Evaluation of ventricular function by X-Strainâ„¢ in dogs with mitral regurgitation

The aim of echocardiography is to perform the study of the cardiac function, through the evaluation of alterations of anatomy, contractility and flow. The ultrasound techniques used until now to reveal possible alterations of myocardial contractility, such as b-mode, m-mode and Tissue Doppler Imaging (TDI) haven't allowed to obtain complete evaluations. In 2002, Buckberg, analyzing the cardiac structure, demonstrated a complex movement of the heart, determined by the particular helical disposition of the myocardial bundles. The motion is composed by three different components: radial, longitudinal and of torsion. The TDI is dependent from the angle Doppler of incidence, therefore it allows to estimates only movements parallel to the ultrasound beam. Recently, the application of Speckle Tracking , being independent from the angle Doppler, has permitted to improve the study of the cardiac motion. X-StrainTM is a new ultrasound tool by ESAOTE, based on Feature Tracking, that is able to perform the evaluation of the ventricular performance. The aims of this study are to verify the possible application of X-StrainTM in 18 dogs affected by mitral regurgitation, to verify the relationship between ventricular indexes (ejection fraction, shortening fraction, and left atrium diameter- aorta diameter ratio) obtained through traditional techniques (B-MODE, M-MODE), X-StrainTM and the severeness of heart failure in dogs with mitral regurgitation (ISACHC classification), and to verify if X-StrainTM indexes (radial strain and strain rate, endocardial and epicardial circumferential strain and strain rate, radial and rotational displacement of endocardium and epicardium) could have a prognostic value and allow an easier therapeutic control of the patient during the follow-up. The dogs have been evaluated twice (T0 and T1), and the data have been subjected to a statistical analysis. It has been demonstrated a significant positive correlation between the radial strain and strain rate and the ejection an shortening fractions. Besides, to the increase of the radial strain and strain rate, corresponds an improvement of the clinical conditions. The radial strain seems to be less sensible to the volume overload caused by the mitral regurgitation. The endocardial and the epicardial circumferential strain and strain rate have the same trend at T0 and T1. This condition suggests that the motion of torsion could be not influenced by the volume overload. Besides, it has been possible to consider the follow-up of four dogs treated with inotropic medicines, and it has been possible to note their improvement of ventricular contraction. The results therefore, suggest the possibility to use X-StrainTM as a valid ultrasound method in dog to complete the cardiac study, and in particular, to reveal alteration of regional and global myocardial contractility, and to evaluate the complex motion of torsion of heart. It would be interesting to perform a study in a bigger sample of dogs, to obtain physiological data and to verify the eventual different effect of the treatment. X-StrainTM could allow to check the follow-up of dogs, to choose the right therapy.