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” 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.