# US 5,129,392 A · Apparatus for automatically inducing fibrillation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,129,392 A - Document ID: US5129392A - Status: Granted - Kind: A - Application number: 07/630,445 - Filed: 1990-12-20 - Granted: 1992-07-14 - Earliest claimed: 1990-12-20 - Assignees: Medtronic, Inc. - Inventors: Gust H. Bardy; Rahul Mehra - Web page: https://patentgrep.com/patent/US5129392A ## CPC - A61N 1/385: {Devices for inducing an abnormal cardiac function, e.g. fibrillation} - A61N 1/3943: {for threshold determination} - 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) ## Abstract An automatic fibrillator for inclusion in an implantable defibrillator. Fibrillation induction takes place while the patient's heart is beating at a known rate, and the fibrillation inducing pulse is delivered at a time based on the expected or measured natural refractory period of the patient's heart, at the heart rate in effect during fibrillation induction. In its preferred embodiment, fibrillation induction takes place during overdrive pacing, and the timing of the pulse takes place using an overdrive pacing pulse as a time reference. The period between the pacing pulse and the fibrillation inducing pulse may be determined as a function of actual measurement of the patient's refractory period, either directory, or by means of measurement of the Q-T interval of the patient's heart. ## Claims ### Claim 1 A method of inducing fibrillation in a patient's heart, comprising: measuring the effective refractory period of said patient's heart while pacing said patient's heart at a predetermined rate; deriving a first time interval based on the measured refractory period of said patient's heart; delivering a fibrillation inducing pulse to said patient's heart at said first time interval following delivery of a pacing pulse to said patient's heart. ### Claim 2 (depends on 1) A method according to claim 1 wherein said derived first time interval comprises the measured refractory period of said patient's heart plus a predetermined second time interval. ### Claim 3 A method of inducing fibrillation in a patient's heart, comprising: measuring a time related characteristic of the T-waves of said patient's heart following cardiac pacing pulses delivered at a predetermined rate; deriving a first time interval based on said measured characteristic of said patient's T-waves; delivering a fibrillation inducing pulse to said patient's heart at said first time interval following delivery of a pacing pulse to said patient's heart. ### Claim 4 (depends on 1, 3) A method according to claim 1 or 3, wherein said fibrillation inducing pulse is delivered following a pacing pulse which follows an immediately preceding pacing pulse by an interval corresponding to said predetermined rate. ### Claim 5 (depends on 3) A method according to claim 3 wherein said time related characteristic is the Q-T interval of said patient's heart. ### Claim 6 (depends on 5) A method according to claim 5 wherein said derived first time interval comprises the measured Q-T interval of said patient's heart plus a predetermined second time interval. ### Claim 7 (depends on 2, 6) A method according to claim 6 or claim 2 wherein said second time interval is a fixed time interval. ### Claim 8 (depends on 1, 3) A method according to claim 1 or claim 3 further comprising the step of monitoring said patient's heart following delivery of said fibrillation inducing pulse to determine whether fibrillation is induced. ### Claim 9 (depends on 8) A method according to claim 8 further comprising the step of repeating the step of delivery of said fibrillation inducing pulse until fibrillation is induced. ### Claim 10 (depends on 9) A method according to claim 9 comprising the step of increasing the amplitude of said fibrillation inducing pulse in the event that fibrillation is not induced by delivery of a fibrillation inducing pulse. ### Claim 11 (depends on 9) A method according to claim 9 comprising the step of varying the duration of said first time interval in the event that fibrillation is not induced by delivery of a fibrillation inducing pulse. ### Claim 12 An automatic fibrillator, comprising: means for generating pacing pulses to pace a patient's heart at a predetermined rate; means for measuring the refractory period of said patient's heart while pacing said patient's heart at said predetermined rate; means for deriving a first time interval based on the measured refractory period of said patient's heart; and means for delivering a fibrillation inducing pulse to said patient's heart at said first interval following generation of one of said pacing pulses. ### Claim 13 (depends on 12) A fibrillator according to claim 12 wherein said deriving means comprises means for deriving a first interval equal to said measured refractory period of said patient's heart plus a predetermined second time interval. ### Claim 14 (depends on 13) A fibrillator according to claim 13 wherein said predetermined second time interval is fixed in duration. ### Claim 15 An automatic fibrillator, comprising: