Feline Heart Murmur
A heart murmur is an abnormal heart sound heard when listening to the heart with a stethoscope. It is caused by abnormal blood flow in the heart.
Heart murmurs are graded I-VI (always Roman numerals), based on the severity of the sound. It is important to note that the grade has no direct correlation with the severity of any possible disease process. A grade I/VI murmur is barely audible, while a grade VI/VI is very loud, and can be felt through the chest wall. Murmurs can occur either when the heart is contracting, relaxing or sometimes throughout the cycle.
Sometimes kittens have murmurs and then grow out of them. And sometimes they do not. Adult cats can have what is called an idiopathic murmur, which means that there is no discernable cause, other than perhaps stress causing the disruption in blood flow. There is no way of knowing the cause of a murmur without further diagnostic testing, including electrocardiography, radiography, echocardiography and bloodwork. Some causes of murmurs include, but are not limited to, outflow obstruction, diseased valves, defect in the septum, anemia, hyperthyroidism, HCM, valve stenosis and endocarditis.