Q: We were told during our last vet visit that our pet has a heart murmur. Why have we never been told this before? We have taken him there for years. What can we do now and how will this affect his health in the future?A: All mammals have hearts that have four chambers. Each chamber has a valve that closes when the heart beats to prevent blood flowing in the wrong direction. A murmur is a sound heard through a stethoscope when blood leaks past one or more of the valves. Some murmurs are present at birth and some develop over time. For a veterinarian (or medical doctor) to hear a murmur, it must be loud enough for our ears to detect it. Some people hear better than others, and some murmurs become progressively louder over time. Murmurs can also be louder depending on a pet's heart rate and degree of relaxation or nervousness. Panting or rapid breathing can also make murmurs hard to hear. There are several factors that determine how a murmur affects a pet's health. Which valve is affected, the severity of the leak, how the heart responds to the leak, and other illnesses in the body are a few examples. Clinical signs can range from no effect on daily activity to severe respiratory and circulatory problems even when resting. The first thing we usually do when we hear a murmur is gather information so we can decide if any treatment is necessary. The most common procedures that are considered are chest X-rays, heart ultrasound, and electrocardiogram. White and red cell counts, chemistries, urinalysis and blood pressure are often also evaluated to screen for other underlying problems. Treatments vary widely depending on how severe the clinical signs are and how the heart is changing in response to the murmur. Medication can lower blood pressure, decrease the heart rate and increase the strength of the contractions, among other things. We are also fortunate that there are veterinary cardiologists available. They can offer another level of expertise and treatment options.There is no need to panic when a pet is diagnosed with a heart murmur. We just need to determine how the murmur is affecting the pet. Then we can find treatment options that work for both the pet and their owner.