Adagio Medical has developed a new technology that makes it possible to manufacture ultra-low temperature cryoablation catheters with diameters smaller than 2mm. These catheters can be used by an electophysiologist to create endocardial, continuous, transmural lesions anywhere in the beating heart and without stopping the blood flow. Contrary to the term cryo-surgery that requires an open chest procedure with large-diameter cryoprobes the term ‘cryoablation’ refers to an endocardial catheter that can do therapeutic freezing of nearly any tissue and no longer requires an open surgical approach.
Near Critical Nitrogen (NCN) Technology
Our Near Critical Nitrogen (NCN) ultra-low temperature technology requires continuous and uninterrupted flow of the cryogen through a catheter. The liquid nitrogen is always maintained close to its critical point. When a fluid has both liquid and vapor phases present during a gradual increase in pressure, the system moves up along the liquid-vapor curve. An increased pressure causes the density of the liquid to decrease and the density of the vapor phase to increase, until they are exactly equal only at the critical point. However, vapor lock occurs anywhere on the liquid-vapor line beneath a few atmospheres of the critical point because of the associated massive volume expansion. Thus, the near-critical area can be described as a region where the density difference between liquid and gas is small or zero. This choice of parameters has three important implications:
- The cryogen always has high “liquid-like” density providing for efficient cooling rate.
- The heat capacity of a NCN is very high near its critical point which is especially important in endocardial application where the ultimate cooling power of a device is expected.
- The viscosity of NCN remains “gas-like,” that is, very low compared with “ordinary” liquids, resulting in very small hydrodynamic resistance even in tiny channels, hence making feasible practical use of very small and yet powerful catheters.
Combined, these unique properties of NCN enable creation of long and continuous lesions with full transmurality anywhere in the heart. This can be achieved via endocardial approach with small size catheters (≤9Fr).