End-fire guided ablation
An apparatus for forming a lesion in tissue along a desired ablation path includes a guide member having a tissue-opposing surface for placement against a heart surface. A guide carriage is sized to be received within the guide member and moveable therein along a longitudinal axis. The carriage is configured to receive an optical fiber extending substantially axially within the carriage and bend the fiber for a discharge tip of the fiber to aim through a bottom wall of the guide member. The carriage is further configured to bend the fiber toward said discharge tip with a curved portion subject to mechanical stress and a straight portion at the fiber discharge tip. The straight portion is selected to have a length to dissipate thermal stress arising from reflectance of light from the tissue back into the discharge tip.
1 . An apparatus for forming a lesion in tissue along a desired ablation path, said apparatus comprising:
a guide member having a tissue-opposing surface for placement against a heart surface, said guide member having interior surfaces and a longitudinal axis;
a guide carriage sized to be received within said guide member and moveable therein along said longitudinal axis;
said carriage configured to receive an optical fiber extending substantially axially within said carriage and bend said fiber for a discharge tip of said fiber to aim through a bottom wall of said guide member;
said carriage further configured to bend said fiber toward said discharge tip with a curved portion subject to mechanical stress and a straight portion at said fiber discharge tip, said straight portion selected to have a length to dissipate thermal stress arising from reflectance of light from said tissue back into said discharge tip.
2 . An apparatus according to claim 1 wherein said straight portion includes a distal portion at said fiber tip with a jacket of said fiber removed at said distal portion to expose a core of said fiber.
3 . An apparatus according to claim 1 wherein said fiber is disposed within a channel with said carriage, said channel adapted to receive a flow of coolant fluid.
4 . An apparatus according to claim 3 wherein said channel has a greater cross-sectional area in said curved portion than in said straight portion to increase a velocity of said flow in said straight portion.
5 . An apparatus according to claim 1 wherein said fiber is connected to a source of laser energy at a wavelength selected to reduced absorption in water.
6 . An apparatus according to claim 5 wherein said wavelength is selected for reduced absorption in myocardial tissue.
7 . An apparatus according to claim 5 wherein said wavelength is selected to be in a range selected from 790 nm to 830 nm and 1020 nm to 1140 nm.
8 . An apparatus according to claim 5 wherein said wavelength is selected to be 1064 nm.