System for detecting catheter electrodes entering into and exiting from an introducer

Systems for detecting when catheter electrodes enter and exit an introducer are disclosed. In one form, a system detects a relative position of a catheter (comprising a marker band and an electrode) and an introducer (comprising a proximity sensor adapted to sense the marker band), while the catheter and introducer are in a human body. The system may comprise an electronic control unit to analyze signals from the catheter and/or the introducer, to determine whether the catheter electrode is within the introducer; and to disregard data collected from the electrode when that electrode is in the introducer. The sensor may be on the catheter and the sensed element may be on the introducer. The sensed element may comprise one or several marker bands. A marker band may be applied during the manufacture of a medical device or during its use and is any element capable of electromagnetic detection.

BACKGROUND OF THE INVENTION

a. Field of the Invention

This invention relates to systems, apparatuses and methods for navigating a medical device within a body. In particular, the instant invention relates to systems, apparatuses and methods for detecting when one or more electrodes on a medical device enter into and/or exit from an introducer or other enveloping device while navigating the medical device within a body.

b. Background Art

Electrophysiology catheters are used in a variety of diagnostic, therapeutic, and/or mapping and ablative procedures to diagnose and/or correct conditions such as atrial arrhythmias, including for example, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter. Arrhythmias can create a variety of conditions including irregular heart rates, loss of synchronous atrioventricular contractions and stasis of blood flow in a chamber of a heart which can lead to a variety of symptomatic and asymptomatic ailments and even death.

Typically, a catheter is deployed and manipulated through a patient's vasculature to the intended site, for example, a site within a patient's heart. The catheter carries one or more electrodes that can be used for cardiac mapping or diagnosis, ablation and/or other therapy delivery modes, or both, for example. Once at the intended site, treatment can include, for example, radio frequency (RF) ablation, cryoablation, laser ablation, chemical ablation, high-intensity focused ultrasound-based ablation, microwave ablation, and/or other ablation treatments. The catheter imparts ablative energy to cardiac tissue to create one or more lesions in the cardiac tissue. This lesion disrupts undesirable cardiac activation pathways and thereby limits, corrals, or prevents errant conduction signals that can form the basis for arrhythmias.

To position a catheter at a desired site within the body, some type of navigation may be used, such as using mechanical steering features incorporated into the catheter (or an introducer). In some examples, medical personnel may manually manipulate and/or operate the catheter using the mechanical steering features.

In order to facilitate the advancement of catheters through a patient's vasculature, a navigating system may be used. Such navigating systems may include, for example, electric-field-based positioning and navigating systems that are able to determine the position and orientation of the catheter (and similar devices) within the body. In such electric-field-based positioning and navigating systems, it can be important to know when the electrodes on the catheter are shielded inside of a sheath or introducer that is being used to deliver the catheter to a desired location.

The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope.

BRIEF SUMMARY OF THE INVENTION

The present disclosure generally relates to detecting when catheter electrodes enter into, and/or exit from, an introducer or other enveloping device in order to avoid, for example, introducing undesirable shift or drift into the determined catheter position and orientation based upon readings obtained by an electric-field-based positioning system.

In an embodiment, a system detects a relative position of a catheter and an introducer while the catheter and the introducer are in a human body, wherein the catheter comprises a marker band and an electrode and the introducer comprises a proximity sensor adapted to sense the marker band. The system comprising (a) an electric-field-based positioning system; and (b) an electronic control unit electrically coupled to the electric-field-based positioning system. The electronic control unit is operable to do the following: (A) drive currents through a plurality of patch electrodes on a surface of the body and measure a resulting voltage from the catheter electrode; (B) monitor a first signal originating from the proximity sensor to determine when the marker band pass the proximity sensor; (C) analyze the first signal to determine whether the catheter electrode is within the introducer; and (D) disregard the measured resulting voltage if the catheter electrode is within the introducer. In some embodiments, when the system disregards measured resulting voltage data, it also communicates that fact to a clinician (e.g., by sending a message to a display or activating a light on the catheter or the introducer.

