GAPDH and atrial fibrillation: The expression of cleaved caspase-3 protein (normalized to GAPDH) by immunoblotting in left atrial tissues of the MR AF patients (n = 6) was significantly higher than the expression of cleaved caspase-3 of the normal control subjects (n = 3) (0.20 ± 0.04 vs. 0.04 ± 0.02, p = 0.039) (Fig. 7c).