CN114469311B - Cryoablation system with temperature limiting function - Google Patents

Cryoablation system with temperature limiting function Download PDF

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CN114469311B
CN114469311B CN202111664041.7A CN202111664041A CN114469311B CN 114469311 B CN114469311 B CN 114469311B CN 202111664041 A CN202111664041 A CN 202111664041A CN 114469311 B CN114469311 B CN 114469311B
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temperature
freezing
flow
value
balloon
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CN114469311A (en
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冯骥
龚杰
彭博
韩博阳
刘翠鹄
王小龙
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Synaptic Medical Beijing Co Ltd
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Priority to PCT/CN2022/125981 priority patent/WO2023124426A1/en
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/02—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by cooling, e.g. cryogenic techniques
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00053—Mechanical features of the instrument of device
    • A61B2018/00214—Expandable means emitting energy, e.g. by elements carried thereon
    • A61B2018/0022—Balloons
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00315—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for treatment of particular body parts
    • A61B2018/00345—Vascular system
    • A61B2018/00351—Heart
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00571—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for achieving a particular surgical effect
    • A61B2018/00577—Ablation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00636—Sensing and controlling the application of energy
    • A61B2018/00696—Controlled or regulated parameters
    • A61B2018/00714—Temperature
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00636—Sensing and controlling the application of energy
    • A61B2018/00773—Sensed parameters
    • A61B2018/00791—Temperature
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00636—Sensing and controlling the application of energy
    • A61B2018/00773—Sensed parameters
    • A61B2018/00863—Fluid flow
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/02—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by cooling, e.g. cryogenic techniques
    • A61B2018/0212—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by cooling, e.g. cryogenic techniques using an instrument inserted into a body lumen, e.g. catheter

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Abstract

The invention provides a cryoablation system with a temperature limiting function and a cryoablation method, wherein the cryoablation system comprises a catheter, a fluid conveying unit and a control unit, a cryoballoon is arranged at the tail end of the catheter, the fluid conveying unit is used for conveying frozen liquid into the cryoballoon, the control unit comprises a temperature limiting loop, and the temperature limiting loop is used for controlling the fluid conveyed to the cryoballoon by the fluid conveying unit based on a preset temperature limiting value and the temperature of the cryoballoon, so that the temperature of the cryoballoon is not lower than the preset temperature limiting value. The cryoablation system avoids the phenomenon of adjacent tissue damage caused by too low freezing temperature in the process of pulmonary vein isolation ablation, and reduces the incidence rate of complications.

Description

Cryoablation system with temperature limiting function
Technical Field
The invention relates to the technical field of cryotherapy, in particular to a cryoablation system with a temperature limiting function and a cryoablation method.
Background
At present, the minimally invasive interventional technology of arrhythmia and other diseases is gradually becoming the main means for treating the arrhythmia, atrial fibrillation (atrial fibrillation) is one of the most common clinical tachyarrhythmia, the total incidence of atrial fibrillation in China is about 0.7 percent, and the incidence of the atrial fibrillation increases year by year along with the aging of population. In the aspect of atrial fibrillation treatment, the curative effect of catheter ablation on atrial fibrillation is well known, and Pulmonary Vein Isolation (PVI) is a foundation stone for catheter ablation treatment of atrial fibrillation. Cryoballoon ablation (CBA) is a new ablation method that has emerged in recent years and has become one of the standard methods for achieving PVI. A plurality of researches prove that CBA has good safety and effectiveness in treating atrial fibrillation, and has the advantages of short learning curve, less serious complications, low rate of hospitalization, and the like.
The mechanism of cryoablation is to cause target myocardial cell necrosis by low temperature caused by freezing energy, thereby achieving the treatment effect. The damaging effects of freezing can be classified as transient or permanent; the transient effect refers to cell stress state caused by temperature reduction to not lower than-20 deg.C and cell hypofunction caused by cell osmotic pressure change, and has recoverable property. The permanent effects of cryoablation include direct and indirect cell damage caused by cryogenics, where direct cell damage is mainly caused by the formation and breakdown of ice crystals inside and outside the cell at cryogenics; when the temperature is reduced to-20 ℃ to-15 ℃, the extracellular fluid gradually tends to be completely frozen, and the osmotic pressure of the extracellular fluid is suddenly increased, so that the intracellular dehydration is serious, and further, cell membranes and organelles are damaged; when the temperature is reduced to below-40 ℃, the intracellular liquid begins to freeze, which causes the damage of cell structure, the rupture of cell membrane and the inactivation of intracellular protein, thereby causing irreversible cell damage; indirect cellular damage by cryoablation is mainly mediated by blood vessels.
