On Testing the Effectivity of a Cryoablation System in vitro and in vivo

摘要

Catheters for cryoablation of cardiac arrhythmias have become an important issue during the last years. The primary goal for cryocatheters is to create transmural lesions in the myocardium that inhibit spreading of certain arrhythmias such as atrial fibrillation. To operate cryocatheters, usually a complex system is required which controls flow and withdrawal of a proper refrigerant. The true efficiency of the freezing procedure (cooling power) depends on a series of physical parameters, such as the dimensions of the catheter, its tip and the supply lines or the thermodynamic state of the refrigerant entering the catheter. Thus, it is not straightforward to estimate cooling power. This study presents a cryosys-teni (console including a catheter) and uses an indirect approach to measure cooling power. For that purpose, a heating coil is wound around the catheter tip, and cooling power is determined from the amount of heating power required to compensate the freezing effect. In particular, the influence of a precool system on the cooling power is studied, and various characteristic numbers are calculated from the experiments. Furthermore, the presented cryosystem was tested in an "in vivo" experiment in an animal (swine). The lesions created in the operation were sent to a pathological institute for histologi-cal examination. Transmural necrosis was found where the catheter was in contact with myocardial tissue.