Transtelephonic Interrogation of the Implantable Cardioverter Defibrillator MARK H. ANDERSON, VINCE E. PAUL, SUE JONES, DAVID E. WARD, and A. JOHN CAMM From the Department of Cardiological Sciences, St. George's Hospital Medical School, London, England
ANDERSON, M.H., ETAL.: Transtelephonic Interrogation of the Implantable Cardioverter Defibrillator. Third generation impiantable cardioverter defihriilators (/CDs) have extensive memory capability to store data about the patient's arrhythmias and the effect of therapies delivered by the ICD. However, this data has so far been accessible only when the patient attends the pacing clinic. Two Medtronic 9421 PCD'" Teletrace^ transmitters have been used io interrogate Medtronic 7216A and 7217B PCD™s at distances of up to 300 miles from our hospital and transmit the data to a 9420 PCD'" Teletrace^ receiver. Successful transmission of data has been obtained on 50 occasions with 100% data concordance with repeat transmission. The system can reduce the number of unscheduled cJinic visits, reduce delay in making a diagnosis following unexpected delivery of a shock therapy, and reassure patients about to be discharged following ICD implantation. The benefits are magnified where patients reside far away from the implanting center. (PACE, Vol. 15, August 1992) implanfable de/ibrilJator, transteiephonic interrogation
Introduction Early versions of the implantable cardioverter defibrillator (ICD) were simple nonprogrammable devices, the limitations of which were obvious. Over the last 10 years, rapid technical development of the ICD has led to the current third generation devices with programmable antitachycardia pacing, cardioversion, and defibrillation therapies. In parallel with this increasingly sophisticated choice of therapies, these devices offer detailed logging of arrhythmia episodes, therapies delivered, and the response to these therapies. This information enables confirmation of correct ICD function and this in turn can reassure the physician and patient. Unfortunately, this information is only availahle once the device has been interro-
Address for reprints: Dr. Mark H. Anderson, Department of Cardiological Sciences, St. George's Hospital Medical School, Cranmer Terrace, London SW17 ORE. England. Fax: 44817677141. Received September 26, 1991; revision February 10, 1992; accepted February 10, 1992.
1144
gated using a pacemaker programmer. With five of the six third generation ICDs currently under evaluation, full interrogation is possible only using a standard programmer. However, the Medtronic pacer-cardioverter-defibrillator (PCD™) 7216A/7217B device (Medtronic, Inc., Minneapolis, MN, USA) has the potential for full transtelephonic interrogation. In this study, we have evaluated the reliability and ease of use of this system and assessed its potential impact on our clinic and patients. Patient Population Fourteen consecutive patients receiving ICD implants at this institution over the last 21 months formed the population for this study. Because of the small number of implanting centers in the United Kingdom, many of these patients live far away. The average distance of our patients from this center is 73 miles (range 15-300). All patients attend the clinic routinely every 3 months for a check of pacing and sensing and to reform the PCD"^" capacitors. Over a mean follow-up period of 12 months (range 2-21), ten of our 14 patients
August 1992
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TRANSTELEPHONIC DEFIBRILLATOR INTERROGATION
have received an ICD discharge while out of hospital. All ten of these patients have experienced at least one episode [range 1-4) where an ICD discharge was not preceded by typical symptoms, either due to inappropriate therapy delivery or to occurrence of an arrhythmia not associated with immediate hemodynamic collapse. The rapid response of the third generation ICDs, some of which can detect an arrhythmia, charge their capacitors, and deliver a shock in under 10 seconds, increases the likelihood of such an occurrence. We have assessed the use of a transtelephonic interrogation system in two randomly selected patients living 35 and 300 miles from this center. Methods The Medtronic PCD'" Teletrace^ system described in this article is a modification, produced for feasibility analysis, of the standard model 9421 Teletrace** transmitter and model 9420 Teletrace*^ receiver. These devices, designed for transtelephonic pacemaker follow-up, have been equipped
with additional circuitry allowing interrogation of the implantahle Medtronic PCD"^". Each patient was provided with a Medtronic 9421 PCD'" Teletrace'^ transmitter. This device is powered by two 9-V batteries and is fully portable. Telephone contact is established with the pacing clinic. The patient connects two elasticated metal bracelets to the transmitter and switches the transmitter on. The interrogation head is placed over the defihrillator and a light on the transmitter confirms correct placement. The patient places their telephone handset on the Teletrace** transmitter and transmission commences automatically (Fig. 1). Initially a continuous tone transmits a short ECC rhythm strip and this is followed by a series of fractionated tones lasting 50 seconds, which convey the telemetry data. Finally a continuous tone transmits a further 20 seconds of ECC rhythm strip. At the implanting center, the telephone receiver is placed on the Medtronic 9420 PCD'" Teletrace^ receiver as soon as the tones commence. The receiver is connected to a Star ND15 dot-ma-
Figurel. The 9421 PCD'" Teletrace^ transmitter in use. The patient holds the interrogation head over the device as directed hy a series of indicator lights on the transmitter.
PACE, Vol. 15
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ANDERSON, ET AL.
