B-Type natriuretic peptide trends correlate with clinical events in heart failure patients discharged from an observation unit

Abstract

Study objectives: B-type natriuretic peptide (BNP) has been evaluated extensively as a diagnostic marker in dyspneic emergency department (ED) patients, but changes in BNP during treatment are less well understood. We hypothesize that changes in BNP levels will predict treatment failures in heart failure patients treated in an observation unit. Methods: We performed a retrospective medical record review of heart failure patients treated in the observation unit between February 2003 and March 2004. Those patients discharged directly from the observation unit were the focus of this analysis. All patients were required to have a minimum of 2 BNP values drawn as part of their observation unit management, with the last BNP performed just before observation unit disposition. Thirty-day heart failure event rates included an ED visit for heart failure, an observation unit readmission for heart failure, a hospital readmission for heart failure, and death. Event rates were not counted twice (ie, an ED visit for heart failure resulting in a hospital admission counted as only 1 event). The Mann-Whitney U test was used to compare continuous variables. Results: Thirty-two patients discharged directly from the observation unit fulfilled inclusion criteria. These patients had a mean age of 54.8 years, 59.4% were men, and 83.1% were black. Eight of the 32 patients discharged from the observation unit experienced 30-day events: 0 deaths, 7 ED heart failure visits, 1 observation unit heart failure readmission, and 6 hospital heart failure readmissions. Patients whose BNP levels increased despite apparent clinical improvement experienced more 30-day events (44.4%) than those patients whose BNP levels decreased with treatment (17.4%). Although there was no significant difference in initial BNP levels between the 2 groups (1,436±940 pg/mL versus 1,025±1,029 pg/mL; P =.124), the absolute value of the final BNP drawn was higher in those with events (1,620±854 pg/mL) than those without events (785±626 pg/mL; P =.033). Conclusion: This pilot study suggests that discharged observation unit patients with heart failure whose BNP decreases with treatment have a better prognosis than those patients whose BNP increases with treatment.