Surgery – Instruments – Electrical application
Reexamination Certificate
1997-12-18
2001-03-13
Cohen, Lee (Department: 3739)
Surgery
Instruments
Electrical application
C606S049000, C607S099000, C607S113000, C607S122000
Reexamination Certificate
active
06200315
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to introducer sheaths used to introduce an electrophysiology catheter into the left atrium of the heart through a transseptal puncture and then direct the catheter to the target region within the left atrium.
The heart includes a number of pathways which are responsible for the propagation of signals necessary for normal electrical and mechanical function. The present invention is concerned with treatment of tachycardia, abnormally rapid rhythms of the heart caused by the presence of an arrhythmogenic site or accessory pathway which bypasses or short circuits the normal pathways in the heart. Tachycardias may be defined as ventricular tachycardias (VTs) and supraventricular tachycardias (SVTs). VTs originate in the left or right ventricle and are typically caused by arrhythmogenic sites associated with or without underlying heart disease. SVTs originate in the atria and are typically caused by an accessory pathway.
Treatment of both ventricular and supraventricular tachycardias may be accomplished by a variety of approaches, including drugs, surgery, implantable pacemakers/defibrillators, and catheter ablation. While drugs may be the treatment of choice for many patients, drugs typically only mask the symptoms and do not cure the underlying cause. Implantable devices, on the other hand, usually can correct an arrhythmia only after it occurs. Surgical and catheter-based treatments, in contrast, will actually cure the problem usually by ablating the abnormal arrhythmogenic tissue or accessory pathway responsible for the tachycardia. The catheter-based treatments rely on the application of various destructive energy sources to the target tissue including direct current electrical energy, radiofrequency electrical energy, laser energy, and the like.
Of particular interest to the present invention, are radiofrequency (RF) ablation protocols which have proven to be highly effective in tachycardia treatment while exposing the patient to minimum side effects and risks. Radiofrequency catheter ablation is generally performed after an initial mapping procedure where the locations of the arrhythmogenic sites and accessory pathways are determined. After mapping, a catheter having a suitable electrode is introduced to the appropriate heart chamber and manipulated so that the electrode lies proximate the target tissue. Radiofrequency energy is then applied through the electrode to the cardiac tissue to ablate a region of the tissue which forms part of the arrhythmogenic site or the accessory pathway. By successfully destroying that tissue, the abnormal signaling patterns responsible for the tachycardia cannot be sustained. Methods and systems for performing RF ablation by controlling temperature at the ablation site are described in U.S. Pat. No. 5,540,681 entitled “Method and System for Radiofrequency Ablation of Tissue.”
Catheters designed for mapping and ablation frequently include a number of individual electrode bands mounted to the distal tip of the catheter so as to facilitate mapping of a wider area in less time, or to improve access to target sites for ablation. Such catheters are described in U.S. Pat. No. 5,445,148 entitled “Intracardiac Electrical Potential Reference Catheter.” Mapping and ablation catheters may facilitate rotational positioning of the distal tip, either by rotating the entire catheter from the proximal end, or by exerting torque on a core wire secured to the distal tip without rotating the catheter body itself. See U.S. Pat. No. 5,545,200 entitled “Steerable Electrophysiology Catheter.” Introducer catheters or sheaths having precurved distal ends have been used for guiding cardiac catheters as well as other types of catheters. See, for example, U.S. Pat. No. 5,147,315 and European Patent Application Publication No. 0670168.
Catheters used in radiofrequency ablation are inserted into a major vein or artery, usually in the neck or groin area, and guided into the chambers of the heart by appropriate manipulation through the vein or artery. Such catheters must facilitate manipulation of the distal tip so that the distal electrode can be positioned against the tissue region to be ablated. The catheter must have a great deal of flexibility to follow the pathway of the major blood vessels into the heart, and the catheter must permit user manipulation of the tip even when the catheter is in a curved and twisted configuration. Because of the high degree of precision required for proper positioning of the tip electrode, the catheter must allow manipulation with a high degree of sensitivity and controllability.
SUMMARY OF THE INVENTION
An ablation catheter, including a sheath and an electrophysiology catheter housed within the sheath, is used to ablate coronary tissue at a target site within the left atrium of a heart. The electrophysiology catheter has a tip with one or more ablation-capable electrodes along at least a portion of the length of the tip. The tip of electrophysiology catheter can be housed within the sheath while the sheath is being manipulated into position within the heart and then extended from the distal open end of the sheath.
The ablation catheter is introduced into the right atrium through either the superior vena or the inferior vena cava. The distal open end of the sheath is guided through a punctured hole in the interatrial septum and into the left atrium. The distal end of the sheath is either precurved or is steerable so that the distal end can be directed towards the desired region of the left atrium. The tip of the electrophysiology catheter is extended from the distal end of the sheath and is manipulated to contact the target site within the left atrium. Energy is then supplied to the tip of the electrophysiology catheter to ablate coronary tissue at a target site. The one or more electrodes are sized and positioned so that an elongate, therapeutically effective ablated lesion can be created at the target site without moving the tip along the target site.
It is generally preferred that the precurved portion of the sheath be at the distal end of the sheath. In some situations it may be desirable to provide an additional, proximal curve spaced apart from the distal end of the sheath to lie within the right atrium. Providing a proximal curve at this position helps to stabilize the sheath, which passed through the inferior vena cava or superior vena cava and into the right atrium, during the electrophysiology procedures. However, using such a dual-curve sheath limits the ability of the user to laterally deflect the curved distal end of the sheath by rotating the sheath about its longitudinal axis. In some situations this drawback is compensated for by the stability added through use of the proximal curve.
The curve at the distal end is preferably short or small. That is, the maximum lateral dimension of the curved distal end is preferably about 0.5 to 2.0 cm, more preferably about 1 cm. The radius of curvature of the curved distal end is preferably about 0.5 cm to 2 cm. By limiting the size of the curved distal end, the user can laterally deflect (torque) the curved distal end 360° so to direct the tip of the electrophysiology catheter passing through the open distal end of the sheath towards a great range of positions within the left atrium. This type of flexibility is not possible when the lateral dimension of the sheath in the left atrium is much larger, such as more than about 3 cm, as is found in some conventional catheters.
The catheter is typically introduced into the right atrium through the inferior/superior vena cava, and into the left atrium through a transseptal puncture at the fossa ovalis. This is typically accomplished with a needle and dilator passed through the sheath. After the distal end of the sheath is housed within the left atrium, the needle and dilator are removed from the sheath; this permits the distal end of the sheath, when precurved, to assume its normal curved shape. The somewhat elastic properties of the sheath help to maintain the sheath in position between the tr
Gaiser John W.
Li Hong
Cohen Lee
Latham Daniel W.
Medtronic Inc.
Patton Harold R.
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