Effect of atrial pressure increase on effective refractory period and vulnerability to atrial fibrillation in patients with lone atrial fibrillation

Background: There is evidence suggesting that atrial fibrillation (AF) may be induced by acute increase of atrial pressure. The aim of the present stu dy was to investigate the effect of alterations in atrial pressure, induced by varying the atrioventricular (AV) interval, on atrial refractoriness, a nd on the frequency of induction of (AF), in patients with a history of lon e atrial fibrillation (LAF). Methods and Results: Twenty-five patients were included in this study. The patients were divided in two groups: the LAF group, and the control group. None of the patients in either group had organic heart disease. Effective r efractory period (ERP) and duration of atrial extrastimulus electrogram (A( 2)) were measured at two right atrial sites (high lateral wall, atrial appe ndage) during AV pacing (cycle length: 500 msec) with different AV interval s. Peak, minimal and mean atrial pressure increased from 8.57 +/- 2.37 to 1 8.14 +/- 4.74 mm Hg, 2 +/- 2.23 to 5.14 +/- 2.60 mm Hg (p = 0.0001) and fro m 4.28 +/- 1.6 mm Hg to 9.77 +/- 2.9 mm Hg (p = 0.001), respectively during AV interval modification. During lateral and atrial appendage pacing, with a progressive decrease of AV interval to 160, 100, 80, 40, 0 msec, the ERP , the dispersion of ERP, functional refractory period (FRP), A2 and latency period (LP) did not change significantly, in both groups. The frequency of induction of AF was not statistically different in both lateral atrial wal l and appendage, during pacing in different AV intervals. Conclusions: This study demonstrates that alterations in the intraatrial pr essure does not have important effects on atrial refractoriness and does no t increase vulnerability to AF in patients with a history of LAF.