Mention of the expert consensus 2020 of China for atrial fibrillation ablated by cryoballoon catheter: the main factors that determine cryoablation effectiveness include (1) minimum temperature; (2) the cooling speed is increased; (3) the rewarming speed; (4) freezing time; (5) the number of times of freezing; (6) degree of contact and local blood flow. The lowest temperature is the main factor for determining the icing in the cells, and the freezing depth can be increased by 0.38mm when the temperature is reduced by 10 ℃. Evaluation of temperature for cryoablation safety: if the freezing temperature is too low, unnecessary damage to tissue outside the pulmonary vein may occur, increasing the incidence of complications. CBA is used for treating main complications of atrial fibrillation, such as phrenic nerve injury and esophageal injury, which are caused by excessive cryoablation. It is generally considered reasonable to strictly control the minimum freezing temperature to within-55 ℃.
However, the only atrial fibrillation cryoablation system on the market at present adopts fixed flow to carry out cryoablation; that is, doctors need to pay attention to the temperature displayed by the system all the time during the operation, when the temperature is lower than-55 ℃ (note that different operators have slight difference for the selection of the specific lowest temperature value), the operators need to manually operate the equipment to stop the ablation, and the operation is very inconvenient; at the same time, the risk of untimely treatment due to distraction exists, so that when the freezing temperature is lower than-55 ℃, not only can the adjacent tissues be damaged, but also the incidence rate of complications is higher.
Disclosure of Invention
Accordingly, the present invention is directed to a cryoablation system and method with temperature limiting function to solve one or more of the problems of the prior art.
According to one aspect of the present invention, a cryoablation system with temperature limiting functionality is disclosed, the system comprising:
the cryoablation system with the temperature limiting function is characterized by comprising a catheter, a fluid conveying unit and a control unit, wherein a freezing balloon is arranged at the tail end of the catheter, the fluid conveying unit is used for conveying freezing liquid into the freezing balloon, the control unit comprises a temperature limiting loop, and the temperature limiting loop is used for controlling the fluid conveyed to the freezing balloon by the fluid conveying unit based on a preset temperature limiting value and the temperature of the freezing balloon, so that the temperature of the freezing balloon is not lower than the preset temperature limiting value.
In some embodiments of the invention, the temperature limiting circuit comprises: the temperature acquisition device is used for acquiring the temperature of the freezing sacculus, the temperature comparison module is used for comparing the temperature of the freezing sacculus with the difference value of the preset temperature limit value with a preset temperature difference threshold value, and the regulating quantity calculation module is used for calculating the flow regulating value based on the temperature of the freezing sacculus acquired by the temperature acquisition device and the preset temperature limit value.
In some embodiments of the invention, the control unit comprises:
a pressure control circuit for controlling the fluid delivered by the fluid delivery unit to the cryoballoon via the pressure control circuit; and/or
And the flow control circuit controls the fluid delivered to the freezing balloon by the fluid delivery unit through the pressure control circuit when the difference value between the temperature of the freezing balloon and the preset temperature limit value is greater than the preset temperature difference threshold value.
In some embodiments of the present invention, the,
the flow control loop includes: the flow collecting device is used for collecting the flow of the freezing liquid flowing through the freezing saccule, and the flow comparing module is used for comparing the collected flow with a target flow value;
the pressure control loop comprises a pressure detection device, a driver and a proportional valve, the pressure detection device is used for collecting the pressure of the freezing liquid flowing through the freezing saccule, and the driver controls the proportional valve based on the pressure collected by the pressure detection device.
