Non-invasively measured myocardial torsional modulus: Comparison to invasive evaluation of diastolic function

Abstract

Background: Left ventricular (LV) diastolic function is a key determinant of cardiac output and impairments of diastolic function can lead to heart failure. Assessment of diastolic function is challenging due to several factors, including the load dependence of ventricular filling. We developed a method using cardiovascular magnetic resonance (CMR) imaging to model the untwisting motion of the LV as a viscoelastic damped oscillator to derive myocardial torsional modulus (µ) and frictional damping characteristics, and hypothesized that the torsional modulus would correlate with invasive measures of LV stiffness. Methods: Twenty-two participants who underwent invasive left heart catheterization (LHC) and CMR for the evaluation of chest pain were evaluated. µ and damping constants were determined by solving a system of equations using CMR-measured LV geometrical and angular displacement data during diastole. Time constant of pressure decay τ and chamber stiffness β were measured from invasive LHC and CMR-derived volume data as comparison metrics of diastolic function. Results: µ was correlated with chamber stiffness constant β and time constant of pressure decay τ, derived from invasive measurement (R = 0.78, p < 0.001, and R = 0.51, p = 0.014, respectively). µ was also correlated with pre-A-wave diastolic pressure (0.67, p = 0.001). Conclusion: We propose a new method to objectively evaluate diastolic relaxation properties of the LV. This method may have promise to replace invasive, catheter-based assessment of diastolic function.

Keywords

• Torsional modulus
• Non-invasive evaluation
• CMR
• Diastolic function
• LV twist