Magnetocardiography for the Non-Invasive Diagnosis of Myocardial Inflammation in Cardiac Amyloidosis: A Proof-of-Concept Study

AIMS: Myocardial inflammation is increasingly recognized for its association with impaired clinical outcomes in cardiac amyloidosis but a trend towards less invasive diagnosis impedes its detection. The aim of this study was to assess magnetocardiography (MCG) as a potential non-invasive method to diagnose myocardial inflammation in patients with cardiac amyloidosis. METHODS AND RESULTS: This retrospective proof-of-concept study included 27 patients with cardiac amyloidosis who had undergone MCG and endomyocardial biopsy as part of their diagnostic workup. Immunohistopathological evaluation identified myocardial inflammation in 10 patients (37.0%). Patients with myocardial inflammation had significantly higher magnetocardiography vector (VMCG) values than those without (0.093 [IQR 0.058-0.183] vs. 0.052 [IQR 0.039-0.073]; P = 0.01). With an area under the curve of 0.785 (95% CI 0.600-0.970; P < 0.01), VMCG had significant diagnostic value for myocardial inflammation in cardiac amyloidosis when tested against a non-informative random classifier in receiver operating characteristic analysis. Youden's index identified VMCG ≥0.078 as the optimal cut-off to discriminate between patients with and without myocardial inflammation, yielding a sensitivity of 60.0%, a specificity of 88.2%, a positive predictive value of 75.0% and a negative predictive value of 78.9%. CONCLUSIONS: This proof-of-concept study provides initial evidence for the potential of MCG as a non-invasive method to identify myocardial inflammation in patients with cardiac amyloidosis. These findings require validation in larger prospective studies but could substantially contribute to the optimization of personalized management in patients diagnosed with cardiac amyloidosis via non-invasive pathways in the future.