Abstract 2310: Loss of Neurohumoral Adaptation in Atrial Fibrillation Predicts AF Recurrence
Background: Studies in healthy controls show ANP but not BNP rises during exercise, reflecting normal homeostatic mechanisms. Exercise response in atrial fibrillation (AF) patients provides insights into the maladaptive changes that occur in the atrial substrate. We hypothesize that a rise in pro NT-Atrial natriuretic peptide (ANP) during exercise reflects atrial integrity and can predict maintenance of sinus rhythm (SR) after cardioversion in AF patients.
Methods: Thirty patients (19 men, age 66yrs ±8.35) with persistent AF and normal left ventricular function undergoing cardioversion had baseline blood pressure, heart rate, and ECG recordings along with serial NT-pro ANP (ANP), NT-proBNP(BNP) measurements at rest, at peak exercise, in recovery phase and further samples 4 hours post cardioversion, at 1 and 3 months follow up.
Results: All 30 patients were successfully cardioverted. Mean resting HR was 85.26 bpm ± 18.09 and BP 127/75mmHg ± 14/7. At 1 month 17/30 patients were in SR and at 3 months 15/30 remained in SR (group 1) whilst 15/30 had AF recurrence (group 2). 11/15 (73.3%) patients in group 1 and 10/15 (66.7%) in group 2 were on anti-arrhythmic drugs. (p=0.69) Baseline mean ANP levels in groups 1 & 2 were 6.41±2.46 vs 6.67±2.30 and BNP 1030±515 vs 1077±516. Left atrial size was similar between groups 1 &2, (5.2cm±0.72cm vs. 5.3cm±0, p>0.05). However, at peak exercise 13/15 patients in group 1 had a >25% increase in ANP, 1 had no change and 1 had a fall in ANP. In group 2, only 4/15 had an ANP rise during exercise which was <15%, whilst 11/15 showed a decrease in ANP, p<0.0001 using independent sample t-test. Moreover, there was a significant fall in ANP from peak exercise to recovery in group 1 compared to group 2 (p=0.025). BNP also rose with peak exercise in Groups 1 & 2(38.7±107.9 vs. 27.7±83.5) but this was not significant, (p=0.75) and rather may reflect the irregular, fast ventricular response.
Conclusion: A rise (>25%) in ANP during exercise in AF patients reflects atrial substrate integrity and may predict SR maintenance post cardioversion. Loss of this adaptive feedback response may serve as a marker for extensive and irreversible myocyte damage reflecting an inability to maintain SR in the long term. BNP changes during exercise do not help to predict AF recurrence.