Irrigated tip catheter

FIELD OF THE INVENTION

0001The present invention relates to improved steerable electrode catheters having an irrigated tip.

BACKGROUND OF THE INVENTION

0002Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity.

0003In use, the electrode catheter is inserted into a major vein or artery, e.g., femoral artery, and then guided into the chamber of the heart which is of concern. Within the heart, the ability to control the exact position and orientation of the catheter tip is critical and largely determines how useful the catheter is.

0004In certain applications, it is desirable to have the ability to inject and/or withdraw fluid through the catheter. This is accomplished by means of an irrigated tip catheter. One such application is a cardiac ablation procedure for creating lesions which interrupt errant electrical pathways in the heart.

0005A typical ablation procedure involves the insertion of a catheter having a tip electrode at its distal end into a heart chamber. A reference electrode is provided, generally taped to the skin of the patient. RF (radio frequency) current is applied to the tip electrode, and current flows through the media that surrounds it, i.e., blood and tissue, toward the reference electrode. The distribution of current depends on the amount of electrode surface in contact with the tissue as compared to blood, which has a higher conductivity than the tissue. Heating of the tissue occurs due to its electrical resistance. The tissue is heated sufficiently to cause a lesion. Heating of the electrode results from conduction from the heated tissue. While the blood circulating around the ablation electrode tends to cool it, a stagnant area between the electrode and the tissue may be heated to such a temperature that a thin, transparent coating of blood protein forms on the surface of the tip electrode. This causes an impedance rise. When this occurs, the catheter must be removed and the tip electrode cleaned.

0006When RF current is applied to an ablation electrode in good contact with the endocardium to create a lesion, the temperature of the endocardium drops off very rapidly with distance from the electrode. The resulting lesion tends to be hemispherical, usually about 6 mm in diameter and about 3 to 4 mm deep.

0007When a tip electrode is irrigated, e.g., with room temperature saline, the tip electrode is cooled by the flow of saline through it and the surface of the electrode is flushed. Because the strength of the RF current is no longer limited by the interface temperature, current can be increased. This results in lesions which tend to be larger and more spherical, usually measuring about 10 to 12 mm.

0008In US-A 5,431,168 there is disclosed a steerable irrigated tip catheter comprising a catheter body, a control handle, a tip section, a tip electrode, and means for deflecting the tip section The catheter body has an outer wall, proximal and distal ends and three lumens extending therethrough. The control handle is at the proximal end of the catheter body. The tip section comprises a segment of flexible tubing having proximal and distal ends and three lumens therethrough. The proximal end of the tip section is fixedly attached to the distal end of the catheter body. The tip electrode is fixedly attached to the distal end of the tubing of the tip section. The tip electrode has a fluid passage in fluid communication, with one of the lumens of the tip section. The catheter further includes an infusion tube segment having a proximal end mounted in the distal end of said lumen in the tip section, and a distal end mounted in the fluid passage in the tip electrode. US-A 5,431,168 therefore discloses a catheter of the type set forth in the precharacterising portion of the accompanying claim 1.

0009In WO 96/40344 there is disclosed a steerable catheter in which, instead of three lumens in the catheter body, there is just a single, central lumen.

SUMMARY OF THE INVENTION

0010In accordance with a first aspect of the invention, there is provided a steerable catheter of the type set out in the accompanying claim 1.

0011Further preferred aspects are set out in the accompanying dependent claims.

DESCRIPTION OF THE DRAWINGS

0012These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: <ul id="ul0001" list-style="none" compact="compact"><li>FIG. 1 is a side cross-sectional view of an embodiment of the catheter of the invention.</li><li>FIG. 2 is a side cross-sectional view of a catheter body according to the invention, including the junction between the catheter body and tip section.</li><li>FIG. 3 is a side cross-sectional view of a catheter tip section showing an embodiment having a fluid passage comprising an axial branch and multiple transverse branches.</li><li>FIG. 3A is a side cross-sectional view of a catheter tip section showing an embodiment wherein the fluid passage comprises a longitudinal hole.</li><li>FIG. 4 is a longitudinal cross-sectional view of the tip section illustrated in FIG. 3 across line 4-4.</li><li>FIG. 5 is a side cross-sectional view of an alternative embodiment of a catheter body according to the invention having a side arm for an infusion tube.</li><li>FIG. 6 is a side cross-sectional view of an embodiment of a catheter control handle according to the invention.</li><li>FIG. 7 is a side cross-sectional view of an alternative embodiment of a catheter tip section containing an electromagnetic sensor.</li><li>FIG. 8 is a side cross-sectional view of an alternative embodiment of a catheter containing an electromagnetic sensor.</li><li>FIG. 9 is a longitudinal cross-sectional view of the proximal end of catheter tip section for a bidirectional catheter embodiment according to the invention.</li><li>FIG. 10 is a side cross-sectional view of a bidirectional control handle according to the invention.</li><li>FIG. 11 is a side cross-sectional view of a preferred means for securing the puller wires to the control handle.</li><li>FIG. 12 is a side cross-sectional view of an alternative bidirectional control handle according to the invention.</li><li>FIG. 12A is a longitudinal cross-sectional view of the bidirectional control handle of FIG. 12 along line 12A-12A.</li><li>FIG. 12B is a longitudinal cross-sectional view of the bidirectional control handle of FIG. 12 along line 12B-12B.</li><li>FIG. 12C is a longitudinal cross-sectional view of the bidirectional control handle of FIG. 12 along line 12C-12C.</li><li>FIG. 13 is a side cross-sectional view of the bidirectional control handle of FIG. 12 where the piston is extended distally with respect to the handle housing.</li><li>FIG. 13A is a longitudinal cross-sectional view of the bidirectional control handle of FIG. 13 along line 13A-13A.</li></ul>

DETAILED DESCRIPTION

0013In a particularly preferred embodiment of the invention, there is provided a steerable catheter having an irrigated tip. As shown in FIGs. 1-6, catheter <b>10</b> comprises an elongated catheter body <b>12</b> having proximal and distal ends, a tip section <b>14</b> at the distal end of the catheter body <b>12</b>, and a control handle <b>16</b> at the proximal end of the catheter body <b>12</b>.