In another embodiment, a system detects when a sensed element on a first medical device enter into or exist from an introducer, and the system comprises the following: (a) a first storage operable to store (i) first location data relating to a location of the sensed element on the first medical device and (ii) second location data relating to a location of a sensor on the introducer; (b) a second storage operable to store current position and orientation data relating to the first medical device; (c) a device operable to determine a relative position of the sensor and the sensed element based upon the stored first and second location data; and (d) a processor in communication with the first storage, the second storage, and the device. Further, in this embodiment, the processor is operable to do the following: (1) consider the relative position of the sensor and the sensed element; (2) determine whether to disregard the current position and orientation data for the first medical device; and (3) output a signal indicative of whether the current position and orientation data for the first medical device is being disregarded.

In yet another embodiment, a system detects when one or more catheter electrodes enter into or exist from an introducer, and the system comprises the following: (a) an introducer comprising (i) an introducer proximal end, (ii) an introducer distal end, (iii) a longitudinally-extending introducer body extending between the introducer proximal end and the introducer distal end; and (iv) a first element affixed to the introducer body; and (b) a catheter comprising (i) a catheter proximal end, (ii) a catheter distal end, (iii) a longitudinally-extending catheter body extending between the catheter proximal end and the catheter distal end; (iv) a plurality of electrodes on the catheter body; and (v) a second element affixed to the catheter body and operable to electromagnetically interact with the first element. In one offshoot of this embodiment, the first element is a proximity sensor and the second element is a marker band on an outer surface of the catheter body. And, in another embodiment, the catheter comprising part of the system may further comprise an indicator light configured to report when at least one of the plurality of catheter electrodes is located within the introducer.

In another embodiment, a catheter is provided that includes a shaft having one or more electrodes at a distal portion of the shaft, and includes a detectable marker positioned proximal to the one or more electrodes at the distal portion of the shaft. The detectable marker is positioned at a predetermined distance from a most proximal one of the one or more electrodes. In a more particular embodiment of such a catheter, the predetermined distance may correspond to a distance from a distal opening of an interoperable introducer to a marker detector positioned along the introducer proximal to the distal opening. In still another particular embodiment of such a catheter, one or more additional detectable markers may each be positioned proximal to a plurality of the electrodes at the distal portion of the shaft, where each of the detectable markers is positioned a predetermined distance from a respective one of the plurality the electrodes.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures, in which like reference numerals refer to the same or similar features in the various views,FIG. 1illustrates one embodiment of a system10for navigating a medical device within a body12. In the illustrated embodiment, the medical device comprises a catheter14that is shown schematically entering a heart that has been exploded away from the body12. The catheter14, in this embodiment, is depicted as an irrigated radiofrequency (RF) ablation catheter for use in the treatment of cardiac tissue16in the body12. It should be understood, however, that the system10may find application in connection with a wide variety of medical devices used within the body12for diagnosis or treatment. For example, the system10may be used to navigate an electrophysiological mapping catheter, an intracardiac echocardiography (ICE) catheter, or an ablation catheter using a different type of ablation energy (e.g., cryoablation, ultrasound, etc.). Further, it should be understood that the system10may be used to navigate medical devices used in the diagnosis or treatment of portions of the body12other than cardiac tissue16.

Referring still toFIG. 1, the ablation catheter14is connected to a fluid source18for delivering a biocompatible irrigation fluid such as saline through a pump20, which may comprise, for example, a fixed rate roller pump or variable volume syringe pump with a gravity feed supply from fluid source18as shown. The catheter14is also electrically connected to an ablation generator22for delivery of RF energy. The catheter14may include a handle24; a cable connector or interface26at a proximal end of the handle24; and a shaft28having a proximal end30, a distal end32, and one or more electrodes34. The connector26provides mechanical, fluid, and electrical connections for conduits or cables extending from the pump20and the ablation generator22. The catheter14may also include other conventional components not illustrated herein such as a temperature sensor, additional electrodes, and corresponding conductors or leads.

