The invention pertains to devices usable for non-invasive heart pacing. More particularly, the invention pertains to esophageal catheters usable for non- invasive cardiac pacing. Background of the Invention

Transvenous catheters are known for use in invasive cardiac pacing. Such catheters have a distal end which can be inserted, via a vein of a patient, into the appropriate chamber of a patient's heart so as to carry out a pacing operation.

It's also been known to use transvenous catheters, at least experimentally, in esophageal pacing. Such catheters have first and second spaced-apart electrodes located on a distal end thereof. The electrodes are positioned in the esophagus appropriately with respect to the posterior surface of the patient's heart so as to carry out a pacing operation. Results of experiments using such bipolar transvenous catheters for esophageal pacing were presented, in part, at the Fifty- Third Scientific Sessions of the American Heart Association, November 19, 1980. Results of that work were subsequently published in the journal Circulation in 1982. Notwithstanding the above-noted uses for transvenous catheters, none of the known transvenous catheters provide any adjustment of the flexibility or stiffness thereof during insertion. Further, transvenous catheters at times terminate in a hard electrode member which can cause some discomfort to the patient on insertion through the nasal passages into the esophagus. Hence, there continues to be a need for cost- effective esophageal pacing catheters which are readily inserted and which cause minimal patient discomfort and/or trauma.

Summary of the Invention

A variable stiffness esophageal catheter has an elongated body portion with a proximal end and a distal end. The catheter has a soft tip which is rounded and sealed which is carried on the distal end of the body portion.

A stylet is slidably positioned within the body portion and is usable for adjusting the stiffness characteristic thereof. First and second electrodes are carried spaced apart from one another on the distal end of the body portion. One of the electrodes is positioned adjacent the flexible tip. The electrodes can be formed of platinum.

In a disclosed embodiment the body portion is formed out of first and second elongated flexible polyethylene cylindrical members. One member is positioned inside of the other member and extends axially therewith.

First and second conducting wires extend axially in a region between the two cylindrical polyethylene members from the proximal end of the body portion to the distal end thereof. The conducting wires are each electrically connected to a respective one of two electrodes at the distal end of the catheter. At the proximal end of the catheter the two electrical wires are each terminated in an electrical connector.

The stylet extends axially through the interior elongated polyethylene member. The stylet is formed of a stainless steel rod. The flexibility of this rod is much less than that of the catheter body.

The catheter may be inserted into a patient's esophagus via the nasal passages and sinus cavities. Alternately, the catheter could be inserted orally. The soft, flexible tip reduces trauma to the patient's tissues and improves insertion comfort.

The slidably removable stylet can be used to alter the flexibility of the body portion as the catheter is being positioned in the esophagus of the patient.

Once the spaced-apart electrodes are properly located with respect to the posterior surface of the patient's heart, the electrical connections at the proximal end may be used to apply electrical energy to the spaced-apart electrodes to carry out a pacing procedure.

Alternately, the electrodes can be used to carry out a cardiac monitoring function.

Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings in which the details of the invention are fully and completely disclosed as a part of this specification. Brief Description of the Drawings

Figure l is a top view of an esophageal catheter with the stylet partly withdrawn therefrom;

Figure 2 is a top view of the esophageal catheter with the stylet completely withdrawn therefrom;

Figure 3 is a view in section taken along plane 3-3 of Figure 1; Figure 4 is a view in section taken along plane

4-4 of Figure 1; and

Figure 5 is a fragmentary left sagittal view of a patient with an esophageal catheter inserted and properly positioned adjacent a posterior heart surface. Detailed Description of the Preferred Embodiments

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will be described herein in detail a specific embodiment thereof with the understanding that the present disclosure is to be considered as an exemplification of

the principles of the invention and is not intended to limit the invention to the specific embodiment illustrated.

A variable flexibility esophageal catheter 10 is illustrated in Figure 1. The catheter 10 includes a flexible elongated body portion 12 with a proximal end 14 and a distal end 16.

Carried on the body portion 12 adjacent the distal end 16 are first and second spaced-apart electrodes 18 and 20. Adjacent the electrode 20 is a soft catheter tip 26 which has a rounded and sealed end 28.

The body portion 12 and the catheter tip 26 can both be formed of polyethylene. The tip 26 is flexible.

The proximal end 14 terminates at a bifurcated coupler 32. Input to the bifurcated coupler 32 includes a first electrical connector lead 34 which is electrically coupled through the coupler 32 and the body member 12 to the electrode 20. A second electrical connector lead 36 is coupled via the coupler 32 and the body member 12 to the electrode member 18.

