SMN1 and cardiac arrhythmia: Constant appearance of congenital septal defects, arrhythmia and cardiomyopathy are the most important cardiac phenotypes noticed in patients with severe SMA and SMA mouse models.32,33 Adding to this vascular defect such as distal digital necrosis, where the necrotic lesions occur at the distal aspects of fingers or toes are also commonly reported in severe SMA patients.34 Viral delivery systems carrying SMN (scAAV9-SMN) at the early post-natal stage prevented these cardiac severe defects and significantly improved the survival, suggesting the role of SMN in cardiovascular system.