The handle24provides a location for the physician to hold the catheter14and may further provide means for steering or guiding the shaft28within the body12. For example, the handle24may include means to change the length of one or more pull wires extending through the catheter14from the handle24to the distal end32of shaft28. The construction of the handle24may vary.

The shaft28may be made from conventional materials such as polyurethane and may define one or more lumens configured to house and/or transport electrical conductors, fluids, or surgical tools. The shaft28may be introduced into a blood vessel or other structure within the body12through a conventional introducer (see, for example,FIGS. 2 and 3). The shaft28may then be steered or guided through the body12to a desired location such as the tissue16using guide wires or pull wires or other means known in the art including remote control guidance systems. The shaft28may also permit transport, delivery, and/or removal of fluids (including irrigation fluids and bodily fluids), medicines, and/or surgical tools or instruments.

The system10may include an electric-field-based positioning system36, a magnetic-field-based positioning system38, a display40, and an electronic control unit (ECU)42. Each of the exemplary system components is described further below.

The electric-field-based positioning system36is provided to determine the position and orientation of the catheter14and similar devices within the body12. The system36may comprise, for example, the ENSITE NAVX system sold by St. Jude Medical, Inc. of St. Paul, Minn., and described in, for example, U.S. Pat. No. 7,263,397 titled “Method and Apparatus for Catheter Navigation and Location Mapping in the Heart,” the entire disclosure of which is hereby incorporated by reference as though fully set forth herein. The system36operates based upon the principle that when low amplitude electrical signals are passed through the thorax, the body12acts as a voltage divider (or potentiometer or rheostat) such that the electrical potential or field strength measured at one or more electrodes34on the catheter14may be used to determine the position of the electrodes, and, therefore, of the catheter14, relative to a pair of external patch electrodes using Ohm's law and the relative location of a reference electrode (e.g., in the coronary sinus).

In the configuration shown inFIG. 1, the electric-field-based positioning system36further includes three pairs of patch electrodes44, which are provided to generate electrical signals used in determining the position of the catheter14within a three-dimensional coordinate system46. The electrodes44may also be used to generate EP data regarding the tissue16. To create axes-specific electric fields within body12, the patch electrodes are placed on opposed surfaces of the body12(e.g., chest and back, left and right sides of the thorax, and neck and leg) and form generally orthogonal x, y, and z axes. A reference electrode/patch (not shown) is typically placed near the stomach and provides a reference value and acts as the origin of the coordinate system46for the navigation system.

In accordance with this exemplary system36as depicted inFIG. 1, the patch electrodes include right side patch44X1, left side patch44X2, neck patch44Y1, leg patch44Y2, chest patch44Z1, and back patch44Z2; and each patch electrode is connected to a switch48(e.g., a multiplex switch) and a signal generator50. The patch electrodes44X1,44X2are placed along a first (x) axis; the patch electrodes44Y1,44Y2are placed along a second (y) axis, and the patch electrodes44Z1,44Z2are placed along a third (z) axis. Sinusoidal currents are driven through each pair of patch electrodes, and voltage measurements for one or more position sensors (e.g., ring electrodes34or a tip electrode located near the distal end32of catheter shaft28) associated with the catheter14are obtained. The measured voltages are a function of the distance of the position sensors from the patch electrodes. The measured voltages are compared to the potential at the reference electrode and a position of the position sensors within the coordinate system46of the navigation system is determined.

The magnetic-field-based positioning system38in this exemplary embodiment employs magnetic fields to detect the position and orientation of the catheter14within the body12. The system38may include the GMPS system made available by MediGuide, Ltd. and generally shown and described in, for example, U.S. Pat. No. 7,386,339 titled “Medical Imaging and Navigation System,” the entire disclosure of which is hereby incorporated by reference as though fully set forth herein. In such a system, a magnetic field generator52may be employed having three orthogonally arranged coils (not shown) to create a magnetic field within the body12and to control the strength, orientation, and frequency of the field. The magnetic field generator52may be located above or below the patient (e.g., under a patient table) or in another appropriate location. Magnetic fields are generated by the coils and current or voltage measurements for one or more position sensors (not shown) associated with the catheter14are obtained. The measured currents or voltages are proportional to the distance of the sensors from the coils, thereby allowing determination of a position of the sensors within a coordinate system54of system38.

