Magnetocardiography detects non-ischemic cardiomyopathy despite normal hs-TnT and NT-proBNP

Background

Early diagnosis of cardiomyopathies (CM) remains challenging, particularly in the initial stages when structural and functional abnormalities may be subtle. Established cardiac biomarkers, including high-sensitivity troponin T (hs-TnT) and NT-proBNP, provide important diagnostic and prognostic information but may not fully capture early myocardial alterations in all patients1,2. In addition, ECG and echocardiography can be non-specific during early evaluation2. Magnetocardiography (MCG) is an emerging non-invasive technique that detects electrophysiological myocardial alterations and may offer complementary information in the assessment of suspected CM3-6.

Purpose

To evaluate the diagnostic performance of MCG in patients with suspected CM following exclusion of coronary artery disease (CAD), and to assess its complementary diagnostic value alongside established biomarkers, including high-sensitivity troponin T (hs-TnT) and NT-proBNP.

Methods

This retrospective analysis included 100 symptomatic patients after exclusion of CAD, defining a cohort with suspected CM. MCG was applied using a predefined cutoff value of 0.051. Analyses including hs-TnT (Ref: <15 ng/L) and NT-proBNP (Ref: <300 ng/L) were performed in patients with available biomarker measurements at presentation7,3. Final diagnosis was established using gold standard multimodal diagnostics, including CMR imaging, PET-CT, and endomyocardial biopsy (EMB) when indicated2.

Results

Fifty patients were diagnosed with CM using current gold standard diagnostics. MCG demonstrated high diagnostic performance overall to detect CM (sensitivity 96.2%, specificity 91.7%, PPV 92.6%, NPV 95.7%).

Importantly, pathological MCG findings identified additional CM cases confirmed by imaging or EMB in patients with normal hs-TnT and NT-proBNP levels (11%, n=8; Fig. 1 & 2).

In the hs-TnT subgroup analysis (n=85), 18.2% (n=16) of patients with confirmed CM demonstrated pathological MCG despite hs-TnT values within the reference range. Among patients with normal hs-TnT, MCG demonstrated sensitivity and NPV of 100% (95% CI 0.79–1.00 and 0.89–1.00) and specificity of 86.5% (95% CI 0.71–0.95). In patients with elevated hs-TnT, sensitivity was 92.6% (95% CI 0.75–0.99) and specificity 100% (95% CI 0.47–1.00).

Similarly, in the NT-proBNP analysis (n=88), MCG identified additional CM in patients with normal NT-proBNP (20.1%, n=18). In this subgroup, MCG demonstrated sensitivity of 94.7% (95% CI 74.0–99.9), NPV of 97.2% (95% CI 85.5–99.9), and specificity of 92.1% (95% CI 78.6–98.3). In patients with NT-proBNP ≥300 ng/L, sensitivity was 96.4% (95% CI 81.7–99.9) and specificity 66.7% (95% CI 9.4–99.2).

Conclusion

MCG provides complementary diagnostic information alongside established cardiac biomarkers, including hs-TnT and NT-proBNP. Its added value appears in patients with normal biomarker levels, where MCG may facilitate earlier detection of CM not captured by biomarkers alone.Figure 1Figure 2