# US 9,433,793 B2 · System and method for accurately detecting cardiac events using multi-threshold processing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,433,793 B2 - Document ID: US9433793B2 - Status: Granted - Kind: B2 - Application number: 12/264,131 - Filed: 2008-11-03 - Published: 2010-05-06 - Granted: 2016-09-06 - Earliest claimed: 2008-11-03 - Assignees: Pacesetter, Inc. - Applicants: Rupinder Bharmi; Jeffery D. Snell - Inventors: Rupinder Bharmi; Jeffery D. Snell - Web page: https://patentgrep.com/patent/US9433793B2 ## CPC - A61N 1/3704: {Circuits specially adapted therefor, e.g. for sensitivity control} - A61B 5/346: Analysis of electrocardiograms - A61B 5/35: by template matching - A61B 5/352: Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval - A61N: ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY (measurement of bioelectric currents A61B; surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body A61B18/00; anaesthetic apparatus in general A61M; incandescent lamps H01K; infrared radiators for heating H05B) - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract A system and method provide precise detection of the time of occurrence of a cardiac event of a heart. The method comprises the steps of sensing electrical activity of the heart to generate an electrogram of the heart and applying the electrogram to an event detector having a plurality of spaced apart thresholds. The thresholds are selected such that the electrogram has an amplitude for crossing at least one of the thresholds. The method further comprises determining a characteristic identifying feature of the electrogram at each threshold crossing of the electrogram, comparing the determined characteristic identifying features to an electrogram template, and identifying the time of occurrence of the cardiac event based upon the comparison. ## Claims ### Claim 1 A method of detecting the time of occurrence of a cardiac event of a heart, the method comprising: sensing electrical activity of the heart to generate an electrogram of the heart; applying the electrogram to an event detector having a plurality of thresholds, the electrogram having an amplitude for crossing a plurality of the thresholds; determining a characteristic identifying feature of the electrogram at each of the plurality of threshold crossings of the electrogram; comparing the determined characteristic identifying features to an electrogram template for each of the plurality of threshold crossings; and identifying the time of occurrence of the cardiac event based upon the comparison. ### Claim 2 (depends on 1) The method of claim 1, wherein the characteristic identifying feature is electrogram slope. ### Claim 3 (depends on 1) The method of claim 1, wherein the characteristic identifying feature is electrogram amplitude. ### Claim 4 (depends on 1) The method of claim 1, wherein the characteristic identifying feature is time of threshold crossing. ### Claim 5 (depends on 1) The method of claim 1, wherein the step of identifying the time of occurrence of the cardiac event based upon the comparison comprises the steps of assigning a point on the electrogram template as a fiducial point, aligning the electrogram with the electrogram template and locating a point on the electrogram corresponding to the fiducial point on the electrogram template. ### Claim 6 (depends on 1) The method of claim 1, wherein the electrogram is a portion of a cardiac cycle. ### Claim 7 (depends on 6) The method of claim 6, further comprising the steps of defining a recording window and recording the electrogram during the recording window. ### Claim 8 (depends on 7) The method of claim 7, comprising the further step of initiating the recording window based upon real time detection of the cardiac event. ### Claim 9 A system that detects the time of occurrence of a cardiac event of a heart, the system comprising: a sensing circuit that senses electrical activity of the heart to generate an electrogram of the heart; an event detector that acts upon the electrogram, the event detector having a plurality of thresholds, the electrogram having an amplitude for crossing a plurality of the thresholds; and a processor that stores an electrogram template and determines a characteristic identifying feature of the electrogram at each of the plurality of threshold crossings of the electrogram, compares the determined characteristic identifying features to the electrogram template, and identifies the time of occurrence of the cardiac event based upon the comparison. ### Claim 10 (depends on 9) The system of claim 9, wherein the characteristic identifying feature is electrogram slope. ### Claim 11 (depends on 9) The system of claim 9, wherein the characteristic identifying feature is electrogram amplitude. ### Claim 12 (depends on 9) The system of claim 9, wherein the characteristic identifying feature is time of threshold crossing. ### Claim 13 (depends on 9) The system of claim 9, wherein the processer is programmed to assign a point on the electrogram template as a fiducial point, align the electrogram with the electrogram template based upon the characteristic identifying features and locate a point on the electrogram corresponding to the fiducial point on the electrogram template. ### Claim 14 (depends on 9) The system of claim 9, wherein the cardiac event is an R wave. ### Claim 15 (depends on 9) The system of claim 9, wherein the electrogram is a portion of a cardiac cycle. ### Claim 16 (depends on 15) The system of claim 15, wherein the processor is further programmed to define a recording window and to record the electrogram during the recording window. ### Claim 17 (depends on 16) The system of claim 16, wherein the processor is further programmed to initiate the recording window based upon a real time detection of the cardiac event. ### Claim 18 In an implantable cardiac device, a system that detects the time of occurrence of a cardiac event of a heart comprising: a sensing circuit that senses electrical activity of the heart to generate an electrogram of the heart; an event detector that acts upon the electrogram, the event detector having a plurality of thresholds, the electrogram having an amplitude for crossing a plurality of the thresholds; and a processor that stores an electrogram template and determines a characteristic identifying feature of the electrogram at each of the plurality of threshold crossings of the electrogram, compares the determined characteristic identifying features to the electrogram template, and identifies the time of occurrence of the cardiac event based upon the comparison. ### Claim 19 (depends on 18) The device of claim 18, wherein the characteristic identifying feature is electrogram slope. ### Claim 20 (depends on 18) The device of claim 18, wherein the characteristic identifying feature is electrogram amplitude.