Figure 2. The clinic receiving station. The 9420 PCD" Teietrace'^ receiver (left) is connected to a Star ND15 printer frightj, which produced the interrogation report.
trix computer printer (Fig. 2). After the arrival of the fractionated tones, the data is automatically sent to the printer. A four-page printout is produced identical in format to the output produced by the standard Medtronic Programmer (Fig. 3). This printout contains data on currently programmed back-up pacing, ventricular tachycardia (VT) detection criteria, programmed VT therapies, ventricular fibrillation (VF) detection criteria, programmed VF therapies, battery status, last charge time, episode counter and therapy log for VT and VF, and the RR intervals of the 20 beats preceding the last delivered therapy and the ten beats after this therapy. The printout also shows the identity of the transmitting unit. In case of erroneous placement of the programmer head by the patient, an error message is transmitted in place of the usual printout. To assess the reliability and repeatabihty of data transmitted by the system, we have performed 50 routine transtelephonic interrogations over the past 6 months. On each occasion we have telephoned the patient and have obtained two
1146
complete interrogation printouts. On those occasions where an interrogation attempt failed, the procedure has been repeated until two complete printouts were obtained. All printouts were checked for consistency with those obtained on the same occasion, and on previous and subsequent occasions. The duration of the call and the number of attempts required to obtain two complete printouts were recorded.
Results Transtelephonic interrogation was attempted on 50 occasions. On each occasion, two complete printouts were obtained after a mean of 2.94 attempts (range 2-6). There was 100% concordance of telemetered data between the two printouts on each occasion and data was consistent with that obtained from previous interrogations and those performed subsequently. A total of 147 interrogations were performed and 47 of these failed. Reason for failure was "stalling" of the printer during printout (60%), "no telemetry data" message from
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TRANSTELEPHONIC DEFIBRILLATOR INTERROGATION
In addition, a further 20 transtelephonic interrogations were performed with the patient in the pacing clinic, confirming 100% concordance of the data transmitted with that obtained from the standard programmer.
MEDTRONIC 9420PCD TELETRACE RECEIVER SOFTWARE REVISION; 9 4 2 0 P C D - 0 0 2 PCD MODEL 7 2 1 6 TRANSMITTER I D : 0 0 0 0 0 2 2 5 TIME AND DATE; INTERROGATE VALUES: PACING AND SENSING
PACING MODE PACING RATE PACING PULSE WIDTH PACING AMPLITUDE SENSITIVITY REFRACTORY AFTER PACE
VVI 40 1.01 5.4 0.6 320
Discussion PPM MS V MV MS
Over the last 10 years, the implantahle defihrillator has undergone rapid technical development. From a simple device capable of detecting
VT DETECTION AND THERAPIES VT DETECT: VT DETECTION ENABLE VT DETECTION INTERVAL * INTERVALS TO DETECT INTERVAL STABILITY ONSET CRITERIA ENABLE ONSET VALUE (R-R*) ONSET COUNTER ENABLE
MEDTRONIC 9420PCD TELETRACE RECEIVER SOFTWARE REVISION; 9420PCD-002 PCD MODEL 7216 TRANSMITTER ID: 00000225
ON 400 MS 16
OFF OFF
VT THERAPY #3: THERAPY TYPE VT THERAPY ENABLE CV PULSE WIDTH CV ENERGY (JOULES) CV CURRENT PATHWAY
75 %
OH
VT THERAPY *1:
THERAPY TYPE
VT THERAPY ENABLE * OF SI PULSES Sl-Sl INTERVAL PER SEQUENCE DECREMENT * OF SEQUENCES MINIMUM INTERVAL
VT THERAPY *2: THERAPY TYPE VT THERAPY ENABLE CV PULSE WIDTH CV ENERGY (JOULES) CV CURRENT PATHWAY
BURST%
ON 6 91 % 20 MS 3 230 MS
VT THERAPY *4i THERAPY TYPE VT THERAPY ENABLE CV PULSE WIDTH CV ENERGY (JOULES) CV CURRENT PATHWAY
CARDIOVERSION
ON 6.3 MS 18.1 JOUL SIML
Figure 3A. Page 1 of the printout shou'ing transmitter identity, currentiy programmed pacing and sensing. VT detection criteria, and first Iwo VT therapies. the transmitter (this suggests incorrect placement of interrogation head by the patient [30%]), transmitter battery depletion (4%), and no apparent reason (6%). The mean duration of the telephone call required to obtain two complete printouts was 7 minutes (range 4-19). On three occasions the printout showed that pacing therapies had been delivered for tachycardias of which the patient was unaware. The tachycardia intervals obtained from the device suggested that these therapies were appropriate. Had the devices not been interrogated until the next routine clinic visit, the tachycardia interval data on two of these three episodes would have been erased by subsequent tachycardia episodes.