In some embodiments of the present invention, the flow adjustment value is calculated by the formula:
ΔQ＝a*(T-T k )+b*(T k -T k-1 )；
wherein, is Δ Q 1 Is a flow regulation value; a is 、 b are all coefficients; t is a preset temperature limit value; t is k The temperature of the freezing saccule at the current moment; t is k-1 The temperature of the freezing saccule before the time of delta t, and the value range of delta t is 0.5 s-3 s.
In some embodiments of the present invention, the,
when the flow is regulated for the first time, the value range of a is 10 to 50, and the value range of b is-500 to-1000;
when the flow is regulated after the first time, the value range of a is 10-50, and the value range of b is-10 to-50.
In some embodiments of the present invention, the preset temperature limit value is a parameter pre-stored in the control unit, and can be set through a human-computer interaction module of the control unit.
According to another aspect of the present invention, there is also disclosed a method of limiting the minimum temperature of a cryoballoon, the method comprising: and controlling the fluid delivered to the freezing balloon by the fluid delivery unit based on a preset temperature limit value and the acquired temperature of the freezing balloon, so that the temperature of the freezing balloon is not lower than the preset temperature limit value.
In some embodiments of the present invention, controlling the fluid delivered to the cryoballoon by the fluid delivery unit based on the preset temperature limit and the collected temperature of the cryoballoon comprises:
collecting the temperature of the freezing saccule in real time, and calculating the difference value between the temperature of the freezing saccule and a preset temperature limit value;
judging whether the difference value between the temperature of the freezing saccule and a preset temperature limit value is larger than a preset temperature difference threshold value or not;
and under the condition that the difference value between the temperature of the freezing balloon and the preset temperature limit value is not larger than the preset temperature difference threshold value, calculating a flow regulation value based on the preset temperature limit value and the collected temperature of the freezing balloon, and controlling the fluid delivered to the freezing balloon by the fluid delivery unit based on the flow regulation value.
In some embodiments of the present invention, the flow adjustment value is calculated by the formula:
ΔQ＝a*(T-T k )+b*(T k -T k-1 )；
wherein, the delta Q is a flow regulating value; a is 、 b are all coefficients; t is a preset temperature limit value; t is k The temperature of the freezing saccule at the current moment; t is k-1 The temperature of the freezing saccule before the time of delta t, and the value range of delta t is 0.5 s-3 s.
The cryoablation system with the temperature limiting function and the cryoablation method limit the temperature of the cryoballoon to be not lower than a preset temperature limit value through the temperature limiting loop, so that the minimum temperature of the cryoballoon is kept in an ideal temperature range, a doctor does not need to pay attention to the temperature displayed by the system all the time in the operation process, and the attention of the doctor can be ensured to be concentrated; in addition, the system also prevents the over-ablation phenomenon caused by the over-low freezing temperature, avoids the damage of adjacent tissues, improves the safety of the system, and also reduces the incidence of complications such as phrenic nerve damage, esophagus damage, pulmonary vein stenosis and vagus nerve reflex with severe bradycardia.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
It will be appreciated by those skilled in the art that the objects and advantages that can be achieved with the present invention are not limited to the specific details set forth above, and that these and other objects that can be achieved with the present invention will be more clearly understood from the detailed description that follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. For purposes of illustrating and describing some portions of the present invention, corresponding parts of the drawings may be exaggerated, i.e., may be larger, relative to other components in an exemplary apparatus actually manufactured according to the present invention. In the drawings:
fig. 1 is a schematic structural diagram of a cryoablation system with temperature limiting capability according to an embodiment of the present invention.
Fig. 2 is a schematic structural view of a cryoablation apparatus according to an embodiment of the present invention.
Fig. 3 is a schematic interface diagram of a human-computer interaction module of a control unit according to an embodiment of the present invention.
Fig. 4 is a schematic control flow chart of a flow control loop according to an embodiment of the invention.
FIG. 5 is a control flow diagram of a temperature limiting loop according to an embodiment of the invention.
Fig. 6 is a graph comparing temperature curves with and without limitation of cryoablation minimum temperature.
Fig. 7 is a graph comparing flow curves for cryoablation cryotherapy with and without limiting cryoablation.
FIG. 8 is a schematic control flow diagram of a temperature limiting circuit according to another embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme according to the present invention are shown in the drawings, and other details not closely related to the present invention are omitted.
