WO2003059428A1

WO2003059428A1 - Endovascular catheter and method for temperature measurement

Info

Publication number: WO2003059428A1
Application number: PCT/GR2002/000069
Authority: WO
Inventors: Christodoulos Stefanadis
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-12-28
Filing date: 2002-12-23
Publication date: 2003-07-24
Anticipated expiration: 2004-06-28
Also published as: GR1004169B; AU2002350983A1

Abstract

Endovascular temperature measurement catheter for the coronary sinus/vagina of the heart and other veins of the circulatory system (such as renal, hepatic and others). The catheter comprises an elongated catheter body with an internal lumen, an elastic section (6) the distal end of which comprises one or more thermistors (3), a metallic stylet (1) throughout the length of the internal lumen one end of which is secured on the elastic section whereas the other is secured to a steering gear which is placed at the proximal end of catheter body. The thermistor is connected through its leads with temperature measurement instruments. By pulling the steering gear the elastic section of the catheter can be turned/bended up to 180°, thus making possible the approach of the desired place. By pushing the steering gear forward, the elastic section returns to its straight position.

Description

Endovascular catheter and method for temperature measurement

The present invention relates to an endovascular catheter for temperature measurement and more specifically to an endovascular catheter for the temperature measurement of the coronary sinus of the heart and other veins of the circulatory system (such as renal, hepatic and others) as well as to a method for such temperature measurement.

Rupture of the plaque occurs frequently during the evolution of coronary atherosclerotic lesions and is the most frequent cause of acute coronary syndromes. The risk of plaque disruption depends more on the composition of the plaque than on plaque size and stenosis severity. Other major determinants for the vulnerability of plaque rupture are the size and consistency of the lipid-rich atheromatous core, the thickness of the fibrous cap covering, and ongoing inflammation and repair within the cap. Plaque vulnerability (intrinsic disease) and rupture triggers (extrinsic forces) are important for plaque disruption. Furthermore, plaques that have undergone disruption and, by inference, plaques at risk for disruption, tend to demonstrate outward vessel remodeling.

It is well accepted that coronary artery disease is linked to inflammatory method. Histologically, unstable atherosclerotic plaques contain activated macrophages and T lymphocytes, adhesion molecules, chemokines and cytokines, matrix-degrading enzymes, and prothrombotic factors. Markers of systemic inflammation like interleukins, soluble vascular and intercellular adhesion molecules (sV-CAM-1 , slCAM-1), plasma soluble selectins, and C-reactive protein (CRP), have been found to predict coronary events in individuals with coronary artery disease. CRP induces adhesion molecule expression in human endothelial cells, supporting the hypothesis that CRP may play a direct role in promoting the inflammatory component of atherosclerosis. Moreover, there is increasing evidence that inflammation is induced by prior exposure to infective agents like Chlamydia pneumoniae, citomegalovirus, or Helicobacter pylori.

Several invasive and noninvasive imaging techniques are available to assess atherosclerotic vessels. Most of the standard techniques identify luminal diameter, stenosis, wall thickness, and plaque volume; however, none can accurately characterize plaque composition and, therefore, identify the high-risk plaques.

The identification of individuals at risk for future cardiovascular events is more important than ever, as such patients can now be effectively treated. It has been shown that in a number of patients with coronary artery disease, an active inflammatory is present in atherosclerotic plaques. Recently, it was shown that inflammation is not only a local phenomenon restricted to the culprit atherosclerotic plaque, but, especially in patients with unstable angina inflammation, is widespread in the coronary arteries. These findings challenge the concept of a single vulnerable plaque in acute coronary syndromes. Therefore, techniques are needed for the detection of "vulnerable patients" rather than "vulnerable plaques".

It is hypothesized that a widespread inflammation may result in an increased temperature in the coronary sinus as blood is drained from the left coronary artery. It has been sought to investigate if there is increased blood temperature difference between the coronary sinus and right atrium in patients with significant stenoses in the left coronary artery compared to subjects without angiographically visible lesions with a new coronary sinus thermography catheter.