0014With reference to FIG. 1, the catheter body <b>12</b> comprises an elongated tubular construction having a single, axial or central lumen <b>18</b>. The catheter body <b>12</b> is flexible, i.e., bendable, but substantially non-compressible along its length. The catheter body <b>12</b> can be of any suitable construction and made of any suitable material. A presently preferred construction comprises an outer wall <b>22</b> made of a polyurethane, or PEBAX. The outer wall <b>22</b> comprises an imbedded braided mesh of stainless steel or the like to increase torsional stiffness of the catheter body <b>12</b> so that, when the control handle <b>16</b> is rotated, the tip section <b>14</b> of the catheter <b>10</b> will rotate in a corresponding manner.

0015Extending through the single lumen <b>18</b> of the catheter body <b>12</b> are lead wires, an infusion tube, and a compression coil through which a puller wire extends. A single lumen catheter body is preferred over a multi-lumen body because it has been found that the single lumen body permits better tip control when rotating the catheter. The single lumen permits the lead wires, infusion tube, and the puller wire surrounded by the compression coil to float freely within the catheter body. If such wires and tube were restricted within multiple lumens, they tend to build up energy when the handle is rotated, resulting in the catheter body having a tendency to rotate back if, for example, the handle is released, or if bent around a curve, to flip over, either of which are undesirable performance characteristics.

0016The outer diameter of the catheter body <b>12</b> is not critical, but is preferably no more than about 2.67 mm (8 french), more preferably 2.33 mm (7 french). Likewise the thickness of the outer wall <b>22</b> is not critical, but is thin enough so that the central lumen <b>18</b> can accommodate an infusion tube, a puller wire, lead wires, and any other wires, cables or tubes. The inner surface of the outer wall <b>22</b> is lined with a stiffening tube <b>20</b>, which can be made of any suitable material, such as polyimide or nylon. The stiffening tube <b>20</b>, along with the braided outer wall <b>22</b>, provides improved torsional stability while at the same time minimizing the wall thickness of the catheter, thus maximizing the diameter of the central lumen <b>18</b>. The outer diameter of the stiffening tube <b>20</b> is about the same as or slightly smaller than the inner diameter of the outer wall <b>22</b>. Polyimide tubing is presently preferred for the stiffening tube <b>20</b> because it may be very thin walled while still providing very good stiffness. This maximizes the diameter of the central lumen <b>18</b> without sacrificing strength and stiffness.

0017A particularly preferred catheter has an outer wall <b>22</b> with an outer diameter of from about 2.29 mm (0.090 inch) to about 2.39 mm (0.094 inch) and an inner diameter of from about 1.55 mm (0.061 inch) to about 1.65 mm (0.065 inch) and a polyimide stiffening tube <b>20</b> having an outer diameter of from about 1.52 mm (0.060 inch) to about 1.63 mm (0.064 inch) and an inner diameter of from about 1.30 mm (0.051 inch) to about 1.42 mm (0.056 inch).

0018As shown in FIGs. 3 and 4, the tip section <b>14</b> comprises a short section of tubing <b>19</b> having three lumens. The tubing <b>19</b> is made of a suitable non-toxic material that is preferably more flexible than the catheter body <b>12</b>. A presently preferred material for the tubing <b>19</b> is braided polyurethane, i.e., polyurethane with an embedded mesh of braided stainless steel or the like. The outer diameter of the tip section <b>14</b>, like that of the catheter body <b>12</b>, is preferably no greater than about 2.67 mm (8 french), more preferably 2.33 mm (7 french). The size of the lumens is not critical. In a particularly preferred embodiment, the tip section <b>14</b> has an outer diameter of about 2.33 mm (7 french (.092 inch)) and the first lumen <b>30</b> and second lumen <b>32</b> are generally about the same size, each having a diameter of from about 0.51 mm (0.020 inch) to about 0.61 mm (0.024 inch), preferably 0.56 mm (0.022 inch), with the third lumen <b>34</b> having a slightly larger diameter of from about 0.81 mm (0.032 inch) to about 0.97 mm (0.038 inch), preferably 0.91 mm (0.036 inch).

0019A preferred means for attaching the catheter body <b>12</b> to the tip section <b>14</b> is illustrated in FIG. 2. The proximal end of the tip section <b>14</b> comprises an outer circumferential notch <b>24</b> that receives the inner surface of the outer wall <b>22</b> of the catheter body <b>12</b>. The tip section <b>14</b> and catheter body <b>12</b> are attached by glue or the like. Before the tip section <b>14</b> and catheter body <b>12</b> are attached, however, the stiffening tube <b>20</b> is inserted into the catheter body <b>12</b>. The distal end of the stiffening tube <b>20</b> is fixedly attached near the distal end of the catheter body <b>12</b> by forming a glue joint <b>23</b> with polyurethane glue or the like. Preferably a small distance, e.g., about 3 mm, is provided between the distal end of the catheter body <b>12</b> and the distal end of the stiffening tube <b>20</b> to permit room for the catheter body <b>12</b> to receive the notch <b>24</b> of the tip section <b>14</b>. A force is applied to the proximal end of the stiffening tube <b>20</b>, and, while the stiffening tube <b>20</b> is under compression, a first glue joint (not shown) is made between the stiffening tube <b>20</b> and the outer wall <b>22</b> by a fast drying glue, e.g. Super Glue®. Thereafter a second glue joint <b>26</b> is formed between the proximal ends of the stiffening tube <b>20</b> and outer wall <b>22</b> using a slower drying but stronger glue, e.g., polyurethane.

0020If desired, a spacer can be located within the catheter body between the distal end of the stiffening tube and the proximal end of the tip section. The spacer provides a transition in flexibility at the junction of the catheter body and tip section, which allows this junction to bend smoothly without folding or kinking. A catheter having such a spacer is described in U.S. Patent Application Serial No. 08/924,616, entitled "Steerable Direct Myocardial Revascularization Catheter".

