Subcutaneous P-Wave Centric Insertable Cardiac Monitor For Long Term Electrocardiographic Monitoring

Abstract

A P-wave centric subcutaneous insertable cardiac monitor for use in performing long term electrocardiographic (ECG) monitoring is disclosed. An implantable housing made of a biocompatible material is provided. At least one pair of ECG sensing electrodes is provided on a ventral (or dorsal) 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. Electronic circuitry is provided within the housing assembly including a 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.

1 . A P-wave centric subcutaneous insertable cardiac monitor (ICM) for use in performing long term electrocardiographic (ECG) monitoring, comprising:
 an implantable housing comprised of a biocompatible material that is suitable for implantation within a living body;   at least three ECG sensing electrodes provided on a ventral surface and on opposite ends of the implantable housing with two of the ECG sensing electrodes provided on opposite ends of the implantable housing, each of the ECG sensing electrodes operatively placed to facilitate sensing in closest proximity to the low amplitude, low frequency content cardiac action potentials of P-wave signals that are generated during atrial activation; and   electronic circuitry provided within the implantable housing comprising:
 a low power microcontroller operable to execute under modular micro program control as specified in firmware, 
 programmatic selection of at least one pairing of the ECG sensing electrodes to facilitate the sensing of the cardiac action potentials of the P-wave signals based on a patient's physiology, 
 an ECG front end circuit interfaced to the microcontroller and configured to specifically capture the cardiac action potentials of the P-wave signals sensed by the pairing of the ECG sensing electrodes, and 
   non-volatile memory electrically interfaced with the microcontroller and operable to continuously store samples of the cardiac action potentials of the P-wave signals.   
     
     
         2 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , further comprising:
 at least one of the ECG sensing electrodes further provided on the ventral surface of the implantable housing between the ECG sensing electrodes provided on the opposite ends of the implantable housing.   
     
     
         3 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , further comprising:
 at least one of the ECG sensing electrodes further provided to wraparound an end of the implantable housing circumferentially about the ECG sensing electrodes, electrodes provided on the opposite ends of the implantable housing, continue around the sides and ends of the implantable housing, and over the planar surface of the implantable housing.   
     
     
         4 . A subcutaneous insertable cardiac monitor in accordance with  claim 3 , further comprising:
 a periphery interposed between the at least one ECG sensing electrode and the ECG sensing electrode about which the at least one sensing electrode is circumferentially provided,   wherein the firmware comprises programmatic control over the electrically insulative properties of the periphery.   
     
     
         5 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , wherein at least one of the ECG sensing electrodes is dissimilar from the other ECG sensing electrode with respect to one or more of electrode size, shape, surface area, and placement. 
     
     
         6 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , wherein the ECG front end circuit further comprises a driven reference operable to reduce common mode, power supply and system noise and optimize sensing of the cardiac action potentials of the P-wave signals. 
     
     
         7 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , the electronic circuitry further comprising:
 a transceiver operable to wirelessly interface to an external device through which to at least one of provide the samples of the cardiac action potentials of the P-wave signals from the non-volatile memory and receive modular micro program control into the firmware.   
     
     
         8 . A subcutaneous insertable cardiac monitor in accordance with  claim 7 , wherein the firmware comprises instructions operable to program the microcontroller to perform the steps comprising:
 monitoring the cardiac action potentials of the P-wave signals sensed by the ECG sensing electrodes for arrhythmias of selected medical concern and wirelessly sending an alert via the transceiver upon the occurrence of one of the arrhythmias of selected medical concern;   executing heuristics to actively identify or narrow down a pattern or underlying cause of sporadic cardiac conditions and wirelessly sending an alert via the transceiver upon the occurrence of one of the pattern and the underlying cause;   executing programming tailored to the monitoring and medical diagnostic needs of at least one of a specific patient, patient group or general patient population of conditions or symptoms of medical concern and wirelessly sending an alert via the transceiver upon the occurrence of one of the conditions or symptoms of medical concern.   
     
     
         9 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , further comprising:
 a patient-interfaceable component selected from the group comprising an external tactile feedback device that wirelessly interfaces to the ICM through the transceiver and an external buzzer implemented as part of the external tactile feedback device or as a separate wirelessly-interfaceable component.   
     
     
         10 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , the pairing of the ECG sensing electrodes further comprising:
 an electrode configuration defining an electrode-to-electrode spacing of between 20 mm to 200 mm.   
     
     
         11 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , the pairing of the ECG sensing electrodes further comprising:
 an electrode shape comprising a round disc from 2 mm to 10 mm in diameter.   
     
     
         12 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , the pairing of the ECG sensing electrodes further comprising:
 an electrode shape selected from the group comprising circumferentially-shaped and asymmetrically-shaped electrodes.   
     
     
         13 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , wherein the implantable housing comprises a hermetically sealed implantable housing defining a rectangular shape with rounded edges. 
     
     
         14 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , wherein the implantable housing assembly comprises a hermetically sealed implantable housing defining a rectangular shape with rounded edges with a tapered extension that is terminated on the distal end with one of the ECG sensing electrodes. 
     
     
         15 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , wherein the power source comprises a long life direct current power cell comprised within the implantable housing. 
     
     
         16 . A subcutaneous insertable cardiac monitor in accordance with  claim 1 , further comprising:
 a physiology sensor comprised within the implantable housing and electrically coupled to the circuitry with the physiological sensor operable to sense physiology of the living body; and   the non-volatile memory further operable to store samples of the physiology sensed by the physiology sensor.   
     
     
         17 . A subcutaneous insertable cardiac monitor in accordance with  claim 16 , wherein the physiology sensor is selected from the group consisting of an SpO 2  sensor, a blood pressure sensor, a temperature sensor, a respiratory rate sensor, a glucose sensor, an air flow sensor, and a volumetric pressure sensor.