Subcutaneous cardiac stimulator with small contact surface electrodes
A subcutaneous cardiac device includes two electrodes and a stimulator that generates a pulse to the electrodes. The electrodes are implanted between the skin and the rib cage of the patient and are adapted to generate an electric field corresponding to the pulse, the electric field having a substantially uniform voltage gradient as it passes through the heart. The shapes, sizes, positions and structures of the electrodes are selected to optimize the voltage gradient of the electric field, and to minimize the energy dissipated by the electric field outside the heart. More specifically, the electrodes have contact surfaces that contact the patient tissues, said contact surfaces having a total contact area of less than 100 cm 2 . In one embodiment, one or both electrodes are physically separated from the stimulator. In another embodiment a unitary housing holds the both electrodes and the stimulator. Sensor circuitry may also includes in the stimulator for detecting intrinsic cardiac activity through the same electrodes.
1. A cardiac device comprising:
an implantable housing having an external surface;
first and second subcutaneous electrodes;
at least one lead connecting said housing to at least one of said first and second subcutaneous electrodes; and
a cardiac stimulator disposed in said implantable housing, the cardiac stimulator electrically connected to said first and second subcutaneous electrodes and adapted to apply electrical pulses between said first and second subcutaneous electrodes, wherein at least one of said first and second subcutaneous electrodes is formed on the external surface of the housing, said first and second subcutaneous electrodes sized and configured to generate a vector over a substantial portion of the heart of a patient from their subcutaneous positions when said first and second electrodes are implanted at respective first and second subcutaneous positions within the patient, and wherein said first and second electrodes have respective contact surfaces that, in implantation, are in electrical contact with tissues, said contact surfaces providing a combined total surface area of less than 100 cm 2 .
2. A cardiac device comprising:
an implantable housing having an external surface;
a first subcutaneous electrode having a first electrode center and a second subcutaneous electrode having a second electrode center; and
a cardiac stimulator disposed in said implantable housing, the cardiac stimulator electrically connected to said first and second subcutaneous electrodes and adapted to selectively apply electrical pulses between said first and second subcutaneous electrodes;
said first subcutaneous electrode being sized and adapted to be implanted subcutaneously in the vicinity of the sternum with said first electrode center being disposed on a first line perpendicular to the central axis through the patient and said second subcutaneous electrode being sized and adapted to be implanted subcutaneously on the left side of the patient with said second electrode center being disposed on a second line perpendicular to said central axis, said first and second subcutaneous electrodes sized and configured to provide cardioversion/defibrillation energy in connection with the cardiac stimulator without additional electrodes;
wherein at least one of said first and second subcutaneous electrodes is formed on the external surface of said housing, wherein said first and second subcutaneous electrodes have a combined total surface area of less than 100 cm 2 , and wherein said first and second lines define a predetermined angle therebetween.