0021At the distal end of the tip section <b>14</b> is a tip electrode <b>36</b>. Preferably the tip electrode <b>36</b> has a diameter about the same as the outer diameter of the tubing <b>19</b>. As illustrated in FIG. 3, the tip electrode <b>36</b> is generally solid, having a fluid passage <b>35</b> and a pair of blind holes <b>31</b> and <b>33</b> that correspond in size and location to the three lumens <b>34</b>, <b>30</b> and <b>32</b> respectively in the tip section <b>14</b>. The blind holes <b>31</b> and <b>33</b> extend from the proximal end of the tip electrode <b>36</b>, but do not extend through to the distal end of the tip electrode. In the embodiment shown, the fluid passage <b>35</b> comprises an axial branch and six transverse branches <b>48</b> that extend radially from the distal end of the axial branch to the outer surface of the tip electrode <b>36</b>. It is understood that the configuration of the fluid passage may vary as desired.

0022A preferred tip electrode has an effective length, i.e., from its distal end to the distal end of the tubing, of about 3.5 mm, and an actual length, i.e., from its distal end to its proximal end, of about 4.0 mm. As shown in FIG. 3, this preferred tip electrode <b>36</b> is attached to the tubing <b>19</b> by creating a notch <b>37</b> in the proximal end of the tip electrode <b>36</b>, placing the proximal end of the tip electrode on the distal end of the tubing <b>19</b>, and filling the notch <b>37</b> with glue. The wires and tubes that extend into the tip electrode <b>36</b> help to keep the tip electrode in place on the tip section.

0023In the embodiment shown, there are three ring electrodes <b>38</b> mounted on the tubing <b>19</b> proximal to the tip electrode <b>36</b>. It is understood that the presence and number of ring electrodes <b>38</b> may vary as desired. Each ring electrode <b>38</b> is slid over the tubing <b>19</b> and fixed in place by glue or the like.

0024The tip electrode <b>36</b> and ring electrodes <b>38</b> can be made of any suitable material, and are preferably machined from platinum-iridium bar (90% platinum/10% iridium).

0025The tip electrode <b>36</b> and ring electrodes <b>38</b> are each connected to a separate lead wire <b>40</b>. The lead wires <b>40</b> extend through the first lumen <b>30</b> of tip section <b>14</b>, the central lumen <b>18</b> of the catheter body <b>12</b>, and the control handle <b>16</b>, and terminate at their proximal end in an input jack (not shown) that may be plugged into an appropriate monitor (not shown). The portion of the lead wires <b>40</b> extending through the central lumen <b>18</b> of the catheter body <b>12</b>, control handle <b>16</b> and proximal end of the tip section <b>14</b> are enclosed within a protective sheath <b>39</b>, which can be made of any suitable material, preferably polyimide. The protective sheath <b>39</b> is anchored at its distal end to the proximal end of the tip section <b>14</b> by gluing it in the second lumen <b>32</b> with polyurethane glue or the like.

0026The lead wires <b>40</b> are attached to the tip electrode <b>36</b> and ring electrodes <b>38</b> by any conventional technique. Connection of a lead wire <b>40</b> to the tip electrode <b>36</b> is accomplished, for example, by welding the lead wire <b>40</b> into the second hole <b>33</b> in the tip electrode.

0027Connection of a lead wire <b>40</b> to a ring electrode <b>38</b> is preferably accomplished by first making a small hole through the tubing <b>19</b>. Such a hole can be created, for example, by inserting a needle through the tubing <b>19</b> and heating the needle sufficiently to form a permanent hole. A lead wire <b>40</b> is then drawn through the hole by using a microhook or the like. The ends of the lead wire <b>40</b> are then stripped of any coating and soldered or welded to the underside of the ring electrode <b>38</b>, which is then slid into position over the hole and fixed in place with polyurethane glue or the like.

0028A temperature sensing means is provided for the tip electrode <b>36</b> and, if desired, the ring electrodes <b>38</b>. Any conventional temperature sensing means, e.g., a thermocouple or thermistor, may be used. With reference to FIG. 3, a preferred temperature sensing means for the tip electrode <b>36</b> comprises a thermocouple formed by a wire pair. One wire of the wire pair is a copper wire <b>41</b>, e.g., a number <b>40</b> copper wire. The other wire of the wire pair is a constantan wire <b>45</b>, which gives support and strength to the wire pair. The wires <b>41</b> and <b>45</b> of the wire pair are electrically isolated from each other except at their distal ends where they contact and are twisted together, covered with a short piece of plastic tubing <b>43</b>, e.g., polyimide, and covered with epoxy. The plastic tubing <b>43</b> is then attached in the first blind hole <b>31</b> of the tip electrode <b>36</b>, by polyurethane glue or the like. The wires <b>41</b> and <b>45</b> extend through the first lumen <b>30</b> in the tip section <b>14.</b> Within the catheter body <b>12</b> the wires <b>41</b> and <b>45</b> extend through the protective sheath <b>39</b> with the lead wires <b>40</b>. The wires <b>41</b> and <b>45</b> then extend out through the control handle <b>16</b> and to a connector (not shown) connectable to a temperature monitor (not shown).

0029Alternatively, the temperature sensing means may be a thermistor. A suitable thermistor for use in the present invention is Model No. AB6N2-GC14KA143E/37C sold by Thermometrics (New Jersey).

0030A puller wire <b>42</b> extends through the catheter body <b>12</b>, is anchored at its proximal end to the control handle <b>16</b>, and is anchored at its distal end to the tip section <b>14</b>. The puller wire <b>42</b> is made of any suitable metal, such as stainless steel or Nitinol, and is preferably coated with Teflon® or the like. The coating imparts lubricity to the puller wire <b>42</b>. The puller wire <b>42</b> preferably has a diameter ranging from about 0.15 mm (0.006 inches to about 0.25 mm (0.010 inches).

