Fourier space analysis of mechanical wave dispersion for transthoracic in vivo measurements of left-ventricular viscoelasticity

Diastolic dysfunction causes close to half of congestive heart failure and is associated with increased stiffness in left-ventricular myocardium. A clinical tool capable of measuring viscoelasticity of the myocardium would be beneficial in clinical settings. Here, we present a technique based on the previously reported Lamb wave Dispersion Ultrasound Vibrometry (LDUV) for in vivo noninvasive measurements of myocardial elasticity and viscosity. In vivo open-chest measurements of myocardial elasticity and viscosity obtained using a Fourier space based analysis of Lamb wave dispersion are reported. The approach was used to perform ECG-gated transthoracic in vivo measurements of group velocity, elasticity and viscosity throughout a single heart cycle. Group velocity, elasticity and viscosity in the frequency range 50-500 Hz increased from diastole to systole, consistent with contraction and relaxation of the myocardium.