A
catheter includes a
cryoablation tip with an electrically-driven
ablation assembly for heating tissue. The
cryoablation tip may be implemented with a
cooling chamber through which a controllably injected
coolant circulates to lower the tip temperature, and having an RF
electrode at its distal end. The RF
electrode may be operated to warm cryogenically-cooled tissue, or the
coolant may be controlled to conductively cool the tissue in coordination with an RF
treatment regimen, allowing greater versatility of operation and enhancing the
lesion size, speed or placement of multi-
lesion treatment or single
lesion re-treatment cycles. In one embodiment a
microwave energy source operates at a frequency to extend beyond the
thermal conduction depth, or to penetrate the cryogenic ice ball and be absorbed in tissue beyond an ice boundary, thus extending the depth and / or width of a single treatment locus. In another embodiment, the cooling and the application of RF energy are both controlled to position the
ablation region away from the surface contacted by the
electrode, for example to leave surface tissue unharmed while ablating at depth or to provide an
ablation band of greater uniformity with increasing depth. The driver or RF
energy source may supply
microwave energy at a frequency effective to penetrate the ice ball which develops on a cryocatheter, and different frequencies may be selected for preferential absorption in a layer of defined thickness at depth in the nearby tissue. The
catheter may operate between 70 and minus 70 degrees Celsius for different tissue applications, such as
angioplasty,
cardiac ablation and
tissue remodeling, and may preset the temperature of the tip or adjacent tissue, and otherwise
overlay or
delay the two different profiles to tailor the shape or position where ablation occurs or to speed up a treatment cycle.