PACE. Vol. 15
CARDIOVERSION
ON 6.3 MS 34.1 JOUL SIML
CARDIOVERSION
ON 6.3 MS 34.1 JOUL SIML
VF DETECTION AND THERAPIES VF DETECT: VF DETECTION ENABLE VF DETECTION INTERVAL • INTERVALS TO DETECT
ON 270 MS 16
VF DEFIBRILLATION THERAPY *1: VF THERAPY ENABLE DEFIB PULSE WIDTH DEFIB ENERGY (JOULES) DEFIB CURRENT PATHWAY
ON 6.3 MS 34.1 JOUL SNGL
VF DEFIBRILLATION THERAPY * 2 : VF THERAPY ENABLE DEFIB PULSE WIDTH DEFIB ENERGY (JOULES) DEFIB CURRENT PATHWAY
ON 6.3 MS 34.1 JOUL SNGL
VF DEFIBRILLATION THERAPY #3: VF THERAPY ENABLE DEFIB PULSE WIDTH DEFIB ENERGY (JOULES) DEFIB CURRENT PATHWAY
ON 6.3 MS 34.1 JOUL SNGL
vr DEFIBRILLATION THERAPY #4! VF THERAPY ENABLE DEFIB PULSE WIDTH DEFIB ENERGY (JOULES) DEFIB CURRENT PATHWAY
ON 6.3 MS 34.1 JOUL SNGL
Figure 3B. Page 2 of the printout showing remaining V T fherapies and V F detection and therapy settings.
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ANDERSON. ET AL. MEDTKONIC 9420PCD TELETRACE RECEIVER SOFTWARE REVISION: 9420PCD-002 PCD MODEL 7216 TRANSMITTER ID: 00000225
an ICD is often symptomatic. Syncopal attacks related to arrhythmias may continue and the patient may or may not be aware of ICD discharges. Less dramatically the patient may be aware of continuing short-lived episodes of tachycardia terminated by antitachycardia pacing. In some patients the arrhythmia may be asymptomatic but the shock or pacing therapy programmed to terminate it may be immediately noticed. Inappropriate function of the ICD can produce identical symptoms. The fre-
TELEMETRY PERM TELEMETRY ENABLE TELEMETRY TYPE DATA PCD STATUS: MEMORY RETENTION CHARGE CIRCUIT LAST CHARGE TIME CIRCUITRY BATTERY CHARGING BATTERY
OFF MRKR
OK OK . 3 0 SEC .05 V 6.39 V
VT ONSET COUNTER VT EPISODE AND THERAPY DATA; EPISODE COUNT VT THERAPY *1 SUCCESS COUNT VT THERAPY # 2 SUCCESS COUNT VT THERAPY # 3 SUCCESS COUNT VT THERAPY # 4 SUCCESS COUNT * OF V T ' S PCD INEFFECTIVE PCD EFFICACIOUS ON LAST VT LAST THERAPY USED #SEQ IN LAST PACE THERAPY R-R AVG FOR LAST PACE THRPY
41 36 1 0 0 4 YES *1 1 380 MS
VF EPISODE AND THERAPY DATA: EPISODE COUNT VF THERAPY # 1 SUCCESS COUNT VF THERAPY # 2 SUCCESS COUNT VF THERAPY # 3 SUCCESS COUNT VF THERAPY # 4 SUCCESS COUNT PCD EFFICACIOUS ON LAST VF LAST THERAPY USED
44 42 2 0 0 YES *1
Figure 3C. Page 3 of the printout showing telemetry settings, battery status, last charge time, and episode counter and therapy Jog for VT and VF.
VF and delivering a defibrillating shock, it has acquired cardioversion, bradycardia support pacing, antitachycardia pacing, and extensive Holter and data logging functions. Because the only information that could be obtained from first generation devices was charge time and total shock count, defibrillator follow-up settled into a pattern of regular clinic visits similar to that required for conventional pacemakers, However, this type of follow-up ignores some important differences between pacemakers and defibrillators. Satisfactory function of a bradycardia support pacemaker is not normally associated with symptoms. However, satisfactory function of
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MEDTRONIC 9420PCD TELETRACE RECEIVER SOFTWARE REVISION: 9420PCD-002 PCD MODEL 7216 TRANSMITTER ID: 00000225 LAST EPISODE DETECTION SEQUENCE •19. R-R INTERVAL- 410 MS -18. R-R INTERVAL- 360 MS -17. R-R INTERVAL- 380 MS -16. R-R INTERVAL- 400 MS -15. R-R INTERVAL- 340 MS -14. R-R INTERVAL- 390 MS -13. R-R INTERVAL- 380 MS -12. R-R INTERVAL- 370 MS - 1 1 . R-R INTERVAL- 370 MS -10. R-R INTERVAL- 380 MS - 9 . R-R INTERVAL- 370 MS - 8 . R-R INTERVAL- 380 MS - 7 . R-R INTERVAL- 370 MS - 6 . R-R INTERVAL- 380 MS - 5 . R-R INTERVAL- 380 MS - 4 . K-R INTERVAL- 380 MS - 3 . R-R INTERVAL- 380 MS - 2 . R-R INTERVAL- 380 MS - 1 . R-R INTERVAL- 370 MS - 0 . R-R INTERVAL- 380 MS - 0 . VT DETECTED EVENTS + 0. + 1. +2. +3. +4. +5. +6. +7. +8. +9. + 10. +10.
AFTER LAST THERAPY: VT THERAPY #1 DELIVERED R-R INTERVAL- lOOOMS R-R INTERVAL- 670MS R-R INTERVAL- 1060MS R-R INTERVAL- 1050MS R-R INTERVAL- 1060MS R-R INTERVAL- 1040MS R-R INTERVAL- 1040MS R-R INTERVAL- 1050MS R-R INTERVAL- 1040MS R-R INTERVAL- 1070MS THERAPY WAS SUCCESSFUL
Figure 3D. Page 4 of the printout showing the R-fi intervals of (he 20 beats preceding the Jast deJiVered therapy and the ten heats after this therapy.
