NTRK1 and atrial fibrillation: The percentages of the TrkA-positive NP and AF cells in all groups showed little change until day 7, and the percentages of the TrkA-positive NP and AF cells in the punch group were increased significantly only on day 28 postoperatively (punch vs. sham, P < 0.01, punch vs. gel, P < 0.01, Fig. 4c,d).