This application is a continuation of co-pending U.S. application Ser. No. 13/025,959, filed on Feb. 11, 2011, which is a continuation of U.S. application Ser. No. 12/896,740, filed Oct. 1, 2010, which is a continuation of co-pending U.S. application Ser. No. 11/619,996, filed Jan. 4, 2007, which is a continuation of U.S. application Ser. No. 10/616,831, filed Jul. 10, 2003, which is a continuation of U.S. application Ser. No. 09/696,076, filed Oct. 25, 2000, now U.S. Pat. No. 6,656,136, which claims the benefit of U.S. provisional patent application, Ser. No. 60/163,466, filed Oct. 25, 1999, and U.S. provisional patent application, Ser. No. 60/171,703, filed Dec. 23, 1999.
FIELD OF THE INVENTION
The present invention generally relates to methods and apparatus for sealing vascular punctures and wounds, and more particularly, to a device that may be used to deliver ultrasound energy to a vascular puncture site to arrest bleeding.
BACKGROUND OF THE INVENTION
Various surgical procedures are performed by medical specialists such as cardiologists and radiologists, utilizing percutaneous entry into a blood vessel. To facilitate cardiovascular procedures, a small gauge needle is introduced through the skin and into a target blood vessel, often the femoral artery. The needle forms a puncture through the blood vessel wall at the distal end of a tract that extends through the overlying tissue. A guide wire is then introduced through the bore of the needle, and the needle is withdrawn over the guide wire. An introducer sheath is next advanced over the guide wire; the sheath and guide wire are left in place to provide access during subsequent procedure(s). The sheath facilitates passage of a variety of diagnostic and therapeutic instruments and devices into the vessel and its tributaries. Illustrative diagnostic procedures include angiography, intravascular ultrasonic imaging, and the like; exemplary interventional procedures include angioplasty, atherectomy, stent and graft placement, embolization, and the like. After this procedure is completed, the catheters, guide wire, and introducer sheath are removed, and it is necessary to close the vascular puncture to provide hemostasis and allow healing.
The most common technique for achieving hemostasis is to apply hard pressure on the patient's skin in the region of the tissue tract and vascular puncture to form a blood clot. Initially, pressure is applied manually and subsequently is maintained through the use of mechanical clamps and other pressure-applying devices. While effective in most cases, the application of external pressure to the patient's skin presents a number of disadvantages. When applied manually, the procedure is time-consuming and requires the presence of a medical professional for thirty minutes or more. For both manual and mechanical pressure application, the procedure is uncomfortable for the patient and frequently requires the administration of analgesics to be tolerable. Moreover, the application of excessive pressure can occlude the underlying artery, resulting in ischemia and/or thrombosis. Even after hemostasis has apparently been achieved, the patient must remain immobile and under observation for hours to prevent dislodgment of the clot and to assure that bleeding from the puncture wound does not resume. Renewed bleeding through the tissue tract is not uncommon and can result in hematoma, pseudoaneurisms, and arteriovenous fistulas. Such complications may require blood transfusion, surgical intervention, or other corrective procedures. The risk of these complications increases with the use of larger sheath sizes, which are frequently necessary in interventional procedures, and when the patient is anticoagulated with heparin or other drugs.
In recent years, several hemostasis techniques have been proposed to address the problem of sealing vessel wall punctures following percutaneous transcatheter procedures. Related prior art is described in U.S. Pat. Nos. 5,320,639; 5,370,660; 5,437,631; 5,591,205; 5,830,130; 5,868,778; 5,948,425; 6,017,359; and 6,090,130. In each of these patents, bioabsorbable, thrombogenic plugs comprising collagen and other materials are placed proximal to the vessel wall puncture site to stop bleeding. The large hemostasis plug stimulates blood coagulation in the vessel puncture site, but blocks the catheter entry tract, making catheter reentry more difficult, if required.
Other related prior art disclosed in U.S. Pat. Nos. 5,707,393; 5,810,884; 5,649,959; and 5,350,399 provides for the use of small dissolvable disks or anchors that are placed in the vessel to block or clamp the puncture hole. However, any device remaining in the vessel lumen increases the risk of thrombus formation. Such a device also can detach and cause occlusion in a distal blood vessel, which would likely require major surgery to remove.
