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Is a Pattern of Increasing Biomarker Concentrations Important for Long-Term Risk Stratification in Acute Coronary Syndrome Patients Presenting Early after the Onset of Symptoms?

¹ Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada; ² Institute for Clinical Evaluative Sciences, University of Toronto, Toronto, Ontario, Canada; ³ Department of Pathology, Women and Infants Hospital, Providence, Rhode Island, USA; ⁴ Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; ⁵ Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, Manitoba, Canada; ⁶ Cardiovascular Division and Division of Laboratory Medicine, Mayo Clinic, Rochester, Minnesota, USA

^aaddress correspondence to this author at: Hamilton Regional Laboratory Medicine Program, Henderson General Hospital (Core Lab Section), 711 Concession Street, Hamilton, ON, Canada. Fax 905.575.2581; e-mail kavsakp{at}mcmaster.ca.

Abstract

Background: Guidelines for treatment of acute coronary syndrome (ACS) recommend observing a rise or fall in cardiac troponin (cTn) concentrations for assessing acute injury. It is unknown whether a rising pattern presages a more adverse long-term prognosis than elevations that do not change. The present study assessed whether a rising pattern of cardiac biomarkers was more prognostic than simple elevations.

Methods: We measured N-terminal pro-brain natriuretic peptide (NT-proBNP) (Roche), cTnT (Roche) and cTnI (Beckman Coulter) in 212 ACS patients. These biomarkers were measured in coincident EDTA and heparin plasma samples available from at least 2 different time points, an early first specimen obtained a median of 2 hours after onset of symptoms, interquartile range (IQR) 2–4 hours, and a later second specimen obtained at 9 hours, IQR 9–9 hours. The cTn concentration in the second specimen was used to classify myocardial necrosis (cTnI >0.04 ug/L; cTnT >0.01 ug/L). Outcomes [death, myocardial infarction (MI), heart failure (HF)] were obtained >8 years after the initial presentation. For patients with myocardial necrosis and a cTn concentration ratio (second/first measured concentrations) 1.00, the concentration ratios and the absolute concentrations in the second specimen were used to assess prognosis after 4 years.

Results: In myocardial necrosis, the relative change (cTn₂/cTn₁) was greater for cTnI than for cTnT (P <0.01), whereas the relative change in NT-proBNP was the same regardless of which troponin was used to classify necrosis (P = 0.71). The concentration ratio for cTnI, cTnT, and NT-proBNP was not useful for risk stratification (i.e., death/MI/HF; P 0.15).

Conclusions: A rise in cardiac troponin or NT-proBNP concentration in ACS patients presenting early after onset of pain is not helpful for long-term prognosis.