means for generating pacing pulses to pace a patient's heart art a predetermined rate; means for measuring a time related characteristic of the T-waves of said patient's heart; means for deriving a first time interval based on the measurement of said time related characteristic; means for delivering a fibrillation inducing pulse at said first time interval following the generation of one of said pacing pulses. ### Claim 16 (depends on 12, 15) A fibrillator according to claim 12 or 15 wherein said delivering means comprises means for delivering said fibrillation inducing pulse following the generation of a first one of said pacing pulses preceded by a second one of said pacing pulses, said first and second pulses generated at said predetermined rate. ### Claim 17 (depends on 15) A fibrillator according to claim 15 wherein said measuring means comprises means for measuring the patient's Q-T interval. ### Claim 18 (depends on 17) A fibrillator according to claim 17 wherein said deriving means comprises means for deriving a first time interval equal to said measured Q-T interval plus a predetermined second time interval. ### Claim 19 (depends on 12, 15) A fibrillator according to claim 12 or 15 further comprising means for monitoring said patient's heart following delivery of said fibrillating pulse to determine whether fibrillation is induced. ### Claim 20 (depends on 19) A fibrillator according to claim 19 further comprising means for repeatedly delivering fibrillation inducing pulses until fibrillation is induced. ### Claim 21 (depends on 20) A fibrillator according to claim 20 further comprising means to vary the duration of said first time interval in the event that fibrillation is not induced by the delivery of a fibrillation inducing pulse. ### Claim 22 (depends on 20) A fibrillator according to claim 20 further comprising means to vary the amplitude of fibrillation inducing pulses in the event that fibrillation is not induced by delivery of a fibrillation inducing pulse. ### Claim 23 A method of inducing fibrillation in a patient's heart, comprising: pacing said patient's heart at a predetermined rate; defining a first time interval based on the refractory period of said patient's heart when paced at said predetermined rate; delivering a fibrillation inducing pulse to said patient's heart at said first time interval following delivery of a pacing pulse at said predetermined rate to said patient's heart. ### Claim 24 (depends on 23) A method according to claim 23 further comprising the step of measuring the refractory period of said patient's heart while pacing said patient's heart at said predetermined rate and wherein said first time interval comprises the measured refractory period of said patient's heart plus a predetermined second time interval. ### Claim 25 (depends on 24) A method according to claim 24 wherein said second time interval is a fixed time interval. ### Claim 26 A method of inducing fibrillation in a patient's heart, comprising: measuring a time related characteristic of the T-waves of said patient's heart following cardiac depolarizations; deriving a first time interval based on said measured characteristic of said patient's T-waves; delivering a fibrillation inducing pulse to said patient's heart following a depolarization of said patient's heart, at the expiration of said first time interval. ### Claim 27 (depends on 26) A method according to claim 26 wherein said time related characteristic is the Q-T interval of said patient's heart. ### Claim 28 (depends on 27) A method according to claim 27 wherein said derived first time interval comprises the measured Q-T interval of said patient's heart adjusted by a predetermined increment. ### Claim 29 (depends on 26) A method according to claim 26 further comprising the step of inducing a cardiac depolarization by delivering a cardiac pacing pulse and wherein said step of delivering a fibrillation inducing pulse comprises delivering said fibrillation inducing pulse at the expiration of said first interval following delivery of said cardiac pacing pulse. ### Claim 30 (depends on 29) A method according to claim 29 wherein said step of measuring said time related characteristic comprises measuring the interval between delivery of cardiac pacing pulses and the occurrence of a repeatably detectable characteristic of the T-waves of said patient's heart. ### Claim 31 (depends on 23, 26) A method according to claim 23 or claim 26 further comprising the step of monitoring said patient's heart following delivery of said fibrillation inducing pulse to determine whether fibrillation is induced. ### Claim 32 (depends on 31) A method according to claim 31 further comprising the step of repeating the step of delivery of said fibrillation inducing pulse until fibrillation is induced. ### Claim 33 (depends on 32) A method according to claim 32 comprising the step of varying the duration of said first time interval in the event that fibrillation is not induced by delivery of a fibrillation inducing pulse. ### Claim 34 (depends on 32) A method according to claim 32 comprising the step of