Cardiac biomarkers (BNP and troponin) useful for diagnosis and prognosis of cardiac syncope (BASEL IX)

Reference

du Fay de Lavallaz J, Badertscher P, Nestelberger T, et al. B-type natriuretic peptides and cardiac troponins for diagnosis and risk-stratification of syncope. Circulation 2019;139(21): 2403-2418.

Synopsis

B-type natriuretic peptides (BNP) are primarily used in the diagnosis of heart failure, and high-sensitivity cardiac troponins T and I (hs-cTnT and hs-cTnI) are primarily used in the diagnosis of acute coronary syndrome. These authors identified 1538 adults, 40 years and older, who presented to the emergency department within 12 hours of the onset of syncope. Patients with a nonsyncopal diagnosis, such as epilepsy or alcohol intoxication, were excluded. All patients underwent a standardized diagnostic evaluation, including measurement of the following biomarkers: BNP, N-terminal proBNP (NT-proBNP), hs-cTnT, and hs-cTnI. The final diagnosis was determined by 2 physicians masked to the BNP values. The mean age of the enrolled patients was 71 years, 40% were women, and 15% had cardiac syncope. All 4 biomarkers had good overall discrimination (ability to distinguish cardiac syncope from noncardiac syncope) with areas under the receiver operating characteristic curve (AUROCC) of 0.77 to 0.78. The optimal cutoffs (selected to achieve at least 95% specificity, which is helpful for ruling in when positive) were BNP greater than 302 pg/mL, NT-proBNP greater than 1966 pg/mL, hs-cTnT greater than 42 ng/L, and hs-cTnI greater than 31.1 ng/L. To rule out cardiac syncope, a sensitivity of 95% was targeted, and cardiac syncope was unlikely when BNP was less than 14.9 pg/mL, NT-proBNP was less than 69 pg/mL, hs-cTnT was less than 5 ng/L, and hs-cTnI was less than 2.2 ng/L. The biomarkers added to the diagnostic accuracy of the previously developed Evaluation of Guidelines in Syncope Study clinical prediction rule. Applying these cutoffs allows one to rule out or rule in cardiac syncope in approximately 30% of patients with syncope. The AUROCC for prognosis was also good, from 0.74 to 0.78 for death at 30 days and 0.74 to 0.76 for major adverse cardiac events at 30 days.