The recent findings regarding acute coronary syndromes indicate that rupture of the coronary atherosclerotic plaque is probably the most important mechanism underlying the sudden onset. It has been demonstrated that the risk of plaque rupture may depend more on plaque composition than on plaque size. Plaques rich in soft extracellular lipids and macrophages are possibly more vulnerable to plaque rupture. The goals of current research are to clarify which plaque is prone to rupture, how plaque disruption occurs, and how to prevent the sequel of facts that lead to this devastating outcome. The presence of the inflammatory method within the atherosclerotic plaques may be detected by identifying temperature heterogeneity within the culprit lesions.

Recording the temperature of the blood of the coronary sinus and other veins of the circulatory system, provides information regarding any increase in the temperature of the coronary network due to inflammatory atherosclerotic procedures. This recording though requires the ability of the catheter to approach the coronary sinus of the heart from a peripheral vein or any other vein of the coronary network (such as renal, hepatic and others). This is not possible with a common catheter because such a catheter would not have the ability, for example to be inserted in the coronary sinus of the heart, due to its shape.

There is therefore a need for a catheter that would have the ability to approach the right sinus of the heart and would be inserted in the coronary sinus or in other veins of the coronary network, which are inaccessible for common thermography catheters, in order to obtain temperature measurements.

It is an object of the present invention to provide such a catheter and a method to obtain accurate temperature measurements of the blood within the coronary sinus or in other normally inaccessible veins of the circulatory system.

To this effect the invention provides an endovascular catheter for temperature measurement of the coronary sinus of the heart and/or other veins of the circulatory system, comprising: an elongated catheter body enclosing throughout its whole length an internal lumen, said body having a proximal and a distal end, said distal end comprising a flexible elastic section and one or more thermistors, affixed to the surface of the elastic section in such a way as to allow the temperature measurement of body fluids coming in contact with it, a stylet made from appropriate metal passing throughout the whole length of said internal lumen, said stylet having one end secured to the elastic section while the other end is secured to a steering gear, placed at the proximal end of the catheter body and used for the external manipulation of the catheter's distal end, leads passing throughout the whole length of the internal lumen, one end of said leads being connected to the thermistor, while the other, passing through the steering gear, is connected through a plug to temperature measurement instruments, and wherein by puling the steering gear backwards, the flexible section of the catheter's distal end is controllably bent up to 180°, thus enabling the approach of a desired point in the coronary sinus of the heart and/or other veins of the circulatory system and the measurement of its temperature, while by pushing the steering gear forward, the flexible section of the catheter's distal end is brought back to its original straight position.

Furthermore the invention provides a method for the temperature measurement of the coronary sinus of the heart and/or other veins of the circulatory system comprising the following steps: i. inserting within a vein of a human body a catheter comprising an elongated catheter body enclosing throughout its whole length an internal lumen, said body having a proximal and a distal end, said distal end comprising a flexible elastic section (2) and one or more thermistors (3), affixed to the surface of the elastic section in such a way as to allow the temperature measurement of body fluids coming in contact with it, said catheter further comprising a stylet (1) made from appropriate metal passing throughout the whole length of said internal lumen, said stylet having one end secured to the elastic section (2) while the other end is secured to a steering gear (4), placed at the proximal end of the catheter body and used for the external manipulation of the catheter's distal end, said catheter further comprising leads (5) passing throughout the whole length of the internal lumen, one end of said leads being connected to the thermistor (3), while the other, passing through the steering gear (4), is connected through a plug to temperature measurement instruments, ii. advancing the catheter to the site of which the temperature is to be measured iii. controllably bending the distal end of the catheter by pulling backwards the steering gear, thus allowing the placement of said distal end within the coronary sinus of the heart or other veins of the circulatory system iv. obtaining a temperature measurement from the thermistor affixed to the distal end of the catheter body and connected to the temperature measurement instruments v. bringing the distal end of the catheter to its original straight position by pushing the steering gear forward and removing the catheter from the human body

The flexible elastic section at the distal end of the catheter has the ability, through external manipulation of the steering gear, to be bent up to 180°. This allows the approach of the catheter and the insertion of its distal end, which bears the thermistors, in places, such as the coronary sinus of the heart, that for other catheters would be impossible, and the measurement of the temperature at these places.

