SMAD3 and atrial fibrillation: We also demonstrated that the phosphorylation levels of smad2 (p‐smad2) and smad3 (p‐smad3) were significantly higher in the atrial tissues of the AF‐control and AF‐AdNull groups than in the Sham group, and c‐Ski overexpression reversed these increases in p‐smad2 and p‐smad3 (Figure 4B and 4).