IMPLANTABLE HEART MONITORS
HAVING CAPACITORS WITH ENDCAP
CROSS-REFERENCE TO RELATED 5
This application is a division of U.S. patent application Ser. No. 09/706,515, filed on Nov. 3, 2000 now U.S. Pat. No. 6,684,102, the specification of which is incorporated herein 10 by reference.
This application is related to commonly assigned application Ser. No. 09/706,447, filed on Nov. 3, 2000, entitled FLAT CAPACITOR FOR AN IMPLANTABLE MEDICAL DEVICE, which is incorporated herein by reference in its 15 entirety.
FIELD OF THE INVENTION
The present invention concerns capacitors, particularly 20 wet-electrolytic capacitors used in implantable medical devices, such as implantable defibrillators, cardioverters, and pacemakers.
The present invention concerns implantable heart monitors, such as defibrillators and cardioverters, particularly 25 structures and methods for capacitors in such devices.
Since the early 1980s, thousands of patients prone to 30 irregular and sometimes life-threatening heart rhythms have had miniature heart monitors, particularly defibrillators and cardioverters, implanted in their bodies. These devices detect onset of abnormal heart rhythms and automatically apply corrective electrical therapy, specifically one or more 35 bursts of electric current, to hearts. When the bursts of electric current are properly sized and timed, they restore normal heart function without human intervention, sparing patients considerable discomfort and often saving their lives.
The typical defibrillator or cardioverter includes a set of 40 electrical leads, which extend from a sealed housing into the walls of a heart after implantation. Within the housing are a battery for supplying power, monitoring circuitry for detecting abnormal heart rhythms, and a capacitor for delivering bursts of electric current through the leads to the heart. 45
The capacitor is often times a cylindrical aluminum wet electrolytic capacitor. This type capacitor usually includes stacked strips of aluminum foil and paper rolled, or wound, to form a cylindrical structure which is housed in a round tubular aluminum can. The can has an integral aluminum 50 bottom end and an open top end sealed with a non-conductive flat circular lid, known as a header. Two terminals extend from the header, each connected to one of the rolled aluminum foils.
One problem the inventors recognized with these cylin- 55 drical capacitors is the overall height of the capacitor, measured from the bottom of the tubular aluminum can to the top of the terminals extending from the header. In particular, the terminals are rigid metal structures that generally require clearance space to avoid contacting other 60 components within the housing of the implantable devices. Providing this clearance space ultimately increases the size of implantable devices beyond that otherwise necessary. Another related problem is that the diameter of the header has a practical minimum of about twelve millimeters and 65 thus restricts how small capacitors and thus implantable devices can be made. Accordingly, the inventors identified a
need to develop space-efficient techniques and structures for providing terminals on electrolytic capacitors.
SUMMARY OF THE INVENTION
To address this and other needs, the inventors devised wet electrolytic capacitors with unique connection structures. One exemplary capacitor includes two conductive endcaps at opposite ends of its capacitive element, instead of two upright terminals at one end, thereby allowing reduction in the height or volume of the capacitor and/or increases in the dimensions of other components, such as aluminum foils. Another exemplary capacitor includes two feedthrough assemblies at opposite ends of the wound capacitive element to also facilitate reduction in the height or volume of the capacitor or increasing its energy-storage density.
Other aspects of the invention include an implantable heart monitor, such as a pacemaker, defibrillator, congestiveheart-failure (CHF) device, or cardioverter defibrillator, that incorporates one or more capacitors with the unique connection structures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an exemplary cylindrical wet electrolytic capacitor 100 embodying teachings of the present invention.
FIG. 2 is a cross-sectional view of capacitor 100 in FIG. 1 taken along line 2—2.
FIG. 3 is a perspective view of an exemplary cylindrical wet electrolytic capacitor 300 embodying teachings of the present invention.
FIG. 4 is a cross-sectional view of capacitor 300 taken along line 4—4 in FIG. 3.
FIG. 5 is a block diagram of an exemplary implantable heart monitor 500 which includes one or more electrolytic capacitors 532 embodying teachings of the present invention.
DESCRIPTION OF THE PREFERRED
The following detailed description, which references and incorporates FIGS. 1-5, describes and illustrates one or more specific embodiments of the invention. These embodiments, offered not to limit but only to exemplify and teach, are shown and described in sufficient detail to enable those skilled in the art to implement or practice the invention. Thus, where appropriate to avoid obscuring the invention, the description may omit certain information known to those of skill in the art.
FIG. 1 shows a perspective view of an exemplary cylindrical wet electrolytic capacitor 100 which embodies teachings of the present invention. And, FIG. 2 shows a crosssection of capacitor 100 taken along line 2—2.
In particular, capacitor 100 includes a cylindrical or tubular section 102, cylindrical endcaps 104 and 106, a cylindrical capacitive element 108, anode tab 110, and cathode tab 112. Tubular section 102, which comprises a non-conductive material, such as a ceramic, a polymer, or a plastic, in the exemplary embodiment, at least partially encloses a central portion of wound or rolled capacitive element 108. To fully enclose capacitive element 108, section 102 has two opposing ends 102a and 1026 that mate respectively with conductive end caps 104 and 106.
Endcaps 104 and 106, which are exemplarily formed of diecast (deep drawn) or machined aluminum or other con