Abstract 19848: Novel Quantification of Extracellular Expansion by Cardiac Magnetic Resonance is a Robust Marker in Diagnosis of Amyloid Cardiac Infiltration
Background: Diagnosis of cardiac amyloidosis (CA) has significant therapeutic and prognostic implications. While late gadolinium enhancement (LGE) imaging by MRI demonstrates a characteristic pattern of infiltration, a more precise method that quantifies myocardial amyloid infiltration can further improve the diagnosis and monitoring of CA. Thus, we tested the hypothesis that a direct measure of myocardial extracellular volume fraction (MECVF) using dynamic T1-weighted imaging can diagnose CA.
Methods: We performed 3T cardiac MRI in 27 consecutive patients (mean age 70 ± 15 yrs) with suspected infiltrative cardiomyopathy. MRI included cine imaging and LGE 10 min after 0.15 mmol/Kg of gadolinium (Gd). An adiabatic inversion recovery Look-Locker gradient echo technique was acquired once before and 3 times over 30 min after Gd injection to measure the dynamic myocardial T1 changes. Myocardial partition coefficient was calculated as the ratio of T1 change of the myocardium to blood. MECVF was obtained by normalizing the partition coefficient to patient's hematocrit. LV subendocardial and subepicardial LGE was blindly graded as present or absent using a 17-segment model.
Results: In this cohort, 15 patients were confirmed to have CA (11 by biopsy and 4 by clinical evaluation combined with LGE), 2 patients had systemic amyloidosis without CA and 10 had a nonspecific cardiomyopathy on further workup. Mean MECVF was substantially higher in patients with CA than the other 2 groups (p < 0.001, p = 0.002, Figure) and demonstrated a strong correlation with the extent of LGE (r = 0.76, p < 0.0001) and with LV mass index (r = 0.61, p = 0.01).
Conclusions: Direct quantification of extracellular matrix expansion by MECVF may characterize the burden of CA infiltration. Elevated MECVF is associated with higher extent of LGE and increased LV mass index. This novel quantitative method may aid in the diagnosis of CA and in monitoring its response to therapy. It thus warrants further evaluation.
- © 2010 by American Heart Association, Inc.