0031A compression coil <b>44</b> is situated within the catheter body <b>12</b> in surrounding relation to the puller wire <b>42</b>. The compression coil <b>44</b> extends from the proximal end of the catheter body <b>12</b> to the proximal end of the tip section <b>14</b>. The compression coil <b>44</b> is made of any suitable metal, preferably stainless steel. The compression coil <b>44</b> is tightly wound on itself to provide flexibility, i.e., bending, but to resist compression. The inner diameter of the compression coil <b>44</b> is preferably slightly larger than the diameter of the puller wire <b>42</b>. The Teflon® coating on the puller wire <b>42</b> allows it to slide freely within the compression coil <b>44</b>. If desired, particularly if the lead wires <b>40</b> are not enclosed by a protective sheath <b>39</b>, the outer surface of the compression coil <b>44</b> can be covered by a flexible, non-conductive sheath, e.g., made of polyimide tubing, to prevent contact between the compression coil <b>44</b> and any other wires within the catheter body <b>12</b>.

0032The compression coil <b>44</b> is anchored at its proximal end to the proximal end of the stiffening tube <b>20</b> in the catheter body <b>12</b> by glue joint <b>50</b> and at its distal end to the tip section <b>14</b> by glue joint <b>51</b>. Both glue joints <b>50</b> and <b>51</b> preferably comprise polyurethane glue or the like. The glue may be applied by means of a syringe or the like through a hole made between the outer surface of the catheter body <b>12</b> and the central lumen <b>18</b>. Such a hole may be formed, for example, by a needle or the like that punctures the outer wall <b>22</b> of the catheter body <b>12</b> and the stiffening tube <b>20</b> which is heated sufficiently to form a permanent hole. The glue is then introduced through the hole to the outer surface of the compression coil <b>44</b> and wicks around the outer circumference to form a glue joint about the entire circumference of the compression coil <b>44</b>.

0033The puller wire <b>42</b> extends into the second lumen <b>32</b> of the tip section <b>14</b>. The puller wire <b>42</b> is anchored at its distal end to the tip electrode <b>36</b> within the second blind hole <b>33</b>. A preferred method for anchoring the puller wire <b>42</b> within the tip electrode <b>36</b> is by crimping metal tubing <b>46</b> to the distal end of the puller wire <b>42</b> and soldering the metal tubing <b>46</b> inside the second blind hole <b>33</b>. Anchoring the puller wire <b>42</b> within the tip electrode <b>36</b> provides additional support, reducing the likelihood that the tip electrode <b>36</b> will fall off the tip section <b>14</b>. Alternatively, the puller wire <b>42</b> can be attached to the side of the tip section <b>14</b>. Within the second lumen <b>32</b> of the tip section <b>14</b>, the puller wire <b>42</b> extends through a plastic, preferably Teflon®, sheath <b>81</b>, which prevents the puller wire <b>42</b> from cutting into the wall of the tip section <b>14</b> when the tip section is deflected.

0034An infusion tube is provided within the catheter body <b>12</b> for infusing fluids, e.g., saline, to cool the tip electrode <b>36</b>. The infusion tube may also be used to infuse drugs or to collect tissue or fluid samples. The infusion tube may be made of any suitable material, and is preferably made of polyimide tubing. A preferred infusion tube has an outer diameter of from about 0.81 mm (0.032 inch) to about 0.91 mm (0.036 inch) and an inner diameter of from about 0.71 mm (0.028 inch) to about 0.81 mm (0.032 inch).

0035With reference to FIGs. 2, 3 and 4, a first infusion tube segment <b>88</b> extends through the central lumen <b>18</b> of the catheter body <b>12</b> and terminates in the proximal end of the third lumen <b>34</b> of the tip section <b>14</b>. The distal end of the first infusion tube segment <b>88</b> is anchored in the third lumen <b>34</b> by polyurethane glue or the like. The proximal end of the first infusion tube segment <b>88</b> extends through the control handle <b>16</b> and terminates in a luer hub <b>90</b> or the like at a location proximal to the control handle. A second infusion tube segment <b>89</b> is provided at the distal end of the third lumen <b>34</b> and extends into the fluid passage <b>35</b> of the tip electrode <b>36</b>. The second infusion tube segment <b>89</b> is anchored within the third lumen <b>34</b> and the fluid passage <b>35</b> by polyurethane glue or the like. The second infusion tube segment <b>89</b>, like the puller wire <b>42</b>, provides additional support for the tip electrode. In practice, fluid may be injected into the first infusion tube segment <b>88</b> through the luer hub <b>90</b>, and flows through the first infusion tube segment <b>88</b>, through the third lumen <b>34</b>, through the second infusion tube segment, into <b>89</b> into the fluid passage <b>35</b> in the tip electrode <b>36</b>, and out the transverse branches <b>48</b> of the fluid passage <b>35</b> in the tip electrode. Again, the fluid passage may have other configurations as desired. For example, the fluid passage <b>35</b> may form a longitudinal hole that extends out the distal end of the tip electrode <b>36</b> , as shown in FIG. 3A, or the tip electrode <b>36</b> may be porous enough to allow fluids to pass to the outer surface of the tip electrode, the interconnecting pores forming the fluid passage.

0036In an alternative arrangement, as shown in FIG. 5, a single lumen side arm <b>94</b> is fluidly connected to the central lumen <b>18</b> near the proximal end of the catheter body <b>12</b>. The first infusion tube segment <b>88</b> extends through the catheter body <b>12</b> and out the side arm <b>94</b>, where it terminates in a luer hub <b>90</b> or the like. The side arm <b>94</b> is preferably made of the same material as the outer wall <b>22</b>, but preferably has a greater thickness, e.g., 1.40 mm (0.055 inch). Where the side arm <b>94</b> meets the catheter body <b>12</b>, a molded joint can be provided to provide additional strength and support. The molded joint can be made of any suitable biocompatable material, and is preferably made of polyurethane.

