# US 6,295,470 B1 · Antitachycardial pacing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,295,470 B1 - Document ID: US6295470B1 - Status: Granted - Kind: B1 - Application number: 09/231,570 - Filed: 1999-01-14 - Granted: 2001-09-25 - Earliest claimed: 1996-08-19 - Assignees: Mower Family CHF Treatment Irrevocable Trust - Inventors: Morton M. Mower - Web page: https://patentgrep.com/patent/US6295470B1 ## CPC - A61N 1/368: comprising more than one electrode co-operating with different heart regions {(A61N1/3622, A61N1/3627 take precedence)} - A61N 1/3622: {comprising two or more electrodes co-operating with different heart regions} - A61N 1/3712: {Auto-capture, i.e. automatic adjustment of the stimulation threshold} - A61N 1/39622: {Pacing therapy} - A61N 1/36514: {controlled by a physiological quantity other than heart potential, e.g. blood pressure (controlled by two or more physical parameters A61N1/36585)} - 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 Protocols for antitachycardial pacing including biphasic stimulation administered at, or just above, the diastolic depolarization threshold potential; biphasic or conventional stimulation initiated at, or just above, the diastolic depolarization threshold potential, reduced, upon capture, to below threshold; and biphasic or conventional stimulation administered at a level set just below the diastolic depolarization threshold potential. These protocols result in reliable cardiac capture with a lower stimulation level, thereby causing less damage to the heart, extending battery life, causing less pain to the patient and having greater therapeutic effectiveness. In those protocols using biphasic cardiac pacing, a first and second stimulation phase is administered. The first stimulation phase has a predefined polarity, amplitude and duration. The second stimulation phase also has a predefined polarity, amplitude and duration. The two phases are applied sequentially. Contrary to current thought, anodal stimulation is first applied and followed by cathodal stimulation. In this fashion, pulse conduction through the cardiac muscle is improved together with the increase in contractility. ## Claims ### Claim 1 A method of operating an implantable cardiac stimulator to perform cardioverting, the cardiac stimulator having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of tachycardia; applying pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold, wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether pacing capture has occurred; wherein in the event it is determined that capture has occurred, the method further comprising: continuing biphasic stimulation for a predetermined period of time. ### Claim 2 (depends on 1) The method of operating an implantable cardiac stimulator as in claim 1, wherein it is determined that capture has not occurred, further comprising: increasing the stimulation intensity level by predefined increments until capture occurs. ### Claim 3 (depends on 1) The method of operating an implantable cardiac stimulator as in claim 1, wherein the first phase polarity is positive. ### Claim 4 (depends on 1) The method of operating an implantable cardiac stimulator as in claim 1, wherein the first phase duration is at least as long as the second phase duration. ### Claim 5 (depends on 1) The method of operating an implantable cardiac stimulator as in claim 1, wherein the first stimulation phase comprises an anodal stimulus. ### Claim 6 A method of operating an implantable cardiac stimulator to perform cardioverting, the cardiac stimulator having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of tachycardia; applying pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold, wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether pacing capture has occurred; wherein the first phase amplitude is less than the second phase amplitude. ### Claim 7 A method of operating an implantable cardiac stimulator to perform cardioverting, the cardiac stimulator having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of tachycardia; applying pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold, wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether pacing capture has occurred; wherein the first phase amplitude is ramped from a baseline value to a second value. ### Claim 8 (depends on 7) The method of operating an implantable cardiac stimulator as in claim 7, wherein the second value is equal to the second phase amplitude. ### Claim 9 (depends on 7) The method of operating an implantable cardiac stimulator as in claim 7, wherein the second value is at a maximum subthreshold amplitude. ### Claim 10 (depends on 9) The method of operating an implantable cardiac stimulator as in claim 9, wherein the maximum subthreshold amplitude is about 0.5 to 3.5 volts. ### Claim 11 (depends on 7) The method of operating an implantable cardiac stimulator as in claim 7, wherein the first phase duration is at least as long as the second phase duration. ### Claim 12 (depends on 7) The method of operating an implantable cardiac stimulator as in claim 7, wherein the first phase duration is about one to nine milliseconds. ### Claim 13 (depends on 7) The method of operating an implantable cardiac stimulator as in claim 7, wherein the second phase amplitude is about two volts to twenty volts. ### Claim 14 (depends on 7) The method of operating an implantable cardiac stimulator as in claim 7, wherein the second phase duration is about 0.2. to 0.9 milliseconds. ### Claim 15 (depends on 7) The method of operating an implantable cardiac stimulator as in claim 7, wherein the second phase duration is less than 0.3 milliseconds and the second phase amplitude is greater than 20 volts. ### Claim 16 A method of operating an implantable cardiac stimulator to perform cardioverting, the cardiac stimulator having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of tachycardia; applying pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold, wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether pacing capture has occurred; wherein the first stimulation phase further comprises a series of stimulating pulses of a predetermined amplitude, polarity and duration. ### Claim 17 (depends on 16) The operating an implantable cardiac stimulator as in claim 16, wherein the first stimulation phase further comprises a series of rest