Additional prior art includes U.S. Pat. Nos. 5,779,719; 5,496,332; 5,810,850; and 5,868,762. In the disclosure of these patents, needles and sutures delivered through catheters are used to ligate the puncture. The suturing procedure requires particular skill. Suture material left in the vessel may cause tissue irritation that will prolong the healing process.
Still other prior art is disclosed in U.S. Pat. No. 5,626,601, wherein a procoagulant is injected into the puncture, with a balloon catheter blocking inside the vessel lumen. However, in some cases, the clotting agent may leak past the balloon into the vessel lumen and cause stenosis.
Yet other prior art references related to this topic include U.S. Pat. Nos. 4,929,246; 5,810,810; and 5,415,657, which disclose the use of a laser or of radio-frequency (RF) energy that is transmitted to the blood vessel through a catheter to thermally fuse or weld the punctured tissue together.
All of the above cited prior art references require either introducing and leaving foreign objects in the patient's body, and/or inserting a tubular probe of large diameter into the tissue channel left by the catheter in order to seal the puncture.
As will be evident from the preceding discussion, there is a clear need for an improved method and apparatus for sealing a puncture left in a blood vessel, following an intravascular catheterization procedure. The method and apparatus should cause rapid cessation of bleeding, not rely on blood clot formation, and should be independent of the patient's coagulation status. By employing such a method and apparatus, the patient will be more comfortable as a result of shortened hemostasis and ambulation times, and physician and hospital resources will thereby be minimized. In addition, the method and apparatus should not leave any foreign object in the patient's body, to reduce the risk of stenosis at or distal to the puncture wound. An ideal device will be noninvasive and should not include any component that must be inserted in the catheter tract and which might further damage the wound and impede the sealing process.
SUMMARY OF THE INVENTION
In accord with the present invention, a method and apparatus are defined that provide advantageous solutions to the problem of expeditiously and safely sealing vascular catheter entry wounds made in connection with medical procedures. The method includes the steps of determining a site of the puncture in the vascular vessel and positioning an ultrasonic transducer applicator at a position adjacent to the site. The ultrasonic transducer applicator is coupled to a control that includes a processor programmed to administer ultrasonic energy in a manner that efficaciously seals a puncture. A user is enabled to initiate a process that is controlled by the control, so that very little operator training is required. The control automatically controls the ultrasonic transducer applicator so that the ultrasonic energy produced by the ultrasonic transducer applicator is focused at the site and is administered at a sufficient intensity and duration to denature tissue at the puncture, closing and sealing the puncture.
To determine the site of the puncture, an imaging ultrasonic beam is generated with the ultrasonic transducer applicator and is transmitted into the patient, proximate an expected location for the site. A reflection of the imaging ultrasonic beam is then received from within the patient using the ultrasonic transducer applicator, producing a corresponding output signal. The output signal is processed with the processor included in the control to facilitate determining the site of the puncture.
For example, a visual indication of a location of the site of the puncture can be provided to enable an operator to position the ultrasonic transducer applicator so that the ultrasonic energy produced by the ultrasonic transducer applicator is directed at the site. Such a visual indication may be in the form of, for example, lighted display indicators. In one form of the present invention, the visual indication includes an image of the site in which an axis of the vascular vessel is visually evident, enabling the operator to position the ultrasonic transducer applicator longitudinally along the axis of the vascular vessel so that the ultrasonic energy is directed at the site of the puncture.
In an alternative embodiment, an object is provided that extends into the puncture from outside the patient. The operator can then estimate the location of the puncture along the longitudinal axis of the vessel based upon a disposition of the object extending outside the patient. As yet a further alternative, the visual indication includes an image of the site in which the object extending into the puncture is evident. An estimate is made of the location of the puncture based upon a disposition of the object in the image.
Finally, the output signal can be processed with the processor to determine the site of the puncture. An indicator disposed on the ultrasonic transducer applicator can be controlled by the processor to provide an indication of a direction in which the ultrasonic transducer applicator should be moved to position it adjacent to the site of the puncture.