0037Longitudinal movement of the puller wire <b>42</b> relative to the catheter body <b>12</b>, which results in deflection of the tip section <b>14</b>, is accomplished by suitable manipulation of the control handle <b>16</b>. As shown in FIG. 6, the distal end of the control handle <b>16</b> comprises a piston <b>54</b> with a thumb control <b>56</b> for manipulating the puller wire <b>42</b>. The proximal end of the catheter body <b>12</b> is connected to the piston <b>54</b> by means of a shrink sleeve <b>28</b>.

0038The puller wire <b>42</b>, lead wires <b>40</b>, thermocouple wires <b>41</b> and <b>45</b>, and first infusion tube segment <b>88</b> extend through the piston <b>54</b>. The puller wire <b>42</b> is anchored to an anchor pin <b>57</b>, located proximal to the piston <b>54</b>. Within the control handle <b>16</b>, the lead wires <b>40</b> and thermocouple wires <b>41</b> and <b>45</b> are within the protective sheath <b>39</b>. Within the piston <b>54</b>, the first infusion tube segment <b>88</b> extends into another protective sheath <b>91</b>, preferably made of polyurethane, similar to the side arm <b>94</b>, described above. The protective sheathes <b>39</b> and <b>91</b> are anchored to the piston <b>54</b>, preferably by polyurethane glue or the like at a glue joint <b>53</b>, allowing the first infusion tube segment <b>88</b>, lead wires <b>40</b> and thermocouple wires <b>41</b> and <b>45</b> longitudinal movement within the control handle <b>16</b> so that they does not break when the piston <b>54</b> is adjusted to manipulate the puller wire <b>42</b>. Within the piston <b>54</b>, the puller wire <b>42</b> extends through a transfer tube <b>27</b>, preferably a polyimide tube, to allow longitudinal movement of the puller wire near the glue joint <b>53</b>.

0039The piston <b>54</b> lies within the barrel <b>55</b> of the control handle. The barrel <b>55</b> is generally solid having a piston chamber for receiving the piston <b>54</b>. Extending proximally from the piston chamber are three longitudinal holes <b>58</b>, <b>59</b> and <b>60</b> and a transverse hole for receiving the anchor pin <b>57</b>. The second longitudinal hole <b>59</b> is in communication with the transverse hole. The first infusion tube segment <b>88</b> within the protective sheath <b>91</b> extends through the first longitudinal hole <b>58</b> while the lead wires <b>40</b>. The puller wire <b>42</b> extends through the second longitudinal hole <b>59</b> and is anchored to the anchor pin <b>57</b> in the transverse hole. The thermocouple wires <b>41</b> and <b>45</b> within the protective sheath <b>39</b> extend through the third longitudinal hole <b>60</b>. Between the distal end of the longitudinal holes <b>58</b>, <b>59</b> and <b>60</b> and the proximal end of the piston <b>54</b>, chamber <b>62</b> provides additional space to avoid undesirable bending of the first infusion tube segment <b>88</b>. Preferably the space has a length of at least 0.50 inch and more preferably about from about 1.52 mm (0.60 inch) to about 2.29 mm (0.90 inch).

0040In another preferred embodiment according to the invention, an electromagnetic sensor <b>72</b> is located within the distal end of the tip section <b>14</b>. As shown in FIG. 7, in this embodiment the tip electrode <b>36</b> is connected to the tubing <b>19</b> of the tip section <b>14</b> by means of a plastic housing <b>21</b>, preferably made of polyetheretherketone (PEEK). The proximal end of the tip electrode <b>36</b> is notched circumferentially to form a stem <b>70</b>, which fits inside the distal end of the plastic housing <b>21</b> and is bonded to the housing <b>21</b> by polyurethane glue or the like. The proximal end of the plastic housing <b>21</b> is bonded with polyurethane glue or the like to the distal end of the tubing <b>19</b> of the tip section <b>14</b>. Preferably the plastic housing is about 1 cm long.

0041Preferably the tip electrode <b>36</b> has a total length of about 7 mm, with the stem <b>70</b> having a length of about 3.5 mm (i.e., half the total length of the tip electrode). The distal end of the tip electrode <b>36</b> is generally solid with a blind hole <b>31</b> and a fluid passage <b>33</b> with six transverse branches <b>48</b>. In the embodiment shown, the stem <b>70</b> of the tip electrode <b>36</b> is generally hollow.

0042A second infusion tube segment <b>89</b>, as described above, extends into and is anchored in the fluid passage <b>33</b> of the tip electrode <b>36</b>. The infusion tube segments <b>88</b> and <b>89</b> preferably have an outer diameter of about from 0.74 mm (0.029 inch) to about 0.84 mm (0.033 inch) and an inner diameter of from about 0.64 mm (0.025 inch) to about 0.74 mm (0.029 inch).

0043A puller wire <b>42</b> extends into and is anchored in the blind hole <b>31</b> of the tip electrode <b>36</b>. A pair of thermocouple wires <b>41</b> and <b>45</b>, as described above, also extend into and are soldered into the first hole <b>31</b> of the tip electrode <b>36</b>, and the copper wire <b>41</b> acts also as a lead wire <b>40</b> for the tip electrode. The electromagnetic sensor <b>72</b> is positioned within the plastic housing <b>21</b> and hollow stem <b>70</b> of the tip electrode <b>36</b>. The sensor <b>72</b> is fixedly attached within the tip electrode <b>36</b> and the plastic housing <b>21</b> by polyurethane glue or the like.

0044Mounted on the plastic housing <b>21</b> are three ring electrodes <b>38</b>. The presence and number of ring electrodes <b>38</b> can vary as desired. Each ring electrode <b>38</b> is slid over the plastic housing <b>21</b> and fixed in place by glue or the like. Alternatively, one or more ring electrodes <b>38</b> can be positioned over the flexible tubing <b>19</b> of the tip section <b>14</b>.

