Prevalence of mitral valve regurgitation in 97 apparently healthy Chihuahua dogs.

Abstract

Introduction/objectives: Mitral regurgitation (MR) is often caused by myxomatous mitral valve disease which affects many small-breed dogs, including Chihuahua dogs. The aim of the study was to assess the prevalence of MR and tricuspid regurgitation (TR), valvular thickening, and prolapse in a group of apparently healthy Chihuahua dogs.

Animals, materials and methods: Ninety-seven privately owned Chihuahua dogs, recruited via the Swedish Chihuahua Club, were included in the study. A prospective observational study was conducted where clinical examinations, electrocardiograms, and echocardiographic and Doppler examinations were performed in all dogs.

Results: Mitral regurgitation was found in 37 (38%) dogs and was considered mild in 31 dogs, moderate in four dogs, and severe in two dogs. A systolic murmur over the mitral valve area was heard in 21 (22%) dogs. Mitral valve thickening was observed in 36 (37%) and mitral valve prolapse in 12 (12%) dogs. Tricuspid valve regurgitation was present in 14 (14%) of all dogs and in 30% of dogs with MR. Dogs with MR were significantly older (median: 7.6 years) than dogs without MR (median: 3 years); P < 0.0001.

Study limitations: Whether or not the presence of MR reflects early stages of myxomatous mitral valve disease cannot be ascertained without the use of histological examination of the mitral valves.

Conclusions: Mitral regurgitation was common in this group of apparently healthy Chihuahua dogs, and at the age of 6.4 years, there is a 50% chance that a dog has developed MR. In the age group 9-10 years, MR was found in 80% of the dogs.