It should be emphasized that the term "comprises/comprising/comprises/having" when used herein, is taken to specify the presence of stated features, elements, steps or components, but does not preclude the presence or addition of one or more other features, elements, steps or components.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar parts, or the same or similar steps.
Fig. 1 is a schematic structural diagram of a cryoablation system with a temperature limiting function according to an embodiment of the present invention, and as can be seen from fig. 1, the cryoablation system at least includes a catheter, a fluid delivery unit and a control unit, the catheter is provided with a cryoballoon 100 at a distal end thereof, the fluid delivery unit is configured to deliver a cryogenic liquid into the cryoballoon 100, and the control unit includes a temperature limiting circuit, the temperature limiting circuit is configured to control a fluid delivered to the cryoballoon 100 by the fluid delivery unit based on a preset temperature limit value and a temperature of the cryoballoon 100, so that the temperature of the cryoballoon 100 is not lower than the preset temperature limit value.
In the process of cryoablation, the cryoablation instrument shown in fig. 2 is specifically needed to be used for completing the process, the cryoablation instrument mainly comprises a main machine 500 and sterile accessories, and the sterile accessories mainly comprise a coaxial fluid connecting pipe, a cable connecting wire, a manual retractor sleeve and the like; and the cryoablation instrument main body 500 mainly includes a control unit. When carrying out cryoablation, firstly preparing equipment according to the operation instruction of the cryoablation instrument, and connecting a cryoablation instrument host 500 with a cryoablation balloon catheter through a coaxial fluid connecting pipe and a cable connecting line; placing the balloon catheter into the left atrium of the human body according to the operation process, and positioning, inflating and plugging the balloon catheter; the temperature of the balloon surface can then be collected in real time by temperature collection device 210.
Specifically, the preset temperature limit value is a parameter pre-stored in the control unit, and can be set through a human-computer interaction module of the control unit. Besides setting a temperature limit value, a man-machine interaction module of the control unit can also realize the opening and closing of a temperature limit loop. The human-computer interaction module of the Control unit may include an industrial personal computer, a touch screen display and related software, and the display interface is as shown in fig. 3, as can be seen from fig. 3, the temperature limit value may be increased or decreased by operating a "+" - "key ON the touch display 510, and the temperature limit loop may be in an" ON "state or an" OFF "state by clicking a" Temp Control "button in the interface. When the temperature limiting circuit is in the "ON" state, the system can then limit the temperature of the cryoballoon 100 above a preset temperature value. The preset temperature limit value can be set according to the specific situation of an operator, and is generally set within the range of minus 40 ℃ to minus 60 ℃ at an interval of 1 ℃; in some cases, the default temperature limit for the temperature limit loop may also be set to-55 ℃, i.e., the safe temperature of the cryoablation system defaults to-55 ℃.
Furthermore, various system parameters in the operation process, such as the temperature in the saccule, the air inlet pressure, the ablation flow, the weight of the main machine gas cylinder, the ablation time and the like, can be displayed in real time on a display interface of the human-computer interaction module.
It should be understood that, the setting of the temperature limit value or the opening and closing of the temperature limit loop through the human-computer interaction module of the control unit in the above embodiments is only a preferred way, and in other examples, the temperature limit value may be adjusted through a mechanical knob switch, or the opening or closing of the temperature limit loop may be implemented through a mechanical button.
Illustratively, the temperature limiting circuit includes: the temperature control device comprises a temperature acquisition device 210, a temperature comparison module 220 and an adjustment amount calculation module 230, wherein the temperature acquisition device 210 is used for acquiring the temperature of the freezing balloon 100, the temperature comparison module 220 is used for comparing the acquired difference value between the temperature of the freezing balloon 100 and the preset temperature limit value with a preset temperature difference threshold value, and the adjustment amount calculation module 230 is used for calculating a flow adjustment value based on the temperature of the freezing balloon 100 acquired by the temperature acquisition device 210 and the preset temperature limit value.
