Prevalence and diagnostic characteristics of non-clinical mitral regurgitation murmurs in North American Whippets

Abstract

Objectives: To assess the prevalence of functional ejection murmurs and murmurs of mitral regurgitation (MR) due to myxomatous mitral valve disease in healthy whippets; to assess the diagnostic value of auscultation to detect MR; and investigate the relationship between age and presence of echocardiographically documented MR (MR_echo).

Animals: A total of 200 healthy client-owned Whippets, recruited at national shows between 2005 and 2009 were involved in this study.

Methods: Cross-sectional study. Dogs were examined by auscultation by one examiner and Doppler echocardiography by another, and results were compared. Prevalence of types of murmurs and MR_echo were calculated and correlated to age. Accuracy of auscultation to predict MR_echo was calculated.

Results: Left-sided systolic heart murmurs were detected in 185/200 (93%) of dogs. Left apical systolic murmurs (L_apex) were detected in 57/200 (29%) and left basilar systolic murmurs (L_base) in 128/200 of the dogs (64%). MR_echo was present in 76/200 (38%) dogs. Prevalence MR_echo was correlated with age (r = 0.96, p=0.0028). Mitral regurgitation detected by echocardiography was present in 12/78 (15%) of the dogs ≤ 2 years of age and in 59% of the dogs at 7-8 years old. Detection of L_apex predicted MR_echo with sensitivity 65%, specificity 94%, positive predictive value 86%, and negative predictive value 81%; and accuracy improved when only dogs with more intense L_apex (grade ≥ 3/6) were considered.

Conclusions: Systolic murmurs are common in North American Whippets and this breed exhibits a high prevalence of MR_echo, which may be documented at a relatively early age. Whippets with non-clinical MR_echo may not be identifiable by auscultation alone; echocardiographic examination may be required to exclude a diagnosis of MR. Louder heart murmurs allow more accurate localization in this population.

Keywords: Athletic; Dogs; Functional murmur; Myxomatous mitral valve disease; Physiologic murmur.