OBJECTIVEElectrical restitution was believed to be a determinant responsible for the stability of heart rhythm. Although numerous studies focused on the role of action potential duration restitution (APDR) in the initiation and maintenance of ventricular fibrillation (VF), the relationship between atrial APDR and atrial fibrillation (AF) has not been fully understood. This study aims to investigate the characteristics of APDR of left atrium (LA) and right atrium (Rs) in canines and the relevance to induction of AF.

METHODSMonophasic action potential (MAP) was recorded from LA and RA in 14 canines using the MAP recording-pacing combination catheter. APDR, plotted as action potential duration (APD) on the preceding diastolic interval (DI), was assessed by use of programmed stimulation with a single extrastimulus (S1S2) at LA and RA. Episodes of AF were recorded and analyzed.

RESULTSAPD90 was significantly shorter in the LA than that in the RA [(157.4 +/- 43.5) ms vs. (170.9 +/- 37.9) ms, P < 0.05]. The mean slope of the APDR curve by S1S2 in the LA was significantly greater than that in the RA (1.3 +/- 0.4 vs. 0.9 +/- 0.3, P < 0.05). The incidence of induced AF was significantly higher in the LA than in the RA (11/18 vs. 7/18, P < 0.05).

CONCLUSIONSThe APDR and MAP characteristics are not uniform between atrium, which may be one of the important mechanisms responsible for the initiation of AF. Heterogeneity of APDR between LA and RA might create critical gradients or a dispersion of repolarization and substrate for re-entrant arrhythmias and vulnerability to AF.

Action Potentials ; Animals ; Atrial Fibrillation ; etiology ; physiopathology ; Atrial Function, Left ; physiology ; Atrial Function, Right ; physiology ; Cardiac Pacing, Artificial ; Dogs ; Electric Countershock

PURPOSE: The association between pulmonary vein (PV) dilatation and stroke in non-valvular atrial fibrillation (AF) patients remains unknown. MATERIALS AND METHODS: We examined the left atrium (LA) and PV in control (n=138) and non-valvular AF patients without (AF group, n=138) and with non-hemorrhagic stroke (AF with stroke group, n=138) using computed tomography. RESULTS: The LA, LA appendage (LAA), and all PVs were larger in the AF than control patients. The orifice areas of the LAA (5.6+/-2.2 cm2 vs. 4.7+/-1.7 cm2, p<0.001), left superior PV (3.8+/-1.5 cm2 vs. 3.4+/-1.2 cm2, p=0.019), and inferior PV (2.3+/-1.0 cm2 vs. 1.8+/-0.7 cm2, p<0.001) were larger in the AF with stroke than in the AF only group. However, right PVs were not different between the two groups. In a multivariate analysis, the orifice areas of the left superior PV [odds ratio (OR) 1.25, 95% confidence interval (CI) 1.03-1.51, p=0.02], left inferior PV (OR 1.97, 95% CI 1.41-2.75, p<0.001), and LAA (OR 1.30, 95% CI 1.13-1.50, p<0.001) were independent predictors of stroke. CONCLUSION: Compared to the right PVs, the left PVs and LAA exhibited more significant enlargement in patients with AF and stroke than in patients with AF only. This finding suggests that the remodeling of left-sided LA structures might be related to stroke.
Aged ; Atrial Appendage/physiopathology/*radiography ; Atrial Fibrillation/*complications/diagnosis/physiopathology ; Atrial Function, Right/*physiology ; Female ; Heart Atria ; Humans ; Male ; Middle Aged ; Multidetector Computed Tomography/*methods ; Multivariate Analysis ; Odds Ratio ; Predictive Value of Tests ; Prognosis ; Pulmonary Veins/physiopathology/*radiography ; Stroke/diagnosis/*etiology ; Tomography, X-Ray Computed/methods