Since the early 1980s, thousands of patients prone to irregular and sometimes life threatening heart rhythms have had miniature defibrillators and cardioverters implanted in their bodies, typically in the upper chest area above their hearts. These devices detect onset of abnormal heart rhythms and automatically apply corrective electrical therapy, specifically one or more 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 defibrillator or cardioverter includes a set of 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.
In many instances, the capacitor takes the form of a flat aluminum electrolytic capacitor. This type of capacitor generally includes a stack of flat capacitor elements, with each element including one or more paper separators between two sheets of aluminum foil. One of the foils serves as the anode of the capacitor element, and the other serves as the cathode. Each anode foil in the stack, and each cathode foil in the stack, is interconnected to the other anodes and cathodes respectively. Connecting the anodes and cathodes provides a total capacitance equal to the sum of the capacitances of all the capacitor elements. After being connected, the respective anodes and cathodes are connected to terminals for being coupled to circuitry outside the capacitor case.
Since defibrillators and cardioverters are typically implanted in the left region of the chest or in the abdomen, a smaller size device, which is still capable of delivering the required level of electrical energy, is desirable.
Accordingly, there is a need to provide a compact capacitor capable of providing the required pulse of energy for use within the device. Furthermore, there is a need to provide methods of manufacturing a capacitor and structures within the capacitor that provide greater process control, less expensive manufacturing, and provide for a design efficiently utilizing space within the capacitor case.