0045Lead wires are attached to the ring electrodes <b>38</b> generally as described above. However, due to the length of the plastic housing <b>21</b>, the most distal ring electrode <b>38</b> is mounted on the plastic housing <b>21</b> at a position above the stem <b>70</b> of the tip electrode <b>36</b>. As a result, the lead wire <b>40</b> for the most distal ring electrode <b>38</b> extends though a hole <b>49</b> in the plastic housing <b>21</b> that is proximal to the distal ring electrode <b>38</b> and stem <b>70</b>. The lead wire <b>40</b> extends a short distance along the outside of the plastic housing <b>21</b> and is soldered to the underside of the most distal ring electrode <b>38</b>. Polyurethane glue or the like is used to cover the exposed section of the lead wire <b>40</b> and to fill in the hole <b>49</b>.

0046The electromagnetic sensor <b>72</b> is connected to a electromagnetic sensor cable <b>74</b>, which extends through the third lumen <b>34</b> of the tip section <b>14</b>, through the central lumen <b>18</b> of the catheter body <b>12</b>, and into the control handle <b>16</b>. The electromagnetic sensor cable <b>74</b> then extends out the proximal end of the control handle <b>16</b> within an umbilical cord <b>78</b> to a sensor control module <b>75</b> that houses a circuit board (not shown). Alternatively, the circuit board can be housed within the control handle <b>16</b>, for example, as described in U.S. Patent Application Serial No. 08/924,616, entitled "Steerable Direct Myocardial Revascularization Catheter". The electromagnetic sensor cable <b>74</b> comprises multiple wires encased within a plastic covered sheath. In the sensor control module <b>75</b>, the wires of the electromagnetic sensor cable <b>74</b> are connected to the circuit board. The circuit board amplifies the signal received from the electromagnetic sensor <b>72</b> and transmits it to a computer in a form understandable by the computer by means of the sensor connector <b>77</b> at the proximal end of the sensor control module <b>75</b>, as shown in FIG. 8. Also, because the catheter is designed for single use only, the circuit board preferably contains an EPROM chip which shuts down the circuit board approximately <b>24</b> hours after the catheter has been used. This prevents the catheter, or at least the electromagnetic sensor, from being used twice. Suitable electromagnetic sensor for use with the present invention are described, for example, in U.S. Patent Nos. 5,558,091, 5,443,489, 5,480,422, 5,546,951, 5,568,809, and 5,391,199 and International Publication No. WO 95/02995. A preferred electromagnetic mapping sensor <b>72</b> has a length of from about 6 mm to about 7 mm and a diameter of about 1.3 mm.

0047To use the electromagnetic sensor <b>72</b>, the patient is placed in a magnetic field generated, for example, by situating under the patient a pad containing coils for generating a magnetic field. A reference electromagnetic sensor is fixed relative to the patient, e.g., taped to the patient's back, and the catheter containing a second electromagnetic sensor is advanced into the patient's heart. Each sensor comprises three small coils that in the magnetic field generate weak electrical signals indicative of their position in the magnetic field. Signals generated by both the fixed reference sensor and the second sensor in the heart are amplified and transmitted to a computer that analyzes the signals and then displays the signals on a monitor. By this method, the precise location of the sensor in the catheter relative to the reference sensor can be ascertained and visually displayed. The sensor can also detect displacement of the catheter that is caused by contraction of the heart muscle.

0048Using this technology, the physician can visually map a heart chamber. This mapping is done by advancing the catheter tip into a heart chamber until contact is made with the heart wall. This position is recorded and saved. The catheter tip is then moved to another position in contact with the heart wall and again the position is recorded and saved. This procedure is repeated until a three-dimensional image of the heart chamber is achieved. A preferred mapping system includes a catheter comprising multiple electrodes and an electromagnetic sensor.

0049The catheter body <b>12</b> is generally similar to that described above, having an open central lumen <b>18</b>. Preferably, the catheter body <b>12</b> in this embodiment does not comprise a stiffening tube <b>20</b>, however, because additional space is needed within the central lumen <b>10</b> to include the electromagnetic sensor cable sensor cable <b>74</b>. Preferably the catheter body has an outer diameter no greater than about 2.67 mm (8 French), more preferably about 2.33 mm (7 French to about 2.50 mm (7.5 French)

0050The control handle <b>16</b> is also generally similar to that described above. However, the electromagnetic sensor cable <b>74</b> extends out the proximal end of the control handle <b>16</b> where it is connected to the sensor control module <b>75</b>.

0051An alternative embodiment of a catheter according to the present invention is a bidirectional catheter containing two puller wires to enhance the ability to manipulate the tip section. As illustrated in FIG. 9, the tip section <b>14</b> of this embodiment contains four lumens. For a tip section having a diameter of about 2.33 mm (7 French), the diameters of the first lumen <b>30</b> and second lumen <b>32</b> are similar in size, and are each preferably 0.46 mm (0.018 inch). The diameters of the third lumen <b>34</b> and fourth lumen <b>35</b> are also similar in size and are each preferably 0.74 mm (0.029 inch) The tip section <b>14</b> carries a tip electrode <b>36</b> and ring electrodes <b>38</b>. A thermocouple, or other temperature sensing means, is provided for the tip electrode <b>36</b> as discussed above. The lead wires <b>40</b> for the ring electrodes <b>38</b>, as well as the thermocouple wires <b>40</b> and <b>45</b>, one of which serves as the tip electrode lead wire, extend through the third lumen <b>34</b>. The tip section <b>14</b> also contains an electromagnetic sensor <b>72</b>, and the electromagnetic sensor cable <b>74</b> also extends through the third lumen <b>34</b>. A first infusion tube segment <b>88</b> extends through the control handle <b>16</b> and catheter body <b>12</b> and into the fourth lumen <b>35</b>. A second infusion tube segment <b>89</b> extends from the distal end of the fourth lumen <b>35</b> in the tip section <b>14</b> and into the tip electrode <b>36</b> in a manner similar to the embodiment described above.

