Heart Murmurs - An Overview
In young cats, a veterinarian will sometimes hear benign (also termed innocent, functional, or physiological) heart murmurs. They are produced because the young strong heart is beating in close proximity to the chest wall, and therefore the turbulence produced from blood flowing in the heart and large adjacent vessels can be heard.
These murmurs can be identified at the first check up, and may vary in intensity depending on the kitten's health and physical state. Follow up stethoscope exams will track the murmur as the kitten matures. Heart murmurs usually resolve themselves by about six months of age.
Significant murmurs will produce changes in the ECG and other tests, and may hinder the kitten's growth. Some murmurs require surgical and medical therapy. Prognosis depends on type of defect and its severity.
Specific Conditions that May Cause Heart Murmurs
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Mitral valve dysplasia is one of the more common cat conditions. This defect results in a leaky valve and the murmur results from the turbulence of blood reflux.
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Pulmonic stenosis is a narrowing of the outflow area of the pulmonary artery at the exit from the right ventricle of the heart. The murmur reflects the abnormal turbulence that results where the outgoing blood meets resistance.
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Aortic stenosis is a similar narrowing but occurs in the aorta outflow area and the murmur develops for the same reason.
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Ventricular septal defect (VSD) is a hole in the interior wall of the pumping chambers. If the hole is very large, murmurs may actually be absent because lower turbulence occurs.
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Patent ductus arteriosus (PDA) is a lack of closure of a duct in the fetal heart, that will produce shunting of blood in the heart when it remains open after birth. If shunting occurs from the right to the left, murmurs are usually absent. However, in the usual left-to-right side PDA shunt, murmurs can be heard.
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Tetralogy of Fallot is a complex defect affecting more than one segment of the heart and emerging arteries. This murmur is usually a result of pulmonic stenosis.