Information on the prevalence and cause of heart murmurs in young cats is scarce. This prospective study was performed to investigate prevalence of heart murmurs, and heart disease, and to explore the association between auscultatory and echocardiographic findings in clinically healthy young cats.

Between May 2012 and March 2017, 12,958 healthy cats aged ≤12 months were screened by auscultation by shelter veterinarians in a single animal shelter (RSPCA Yagoona, NSW, Australia). Heart murmurs were detected in 221 (1.7%) cats, which were subsequently within 1 month investigated by a veterinary cardiologist (NB) or cardiology resident (GN). Murmurs were confirmed in 163 cats. Murmur characteristics (timing, grade, point of maximal intensity) were recorded. All but one murmur were systolic. The point of maximum intensity of murmurs was often difficult to localise.

Subsequently transthoracic echocardiography was performed in all 221 cats, after which the murmur was assessed to be pathological or non-pathological. Cats with multiple congenital heart anomalies were classified according to the most severe condition. No efforts were made to differentiate between physiological and innocent murmurs, both were considered non-pathological.

Heart disease was detected in 51 cats (prevalence 0.4% total population). Diagnoses included obstructive (n=19) and non-obstructive (n=6) mitral valve dysplasia, ventricular septal defect (n=15), tricuspid valve dysplasia (n=7), pulmonic stenosis (n=1), double chamber right ventricle (n=1), subvalvular aortic stenosis (n=1), and hypertrophic cardiomyopathy (n=1). The murmur was non-pathological in 170 cats (of which 3 cats had dynamic right ventricular outflow tract obstruction).

Grade 5–6 murmurs (n=5) were all pathological. A positive predictive value of a grade 3–4 murmur being associated with pathological heart disease was 58.9% (CI 48.5% to 68.7%), whilst negative predictive values of grade 0 and grade 1–2 murmurs being associated with non-pathological heart disease were 96.6% (CI 87.0% to 99.1%) and 88.4% (CI 82.1% to 92.6%), respectively.

In conclusion, in this study the prevalence of heart murmurs and heart disease were 1.7% and 0.4%, respectively, with mitral valve dysplasia and ventricular septal defects most commonly diagnosed. Murmur grading was helpful in differentiating non-pathological from pathological heart murmurs.

Disclosures

Disclosures to report.

This study received funding from Australian Pet Welfare Foundation (APWF) Authors: Niek Beijerink Speaking & Consultancies: Boehringer Ingelheim, Elanco Animal Health, Bova Compounding, CEVA Animal Health, Blackmores, Grants/Research: Luoda Pharma.