When using a stethoscope to listen to an animal's heart, a veterinarian assesses many characteristics including:
The heart rate – how many beats per second.
The heart rhythm – if the beats are evenly spaced.
The heart sounds – which reflect the movement of blood through the heart and vibrations of the heart and vessels.
Normally, when listening to the heart, there are two major heart sounds in a sequence that sound similar to: lub-dup, lub-dup, lub-dup… Extra sounds may be heard and some of these are termed murmurs. Murmurs are caused by turbulent blood flow through the heart and vessels, and there are several types:
Physiologic: Due to certain body conditions such as anemia or fever.
Innocent: No known cause and no identifiable heart problem.
Pathologic: Due to problems with the vessels and heart, including heart valves and heart muscle.
Researchers at the Angell Memorial Animal Hospital in Boston did a study to determine how common murmurs were in apparently healthy cats. Over 100 cats from 1-9 years of age that were brought to the Hospital as possible blood donors were examined. These cats were recruited through notices placed within the Hospital and through media coverage in the New England area. Each cat was examined by a veterinary specialist.
Out of 103 apparently healthy cats ultimately included in the study, 22 (21%) had heart murmurs. Seven of these cats were examined with echocardiography; one had normal results, and the other six showed signs of heart disease. Hypertrophic cardiomyopathy, in which the heart muscle becomes thicker and restricts blood flow, was the most common cause.
The researchers suggest that heart murmurs in apparently healthy cats are common and that hypertrophic cardiomyopathy in the general cat population is more common than previously reported. This underscores the need for regular physical examinations to identify potential problems earlier, and the need for complete exams prior to anesthesia or prescribing medications that may influence the heart.