NGF and atrial fibrillation: Quantification revealed significant cell death in PC12 cells exposed to HMS-conditioned media from both AF culture (64.6% ± 4.2% viable; P = 0.003) and NP culture (57.2% ± 8.4% viable; P = 0.0018) compared to vehicle-treated control (88.7% ± 1.87% viable) or NGF-treated control (94.3% ± 1.9% viable) (Figure 5; LIVE/DEAD image panels).