Myxomatous mitral valve degeneration (MMVD) is the most common canine cardiac disease.
In the studies presented in this dissertation, we used advanced echocardiographic techniques to elucidate several aspects of MMVD in dogs. Our hypothesis was that the mitral valve (MV) morphology could have a role in the development of MMVD. First, we tested whether we could use real time three-dimensional transthoracic echocardiography (RT-3DTTE), and an offline software for MV analysis to evaluate canine MV. We described that the technique was feasible and repeatable, we evaluated the morphology of the MV in healthy dogs, and we provided reference values for MV morphologic variables in this species. Then, we used the same technique to compare healthy dogs to dogs affected by MMVD. We found that dogs affected by MMVD have more circular and flatter valve. We then analyzed the MV of healthy Cavalier King Charles Spaniels (CKCSs), given the high predisposition of this breed for MMVD. Our findings indicate that compared to healthy dogs of other breeds, the MV of healthy CKCSs is flatter and has less leaflet tenting, corroborating our hypothesis that an altered MV morphology could represent a predisposing factor for disease development. We also used RT–3DTTE to characterize the area of the regurgitant MV orifice of dogs affected with MMVD, finding that the technique requires further standardization in order to become clinically useful.
The elevation of pulmonary venous pressure caused by MMVD can, in some dogs, cause pulmonary arterial hypertension (PH), which is a risk factor associated with worse outcome in dogs with MMVD. Diagnosis of PH in dogs with MMVD is usually made by estimating pulmonary pressure using Doppler echocardiography. We are currently evaluating the accuracy of this technique, compared to invasive measurement of pulmonary pressure. Only preliminary data are presented regarding this study, as the disclosure of the blinding would have infringed the power of the study. Our preliminary results demonstrate that there is only moderate agreement between the two techniques, indicating that caution should be used when deriving the non-invasive estimation of systolic pulmonary pressure in order to make clinical decisions. / Ph. D. / The studies collected in this dissertation focus on myxomatous mitral valve disease (MMVD), which is the most common heart disease in dogs, and the most common cause of cardiac-related death in this species. This disease mainly affects one of the heart valves, i.e. the mitral valve (MV), impeding its normal functionality. In the studies presented in this dissertation, we used advanced non-invasive ultrasonographic techniques to investigate the mechanisms involved in this disease. We hypothesized that a different shape of the MV in some dogs could contribute to the development of the disease. We used 3D ultrasounds to build models of the MV and analyze the shape of it. We first demonstrated that using this technique in dogs was feasible and repeatable, and that the MV of normal dogs was elliptical and saddle-shaped. We then compared the shape of the MV of normal dogs, to the shape of the MV of dogs affected with MMVD. We found that dogs with the disease have a MV that is flatter and more circular. In our next study, we examined the shape of the MV of a breed of dogs that is predisposed to develop MMVD: Cavalier King Charles Spaniels (CKCSs). Our study found that healthy CKCSs have an overall flatter MV when compared with the other breeds, and that the normal MV of CKCSs is similar to the MV of affected dogs of other breeds. This finding support our hypothesis that an abnormal shape of the MV could contribute to the development of the disease. In another study, we saw to evaluate whether we could use 3D ultrasounds for investigating the shape of the hole that creates on affected MV. We concluded that this technique still requires more standardization before being used for evaluation of dogs. In another study, of which some preliminary results are presented in this dissertation, we are testing how accurate it is to evaluate the pressure of the pulmonary artery using ultrasonography. We are doing this by comparing this technique to a direct measurement of the pressures with a catheter in the pulmonary artery. We found that measurements obtained with the two techniques do not agree very well, which most likely indicates the evaluation of the pulmonary artery pressure using ultrasonography requires caution.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/77704 |
| Date | 23 May 2017 |
| Creators | Menciotti, Giulio |
| Contributors | Veterinary Medicine, Borgarelli, Michele, Huckle, William R., Abbott, Jonathan A., Guglielmini, Carlo, Haggstrom, Jens Ulrik, De Vita, Raffaella |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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