초록 ▼

A cryoablation device having a pressure monitoring system includes an elongated catheter tube that has a central lumen and is formed with a closed distal end. The distal end of a refrigerant supply line is positioned in the central lumen and distanced from the catheter tube's distal end to establish

A cryoablation device having a pressure monitoring system includes an elongated catheter tube that has a central lumen and is formed with a closed distal end. The distal end of a refrigerant supply line is positioned in the central lumen and distanced from the catheter tube's distal end to establish an expansion chamber therebetween. A return line, which can be established between the supply line and the catheter tube or can include a return tube, is provided to exhaust expanded refrigerant from the chamber. First and second pressure sensors are respectively positioned in the supply line upstream from the expansion chamber and in the return line. Typically, both sensors are positioned to remain at extracorporeal locations throughout a cryoablation procedure. Measured pressures are used together with the supply and return line dimensions to analytically estimate the chamber pressure and allow the expansion of refrigerant in the chamber to be monitored.

대표청구항 ▼

What is claimed is: 1. A cryoablation device having a pressure monitoring system, said device comprising: a refrigerant supply unit; an elongated catheter tube having a central lumen and formed with a closed distal end; a supply line having a proximal end connected to said refrigerant supply unit a

What is claimed is: 1. A cryoablation device having a pressure monitoring system, said device comprising: a refrigerant supply unit; an elongated catheter tube having a central lumen and formed with a closed distal end; a supply line having a proximal end connected to said refrigerant supply unit and a distal end disposed in said central lumen of said catheter tube and distanced from the distal end thereof to establish an expansion chamber therebetween, said supply line for delivering a refrigerant from said refrigerant supply unit to said expansion chamber for expansion therein; a return line in fluid communication with said expansion chamber for exhausting refrigerant from said expansion chamber; a first pressure sensor for measuring a supply pressure, P s, in said supply line at a pre-selected distance upstream from said expansion chamber; a second pressure sensor for measuring a return pressure, Pr, in said return line at a pre-selected distance downstream from said expansion chamber; and a control unit connected to said first pressure sensor and to said second pressure sensor for using said measured pressures Ps and Pr for determining a pressure in said expansion chamber to monitor the expansion of said refrigerant therein. 2. A device as recited in claim 1 wherein said return line comprises a return tube having a distal end disposed in said central lumen of said catheter tube. 3. A device as recited in claim 2 wherein said distal end of said return tube is positioned to be substantially coterminous with said distal end of said supply line. 4. A device as recited in claim 1 wherein said catheter tube has an inner surface, said supply line has an outer surface and said return line is established between said inner surface of said catheter tube and said outer surface of said supply line. 5. A device as recited in claim 1 wherein said supply line comprises a supply tube and a capillary tube, said supply tube is formed with a lumen having a lumen diameter, D, and said capillary tube is formed with a lumen having a lumen diameter, d, with D >d. 6. A device as recited in claim 5 wherein said supply tube and said catheter tube are arranged co-axially. 7. A device as recited in claim 1 wherein said control unit further comprises: a means for comparing the pressure in said expansion chamber with a reference pressure to create an error signal; and a means for varying said supply pressure, Ps, to make the error signal a nullity. 8. A device as recited in claim 7 further comprising an alarm means responsive to the error signal for shutting down the flow of refrigerant from said refrigerant supply unit and into said supply line when the error signal attains a predetermined value. 9. A system for monitoring pressure in an expansion chamber of a cryoablation catheter, said catheter having a supply line for delivering a refrigerant to said expansion chamber for expansion therein and a return line for exhausting expanded refrigerant therefrom, said system comprising: a first pressure sensor for measuring a supply pressure, P s, in said supply line at a pre-selected distance upstream from said expansion chamber; a second pressure sensor for measuring a return pressure, Pr, in said return line at a pre-selected distance downstream from said expansion chamber; and a control unit for using said measured pressures Ps and Pr to determine the pressure in said expansion chamber to monitor the expansion of said refrigerant therein. 10. A system as recited in claim 9 wherein said control unit is configured to use at least one supply line dimension and at least one return line dimension together with said measured pressures Ps and Pr to determine the pressure in said expansion chamber. 11. A system as recited in claim 10 wherein said system further comprises: an electronic means for comparing the pressure in said expansion chamber with a reference pressure to create an error signal; and a means for varying said supply pressure, Ps, to make the error signal a nullity. 12. A system as recited in claim 11 further comprising an alarm means responsive to the error signal for shutting down the flow of refrigerant from said refrigerant supply unit and into said supply line when the error signal attains a predetermined value. 13. A method for cryoablating tissue at a treatment site in the vasculature of a patient, said method comprising the steps of: providing an elongated catheter tube having a central lumen and formed with a closed distal end; positioning the distal end of a supply line in said central lumen of said catheter tube at a distance from said distal end thereof to establish an expansion chamber therebetween; advancing said distal end of said catheter tube through the patient's vasculature to the treatment site; introducing a refrigerant into said supply line for outflow from said distal end thereof and expansion in said expansion chamber; measuring a supply pressure, Ps, at an extracorporeal location in said supply line upstream from said expansion chamber; measuring a return pressure, Pr, at an extracorporeal location downstream from said expansion chamber; and using said measured pressures Ps and Pr to determine a pressure in said expansion chamber to monitor the expansion of said refrigerant therein. 14. A method as recited in claim 13 further comprising the step of positioning a return tube in said central lumen of said catheter, and wherein said step of measuring a return pressure, Pr, is accomplished by measuring a pressure within said return tube. 15. A method as recited in claim 14 wherein said distal end of said return tube is positioned to be substantially coterminous with said distal end of said supply line. 16. A method as recited in claim 13 wherein said catheter tube has an inner surface, said supply line has an outer surface and wherein said step of measuring a return pressure, Pr, is accomplished by measuring a pressure between said inner surface of said catheter tube and said outer surface of said supply line. 17. A method as recited in claim 13 wherein said supply line comprises a supply tube and a capillary tube, said supply tube is formed with a lumen having a lumen diameter, D, and said capillary tube is formed with a lumen having a lumen diameter, d, with D >d. 18. A method as recited in claim 17 wherein said supply tube and said catheter tube are arranged co-axially. 19. A method as recited in claim 13 further comprising the step of varying the flow of refrigerant into said supply line to obtain a pre-selected pressure in said expansion chamber.