Clinical characteristics of cats referred for evaluation of subclinical cardiac murmurs

Abstract

Objectives: The aim of this study was to define the clinical characteristics of cats referred for evaluation of subclinical cardiac murmurs, and, secondarily, to identify predictors of echocardiographic identification of cardiac disease.

Methods: One hundred and sixty-three apparently healthy cats with subclinical murmurs were retrospectively enrolled. Medical records of cats older than 1 year of age referred for the evaluation of subclinical murmurs were reviewed. Cats were considered healthy if clinical signs of systemic disease or cardiac disease were not reported and cats were not receiving cardiac medications. Logistic regression was used to identify clinical variables that predict echocardiographic identification of cardiac disease.

Results: One hundred and eight cats (66.3%) had echocardiographic evidence of cardiac disease with hypertrophic cardiomyopathy being the most common (80.5%). Left atrial enlargement was uncommon; in 90% of cats with echocardiographically identified cardiac disease, the left atrial aortic ratio from two-dimensional echocardiography was <1.51. Cats with cardiac disease were more likely to be male (P = 0.016), weigh more (P <0.01) and have a murmur of intensity ⩾3/6 (P = 0.019) than cats without cardiac disease. Murmur intensity ⩾grade 3/6 (P = 0.01) and male sex (P = 0.01) were independent predictors of echocardiographic evidence of cardiac disease in multivariable analysis.

Conclusions and relevance: The majority of cats referred for evaluation of subclinical cardiac murmurs have cardiac disease. Based on left atrial dimensions, cardiac disease is generally mild. Male sex and a loud cardiac murmur are associated with the identification of cardiac disease.

Keywords: Echocardiography; cardiac disease; left atrium; subclinical murmurs.

Figure 1

Distribution of maximal recorded murmur intensity from 163 apparently healthy cats referred for echocardiographic evaluation of cardiac murmurs

Figure 2

Distribution of flow disturbances inferred from Doppler echocardiographic findings in 96 cats with left ventricular hypertrophy phenotype that had been referred for evaluation of subclinical cardiac murmurs. LVOTO = left ventricular outflow tract obstruction; RVOTO = right ventricular outflow tract obstruction

Figure 3

Box plots of ratios of left atrial dimension and aortic diameter obtained from M-mode (LA:Ao_M; n = 71) and two-dimensional echocardiography (LA:Ao_2D; n = 100) of 108 cats with subclinical cardiac murmurs in which cardiac disease was echocardiographically identified. Both LA:Ao_M and LA:Ao_2D were available for most cases, but, for a few, only one of the ratios was recorded. Each box represents the interquartile range (IQR) and is divided by a line that represents the median value. ‘Whiskers’ represent the value that is most distant from the median but within 1.5 times the IQR from the first or second quartiles. Dots represent single observations greater than or less than the value defined by the ‘whiskers’