The display40is provided to convey information to a physician to assist in diagnosis and treatment. The display40may comprise one or more conventional computer monitors or other display devices. The display40may present a graphical user interface (GUI) to the physician. The GUI may include a variety of information including, for example, an image of the geometry of the tissue16, electrophysiology data associated with the tissue16, graphs illustrating voltage levels over time for various electrodes34, and images of the catheter14and other medical devices and related information indicative of the position of the catheter14and other devices relative to the tissue16.

The ECU42provides a means for controlling the operation of various components of the system10, including the catheter14, the ablation generator22, and the switch48of the electric-field-based positioning system36, and magnetic generator52of the magnetic-field-based positioning system38. For example, the ECU42may be configured through appropriate software to provide control signals to switch48and thereby sequentially couple pairs of patch electrodes44to the signal generator50. Excitation of each pair of electrodes44generates an electromagnetic field within the body12and within an area of interest such as the heart. The ECU42may also provide a means for determining the geometry of the tissue16, electrophysiology characteristics of the tissue16, and the position and orientation of the catheter14relative to tissue16and the body12. The ECU42also provides a means for generating display signals used to control the display40. The depicted ECU42represents any processing arrangement such as, for example, single device processors, multiple device processors (e.g., co-processors, master/slave processors, etc.), distributed processing across multiple components/systems, system on chip (SOC) devices, or the like.

As the catheter14moves within the body12, and within the electric field generated by the electric-field-based positioning system36, the voltage readings from the electrodes34change, thereby indicating the location of catheter14within the electric field and within the coordinate system46established by the system36. The ring electrodes34communicate position signals to ECU42through a conventional interface (not shown). In order to avoid introducing undesirable shift or drift into the determined catheter position and orientation based upon readings obtained by the electric-field based positioning system36, it can be important to know when the catheter electrodes34are inside the introducer. In particular, if the catheter electrodes34are located inside the introducer, the data coming off of those shielded electrodes may be degraded/compromised.

FIG. 2depicts a steerable introducer56having a sensor58(e.g., a proximity sensor) affixed to a cap60of a hemostasis valve62. Although the proximity sensor58is depicted as an external component, it could be internal to the handle64. Also visible inFIG. 2is a Tuohy-Borst side arm assembly66, including a Tuohy-Borst adapter68and a stopcock70. A steering actuator72is shown at the distal end of the handle64, and a strain relief74(or retaining nut) is shown just distal to the steering actuator72. An introducer shaft76extends rightward inFIG. 2from the strain relief74to an atraumatic tip78at the distal end of the shaft. An electrode80is also depicted inFIG. 2near the atraumatic tip78. A connector82is available to electrically connect the sensor58to, for example, the ECU42(FIG. 1). Finally, the steerable introducer56depicted inFIG. 2may include on-board information storage84(e.g., an EEPROM or other memory device) mounted inside the handle housing. The introducer depicted inFIG. 2is similar to the AGILIS ES steerable introducer manufactured by St. Jude Medical, Inc., of St. Paul. Minn., and is depicted as a representative example of an introducer or other enveloping device in which the principles described herein may be implemented.

FIG. 3depicts a fixed-curve introducer86. The fixed-curve introducer has a hemostasis valve62′ at its proximal end. The hemostasis valve includes a cap60′ that includes an annular groove88that is configured to accept the gripping arms90of a clip-on sensor92such as the one depicted in, for example,FIG. 4. The clip-on sensor depicted inFIG. 4includes a sensor head94and a mounting clip96comprising the gripping arms90shown riding in the annular groove88in the hemostasis valve cap60′ ofFIG. 3. An electrical connector is depicted inFIG. 3for electrically connecting the sensor92to a navigation system10such as the one depicted inFIG. 1. The fixed-curve introducer, as shown inFIG. 3, also includes a Tuohy-Borst side arm assembly66, including a Tuohy-Borst adapter68and a stopcock70. The fixed-curve introducer depicted inFIG. 3is similar to a SWARTZ BRAIDED introducer sold by St. Jude Medical, Inc., and is depicted as another representative example of an introducer or other enveloping device in which the principles described herein may be implemented. An atraumatic tip78′ is depicted at the distal end of the introducer shaft76′. The clip-on sensor92is a separate, re-sterilizable device that could be attached to the proximal end of the introducer86.