0052Two puller wires <b>34</b> and surrounding compression coils <b>44</b> extend from the control handle <b>16</b> through the central lumen <b>18</b> of the catheter body <b>12</b> as described above. Within the tip section <b>14</b>, one puller wire <b>34</b> extends into the first lumen <b>30</b> and the other puller wire extends into the second lumen <b>32</b>. The puller wires <b>34</b> then extend into holes in the tip electrode <b>36</b> preferably coaxial with the first lumen <b>30</b> and second lumen <b>32</b> and are anchored within the holes of the tip electrode as described above. Within the tip section <b>14</b>, the puller wires <b>34</b> each extend through a plastic, preferably Teflon®, sheath <b>81</b>, to prevent the puller wires <b>42</b> from cutting into the wall of the tip section <b>14</b> when the tip section is deflected The lumens <b>30</b> and <b>32</b> of the tip section receiving the puller wires may be in adjacent quadrants, but are preferably in opposing quadrants. If desired, the distal ends of one or both of the puller wires may be anchored to the side wall of the catheter tip section for example as described in U.S. Patent Application Serial No. 08/924,611, reference. Moreover, the first puller wire may be anchored proximal to the anchor location of the second puller wire.

0053A particularly preferred catheter construction comprising multiple puller wires including control handle construction is disclosed in U.S. Patent Application Serial No. 08/924,611, entitled "Omni-Directional Steerable Catheter". Such application describes a suitable control handle for manipulating two or more puller wires. The described control handle includes a central passage that may be expanded to accommodate the electrode lead wires, electromagnetic sensor cable, optic fiber and even infusion tube. Further, an extension of the handle may be provided to house the circuit board for the electromagnetic sensor, e.g., in the same manner as shown in FIG. 8 .

0054An alternative control handle <b>16</b> particularly suitable for the bidirectional catheter embodiment of the invention is illustrated in FIG. <b>10</b>. The control handle <b>16</b> comprises a generally solid and generally cylindrical housing <b>102</b> having a nose piece <b>104</b> at its distal end. The housing <b>102</b> and nose piece <b>104</b> can be made of any suitable material, preferably acetal. The catheter body <b>12</b> is fixedly attached to the nose piece <b>104</b> by means of a shrink sleeve, as described above.

0055Within the housing <b>102</b> are two rack gear channels <b>105</b>. Preferably the rack gear channels <b>105</b> are located in opposite quadrants within the housing <b>102</b>. Slidably mounted within each rack gear channel <b>105</b> is a rack gear <b>106</b>. Each rack gear <b>106</b> is generally rectangular having teeth <b>108</b> along the length of its interior edge. Between the rack gears <b>106</b> is a spur gear <b>110</b>, also having teeth <b>112</b>. The teeth <b>112</b> of the spur gear <b>110</b> receive the teeth <b>108</b> of the rack gears <b>106</b> such that proximal movement off one rack gear results in distal movement of the other rack gear.

0056The proximal end of each puller wire <b>42</b> is attached to the distal end of one of the rack gears <b>106</b> by a puller wire coupling <b>114</b>. The coupling <b>114</b> may be integral with the rack gear <b>106</b> or fixedly attached to it. Each rack gear <b>106</b> may be soldered or glued to the coupling <b>114</b>, for example, with polyurethane or epoxy. Alternatively, the proximal end of each puller wire coupling <b>114</b> may comprise a threaded hole to receive a threaded post at the distal end of the corresponding rack gear <b>106</b>. The couplings <b>114</b> can be made of any suitable material, preferably aluminum.

0057As shown in FIG. 11, the distal end of each coupling <b>114</b> contains a threaded axial hole <b>115</b> that receives a threaded set screw <b>116</b>. The set screw <b>116</b> has an axial bore <b>118</b> therethrough for passage of the proximal end of the puller wire <b>42</b>. In a preferred embodiment, the axial bore <b>118</b> has a distal section with a diameter slightly larger than the diameter of the puller wire <b>42</b> and a proximal section having a diameter larger than that of the distal section. The axial bore <b>118</b> extends through the proximal end of the set screw <b>116</b>.

0058The puller wire <b>42</b> extends through the axial bore <b>118</b> of the set screw <b>116</b> and is anchored thereto. A preferred means for anchoring the puller wire <b>42</b> to the set screw <b>116</b> comprises a short piece of hypodermic stock <b>120</b> that is fixedly attached, i.e., by crimping, to the proximal end of the puller wire <b>42</b> after it has passed through the distal section of the axial bore <b>118</b> of the set screw <b>116</b>. The hypodermic stock <b>120</b> has a diameter greater than the diameter of the distal section of the axial bore <b>118</b> and prevents the puller wire <b>42</b> from being pulled through the set screw <b>116</b>. As an alternative, a cross-member, e.g., stainless steel ribbon, may be welded to the proximal end of the puller wire <b>42</b> such that the cross-member prevents the puller wire from being pulled through the axial bore <b>118</b> of the set screw <b>116</b>. It is understood that any mechanism for attaching the proximal end of the puller wire to the coupling <b>114</b> may be used.

0059Within the coupling <b>114</b> is an axial hole <b>119</b>, which has a diameter similar to the distal end of the axial bore <b>118</b> in the set screw <b>116</b>. The distal end of the axial hole <b>119</b> is in communication with the proximal end of the axial bore <b>118</b> to provide a passage into which the puller wire <b>42</b> can extend when the corresponding rack gear <b>106</b> and coupling <b>114</b> are moved distally. This prevents the puller wire <b>42</b> from buckling.

0060The handle housing <b>102</b> contains a slot <b>122</b> along one side, corresponding with the position of one of the rack gears <b>106</b>. A set screw <b>124</b> extends through the slot <b>122</b> into the rack gear <b>106</b> through the puller wire coupling <b>114</b>. A deflection knob <b>126</b> is placed on the outside end of the set screw <b>124</b> for easy manipulation of the control handle <b>16</b>. The deflection knob <b>126</b> extends around the circumference of the handle housing <b>102</b>, allowing the user to manipulate the knob <b>126</b> no matter how the handle is turned. Preferably the set screw <b>124</b> is positioned on the rack gear <b>106</b> so that when both rack gears <b>106</b> are in a neutral position, i.e., in line with each other, the deflection knob <b>126</b> is situated approximately at the midsection of the slot <b>122</b>.

