Myocardial triglycerides in cardiac amyloidosis assessed by proton cardiovascular magnetic resonance spectroscopy

Abstract

Background: Cardiac involvement of amyloidosis leads to left-ventricular (LV) wall thickening with progressive heart failure requiring rehospitalization. Cardiovascular magnetic resonance (CMR) is a valuable tool to non-invasively assess myocardial thickening as well as structural changes. Proton CMR spectroscopy (¹H-CMRS) additionally allows assessing metabolites including triglycerides (TG) and total creatine (CR). However, opposing results exist regarding utilization of these metabolites in LV hypertrophy or thickening. Therefore, the aim of this study was to measure metabolic alterations using ¹H-CMRS in a group of patients with thickened myocardium caused by cardiac amyloidosis.

Methods: ¹H-CMRS was performed on a 1.5 T system (Achieva, Philips Healthcare, Best, The Netherlands) using a 5-channel receive coil in 11 patients with cardiac amyloidosis (60.5 ± 11.4 years, 8 males) and 11 age- and gender-matched controls (63.2 ± 8.9 years, 8 males). After cardiac morphology and function assessment, proton spectra from the interventricular septum (IVS) were acquired using a double-triggered PRESS sequence. Post-processing was performed using a customized reconstruction pipeline based on ReconFrame (GyroTools LLC, Zurich, Switzerland). Spectra were fitted in jMRUI/AMARES and the ratios of triglyceride-to-water (TG/W) and total creatine-to-water (CR/W) were calculated.

Results: Besides an increased LV mass and a thickened IVS concomitant to the disease characteristics, patients with cardiac amyloidosis presented with decreased global longitudinal (GLS) and circumferential (GCS) strain. LV ejection fraction was preserved relative to controls (60.0 ± 13.2 vs. 66.1 ± 4.3%, p = 0.17). Myocardial TG/W ratios were significantly decreased compared to controls (0.53 ± 0.23 vs. 0.80 ± 0.26%, p = 0.015). CR/W ratios did not show a difference between both groups, but a higher standard deviation in patients with cardiac amyloidosis was observed. Pearson correlation revealed a negative association between elevated LV mass and TG/W (R = - 0.59, p = 0.004) as well as GCS (R = - 0.48, p = 0.025).

Conclusions: A decrease in myocardial TG/W can be detected in patients with cardiac amyloidosis alongside impaired cardiac function with an association to the degree of myocardial thickening. Accordingly, ¹H-CMRS may provide an additional diagnostic tool to gauge progression of cardiac amyloidosis along with standard imaging sequences.

Trial registration: EK 2013-0132.

Keywords: Cardiac amyloidosis; Cardiovascular magnetic resonance; Left-ventricular thickening; Myocardial metabolism; Proton spectroscopy.

Fig. 1

Position of the ¹H-CMRS voxel within the IVS of a patient with cardiac amyloidosis (a) and of a normal control (b). IVS, interventricular septum; ¹H-CMRS, Proton CMR spectroscopy

Fig. 2

Flow chart of CMR imaging and spectroscopy as well as processing pipeline for spectroscopy data. CR, Creatine; Gd-CA, gadolinium based contrast agent; LGE, late gadolinium enhancement; CMRS, cardiovascular magnetic resonance spectroscopy; bSSFP, balanced steady state free precession; PRESS, point-resolved spectroscopy; TG, triglycerides

Fig. 3

Mean and SD of TG/W and CR/W ratios in patients with amyloidosis compared to an age- and BMI-matched normal control group. TG/W, triglyceride-to-water; Cr/W, creatine-to-water; SD, standard deviation

Fig. 4

Exemplary spectra in a patient with amyloidosis and in a control. TG/W, triglyceride-to-water; CR/W, creatine-to-water; ppm, part per million

Fig. 5

Pearson’s correlation between TG/W ratios and (a) IVS and (b) LVMi, (c) GLS as well as (d) GCS. GCS, global circumferential strain; GLS, global longitudinal strain; IVS, interventricular septum; LVMi, left-ventricular mass indexed to body surface area; TG/W, triglyceride-to-water