Inflammation depresses electrical conduction in normal heart tissue

Up to 40% of patients that undergo cardiac surgery will experience atrial fibrillation. Because it has been shown that there is an inflammatory response after open-heart surgery associated with elevated levels of arachidonic acid (AA), we postulated that inflammation leads to abnormal conduction and atrial fibrillation. We studied AA effects on conduction properties of canine atrial tissue. A piece of the right atrial free wall was placed in a tissue bath and a bipolar recording electrode was placed a known distance from a point stimulator. Control recordings revealed two groups, one with high conduction velocity (CV) (63.39±3.06 cm/sec) and one with low CV (36.48±0.34 cm/sec, p<0.05 vs. high CV). AA (80 μM) was superfused for 15 minutes, and then washed out. AA caused a significant and reversible decrease of 44% in the slow CV group (n=3) whereas in the other group (n=3), there was little observed change (12%). The group with slower baseline CV responded to AA, whereas the group with higher CV was unaffected by AA. We postulate that the group with higher CV demonstrated conduction properties along the fiber long axis, whereas the group with slower velocities indicated conduction transverse to the long axis.