Cryoablation System Temperature Control via Refrigerant Phase Mixing
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Solution Overview
Problem
Current cardiac cryoablation systems lack control over minimum temperature and cooling/thawing rates, limiting the ability to extend the thawing phase and ensure complete tissue destruction during procedures.
Innovation Solution
A system with a fluid delivery conduit, subcooler, and bypass fluid flow path, along with valves to control the ratio of gaseous to liquid refrigerant, allowing for adjustable temperature settings between approximately −20° C. and −25° C., enabling full control over freeze duration, treatment temperature, cooling and thawing rates, and the number of freeze-thaw-freeze cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If current cardiac cryoablation systems operate at controlled refrigerant flow, then the treatment element reaches the lowest achievable temperature, but the operator cannot control the minimum temperature or cooling and thawing rates
Solution Approach 1:
The system dynamically adjusts refrigerant flow characteristics by switching between liquid and gaseous refrigerant delivery modes. This allows the treatment element temperature to be dynamically controlled across a range rather than fixed at a single minimum temperature, enabling operators to adjust cooling and thawing rates as needed for different treatment requirements.
Solution Approach 2:
The invention changes the physical state parameter of the refrigerant from exclusively liquid to a selectable mix of liquid and gaseous phases. By controlling the phase state and flow rate of refrigerant delivered to the treatment element, the system achieves variable temperature control and adjustable cooling/thawing rates, directly addressing the operator control limitation.
2Reliability
If the thawing phase is extended by maintaining treatment element temperature between −20° C. and −25° C., then more complete cell destruction is achieved, but current systems cannot maintain this temperature range due to lack of control
Solution Approach 1:
The system changes the refrigerant delivery parameter from fixed liquid flow to variable phase composition (liquid/gas ratio). This enables precise maintenance of the treatment element temperature within the −20° C. to −25° C. range, ensuring complete cell destruction while giving operators control over the thawing phase duration and temperature profile.
Solution Approach 2:
The system provides dynamic control over temperature parameters during the thawing phase. By adjusting the refrigerant flow characteristics in real-time, operators can maintain the treatment element within the optimal temperature range for extended periods, ensuring reliable and complete tissue destruction.
3Power
If the treatment element reaches minimum temperature with controlled refrigerant flow, then cooling efficiency is maximized, but the operator cannot adjust cooling and thawing rates
Solution Approach 1:
The invention changes the refrigerant flow parameter from fixed liquid flow rate to variable phase composition and flow rate. This allows the system to deliver maximum cooling power when needed (liquid refrigerant) while also enabling controlled thawing rates (gaseous refrigerant or reduced flow), giving operators full control over the thermal profile during both cooling and thawing phases.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for more precise control over cryoablation parameters, enhancing tissue destruction and reducing the likelihood of reconduction by extending the thawing phase and minimizing collateral damage.
Implementation Method 1
a subcooler located between the upstream fluid flow path and the downstream fluid flow path
Implementation Method 2
Adjusting the ratio of gaseous refrigerant to liquid refrigerant may selectively control the temperature of the treatment element
Implementation Method 3
extending the thawing phase of a cryoablation procedure by creating a temperature plateau at a mildly cold temperature
Implementation Method 4
cooling tissue to sub-lethal temperatures is commonly used in electrophysiology studies
Data Source
AI summary
A system and method for providing greater control over the temperature of a thermal treatment element of a medical device, enabling an operator to extend a thawing period of a cryoablation procedure. The system may include a fluid flow path that bypasses a subcooler, giving the operator selective control over the temperature of refrigerant delivered to the treatment element and, therefore, treatment element temperature. Additionally or alternatively, the system may include a fluid delivery conduit that is in communication with a liquid refrigerant and a gaseous refrigerant. Adjustment of the ratio of liquid to gaseous refrigerant also offers control over the treatment element temperature. Additionally or alternatively, the system may include one or more valves and/or heating elements in the fluid delivery and recovery conduits to control the treatment element temperature.