Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator
Reexamination Certificate
2001-10-12
2004-04-06
Schaetzle, Kennedy (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical energy applicator
C607S129000, C600S391000
Reexamination Certificate
active
06718212
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to medical electrical leads adapted to be implanted within the body, and particularly to such leads having at least one distal electrode affixed at a site of a body organ, particularly the epicardium of the heart, employing a light-activated adhesive fixation and methods and systems for accessing the site, applying the distal electrode to the site and activating the light-activated adhesive.
BACKGROUND OF THE INVENTION
In the field of cardiac stimulation, cardiac pacing leads having bipolar and unipolar pace/sense electrodes have long been used in conjunction with implantable pulse generators (IPGs) to conduct pacing pulses or cardioversion/defibrillation shocks generated by the IPG to a site of the heart and cardiac signals from the site to the IPG. Cardioversion/defibrillation leads and pacing leads are typically provided with a passive fixation or an active fixation mechanism at the lead body distal end that is passively or actively engaged with cardiac tissue to anchor a distal tip electrode at a desired site in or on the heart. Passive fixation generally involves an atraumatic fixation lodging the distal electrode against the endocardium or within a coronary blood vessel. Positive or active fixation generally involves a more traumatic penetration of a fixation mechanism into the myocardium from an endocardial or epicardial surface, and the active fixation mechanism commonly comprises a distal electrode.
Endocardial pacing and cardioversion/defibrillation leads having either active fixation or passive fixation mechanisms are implanted by a transvenous route into a heart chamber to locate the distal electrode(s) at a selected site in the heart chamber where an active or passive fixation mechanism is deployed to maintain the electrode affixed at the site. Epicardial leads are implanted by exposure of the epicardium of the heart typically through a limited subxiphoid approach or a more extensive surgical exposure made to perform other corrective procedures. The distal end of the epicardial lead formed with one or two electrodes and an active fixation mechanism supported by an electrode head is affixed to the epicardium. Typically, the active fixation mechanism comprises the single electrode or one of the bipolar electrodes, but can be separate and electrically isolated from the electrodes.
Epicardial pacing and cardioversion/defibrillation leads were the first to be implanted widely, because endocardial leads lacked effective active or passive fixation mechanisms and relied upon relatively stiff lead bodies that cause perforations and dislodgement of the distal electrode(s). Initially, access to the epicardium was made by a thoracotomy or median sternotomy and excision through or removal of the pericardial sac. Typically, pace/sense electrodes penetrated the myocardium and were sutured against the epicardium to maintain fixation. The large patch electrodes of cardioversion/defibrillation electrodes were sutured to the epicardium.
Many improvements were made in epicardial pace/sense leads to minimize surgical trauma of accessing the epicardium and to avoid the need to suture the electrode to the epicardium. Thus, active fixation mechanisms of epicardial pacing leads typically comprise a tissue penetrating, self-affixing mechanism extending away from a support or base or plate of the electrode head. The fixation mechanism is forced into the myocardium typically employing an introduction tool engaging the electrode head until it is fully seated within the endocardium and the plate bears against the epicardium. The plate is typically formed with a tissue ingrowth encouraging fabric or lattice, whereby tissue ingrowth about the plate assists in chronic anchoring to the heart.
Such active fixation mechanisms include a rigid helix having a sharpened tip that is coupled with a lead conductor within the electrode head and extends at a right angle from the plate as typified by the MEDTRONIC® Model 6917 lead and the leads disclosed in commonly assigned U.S. Pat. Nos. 3,737,579 and 4,010,758. Other variations of such epicardial screw-in leads include multiple co-axial and intertwined helixes or a helix axially surrounding a pin extending coaxially with the helix axis from the electrode head. During implantation, the lead body and electrode head are mounted to an elongated tool, and the sharpened tip of the helix is advanced through the incision to perforate the epicardium. The tool and lead are rotated to screw the helix in until the plate abuts the epicardium, and the electrode head is detached from the tool.
A further epicardial screw-in lead is disclosed in commonly assigned U.S. Pat. No. 4,357,946 wherein the helix is mounted to a gear mechanism within the electrode head. The helix can itself be rotated to screw into the myocardium without rotating or moving the electrode head by a rotation of a removable stylet extending through the length of the lead body and engaging the gear mechanism. Both unipolar and bipolar embodiments are disclosed.
A further active fixation, unipolar, epicardial lead comprises the MEDTRONIC® Model 6951 lead disclosed in commonly assigned U.S. Pat. No. 4,313,448. The active fixation mechanism comprises forward facing barbed electrode having the tip at a predetermined angle with relation to the shank of the electrode and with respect to a flexible base pad or plate of the electrode head. The plate has a substantially centered hole and a plurality of outer holes for fibrous ingrowth, and the shank of the electrode extends out through the substantially centered hole. The barbed electrode is pushed into the myocardial tissue to the point where the base pad engages against the epicardium thereby indicating full implantation within the myocardium. During implantation, a stiffening stylet is employed to stiffen the lead body and a forceps is employed to grasp the electrode head to push the barb into the myocardium.
Over the years, endocardial pacing leads were improved by incorporation of effective active and passive fixation mechanisms, and development of simplified introduction procedures, stronger, more flexible, smaller diameter, and more reliable lead bodies enabling fixation of pace/sense electrodes in the right atrium, right ventricle and within the coronary sinus and great vein descending from the coronary sinus. Endocardial cardioversion/defibrillation leads were also developed incorporating these improved features of pacing leads and elongated cardioversion/defibrillation electrodes for implantation in the same locations. Thus, endocardial pacing and cardioversion/defibrillation leads have largely supplanted epicardial pacing and cardioversion/defibrillation leads in clinical practice. Epicardial pacing leads are still medically indicated for many patients, particularly children. Although the various indications for epicardial lead fixation in pediatric patients are numerous, some common factors include small stature, congenital heart defects with residual or potential right to left shunting or single ventricle hearts, or lack of venous access to the chamber requiring pacing.
Moreover, endocardial pacing and cardioversion/defibrillation leads cannot be implanted within the left heart chambers, due to risk of embolized thrombus. In particular, blood flows through the right heart chambers (atrium and ventricle), through the lungs, through the left heart chambers (atrium and ventricle) and then through the rest of the body, including the brain, before returning again to the right atrium. Implanted objects, however, often cause minor blood clots and thrombus to form in the blood. These may, on occasion, dislodge and be released into the bloodstream. Because the blood circulates directly from the left atrium and ventricle to the brain, any clots, however minor, could have serious consequences if they were to reach the brain, e.g. a stroke. In contrast, any clots released from an object implanted in the right side of the heart would simply travel to the lungs, where they would lodge, usually without serious
Parry Andrew J.
Williams Terrell M.
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