Recent advances in cryo technology have yielded positive results in the treatment of arrhythmias with cold energy delivered through a 7 French (Fr) catheter. Freezor®, a cryocatheter from CryoCath Technologies, has been in clinical use in Europe for the past two years. In that time, it has established a record of safety and effectiveness in the treatment of arrhythmias, particularly in peri-nodal procedures. The technology has also proven itself in an Investigational Device Exemption study held at 10 centers in the United States and 3 in Canada.

Pending FDA approval, Freezor® is expected to be available in the U.S. this year. With its demonstrated safety profile especially important when working around the atrioventricular (AV) node Freezor® represents a new paradigm in treatment alternatives for electrophysiologists.

Cryotherapy is the use of cooling and freezing in living tissue to affect cellular function and activity. To produce cryotherapeutic temperatures, heat energy is removed from the tissue, rather than injecting cold energy into the tissue. Multiple factors influence the effectiveness of catheter-based cryotherapy. Chief among these are: 1) tip contact [to remove heat from the tissue, the catheter tip must be in contact with the tissue]; 2) tip temperature [the catheter tip temperature applied determines if the cells are subjected to hypothermia or killed]; and 3) freeze duration [longer freeze times will cause more tissue damage].

During cryoablation, the removal of heat from the tissue creates a temperature gradient that extends from the catheter tip to the edge of the cryotherapy zone. At the tip/tissue interface of the catheter, the cryotherapy temperature can be either -30 ºC and -75 ºC, depending on the type of intervention (cryomapping or cryoablation). The temperature in the cryotherapy zone ranges from the sub-zero cryogenic temperature at the tip-tissue interface to body temperature at sites distant from the catheter tip. This zone is dynamic as it expands during freezing and shrinks upon re-warming. In living tissue, vascularity always provides a heat source and will, as a result, cause local variations in temperature (Figure 1).