Mid- to long-term biovariability of hs-cTnT within 6-12 months in Muscular Dystrophic Cardiomyopathy: An Observational Study on 35 patients.

Mustafa Yildirim (Heidelberg)1, C. Reich (Heidelberg)1, C. Salbach (Heidelberg)1, R. Pribe-Wolferts (Heppenheim)2, B. R. Milles (Heidelberg)1, T. Täger (Heidelberg)1, M. Müller-Hennessen (Heidelberg)3, B. Meder (Heidelberg)1, N. Frey (Heidelberg)1, E. Giannitsis (Heidelberg)1

1Universitätsklinikum Heidelberg Klinik für Innere Med. III, Kardiologie, Angiologie u. Pneumologie Heidelberg, Deutschland; 2Kreiskrankenhaus Bergstraße gGmbH Innere Medizin II Heppenheim, Deutschland; 3Atos Praxisklinik Zentrum für Gefäßerkrankungen und Präventivmedizin Heidelberg, Deutschland


Introduction: This study aimed to evaluate the short- and long-term variability of hs-cTnT in patients with chronic skeletal muscle disease and cardiac involvement. We determined the reference change values (RCV) and minimal important differences (MID) of hs-cTnT within 6 to 12 months to characterize physiological biovariability and differentiate acute from chronic elevations.

 Hs-cTnT measurements were obtained at the index visit and after 6-12 months scheduled routine outpatient visit in 35 stable outpatients. All had confirmed skeletal muscular dystrophies. RCVs and MIDs were calculated to assess the biological variation of hs-cTnT. 

 The absolute MID and relative RCVs for the 6–12-month interval in patients were calculated as 1.2 ng/L (95% CI: 0.7 - 2.1) and 28.6% (95% CI: 27.9% - 29.6%), respectively. Five individuals (14.3%) showed an increase or decrease in hs-cTnT outside of RCV, representing an increase or decrease at follow-up. Regarding MID, 25 patients (73.5%) had an increase or decrease outside the MID range. Clinical specificity of hs-cTnT for discrimination of cardiac involvement was 100% (95%CI: 3-100) and strongly dependent on the diagnostic reference standard. Specificities were highest when cardiac involvement was based on contrast-enhanced cardiac magnetic resonance imaging in combination with myocardial biopsy. Sensitivity was significantly lower (26.5% vs 97.1%, p = 0.5485) when hs-cTnI was used at the established 99th percentile instead of hs-cTnT.

Conclusions: This study establishes reference change values and minimal important differences for hs-cTnT in patients with skeletal muscle disease and cardiac involvement, offering critical insights into the mid- to long-term biovariability. These findings contribute to the nuanced understanding of disease progression over time, aiding clinicians in distinguishing acute from chronic elevations and facilitating improved patient management.

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