Short-term fluctuations of plasma NT-proBNP levels in patients with new-onset atrial fibrillation: a way to assess time of onset?

OBJECTIVE: The objective of this study was to characterise short-term kinetics of plasma amino-terminal pro-B natriuretic peptide (NT-proBNP) levels in patients with new-onset atrial fibrillation (AF) without heart failure. DESIGN: Prospective cohort study. SETTING: Emergency departments and inpatient services of three large community hospitals. PATIENTS: 31 consecutive patients with new-onset atrial fibrillation (<24 h before presentation) persisting at least 48 h, without evidence of heart failure. MAIN OUTCOME MEASURES: Plasma NT-proBNP levels were obtained at presentation and then 6, 12, 18, and 24 h after presentation. A final sample was obtained 48 h after onset of AF. RESULTS: Mean plasma NT-proBNP levels and 95% CIs (pg/ml) during the 48-h period following onset of AF were: 0-6 h: 636 (395 to 928), 6-12 h: 1364 (951 to 1778), 12-18 h: 1747 (1412 to 2083), 18-24 h: 1901 (1549 to 2253), 24-36 h: 1744 (1423 to 2066) and 36-48 h: 1101 (829 to 1373). Mean time to peak NT-proBNP levels was 16.7 (0.7) h; 29 patients reached their peak levels within 24 h. The mean peak NT-proBNP level was significantly higher than those obtained at 0-6 h and at 36-48 h after onset of AF (p<0.001 for both). There was no correlation between ventricular rate and plasma NT-proBNP levels during any time period after onset of AF. CONCLUSION: In patients with new-onset AF but no clinical or radiographic evidence of heart failure, plasma NT-proBNP levels rise progressively to a peak during the first 24 h and then rapidly fall. This pattern may serve as an aid to assess the time from AF onset.

Congestive heart failure and VVI pacing mode: dynamic behavior of the dispersion of ventricular repolarization.

Dynamic Behavior of the Dispersion of Ventricular Repolarization. The aim of this study was to evaluate the circadian variation in the spatial dispersion of ventricular repolarization in continuously paced patients with congestive heart failure (CHF). Fourteen patients (10 males, 4 females, aged 65 +/- 8 years) with CHF due to dilated cardiomyopathy (DCM) and an echocardiographic ejection fraction of 28% +/- 3% were studied. All patients underwent AV junctional RF ablation and permanent pacemaker implantation for drug refractory chronic atrial fibrillation (AF). Patients were evaluated at 1 month postimplant with a three-channel 24-hour Holter monitor, using the three plane Frank orthogonal leads (X, Y, and Z), in VVI pacing mode at 70 beats/min. For each hour, the mean value of spike-T interval dispersion of the first five beats was measured. The control group consisted of 20 patients without structural heart disease, but with AF and complete AV block, continuously paced in VVI mode at 70 beats/min. The dispersion of the spike-T interval had a circadian behavior in the study population, with higher values at night and lower during the daytime. During the daytime, the mean value of spike-T interval dispersion was 39 +/- 5 ms and during the nighttime it was 45 +/- 7 ms (P = 0.003). Such a difference between day and night was not found in the control group (38 +/- 6 ms and 40 +/- 8 ms, respectively, P = NS). In the daytime period the mean value of spike-T interval dispersion of our study population was comparable to that of the control group (P = NS), while during the nighttime it was significantly higher (P = 0.0004). In conclusion, by evaluating the dispersion of ventricular repolarization in two dimensions, space and time, a circadian variation was found in paced patients with CHF due to DCM. The increased QT dispersion in these patients during the nighttime period was attributed to different effects of vagal activity in normal and abnormal myocardial areas.