You have your pet in for a routine physical examination and suddenly the expression on the vet’s face becomes much more intent as they listen to your pet’s heart and lungs with their stethoscope. Veterinarians listen to how fast the heart beats, for sounds such as murmurs, and for fluid sounds in the lungs that shouldn’t be there.
Murmurs are sounds created by turbulence of the liquid, blood, moving through the tubes and valves of the heart. Sounds are symptoms; a sound is not a diagnosis. If a murmur is investigated and found to be of no consequence it is called an innocent murmur.
If your dog is a very young puppy it could simply be a murmur because the normal hole, which exists between the chambers of a fetus’ heart, hasn’t closed yet. The veterinarian may just recommend making a note of it and checking the puppy in a few weeks. In older dogs and cats, blood work to check for various diseases, an electrocardiogram (ECG), and radiographs (x-rays) to see the size and shape of the heart and to see fluid in the lungs are recommended. Your veterinarian may recommend referral to a specialist for a cardiac ultrasound to visualize the internal mechanics of the heart. A pet may be referred to a cardiologist, who specializes in heart disease.
Your pet’s heart rate is measured in beats per minute. A heart rate that is too fast is called tachycardia; too slow is called bradycardia. What your pet’s normal heart rate has been in the past is very valuable information, as not every pet’s heart rate falls within normal limits.
I once examined an older cat and her heart rate was 62. Normal for a cat is about 160 to 180 beats per minute and 164 had been recorded for this cat all her life. She had developed a mass in her throat which was irritating her vagal nerve and causing the heart rate to slow. The problem wasn’t at the heart at all. Thyroid disease can disrupt a normal heart rate and cause a murmur. Anemia can cause a murmur.
Many years ago, I had a client who took his Doberman out to exercise by chasing his truck (A horrible idea!). The dog came to my clinic with a heart rate of 240 which a dog cannot live long with. This dog had developed atrial fibrillation because of a developing disease of the heart muscle and the crisis was triggered by the extreme exercise. We treated this dog with drugs to convert his heart back to a normal rate of about 100 and subsequently referred him to a cardiologist who treated him for about two years before he succumbed to his heart disease.
More than once tachycardia in a big dog with decreased energy and otherwise a normal physical examination has led me to diagnose a tumor of the right atrium of the heart called a hemangiosarcoma. These tumors often start to bleed into the pericardial sac around the heart and the heart starts beating fast because it can’t expand properly when the bag around the heart is filling with blood. Taurine deficient diets can cause life threatening diseases of the heart with abnormal heart rhythms.
This article is but a tiny window on the myriad of diseases that can change the sound or rate of a heart beating. Once a specific diagnosis is made a veterinarian will discuss treatment options and prognosis with the pet owner. It is critical to have your pet examined annually and the physical examination is the keystone to any preventative health care program.
