How cryocatheter works ? Cryoagent, like nitric oxide is delivered through the small lumen to the tip of the ablation catheter. At the tip of the catheter nitric oxide's temperature increases due to the contact with warm heart tissue. Temperature of the gas drops as it expands and reaches about -70 C at the tip of the catheter. 

Single Cell Freezing

 Initially ice forms outside of the cell ( extracellular ice ), then inside of the cell  ( intracellular freezing ).  As ice crystals grows in size-they rupture cell membrane ( cell death ).