Surgery – Diagnostic testing – Temperature detection
Reexamination Certificate
1999-07-01
2001-06-12
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Temperature detection
Reexamination Certificate
active
06245026
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to medical devices suitable for thermally mapping body vessel segments to locate hot spots (areas with elevated temperatures associated with high metabolic activity) within the vessel. In one particular application, intravascular thermography devices suitable for locating (and in some embodiments treating) vulnerable atherosclerotic plaque in body vessels are described.
BACKGROUND OF THE INVENTION
Cardiovascular disease is one of the leading causes of death worldwide. For example, some recent studies have suggested that plaque rupture may trigger 60 to 70% of fatal myocardial infarctions. In a further 25 to 30% of fatal infarctions, plaque erosion or ulceration is the trigger. Vulnerable plaques are often undetectable using conventional techniques such as angiography. Indeed, the majority of these vulnerable plaques that lead to infarction occur in coronary arteries that appeared normal or only mildly stenotic on angiograms performed prior to the infarction.
Studies into the composition of vulnerable plaque suggest that the presence of inflammatory cells (and particularly a large lipid core with associated inflammatory cells) is the most powerful predictor of ulceration and/or imminent plaque rupture. For example, in plaque erosion, the endothelium beneath the thrombus is replaced by or interspersed with inflammatory cells. Recent literature has suggested that the presence of inflammatory cells within vulnerable plaque and thus the vulnerable plaque itself, might be identifiable by detecting heat associated with the metabolic activity of these inflammatory cells. Specifically, it is generally known that activated inflammatory cells have a heat signature that is slightly above that of connective tissue cells. Accordingly, it is believed that one way to detect whether specific plaque is vulnerable to rupture and/or ulceration is to measure the temperature of the plaque walls of arteries in the region of the plaque.
Once vulnerable plaque is identified, the expectation is that in many cases it may be treated. Since currently there are not satisfactory devices for identifying vulnerable plaque, current treatments tend to be general in nature. For example, low cholesterol diets are often recommended to lower serum cholesterol (i.e. cholesterol in the blood). Other approaches utilize systemic anti-inflammatory drugs such as aspirin and non-steroidal drugs to reduce inflammation and thrombosis. However, it is believed that if vulnerable plaque can be reliably detected, localized treatments may be developed to specifically address the problems.
In view of the foregoing, improved catheters that facilitate the identification, location and mapping of inflamed plaque and/or other hot spots within arteries and/or other vessels would be desirable. Further, integrated catheter devices which are capable of both locating vulnerable plaque and delivering appropriate treatment agents would be desirable.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, a variety of improved thermal mapping catheters are disclosed which are capable of sensing and mapping thermal variations within body vessels. In embodiments directed at vascular applications, the catheters are capable of detecting temperature variations in atherosclerotic plaque, on the atherosclerotic plaque surface, and on the arterial wall of aneurysms and other vascular lesions (i.e. arteritis, vasculitis, inflammatory reaction, immunologic reaction, benign growth lesions, and malignant lesions) of the human vasculature.
In one aspect of the invention, a combined thermal mapping and drug delivery catheter is provided. In this embodiment a plurality of thermal sensors are combined with at least one infusion port suitable for delivering therapeutic agents into a vessel. In some embodiments, at least some of the infusion ports are located between adjacent thermal sensors.
In another aspect of the invention, a catheter that includes an expansion device that carries a plurality of the thermal sensors is described. The expansion device is arranged to position the thermal sensors against the walls of a vessel being mapped. In some embodiments, a protective sheath is provided to cover the thermal sensors such that the thermal sensors are positioned between the expansion device and the sheath/member. In a preferred embodiment, the expansion device takes the form of a balloon.
In some embodiments, the expansion device is combined with the infusion ports described above to facilitate localized drug delivery. In some specific implementations the expansion device (e.g. a balloon) is arranged to include a plurality of circumferential recesses in an expanded position in order to place therapeutic agents in physical contact with the vessel wall without being washed away by fluids passing through the vessel.
In some specific implementations, the infusion ports are coupled through a fluid delivery channel in the catheter to a reversible pump that facilitates infusing and/or removing fluids from the vessel. By way of example, these embodiments are particularly useful in applications where it is desirable to pump therapeutic agents (e.g. a radioactive fluid) into a vessel in the region of the thermal sensors and thereafter withdraw the therapeutic agents. Alternatively, separate infusion and withdrawal ports may be provided. In still other embodiments withdrawal ports alone may be provided. The withdrawal ports are particularly useful in applications where it is desirable to withdraw fluid samples (e.g. a blood sample) directly from the region of a vessel being thermally mapped.
In a method aspect of the invention aspect, methods are provided for withdrawing fluid specimens (e.g. blood) directly from in a vessel region of interest (e.g. adjacent vulnerable plaque). In some embodiments, a small vessel segment is isolated for a period of time prior to withdrawing the specimen to permit the infusion of serum markers from surrounding plaque and/or vessel walls. The sample is then taken from the isolated vessel segment.
In another particular method aspect of the invention, a method of treating vulnerable plaque is described. A thermal mapping catheter is inserted into an artery and used to detect the temperature of walls of the artery to identify a region of vulnerable plaque. A radioactive fluid is then applied to the identified region of vulnerable plaque using the catheter to facilitate treatment of the vulnerable plaque. In some embodiments, the radioactive fluid further includes a therapeutic agent. In some embodiments, the radioactive fluid is infused into the distal balloon catheter to deliver the radiation without coming into contact with the bodily fluid.
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W Casscells et al. “Thermal Detection of Cellular Infiltrates In Living Atherosclerotic Plaques: Possible Implications For Plaque Rupture And Thrombosi
Campbell Thomas H.
Rahdert David A.
Sweet William L.
Beyer Weaver & Thomas LLP
Farallon MedSystems, Inc.
Winakur Eric F.
Wingood Pamela L.
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