title: Pulmonary transit time measurement by contrast-enhanced ultrasound in left ventricular dyssynchrony.
abstract: BACKGROUND
  Pulmonary transit time (PTT) is an indirect measure of preload and left ventricular function, which can be estimated using the indicator dilution theory by contrast-enhanced ultrasound (CEUS). In this study, we first assessed the accuracy of PTT-CEUS by comparing it with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Secondly, we tested the hypothesis that PTT-CEUS correlates with the severity of heart failure, assessed by MRI and N-terminal pro-B-type natriuretic peptide (NT-proBNP).
  
  
  RESULTS
  Twenty patients referred to our hospital for cardiac resynchronization therapy (CRT) were enrolled. DCE-MRI, CEUS, and NT-proBNP measurements were performed within an hour. Mean transit time (MTT) was obtained by estimating the time evolution of indicator concentration within regions of interest drawn in the right and left ventricles in video loops of DCE-MRI and CEUS. PTT was estimated as the difference of the left and right ventricular MTT. Normalized PTT (nPTT) was obtained by multiplication of PTT with the heart rate. Mean PTT-CEUS was 10.5±2.4s and PTT-DCE-MRI was 10.4±2.0s (P=0.88). The correlations of PTT and nPTT by CEUS and DCE-MRI were strong; r=0.75 (P=0.0001) and r=0.76 (P=0.0001), respectively. Bland-Altman analysis revealed a bias of 0.1s for PTT. nPTT-CEUS correlated moderately with left ventricle volumes. The correlations for PTT-CEUS and nPTT-CEUS were moderate to strong with NT-proBNP; r=0.54 (P=0.022) and r=0.68 (P=0.002), respectively.
  
  
  CONCLUSIONS
  (n)PTT-CEUS showed strong agreement with that by DCE-MRI. Given the good correlation with NT-proBNP level, (n)PTT-CEUS may provide a novel, clinically feasible measure to quantify the severity of heart failure.
  
  
  BACKGROUND
  NCT01735838.
authors.affiliation: Department of Anesthesiology and Intensive-Care, Catharina Hospital Eindhoven, Eindhoven, the Netherlands Ingeborg.Herold@cze.nl.
authors.forename: Ingeborg H F
authors.initials: IH
authors.lastname: Herold
authors.affiliation: Department of Electrical Engineering, Signal Processing Systems, Eindhoven University of Technology, Eindhoven, the Netherlands.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Saporito
authors.affiliation: Department of Electrical Engineering, Signal Processing Systems, Eindhoven University of Technology, Eindhoven, the Netherlands.
authors.forename: Massimo
authors.initials: M
authors.lastname: Mischi
authors.affiliation: Department of Electrical Engineering, Signal Processing Systems, Eindhoven University of Technology, Eindhoven, the Netherlands.
authors.forename: Hans C
authors.initials: HC
authors.lastname: van Assen
authors.affiliation: Department of Anesthesiology and Intensive-Care, Catharina Hospital Eindhoven, Eindhoven, the Netherlands.
authors.forename: R Arthur
authors.initials: RA
authors.lastname: Bouwman
authors.affiliation: Department of Cardiology, Catharina Hospital Eindhoven, Eindhoven, the Netherlands.
authors.forename: Anouk G W
authors.initials: AG
authors.lastname: de Lepper
authors.affiliation: Department of Radiology, Catharina Hospital Eindhoven, Eindhoven, the Netherlands.
authors.forename: Harrie C M
authors.initials: HC
authors.lastname: van den Bosch
authors.affiliation: Department of Anesthesiology and Intensive-Care, Catharina Hospital Eindhoven, Eindhoven, the Netherlands Department of Electrical Engineering, Signal Processing Systems, Eindhoven University of Technology, Eindhoven, the Netherlands.
authors.forename: Hendrikus H M
authors.initials: HH
authors.lastname: Korsten
authors.affiliation: Department of Cardiology, Catharina Hospital Eindhoven, Eindhoven, the Netherlands.
authors.forename: Patrick
authors.initials: P
authors.lastname: Houthuizen
keywords: B-type natriuretic peptide; cardiac magnetic resonance imaging; contrast echocardiography; heart failure; pulmonary transit time