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TRANSTELEPHONIC DEFIBRILLATOR INTERROGATION
quency of arrhythmias may vary over time and the nature of symptoms associated with arrhythmias may change.^ All of these factors combine to produce a more frequent requirement for unscheduled follow-up visits than occurs during routine bradycardia support pacing. Where patients live far from the implanting clinic, such visits can be a major source of disruption and the delay before correct device function can be confirmed can cause unnecessary anxiety. The availability of a reliable transtelephonic interrogation system could help to minimize such problems. Transtelephonic monitoring of conventional pacemakers has a long history and has been widely used for follow-up purposes, particularly in the United States.^"^ More recently, trials of transtelephonic control of conventional defibrillation have been described'* within hospital, and transtelephonic transmission of automatic implantable cardioverter defibrillator (Cardiac Pacemakers, Inc., St. Paul, MN, USA) beepergrams has been used to assess adequacy of sensing in relation to a simultaneously transmitted ECG.^ Transtelephonic ECG monitoring has been used to assess the function of antitachycardia pacemakers^ and to study the rhythms precipitating ICD discharge.^ In a recent article describing such a system, Porterfield and colleagues" showed that 60% of patients received an ICD discharge within the first several months after device implantation. Some 90% of the transtelephonic transmissions for suspected ICD discharge took place in the first 2 months of their study. However, the precipitating arrhythmia was only captured in eight of 19 episodes because of delay in activation of the recording system by the patient. The presence of an ICD discharge could then only be confirmed at the subsequent clinic visit. In addition, this system requires the patient to wear an 8.5-ounce electronic recorder with four skin electrodes for periods of months at a time! By contrast, transtelephonic interrogation of the ICD does not require any action by the patient at the time of the arrhythmia and no additional equipment needs to be worn. A number of manufacturers are developing transtelephonic interrogation systems for their third generation defibrillators. The PRx^'^ (Cardiac Pacemakers, Inc.) has a transtelephonic facility providing limited information on battery status, therapy status (on or off), and whether a ther-
PACE, Vol. 15
apy has been delivered since last interrogation only. Full transtelephonic interrogation with the PCD'" Teletrace** system offers many potential advantages. Even in our small population of ICD patients, 12 clinic visits could have been avoided with considerable savings in time for patients and medical staff alike. The average delay between the therapy occurring and the patient reaching the defibrillator clinic was 18 hours (range 3-36), and many of our patients expressed anxiety at having to travel to the hospital when there was a doubt concerning correct functioning of the ICD. This anxiety would have been avoided had we been able to provide all of our patients with a transtelephonic system. The first shock therapy that any patient receives from their ICD often produces anxiety over the function of the device, even when the shock has followed symptoms suggestive of an arrhythmia. As the majority of patients who receive a shock do so within the first 6 months,^ provision for all patients with a transtelephonic system for this period would improve the quality of patient follow-up, minimize undue anxiety, and reduce disruption to the lifestyle of the patient. To maximize the value of transtelephonic interrogation, implanting centers could provide a 24-hour telephone number enabling patients to obtain an interrogation at any time. This service could be provided by single centers, groups of centers, or even by a national or manufacturer sponsored organization. Once a printout has been obtained, it can easily be sent by facsimile to the physician caring for the patient. Conclusion Transtelephonic interrogation of the Medtronic PCD''' 7216A/7217B defibrillator is practical and reliable. This technique offers potential savings in time and inconvenience for patients and hospital staff and avoids anxious journeys to the hospital when doubt about ICD function exists. Ail future defibrillators should incorporate such a system. We would recommend provision of a remote transmitter for all patients for 3 to 6 months following implantation of the device, for all patients who live far from the hospital, and for those patients suffering an increased frequency of defibrillator discharge.
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References 1. Kou W, Clakins H, Lewis R, et al. Syncope may occur during automatic cardioverter defibrillator shocks in patients whose initial presentation of ventricular tachycardia was presyncope: Implications for driving, (abstract) PACE 1991; 14:721. 2. Dreifus LS, Zinberg A, Hurzeler P, et al. Transtelephonic monitoring of 25,919 implanted pacemakers. PACE 1986; 9;371-378. 3. Parsonnet V, Crawford CC, Bernstein AD. The 1981 United States survey of cardiac pacing practices. J Am Coll Cardiol 1984; 3:1321-1332. 4. Feldstein JS, O'Connor RE, Henry J, et al. Transtelephonic defibrillation. Ann Emerg Med 1990; 19:1367-1370. 5. Gessman LJ,, Raman SY, Janeira L, et al. Transtelephonic ECG-heepergram telemetry: A new device and method for implanted defihrillator follow-up, (abstract) PACE 1991; 14:718.
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Lyons C, Schroeder P. Shankar K, et al. Transtelephonic monitoring of a tachycardia-terminating pacemaker. PACE 1984; 7:34-36. Steinberg JS, Sugalaski JS. Cardiac rhythm precipitating automatic implantable-cardioverter defibrillator discharge in outpatients as detected from transtelephonic electrocardiographic recordings. Am ] Cardiol 1991; 67:95-97. Porterfield JG, Porterfield IM, Bray L, et al. A prospective study utilizing a transtelephonic electrocardiographic transmission program to manage patients in the first several months post-ICD implant. PACE 1991; 14:308-311. Fogoros RN, Elson JJ, Bonnet CA. Actuarial incidence and pattern of occurrence of shocks following implantation of the automatic implantable cardioverter defibrillator. PACE 1989; 12;1465-1473.
