Subcutaneous insertable electrocardiography monitor
Long-term electrocardiographic and physiological monitoring over a period lasting up to several years in duration can be provided through a continuously-recording subcutaneous insertable cardiac monitor (ICM). The sensing circuitry and the physical layout of the electrodes are specifically optimized to capture electrical signals from the propagation of low amplitude, relatively low frequency content cardiac action potentials, particularly the P-waves that are generated during atrial activation. The ICM is intended to be implanted centrally and positioned axially and slightly to either the left or right of the sternal midline in the parasternal region of the chest, with at least one of the ECG sensing electrodes of the ICM being disposed for being positioned in a region overlying the sternum or adjacent to the sternum and the other of the electrodes also being disposed for being positioned over the sternum or adjacent to the sternum of on the patient's chest.
1. A subcutaneous insertable electrocardiography (ECG) monitor, comprising:
an implantable housing comprised of a biocompatible material that is suitable for implantation within a living body in at least one of the sternal midline and the parasternal region of the chest of the body;
at least a pair of ECG sensing electrodes provided on a ventral surface and on opposite ends of the implantable housing operatively placed to facilitate sensing in closest proximity to the low amplitude, low frequency content cardiac action potentials that are generated during atrial activation, one of the electrodes being disposed for being positioned in at least one a region overlying the inferior sternum and the parasternal region of a patient's chest when the housing has been implanted, the other of the electrodes being disposed for being positioned in at least one of the superior sternal region and the parasternal region of the patient's chest when the housing has been implanted;
an extension formed on a distal end of the implantable housing;
at least one additional ECG sensing electrode provided on a distal end of the extension, the at least one additional ECG sensing electrode comprising a pair of crescent-shaped electrodes surrounding a central oval electrode that can be programmatically combined by the microcontroller to form a single electrode; and
electronic circuitry provided within the housing assembly comprising the low power microcontroller operable to execute under modular micro program control as specified in firmware, an ECG front end circuit interfaced to the microcontroller and configured to capture the cardiac action potentials sensed by the pair of ECG sensing electrodes which are output as ECG signals, and non-volatile memory electrically interfaced with the microcontroller and operable to continuously store samples of the ECG signals, wherein the firmware comprises programmatic selection of one or more pairings of the ECG sensing electrodes.
2. A monitor in accordance with claim 1 , wherein the implantable housing is configured to be positioned between the second and the sixth rib of the body.
3. A monitor in accordance with claim 1 , wherein the biocompatible material comprises at least one of titanium and stainless steel.
4. A monitor in accordance with claim 1 , further comprising:
a wireless antenna positioned to wrap around an internal periphery of the implantable housing.
5. A monitor in accordance with claim 1 , further comprising:
at least one further ECG sensing electrode further provided to wraparound an end of the implantable housing circumferentially about one of the pair of ECG sensing electrodes, continue around the sides and ends of the implantable housing, and over the planar surface of the implantable housing.
6. A monitor in accordance with claim 5 , wherein one of the ECG sensing electrodes and the at least one ECG sensing electrode are logically combined to form a single virtual electrode.
7. A monitor in accordance with claim 5 , wherein the at least one further ECG sensing electrode is electrically insulated from at least one of the ECG sensing electrodes.
8. A monitor in accordance with claim 1 , wherein the pair of the ECG sensing electrodes are operatively coupled to the implantable housing.
9. A rectangular subcutaneous insertable electrocardiography monitor, comprising:
a hermetically sealed implantable housing defining a rectangular shape with rounded edges and comprised of a biocompatible material that is suitable for implantation within a living body of a patient in at least one of the sternal midline and the parasternal region of the chest of the body;
at least a pair of ECG sensing electrodes provided on a ventral surface and on opposite ends of the implantable housing operatively placed to facilitate sensing in closest proximity to the low amplitude, low frequency content cardiac action potentials that are generated during atrial activation, one of the electrodes being disposed for being positioned in at least one a region overlying the inferior sternum and the parasternal region of a patient's chest when the housing has been implanted, the other of the electrodes being disposed for being positioned in at least one of the superior sternal region and the parasternal region of the patient's chest when the housing has been implanted;
an extension formed on a distal end of the implantable housing and tapering from a proximal end of the extension and towards a distal end of the extension, the distal end of the tapered extension comprising a substantially cylindrical structure;
at least one additional ECG sensing electrode provided on a distal end of the cylindrical structure, the at least one additional ECG sensing electrode comprising a pair of crescent-shaped electrodes surrounding a central oval electrode that can be programmatically combined by a low-power microcontroller to form a single electrode; and
electronic circuitry provided within the housing assembly comprising the low power microcontroller operable to execute under modular micro program control as specified in firmware, an ECG front end circuit interfaced to the microcontroller and configured to capture the cardiac action potentials sensed by the pair of ECG sensing electrodes which are output as ECG signals, and non-volatile memory electrically interfaced with the microcontroller and operable to continuously store samples of the ECG signals, wherein the firmware comprises programmatic selection of one or more pairings of the ECG sensing electrodes.
10. A monitor in accordance with claim 9 , wherein the implantable housing is configured to be positioned between the second and the sixth rib of the body.
11. A monitor in accordance with claim 9 , wherein the biocompatible material comprises at least one of titanium and stainless steel.
12. A monitor in accordance with claim 9 , further comprising:
a wireless antenna positioned to wrap around an internal periphery of the implantable housing.
13. A monitor in accordance with claim 9 , further comprising:
at least one further ECG sensing electrode further provided to wraparound an end of the implantable housing circumferentially about one of the pair of ECG sensing electrodes, continue around the sides and ends of the implantable housing, and over the planar surface of the implantable housing.
14. A monitor in accordance with claim 13 , wherein one of the ECG sensing electrodes and the at least one ECG sensing electrode are logically combined to form a single virtual electrode.
15. A monitor in accordance with claim 13 , wherein the at least one further ECG sensing electrode is electrically insulated from at least one of the ECG sensing electrodes.
16. A monitor in accordance with claim 9 , wherein the pair of the ECG sensing electrodes are operatively coupled to the implantable housing.