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Stahl, Anna Helena (2010): Gewebedopplerechokardiographische Untersuchung der rechtsventrikulären Myokardfunktion gesunder und COB erkrankter Pferde: Assessment of right ventricular myocardial function by Doppler Myocardial Imaging in healthy and RAO affected horses. Dissertation, LMU München: Faculty of Veterinary Medicine
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Abstract

“Assessment of right ventricular myocardial function by Doppler Myocardial Imaging in healthy and RAO affected horses” In this study right ventricular longitudinal, circumferential and radial myocardial function were evaluated by different scan plans (short-axis view, long-axis view, right ventricular outflow tract) and by different Doppler myocardial imaging techniques (Tissue and pulsed wave Doppler, speckle tracking) for the first time. Furthermore the impact of one of the most common equine airways diseases, RAO, on right ventricular myocardial function was shown non-invasively. Right ventricular myocardial velocities, strain and strain rate, displacement as well as time intervals and electro-mechanical coupling periods were measured. In a prestudy in 6 healthy and 6 RAO horses colour tissue Doppler, pulsed wave Doppler and speckle tracking method were applied to evaluate radial, circumferential and longitudinal right ventricular myocardial function for the first time. Angle-independent speckle tracking was applied to zoomed right ventricle from long-axis four-chamber view. Healthy as well as RAO horses showed a velocity gradient of the right ventricular free wall from its base to its apex. In order to evaluate circumferential myocardial movement, tissue Doppler (ROI next to the pulmonary valve) and speckle tracking were applied to the right ventricular outflow tract myocardium. Colour tissue Doppler was applied simultaneously to the right, left and interventricular wall at the short axis view to evaluate whether radial movement of all ventricular walls is synchrone. To determine longitudinal myocardial function colour tissue Doppler and pulsed wave Doppler were applied to lowered basal right ventricular free wall of long-axis four-chamber view (tricuspid annulus). This scan plan and applied tissue Doppler techniques were of lowest intra-individual variability whereas other techniques and scan plans, especially speckle tracking method were of very high intra-individual variability (> 25 %). Furthermore, this scan plan and evaluated longitudinal myocardial function revealed the most significant differences between healthy and RAO affected horses. Therefore tricuspid annular motion was evaluated by colour tissue and pulsed wave Doppler in the whole study population (20 healthy, 6 mildly, 19 moderately and 16 severely affected RAO horses). This scan plan and applied techniques were able to detect altered right ventricular myocardial function due to different grades of RAO. Both tissue Doppler techniques revealed right ventricular diastolic dysfunction (lowered early diastolic filling velocity, elevated late diastolic filling velocity / atrial contraction) and colour tissue Doppler derived compensatory elevated strain. These tissue Doppler indices were able to discriminate between RAO horses with secondary right heart alterations and healthy subjects, regardless the correlation of tissue Doppler indices to age and breathing frequency. This study showed that Doppler myocardial imaging is a useful tool to evaluate equine right ventricular myocardial function objectively. The impact of RAO on diastolic right ventricular myocardial function and contractility could be proven. These examinations point out the necessity of early RAO treatment and provide a non-invasive insight in equine right heart function for the first time.