PACE, Vol. 15
ANDERSON, M.H., ETAL.: Transtelephonic Interrogation of the Implantable Cardioverter Defibrillator. Third generation impiantable cardioverter defihriilators (/CDs) have extensive memory capability to store data about the patient's arrhythmias and the effect of therapies delivered by the ICD. However, this data has so far been accessible only when the patient attends the pacing clinic. Two Medtronic 9421 PCD'" Teletrace^ transmitters have been used io interrogate Medtronic 7216A and 7217B PCD™s at distances of up to 300 miles from our hospital and transmit the data to a 9420 PCD'" Teletrace^ receiver. Successful transmission of data has been obtained on 50 occasions with 100% data concordance with repeat transmission. The system can reduce the number of unscheduled cJinic visits, reduce delay in making a diagnosis following unexpected delivery of a shock therapy, and reassure patients about to be discharged following ICD implantation. The benefits are magnified where patients reside far away from the implanting center. (PACE, Vol. 15, August 1992) implanfable de/ibrilJator, transteiephonic interrogation
Introduction Early versions of the implantable cardioverter defibrillator (ICD) were simple nonprogrammable devices, the limitations of which were obvious. Over the last 10 years, rapid technical development of the ICD has led to the current third generation devices with programmable antitachycardia pacing, cardioversion, and defibrillation therapies. In parallel with this increasingly sophisticated choice of therapies, these devices offer detailed logging of arrhythmia episodes, therapies delivered, and the response to these therapies. This information enables confirmation of correct ICD function and this in turn can reassure the physician and patient. Unfortunately, this information is only availahle once the device has been interro-
Address for reprints: Dr. Mark H. Anderson, Department of Cardiological Sciences, St. George's Hospital Medical School, Cranmer Terrace, London SW17 ORE. England. Fax: 44817677141. Received September 26, 1991; revision February 10, 1992; accepted February 10, 1992.
1144
gated using a pacemaker programmer. With five of the six third generation ICDs currently under evaluation, full interrogation is possible only using a standard programmer. However, the Medtronic pacer-cardioverter-defibrillator (PCD™) 7216A/7217B device (Medtronic, Inc., Minneapolis, MN, USA) has the potential for full transtelephonic interrogation. In this study, we have evaluated the reliability and ease of use of this system and assessed its potential impact on our clinic and patients. Patient Population Fourteen consecutive patients receiving ICD implants at this institution over the last 21 months formed the population for this study. Because of the small number of implanting centers in the United Kingdom, many of these patients live far away. The average distance of our patients from this center is 73 miles (range 15-300). All patients attend the clinic routinely every 3 months for a check of pacing and sensing and to reform the PCD"^" capacitors. Over a mean follow-up period of 12 months (range 2-21), ten of our 14 patients
August 1992
PACE, Vol. 15
TRANSTELEPHONIC DEFIBRILLATOR INTERROGATION
have received an ICD discharge while out of hospital. All ten of these patients have experienced at least one episode [range 1-4) where an ICD discharge was not preceded by typical symptoms, either due to inappropriate therapy delivery or to occurrence of an arrhythmia not associated with immediate hemodynamic collapse. The rapid response of the third generation ICDs, some of which can detect an arrhythmia, charge their capacitors, and deliver a shock in under 10 seconds, increases the likelihood of such an occurrence. We have assessed the use of a transtelephonic interrogation system in two randomly selected patients living 35 and 300 miles from this center. Methods The Medtronic PCD'" Teletrace^ system described in this article is a modification, produced for feasibility analysis, of the standard model 9421 Teletrace** transmitter and model 9420 Teletrace*^ receiver. These devices, designed for transtelephonic pacemaker follow-up, have been equipped
with additional circuitry allowing interrogation of the implantahle Medtronic PCD"^". Each patient was provided with a Medtronic 9421 PCD'" Teletrace'^ transmitter. This device is powered by two 9-V batteries and is fully portable. Telephone contact is established with the pacing clinic. The patient connects two elasticated metal bracelets to the transmitter and switches the transmitter on. The interrogation head is placed over the defihrillator and a light on the transmitter confirms correct placement. The patient places their telephone handset on the Teletrace** transmitter and transmission commences automatically (Fig. 1). Initially a continuous tone transmits a short ECC rhythm strip and this is followed by a series of fractionated tones lasting 50 seconds, which convey the telemetry data. Finally a continuous tone transmits a further 20 seconds of ECC rhythm strip. At the implanting center, the telephone receiver is placed on the Medtronic 9420 PCD'" Teletrace^ receiver as soon as the tones commence. The receiver is connected to a Star ND15 dot-ma-
Figurel. The 9421 PCD'" Teletrace^ transmitter in use. The patient holds the interrogation head over the device as directed hy a series of indicator lights on the transmitter.
PACE, Vol. 15
August 1992
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ANDERSON, ET AL.
