Cryoablation: mechanism of action and devices

Abstract

Cryoablation refers to all methods of destroying tissue by freezing. Cryoablation causes cellular damage, death, and necrosis of tissues by direct mechanisms, which cause cold-induced injury to cells, and indirect mechanisms, which cause changes to the cellular microenvironment and impair tissue viability. Cellular injury, both indirect and direct, can be influenced by four factors: cooling rate, target temperature, time at target temperature, and thawing rate. In this review, the authors describe the mechanisms of cellular injury that occur with cryoablation, the major advantages and disadvantages of cryoablation compared with other thermal ablation techniques, and the current commercially available cryoablation ablation systems.

Figure

Cryoablation-induced injury. (a) During freezing, extracellular ice formation results in sequestration of free extracellular water, increasing the osmolarity of the extracellular space. This leads to cellular dehydration and cell shrinkage. Intracellular ice formation results in disruption of organelle and plasma membranes, impairing cellular function. (b) During thawing, extracellular ice melts before intracellular ice, creating an osmotic fluid shift of water into damaged cells, causing swelling and bursting. Growth of intracellular ice crystals can continue during thawing, exacerbating cellular damage. (c) Damage to the vascular endothelium results in tissue edema. Delayed cellular damage occurs because of the initiation of apoptosis by the cold-induced cellular injury. Thrombosis of blood vessels causes tissue ischemia, hindering repair. Inflammatory cells, including macrophages and neutrophils, remove damaged cells and clear cellular debris.