N-Terminal Pro-B-Type Natriuretic Peptide Levels Inversely Correlated With Heart Rate Variability in Patients With Unstable Angina Pectoris

We explored the relationships between heart rate variability (HRV) and levels of N-terminal Pro-B-type natriuretic peptide (NT-proBNP) in patients with unstable angina pectoris (UA).A total of 90 consecutive patients admitted < 48 hours for UA were included. Serum levels of NT-proBNP were measured from blood samples. The cohort was divided into tertiles according to NT-proBNP levels. HRV parameters including SDNN, RMSSD, LF, HF, TP, and VLF were assessed by 24-hour Holter ECG monitoring.The median (IQR) NT-proBNP level was 177.02 (64.76, 740.70) pg/mL. Patients with SDNN < 100 ms had higher levels of NT-proBNP than those with SDNN > 100 ms (P = 0.003). With increasing levels of NT-proBNP, both the 24hour monitoring HRV and night-monitoring HRV showed that SDNN and VLF gradually decreased (P < 0.01), and patients in the NT-proBNP lowest tertile group had higher LF values than the other two groups (P < 0.05); however, no difference was found in RMSSD, HF, and TP. During the daytime, the LF, VLF, and TP values were lower in the NTproBNP highest group compared with the lowest tertile group (P < 0.05). NT-proBNP levels correlated negatively with SDNN (r = -0.314, P = 0.003) and VLF (r = -0.397, P < 0.001) but not with other HRV parameters. Multiple regression analysis showed that serum levels of NT-proBNP remained predictive of SDNN (β = -0.060, P = 0.001) and VLF (β = -0.145, P < 0.001), even after adjustment for confounders.Our study showed that the elevated serum levels of NT-proBNP predict reduced HRV parameters, and the increased NT-proBNP levels combined with decreased HRV represent the degree of neurohormonal dysfunction and may be better prognostic predictors for risk stratification in UA patients.