Effect of sample volume size and sampling method on feline longitudinal myocardial velocity profiles from color tissue Doppler imaging.

The aims of this study were to compare the effect of sample volume (SV) size settings and sampling method on measurement variability and peak systolic (s'), and early (e') and late (a') diastolic longitudinal myocardial velocities using color tissue Doppler imaging (cTDI) in cats.Twenty cats with normal echocardiograms and 20 cats with hypertrophic cardiomyopathy.We quantified and compared empirical variance and average absolute values of s', e' and a' for three cardiac cycles using eight different SV settings (length 1,2,3 and 5 mm; width 1 and 2 mm) and three methods of sampling (end-diastolic sampling with manual tracking of the SV, end-systolic sampling without tracking, and random-frame sampling without tracking).No significant difference in empirical variance could be demonstrated between most of the tested SVs. However, the two settings with a length of 1 mm resulted in a significantly higher variance compared with all settings where the SV length exceeded 2 mm (p < 0.001). There was an overall significant effect of sampling method on the variability of measurements (p = 0.003) and manual tracking obtained the lowest variance. No difference in average values of s', e' or a' could be found between any of the SV settings or sampling methods.Within the tested range of SV settings, an SV length of 1 mm resulted in higher measurement variability compared with an SV length of 3 and 5 mm, and should therefore be avoided. Manual tracking of the sample volume is recommended.