periods. ### Claim 18 (depends on 17) The method of operating an implantable cardiac stimulator as in claim 17, wherein applying the first stimulation phase further comprises applying a rest period of a baseline amplitude after at least one stimulating pulse. ### Claim 19 (depends on 18) The method of operating an implantable cardiac stimulator as in claim 18, wherein the rest period is of equal duration to the duration of the stimulating pulse. ### Claim 20 A method of operating an implantable cardioverter-defibrillator (ICD), the ICD having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of arrhythmia; applying biphasic stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold wherein biphasic stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration, and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether capture has occurred; wherein the first phase amplitude is ramped from a baseline value to a second value; wherein the first stimulation phase further comprises: a series of stimulating pulses of a predetermined amplitude, polarity and duration; and a series of rest periods; wherein applying the first stimulation phase further comprises applying a rest period of a baseline amplitude after at least one stimulating pulse; and wherein the rest period is of equal duration to the duration of the stimulating pulse. ### Claim 21 (depends on 20) The method of operating an ICD as in claim 20, wherein the first stimulation phase comprises an anodal stimulus. ### Claim 22 A method of operating an implantable cardiac stimulator to perform cardioverting, the cardiac stimulator having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of tachycardia; applying pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold, wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether pacing capture has occurred; wherein the first phase amplitude is at a maximum subthreshold amplitude. ### Claim 23 (depends on 22) The method of operating an implantable cardiac stimulator as in claim 22, wherein the maximum subthreshold amplitude is about 0.5 to 3.5 volts. ### Claim 24 A method of operating an implantable cardiac stimulator to perform cardioverting, the cardiac stimulator having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of tachycardia; applying pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold, wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether pacing capture has occurred; wherein the first phase duration is about one to nine milliseconds. ### Claim 25 A method of operating an implantable cardiac stimulator to perform cardioverting, the cardiac stimulator having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of tachycardia; applying pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold, wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether pacing capture has occurred; wherein the second phase duration is about 0.2 to 0.9 milliseconds. ### Claim 26 A method of operating an implantable cardiac stimulator to perform cardioverting, the cardiac stimulator having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of tachycardia; applying pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold, wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether pacing capture has occurred; wherein the second phase amplitude is about two volts to twenty volts. ### Claim 27 A method of operating an implantable cardiac stimulator to perform cardioverting, the cardiac stimulator having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of tachycardia; applying pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold, wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether pacing capture has occurred; wherein the second phase duration is less than 0.3 milliseconds and the second phase amplitude is greater than 20 volts. ### Claim 28 A method of operating an implatable cardioverter-defibrillator (ICD), the ICD having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of arrhythmia; applying biphasic stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold wherein biphasic stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration, and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether capture has occurred; wherein the first phase amplitude is ramped from a baseline value to a second value; and wherein the second phase duration is about 0.2 to 0.9 milliseconds. ### Claim 29 (depends on 28) The method of operating an ICD as in claim 28, wherein the first stimulation phase comprises an anodal stimulus. ### Claim 30 A method of operating an implantable cardioverter-defibrillator (ICD), the ICD having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of arrhythmia; applying biphasic stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold wherein biphasic stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration, and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether capture has occurred; wherein the first phase amplitude is ramped from a baseline value to a second value; and wherein the second phase duration is less than 0.3 milliseconds and the second phase amplitude is greater than 20 volts. ### Claim 31 (depends on 30) The method of operating an ICD as in claim 30, wherein the first stimulation phase comprises an anodal stimulus. ### Claim 32 A method of operating an implantable cardioverter-defibrillator (ICD), the ICD having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of arrhythmia; applying biphasic stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold wherein biphasic stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration, and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and determining whether capture has occurred; wherein the first stimulation phase is initiated greater than 200 milliseconds after completion of a cardiac beating cycle. ### Claim 33 (depends on 32) The method of operating an ICD as in claim 32, wherein the first stimulation phase comprises an anodal stimulus. ### Claim 34 A method of operating an implantable cardioverter-defibrillator )ICD), the ICD having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: sensing the onset of arrhythmia; applying stimulation selected from the group consisting of biphasic stimulation and conventional stimulation at a first intensity level selected from the group consisting of at the diastolic depolarization threshold, below the diastolic depolarization