FIG. 5depicts a catheter14′ having a plurality of electrodes34for a variety of diagnostic and therapeutic purposes including, for example, electrophysiological studies, catheter identification and location, pacing, and cardiac mapping and ablation. Although the catheter14′, for purposes of this invention, could be a therapy or diagnostic catheter, the catheter depicted inFIG. 5is most similar to the SAFIRE ablation catheter manufactured by St. Jude Medical, Inc., and is depicted as a representative example of a catheter or other advanceable intrabody device in which the principles described herein may be implemented.

InFIG. 5, a marker band98is shown near the proximal end of the catheter shaft28′. The marker band could extend around the entire circumference of the catheter shaft, or it could be one or more arcuate pieces rather than a complete ring. The marker band98could also be an embedded spot or puck or other recessed, detectable component (e.g., lines or tick marks like the transverse markings on a tape measure). The marker band98could be molded into or applied to the surface of the catheter shaft28′; and, the marker band could be added to the catheter shaft during assembly of the catheter, or it could be added at a later time, including just prior to a procedure in an electrophysiology (EP) lab. The application of marker bands on catheter shafts, “on the fly” in an EP lab is discussed further below in connection withFIGS. 21 and 22.

Preferably, the marker band or bands98on the catheter shaft are flush or nearly flush with the outer surface of the catheter shaft28′ so that they may fit through the seal in the hemostasis valve (62or62′ or62″) of the steerable or fixed-curve introducer56,86, respectively. However, an enlarged marker band (not shown) that does not fit through the hemostasis valve could be used if the physician or clinician only wanted to know when the most proximal ring electrode exits the distal end of the introducer. At that point, the enlarged marker band could actually come into physical contact with the proximal side of the hemostasis valve and, alternatively, be simultaneously sensed by the sensor58and reported to the navigation system10. Similar to what was described in connection with the introducer shown inFIG. 2, the catheter depicted inFIG. 5may also include on-board storage84′ such as an EEPROM, shown inFIG. 5as being mounted within the catheter handle housing. The EEPROM could store, for example, information about the location of the marker band, including the distance from the marker band to the tip electrode along the catheter shaft, and/or the distance from the marker band to the most-proximal ring electrode, and/or the distance from the marker band to each of a plurality of ring electrodes on the catheter shaft. When the catheter is connected via the electrical connector26to the navigation system depicted inFIG. 1, the navigation system could thereby learn about the marker band and its placement along the catheter shaft. Finally, a light100(e.g., an LED) may be present on the catheter handle24′ as explained further below.

FIG. 6depicts a catheter assembly102, comprising the catheter14′ shown inFIG. 5inserted into the steerable introducer56shown inFIG. 2. When the catheter shaft28′ is inserted down the throat of the introducer as shown inFIG. 6, the distal end of the catheter shaft protrudes from the sheath distal end. In this particular embodiment, when the most proximal catheter electrode exits the distal end of the sheath, a marker band is detected by the proximity sensor58, and the indicator light100lights up. Alternatively, the indicator light100could be red until the marker band98is detected by the proximity sensor and then go out or turn green. Other feedback may be used in lieu of or in addition to visual feedback, such as audible, tactile (e.g., vibratory) and/or other perceivable feedback. The fact that the most proximal catheter electrode has exited from the distal end of the introducer shaft76may also be reported through the connector82to the navigation system10depicted inFIG. 1. The navigation system relies upon knowing that the ring electrodes and tip electrode34are not within the introducer shaft76. If one or more of the ring electrodes, for example, are retracted into the introducer shaft76, the navigation system receives degraded or compromised data and may miscalculate or be completely unable to determine where the catheter is located within, for example, an anatomical model of the patient's heart.

