**Acknowledgements**

*Advanced Concepts in Endocarditis - 2021*

movement (**Figure 14C** and **D**) [99].

in the univariate analysis [109].

shortening time strain were significantly slower [75].

with loading conditions [95]. Several studies demonstrated strain and strain rate obtained from the 2D-STE were useful to grade the progression of dogs with MMVD [95–98]. One study claimed the longitudinal strain with the GE analysis software algorithm (EchoPAC) was inconsistent and less repeatable, while radial strain curves from short-axis images were more consistent and more repeatable (**Figure 14A** and **B**) [95]. Since the software algorithm for strain is automated, special attention should be focused on "(1) timing of the ECG to select the cardiac cycle and the onset and duration of analysis; (2) tracing of the endocardial border for automated detection; (3) inspecting the region of interest; (4) following the tissue tracking in real-time and slow-motion; and (5) inspecting the generated curves relative to the R-waves and aortic valve closure (AVC)" as described in Smith et al. [95]. A velocity vector imaging (VVI) is another form of strain analysis, which can display tissue velocity as a vector showing the amplitude and direction of the

Atrial myocardial deformation profiles estimated by TDI and 2D-STE (e.g. strain and strain rate) have been recently emerged as a good alternative method of exploring LA mechanics in both humans and dogs [100–103]. Although many drawbacks of this approach were noticed (e.g. suboptimal reproducibility, angle dependence, and the confounding effect of noise artifacts), 2D-STE can be a more advanced angle-independent echocardiographic technique for the direct evaluation of LA function than standard grayscale echocardiographic images [100–103]. The specific STE variables subject to the LA function include peak atrial longitudinal average strain (PALS), peak atrial contraction average strain (PACS), and contraction strain index (CSI), which reflect the LA function during its reservoir, booster pump phase, and the contribution of LA active contraction to the LV filling phase (**Figure 14B**) [104]. In humans, LA strain analysis has been useful for grading patients with valvular diseases, atrial fibrillation, or acute coronary disease [105–107]. However, a recent canine study found the STE variables were not significantly different between ACVIM B1 and B2 groups, although those (especially, PALS) were significantly different between ACVIM B2 and C groups [108]. The use of cut-off for PALS <27.9% enables to perfectly differentiate dogs in ACVIM stage B2 from those in ACVIM stage C with a sensitivity of 100% and specificity of 100% [108]. Another study also demonstrated the STE variables including PALS, PACS, and CSI were significantly decreased with the progression of MMVD [103]. A further study from this study group also found the STE variables (PALS <30% and CSI per 1% increase) were predictors of cardiac death

Since the RV chamber is crescent-shaped and is wrapped around the LV, precise echocardiographic assessment of RV function is often difficult. The TDI and STE can overcome this limitation as reported in human studies [110, 111]. Recent canine study found the STE on RV was applicable and repeatable in healthy dogs [93]. Furthermore, other study demonstrated the RV longitudinal strain and the dyssynchrony index were significantly different from control dogs [75]. In this study, the global, free wall, and septal RV longitudinal strain in dogs with precapillary PH were significantly lower than those in control, while free wall and septal systolic

In this chapter, we described echocardiographic features of MMVD in dogs along with human echocardiographic criteria of MR. Although there are many similarities for diagnosing and grading the severity of MR in both species,

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**7. Conclusion**

The authors express great gratitude to Siemens Healthineers (Ms. UnWook Park) for technical support and Drs Jae-Min Suhl and Jin-Hee Noh for sharing space and resources for preparing echocardiographic images on this chapter.
