Tissue Doppler Imaging is based on the same principles as Color Flow Doppler
Imaging. Modified filter settings enable the acquisition and quantitative analysis of
tissue movement. Color Tissue Doppler Imaging enables offline processing of the
raw data and therefore calculation of strain and strain-rate.
The aim of this study was to establish reference values for tissue velocity, strain
and Strain-Rate of the longitudinal and radial myocardial function of the cat. The
study was performed using a GEVingmed Vivid 7, Horten, Norway and its Echo-
Pac analysis software. For validation of the method, inter- and intraobserver variability
and inter- and intrareader variability were evaluated.
112 healthy cats between 1 and 17 years were included into the study. The study
population was comprised of 67 domestic shorthair cats and 45 pure breed cats
(25 main coons, 7 persians, 13 others). All cats were normotensive with a blood
pressure between 100 and 150 mmHg. The heart rates of the study cats varied
between 135/min and 260/min during the data acquisition of the septum, between
144/min and 255/min for the free wall, between 123/min and 257/min for the right
wall and between 140/min and 266/min for the short axis. Validation of the method
resulted in variation coefficients between 10 % and 70 % for the curve amplitudes.
The repeatability of the time to peak measurements was very good with variation
coefficients < 10 %.
There was a statistically significant correlation between some isolated TDImeasurement
and age, bread and sex. The only clinically relevant correlation was
the dependency between time to peak S values and the heart rate. Heart rate altered
these values by 60 %. Therefore, separate reference ranges for several
heart rate ranges were calculated by regression analysis.
The distribution of the tissue velocity is inhomogenous in the myocardium. A velocity
gradient from basal to apical myocardium was found. This inhomogenity is less
pronounced in the strain and Strain-Rate curves.
High heart rates (> 190/min) lead to a fusion of E- and A- wave producing an additive
effect which causes an EA-wave that is significantly higher than the E-wave.
The cut-off heart rate values ranged between 180/min and 190/min.