Prevalence and Clinical Significance of Heart Murmurs Detected on Cardiac Auscultation in 856 Cats

SIMPLE SUMMARY: Heart murmurs are a common finding in cats and, in many cases, the presence of an audible murmur on cardiac auscultation does not necessarily imply the presence of an underlying heart disease. Several studies have been published in the past to address the prevalence and clinical significance of heart murmurs in cats, but very few have looked into the exact origin of the blood flow turbulence responsible for this finding. We retrospectively reviewed clinical records and echocardiographic examinations of 856 cats with heart murmur and found that the majority of murmurs are caused by systolic anterior motion of the mitral valve (SAM) (39.2%) and dynamic right ventricular outflow tract obstruction (DRVOTO) (32%). These causes of murmur do not appear associated with a structural cardiac abnormality in 56.1% (SAM) and 85.0% (DRVOTO) of murmurs. This study also demonstrated that some heart murmur characteristics (timing, intensity and location) can occasionally discriminate between normal cats and cats with underlying heart disease, with the exception of loud and palpable murmurs, which are inevitably associated with significant cardiac abnormalities. However, since the majority of heart murmurs in cats appear to be systolic and mild–moderate in loudness, echocardiography should always be considered following identification of a heart murmur on physical examination in cats. ABSTRACT: Background: Cardiac auscultation is one of the most important clinical tools to identify patients with a potential heart disease. Although several publications have reported the prevalence of murmurs in cats, little information is available in relation to the exact origin of the blood flow turbulences responsible for these murmurs. The aim of this study was to determine the prevalence and clinical significance of murmurs detected during physical examination in cats. Methods: Retrospective evaluation of clinical records and echocardiographic examinations performed in cats for investigation of heart murmurs; Results: Records of 856 cats with full clinical information were available for review. The cause of murmur was identified in 93.1% of cases (72.3% with single blood flow turbulence, 26.4% with two, and 1.3% with three identifiable sources of murmur). Systolic anterior motion of the mitral valve (SAM) was the primary cause of murmur in this population (39.2%), followed by dynamic right ventricular outflow tract obstruction (DRVOTO) (32%) and flow murmurs (6.9%). Most cats with a murmur (56.7%) did not present any structural cardiac abnormality. Conclusions: This study indicates that some heart murmur characteristics (timing, loudness and point of maximal intensity) can potentially predict the presence of an underlying cardiac disease.