Figure 2. The clinic receiving station. The 9420 PCD" Teietrace'^ receiver (left) is connected to a Star ND15 printer frightj, which produced the interrogation report.
trix computer printer (Fig. 2). After the arrival of the fractionated tones, the data is automatically sent to the printer. A four-page printout is produced identical in format to the output produced by the standard Medtronic Programmer (Fig. 3). This printout contains data on currently programmed back-up pacing, ventricular tachycardia (VT) detection criteria, programmed VT therapies, ventricular fibrillation (VF) detection criteria, programmed VF therapies, battery status, last charge time, episode counter and therapy log for VT and VF, and the RR intervals of the 20 beats preceding the last delivered therapy and the ten beats after this therapy. The printout also shows the identity of the transmitting unit. In case of erroneous placement of the programmer head by the patient, an error message is transmitted in place of the usual printout. To assess the reliability and repeatabihty of data transmitted by the system, we have performed 50 routine transtelephonic interrogations over the past 6 months. On each occasion we have telephoned the patient and have obtained two
1146
complete interrogation printouts. On those occasions where an interrogation attempt failed, the procedure has been repeated until two complete printouts were obtained. All printouts were checked for consistency with those obtained on the same occasion, and on previous and subsequent occasions. The duration of the call and the number of attempts required to obtain two complete printouts were recorded.
Results Transtelephonic interrogation was attempted on 50 occasions. On each occasion, two complete printouts were obtained after a mean of 2.94 attempts (range 2-6). There was 100% concordance of telemetered data between the two printouts on each occasion and data was consistent with that obtained from previous interrogations and those performed subsequently. A total of 147 interrogations were performed and 47 of these failed. Reason for failure was "stalling" of the printer during printout (60%), "no telemetry data" message from
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TRANSTELEPHONIC DEFIBRILLATOR INTERROGATION
In addition, a further 20 transtelephonic interrogations were performed with the patient in the pacing clinic, confirming 100% concordance of the data transmitted with that obtained from the standard programmer.
MEDTRONIC 9420PCD TELETRACE RECEIVER SOFTWARE REVISION; 9 4 2 0 P C D - 0 0 2 PCD MODEL 7 2 1 6 TRANSMITTER I D : 0 0 0 0 0 2 2 5 TIME AND DATE; INTERROGATE VALUES: PACING AND SENSING
PACING MODE PACING RATE PACING PULSE WIDTH PACING AMPLITUDE SENSITIVITY REFRACTORY AFTER PACE
VVI 40 1.01 5.4 0.6 320
Discussion PPM MS V MV MS
Over the last 10 years, the implantahle defihrillator has undergone rapid technical development. From a simple device capable of detecting
VT DETECTION AND THERAPIES VT DETECT: VT DETECTION ENABLE VT DETECTION INTERVAL * INTERVALS TO DETECT INTERVAL STABILITY ONSET CRITERIA ENABLE ONSET VALUE (R-R*) ONSET COUNTER ENABLE
MEDTRONIC 9420PCD TELETRACE RECEIVER SOFTWARE REVISION; 9420PCD-002 PCD MODEL 7216 TRANSMITTER ID: 00000225
ON 400 MS 16
OFF OFF
VT THERAPY #3: THERAPY TYPE VT THERAPY ENABLE CV PULSE WIDTH CV ENERGY (JOULES) CV CURRENT PATHWAY
75 %
OH
VT THERAPY *1:
THERAPY TYPE
VT THERAPY ENABLE * OF SI PULSES Sl-Sl INTERVAL PER SEQUENCE DECREMENT * OF SEQUENCES MINIMUM INTERVAL
VT THERAPY *2: THERAPY TYPE VT THERAPY ENABLE CV PULSE WIDTH CV ENERGY (JOULES) CV CURRENT PATHWAY
BURST%
ON 6 91 % 20 MS 3 230 MS
VT THERAPY *4i THERAPY TYPE VT THERAPY ENABLE CV PULSE WIDTH CV ENERGY (JOULES) CV CURRENT PATHWAY
CARDIOVERSION
ON 6.3 MS 18.1 JOUL SIML
Figure 3A. Page 1 of the printout shou'ing transmitter identity, currentiy programmed pacing and sensing. VT detection criteria, and first Iwo VT therapies. the transmitter (this suggests incorrect placement of interrogation head by the patient [30%]), transmitter battery depletion (4%), and no apparent reason (6%). The mean duration of the telephone call required to obtain two complete printouts was 7 minutes (range 4-19). On three occasions the printout showed that pacing therapies had been delivered for tachycardias of which the patient was unaware. The tachycardia intervals obtained from the device suggested that these therapies were appropriate. Had the devices not been interrogated until the next routine clinic visit, the tachycardia interval data on two of these three episodes would have been erased by subsequent tachycardia episodes.
