Catheter ablation device with impedance monitoring
View Patent ↗The invention relates to a catheter ablation device for delivery of energy (such as microwave energy) via a radiating antenna to a selected region of tissue, the device having an elongated catheter with an outer sheath, configured to allow flow of fluid along the catheter to exit through one or more orifices adjacent to the antenna. The device includes an impedance monitoring system having two electrodes arranged respectively inside and outside said catheter sheath, the impedance monitoring system including an electric circuit incorporating an ionic conductivity path through said fluid. The device is introduced into a blood vessel and the invention allows monitoring of changes in the size of the blood vessel during an ablation procedure, as it can be used to measure the impedance of an electrical circuit including a blood path in the blood vessel in the region of the ablation, the measured impedance providing a measure of vascular calibre.
1 . A microwave catheter ablation device for delivery of energy to a selected region of tissue, the microwave catheter ablation device comprising:
an electrical feedline;
an antenna portion including a radiating antenna electrically connectable via the electrical feedline to a microwave generator and configured to generate an electromagnetic field comprising electromagnetic waves in a microwave energy spectrum able to ablate tissue in the selected region of tissue;
an elongated catheter having a distal tip, an outer sheath and one or more orifices formed through the outer sheath in or adjacent to the antenna portion, wherein the outer sheath is configured to allow a flow of fluid along the catheter to exit through the one or more orifices; and
an impedance monitoring system comprising first and second electrodes positioned along a length of the catheter at locations spaced apart from the distal tip, wherein the first and second electrodes are arranged respectively inside and outside the outer sheath and configured such that in use the impedance monitoring system applies an electrical signal to create an electric circuit incorporating an ionic conductivity path through the fluid between the first electrode and the second electrode via the one or more orifices and the impedance monitoring system measures the impedance of the ionic conductivity path;
wherein the second electrode is separate to the radiating antenna.
2 . The device of claim 1 , wherein the first and second electrodes are arranged proximal of the antenna portion.
3 . The device of claim 1 , wherein the first and second electrodes are electrically connectable to an impedance monitor configured to provide an indication to a user of the device of a measure of an impedance of the electric circuit.
4 . The device of claim 1 , wherein one or both of the first and second electrodes comprise ring or part-ring form electrodes.
5 . The device of claim 1 , wherein the first electrode arranged on the inside of the outer sheath is supported on an outside surface of the electrical feedline.
6 . The device of claim 1 , wherein the second electrode arranged on the outside of the catheter sheath is supported on an outside surface of the catheter sheath.
7 . The device of claim 1 , wherein one or both of the first and second electrodes is embedded into a wall of the catheter sheath.
8 . The device of claim 1 , wherein the outer catheter sheath is sized to provide sufficient internal free space around the feedline to allow a flow of fluid through the catheter from a proximal end and exiting the catheter through the one or more orifices at a distal end.
9 . The device of claim 8 wherein the one or more orifices are arranged radially around the outer sheath.
10 . The device of claim 1 , wherein the first and second electrodes are positioned at approximately at the same axial position along the catheter.
11 . The device of claim 1 , wherein the ionic conductivity path extends within the catheter from the first electrode to the one or more orifices and extends from the one or more orifices to the second electrode outside of the catheter.
12 . The device of claim 1 , wherein the first and second electrodes are each formed by stripped ends of wires, the wires running a length of the catheter from a proximal end of the catheter.