Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2001-05-31
2004-04-06
Jeffery, John A. (Department: 3742)
Surgery
Diagnostic testing
Cardiovascular
C600S342000
Reexamination Certificate
active
06716178
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of medical diagnosis and treatment by means of a device having Doppler velocimetry and thermal sensing capability. More specifically, the present invention relates to a therapeutic medical device for performing thermal measurements and laser Doppler velocimetry measurements within a body lumen.
2. Description of Related Art
Arteriosclerosis, or more specifically atherosclerosis, is a common human ailment arising from the deposition of fatty-like substances, referred to as atheroma or plaque, on the walls of systemic, peripheral, and coronary blood vessels. When deposits accumulate in localized regions of a vessel, blood flow can be occluded or restricted, increasing the risk of heart attack or stroke.
Numerous approaches for reducing and removing such vascular deposits have been proposed, including balloon angioplasty, where a balloon-tipped catheter is used to dilate a region of atheroma; atherectomy, where a blade or other cutting element is used to sever and remove the atheroma; laser angioplasty, where laser energy is used to ablate (i.e., remove) at least a portion of the atheroma; or stenting, where a stent is deployed (permanently or temporarily) at the site of vascular deposits (sometimes following balloon angioplasty). The vast majority of these therapeutic devices, however, are being used with very little information about the in vivo biological environment, including for example, the information on physiology, hemorheology, vascular biology or histology and histochemistry of the vasculature being treated. Without such information available to the physician, “lesion specific” treatment, as well as preventive measures, cannot be adequately envisioned or planned.
Evidence reported in the medical field suggests that thermal heterogeneity in the atherosclerotic plaque may reflect its propensity to be vulnerable to rupture. Both in vitro and in vivo data on human and animal lesions have indicated that thermal gradients in the tissue are related to the presence of inflammatory macrophages, and the most recent data have correlated thermal profiles with clinical presentation in humans. There is, therefore, scientific support that inflammation can be reflected in local thermal gradients in vascular tissue in vivo. Of particular interest is the application of thermal sensing to assess the risk of thrombotic complications post-intervention. An acute inflammatory response, such as that induced by endovascular percutaneous transluminal coronary angioplasty (PTCA) and/or stenting, may induce circulating monocyte binding and migration across the endothelium of the vessel wall to gain access to the injury site.
Studies have suggested that physiologic, and more specifically flow-based, components of the lesion environment can yield insight into lesion assessment and management. A variety of flow-based indices, most notably the coronary flow reserve (CFR), can be used to elucidate clinically relevant relations of physiologic lesion environment and the functional status of the treatment. A recent medical clinical trial concluded that based on target criteria established for residual percent diameter stenosis and final CFR, the percentage of acute procedural success observed in the trials could be increased up to 50 percent if some type of flow-based Doppler guidance were used.
Current generation medical devices force cardiovascular treatment procedures to employ one device for the diagnostic phase of the procedure and a second device for the treatment phase of the procedure. Given the tendency within the medical community to move toward shorter procedural times, spot PTCA, and even direct and/or spot stenting in many cases, the use of an additional device required to obtain diagnostic-type information is not generally an acceptable alternative.
Previous attempts to make a combined diagnostic/treatment biomedical device (such as a guidewire-based platform or a catheter-based system) with the capability of directly measuring flow-based variables have yielded devices either too bulky or too cumbersome to use during intravascular or intraluminal procedures. Current generation biomedical devices that have attempted to combine diagnostic and therapeutic capabilities consist mainly of ultrasound Doppler guidewires and ultrasound Doppler catheters.
Ultrasound Doppler guidewires have a number of disadvantages and limitations. One disadvantage is that the ultrasound Doppler guidewire measurement system creates a comparatively large sample volume (about 1 mm
3
). Another disadvantage associated with ultrasound Doppler guidewire devices is the susceptibility to signal loss very close to the lesion site. Furthermore, ultrasound Doppler guidewires require extensive operator input to optimize the signal quality in regions of disturbed flow.
Ultrasound Doppler catheter systems have disadvantages and limitations similar to those of ultrasound Doppler guidewire devices. The catheter-based ultrasound Doppler measurement system creates a comparatively large sample volume (about 1 mm
3
). Another disadvantage of current generation ultrasound Doppler catheter systems is the reduced catheter body flexibility due to the multiple junctions required in the design of these catheters. Another limitation of current ultrasound Doppler catheter designs is that because the ultrasonic crystals are mounted on either the side or end of the catheter body, instability of the catheter tip position can result, making it difficult to localize the measurement site.
Furthermore, most current ultrasound Doppler catheter and guidewire designs lack the means of having combined therapeutic/diagnostic capability, especially for intravascular or coronary applications. The result is that therapeutic strategies are often unilaterally rendered without relevant information concerning the lesion, surrounding vasculature, or the biomechanical environment—information which, if available, could be appropriately used to improve both acute and chronic outcomes for the patient.
The disadvantages of current generation ultrasound Doppler catheters and guidewires can be overcome in the present invention by incorporating thermal sensing and laser Doppler velocimetry (LDV) technologies onto a therapeutic catheter or therapeutic guidewire assembly. Laser Doppler velocimetry is a technique for measuring the speed of small particles. Generally, for LDV measurements, small particles suspended in a fluid are illuminated by a laser beam and the light scattered to various angles is compared to light in a reference beam to determine the Doppler shift of the scattered light. The Doppler shift of the light depends on the speed of the particles and the angle of measurement.
SUMMARY OF THE INVENTION
A therapeutic medical device for performing thermal and laser Doppler velocimetry measurements and method of using the same are described. In one embodiment, the therapeutic medical device includes an elongated member having at least first and second optical fibers longitudinally disposed therethrough, the first optical fiber to perform a laser Doppler velocity measurement of a fluid within a body lumen, the second optical fiber to perform a temperature measurement within the body lumen. Incorporating LDV technology and thermal sensing capability into a therapeutic medical device such as a catheter or a guidewire system provides diagnostic information of the physiologic environment of the lesion before, during, or after a therapeutic procedure.
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Ainsworth Robert D.
Ellis Jeffrey T.
Hurley Bridget A.
Kilpatrick Deborah
Lee Jeong S.
Advanced Cardiovascular Systems Inc.
Blakely , Sokoloff, Taylor & Zafman LLP
Jeffery John A.
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