Ventricular Septal Defect – 3 month old male Domestic Shorthair Kitten
- enquiries16342
- Apr 8
- 2 min read
By Dr Christine Baker, March 2025
History: A 3 month old kitten was presented for echocardiography after a grade IV/VI systolic heart murmur was noted at vaccination.
Findings: A jet of turbulent, high velocity flow was visualised in systole, flowing from the left ventricular outflow tract just ventral to the aortic valve, into the right ventricle just ventral to the tricuspid valve. This flow was visible on both right parasternal short and long axis views, consistent with a perimembranous, left-to-right shunting ventricular septal defect (VSD). The velocity of the flow through the VSD was 4.75 m/s (normal 4-5m/s) consistent with a restrictive (small) VSD. There was no significant enlargement of any chambers of the heart, and no other congenital cardiac defects identified.
Comments: Ventricular septal defects are the most common type of congenital cardiac defect in cats. They are generally classified based on their location, with perimembranous being the most common location (between the left ventricular outflow tract and right ventricle, just below the level of the aortic and tricuspid valve leaflets). Small (restrictive) defects maintain the normal pressure gradient between the left and right ventricles, and do not generally cause significant cardiac remodelling or clinical signs. Typically they do not require any treatment. In this case as the defect currently appears small the prognosis is likely to be good, but given the young age of this patient a repeat echocardiogram was recommended to reassess the findings within 6-9 months.
At the repeat examination, findings were very similar with no evidence of left atrial or ventricular dilation and the defect was still restrictive, suggesting a good long term prognosis. Larger (non-restrictive) defects have the potential to cause left congestive heart failure or pulmonary hypertension and shunt reversal (Eisenmenger’s syndrome), which can result in generalised cyanosis and polycythemia. While interventional procedures are occasionally possible for large left-to-right shunting VSD, often surgical options are limited (due to patient size and/or defect location) and treatment for large defects is often palliative, aiming to manage left congestive heart failure, or in the case of reversed VSD, management of polycythemia and pulmonary hypertension. Cats with congenital heart disease can often present with multiple defects (such as Tetralogy of Fallot) so complete echocardiography is important for diagnosis and prognostication, and in some cases referral to a veterinary cardiologist may be recommended for complex cases.
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