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

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.