A centrally located lumen 38 to the coupler 32 slidably receives an elongated axially extending stylet 42. The stylet 42 is illustrated at Figure 1 partly withdrawn from the body portion 12 of the catheter 10. The slidably engageable stylet 42 provides for variable flexibility as the catheter 10 is being inserted via a patient's nasal passages into the esophagus. The soft round-ended catheter tip 26 improves insertion comfort and reduces trauma to the patient's tissues. Figure 2 illustrates the catheter 10 with the stylet 42 removed therefrom. The stylet 42 includes a manually grippable knob 46 coupled to an elongated cylindrical stiffening member 48.

The member 48 can be formed of a medical-grade stainless steel and may be somewhat flexible. However,

the degree of flexibility of the member 48 is substantially less than the degree of flexibility of the body member 12 with the stylet 42 withdrawn.

Figure 3, a sectional view taken along plane 3-3 of Figure 1, illustrates the structure of the body member

12 in detail. The body member 12 is formed of an exterior flexible cylindrical member 52. The member 52 defines an interior, closed, axially extending region or lumen 54.

Positioned within the axially extending lumen 54 is a second flexible elongated cylindrical member 56.

The member 56 defines a second, closed, interior elongated lumen 58 therein.

The member 54 is formed of polyethylene. The member 56 is formed of flexible, high-density polyethylene.

First and second insulated conducting wires 62 and 64 are positioned in the lumen 54. The wires 62 and 64 extend substantially axially through the length of the body member 12 and respectively couple the proximal end electrical connector leads 34 and 36 to the electrodes 20 and 16 respectively.

The insulated wires 62, 64 can be formed as a twisted pair or can be located coextensively in the region 54 without being twisted together. The elongated body portion 48 of the stylet 42 is illustrated in Figure 3 positioned in the second axially extending elongated lumen 58.

Figure 4, a sectional view taken along plane 4- 4 of Figure 1, illustrates the relationship of the electrode 20 to the body member 12. The electrode 20 is carried on the polyethylene member 52 in contact therewith. Since the stylet 42 has been illustrated in Figure 1 partly withdrawn from the body member 12, it does not appear in the section of Figure 4.

The electrodes 18, 20 can be formed of platinum or any other acceptable conductor. The electrodes 18, 20 could be deposited on the member 52. Alternately, the electrodes 18, 20 may be formed as separate conducting members that are then affixed to the distal end of the member 52. The exact way in which the electrodes 18, 20 are formed and attached to the body member 12 is not a limitation of the present invention.

Figure 5 illustrates a fragmentary sagittal view of a patient P. The patient P has an esophagus E in which a catheter 10 in accordance with the present invention has been inserted. The electrodes 18 and 20 have been positioned adjacent a posterior surface of the heart H of the patient P. As illustrated in Figure 5, the body portion 12 of the catheter 10 has been inserted through the nasal passages of the patient P. Proper insertion has required that the body portion 10 undergo a substantial bend 70 when passing from the region of the patient's sinuses into the esophagus E. The soft tip 28 minimizes trauma as the distal end 16 makes the bend 70.

The catheter 10 can be inserted with the stylet 42 positioned therein. The stylet 42 is of a size which is flexible enough to readily deflect or bend as necessary to pass into the esophagus.

When the electrodes 18 and 20 have been positioned far enough into the esophagus, the stylet 42 can be withdrawn and the patient can, by swallowing, cause the electrodes 18, 20 and the soft tip 28 to move downwardly into the esophagus E until the electrodes approach the desired position adjacent the posterior surface of the heart H. Alternately, the stylet 42 can be left fully inserted into the catheter 10 until the electrodes 18 and 20 have been properly positioned.

As illustrated in Figure 5, the soft tip 28 is particularly useful in reducing trauma to the patient P during insertion of the catheter.

The exterior diameter of the cylindrical polyethylene member 52 can be on the order of .058 inches.

The interior diameter thereof can be on the order of .045 inches. The exterior diameter of the member 52 corresponds to the size of a 4 French catheter.

The exterior diameter of the high-density polyethylene cylindrical member 56 can be on the order of .030 inches. The interior diameter of the member 56 can be on the order of .022 inches. The exterior diameter of the body 48 of the stylet can be on the order of .016 inches. The overall length of the catheter 10 can be on the order of 1 meter.

It will be understood that the actual diameter of the member 52 is not a limitation of the present invention. For example, alternate sizes such as 5 or 6 French could also be used. From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the novel concept of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.