Additive prognostic value of NT-proBNP over TIMI risk score in intermediate-risk patients with acute coronary syndrome

OBJECTIVES
We evaluated the prognostic value of N-terminal pro-brain natriuretic peptide (NT-proBNP) for further risk stratification of intermediate-risk patients with non-ST elevation acute coronary syndromes (NSTE-ACS).

STUDY DESIGN
The study included 137 intermediate-risk patients (85 men, 52 women; mean age 62±11 years) with ACS, based on the TIMI risk score (scores 3 to 5). Serum NT-proBNP levels were measured 12 hours after the last anginal episode. The patients were divided into four groups according to the following NT-proBNP quartiles: 17-310 pg/ml (n=34), 313-688 pg/ml (n=35), 724-2,407 pg/ml (n=34), and 2,575-24,737 pg/ml (n=34). Primary endpoint of the study was mortality. The mean follow-up was 21.8±7.1 months.

RESULTS
There were 27 deaths (19.7%), 14 of which were in the 4th quartile (4th vs 1st, 2nd, and 3rd quartiles: p=0.02, p=0.01, and p<0.01, respectively). The first three quartiles did not differ significantly in this respect. In Kaplan-Meier analysis, patients in the 4th quartile had the lowest cumulative survival (log rank test, 4th vs 1st, 2nd, and 3rd quartiles: p=0.041, p=0.026, and p=0.009, respectively). NT-proBNP level was significantly higher in nonsurvivors than in survivors (p=0.01). In univariate analysis, mortality was also associated with the TIMI risk score, ejection fraction, and age. Patients who died were older (65.6±11.9 years vs 60.7±11.0 years; p=0.048) and had a lower ejection fraction (46.3±11% vs 54.1±9.8%; p<0.001) than patients who survived. Mortality rates corresponding to TIMI risk scores of 3, 4, and 5 were 25.9%, 29.6%, and 44.4%, respectively (p=0.58 for TIMI 3 vs 4; p=0.001 for TIMI 3 vs 5; p=0.013 for TIMI 4 vs 5). Cox proportional hazards regression analysis showed that only TIMI risk score was an independent predictor of mortality (hazard ratio 2.3, 95% confidence interval 1.4-3.8, p=0.001).

CONCLUSION
NT-proBNP has an additive predictive value over TIMI risk score in predicting long-term mortality in intermediate-risk patients with ACS.