PACE. Vol. 15
CARDIOVERSION
ON 6.3 MS 34.1 JOUL SIML
CARDIOVERSION
ON 6.3 MS 34.1 JOUL SIML
VF DETECTION AND THERAPIES VF DETECT: VF DETECTION ENABLE VF DETECTION INTERVAL • INTERVALS TO DETECT
ON 270 MS 16
VF DEFIBRILLATION THERAPY *1: VF THERAPY ENABLE DEFIB PULSE WIDTH DEFIB ENERGY (JOULES) DEFIB CURRENT PATHWAY
ON 6.3 MS 34.1 JOUL SNGL
VF DEFIBRILLATION THERAPY * 2 : VF THERAPY ENABLE DEFIB PULSE WIDTH DEFIB ENERGY (JOULES) DEFIB CURRENT PATHWAY
ON 6.3 MS 34.1 JOUL SNGL
VF DEFIBRILLATION THERAPY #3: VF THERAPY ENABLE DEFIB PULSE WIDTH DEFIB ENERGY (JOULES) DEFIB CURRENT PATHWAY
ON 6.3 MS 34.1 JOUL SNGL
vr DEFIBRILLATION THERAPY #4! VF THERAPY ENABLE DEFIB PULSE WIDTH DEFIB ENERGY (JOULES) DEFIB CURRENT PATHWAY
ON 6.3 MS 34.1 JOUL SNGL
Figure 3B. Page 2 of the printout showing remaining V T fherapies and V F detection and therapy settings.
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an ICD is often symptomatic. Syncopal attacks related to arrhythmias may continue and the patient may or may not be aware of ICD discharges. Less dramatically the patient may be aware of continuing short-lived episodes of tachycardia terminated by antitachycardia pacing. In some patients the arrhythmia may be asymptomatic but the shock or pacing therapy programmed to terminate it may be immediately noticed. Inappropriate function of the ICD can produce identical symptoms. The fre-
TELEMETRY PERM TELEMETRY ENABLE TELEMETRY TYPE DATA PCD STATUS: MEMORY RETENTION CHARGE CIRCUIT LAST CHARGE TIME CIRCUITRY BATTERY CHARGING BATTERY
OFF MRKR
OK OK . 3 0 SEC .05 V 6.39 V
VT ONSET COUNTER VT EPISODE AND THERAPY DATA; EPISODE COUNT VT THERAPY *1 SUCCESS COUNT VT THERAPY # 2 SUCCESS COUNT VT THERAPY # 3 SUCCESS COUNT VT THERAPY # 4 SUCCESS COUNT * OF V T ' S PCD INEFFECTIVE PCD EFFICACIOUS ON LAST VT LAST THERAPY USED #SEQ IN LAST PACE THERAPY R-R AVG FOR LAST PACE THRPY
41 36 1 0 0 4 YES *1 1 380 MS
VF EPISODE AND THERAPY DATA: EPISODE COUNT VF THERAPY # 1 SUCCESS COUNT VF THERAPY # 2 SUCCESS COUNT VF THERAPY # 3 SUCCESS COUNT VF THERAPY # 4 SUCCESS COUNT PCD EFFICACIOUS ON LAST VF LAST THERAPY USED
44 42 2 0 0 YES *1
Figure 3C. Page 3 of the printout showing telemetry settings, battery status, last charge time, and episode counter and therapy Jog for VT and VF.
VF and delivering a defibrillating shock, it has acquired cardioversion, bradycardia support pacing, antitachycardia pacing, and extensive Holter and data logging functions. Because the only information that could be obtained from first generation devices was charge time and total shock count, defibrillator follow-up settled into a pattern of regular clinic visits similar to that required for conventional pacemakers, However, this type of follow-up ignores some important differences between pacemakers and defibrillators. Satisfactory function of a bradycardia support pacemaker is not normally associated with symptoms. However, satisfactory function of
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MEDTRONIC 9420PCD TELETRACE RECEIVER SOFTWARE REVISION: 9420PCD-002 PCD MODEL 7216 TRANSMITTER ID: 00000225 LAST EPISODE DETECTION SEQUENCE •19. R-R INTERVAL- 410 MS -18. R-R INTERVAL- 360 MS -17. R-R INTERVAL- 380 MS -16. R-R INTERVAL- 400 MS -15. R-R INTERVAL- 340 MS -14. R-R INTERVAL- 390 MS -13. R-R INTERVAL- 380 MS -12. R-R INTERVAL- 370 MS - 1 1 . R-R INTERVAL- 370 MS -10. R-R INTERVAL- 380 MS - 9 . R-R INTERVAL- 370 MS - 8 . R-R INTERVAL- 380 MS - 7 . R-R INTERVAL- 370 MS - 6 . R-R INTERVAL- 380 MS - 5 . R-R INTERVAL- 380 MS - 4 . K-R INTERVAL- 380 MS - 3 . R-R INTERVAL- 380 MS - 2 . R-R INTERVAL- 380 MS - 1 . R-R INTERVAL- 370 MS - 0 . R-R INTERVAL- 380 MS - 0 . VT DETECTED EVENTS + 0. + 1. +2. +3. +4. +5. +6. +7. +8. +9. + 10. +10.
AFTER LAST THERAPY: VT THERAPY #1 DELIVERED R-R INTERVAL- lOOOMS R-R INTERVAL- 670MS R-R INTERVAL- 1060MS R-R INTERVAL- 1050MS R-R INTERVAL- 1060MS R-R INTERVAL- 1040MS R-R INTERVAL- 1040MS R-R INTERVAL- 1050MS R-R INTERVAL- 1040MS R-R INTERVAL- 1070MS THERAPY WAS SUCCESSFUL
Figure 3D. Page 4 of the printout showing the R-fi intervals of (he 20 beats preceding the Jast deJiVered therapy and the ten heats after this therapy.
