Whereas WT mice exposed to 14 days of Ang II infusion exhibited increased atrial fibrosis and concomitantly were noted for decreased threshold for atrial fibrillation, CD11b−/− mice not only displayed attenuated atrial PMN accumulation after Ang II treatment, but also less fibrosis, which translated into reduced susceptibility to atrial fibrillation. This evidence concerns the gene AGT and atrial fibrillation.