Implantable cardiac arrest monitor and alarm system

#1. Field of the Invention

#This invention relates to a cardiac arrest monitor and alarm system that continuously monitors a patient's heart and detects a deviation from a normal heart electrical activity to alert bystanders and activate a communication link to transmit an alarm and an electrocardiographic signal to a remote transceiver, which permits automatic geographical location of the patient.

#2. Description of Related Art

#The drawings show different features of a cardiac arrest monitor and alarm system, according to preferred embodiments of this invention, wherein:

#FIG. 1 is a schematic drawing of a patient showing placement of the implantable medical device subcutaneously, having a plurality of electrodes and a microdevice positioned with respect to the patient's heart to form an orthogonal lead configuration, according to one preferred embodiment of this invention;

#FIG. 1A is a schematic drawing of a patient showing placement of the implantable medical device subcutaneously, having a microdevice and a plurality of electrodes located on an exterior surface of the microdevice and positioned with respect to the patient's heart to form an orthogonal lead configuration, according to one preferred embodiment of this invention;

#As shown in FIGS. 1-3, in one preferred embodiment of the invention, a cardiac arrest monitor and alarm system 10 comprises an implantable or subcutaneous medical device 15. In one preferred embodiment of this invention, medical device 15 is chronically and completely implanted within a patient's body. Medical device 15 is implanted subcutaneously to sample electrocardiographic (“ECG”) signals to continuously monitor and analyze the ECG signals to detect normal cardiac electrical activity and automatically initiate communication with an external communicating device to warn the patient when the results of the analysis call for medical intervention.

#In one preferred embodiment of this invention, medical device 15 comprises at least three subcutaneous electrodes 22, 24, 26 positioned with respect to a heart organ, for example a human patient's heart to form a subcutaneous orthogonal lead configuration or system 31 to continuously monitor the ECG signals of the patient's heart. In order to obtain an ECG signal of high quality, suitable for processing in order to generate an alarm automatically, subcutaneous electrodes 22, 24, 26 are preferably spaced at least 4.0 centimeters apart from each other and positioned in the precordial region of the chest of the patient. Lead wires 28 are tunneled under the skin between electrode 22,24,26 and an implanted microdevice 30. Further, electrodes 22, 24, 26 are positioned at the corners of a 2-dimensional or, preferably, 3-dimensional parallelepiped to group electrodes 22, 24, 26 in pairs such that each pair forms with other pairs a set of orthogonal electrocardiographic leads.

#Representation of the electrical nature of the heart as a current dipole is a well known concept in electrocardiography. In this concept, the heart is modeled as a single source of current and a sink for that current, wherein the source and sink are closely spaced points within the chest in the region occupied by the heart. It is apparent to those skilled in the art that a current dipole immersed in a conducting medium such as the body will create voltages throughout the body and upon its surface that are ideally measured by three pairs of electrodes whose axes, the straight lines joining the two electrodes of each pair, are mutually perpendicular to each other. This is the basis of that branch of electrocardiolography called “vectorcardiography.” The three leads, such as connections of electrodes, used in vectorcardiography are called “orthogonal leads” because they measure the three perpendicular components of the cardiac dipolar source: vertical; horizontal anteroposterior; and horizontal transverse. In principle, from these three components the cardiac source can be accurately reconstructed. All the information needed to describe the heart's dipolar electrical activity is contained in these three leads. A reduced set of two such leads can describe the heart's electrical activity in two dimensions, for example, in a frontal plane. Depending on the direction of electrical activation across the heart, the three components of the cardiac dipole will vary in relative magnitude, but the composite or vector magnitude will not. In particular, the vector magnitude of the three signals from the orthogonal lead set will, during a dangerous rhythm, be similar to that obtained during normal rhythm, since the vector magnitude is independent of the source and direction of cardiac activation.