The thermography catheter is made from a non-thrombogenic material and comprises an elongated catheter body, whose distal end is elastic/flexible. One or more thermistors are affixed to the surface of this flexible section and serve in order to obtain the temperature measurement of bodily fluids coming into contact with the thermistors. The length of the catheter body and the elastic section depend on the use for which the catheter is intended. Over the whole length of the catheter there is an internal lumen through which passes a stylet. The stylet is made from metal or another type of appropriate material. It has two ends, one secured to the tip of the catheters distal end's elastic section and the other connected to a steering gear which is placed at the proximal end of the catheter's body and serves for the external manipulation of the catheter's distal end. The thermistor, through leads that pass through the internal lumen, is connected to temperature measurement instruments. These instruments comprise an interface module, connected to a microcontroller, that converts the analogue signal from the thermistor into digital, and a computer that receives this digital signal methodes it and measures the temperature which is then displayed on the computer screen.

The catheter is inserted in the human body and advanced to the area of which the temperature we need to measure. By pulling the steering gear backwards, the stylet causes the flexible distal end to bend. In this way the controllable bending of the catheter's distal end, up to 180° , is possible thus enabling the approach of the thermistor placed on the end of the catheter to the desired place whose temperature we wish to measure. Through the interface module and the computer connected to the thermistor, temperature measurement and recording of the blood located at an exact site, such as the coronary sinus of the heart, can be taken.

Embodiments of the invention will now be described, by way of example, with reference to the appended drawings. Figure 1 shows a first embodiment of the temperature measurement catheter in its original straight position.

Figure 2 shows a first embodiment of the temperature measurement catheter in a bent/turned position.

Figure 3 shows the temperature measurement catheter connected to the interface and the personal computer.

Figure 4 shows a second embodiment of the temperature measurement catheter, having two thermistors in a bent/turned position. Figure 5 shows a second embodiment of the temperature measurement catheter in its original straight position

It must be clarified that in Figures 1 , 2, 4, 5 not the whole length of the catheter is illustrated, but only the distal and proximal sections/ends of the catheter are shown.

The catheter of the example is made from polyurethane, has a total length of 90 cm and is used for measuring the temperature in the coronary sinus of the heart. The length of the catheter depends on the needs that arise from its use, and from the site whose temperature we wish to measure.

As shown in Figure 1 the catheter has an elongated body and comprises an internal lumen passing throughout its whole length. The distal end (2) of the catheter body has an elastic section (6). This has a length of 7 cm and comprises a thermistor (3) affixed on the surface of the elastic section (6) in such a way that it comes in contact with the body fluids of the site, the temperature of which we wish to measure. A metallic stylet (1) passes throughout the whole length of the internal lumen. This stylet is used for the external handling of the catheter's elastic section (6). One end of the metallic stylet (1) is secured to the end of the elastic section of the catheter (6) and the other is secured to a steering gear (4), which is placed at the proximal end of catheter.

The catheter is inserted to the fermoral vein (right or left) and is advanced through the inferior vena cava to the right atrium. By pulling backwards the steering gear at the proximal end of the catheter, the catheter's distal elastic section is bent controllably in order for the physician to approach the coronary sinus (as shown in Figure 2). The catheter's distal end is thus introduced in the coronary sinus of the heart thus allowing the measurement of the temperature from the thermistor (3) affixed to the distal end (2) of the catheter body. By pushing the steering gear (4) forward, the distal section of the catheter (6) comes back to its original position (drawing 1) and the catheter is removed from the human body. Thus, the shape of the catheter can be properly formed, so that the approach of the place whose temperature we want to measure can be achieved.

As shown in Figure 3, the catheter (7) is first connected to an interface module (8) and then to a computer (9). More specifically, the thermistor (3) (Figures 1&2) is connected through leads (5) that pass throughout the whole length of the internal lumen, and through a plug, with the interface module (8) (drawing 3), that converts an analogue signal from the thermistor (3) to digital. This signal is then sent to a computer (9) connected to the above-mentioned interface module. The computer (9) methodes it, measures and records the temperature, which is then displayed on the screen.

