By Dr. Tiffany Hughes
Emergency Intern
You bring your pet in to see your veterinarian for their annual wellness visit and everything seems to be going well. After listening to your pet’s heart during the exam, they inform you that Fluffy has a heart murmur. What is a heart murmur and what does this mean for your pet?
Our pet’s hearts are structured very similarly to our own. They have 4 chambers separated by valves that control the flow of blood through the heart. The right side of the heart collects blood from the body and sends it to the lungs for oxygenation. The left side of the heart collects oxygenated blood from the lungs and sends it to the rest of the body.
Heart murmurs are additional, abnormal sounds outside the “lub-dub” or “boom-boom” you think of when you think of a heartbeat. Blood flowing through the heart should be smooth, but when there is turbulence in this flow is when we hear a murmur. Often the location of the murmur can tell us about its underlying cause. Not all murmurs mean your pet has heart disease, but it is often the first sign that is noticed with heart disease.
In smaller dogs, the most common murmur develops in middle aged to older animals and originates from an abnormal or damaged valve. Age related changes to the valve cause it to become thickened and nodular and allows leakage of blood when closed. This abnormal leakage of blood causes turbulence and the murmur that we hear. Over time, this abnormal leakage of blood can lead to heart enlargement and even heart failure, where fluid develops in the lungs. Heart failure, such as in this scenario, will present as sudden onset of difficulty breathing, collapse, or even sudden death. Often, the first sign pet owners will notice prior to the onset of serious failure is coughing, particularly at night.
In larger dogs, murmurs are sometimes associated with a condition called dilated cardiomyopathy. This is where the chamber enlarges while the muscle thins and becomes weakened. Eventually the heart is not strong enough to push enough blood through the body. This process can occur in both sides of the heart but the left side is most common. This leads to left sided congestive heart failure, difficulty breathing, and death. If the disease is right sided, blood backs up in the rest of the body and fluid builds up in the abdomen or chest.
In young animals, murmurs can indicate developmental problems or structural problems that may require surgery to fix. This is especially true of loud murmurs in young animals. Soft murmurs may resolve as they age, but if persistent may indicate a problem.
Cats tend to be trickier with their heart disease. Cats can have severe heart disease and not have an audible murmur at all or they can have a murmur and no heart disease. Cats can develop a heart condition called hypertrophic cardiomyopathy where their heart muscle thickens and the chamber size becomes much smaller. Cats with heart disease can develop congestive heart failure like dogs and develop sudden respiratory distress. However, cats with heart disease are also prone to throwing blood clots to their legs, especially their back legs, causing sudden paralysis and pain.
If a heart murmur is found in your animal, your veterinarian will likely recommend chest x-rays to evaluate the heart. Chest x-rays allow us to assess overall heart size and for specific chamber enlargement. They also allow us to assess the vessels of the lungs for impending onset of heart failure or for the presence of fluid in the lungs.
The ultimate diagnostic for heart disease is an ultrasound of the heart called an echocardiogram. This is most often done by veterinary cardiologists. Echocardiograms allow for more a detailed assessment of the heart and can assess for the severity of heart disease. Often, an echocardiogram is the only modality that can evaluate the extent of heart disease in a cat since their hearts tend to not show obvious changes on x-rays.
There are many causes of murmurs and the diseases listed above are only a selection of the most common. Unfortunately, there is no medication that treats or fixes a murmur. There are medications that can help reduce the work on the heart, if failure is imminent or has already occurred. Knowing the extent of disease is important by performing x-rays or echocardiography, in order to more closely monitor our pets for the onset of heart failure. The more quickly the onset is recognized the more likely it is that we can treat them appropriately before it becomes life-threatening.
Dr. Tiffany Hughes is an Emergency Intern at Aspen Meadow Veterinary Specialists. AMVS is a 24-hour veterinary facility providing specialty internal medicine, orthopedic surgery, oncology, neurology, emergency, critical care, and pain management. They are located in Longmont at 104 S. Main St. For more information, go to www.AspenMeadowVet.com [1].