Comparison of Ca -handling properties of canine pulmonary vein and left atrial cardiomyocytes

Coutu, Pierre, Denis Chartier, and Stanley Nattel. Comparison of Ca -handling properties of canine pulmonary vein and left atrial cardiomyocytes. Am J Physiol Heart Circ Physiol 291: H2290–H2300, 2006. First published June 23, 2006; doi:10.1152/ajpheart.00730.2005.—Cardiac tissue in the pulmonary vein sleeves plays an important role in clinical atrial fibrillation. Mechanisms leading to pulmonary vein activity in atrial fibrillation remain unclear. Indirect experimental evidence points to pulmonary vein Ca handling as a potential culprit, but there are no direct studies of pulmonary vein cardiomyocyte Ca handling in the literature. We used the Ca -sensitive dye indo-1 AM to study Ca handling in isolated canine pulmonary vein and left atrial myocytes. Results were obtained at 35°C and room temperature in cells from control dogs and in cardiomyocytes from dogs subjected to 7-day rapid atrial pacing. We found that basic Ca -transient properties (amplitude: 186 28 vs. 216 25 nM; stimulus to half-decay time: 192 9 vs. 192 9 ms; atria vs. pulmonary vein, respectively, at 1 Hz), beat-to-beat regularity, propensity to alternans, -adrenergic response (amplitude increase at 0.4 Hz: 96 52 vs. 129 61%), number of spontaneous Ca transient events after Ca loading (in normal Tyrode: 0.9 0.2 vs. 1.3 0.2; with 1 M isoproterenol: 7.6 0.3 vs. 5.1 1.8 events/min), and caffeine-induced Ca -transient amplitudes were not significantly different between atrial and pulmonary vein cardiomyocytes. In an arrhythmia-promoting model (dogs subjected to 7-day atrial tachypacing), Ca -transient amplitude and kinetics were the same in cells from both pulmonary veins and atrium. In conclusion, the similar Ca handling properties of canine pulmonary vein and left atrial cardiomyocytes that we observed do not support the hypothesis that intrinsic Ca -handling differences account for the role of pulmonary veins in atrial fibrillation.