In a second embodiment (Figures 4, 5) a second thermistor (10) is affixed to the body of the catheter 7 cm away from the distal end. When the distal end of the catheter is inserted by 3 cm into the coronary sinus to measure the blood temperature, the thermistor at the distal end measures the temperature of the blood that runs out from the coronary sinus to the right atrium, while the second thermistor (10) measures the temperature of the blood inside the right atrium. In this way simultaneous temperature measurements can be made from two different sites of interest.

Claims

1. Endovascular catheter for temperature measurement of the coronary sinus of the heart and/or other veins of the circulatory system, comprising: an elongated catheter body enclosing throughout its whole length an internal lumen, said body having a proximal and a distal end, said distal end comprising a flexible elastic section (2) and one or more thermistors (3), affixed to the surface of the elastic section in such a way as to allow the temperature measurement of body fluids coming in contact with it, a stylet (1) made from appropriate metal passing throughout the whole length of said internal lumen, said stylet having one end secured to the elastic section (2) while the other end is secured to a steering gear (4), placed at the proximal end of the catheter body and used for the external manipulation of the catheter's distal end, leads (5) passing throughout the whole length of the internal lumen, one end of said leads being connected to the thermistor (3), while the other, passing through the steering gear (4), is connected through a plug to temperature measurement instruments, and wherein by puling the steering gear (4) backwards, the flexible section of the catheter's distal end is controllably bent up to 180°, thus enabling the approach of a desired point in the coronary sinus of the heart and/or other veins of the circulatory system and measurement of its temperature, while by pushing the steering gear forward, the flexible section of the catheter's distal end is brought back to its original straight position.

2. Endovascular catheter according to claim 1 , wherein the said temperature measurement instruments comprise an interface module (8) which converts an analogue signal received from the thermistor (3) to digital and a computer (9) which receives the digital signal, methodes it and calculates the temperature, which is then displayed on its screen.

3. Endovascular catheter according to claims 1 or 2, wherein a second thermistor is affixed to the catheter body, close to the distal end in a distance such that when the catheter's distal end is inserted inside the heart's coronary sinus to measure the blood temperature, the second thermistor measures the blood temperature inside the right atrium, thus providing simultaneous temperature measurement from two sites of interest.

4. Method for the temperature measurement of the coronary sinus of the heart and/or other veins of the circulatory system comprising the steps of: i. inserting within a vein of a human body a catheter comprising an elongated catheter body enclosing throughout its whole length an internal lumen, said body having a proximal and a distal end, said distal end comprising a flexible elastic section (2) and one or more thermistors (3), affixed to the surface of the elastic section in such a way as to allow the temperature measurement of body fluids coming in contact with it, said catheter further comprising a stylet (1) made from appropriate metal passing throughout the whole length of said internal lumen, said stylet having one end secured to the elastic section (2) while the other end is secured to a steering gear (4), placed at the proximal end of the catheter body and used for the external manipulation of the catheter's distal end, said catheter further comprising leads (5) passing throughout the whole length of the internal lumen, one end of said leads being connected to the thermistor (3), while the other, passing through the steering gear (4), is connected through a plug to temperature measurement instruments, ii. advancing the catheter to the site of which the temperature is to be measured iii. controllably bending the distal end of the catheter by pulling backwards the steering gear, thus facilitating contact of the catheter's distal end with the site of interest iv. obtaining a temperature measurement from the thermistor affixed to the distal end of the catheter body and connected to the temperature measurement instruments v. bringing the distal end of the catheter to its original straight position by pushing the steering gear forward and removing the catheter from the human body.

5. Method for the temperature measurement of the coronary sinus of the heart according to claim 4 but wherein in step i, the catheter is inserted within the femoral vein, in step ii, the catheter is advanced through the inferior vena cava to the right atrium and in step iii the controllable bending of the catheter's distal end by pulling backwards the steering gear, allows the placement of said distal end within the coronary sinus of the heart.