Non-Invasively Measured Myocardial Torsional Modulus: Comparison to Invasive Evaluation of Diastolic Function.

Background: Left ventricular (LV) diastolic function is a key determinant of cardiac output; 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 imaging (CMR) 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).

Conclusions: 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.