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Association of Cardiac Troponin I With Disease Severity
Study Questions:
Is high-sensitivity cardiac troponin I (cTnI) level a marker of prognosis in pulmonary hypertension (PH)?
Methods:
cTnI was measured in 255 PH patients (World Health Organization group 1-5) using a new highly sensitive (hs) assay. Other measures included demographics, creatinine, 6-minute walk distance, hemodynamics, cardiac magnetic resonance imaging, and B-type natriuretic peptide level. The association between cTnI and survival was assessed using Kaplan-Meier analysis and Cox regression.
Results:
cTnI was detectable with the hs assay in 95% of the patients with a median level of 6.9 pg/ml (interquartile range, 2.7-12.6 pg/ml). Higher cTnI levels were associated with higher levels of B-type natriuretic peptide, shorter 6-minute walk distance, and more severe hemodynamic and cardiac magnetic resonance imaging abnormalities. During a median follow-up of 3.5 years, 60 persons died. Unadjusted event rates increased across higher cTnI quartiles (3, 5, 13, 17 events/100 person-years, respectively, p trend = 0.002). cTnI in the fourth (vs. first) quartile remained associated with death in a final stepwise multivariable model that included clinical variables and hemodynamics (adjusted hazard ratio, 5.3; 95% confidence interval, 1.8-15.6).
Conclusions:
In conclusion, cTnI levels, detectable with a novel hs assay, identify patients with PH who have more severe hemodynamic and cardiac structural abnormalities and provide novel and independent prognostic information. This hs assay has the potential to detect more at-risk patients and improve current risk-stratification algorithms.
Perspective:
The novel hs cTnI assay has an approximate 10-fold lower detection limit compared with recent generation assays. cTnI was detected in two-thirds of the cohort who would have been undetected with standard assays. Nearly 70% of subjects had pre-capillary pulmonary arterial hypertension (PAH), in whom cTnI had prognostic ability even after adjusting for known markers of more advanced disease. Further studies are needed in the varying causes of PAH, as well as PH associated with left heart and valvular disease, lung diseases, and pulmonary embolism.
Keywords: Risk, Follow-Up Studies, Heart Defects, Congenital, Demography, Pulmonary Embolism, World Health Organization, Creatinine, Magnetic Resonance Imaging, Hemodynamics, Capillaries, Prognosis, Biomarkers, Troponin I, Hypertension, Pulmonary, Hydrogen-Ion Concentration, Natriuretic Peptide, Brain, Lung Diseases
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