title: Quantifying Myocardial Contractility Changes Using Ultrasound-Based Shear Wave Elastography.
abstract: Myocardial contractility, a significant determinant of cardiac function, is valuable for diagnosis and evaluation of treatment in cardiovascular disorders including heart failure. Shear wave elasticity imaging (SWEI) is a newly developed ultrasound-based elastographic technique that can directly assess the stiffness of cardiac tissue. The aim of this study was to verify the ability of this technique to quantify contractility changes in the myocardium.
  
  
  
  In 12 isolated rabbit hearts, SWEI measurements were made of systolic stiffness at five different coronary perfusion pressures from 0 to 92 mm Hg. The changes in coronary perfusion were used to induce acute stepwise reversible changes in cardiac contractility via the Gregg effect. The Gregg effect is the dependency of contractility on coronary perfusion. In four of the hearts, the measurements were repeated after delivery of gadolinium, which is known to block the Gregg effect.
  
  
  
  Systolic stiffness measured by SWEI changed linearly with coronary perfusion pressure, with a slope of 0.27 kPa/mm Hg (mean of 95% CI, R2= 0.73). As expected, the change in contractility due to the Gregg effect was blocked by gadolinium, with a significant reduction of the slope to 0.08 kPa/mm Hg.
  
  
  
  SWEI measurements of systolic stiffness provide an index of contractility in the unloaded isolated rabbit heart. Although this study was done under ideal imaging conditions and with nonphysiologic loading conditions, it reinforces the concept that this ultrasound technique has the potential to provide a direct and noninvasive index of cardiac contractility.
authors.affiliation: Biomedical Engineering Department, Duke University, Durham, North Carolina.
authors.forename: Maryam
authors.initials: M
authors.lastname: Vejdani-Jahromi
authors.affiliation: Biomedical Engineering Department, Duke University, Durham, North Carolina.
authors.forename: Jenna
authors.initials: J
authors.lastname: Freedman
authors.affiliation: Biomedical Engineering Department, Duke University, Durham, North Carolina.
authors.forename: Matthew
authors.initials: M
authors.lastname: Nagle
authors.affiliation: Biomedical Engineering Department, Duke University, Durham, North Carolina.
authors.forename: Young-Joong
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Biomedical Engineering Department, Duke University, Durham, North Carolina.
authors.forename: Gregg E
authors.initials: GE
authors.lastname: Trahey
authors.affiliation: Biomedical Engineering Department, Duke University, Durham, North Carolina. Electronic address: patrick.wolf@duke.edu.
authors.forename: Patrick D
authors.initials: PD
authors.lastname: Wolf
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D003326:Coronary Circulation / Q000502:physiology; D004452:Echocardiography / Q000379:methods*; D054459:Elasticity Imaging Techniques / Q000379:methods*; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D009200:Myocardial Contraction / Q000502:physiology*; D011817:Rabbits; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013318:Stroke Volume / Q000502:physiology*; D016277:Ventricular Function, Left / Q000502:physiology*
keywords: Contractility; Elastography; Gregg effect; Shear wave elasticity imaging (SWEI); Tissue characterization; Ultrasound imaging