Influence of concurrent lower respiratory tract disease on point-of-care lung ultrasound in small-breed dogs with myxomatous mitral valve disease

Background: Small-breed dogs commonly have concurrent myxomatous mitral valve disease (MMVD) and lower respiratory tract disease (LRTD).

Hypothesis: Small-breed dogs with preclinical MMVD and concurrent LRTD have more B-lines on point-of-care lung ultrasound (POC-LUS) compared to dogs without concurrent LRTD and are prone to misdiagnose as cardiogenic pulmonary edema (CPE).

Animals: A total of 114 small-breed dogs with preclinical MMVD.

Methods: A prospective study was conducted, in which POC-LUS was obtained and the number of B-lines was calculated by a single clinician using the Veterinary Bedside Lung Ultrasound Examination protocol. The presence/absence of LRTD was assessed by clinicians blinded to the POC-LUS results.

Results: Fifty and 64 dogs were in ACVIM stage B1 and B2, respectively. The presence of LRTD was prevalent in 74.6% (85/114) of small-breed dogs with preclinical MMVD. When a previously reported criterion for CPE diagnosis (≥2 sites with >3 B-lines/site) was applied, false-positive results were observed in 15.8% (18/114) of dogs with preclinical MMVD. The summated number of B-lines (3 vs. 1, P = .003), as well as the false-positive rate (20% vs 3%, P = .04), were significantly higher in dogs with LRTD compared with dogs without LRTD. Multivariable logistic regression showed the presence of abnormalities other than B-line on POC-LUS (eg, thickened pleura or consolidation) could predict false-positive results (odds ratio = 3.75, 95% confidence intervals 1.12-12.54; P = .03) after adjustment for other clinical and echocardiographic factors.

Conclusions and clinical importance: Concurrent LRTD and abnormalities other than B-lines should be considered in the interpretation of POC-LUS in MMVD dogs.