The processor is preferably used for automatically controlling at least one of a direction, an intensity, and a focus of the ultrasonic energy, to ensure that the ultrasonic energy is administered to the site of the puncture. Using the processor, the ultrasonic energy is directed so as to overscan the site of the puncture, ensuring that the puncture is closed and sealed. For example, the processor can move the focus of the ultrasonic energy while it is being administered, to overscan the site of the puncture. As another alternative, an ultrasound emitter of the ultrasonic transducer applicator has an aspheric shape so that the ultrasonic energy that is directed at the site of the puncture covers a larger area that overscans the site. Other transducer configurations that provide a laterally broadened focal region may also be employed.
Preferably, the ultrasonic transducer applicator uses a common array of transducers for generating both the imaging ultrasound beam and the ultrasound energy that closes and seals the puncture.
It is also contemplated that the administration of the ultrasonic energy be interrupted, to again generate the imaging ultrasound beam, thereby confirming whether the ultrasonic energy is being directed at the site of the puncture.
The processor is preferably employed to control a force applied against a surface of the patient using a force generator included in the ultrasonic transducer applicator. This force is controlled so that a pressure developed by the force is sufficient to substantially stop fluid leakage from the vascular vessel, but not so great as to substantially occlude fluid flow through the vascular vessel.
Another aspect of the invention is directed to enclosing the unit applicator within a protective, acoustic coupling shell. The protective, acoustic coupling shell is adapted to contact an external dermal portion of the patient in order to convey the ultrasonic energy transdermally to the site of the puncture, while isolating an ultrasonic emitter surface on the ultrasonic transducer from direct, contacting exposure to the patient. The protective, acoustic coupling shell is preferably pre-sterilized and preferably includes a gel patch on an outer surface that is protected by a tab. The tab is removed prior to contacting the external dermal surface of the patient.
Still another aspect of the present invention is directed to apparatus. The apparatus include elements that carry out functions generally consistent with the steps of the method discussed above.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a schematic block diagram of the primary components employed in a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating how the present invention is employed for sealing a puncture in a vessel;
FIG. 3 schematically illustrates a collagen seal produced by the present invention to close the puncture in the vessel of FIG. 2;
FIG. 4 is a flow chart illustrating the logical steps followed during sealing of a vascular wound in accord with the present invention;
FIG. 4A is a flow chart illustrating the optional steps employed for detecting nerves during the method of FIG. 4;
FIG. 5 is a cross-sectional view of a portion of a patient's body, illustrating an applicator unit in accord with the present invention disposed adjacent to a puncture that extends transdermally into an artery;
FIG. 6 is a cutaway isometric view of the applicator shown in FIG. 5;
FIG. 6A is an isometric view showing the force sensing transducer, force generator, and ultrasonic array of the applicator;
FIG. 7 is an elevational view of a locator rod adapted to be inserted into a puncture wound over a guide wire;
FIG. 7A is a cross-sectional view of a portion of a patient's body like that in FIG. 5, illustrating the locator rod of FIG. 7 being used to determine a location of a puncture in the artery relative to the applicator unit;
FIG. 7B is similar to FIG. 7A, but illustrates the use of ultrasonic pulse-echo techniques to determine the spatial location of the locator rod;
FIG. 7C depicts a view of a framed two-dimensional image a target region generally orthogonal to that shown in FIG. 7A and FIG. 7B, for use in locating the puncture site;
FIG. 8 is a schematic isometric view of an embodiment of the applicator that uses a disposable shell;
FIG. 8A is an side view of the disposable shell of FIG. 8;
FIG. 9 is a schematic system block diagram depicting modules included in the applicator and control unit;
FIGS. 10 and 10A respectively illustrate the ultrasound beam orientation relative to the vessel from the side of the vessel and as viewed along the vessel;
FIG. 11 is a plan view of an embodiment of the applicator illustrating the controls and indicators that it includes;
FIGS. 12A and 12B respectively illustrate the side and longitudinal geometry of the therapeutic ultrasound beam; and
FIG. 13 is an isometric view illustrating the ultrasound beam geometry produced by an aspheric transducer.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Use of Ultrasound for Sealing Punctures
Because of its unique properties in soft tissue, ultrasound can be brought to a tight focus at a distance from its source. If sufficient energy is radiated within the ultrasound beam, cells located in the focal volume can be rapidly heated, while intervening and surrounding tissues are spared. Surrounding tissues are unaffected in the unfocused portion of the ultrasound beam because the energy is spread over a correspondingly larger area and associated heating is minimized.