increasing the amplitude of said fibrillation inducing pulse in the event that fibrillation is not induced by delivery of a fibrillation inducing pulse. ### Claim 35 An automatic fibrillator, comprising: means for generating pacing pulses to pace a patient's heart at a predetermined rate; means for defining a first time interval based on the refractory period of said patient's heart when paced at said predetermined rate; and means for delivering a fibrillation inducing pulse to said patient's heart at said first interval following generation of one of said pacing pulses at said predetermined rate. ### Claim 36 (depends on 35) A fibrillator according to claim 35 further comprising means for measuring the refractory period of said patient's heart while pacing said patient's heart at said predetermined rate and wherein said first time interval comprises the measured refractory period of said patient's heart plus a predetermined second time interval. ### Claim 37 (depends on 36) A fibrillator according to claim 36 wherein said second time interval is a fixed time interval. ### Claim 38 An automatic fibrillator, comprising: means for measuring a time related characteristic of the T-waves of said patient's heart following cardiac depolarizations; means for deriving a first time interval based on the measurement of said time related characteristic; means for delivering a fibrillation inducing pulse following a cardiac depolarization, at the expiration of said first time interval. ### Claim 39 (depends on 38) A fibrillator according to claim 38 wherein said time related characteristic is the Q-T interval of said patient'heart. ### Claim 40 (depends on 39) A fibrillator according to claim 39 wherein said derived first time interval comprises the measured Q-T interval of said patient's heart adjusted by a predetermined increment. ### Claim 41 (depends on 38) A fibrillator according to claim 38 further comprising means for inducing a cardiac depolarization by delivering a cardiac pacing pulse and wherein said means for delivering a fibrillation inducing pulse comprises means for delivering said fibrillation inducing pulse at the expiration of said first interval following delivery of said cardiac pacing pulse. ### Claim 42 (depends on 41) A fibrillator according to claim 41 wherein said means for measuring said time related characteristic comprises means for measuring the interval between delivery of said cardiac pacing pulses and the occurrence of a repeatedly detectable characteristic of the T-waves of said patient'heart. ### Claim 43 (depends on 35, 38) A fibrillator according to claim 35 or 38 further comprising means for monitoring said patient's heart following delivery of said fibrillation inducing pulse to determine whether fibrillation is induced. ### Claim 44 (depends on 43) A fibrillator according to claim 43 further comprising means for repeating the step of delivery of said fibrillation inducing pulse until fibrillation is induced. ### Claim 45 (depends on 44) A fibrillator according to claim 44 comprising means for varying the duration of said first time interval in the event that fibrillation is not induced by delivery of a fibrillation inducing pulse. ### Claim 46 (depends on 44) A fibrillator according to claim 44 comprising means for increasing the amplitude of said fibrillation inducing pulse in the event that fibrillation is not induced by delivery of a fibrillation inducing pulse. ### Claim 47 A method of inducing fibrillation in a patient's heart, comprising: measuring the effective refractory period from depolarizations of said patient's heart while said patient's heart is beating at a known rate; deriving a first time interval based on the measured refractory period of said patient's heart; delivering a fibrillation inducing pulse to said patient's heart at said first time interval following a depolarization of said patient's heart while said patient'heart is beating at said known rate. ### Claim 48 (depends on 47) A method according to claim 47 wherein said measuring step comprises pacing said patient's heart at said known rate. ### Claim 49 (depends on 47) A method according to claim 47 wherein said measuring step comprises measuring the Q-T interval of said patient's heart. ### Claim 50 An automatic fibrillator, comprising: means for measuring the refractory period following depolarizations of said patient'heart while said patient's heart beats at a known rate; means for deriving a first time interval based on the measured refractory period of said patient's heart; means for delivering a fibrillation inducing pulse to said patient's heart at said first interval following a depolarization of said patient's heart while said patient's heart beats at said known rate. ### Claim 51 (depends on 50) A fibrillator according to claim 50 wherein said measuring means comprises means for pacing said patient's heart at said known rate while measuring said refractory period. ### Claim 52 (depends on 50) A method according to claim 50 wherein said measuring means comprises means for measuring the Q-T interval of said patient's heart.