The temperature acquisition device 210 may specifically be a balloon temperature sensor, and the balloon temperature sensor is used for monitoring a temperature parameter of the balloon during the ablation process. The 'preset temperature difference threshold value' is a parameter pre-stored in the system, and the parameter is used for judging whether the balloon temperature acquired by the balloon temperature sensor needs to be subjected to temperature limitation or not; for example, the current temperature of the balloon is denoted as T k The predetermined temperature limit is denoted T and the predetermined temperature difference threshold is denoted T 0 Then the current temperature T is set at this time k The difference obtained by subtracting the limit set temperature T is defined as Δ T, and the calculated Δ T and T are calculated 0 Comparing; when Δ T is less than T 0 Or equal to T 0 In this case, the temperature of the cryoballoon 100 needs to be limited by a temperature limiting circuit.
Exemplary, T 0 The value of (c) may range from 2 c to 10 c, and may vary from balloon to balloon. Assuming a preset temperature limit of-55 deg.C, and T 0 At 5 ℃, the initial balloon temperature is about 37 ℃ (i.e., body temperature) at the beginning of ablation, Δ T =37 ℃ (-55 ℃) =92 ℃, when the difference between the temperature of the cryoballoon 100 and the preset temperature limit is greater than T 0 The control unit of the system does not temperature limit the cryoballoon 100; and as the ablation proceeds, the balloon temperature becomes lower and lower, when the balloon temperature drops to-50 ℃, at = T 0 The system will switch to a temperature limiting closed loop control, i.e., the system limits the temperature of the cryoballoon 100 above a preset temperature limit via a temperature limiting circuit.
In an embodiment of the present invention, the control unit further includes: a pressure control circuit for controlling the fluid delivered by the fluid delivery unit to the cryoballoon 100 through the pressure control circuit. Referring to fig. 1, the pressure control circuit may include a pressure detection device 410, an actuator and a proportional valve 420, the pressure detection device 410 may be an intake pressure sensor for acquiring the pressure of the freezing liquid flowing through the freezing balloon 100 or the intake pressure of the freezing balloon, and the actuator controls the proportional valve 420 based on the pressure acquired by the pressure detection device 410, so as to further control the flow rate of the freezing liquid flowing through the freezing balloon 100, so as to achieve the purpose of limiting the minimum temperature of the freezing balloon 100.
In addition, the control unit may also include a flow control circuit that controls the fluid delivered by the fluid delivery unit to the cryoballoon 100 via the pressure control circuit when the difference between the temperature of the cryoballoon 100 and the preset temperature limit is greater than the preset temperature difference threshold. The flow control circuit specifically comprises a flow acquisition device and a flow comparison module 320, wherein the flow acquisition device 310 is used for acquiring the flow of the frozen liquid flowing through the freezing balloon 100, and the flow comparison module 320 is used for comparing the acquired flow with a target flow value. The flow collecting device can be a refrigerating medium mass flowmeter.
Further, the control unit of the cryoablation system can be implemented by a PLC (Programmable Logic Controller) for acquiring signals of the sensors, performing conversion processing, and performing Logic control. The PLC has the advantages of high reliability, easy programming, flexible configuration, convenient installation, high running speed and the like, and the control function can be realized by designing the PCBA besides being controlled by the PLC, so that the PCBA has larger expansibility and lower cost.
In the above embodiment, when the difference between the temperature of the cryoballoon 100 and the preset temperature limit value is greater than the preset temperature difference threshold, the temperature limit function does not need to be started, that is, the cryoablation system does not need to be subjected to the minimum temperature limit on the cryoballoon 100 by using a temperature limit circuit, and at this time, the cryoablation system is in a flow closed-loop control state. In the cryoablation system, because the structure of the working medium circulation pipeline is fixed, the delivery pressure of the frozen liquid directly determines the flow rate of the pipeline, and the indirect control of the flow rate can be realized by directly controlling the air inlet pressure. Referring to fig. 1, the flow control circuit is connected in series with the pressure control circuit, that is, during operation, the flow collecting device 310 collects the flow of the freezing liquid flowing through the freezing balloon 100 in real time, and further compares the collected flow value with a preset target flow value, and feeds back the comparison result to the pressure control circuit. A pressure sensor is arranged behind a proportional valve 420 of the pressure control circuit so as to realize quick feedback, the comparison result of the flow control circuit can further regulate the intake pressure through closed-loop control conversion, and a proportional valve driver quickly regulates the intake pressure to the specified pressure, so that the aim of stabilizing the flow is fulfilled.
