CFTR and cardiac arrhythmia: Thus, although the two candidate genes CFTR and NOS1 have not been proven to directly cause arrhythmia, all the potential evidence listed above shows that these gene mutations can change some characteristics of atrioventricular node conduction by affecting the autonomic nervous system/neurotransmitter release or ion channels, which can lead to changes in cardiac depolarization, action potentials, cardiac conduction velocity, the refractory period, etc., and such changes will lead to dual AV node physiology and AVNRT.