Monophasic Action Potentials of the Right Atrium in Patients With Paroxysmal Atrial Fibrillation

Abstract

To investigate the mechanism of atrial fibrillation (AF), monophasic action potentials (MAPs) from the atrial myocardium were studied in 7 patients with paroxysmal AF (PAF) and in 7 control individuals. The MAPs were recorded using a contact catheter during sinus rhythm and continuous pacing at the high right atrium (HRA) with pacing cycle lengths of 600, 500 and 400 ms. MAPs were obtained from 6 sites in each participant. The MAPD₉₀ was measured from onset to 90% of MAP repolarization. Average, maximal and minimal MAPD₉₀ (avMAPD₉₀, maxMAPD₉₀ and minMAPD ₉₀) were obtained from all participants. The dispersion of MAPD₉₀ (dispMAPD₉₀) was defined as the difference between maxMAPD₉₀ and minMAPD₉₀. The width of each atrial potential (WAP) and the wavelength index (WLI = MAPD₉₀ / WAP) were determined. Average, maximal and minimal WLI (avWLI, maxWLI and minWLI) were obtained from all participants. The avMAPD₉₀ and maxMAPD₉₀ did not significantly differ between the 2 groups. The minMAPD₉₀ in the PAF group was significantly smaller than that in the control group at HRA pacing with cycle lengths of 500 and 400 ms (210±18 ms vs 245±14 ms, p<0.05; 207±23 ms vs 238±20 ms, p<0.05; respectively). The dispMAPD₉₀ was significantly longer in the PAF group than in the control group during sinus and HRA pacing. The WAP value did not differ between the 2 groups. The minWLI in the PAF group was significantly smaller than that in the control group at HRA pacing with cycle lengths of 500 and 400 ms (3.3±0.5 vs 3.8±0.3, p<0.05; 3.2±0.4 vs 3.7±0.3, p<0.02). A shortened and widened dispersion of atrial refractoriness may play an important role in the genesis of AF. Furthermore, smaller wavelengths may form in the atrium of patients with PAF. (Jpn Circ J 2001; 65: 893 - 896)