It should be noted that, in the flow control ablation process, the target pressure of the proportional valve 420 controller is set in a linear acceleration mode at the beginning of the process of flow control ablation, that is, the maximum flow control is performed, so that the balloon flow is rapidly increased, and the temperature is rapidly decreased; and after the linear pressurization is finished, flow control is carried out, a 0.5s sampling and flow adjusting period is set, and the flow of the frozen liquid is adjusted by adjusting the given value of the inlet pressure every 0.5 s. Referring to fig. 4, when the system is operating in a closed flow loop, the system performs ablation at a steady flow rate, at which point the monitored balloon temperature is only displayed on the interactive interface, and the system performs ablation at the maximum flow rate enabled throughout the ablation process until the ablation is complete. At this time, the state of "Temp Control" on the corresponding display interface is "OFF", which means that the temperature limiting circuit does not operate at this time. It should be noted that the target flow rates for different sized balloon catheters may vary, for example, a 28mm diameter balloon catheter may be used at 7200sccm, while a 23mm diameter balloon catheter may be used at 6200sccm.
Further, the flow regulation value is calculated by the formula: Δ Q = a (T-T) k )+b*(T k -T k-1 ) (ii) a Wherein, the delta Q is a flow regulating value; a is a 、 b are all coefficients; t is a preset temperature limit value; t is k Is the temperature of the cryoballoon 100 at the current time; t is a unit of k-1 The temperature of the cryoballoon 100 before the time Δ t, where Δ t ranges from 0.5s to 3s. Wherein, when the flow is regulated for the first time, the value range of a is 10-50, and the value range of b is-500 to-1000; when the flow is regulated after the first time, the value range of a is 10-50, and the value range of b is-10 to-50.
To further increase the rate of temperature limitation of the cryoballoon 100, a step-wise difference calculation may be used, first intervening in a temperature-limited closed-loop-controlled flow calculation: delta Q 1 ＝a 1 *(T-T k )+b 1 *(T k -T k-1 ) At this time a 1 Has a value range of 10 to 50,b 1 The value range of (a) is-500 to-1000; and after the initial flow rate adjustment, the difference of the flow rates is calculated in a manner that Δ Q = a (T-T) k )+b*(T k -T k-1 ) And the value range of a is 10-50, and the value range of b is-10 to-50. In this embodiment, the selection of Δ t determines the dynamic performance of the control system, and is limited by the inherent response characteristics between cryoablation system inlet pressure-flow-balloon temperature, and is also related to the monitoring (sampling) frequency and data transfer of the system, and the response time of the proportional valve 420. However, researches show that the value range of delta t is more suitable between 0.5s and 3s in order to achieve good control effect (the temperature can be quickly inserted into a temperature limiting closed loop, the temperature fluctuation is small, the temperature is quick and stable and is not lower than the set limiting temperature, and the flow fluctuation is small and is reduced in a stable process). It is not difficult to understand Δ t, a of balloon catheters with different diameters 1 、b 1 The specific sizes of a and b are also different.
Correspondingly, the invention also discloses a method for limiting the lowest temperature of the freezing balloon, which comprises the step of controlling the fluid delivered to the freezing balloon by the fluid delivery unit based on the preset temperature limit value and the temperature of the freezing balloon, so that the temperature of the freezing balloon is not lower than the preset temperature limit value.
Referring to fig. 5, after the ablation is started, the temperature of the balloon is acquired in real time through a temperature acquisition device, and the difference value between the temperature of the freezing balloon and a preset temperature limit value is calculated; and comparing the difference value between the actual temperature of the freezing saccule obtained by calculation and the preset temperature limit value with a preset temperature difference threshold value, namely judging whether the difference value between the temperature of the freezing saccule and the preset temperature limit value is greater than the preset temperature difference threshold value. And under the condition that the difference value between the temperature of the freezing saccule and the preset temperature limit value is equal to or less than a preset temperature difference threshold value, and the temperature of the saccule is close to the preset temperature limit value at the moment, switching to temperature closed-loop control, namely specifically calculating a flow regulation value based on the preset temperature limit value and the temperature of the freezing saccule, and controlling the fluid conveyed to the freezing saccule by the fluid conveying unit based on the flow regulation value. In other words, when the system is in a temperature closed-loop control state, the temperature of the balloon is ensured to be not lower than the set safety limit temperature by reducing the delivery amount of the refrigerant, so that the freezing injury caused by the over-low temperature is avoided until the ablation is finished.
