Figure 3.

Effects of atrial cardiomyocyte-specific Tnf ablation on electrical properties on exercise-induced arrhythmias and electrical changes in isolated atria. (A) Representative field electrogram recordings from isolated (denervated) atria in Nppa-Cre+ and Cre− sedentary and exercised mice showing atrial arrhythmia inducibility. Note evidence of sustained AF episodes in Cre− exercised mice only. (B) Atrial-specific Tnf ablation (Nppa-Cre+) reduced the sustained (>10 s) atrial arrhythmia inducibility (P value from 2 × 2 contingency table using Fisher’s exact test) in exercised mice (n-values indicated in figure panel). (C) Representative optically-mapped images of AF episodes from rapidly stimulated isolated atria during sinus rhythm (SR) (top panel) and during AF (bottom panel). (D and E) Typical isochrone activation maps and summary results of conduction velocity (CV) measured in right atrial appendages isolated from Nppa-Cre+ (n = 6) and Cre− (n = 7) swim-exercised mice revealed that CVs are slowed in Cre−, but not Nppa-Cre+ swim mice when compared to their sedentary counterparts (n = 8 and 6 per group, respectively). (F) In isolated atrial preparations, action potential duration at 90% of repolarization (APD₉₀) was prolonged in exercised compared to sedentary mice, in both Nppa-Cre+ and Cre− groups. The n value for individual groups is indicated on bar graphs. Data presented as mean ± S.e.m. P values from two-way ANOVA with Sidak’s multiple comparison tests. *P < 0.05; **P < 0.01; ***P < 0.001.