Reliability, repeatability, and reproducibility of pulmonary transit time assessment by contrast enhanced echocardiography

Abstract

BackgroundThe aim of this study is to investigate the inter and intra-rater reliability, repeatability, and reproducibility of pulmonary transit time (PTT) measurement in patients using contrast enhanced ultrasound (CEUS), as an indirect measure of preload and left ventricular function.MethodsMean transit times (MTT) were measured by drawing a region of interest (ROI) in right and left cardiac ventricle in the CEUS loops. Acoustic intensity dilution curves were obtained from the ROIs. MTTs were calculated by applying model-based fitting on the dilution curves. PTT was calculated as the difference of the MTTs. Eight raters with different levels of experience measured the PTT (time moment 1) and repeated the measurement within a week (time moment 2). Reliability and agreement were assessed using intra-class correlations (ICC) and Bland-Altman analysis. Repeatability was tested by estimating the variance of means (ANOVA) of three injections in each patient at different doses. Reproducibility was tested by the ICC of the two time moments.ResultsFifteen patients with heart failure were included. The mean PTT was 11.8 ± 3.1 s at time moment 1 and 11.7 ± 2.9 s at time moment 2. The inter-rater reliability for PTT was excellent (ICC = 0.94). The intra-rater reliability per rater was between 0.81–0.99. Bland-Altman analysis revealed a bias of 0.10 s within the rater groups. Reproducibility for PTT showed an ICC = 0.94 between the two time moments. ANOVA showed no significant difference between the means of the three different doses F = 0.048 (P = 0.95). The mean and standard deviation for PTT estimates at three different doses was 11.6 ± 3.3 s.ConclusionsPTT estimation using CEUS shows a high inter- and intra-rater reliability, repeatability at three different doses, and reproducibility by ROI drawing. This makes the minimally invasive PTT measurement using contrast echocardiography ready for clinical evaluation in patients with heart failure and for preload estimation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12947-015-0044-1) contains supplementary material, which is available to authorized users.

Noninvasive pulmonary transit time: A new parameter for general cardiac performance

“…To improve the implementation, calculation of PTT can be fully automated as previously shown by Saporito et al . Given the feasibility and accuracy of this measuring technique, CEUS‐derived transit times might be a promising, additional parameter of general cardiac function. An additional advantage is that this measurement is less dependent on image quality than other techniques for reflecting overall cardiopulmonary function.…”

“…From this perspective, PTT measured by contrast‐enhanced ultrasound is a promising alternative as it is reproducible and less dependent on image quality. PTT represents the time for a bolus of contrast to pass from the right ventricle to the left ventricle, measured according to the indicator dilution principles.…”

“…This was shown earlier already by Sherman et al., assessing intracardiac hemodynamics using CEUS validated against right heart catheterization and survival. Importantly, both Brittain and Herold et al . showed that CEUS‐derived PTTs are reproducible and can be obtained with low intra‐ and inter‐individual variability.…”

“…However, the ultrasound measures are not always accurate, as calculation is based on geometrical assumptions of a 3D structure 2 or suboptimal image quality. 3 From this perspective, PTT measured by contrast-enhanced ultrasound is a promising alternative as it is reproducible 4 and less dependent on image quality. PTT represents the time for a bolus of contrast to pass from the right ventricle to the left ventricle, measured according to the indicator dilution principles.…”

“…This was shown earlier already by Sherman et al, 18 assessing intracardiac hemodynamics using CEUS validated against right heart catheterization and survival. Importantly, both Brittain 19 and Herold et al 4 showed that CEUS-derived PTTs are reproducible and can be obtained with low intra-and inter-individual variability. The study by Brittain et al also showed, albeit in a small study population, that PTT correlated with several ultrasound parameters of left ventricular systolic and diastolic function, right ventricular function, and pulmonary vascular status.…”