In addition, the system operates in a closed flow loop until the actual temperature of the balloon is not close to the preset temperature limit (the difference between the actual temperature and the limit temperature is greater than the temperature difference threshold).
Illustratively, the flow adjustment value is calculated by the formula: Δ Q = a (T-T) k )+b*(T k -T k-1 ) (ii) a Wherein, is Δ Q 1 Is a flow regulation value; a is 、 b are all coefficients; t is a preset temperature limit value; t is k Is the temperature of the cryoballoon 100 at the current time; t is k-1 The temperature of the cryoballoon 100 before the time Δ t, where Δ t ranges from 0.5s to 3s.
According to the system and the method for cryoablation, the flow closed loop and the temperature limit closed loop are controlled in a double mode, the requirement of the cryoablation for treating atrial fibrillation on cooling capacity is met on the premise that the cryoablation damage caused by excessive ablation due to too low temperature is avoided, and the safety of the system is improved. In addition, because the division of the cardiac electrophysiology and pacing of the Chinese medical society and the specialized committee of the rhythm of the heart of the Chinese physician association advocate and organize the written 'China specialist consensus 2020 for atrial fibrillation ablated by the cryoballoon catheter', the following complications related to cryoballoon ablation are mainly included: the four complications of phrenic nerve injury, esophageal injury, pulmonary vein stenosis, cardiac tamponade, femoral artery injury, thrombus/air embolism and vagus nerve reflex with severe bradycardia are closely related to hypothermia and excessive ablation, and if the cryoablation system or the cryoablation method disclosed by the invention is adopted for cryoablation in the operation process, the temperature of the balloon can be ensured not to be lower than the safe temperature in the pulmonary vein isolation ablation process, and the injury of adjacent tissues is avoided, so that the incidence rate of the complications is reduced.
To further illustrate the advantages of the cryoablation system and method of the present invention, the following will by way of a specific example compare the two cases of limiting and not limiting the minimum temperature of the balloon, which are the same thermal load condition, with a temperature limit set at-40 ℃ and an ablation time of 180s.
FIG. 6 is a graph comparing the temperature curves for cryoablation with and without limiting the cryoablation minimum, from which it can be seen that the balloon temperature rapidly decreases without minimum temperature limiting of the balloon, and that after 30 seconds the system operates steadily in a balloon temperature interval below-40 deg.C, the minimum temperature being about-48 deg.C; after the balloon is subjected to minimum temperature limitation, the system quickly responds and stabilizes when the balloon temperature is close to-40 ℃, and the temperature is not lower than-40 ℃ in the whole process until the ablation is finished.
While fig. 7 is a comparison graph of flow curves for limiting and not limiting the cryoablation minimum temperature, referring to fig. 7, when the balloon is not limited to the minimum temperature, the balloon flow is rapidly increased to the target flow (the illustrated embodiment is a 28mm balloon, corresponding to a target flow of 7200 sccm) after the ablation is started, and the flow is kept stable during the whole ablation process; when the minimum temperature of the balloon is limited, the balloon flow is also rapidly increased to the target flow after the balloon starts to be ablated, the temperature is rapidly reduced, when the temperature is close to minus 40 ℃, the flow is reduced to be below 7200sccm, the balloon temperature is not reduced along with the ablation, meanwhile, the flow is gradually stabilized between 5500 and 6500, on the premise that the balloon temperature is not lower than the set safety limiting temperature, the freezing injury caused by the over-low temperature is avoided, and a certain freezing flow is maintained to ensure the effect of electrically isolating the pulmonary veins until the ablation is finished.
In addition, fig. 8 is a simpler temperature limiting process in another embodiment of the present invention, in which a limiting temperature can be set, and when the actual temperature of the balloon is detected to be lower than the temperature limiting value during the ablation process, the system automatically stops the ablation, cuts off the input of the freezing liquid, and the balloon enters the rewarming state.