FIG. 7is an enlarged view of the circled region ofFIG. 6, depicting a most-proximal catheter electrode104adjacent to the distal end106of the introducer shaft76.

FIGS. 8 and 9schematically depict the steerable introducer56and catheter14′ shown in, for example,FIG. 6. As shown inFIG. 8, the marker band98on the catheter14′ is detected by the proximity sensor58on the introducer56as the most-proximal ring electrode104exits from the distal end of the introducer106. The compatibility of a given introducer with a given catheter is determined by ensuring that the distance from the proximity sensor58to the distal end106of the introducer56is the same as the distance from the marker band98to the most-proximal ring electrode104of the catheter14′. These two distances are both represented as ‘D’ inFIGS. 8 and 9. InFIG. 9, as represented by the arrow108, the catheter14′ has been moved proximally (i.e., leftward in this figure), thereby retracting the most proximal ring electrode104into the introducer shaft76. At that point, the navigation system would no longer receive accurate information from the most proximal ring electrode104. At that point, the navigation system could be configured to ignore the data being collected from the most proximal electrode104, or ignore the data being collected from all of the electrodes34, depending upon the desired settings for a particular physician.

The embodiments shown inFIGS. 5-9actively measure or indicate only when the most proximal electrode104enters the introducer shaft76. It may, however, be desirable to know when each of a plurality of electrodes on the catheter enters into or exits from the distal end of the introducer. A couple of configurations capable of supplying that higher resolution information are described next.

FIG. 10is similar toFIG. 6, but depicts a catheter14″ having a plurality of marker bands98′ on the catheter shaft portion closest to the catheter handle24″. In this particular configuration, there is a separate marker band for each ring electrode and a separate marker band for the tip electrode. In the configuration and relative placement of the catheter14″ and introducer56shown inFIG. 10, the tip electrode110is right at the distal106end of the introducer shaft76. Thus, the marker band112for the tip electrode110is shown just passing the sensor58. InFIG. 10, the distal portion of the introducer shaft wall is broken away to reveal the fact that the three ring electrodes34are inside the sheath. The marker bands corresponding to these electrodes are, therefore, still proximal to the sensor58. That is, the marker bands corresponding to the ring electrodes have not yet passed under the sensor that is attached to the proximal side of the cap60on the hemostasis valve62.

FIG. 11is similar toFIGS. 8 and 9and schematically depicts a marker band and electrode configuration that is also depicted inFIG. 10. As clearly shown inFIG. 11, there is a separate marker band for each of the three electrodes and a single marker band for the tip electrode. Each marker band is separated from its ring or tip electrode by a distance D, which corresponds to the internal length of the introducer. This configuration is, therefore, able to provide information to the navigation system and thus to the clinician when each of the ring electrodes is retracted into the introducer and thus stops supplying reliable location data or patient information to the navigation system. As shown inFIG. 10, the catheter handle24″ may include a LED100for each of the ring electrodes34and an LED114for the tip electrode110. As previously discussed, these indicator lights or LEDs may be visual indicators to the physician about how many and which electrodes are currently providing reliable data to the navigation system10.

