Influence of paroxysmal atrial fibrillation attack on brain natriuretic peptide secretion

Plasma brain natriuretic peptide (BNP) concentration is higher during atrial fibrillation (Af) than sinus rhythm, based on studies of electrical defibrillation treatment of patients with chronic Af. However, the change in paroxysmal atrial fibrillation (PAf) is not well known. This study investigated such changes and the relationship between BNP and Af.

BNP levels were successfully measured at three time points: before Af attack, during Af attack, and after (spontaneous or pharmacological) termination of 68 consecutive Af attacks in 35 outpatients with PAf (23 men, 12 women, mean age 70.4 +/- 9.6 years). BNP was measured by immunoradiometric assay.

BNP (median[quartiles]) during PAf was increased by 66[25, 120] pg/ml (2.4-fold) compared to during sinus rhythm (p < 0.0001), and fell to the former level after return to sinus rhythm (before attack = 39[18, 70], during attack = 102[52, 205], after attack = 35[20, 67]). BNP increased in 55 (81%) of 68 attacks, did not change (within +/- 20 pg/ml) in 11 (16%), and decreased in 2 (3%). BNP was already elevated immediately (within 4 hr) after onset of Af, and BNP elevation (delta BNP) showed no significant relationship with the time elapsed after onset. During the Af attack, 41% of PAf patients were asymptomatic although BNP increased significantly.

These results suggest that elevated amounts of BNP during Af are released from secretory granules in the atrium, and BNP elevation of unknown cause may be attributed to the presence of asymptomatic Af. Cardiac function evaluation using BNP during Af requires special consideration, unlike during sinus rhythm, even in patients with PAf or chronic Af, because BNP during Af is the sum of the BNP values from the ventricle (reflecting left ventricular function) and the atrium (due to Af).