Risk outcome assessment with novel long-T ITC complex and high sensitivity troponin I and T in patients with suspected acute coronary syndromes: MERITnI substudy

OBJECTIVES: Understanding whether the novel long-T ITC complex might assist in interpreting clinical prognostic utility compared to established cardiac biomarkers is needed. We determined long term major adverse cardiac events (MACE) and all-cause mortality (ACM) predicated on novel long-T ITC complex and high sensitivity cardiac troponin I (hs-cTnI) and T (hs-cTnT) assays in the emergency department (ED). METHODS: cTn assays were measured on the Mindray CL-1200i platform at presentation in consecutive patients enrolled in 'Mindray hs-cTnI Assay Analytical and Clinical Evaluation for the Diagnosis and RIsk Assessment of Myocardial InfarctIon' (MERITnI) (NCT05853042) trial with suspected ischemia. Sex specific 99th percentiles upper reference limits (URLs) were: hs-cTnI female 14 ng/L, male 15 ng/L; hs-cTnT female 10 ng/L, male 19 ng/L; long-T ITC complex 0.9 ng/L, same for female and male. RESULTS: Of 1,070 patients, 59.4 % were male, 43.4 % White, 45.5 % Black, and 39.5 % ≥65 years. Independent of biomarkers, a continuum of risk over 1 year showed MACE increased to 16.1 % and ACM to 16.5 %. Long-T ITC complex did not show a continuum change, increasing only 0.1 % (HR: 1.001 (1.0-1.001) per ng/L. However, hs-cTnI increased 1.8 % (HR: 1.018 [1.009-1.027] for each ng/L (p<0.0001) and hs-cTnT increased 0.3 % per ng/L (HR: 1.003 [1.001-1.006]) (p=0.0028). Between subjects ≤URLs and >URLs, MACE and ACM all biomarkers showed significant (p<0.0001) differences over 1 year. For MACE in those >URL long-T ITC complex increased 11.2-25.2 %, hs-cTnI 18.0-35.0 % and hs-cTnT 8.9-24.2 %. For ACM in those >URL long-T ITC complex increased 4.5-23.3 %, hs-cTnI 5.0-26.2 %, and hs-cTnT 3.6-24.1 %. CONCLUSIONS: Novel long-T ITC complex did not provide new prognostic value to either hs-cTnI or hs-cTnT. Patients with increased hs-cTnI and hs-cTnT concentrations had marked increases in MACE and ACM risk at 1-year.