L. Kristin Newby

Provocative biomarker stress test: stress-delta N-terminal pro-B type natriuretic peptide

Objective Stress testing is commonly performed in emergency department (ED) patients with suspected acute coronary syndrome (ACS). We hypothesised that changes in N-terminal pro-B type natriuretic peptide (NT-proBNP) concentrations from baseline to post-stress testing (stress-delta values) differentiate patients with ischaemic stress tests from controls. Methods We prospectively enrolled 320 adult patients with suspected ACS in an ED-based observation unit who were undergoing exercise stress echocardiography. We measured plasma NT-proBNP concentrations at baseline and at 2 and 4  hours post-stress and compared stress-delta NT-proBNP between patients with abnormal stress tests versus controls using non-parametric statistics (Wilcoxon test) due to skew. We calculated the diagnostic test characteristics of stress-delta NT-proBNP for myocardial ischaemia on imaging. Results Among 320 participants, the median age was 51 (IQR 44–59) years, 147 (45.9%) were men, and 122 (38.1%) were African–American. Twenty-six (8.1%) had myocardial ischaemia. Static and stress-deltas NT-proBNP differed at all time points between groups. The median stress-deltas at 2  hours were 10.4 (IQR 6.0–51.7) ng/L vs 1.7 (IQR −0.4 to 8.7) ng/L, and at 4  hours were 14.8 (IQR 5.0–22.3) ng/L vs 1.0 (−2.0 to 10.3) ng/L for patients with ischaemia versus those without. Areas under the receiver operating curves were 0.716 and 0.719 for 2-hour and 4-hour stress-deltas, respectively. After adjusting for baseline NT-proBNP levels, the 4-hour stress-delta NT-proBNP remained significantly different between the groups (p=0.009). Conclusion Among patients with ischaemic stress tests, static and 4-hour stress-delta NT-proBNP values were significantly higher. Further study is needed to determine if stress-delta NT-proBNP is a useful adjunct to stress testing.

PROGNOSTIC IMPLICATIONS OF LOW-LEVEL CARDIAC TROPONIN ELEVATION USING THE HIGH-SENSITIVITY ASSAY FOR CARDIAC TROPONIN T: RESULTS FROM EARLY ACS & SEPIA-TIMI 42

A high-sensitivity assay for cardiac troponin T (hsTnT) that reliably detects very low concentrations is widely used in many countries worldwide and is under regulatory consideration in the US. It is uncertain whether low levels detected with hsTnT are prognostically meaningful compared with the