Epidemiological Study of Myxomatous Valvular Disease-A Retrospective Study of 195 Cases
*Veterinary faculty, University of Ljubljana, Clinic for Surgery and Small Animal Medicine
To study epidemiology of myxomatous valvular disease a retrospective study was done at the University Clinic for Small Animal Surgery and Medicine in Slovenia. One of the aims of the study was to find out if the classification of the patients and left atrium/aortic ratio predict the survival length.
One hundred and ninety-five dogs were diagnosed with myxomatous valvular disease, which represented 297 visits in 4 years. Dogs were evaluated by means of physical examination, electrocardiography, thoracic radiography, hematology, biochemistry and echocardiography according to the need in a specific case. Dogs were divided into three classes according to the International Small Animal Cardiac Health Council (ISACHC): 1. asymptomatic, 2. mild to moderate heart failure, 3. advanced heart failure. Each class was analyzed according to the breed distribution, sex, age, weight, months of survival (mean, STDEV, range), grade of the murmur, ECG, radiographic, echocardiographic findings and therapy. Correlation was done between the left atrium/aortic ratio and ISACHC class and between length of survival and ISACHC class. One-way ANOVA (Tukey test) was calculated to find out statistical significance of the left atrium/aortic ratio between the classes and length of survival between the classes.
In the entire group of 195 dogs, the most common breeds were Toy and Medium Poodle (64 dogs), followed by mixed breed (34), Cocker spaniel (20), Pekinese dog (9) and other breeds. Among larger breeds of dogs Doberman pinschers, German boxers, German shepherds and Dalmatians were represented (16 dogs together). There were 147 males and 48 females in the whole group. There were 52 dogs in the 1st class, mean age of 10±2 years. Mean weight in this class was 15±10 kg, the left atrium/aortic ratio (LA/Ao; measured in the right short axis view) was 1,92±0,38. In the second class with 127 dogs the mean age was 11±2 years, the mean weight was 11±8 kg, the LA/Ao was 2,31±0,55. In the third class with 16 dogs the mean age was 11±2 years, the mean weight was 16±10 kg, the LA/Ao was 2,7 ±0,6. The LA/Ao ratio was correlated to the class of patients and correlation was significant at the 0,01 level (r=0,355), the multiple comparisons showed this ratio was significantly larger in each class against each of the other two classes (P 0,05). Survival was significantly (P 0,05) longer in the 1st class in comparison to the 2nd and 3rd class (38,3±13,1 months, 1st class, 17±12,8 months, 2nd class, 17,5±15,3 months, 3rd class). The survival between the 2nd class and the 3rd class was not significantly longer. In the 1st class most common grades of left apical systolic murmurs were 3/6 and 4/6, in the 2nd class additionally a grade 5/6 was common, and in class 3 grades 4/6 and 5/6 were the most common.
In addition to the small breeds of dogs, some larger breeds of dogs can be affected with the myxomatous valvular disease. LA/Ao ratio was significantly larger in advanced stages of the disease. Survival was significantly longer in the asymptomatic patients in comparison to the mild, moderate or advanced heart failure patients. LA/Ao ratio could possibly be used as a predictor of the disease stage and survival length.