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TRANSTELEPHONIC DEFIBRILLATOR INTERROGATION
quency of arrhythmias may vary over time and the nature of symptoms associated with arrhythmias may change.^ All of these factors combine to produce a more frequent requirement for unscheduled follow-up visits than occurs during routine bradycardia support pacing. Where patients live far from the implanting clinic, such visits can be a major source of disruption and the delay before correct device function can be confirmed can cause unnecessary anxiety. The availability of a reliable transtelephonic interrogation system could help to minimize such problems. Transtelephonic monitoring of conventional pacemakers has a long history and has been widely used for follow-up purposes, particularly in the United States.^"^ More recently, trials of transtelephonic control of conventional defibrillation have been described'* within hospital, and transtelephonic transmission of automatic implantable cardioverter defibrillator (Cardiac Pacemakers, Inc., St. Paul, MN, USA) beepergrams has been used to assess adequacy of sensing in relation to a simultaneously transmitted ECG.^ Transtelephonic ECG monitoring has been used to assess the function of antitachycardia pacemakers^ and to study the rhythms precipitating ICD discharge.^ In a recent article describing such a system, Porterfield and colleagues" showed that 60% of patients received an ICD discharge within the first several months after device implantation. Some 90% of the transtelephonic transmissions for suspected ICD discharge took place in the first 2 months of their study. However, the precipitating arrhythmia was only captured in eight of 19 episodes because of delay in activation of the recording system by the patient. The presence of an ICD discharge could then only be confirmed at the subsequent clinic visit. In addition, this system requires the patient to wear an 8.5-ounce electronic recorder with four skin electrodes for periods of months at a time! By contrast, transtelephonic interrogation of the ICD does not require any action by the patient at the time of the arrhythmia and no additional equipment needs to be worn. A number of manufacturers are developing transtelephonic interrogation systems for their third generation defibrillators. The PRx^'^ (Cardiac Pacemakers, Inc.) has a transtelephonic facility providing limited information on battery status, therapy status (on or off), and whether a ther-
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apy has been delivered since last interrogation only. Full transtelephonic interrogation with the PCD'" Teletrace** system offers many potential advantages. Even in our small population of ICD patients, 12 clinic visits could have been avoided with considerable savings in time for patients and medical staff alike. The average delay between the therapy occurring and the patient reaching the defibrillator clinic was 18 hours (range 3-36), and many of our patients expressed anxiety at having to travel to the hospital when there was a doubt concerning correct functioning of the ICD. This anxiety would have been avoided had we been able to provide all of our patients with a transtelephonic system. The first shock therapy that any patient receives from their ICD often produces anxiety over the function of the device, even when the shock has followed symptoms suggestive of an arrhythmia. As the majority of patients who receive a shock do so within the first 6 months,^ provision for all patients with a transtelephonic system for this period would improve the quality of patient follow-up, minimize undue anxiety, and reduce disruption to the lifestyle of the patient. To maximize the value of transtelephonic interrogation, implanting centers could provide a 24-hour telephone number enabling patients to obtain an interrogation at any time. This service could be provided by single centers, groups of centers, or even by a national or manufacturer sponsored organization. Once a printout has been obtained, it can easily be sent by facsimile to the physician caring for the patient. Conclusion Transtelephonic interrogation of the Medtronic PCD''' 7216A/7217B defibrillator is practical and reliable. This technique offers potential savings in time and inconvenience for patients and hospital staff and avoids anxious journeys to the hospital when doubt about ICD function exists. Ail future defibrillators should incorporate such a system. We would recommend provision of a remote transmitter for all patients for 3 to 6 months following implantation of the device, for all patients who live far from the hospital, and for those patients suffering an increased frequency of defibrillator discharge.
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References 1. Kou W, Clakins H, Lewis R, et al. Syncope may occur during automatic cardioverter defibrillator shocks in patients whose initial presentation of ventricular tachycardia was presyncope: Implications for driving, (abstract) PACE 1991; 14:721. 2. Dreifus LS, Zinberg A, Hurzeler P, et al. Transtelephonic monitoring of 25,919 implanted pacemakers. PACE 1986; 9;371-378. 3. Parsonnet V, Crawford CC, Bernstein AD. The 1981 United States survey of cardiac pacing practices. J Am Coll Cardiol 1984; 3:1321-1332. 4. Feldstein JS, O'Connor RE, Henry J, et al. Transtelephonic defibrillation. Ann Emerg Med 1990; 19:1367-1370. 5. Gessman LJ,, Raman SY, Janeira L, et al. Transtelephonic ECG-heepergram telemetry: A new device and method for implanted defihrillator follow-up, (abstract) PACE 1991; 14:718.
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Lyons C, Schroeder P. Shankar K, et al. Transtelephonic monitoring of a tachycardia-terminating pacemaker. PACE 1984; 7:34-36. Steinberg JS, Sugalaski JS. Cardiac rhythm precipitating automatic implantable-cardioverter defibrillator discharge in outpatients as detected from transtelephonic electrocardiographic recordings. Am ] Cardiol 1991; 67:95-97. Porterfield JG, Porterfield IM, Bray L, et al. A prospective study utilizing a transtelephonic electrocardiographic transmission program to manage patients in the first several months post-ICD implant. PACE 1991; 14:308-311. Fogoros RN, Elson JJ, Bonnet CA. Actuarial incidence and pattern of occurrence of shocks following implantation of the automatic implantable cardioverter defibrillator. PACE 1989; 12;1465-1473.
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