threshold or above the diastolic depolarization threshold; determining whether capture has occurred; increasing the stimulation intensity level by predefined increments until capture does occurs; and upon capture, continuing stimulation selected from the group consisting of biphasic stimulation and conventional stimulation at a second intensity level below the diastolic depolarization threshold. ### Claim 35 A method of operating an implantable cardioverter-defibrillator (ICD), the ICD having output means for delivering electrical stimulation of a predetermined polarity, amplitude, shape and duration, the method comprising: defining a first stimulation phase with a positive polarity, a first phase amplitude, a first phase shape and a first phase duration, wherein said first phase amplitude is about 0.5 to 3.5 volts, wherein said first phase duration is about one to nine milliseconds and wherein said first stimulation phase is initiated greater than 200 milliseconds after completion of a cardiac beating cycle; defining a second phase with a negative polarity, a second phase amplitude, a second phase shape and a second phase duration, wherein said second phase amplitude is about four volts to twenty volts and wherein said second phase duration is about 0.2 to 0.9 milliseconds; and sensing the onset of arrhythmia; applying the first stimulation phase and the second stimulation phase in sequence to the cardiac tissue; determining whether capture has occurred; and increasing the stimulation intensity level by predefined increments until capture occurs. ### Claim 36 A cardiac stimulator to perform cardioverting, the cardiac stimulator comprising: sensing means for sensing the onset of tachycardia; output means for delivering, in response to the sensing means, electrical stimulation of a predetermined polarity, amplitude, shape and duration to cause application of pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of: at the diastolic depolarization threshold, below the diastolic depolarization threshold, and above the diastolic depolarization threshold; and means for determining whether capture has occurred; wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and wherein in the event that the means for determining determines that capture has occurred, the output means continues biphasic stimulation for a predetermined period of time. ### Claim 37 (depends on 36) The cardiac stimulator as in claim 36, wherein in the event that the means for determining determines that capture has not occurred, the output means increases the stimulation intensity level by predefined increments until capture occurs. ### Claim 38 (depends on 36) The cardiac stimulator as in claim 36, wherein the first stimulation phase comprises an anodal stimulus. ### Claim 39 (depends on 36) The cardiac stimulator as in claim 36, wherein the first phase duration is at least as long as the second phase duration. ### Claim 40 A cardiac stimulator to perform cardioverting, the cardiac stimulator comprising: sensing means for sensing the onset of tachycardia; output means for delivering, in response to the sensing means, electrical stimulation of a predetermined polarity, amplitude, shape and duration to cause application of pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of: at the diastolic depolarization threshold, below the diastolic depolarization threshold, and above the diastolic depolarization threshold; and means for determining whether capture has occurred; wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and wherein the first phase amplitude is less than the second phase amplitude. ### Claim 41 A cardiac stimulator to perform cardioverting, the cardiac stimulator comprising: sensing means for sensing the onset of tachycardia; output means for delivering, in response to the sensing means, electrical stimulation of a predetermined polarity, amplitude, shape and duration to cause application of pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of: at the diastolic depolarization threshold, below the diastolic depolarization threshold, and above the diastolic depolarization threshold; and means for determining whether capture has occurred; wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and wherein the first phase amplitude is ramped from a baseline value to a second value. ### Claim 42 (depends on 41) The cardiac stimulator as in claim 41, wherein the second value is equal to the second phase amplitude. ### Claim 43 (depends on 41) The cardiac stimulator as in claim 41, wherein the second value is at a maximum subthreshold amplitude. ### Claim 44 (depends on 43) The cardiac stimulator as in claim 43, wherein the maximum subthreshold amplitude is about 0.5 to 3.5 volts. ### Claim 45 (depends on 41) The cardiac stimulator as in claim 41, wherein the first phase duration is at least as long as the second phase duration. ### Claim 46 (depends on 44) The cardiac stimulator as in claim 44, wherein the first phase duration is about one to nine milliseconds. ### Claim 47 (depends on 44) The cardiac stimulator as in claim 44, wherein the second phase duration is about 0.2 to 0.9 milliseconds. ### Claim 48 (depends on 41) The cardiac stimulator as in claim 41, wherein the second phase amplitude is about two volts to twenty volts. ### Claim 49 (depends on 41) The cardiac stimulator as in claim 41, wherein the second phase duration is less than 0.3 milliseconds and the second phase amplitude is greater than 20 volts. ### Claim 50 A cardiac stimulator to perform cardioverting, the cardiac stimulator comprising: sensing means for sensing the onset of tachycardia; output means for delivering, in response to the sensing means, electrical stimulation of a predetermined polarity, amplitude, shape and duration to cause application of pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of: at the diastolic depolarization threshold, below the diastolic depolarization threshold, and above the diastolic depolarization threshold; and means for determining whether capture has occurred; wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and wherein the first stimulation phase further comprises a series of stimulating pulses of a predetermined amplitude, polarity and duration. ### Claim 51 (depends on 50) The cardiac stimulator as in claim 50, wherein the first stimulation phase further comprises a series of