FIGS. 12-14depict another embodiment. In this particular embodiment, the sensor58′ (seeFIG. 13) has been moved from the hemostasis valve62″ to the strain relief74′ at the distal end of the steerable introducer handle64′. This may be clearly seen inFIG. 13which is an enlarged view of the circled portion ofFIG. 12. As shown inFIG. 13, the sensor58′ (e.g., a proximity sensor) is embedded in a sidewall adjacent to the inner surface of the introducer shaft and positioned to sense the passing of marker bands on the catheter shaft. InFIGS. 12 and 13, a portion of the strain relief member74′ is broken away so that you can see not only the proximity sensor58′, but also the marker bands on the catheter shaft28″. Similarly, a portion of the introducer sidewall is broken away near the distal end106of the introducer so that it is possible to see that the ring electrodes34at the distal end of the catheter shaft are inside the introducer and the tip electrode110is just exiting the distal end106of the introducer shaft76. The marker band112′ corresponding to the tip electrode is, therefore, just passing by the proximity sensor58′ embedded in the strain relief member74′. In order to transfer signals from the proximity sensor to the navigation system in this embodiment, an electrical lead116would extend to the strain relief member74′ (e.g., inside of the steerable introducer handle).FIG. 14is similar toFIG. 12: however, inFIG. 14the catheter has been inserted deeper into the introducer. At this point, the tip electrode110and all three ring electrodes34at the distal end of the catheter are extended from the distal end of the introducer. The distance D1is the distance from the most proximal ring electrode to the distal end of the introducer, and is also the distance from the most proximal marker band to the proximity sensor mounted in the strain relief member. Again, the catheter handle may include a series of lights to provide visual feedback, and/or audible, tactile or other feedback to a physician as to a number of electrodes providing reliable location data to a navigation system at any point in time.

As described herein, a catheter shaft may be equipped or otherwise configured to accommodate the detection of its own electrodes traversing a distal opening on a partnering introducer. In one embodiment, a catheter, such as catheter14′, includes a catheter shaft28′. The catheter shaft28′ may include one or more electrodes, such as ring electrodes34, at its distal portion. The catheter shaft28′ may further include at least one detectable marker98positioned proximal to the electrode(s)34at the distal portion of the shaft28′. The detectable marker98may be positioned a predetermined distance, such as distance D ofFIGS. 8 and 9, from a most proximal electrode104of the electrode(s)34. In one embodiment, the predetermined distance D may correspond to a distance from a distal opening at the tip78of an interoperable introducer, such as introducers56/86, to a marker detector (e.g., sensors58,58′, sensor head94, etc.) positioned along the introducer proximal to its distal opening. In another embodiment, one or more additional detectable markers98′ may each be positioned proximal to a plurality of the electrodes34at the distal portion of the shaft28′, where each of the detectable markers98′ is positioned a predetermined distance D from a respective one of the plurality the electrodes34.

Since it may be critical to be able to discern which electrodes and how many electrodes are extending past the distal end of the introducer at any particular time, it can be advantageous to sense the location of the electrodes from the distal end of the introducer. In the configuration depicted inFIG. 6, the sensed marker bands are displaced a substantial distance from the electrodes. In the configurations depicted in, for example,FIGS. 12-14, the sensed marker bands have been moved closer to the distal end of the introducer. In the embodiments depicted inFIGS. 15-18, the electrodes are being detected right at the distal end of the introducer.

InFIG. 15, the distal portion of the catheter14′″ is shown extending slightly past the distal end106″ of the introducer56′. Proximity sensors58″ at the distal end of the introducer56′ are shown in dashed lines. In this configuration, the sensors may be, for example, inductive-type sensor coils. In order to provide corresponding data to the navigation system10, a lead wire (not shown) would preferably run in the sidewall of the introducer56′ from the sensors58″ to the connector82at the proximal end of the introducer. Providing lead wires in the sidewall of an introducer can create some manufacturing challenges and may undesirably reduce the inside diameter of the introducer that is available for catheters.

In the embodiments depicted inFIG. 16, the proximity sensor58′″ has been moved to a location on the shaft of the catheter14″″ just proximal of the most-proximal ring electrode104. This proximity sensor58′″ could be configured to detect when it passes the coils or rings118mounted in the distal end106′″ of the introducer56″.

In the embodiment ofFIG. 17, a sensor/detector58″″ projects from the distal surface120of the introducer shaft76″. The sensor/detector58″″ is configured to detect passage of the ring electrodes34and tip electrode110from the distal end of the introducer. This data would be reported back to the navigation system10through the electrical lead116′.

