What is an “Innocent” or “Functional” or “Benign” or “Normal” Heart Murmur?
Low-grade heart murmurs of 1-3/6 are a common finding during the physical development of 50-75% or more (99% is likely more accurate) of normal, healthy kittens. 99% of murmurs are considered to be innocent or functional and completely normal. Therefore they are considered clinically insignificant. Murmurs are usually normal noises or sounds that can be heard as the blood is moving through the chambers of the heart. They can be audible at one point in time and then inaudible at another. Innocent murmurs also may disappear and then reappear. Most innocent murmurs disappear when a kitten reaches adulthood, but some adults still have them. When a kitten’s heart rate changes, such as during excitement or fear, the innocent murmurs may become louder or softer. This still doesn’t mean that the murmur is abnormal. This situation is common in a veterinarian’s office and is referred to as the “white coat syndrome” which causes the kitten’s heart to behave differently under stress. As in childre
