Can Atrial Fibrillation Cause Elevated BNP?
Yes, both atrial fibrillation with rapid ventricular response (AFib RVR) and chronic rate-controlled atrial fibrillation independently elevate BNP levels, even in patients with preserved left ventricular systolic function. This elevation occurs regardless of heart failure status and must be considered when interpreting BNP values in any patient with AFib.
Mechanism of BNP Elevation in Atrial Fibrillation
AFib independently raises BNP by approximately 20–30% compared to sinus rhythm, reflecting increased atrial wall stress, altered hemodynamics, and neurohormonal activation that occur with the arrhythmia itself 1, 2.
Plasma BNP and NT-proBNP levels are significantly elevated in both paroxysmal and persistent AFib and decrease rapidly after restoration of sinus rhythm, confirming that the arrhythmia itself—not just underlying structural heart disease—drives the elevation 1.
In patients with persistent AFib and preserved left ventricular ejection fraction, baseline BNP levels average 148.4 ± 111.4 pg/mL compared to 74.9 ± 81.7 pg/mL in matched controls without AFib (p = 0.01), and NT-proBNP levels average 290.9 ± 257.2 pg/mL versus 47.8 ± 80.6 pg/mL in controls (p = 0.0001) 3.
Impact of Rate Control on BNP
Strict rate control (achieving resting heart rate <80 bpm) significantly reduces BNP levels in patients with chronic AFib, even when systolic function is preserved 4.
In a study of 38 patients with chronic AFib, achieving strict rate control reduced average heart rate from 101 ± 16.3 bpm to 77 ± 5.2 bpm and resulted in significant decreases in BNP, left ventricular volumes, and atrial dimensions 4.
Conversely, patients who did not achieve strict rate control showed significantly higher BNP values at follow-up despite similar baseline cardiac dimensions 4.
Reduced diurnal variation of heart rate in AFib patients is significantly associated with increased BNP levels (r = -0.411, P < 0.001), which correlates with left ventricular diastolic dysfunction 5.
Clinical Implications for BNP Interpretation
When interpreting BNP in patients with AFib, apply higher diagnostic thresholds than in sinus rhythm—standard heart failure cut-offs (BNP <100 pg/mL or NT-proBNP <300 pg/mL) are unreliable in the presence of AFib 2.
A BNP level that would be considered "normal" in sinus rhythm may still reflect significant cardiac dysfunction in a patient with AFib, because the arrhythmia itself elevates the baseline 1.
Confirmatory echocardiography is essential when BNP is elevated in AFib patients, as the biomarker cannot differentiate between AFib-related elevation, heart failure with reduced ejection fraction, heart failure with preserved ejection fraction, or valvular disease 2.
Prognostic Significance
Elevated BNP in AFib patients independently predicts mortality, heart failure hospitalization, and stroke, even after accounting for the arrhythmia itself 1, 2.
Higher baseline BNP levels in lone AFib patients are strong predictors of recurrent arrhythmia after ablation (hazard ratio for +1-log-BNP change, 2.32; 95% CI, 2.11–2.74; P<0.001), reflecting increased cardiac chamber wall stress and intrinsic atrial disease 6.
Patients with paroxysmal or persistent AFib who have elevated BNP (>96 pg/mL) and echocardiographic signs of left ventricular diastolic dysfunction are significantly more likely to progress to permanent AFib within one year (OR 1.06 per pg/mL increase, CI 1.01–1.12, p < 0.0162) 7.
Common Pitfalls
Do not apply standard heart failure rule-out thresholds (BNP <100 pg/mL or NT-proBNP <300 pg/mL) in patients with AFib—these cut-offs are inappropriate because AFib independently raises natriuretic peptides by 20–30% 2.
Do not assume that an elevated BNP in a rate-controlled AFib patient necessarily indicates heart failure—the arrhythmia itself causes elevation, and echocardiography is required to assess ventricular function and filling pressures 1.
Do not overlook the importance of achieving strict rate control—inadequate rate control perpetuates BNP elevation and adverse cardiac remodeling even when systolic function appears preserved 4.
Serial BNP monitoring requires changes ≥50% to be clinically significant due to high biological variability (30–50%), particularly in the setting of AFib where baseline values are already elevated 2.