Cardiac Elastography With External Vibration for Quantification of Diastolic Myocardial Stiffness

Heart failure is an increasing global health problem. Approximately 50% of patients with heart failure have heart failure with preserved ejection fraction (HFpEF) and concomitant diastolic dysfunction (DD), in part caused by increased myocardial stiffness not detectable by standard echocardiography. While elastography can map tissue stiffness, cardiac applications are currently limited, especially in patients with a higher body mass index. Therefore, we developed cardiac time-harmonic elastography (THE) to detect abnormal diastolic myocardial stiffness associated with DD.

Cardiac THE was developed using standard medical ultrasound and continuous external vibration for regionally resolved mapping of diastolic shear wave speed as a proxy for myocardial stiffness. The method was prospectively applied to 54 healthy controls (26 women), 10 patients with moderate left ventricular hypertrophy (mLVH; 5 women), and 45 patients with wild-type transthyretin amyloidosis (wTTR; 4 women), 20 of whom were treated with tafamidis. Ten healthy participants were reinvestigated after 2 to 6 months to analyze test-retest reproducibility by intraclass correlation coefficients.

Myocardial shear wave speed was measured with good reproducibility (intraclass correlation coefficient = 0.82) and showed higher values in wTTR (3.0 ± 0.7 m/sec) than in mLVH (2.1 ± 0.6 m/sec) and healthy controls (1.8 ± 0.3 m/sec, all P < .05). Area under the curve values were 0.991 and 0.737 for discriminating wTTR and mLVH from healthy controls, respectively. Shear wave speed was reduced in patients after tafamidis treatment (2.6 ± 0.6 m/sec, P = .04), suggesting the potential value of THE for therapy monitoring. Shear wave speed was quantified in the septum, posterior wall, and an automatically masked region (here stated for the septal region).

Cardiac THE detects abnormal myocardial stiffness in patients with DD with high penetration depth, independent of body mass index and region selection. Based on standard ultrasound components, cardiac THE is cost-effective and has the potential to become a point-of-care method for stiffness-sensitive echocardiography.