# Translational Echocardiography: The Dog as a Clinical Research Model of Cardiac Dysfunction
## 5 (MDMV) Comparative Pathology and Pathophysiology
### Mitral Valve Disease Epidemiology  
Mitral regurgitation is a common valvular heart disease affecting millions of people worldwide. It is the third most common form of valvular heart disease, and its prevalence is estimated to be between 3-5% in the general population. Mitral valve prolapse is the most common mitral valve pathology, accounting for 2% to 3% of the total population [45]. The chronic degenerative nature of this pathology and the increased life expectancy probably contribute to these presentation rates [46]. Degenerative myxomatous mitral valve disease is dogs' most prevalent form of heart disease. In the same way, being a degenerative phenomenon, it is more present in geriatric patients [30; 47]. Degenerative myxomatous mitral valve disease is commonly observed in other small dog breeds with less than 15 kg of body weight, such as Miniature Poodles, Miniature Schnauzers, and Chihuahuas [48; 49; 50; 51; 52]. In fact, this pathology accounts for a substantial proportion of all heart disease cases in dogs, amounting to around 75% of cardiac clinical cases [51]. Mitral valve prolapse is a condition commonly observed in Cavalier King Charles Spaniels, characterized by the failure of the left atrioventricular valve to close properly due to the accumulation of abnormal myxomatous material and nodular changes on the valve leaflets. This condition is prevalent in a significant percentage of Cavalier King Charles Spaniels, ranging from 11.4-44.95%, and is often accompanied by age and sex-dependent heart murmurs. This degenerative valve disease is similar to myxomatous valvular degeneration, also known as valvular endocarditis. Although tricuspid valve involvement is less frequent, it can still occur. What makes Mitral valve prolapse in Cavalier King Charles Spaniels unique is that it tends to occur at a younger age, with almost 19% of dogs under one year of age exhibiting heart murmurs, and likely more than 50% of dogs over five years of age displaying murmurs [50; 51]. Degenerative mitral valve disease is a prevalent cardiac condition affecting dogs and humans, characterized by progressive degeneration of the mitral valve leading to mitral regurgitation. The clinical presentation varies in both species and can range from mild asymptomatic regurgitation to severe mitral insufficiency with congestive heart failure [52]. In dogs, valvular degeneration, mitral regurgitation, eccentric cardiac hypertrophy, systolic dysfunction, left heart failure, and congestive heart failure are the clinical consequences of severe Degenerative mitral valve disease. In addition. Cardiac mortality within six years of diagnosis of mitral valve disease is 11% in dogs [53; 54]. Although surgical repair is associated with better outcomes, it is not widely available due to its high cost and the limited number of veterinary medical units that perform the procedure. Therefore, medical treatment with loop diuretics, Angiotensin-converting enzyme inhibitors, aldosterone receptor inhibitors, and inodilators or positive inotropes is the standard of care for dogs with severe mitral regurgitation and secondary congestive pulmonary edema [30; 54; 55]. The clinical course of Degenerative mitral valve disease in dogs begins with mild asymptomatic mitral regurgitation, progresses to varying degrees of mitral insufficiency with eccentric left ventricular hypertrophy and atrial enlargement, and commonly escalates later to severe mitral insufficiency with clinical signs of congestive pulmonary edema, typically occurring during the relatively short adult lifespan of the dog compared to humans [30]. Canine Myxomatous Mitral Valve Disease. Comparative Transthoracic Echocardiography with Human Mitral Valve Prolapse  
Many diagnostic methods exist for evaluating mitral valve disease in human and small animal medicine. Transthoracic echocardiography is a basic and primary test for establishing both species' diagnosis and prognostic profile of mitral valve disease.