Time course of B-type natriuretic peptides changes after ventricular fibrillation: relationships with cardiac syncope

Does N-Terminal Pro-B-Type Natriuretic Peptide Improve the Risk Stratification of Emergency Department Patients With Syncope?

BACKGROUND

Studies have reported that natriuretic peptides provide prognostic information for emergency department (ED) syncope.

OBJECTIVE

To evaluate whether adding N-terminal pro-B-type natriuretic peptide (NT-proBNP) to the Canadian Syncope Risk Score (CSRS) improves prediction of 30-day serious adverse events (SAEs).

DESIGN

Prospective cohort study.

SETTING

6 EDs in 2 Canadian provinces.

PARTICIPANTS

1452 adult ED patients with syncope.

INTERVENTION

Serum NT-proBNP was measured locally at 1 site and batch processed at a central laboratory from other sites. The concentrations were not available to treating physicians or for adjudication of outcomes.

MEASUREMENTS

An adjudicated composite outcome of 30-day SAEs, including death and cardiac (arrhythmic and nonarrhythmic) and noncardiac events.

RESULTS

Of 1452 patients enrolled, 152 (10.5% [95% CI, 9.0% to 12.1%]) had 30-day SAEs, 57 (3.9%) of which were identified after the index ED disposition. Serum NT-proBNP concentrations were significantly higher among patients with SAEs than those without them (median, 626.5 ng/L vs. 81 ng/L; P < 0.001). Adding NT-proBNP values to the CSRS did not significantly improve prognostication (c-statistic, 0.89 and 0.90; P = 0.12 for difference), regardless of SAE subgroup or whether the SAE was identified after the index ED visit. The net reclassification index shows that NT-proBNP would have correctly reclassified 3% of patients with SAEs at the expense of incorrectly reclassifying 2% of patients without SAEs.

LIMITATIONS

Our study was powered to detect a 3% difference in the area under the curve. The heterogeneity of outcomes and robust baseline discrimination by the CSRS will make improvements challenging.

CONCLUSION

Although serum NT-proBNP concentrations were generally much higher among ED patients with syncope who had a 30-day SAE, this blood test added little new information to the CSRS. Routine use of NT-proBNP for ED syncope prognostication is not recommended.

PRIMARY FUNDING SOURCE

Physicians' Services Incorporated Foundation, Canadian Institutes of Health Research, and The Ottawa Hospital Academic Medical Organization.

Prohormones in the Early Diagnosis of Cardiac Syncope

Background

The early detection of cardiac syncope is challenging. We aimed to evaluate the diagnostic value of 4 novel prohormones, quantifying different neurohumoral pathways, possibly involved in the pathophysiological features of cardiac syncope: midregional–pro‐A‐type natriuretic peptide (MRproANP), C‐terminal proendothelin 1, copeptin, and midregional‐proadrenomedullin.

Methods and Results

We prospectively enrolled unselected patients presenting with syncope to the emergency department (ED) in a diagnostic multicenter study. ED probability of cardiac syncope was quantified by the treating ED physician using a visual analogue scale. Prohormones were measured in a blinded manner. Two independent cardiologists adjudicated the final diagnosis on the basis of all clinical information, including 1‐year follow‐up. Among 689 patients, cardiac syncope was the adjudicated final diagnosis in 125 (18%). Plasma concentrations of MRproANP, C‐terminal proendothelin 1, copeptin, and midregional‐proadrenomedullin were all significantly higher in patients with cardiac syncope compared with patients with other causes (P<0.001). The diagnostic accuracies for cardiac syncope, as quantified by the area under the curve, were 0.80 (95% confidence interval [CI], 0.76–0.84), 0.69 (95% CI, 0.64–0.74), 0.58 (95% CI, 0.52–0.63), and 0.68 (95% CI, 0.63–0.73), respectively. In conjunction with the ED probability (0.86; 95% CI, 0.82–0.90), MRproANP, but not the other prohormone, improved the area under the curve to 0.90 (95% CI, 0.87–0.93), which was significantly higher than for the ED probability alone (P=0.003). An algorithm to rule out cardiac syncope combining an MRproANP level of <77 pmol/L and an ED probability of <20% had a sensitivity and a negative predictive value of 99%.

Conclusions

The use of MRproANP significantly improves the early detection of cardiac syncope among unselected patients presenting to the ED with syncope.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01548352.