Myocardial Stiffness by Intrinsic Cardiac Elastography in Patients with Amyloidosis: Comparison with Chamber Stiffness and Global Longitudinal Strain

Abstract

The aim of this study was to test the hypothesis that intrinsic cardiac elastography can detect diastolic tissue abnormalities produced by cardiac amyloid infiltration and that measurements may have incremental value beyond traditional echocardiographic measures. The specific aims were (1) to evaluate the relationship between left ventricular myocardial stiffness (by elastography) and measures of diastolic chamber stiffness and systolic strain in patients with amyloidosis and (2) to compare their prognostic potential. We prospectively studied 67 patients with amyloidosis (cardiac amyloidosis, n=48; noncardiac amyloidosis, n=19) and 40 normal subjects. Patients underwent comprehensive echocardiography including measurement of left ventricular global longitudinal strain (GLS) by speckle-tracking. Intrinsic velocity propagation of myocardial stretch (iVP), a direct measure of myocardial elasticity, was quantified using intrinsic cardiac elastography. Chamber stiffness was evaluated from the end-diastolic pressure-volume relationships (P=αVβ). The major end point at follow-up was the composite of death, cardiac hospitalization, worsening heart failure, and stroke. The iVP of myocardial stretch was highest in patients with cardiac amyloidosis compared with those with noncardiac amyloidosis and normal subjects (3.2±1.0, 1.8±0.4, and 1.6±0.2m/sec, respectively; P<.0001) and correlated with chamber stiffness, function, and structure (β coefficient, operating chamber stiffness, GLS, wall thickness; P≤.001 for all). At follow-up (median, 2.6years), measures of left ventricular and myocardial stiffness, GLS, diastolic dysfunction grade, and N-terminal pro-brain natriuretic peptide were associated with excess events. At multivariate analysis, iVP of myocardial stretch remained an independent predictor of adverse events, incremental to GLS and N-terminal pro-brain natriuretic peptide. Measurements by cardiac elastography correlate with functional and structural derangements produced by cardiac amyloid infiltration but provide unique information that is incremental to conventional echocardiography.