FIG. 18is a fragmentary, schematic view of a distal portion of an introducer shaft76′″ and a distal portion of a catheter shaft28″. A first element122is depicted embedded in the inner wall of the introducer shaft76′″ adjacent the distal end surface of the introducer shaft. A second element124is shown embedded in the outer surface of the catheter shaft28′″. As these two elements pass each other, information could be communicated back to the navigation system10concerning the location of catheter shaft electrodes vis-à-vis the end of the introducer. One of these elements122,124would be a sensed element and the other one would be a sensor. Thus, an electrical lead116″ would run from at least one of these elements back to the navigation system10. InFIG. 18, the lead116″ is shown connected to the second element124.

FIG. 19schematically depicts a section of the inner wall of an introducer shaft above a fragmentary section of a catheter shaft28″″. The inner wall126of the introducer is shown with a plurality of marker bands or stripes128on it, and the catheter shaft is depicted with a single sensor130arranged to pass closely adjacent to the bands128on the inner wall126of the introducer. The bands or stripes128on the inner wall of the introducer could be located anywhere on the length of the introducer. In one configuration, each band has a different color and the sensor130is able to detect color. The sensor is thus able to report back to the navigation system10which band it is closest to, which would allow the navigation system to determine which electrode or electrodes must be extending from the distal end of the introducer, if any. The sensor may also be able to detect a direction of travel of the catheter shaft relative to the introducer after the sensor passes at least two bands.

FIG. 20is similar toFIG. 19, but depicts a catheter shaft28′″″ having a plurality of sensors130mounted and configured to read the plurality of marker bands128on the inner wall126′ of an introducer. This two-sensor configuration would be able to provide both location and directionality information to a navigation system.

FIG. 21is an isometric, fragmentary view of the distal portion of an oft-the-shelf catheter132. In this figure, a stencil134is shown exploded away from the outer surface of the catheter132. The stencil could be used to apply marker band material to create marker bands on the outer surface of an off-the-shelf catheter while in, for example, the EP lab. This embodiment contemplates having a plurality of stencils, possibly one stencil for each of a variety of different types or brands of catheters. Using an appropriate stencil, a physician or technician could ‘paint on’ or ‘apply’ marker bands to the catheter of his or her choice, thereby also permitting the navigation system to determine when the catheter electrodes are outside of the sheath and available for reporting accurate location information.

FIG. 22is a fragmentary, isometric view of an off-the-shelf catheter132mounted in an introducer56(shown schematically in phantom in this figure). As clearly depicted inFIG. 22, the catheter132has three ring electrodes34at its distal end. The most distal ring electrode is shown inFIG. 22about to exit from the distal end of the introducer56. Three marker bands134′, corresponding to the three ring electrodes34, are also depicted inFIG. 22. The most distal marker band is shown about to pass under a proximity sensor58on the introducer since the most distal of ring electrodes34is about to exit the introducer56. Hovering above the marker bands134′ is an ancillary device136that was used to put the marker bands on the catheter shaft. In particular, this reusable, ancillary device136may temporarily and removably clamp on or around a catheter shaft to apply marker bands to an off-the-shelf catheter. The ancillary device136could be clamped around the catheter shaft and then rotated about the catheter shaft's longitudinal axis138in order to draw arcuate or circumferential marker bands on the shaft. Once the bands have been placed on the shaft, the ancillary device would be removed before inserting the catheter into the introducer.

A system10and method for navigating a medical device within a body12in accordance with the present teachings enables consistent correction of errors in position measurements due to shift or drift in patient impedance levels. Further, the system10and method do not require the use of an additional reference catheter and the resulting increases in procedure time and risks.

It will be appreciated that the terms “proximal” and “distal” may be used throughout the specification with reference to a clinician manipulating one end of an instrument used to treat a patient. The term “proximal” refers to the portion of the instrument closest to the clinician and the term “distal” refers to the portion located furthest from the clinician. It will be further appreciated that for conciseness and clarity, spatial or directional terms such as “vertical,” “horizontal,” “up,” “down,” “clockwise,” and “counterclockwise” may be used herein with respect to the illustrated embodiments. However, medical instruments may be used in many orientations and positions, and these terms are not intended to be limiting and absolute. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.