Those of ordinary skill in the art will appreciate that the various illustrative components, systems, and methods described in connection with the embodiments disclosed herein may be implemented as hardware, software, or combinations of both. Whether this is done in hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. When implemented in hardware, it may be, for example, an electronic circuit, an Application Specific Integrated Circuit (ASIC), suitable firmware, plug-in, function card, or the like. When implemented in software, the elements of the invention are the programs or code segments used to perform the required tasks. The program or code segments may be stored in a machine-readable medium or transmitted by a data signal carried in a carrier wave over a transmission medium or a communication link. A "machine-readable medium" may include any medium that can store or transfer information. Examples of a machine-readable medium include an electronic circuit, a semiconductor memory device, a ROM, a flash memory, an Erasable ROM (EROM), a floppy disk, a CD-ROM, an optical disk, a hard disk, an optical fiber medium, a Radio Frequency (RF) link, and so forth. The code segments may be downloaded via computer networks such as the internet, intranet, etc.
It should also be noted that the exemplary embodiments mentioned in this patent describe some methods or systems based on a series of steps or devices. However, the present invention is not limited to the order of the above-described steps, that is, the steps may be performed in the order mentioned in the embodiments, may be performed in an order different from the order in the embodiments, or may be performed simultaneously.
Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments in the present invention.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes may be made to the embodiment of the present invention by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (5)

1. A cryoablation system with a temperature limiting function is characterized by comprising a catheter, a fluid conveying unit and a control unit, wherein a freezing balloon is arranged at the tail end of the catheter, the fluid conveying unit is used for conveying freezing liquid into the freezing balloon, the control unit comprises a temperature limiting circuit, and the temperature limiting circuit is used for controlling the fluid conveyed to the freezing balloon by the fluid conveying unit based on a preset temperature limiting value and the temperature of the freezing balloon, so that the temperature of the freezing balloon is not lower than the preset temperature limiting value;
wherein the temperature limiting circuit comprises: the temperature acquisition device is used for acquiring the temperature of the freezing saccule, the temperature comparison module is used for comparing the difference value between the temperature of the freezing saccule and the preset temperature limit value with a preset temperature difference threshold value, and the regulating quantity calculation module is used for calculating a flow regulating value based on the temperature of the freezing saccule acquired by the temperature acquisition device and the preset temperature limit value;
the calculation formula of the flow regulation value is as follows:
ΔQ＝a*(T-T k )+b*(T k -T k-1 )；
wherein, is Δ Q 1 Is a flow regulation value; a. b are all coefficients; t is a preset temperature limit value; t is k The temperature of the freezing saccule at the current moment; t is k-1 The temperature of the freezing saccule before the time of delta t, and the value range of delta t is 0.5 s-3 s.
2. The cryoablation system with temperature limiting capability of claim 1 wherein said control unit comprises:
a pressure control circuit for controlling the fluid delivered by the fluid delivery unit to the cryoballoon via the pressure control circuit; and/or
And the flow control circuit controls the fluid delivered to the freezing balloon by the fluid delivery unit through the pressure control circuit when the difference value between the temperature of the freezing balloon and the preset temperature limit value is greater than the preset temperature difference threshold value.
3. The cryoablation system with temperature limiting capability of claim 2,
the flow control loop includes: the flow collecting device is used for collecting the flow of the freezing liquid flowing through the freezing saccule, and the flow comparing module is used for comparing the collected flow with a target flow value;
the pressure control loop comprises a pressure detection device, a driver and a proportional valve, the pressure detection device is used for collecting the pressure of the freezing liquid flowing through the freezing saccule, and the driver controls the proportional valve based on the pressure collected by the pressure detection device.
4. The cryoablation system with temperature limiting capability of claim 1,
when the flow is regulated for the first time, the value range of a is 10 to 50, and the value range of b is-500 to-1000;
when the flow is regulated after the first time, the value range of a is 10-50, and the value range of b is-10 to-50.
5. The system of any one of claims 1 to 4, wherein the preset temperature limit value is a parameter pre-stored in the control unit and can be set by a human-machine interaction module of the control unit.
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