Ron Hines DVM PhD
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Like all mammals, dogs and cats have a four-chambered heart. It consisting of a left and right upper chambered atrium and a left and right lower chambered ventricle. The left and right atria receive blood from the lungs and body respectively. The left ventricle is responsible for pumping oxygen-rich blood from the lungs out through the aorta into the body, while the right ventricle pumps the blood through the pulmonary artery to the lungs for oxygen.
The Heart’s Four Valves:
The heart has 4 one-way vales to keep blood flowing in the right direction. Because heart valves are fragile structures in constant motion, it is not uncommon for them to develop opening and closing issues as your dog or cat ages. The valve between the left atrium and ventricle is the mitral valve. The one between the right atrium and ventricle is the tricuspid valve. The one regulating blood passage into the aorta is the aortic valve and the one regulating blood going to your pet’s lungs is the pulmonary valve. The mitral valve is the most fragile of these four valves in your pet’s heart. In dogs, it is often the first one to wear out. In us humans, it is the aortic valve that causes the most problems.
What Signs Will I See If My Pet Has A Heart Problem?
The first sign that most owners notice is a cough. Coughs begin because enlarged, failing hearts allow fluid to pool in the lungs an also press on the wind pipe (trachea) – a structure just above the heart. Other signs you might notice in your cat or dog are earlier tiredness after activity, rapid breathing, poor appetite, an enlarged tummy (abdominal ascities), pale, “muddy” or bluish gums, and a rapid, weak pulse. Fainting is much less common.
What Might My Veterinarian Hear Through A Stethoscope?
Many of these pets have heart murmurs. Heart murmurs come about when a passage through the heart becomes too narrow or too wide or when a pet develops substantial anemia that changes its blood consistency. In middle aged and older adult cats and dogs, heart murmurs usually mean that a valve is not working properly. In younger dogs and cats they can be a sign of an imperfectly constructed heart (a cardiac birth defect). The particular valve producing the sound may not be closing completely or it may not be opening sufficiently for blood to pass through it without turbulence. Turbulence as blood rushes through an abnormal heart valve or channel is what produces all heart murmur sounds. The rhythm of a weakened heart also likely to changes. But unlike in us humans, frequent changes in the heart rhythm of relaxed dogs and cats is quite normal (sinus arrhythmia). Read about sinus arrhythmia here.
What Tests Might My Veterinarian Suggest?
If your veterinarian is suspicious that your dog or cat might have a heart problem, the first test we traditionally schedule are chest (thoracic) x-rays. We need two views to start with, one side to side (lateral) and the other bottom to top (DV/dorsoventral view). If your pet’s x-rays shows an enlarged heart, your veterinarian might be satisfied with that, begin therapy or offer you a consult with a formally trained veterinary cardiologist. If the radiographs are inconclusive or for backup evidence, your veterinarian might suggest aproBNP or similar blood test (Cardio-BNP Test, NT-proBNP, B-type natriuretic peptide yield similar information). These tests are especially useful in cats when your veterinarian is not sure if your cat has a heart problem or if it might be a lung problem or asthma. Another tests that a cardiac specialist might perform is echocardiograph (doppler ultrasound) to see your dog or cat’s heart perform in real time, and an ECG/EKG to check if the electrical system of your pet’s heart is functioning normally.
What Are Some Of The Effects Of A Failing Heart?
As I mentioned, in dogs, the valves are often the first heart structures that are affected. Heart disease in cats more commonly involves the entire heart muscle – not just the valves.
Dogs let us know early on that there is a problem