muscle damage from infections, toxic substances, other diseases, or deficiencies of the amino acid L-carnitine.
Dilative cardiomyopathy is a very serious condition. Although some affected dogs have survived 2 or more years, the overall average survival time is only 6 months.
Endocarditis is an inflammation of the lining of the heart and/or the valves of the heart. Usually it is caused by an infection in another part of the body, such as the teeth, tonsils, anal sacs, or kidneys. This infection reaches the heart through the bloodstream.
Endocarditis is a serious disease and may cause death. Blood clots may develop and further complicate an already serious condition. Treatment for endocarditis is designed to eliminate infection. The severity of the condition and involvement of other parts of the body dictate whether hospitalization is necessary and the type of treatment used.
The heart valves are one-way valves that allow blood to flow in one direction only (through the heart). If a valve does not close (valvular insufficiency), blood flows out of and then back into the heart. Valvular insufficiency may be present at birth (congenital) or can occur later because of disease.
It may affect the right, left, or both sides of the heart. Signs of left-sided heart failure include difficult breathing, coughing, and decreased stamina. With right-sided heart failure, signs include decreased appetite, weight loss, gradual abdominal enlargement, occasional vomiting and diarrhea, and swollen limbs. In many cases, signs of both right and left heart failure are present. Many cases of valvular insufficiency can be successfully controlled for long periods with medication. Important points in treatment
1. Extensive laboratory tests, including blood cultures, are used to diagnose the condition and assess the response to treatment. Repeated cardiac examinations, including electrocardiograms and radiographs (x-rays), are often necessary to evaluate your pet's response to treatment. Treatment may be necessary for the rest of your pet's life.
2. Medication: Medication must be given in exact amounts and on time, especially for patients receiving digitalis, digitalis derivatives or drugs used in controlling arrhythmias. Please call the doctor if you cannot give the medication as directed or don't know when to administer the drugs.
3. Patients receiving diuretics (water pills, lasix, furosemide, disal) experience increased urgency to urinate. If your pet must be alone for long periods, discuss this problem with the doctor.
4. Activity: Allowable exercise varies with the severity of the disease. Follow the instructions checked.
q Allow normal activity.
q Limit your pet's activity to short on-leash walks until the doctor allows more vigorous activity.
q Your pet's activity must be severely restricted. No running, jumping, rough playing, or ball chasing is allowed. Avoid situations that result in extreme excitement or extended barking.
5. Diet: Follow the instructions checked.
Feed the normal diet.
A low-sodium (low-salt) diet is an important part of treatment, Feed Prescription Diet h/d.
Notify the Doctor if Any of the Following Occur
Your pet's condition worsens or new problems develop.
Your pet refuses to eat the recommended diet.
You cannot give the medication as directed.
Your pet passes out or has a seizure or convulsion.
Your pet becomes lethargic.
Your pet vomits or has diarrhea.
Your pet refuses to eat.
Your pet continues to cough.
Your pet develops a limp or is reluctant to move.
Blood appears in your pet's urine or feces.
Your pet develops a swollen abdomen.
Your pet's general health appears to be deteriorating.