Intra-atrial pressure increases rate and organization of waves emanating from the superior pulmonary veins during atrial fibrillation.

Abstract

Atrial fibrillation (AF) commonly associates with atrial dilatation by poorly understood mechanisms. We hypothesized that elevation of intra-atrial pressure elicits high-frequency and spatio-temporally organized left atrial (LA) sources emanating from the superior pulmonary veins. We used a stretch-related AF model in the sheep heart to induce stable episodes of AF (>40 minutes) in 9 animals. Video movies of the LA free wall (LAFW) and LA superior pulmonary vein junction (JPV) were obtained by using di-4-ANEPPS. Electrograms from the right atrium were recorded. At intra-atrial pressures >10 cm H2O, the maximum dominant frequency (DFMax) was significantly higher in the JPV than in the LAFW (12.0+/-0.2 and 10.5+/-0.2 Hz, respectively [mean+/-SEM]; P<0.001). Below 10 cm H2O, DFMax was similar in the JPV and LAFW (10.8+/-0.3 versus 10.2+/-0.3 Hz; P=0.6); DFMax in both JPV and LAFW was significantly higher than in the right atrium (7.8+/-0.3 Hz; P<0.001). Analysis of excitation direction in JPV showed positive correlation between intra-atrial pressure and the number of waves emanating from the left superior pulmonary vein (r=0.79, P=0.02) but not from the LAFW (r=0.54, P=0.09). The number of spatio-temporally periodic waves in the JPV correlated with pressure (r=0.92, P=0.002). In 3 cases, JPV rotors were identified with a cycle length equal to 1/DFMax. We demonstrate for the first time that an increase in intra-atrial pressure increases the rate and organization of waves emanating from the superior pulmonary veins underlying stretch-related AF.