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.
Highlights
The 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
We demonstrated that volume estimation by CEUS, resulting from the multiplication of the flow by the PTT (i.e. the difference between the Mean transit times (MTT) of the left atrium and the right ventricle (RV)), showed excellent agreement with the actual volumes, both in-vitro and in-vivo [2, 6]
We investigated the effect of different ultrasound contrast-agent (UCA) doses on the PTT measurement
Summary
The 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. We demonstrated that volume estimation by CEUS, resulting from the multiplication of the flow by the PTT (i.e. the difference between the MTTs of the left atrium and the right ventricle (RV)), showed excellent agreement with the actual volumes, both in-vitro and in-vivo [2, 6]. It showed even better accuracy than transpulmonary thermodilution volume estimation [1, 8]. Our second objective was to evaluate the reliability and agreement between PTT measurements obtained by physicians and non-physicians
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