Cardiac Elastography with External Vibration for Quantification of Diastolic Myocardial Stiffness

Objectives: Heart failure is an increasing global health problem. Approximately 50% of patients with heart failure have 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 (BMI). Therefore, we developed cardiac time-harmonic elastography (THE) to detect abnormal diastolic myocardial stiffness associated with DD.

Material and methods: Cardiac THE was developed using standard medical ultrasound and continuous external vibration for regionally resolved mapping of diastolic shear wave speed (SWS) as a proxy for myocardial stiffness. The method was prospectively applied to 54 healthy controls (HC) (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. 10 healthy participants were re-investigated after 2-6 months to analyze test-retest reproducibility by intraclass correlation coefficients (ICC).

Results: Myocardial SWS was measured with good reproducibility (ICC=0.82) and showed higher values in wTTR (3.0±0.7 m/s) than in mLVH (2.1±0.6 m/s) and HCs (1.8±0.3 m/s, all p<0.05). Area-under-the-curve values were 0.991 and 0.737 for discriminating wTTR and mLVH from HCs, respectively. SWS was reduced in patients after tafamidis treatment (2.6±0.6 m/s, p=0.04), suggesting the potential value of THE for therapy monitoring. SWS was quantified in the septum, posterior wall and an automatically masked region (here stated for the septal region).

Conclusions: Cardiac THE detects abnormal myocardial stiffness in patients with DD with high penetration depth, independent of BMI 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.