Whereas ultrasound intensities on the order of 0.1 Watts/cm2 are employed in diagnostic imaging applications, intensities in excess of 1,000 Watts/cm2 are typical in high-intensity focused ultrasound (HIFU) applications. At the focal point, these high intensities result in large, controlled temperature rises within a matter of seconds.
It has been demonstrated in numerous in vivo animal studies that HIFU can rapidly seal blood vessel punctures and lacerations over a wide range of sizes. When accurately targeted on a vascular wound, ultrasound has been shown to induce complete hemostasis in less than one minute in the femoral, carotid, and axillary arteries, and in the femoral and jugular veins of large animals, while blood flow through the treated vessels remained unaffected. These investigations included: (a) sealing punctured, surgically exposed vessels using visual targeting, (b) sealing incised, surgically exposed vessels using visual targeting, (c) sealing surgically exposed, punctured vessels using Doppler-guided ultrasound targeting, and (d) noninvasive sealing of punctured vessels under ultrasound imaging guidance wherein complete hemostasis was noted in 13±12 seconds.
The mechanism of hemostasis in these ultrasound-exposed vascular wounds appears thermal in origin and involves denaturization of native perivascular collagen with subsequent formation of an extensive fibrin network that covers the hole, thereby sealing it closed. The fibrin links with adjacent vessel wall tissues to form a seal that has been shown to be independent of puncture hole size. Acoustic streaming forces generated by the HIFU beam were also observed to play a role in opposing the escape of blood from the vascular wound. Blood clotting is not believed to be a factor in achieving acoustic hemostasis, as evidenced by equally rapid and complete wound sealing in highly anticoagulated animals and in ex vivo vessels in which saline has been substituted for blood.
Overview of the Present Invention
FIGS. 1 and 2 show the main components of an ultrasonic system suitable for use in implementing the present invention. As illustrated in FIG. 1, a hand-held applicator unit 2 is positioned over an arterial wound 8 in the patient. Included with the hand-held applicator unit is a generally single-use, pre-sterilized cover and acoustic coupling shell 4 that slips over applicator 2. A control unit 6 implements algorithms to facilitate the method and is coupled to applicator 2.
The user enters various conventional scan and control parameters into an input unit 70, which typically includes user input devices 72. Examples of such devices include a keyboard, knobs, and buttons. The input unit is connected to a processing system 74, which will typically comprise a plurality of microprocessors and/or digital signal processors. Processing system 74 may, however, also be implemented using a single processor of sufficient speed to handle the various tasks described below. A conventional memory 75 will normally be included in the system to store, among other data, transmission control parameters and imaging data generated in any given implementation of the present invention.
Processing system 74 sets, adjusts, and monitors the operating parameters of a conventional transmission and control circuit 76. Control circuit 76 forms a transmit ultrasonic waveform by generating and applying electrical control and driving signals to an ultrasound transducer 78, which preferably comprises an array of individually controllable piezoelectric elements. As is well known in the art, the piezoelectric elements generate ultrasonic waves when electric, signals of a proper frequency are applied to them; conversely, when receiving reflected ultrasonic waves, they generate electrical signals corresponding to the mechanical vibrations caused by the returning ultrasonic waves.
Transducer 78 is positioned against it portion 82 of the body of a patient, and by varying the phasing, amplitude, and timing of the driving signals for the transducer array elements, ultrasonic waves are focused to form a transmit beam 314 of high-intensity ultrasound.
In FIG. 2, open arrows indicate the direction of a flow of blood within a blood vessel 312, which has a puncture site 316 that may have been caused by introduction of a catheter or, in the case of unintended punctures that have produced wounds, by some other object. The tissue forming a layer 318 of collagen found on the surface of blood vessels is also shown in FIG. 2 surrounding blood vessel 312.
As will be clear from the description of the present invention below, it is not necessary for the system to include an imaging capability. However, the provision of an imaging capability, including pulse-echo lines of interrogation that are not displayed as images, in the present invention should assist a user to more accurately locate a vascular puncture site. It is recognized that a full display of the insonified vascular target site is not required.
