Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2002-04-25
2004-09-28
Manuel, George (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06799072
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to implantable medical devices (IMDs), particularly methods and apparatus for electrically isolating and supporting component sub-assemblies formed of multiple components in volumetrically efficient ways.
BACKGROUND OF THE INVENTION
A wide variety of IMDs are known in the art. Of particular interest are implantable cardioverter-defibrillators (ICDs) that deliver relatively high-energy cardioversion and/or defibrillation shocks to a patient's heart when a malignant tachyarrhythmia, e.g., atrial or ventricular fibrillation, is detected. The shocks are developed by discharge of one or more high voltage electrolytic capacitor that is charged up from an ICD battery. Current ICDs typically possess single or dual chamber pacing capabilities for treating specified chronic or episodic atrial and/or ventricular bradycardia and tachycardia and were referred to previously as pacemaker/cardioverter/defibrillators (PCDs). Earlier developed automatic implantable defibrillators (AIDs) did not have cardioversion or pacing capabilities. For purposes of the present invention ICDs are understood to encompass all such IMDs having at least high voltage cardioversion and/or defibrillation capabilities.
Energy, volume, thickness and mass are critical features in the design of ICD implantable pulse generators (IPGs) that are coupled to the ICD leads to form the completed ICD. The battery(s) and high voltage capacitor(s) used to provide and accumulate the energy required for the cardioversion/defibrillation shocks have historically been relatively bulky and expensive. Presently, ICD IPGs typically have a volume of about 40 to about 60 cc, a thickness of about 13 mm to about 16 mm and a mass of approximately 100 grams.
It is desirable to reduce the volume, thickness and mass of such capacitors and ICD IPGs without reducing deliverable energy. Doing so is beneficial to patient comfort and minimizes complications due to erosion of tissue around the ICD IPG. The size of the ICD IPG is commonly measured in terms of its volume, i.e., displacement. The volume is determined largely by the size and arrangement of the major components enclosed within an IPG “can” or hermetically sealed housing and the size of a connector header mounted to the IPG housing for making electrical connection with ICD leads. The major components within the ICD IPG housing include one or more battery, one or more high voltage capacitor, electronic modules, a telemetry antenna, a large internal discharge resistor (in early ICD IPGs), and any plastic frame or skeleton, spaces or liners supporting these components within the can. Also, the volume of the interconnection wiring between these components can be appreciable.
The high voltage capacitor(s) are among the largest volume components that must be enclosed within the ICD IPG housing. Thus, a great deal of effort has been expended in decreasing the volume of the capacitor(s) to allow for the balanced addition of volume to the battery, thereby increasing longevity of the ICD IPG, or balanced addition of new components, thereby adding functionality to the ICD IPG or to decrease the volume of the ICD IPG housing.
Various types of flat and spiral-wound capacitors are known in the art, some examples of which are described as follows and/or may be found in the patents listed in Table 1 of commonly assigned U.S. Pat. No. 6,006,133. Typically, an electrolytic capacitor is fabricated with a capacitor case enclosing a “valve metal” (e.g., aluminum) anode layer (or “electrode”), a valve metal (e.g. aluminum) cathode layer (or “electrode”), and a Kraft paper or fabric gauze spacer or separator impregnated with a solvent based liquid electrolyte interposed therebetween. The aluminum anode layer is typically fabricated from aluminium foil that is first etched and then “formed” by passage of electrical current through the anode layer to oxidize the etched surfaces so that the aluminium oxide functions as a dielectric layer. The electrolyte comprises an ion producing salt that is dissolved in a solvent and provides ionic electrical conductivity between the cathode layer and the aluminum oxide dielectric layer. The energy of the capacitor is stored in the electromagnetic field generated by opposing electrical charges separated by the aluminum oxide layer disposed on the surface of the anode layer and is proportional to the surface area of the etched aluminum anode layer. Thus, to minimize the overall volume of the capacitor one must maximize anode surface area per unit volume without increasing the capacitor's overall (i.e., external) dimensions. The separator material, anode and cathode layer terminals, internal packaging, electrical interconnections, and alignment features and cathode material further increase the thickness and volume of a capacitor. Consequently, these and other components in a capacitor and the desired capacitance limit the extent to which its physical dimensions may be reduced.
Some ICD IPGs employ commercial photoflash capacitors similar to those described by Troup in “Implantable Cardioverters and Defibrillators,”
Current Problems in Cardiology
, Volume XIV, Number 12, December 1989, Year Book Medical Publishers, Chicago, and as described in U.S. Pat. No. 4,254,775. The electrodes or anode and cathodes are wound into anode and cathode layers separated by separator layers of the spiral. Most commercial photoflash capacitors contain a core of separator paper intended to prevent brittle, highly etched aluminum anode foils from fracturing during winding of the anode, cathode, and separator layers into a coiled configuration. The cylindrical shape and paper core of commercial photoflash capacitors limits the volumetric packaging efficiency and thickness of an ICD IPG housing made using same.
The early ICD IPG depicted in the '778 patent is much larger in volume and weight than current ICD IPGs due to use of such large cylindrical capacitors as well as large volume batteries, large discrete electrical components, circuit boards and the supporting skeleton for these components. The capacitors are supported and electrically isolated from one another and the batteries and the electrical circuitry by end cups and spacers and are cushioned from the housing itself by electrical insulating tape wound about the capacitors and batteries. An appreciable amount of unfilled space appears to remain in the ICD IPG housing. Moreover, tedious hand assembly appears to have been necessary to assemble these components. Nevertheless, similar component arrangements and assembly techniques have continued to be used until recently with more compact integrated circuit modules as evidenced by the ICD IPG depicted in U.S. Pat. Nos. 5,741,313, 5,749,910, 5,814,090, and 6,026,325, for example.
Recently developed ICD IPGs employ one or more flat or “prismatic”, high voltage, electrolytic capacitor to overcome some of the packaging and volume disadvantages associated with cylindrical photoflash capacitors. Flat aluminum electrolytic capacitors for use in ICD IPGs have been disclosed, e.g., those improvements described in “High Energy Density Capacitors for Implantable Defibrillators” presented by P. Lunsmann and D. MacFarlane at
CARTS
96: 16
th Capacitor and Resistor Technology Symposium,
11-15 March 1996, and at
CARTS
-
EUROPE
96: 10
th European Passive Components Symposium.,
7-11 October 1996, pp. 35-39. Further features of flat electrolytic capacitors for use in ICD IPGs are disclosed in the above-referenced '133 patent and in U.S. Pat. Nos. 4,942,501; 5,086,374; 5,131,388; 5,146,391; 5,153,820; 5,522,851, 5,562,801; 5,628,801; and 5,748,439, all issued to MacFarlane et al. For example, U.S. Pat. Nos. 5,131,388 and 5,522,851 disclose a flat aluminium electrolytic capacitor having a plurality of stacked capacitor layers each comprising an “electrode stack sub-assembly”. Each capacitor layer contains one or more anode sheet forming an anode layer having an anode tab, a cathode sheet or layer having a cathode tab and a separator for separati
Breyen Mark D.
May Steven J.
Miltich Thomas P.
Norton John D.
Ries Andrew J.
Manuel George
Medtronic Inc.
Soldner Michael C.
Wolde-Michael Girma
LandOfFree
Electrically insulated component sub-assemblies of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrically insulated component sub-assemblies of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrically insulated component sub-assemblies of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3232190