0061When the deflection knob <b>126</b> is moved proximally, the corresponding rack gear <b>106</b> moves in a proximal direction. The attached puller wire <b>42</b> also is pulled proximally, causing the tip section <b>14</b> to deflect in the direction of the quadrant of the lumen in the tip section <b>14</b> through which that puller wire extends. Conversely, when the deflection knob <b>126</b> is pushed distally, the corresponding rack gear <b>106</b> moves distally. As a result, the opposite rack gear <b>106</b> moves proximally, pulling the corresponding puller wire <b>42</b> and deflecting the tip section <b>14</b> in the opposite direction.

0062Passages are provided within the handle housing <b>102</b> for the infusion tube <b>88</b>, lead wires <b>40</b>, thermocouple wires <b>41</b> and <b>45</b> and sensor cable <b>74</b> to extend through the housing <b>102</b> and out the distal end. The infusion tube <b>88</b>, lead wires <b>40</b>, thermocouple wires <b>41</b> and <b>45</b> and sensor cable <b>74</b> extend out the proximal end of the handle housing <b>102</b> and attached to a luer hub or to appropriate monitors, as described above.

0063Another alternative bidirectional handle design is illustrated in FIGs. 12 and 13. As shown in FIGs. 12, 12A, 12B and 12C, the control handle <b>16</b> comprises a generally tubular handle housing <b>102</b>, which can be made of any suitable rigid material. The housing <b>102</b> comprises three piston chambers, an axial distal piston chamber <b>131</b> and two smaller proximal piston chambers <b>135</b>. The proximal piston chambers <b>135</b> are preferably in opposite quadrants of the housing and overlap the distal piston chamber <b>131</b>. Mounted within the distal piston chamber <b>131</b> and extending out of the distal end of the housing <b>102</b> is a slidable distal piston <b>130</b> having a thumb rest <b>132</b> at its distal end and an axial passage <b>133</b>. The proximal end of the catheter body <b>12</b> is attached, e.g., by glue, to the distal piston <b>130</b>. The protective sheath <b>39</b> containing the puller wires <b>42</b>, lead wires <b>40</b>, thermocouple wires <b>41</b> and <b>45</b>, and the first infusion tube <b>88</b> extend through the axial passage <b>133</b> of the distal piston <b>130</b>. Proximal to the distal piston <b>130</b>, two slidable proximal pistons <b>134</b> are located in the proximal piston chambers <b>135</b>. The proximal pistons <b>134</b> can be made of any suitable material. Aluminum is presently preferred. Each puller wire <b>42</b> is anchored at its proximal end to the distal end of a proximal piston <b>134</b>. The puller wires <b>42</b> can be fixedly attached to the proximal pistons <b>134</b> by any suitable means, for example, by means of a coupling as described above.

0064In this arrangement, distal movement of the distal piston <b>130</b> relative to the handle housing <b>102</b> by pushing on the thumb rest <b>132</b> also results in distal movement of the catheter body <b>12</b>, the puller wires <b>42</b> and the proximal pistons <b>134</b> to which the puller wires are attached. Tip deflection does not occur however when both puller wires are moved simultaneously. Accordingly, means are provided for preventing simultaneous movement of the puller wires.

0065The means for preventing simultaneous movement of the puller wires <b>42</b> comprises means for anchoring, i.e., preventing movement of, one, but not both, of the proximal pistons <b>134</b>. This is done by the combination of a circumferential notch <b>140</b> along the length of each proximal piston <b>134</b> and a means for engaging the circumferential notch <b>140</b> of a selected one of the proximal pistons <b>134</b>.

0066A preferred engaging means comprises a movable bar <b>142</b> which extends diametrically through the handle housing <b>102</b> and extends slightly out of the housing on each side to thereby create what appears to be a button on each side of the housing at a position corresponding to the circumferential notches <b>104</b> of the proximal pistons <b>134</b> as shown in FIGs. 12 and 12A. As shown in FIGs. 13 and 13A, the bar <b>142</b> comprises a generally oval slot <b>146</b>. Both of the proximal pistons <b>134</b> extend through the slot <b>146</b>. The slot <b>146</b> has a width slightly greater than the diameter of the proximal pistons <b>134</b>. The height of the bar <b>142</b> is less than the length of the circumferential notches <b>140</b> so that the bar <b>142</b> can be received by and engages the notches <b>140</b>. The length of the slot <b>146</b> is selected to allow lengthwise movement of only one proximal piston <b>134</b> at a time. That is, as shown in FIG. 13, the bar <b>142</b> has been moved in a first direction until the end of the slot <b>146</b> engages the circumferential notch of one proximal piston <b>134</b>. In this arrangement, the engaged proximal piston is prevented from moving longitudinally by the bar <b>142</b>, but the other proximal piston can move freely through the slot <b>146</b>. If the bar <b>142</b> is moved in the other direction the previously engaged proximal piston will be afforded free longitudinal movement and the previously freely moving proximal piston will be engaged.

0067When a proximal piston <b>134</b> is engaged by the bar <b>142</b>, it acts as a fixed anchor for the puller wire <b>42</b> attached to it. Hence when the distal piston <b>130</b> is moved distally relative to the housing <b>102</b> by pushing the thumb rest <b>132</b>, the catheter body <b>12</b> will move distally relative to the anchored puller wire <b>42</b>. This results in deflection of the tip section <b>14</b> in the direction of the tip lumen carrying that puller wire. When the opposite proximal piston is engaged, deflection of the tip in the opposite direction will occur.

0068The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the scope of this invention as defined by the following claims.

0069Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope.