Surgery – Instruments – Electrical application
Reexamination Certificate
1999-07-27
2001-07-24
Cohen, Lee (Department: 3739)
Surgery
Instruments
Electrical application
C606S049000, C607S101000, C607S116000
Reexamination Certificate
active
06264654
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to catheters for the mapping and ablation of human tissue, particularly cardiac tissue. In particular, the invention relates to an ablation catheter to ablate human tissue utilizing conductive media contacted by an electrode, which electrode is contained within the catheter.
BACKGROUND
Catheters have been in use for medical procedures for many years. Catheters can be used for medical procedures to examine, diagnose and treat while positioned at a specific location within the body which is otherwise inaccessible without more invasive procedures. During these procedures a catheter is inserted into a vessel near the surface of the body and is guided to a specific location within the body for examination, diagnosis and treatment. For example, one procedure utilizes a catheter to convey an electrical stimulus to a selected location within the human body. Another procedure utilizes a catheter with sensing electrodes to monitor various forms of electrical activity in the human body.
Catheters are also used increasingly for medical procedures involving the human heart. Typically, the catheter is inserted in an artery or vein in the leg, neck or arm of the patient and threaded, sometimes with the aid of a guidewire or introducer, through the vessels until a distal tip of the catheter reaches the desired location for the medical procedure in the heart.
A typical human heart includes a right ventricle, a right atrium, a left ventricle and a left atrium. The right atrium is in fluid communication with the superior vena cava and the inferior vena cava. The atrioventricular septum separates the right atrium from the right ventricle. The tricuspid valve contained within the atrioventricular septum provides communication between the right atrium and the right ventricle.
In the normal heart, contraction and relaxation of the heart muscle (myocardium) takes place in an organized fashion as electro-chemical signals pass sequentially through the myocardium from the sinoatrial (SA) node to the atrioventricular (AV) node and then along a well defined route which includes the His-Purkinje system into the left and right ventricles. The AV node lies near the ostium of the coronary sinus in the interatrial septum in the right atrium. The His-Purkinje system begins at the AV node and follows along the membranous interatrial septum toward the tricuspid valve through the atrioventricular septum and into the membranous interventricular septum. At about the middle of the interventricular septum, the His-Purkinje system splits into right and left branches which straddle the summit of the muscular part of the interventricular septum.
Sometimes abnormal rhythms occur in the heart which are referred to generally as arrhythmia. For example, a common arrhythmia is Wolff-Parkinson-White syndrome (W-P-W). The cause of W-P-W is generally believed to be the existence of an anomalous conduction pathway or pathways that connect the atrial muscle tissue directly to the ventricular muscle tissue, thus bypassing the normal His-Purkinje system. These pathways are usually located in the fibrous tissue that connects the atrium and the ventricle.
Other abnormal arrhythmias sometimes occur in the atria, which are referred to as atrial arrhythmia. Three of the most common atrial arrhythmia are ectopic atrial tachycardia, atrial fibrillation and atrial flutter. Atrial fibrillation can result in significant patient discomfort and even death because of a number of associated problems, including: an irregular heart rate which causes patient discomfort and anxiety, loss of synchronous atrioventricular contractions which compromises cardiac hemodynamics resulting in varying levels of congestive heart failure, and stasis of blood flow, which increases the likelihood of thromboembolism.
Efforts to alleviate these problems in the past have included significant usage of pharmacological treatments. While pharmacological treatments are sometimes effective, in some circumstances drug therapy has had only limited effectiveness and is frequently plagued with side effects, such as dizziness, nausea, vision problems and other difficulties.
An increasingly common medical procedure for the treatment of certain types of cardiac arrhythmia is catheter ablation. During conventional catheter ablation procedures an energy source is placed in contact with cardiac tissue to heat the tissue and create a permanent scar or lesion. During one procedure the lesions are designed to interrupt existing conduction pathways commonly associated with arrhythmias within the heart. The particular area for ablation depends on the type of underlying arrhythmia. One common ablation procedure treats atrioventricular nodal reentrant tachycardia (AVNRT). Ablation of fast or slow AV nodal pathways is disclosed in Singer, I., et al., “Catheter Ablation for Arrhythmias”
Clinical Manual of Electrophysiology,
pgs. 421-431 (1993). The use of electrode catheters for ablating specific locations within the heart has also been disclosed, for example in U.S. Pat. Nos. 4,641,649, 5,263,493, 5,231,995, 5,228,442 and 5,281,217.
Another medical procedure using ablation catheters with sheaths to ablate accessory pathways associated with W-P-W utilizing both a transseptal and retrograde approach is discussed in Saul, J.P., et al. “Catheter Ablation of Accessory Atrioventricular Pathways in Young Patients: Use of long vascular sheaths, the transseptal approach and a retrograde left posterior parallel approach”
Journal of the American College of Cardiology
, Vol. 21, no. 3, pgs. 571-583 (Mar. 1, 1993). Other catheter ablation procedures are disclosed in Swartz, J. F. “Radiofrequency Endocardial Catheter Ablation of Accessory Atrioventricular Pathway Atrial Insertion Sites”
Circulation
, Vol. 87, no. 2, pgs. 487-499 (February, 1993).
Ablation of a specific location within the heart requires the precise placement of the ablation catheter within the heart. Precise positioning of the ablation catheter is especially difficult because of the physiology of the heart, particularly because the heart continues to beat throughout the ablation procedures. Commonly, the choice of placement of the catheter is determined by a combination of electrophysiological guidance and fluoroscopy (placement of the catheter in relation to known features of the heart which are marked by radiopaque diagnostic catheters which are placed in or at known anatomical structures, such as the coronary sinus, high right atrium and the right ventricle).
Ablation procedures using guiding introducers to guide an ablation catheter to a particular location in the heart for treatment of atrial arrhythmia have been disclosed in U.S. Pat. Nos. 5,497,774, 5,427,119, 5,575,166, 5,640,955, 5,564,440 and 5,628,316. During these procedures, ablation lesions are produced in the heart as an element of the medical procedure.
The energy necessary to ablate cardiac tissue and create a permanent lesion can be provided from a number of different sources. originally direct current was utilized although laser, microwave, ultrasound and forms of direct current (high energy, low energy and fulgutronization procedures) have also been utilized to perform ablation procedures. However, because of problems associated with the use of DC current, radiofrequency (RF) has become the preferred source of energy for ablation procedures. The use of RF energy for ablation has been disclosed, for example, in U.S. Pat. Nos. 4,945,912, 5,209,229, 5,281,218, 5,242,441, 5,246,438, 5,281,213 and 5,293,868. The use of RF energy with an ablation catheter contained within a transseptal sheath for the treatment of W-P-W in the left atrium is disclosed in Swartz, J. F. et al. “Radiofrequency Endocardial Catheter Ablation of Accessory Atrioventricular Pathway Atrial Insertion Sites”
Circulation
Vol. 87, pgs. 487-499 (1993). See also Tracey, C. N. “Radio Frequency Catheter Ablation of Ectopic Atrial Tachycardia Using Paced Activation Sequence Mapping”
J. Am. Coll. Cardiol.
Vol. 21, pgs. 910-917 (1993).
In addition to radio f
Bednarek Michael C.
Stehr Richard E.
Swartz John F.
Cohen Lee
Cox Scott R.
Daig Corporation
Gibson Roy
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