rest periods. ### Claim 52 (depends on 51) The cardiac stimulator as in claim 51, wherein applying the first stimulation phase further comprises applying a rest period of a baseline amplitude after at least one stimulating pulse. ### Claim 53 (depends on 52) The cardiac stimulator as in claim 52, wherein the rest period is of equal duration to the duration of the stimulating pulse. ### Claim 54 A cardiac stimulator to perform cardioverting, the cardiac stimulator comprising: sensing means for sensing the onset of tachycardia; output means for delivering, in response to the sensing means, electrical stimulation of a predetermined polarity, amplitude, shape and duration to cause application of pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of: at the diastolic depolarization threshold, below the diastolic depolarization threshold, and above the diastolic depolarization threshold; and means for determining whether capture has occurred; wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and wherein the first phase amplitude is at a maximum subthreshold amplitude. ### Claim 55 (depends on 54) The cardiac stimulator as in claim 54, wherein the maximum subthreshold amplitude is about 0.5 to 3.5 volts. ### Claim 56 A cardiac stimulator to perform cardioverting, the cardiac stimulator comprising: sensing means for sensing the onset of tachycardia; output means for delivering, in response to the sensing means, electrical stimulation of a predetermined polarity, amplitude, shape and duration to cause application of pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of: at the diastolic depolarization threshold, below the diastolic depolarization threshold, and above the diastolic depolarization threshold; and means for determining whether capture has occurred; wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and wherein the first phase duration is about one to nine milliseconds. ### Claim 57 A cardiac stimulator to perform cardioverting, the cardiac stimulator comprising: sensing means for sensing the onset of tachycardia; output means for delivering, in response to the sensing means, electrical stimulation of a predetermined polarity, amplitude, shape and duration to cause application of pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of: at the diastolic depolarization threshold, below the diastolic depolarization threshold, and above the diastolic depolarization threshold; and means for determining whether capture has occurred; wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and wherein the second phase duration is about 0.2 to 0.9 milliseconds. ### Claim 58 A cardiac stimulator to perform cardioverting, the cardiac stimulator comprising: sensing means for sensing the onset of tachycardia; output means for delivering, in response to the sensing means, electrical stimulation of a predetermined polarity, amplitude, shape and duration to cause application of pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of: at the diastolic depolarization threshold, below the diastolic depolarization threshold, and above the diastolic depolarization threshold; and means for determining whether capture has occurred; wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and wherein the second phase amplitude is about two volts to twenty volts. ### Claim 59 A cardiac stimulator to perform cardioverting, the cardiac stimulator comprising: sensing means for sensing the onset of tachycardia; output means for delivering, in response to the sensing means, electrical stimulation of a predetermined polarity, amplitude, shape and duration to cause application of pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of: at the diastolic depolarization threshold, below the diastolic depolarization threshold, and above the diastolic depolarization threshold; and means for determining whether capture has occurred; wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and wherein the second phase duration is less than 0.3 milliseconds and the second phase amplitude is greater than 20 volts. ### Claim 60 A cardiac stimulator to perform cardioverting, the cardiac stimulator comprising: sensing means for sensing the onset of tachycardia; output means for delivering, in response to the sensing means, electrical stimulation of a predetermined polarity, amplitude, shape and duration to cause application of pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of: at the diastolic depolarization threshold, below the diastolic depolarization threshold, and above the diastolic depolarization threshold; and means for determining whether capture has occurred; wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and wherein the first stimulation phase is initiated greater than 200 milliseconds after completion of a cardiac beating cycle. ### Claim 61 An implantable cardiac stimulator device comprising: plural electrodes; sensing circuitry connected to the plural electrodes and adapted to sense the onset of tachycardia; detecting circuitry connected to the sensing circuitry and adapted to detect whether pacing capture has occurred; and pulse generating circuitry connected to the plural electrodes and adapted to generate, in response to the sensing circuitry, electrical pulses of a predetermined polarity, amplitude, shape and duration to cause application of pulses of biphasic pacing stimulation at a first intensity level selected from the group consisting of: at the diastolic depolarization threshold, below the diastolic depolarization threshold, and above the diastolic depolarization threshold; and wherein each pulse of biphasic pacing stimulation comprises: a first stimulation phase with a first phase polarity, a first phase amplitude, a first phase shape and a first phase duration; and a second stimulation phase with a second phase polarity, a second phase amplitude, a second phase shape and a second phase duration; and wherein, in the event that the detecting circuitry determines that capture has occurred, the pulse generating circuitry continues biphasic stimulation for a predetermined period of time. ### Claim 62 (depends on 61) The implantable cardiac stimulator device as in claim 61, wherein, in the event that the detecting circuitry determines that capture has not occurred, the pulse generating circuitry increases the stimulation intensity level by predefined increments until capture occurs.