# Translational Echocardiography: The Dog as a Clinical Research Model of Cardiac Dysfunction
## 6 Dilated Cardiomyopathy (DCM), a Human and Canine Common Disease
### Echocardiographic Measurements on DCM
#### 6.1.4 Tissue Doppler and Speckle Tracking  
Tissue Doppler imaging comprises several techniques such as tissue velocity imaging (TVI), strain, and strain rate imaging. Tissue velocity imaging allows for the assessment of the myocardial wall's early (a') and late (a') diastolic (e') and systolic (s') velocities using either pulsed wave or color Doppler myocardial echography [105]. TVI has demonstrated to be a promising technique for detecting early myocardial dysfunction in dogs with cardiomyopathyopathy [105,106]. One study involving canine patients with either occult or overt dilated cardiomyopathy (DCM) demonstrated that the mitral annular velocities measured by pulsed-wave tissue velocity imaging were reduced in both systolic and diastolic phases [107]. In addition, a singular study investigated the systolic and diastolic tissue velocity imaging as well as strain parameters in amines diagnosed with Idiopathic Dilated Cardiomyopathy across different breeds [108]. In echocardiography, the assessment of myocardial deformation involves measuring the displacement and velocity of cardiac tissue during both systole and diastole. Strain refers to a dimensionless index of deformation that quantifies the percentage change in the length of a myocardial segment in the radial, circumferential, or longitudinal direction relative to the baseline measurement [109]. In contrast to tissue velocity imaging (TVI), strain and strain rate imaging are minimally influenced by the motion of the heart and tethering effects in adjacent segments. This overcomes the limitations of TVI and provides more accurate results. In human patients, these measurements have demonstrated high sensitivity in detecting myocardial diseases [110]. Figure 15: Increased mitral septal separation in a canine patient with DCM. **7. Canine Patients with Naturally Occurring Cardiac Diseases--Learning from a Potential Echocardiography Research Model**  
Dogs have been an essential model for cardiology research since the beginning of experimental physiology in the nineteenth century, allowing the understanding of various mechanisms involved in the electrophysiological and mechanical functioning of the human heart [111]. Dogs' most common cardiovascular diseases, myxomatous mitral valve degeneration (MVDM) and primary dilated cardiomyopathy(CMD), have an incidence of approximately 10% in daily canine veterinary clinical practice. In addition, the relatively short life span of dogs (12-14 years, depending on the breed) and the rapid evolution of these diseases turn the canine patient into a relevant clinical model for the comparative study of these same pathologies in humans [55; 112]. Figure 16: (**a**). Decreased Sphericity Index in canine patient. (**b**). Normal Sphericity Index in the canine patient. In dogs, MVDM is the most common cardiovascular disease and has been associated with canine geriatric patients of certain dog breeds. In humans, its estimated prevalence is 2 to 3% of all cardiac diseases. The molecular and degenerative mechanisms involved in the evolution of the disease appear to be common in both species. For example, the migration of endothelial cells towards the interstitial tissue, stripping the valve's surface, characterizes the myxomatous degeneration of valve tissue in humans and canines [30]. For its part, CMD is the second most common cardiovascular disease in dogs. It develops from a preclinical or hidden phase, without obvious symptoms, up to a clinical-stage marked by congestive heart failure due to systolic dysfunction, severe arrhythmias, syncope, and even sudden death. In both canines and humans, it is associated with several genetic, inflammatory, and hemodynamic factors that cause a decrease in the contractile capacity of the myocardium and an increase in the internal diameter of the cardiac chambers [104; 112]. Although murine models, mice, and rats have been used to study acute myocardial infarction and arterial hypertension, they have not been used to study these chronic diseases.