Nonetheless, since imaging of a vascular target site is preferable and will employ echo processing (especially, Doppler), FIG. 2 also illustrates a reception controller 88, which will include conventional amplification and signal conditioning circuitry as needed. Reception controller 88, all or part of which is normally integrated into processing system 74, converts the ultrasonic echo signals (which are typically at radio frequencies, on the order of a few to tens of megahertz) into lower frequency ranges for processing and may also include analog-to-digital conversion circuitry. The processing includes, as needed, such known signal conditioning as time-gating, gain compensation, Doppler frequency shift processing, and diffraction compensation, in order to identify echo signals from any selected focal region. The type of conventional signal processing needed (if any) will in general depend on the particular implementation of the present invention employed and can be implemented using known design methods.
Note that it is not essential, according to the present invention, that the transducer 78 be used externally, relative to the patient\'s body. It is also contemplated that the transducer may be maneuvered inside a patient\'s body, and the beam focused on a puncture from inside the body. For example, a transesophageal probe, laparoscopic, or other probe inserted into a body cavity, such as the vagina or rectum can be used to practice the present invention. A suitably designed probe inserted into an open body cavity or via minimally invasive means could be used to arrest bleeding in surgical or trauma care situations. Yet, most of the following discussion is directed to a preferred embodiment of the present invention in which the transducer is intended to be used externally, since an initial commercial product in accord with the present invention will be designed for such use.
A conventional display system 92 may also be included in order to display information concerning transmission power, time, focus data, etc. The display system will include known circuitry for scan conversion and for driving the display, as needed. These circuits are well known and therefore need not be specifically illustrated or described further to provide an enabling disclosure.
FIG. 3 illustrates the result of an insonification of puncture site 316 using the present invention. As the focal point of transmit beam 314 (see FIG. 2) is moved around (as illustrated by the arrows pointing in either direction from the focus of the beam) the area of puncture site 316 using conventional beam-steering techniques, the tissue adjacent the puncture site 316 will denature. In effect, the collagen in the tissue “melts” and flows over and into the puncture opening. When the collagen cools, it forms a “patch” that not only covers the puncture, but also flows partially into the puncture opening in the wall of the blood vessel. Moreover, since the denatured tissue tends to contract, it also tends to pull the edges of the puncture together and thus further close the wound.
It should be noted that the present invention can be employed to seal vascular wounds of various types and is not limited to the type of wound created as a result of interventional procedures in which a catheter has been introduced into a vascular vessel. As noted above, application of thermal treatment to the tissue overlying a wound has been demonstrated to seal the wound. In the present invention, a practical method has been developed for repeatedly and reliably achieving sealing of the puncture in a vascular vessel. Steps carried out in this method are shown in FIG. 4, which is discussed below. These steps represent one preferred embodiment of the present invention, but do not represent all alternatives that might be employed to achieve acceptable sealing.
Key steps in the method for vascular sealing described here include:
1. Positioning an ultrasound generating source on a patient such that the source is targeted at an area including the wound to be sealed;
2. Applying a pressure against the patient in an area overlying the wound and directed substantially toward the vessel to be treated;
3. While the pressure and the positioning of the ultrasound source are maintained, carrying out an insonification of a volume of tissue that includes the wound, using an ultrasound exposure that delivers an acoustic energy density (measured at the approximate location of the wound), in excess of 100 joules/sq. cm, but generally less than several thousand joules/sq. cm.
Additional steps of the method described below employ the apparatus in an automated manner that facilitates ease of use and ensures the safety and consistency of the results obtained.
A clinically acceptable device for sealing a puncture wound in accord with the present invention must meet a number of requirements, including:
1. The device and associated procedure must be safe to use in that they avoid undesirable bioeffects, so that the patient is not injured directly or indirectly as a result of the procedure; also, in the event that effective vessel sealing does not occur as desired, traditional methods of applying pressure to the wound are sufficient to accomplish hemostasis;
2. The device and associated procedure must be easy to use in an efficient manner, to facilitate proper, repeatable execution of the sealing process; requirements for operator training should be minimized;
3. The sealing process must be sufficiently fast to enable the entire procedure to be rapidly completed—preferably, in less than 5 minutes;
4. The cost per sealing procedure should be minimized; and,
5. The efficacy of the device should be very high, generally achieving a success rate in excess of about 95%; acceptability of the present invention in routine clinical practice does not permit an unpredictable outcome.