SHORT SERIES REPORT Runaway pacemaker: A forgotten phenomenon? Daniel F. Ortega, M. Victoria Sammartino*, Graciela M.M. Pellegrino, Luis D. Barja, Gaston Albina, Eliseo V. Segura, Roberto Balado, Ruben Lain ˜o, Alberto G. Giniger Instituto Cardiovascular de Buenos Aires, Electrofisiologı´a, Blanco Encalada 1543, DCO 1428 Buenos Aires, Argentina Submitted 21 January 2005, and accepted after revision 1 June 2005 Available online 8 September 2005 KEYWORDS failure of capture; battery depletion; runaway Abstract Runaway is an uncommon pacemaker dysfunction, characterized by fast and erratic spikes at non-physiological rates. This infrequent but potentially lethal failure mode may be related to low battery voltage. Four single chamber pacemaker patients were analyzed (Medtronic Minix ST 8330, Minneapolis, MN, had been implanted in two patients and two CPI Triumph VR 1124, St Paul, MN, in the other two). They had been admitted because of presyncopal episodes. Typical high rate stimuli at 2000 ppm alternating with pacing at 60e65 ppm were recorded in all ECGs. Lead system tests were normal. The pulse generators had to be replaced. ª 2005 Published by Elsevier Ltd on behalf of The European Society of Cardiology. Introduction Pacemaker patient follow-up is recommended to be more frequent near replacement time to avoid generator failure due to low or depleted battery voltage. Runaway is a rare but dangerous phenomenon due to generator dysfunction which may be related to its late replacement and battery depletion. Low battery voltage can provoke low rate stim- uli, capture and sensing failures, mode changes and less frequently the runaway phenomenon. This event shows a typical ECG with captured beats alternating with non-captured high rate spikes. Fortunately, in these cases the patients displayed spontaneous rhythm. Runaway could have been avoided by timely pacemaker replacement [1]. Case 1 A Medtronic model Minix ST 8330 (Minneapolis, MN) was implanted in a 67-year-old patient in another * Corresponding author. Tel.: C54 1148635770; fax: C54 1147877500. E-mail address: [email protected](M.V. Sammartino). 1099-5129/$30 ª 2005 Published by Elsevier Ltd on behalf of The European Society of Cardiology. doi:10.1016/j.eupc.2005.06.004 Europace (2005) 7, 592e597 by guest on October 14, 2011 europace.oxfordjournals.org Downloaded from
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Europace (2005) 7, 592e597
by guest on October 14, 2011
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SHORT SERIES REPORT
Runaway pacemaker: A forgotten phenomenon?
Daniel F. Ortega, M. Victoria Sammartino*, Graciela M.M. Pellegrino,Luis D. Barja, Gaston Albina, Eliseo V. Segura, Roberto Balado,Ruben Laino, Alberto G. Giniger
Instituto Cardiovascular de Buenos Aires, Electrofisiologıa, Blanco Encalada 1543,DCO 1428 Buenos Aires, Argentina
Submitted 21 January 2005, and accepted after revision 1 June 2005Available online 8 September 2005
KEYWORDSfailure of capture;battery depletion;runaway
Abstract Runaway is an uncommon pacemaker dysfunction, characterized by fastand erratic spikes at non-physiological rates.This infrequent but potentially lethal failure mode may be related to low battery
voltage.Four single chamber pacemaker patients were analyzed (Medtronic Minix ST
8330, Minneapolis, MN, had been implanted in two patients and two CPI Triumph VR1124, St Paul, MN, in the other two). They had been admitted because ofpresyncopal episodes. Typical high rate stimuli at 2000 ppm alternating with pacingat 60e65 ppm were recorded in all ECGs. Lead system tests were normal. The pulsegenerators had to be replaced.ª 2005 Published by Elsevier Ltd on behalf of The European Society of Cardiology.
Introduction
Pacemaker patient follow-up is recommended tobe more frequent near replacement time to avoidgenerator failure due to low or depleted batteryvoltage.
Runaway is a rare but dangerous phenomenondue to generator dysfunction which may be relatedto its late replacement and battery depletion.
1099-5129/$30 ª 2005 Published by Elsevier Ltd on behalf of Thedoi:10.1016/j.eupc.2005.06.004
Low battery voltage can provoke low rate stim-uli, capture and sensing failures, mode changes andless frequently the runaway phenomenon.
This event shows a typical ECG with capturedbeats alternating with non-captured high ratespikes. Fortunately, in these cases the patientsdisplayed spontaneous rhythm.
Runaway could have been avoided by timelypacemaker replacement [1].
Case 1
A Medtronic model Minix ST 8330 (Minneapolis, MN)was implanted in a 67-year-old patient in another
institution in 1994 because of complete atrioven-tricular (AV) block, with no recent follow-up.
He was admitted to our Intensive Care Unitbecause of presyncopal episodes for 3 days.
He was alert, with an average heart rate of40 bpm, and his blood pressure was 130/80 mmHg.
The ECG showed a pacemaker rhythm at 60 ppmin VOO mode interrupted by repeated spike burstsat 2000 ppm of 3 s duration and progressivelydecreasing amplitude.
During bursts, atrial flutter was observed withan escape ventricular rhythm at 30 bpm.
Low blood pressure was observed during run-away episodes (Fig. 1).
Magnet manoeuvres did not provoke anychange.
The generator was interrogated by telemetry(Fig. 2) and showed VOO mode programmed at70 ppm. Battery depletion was detected: 1.83 V,an extremely low level, well below elective re-placement level [2,3]. A Medtronic model Thera SR8942 (Minneapolis, MN) was implanted to replacethe exhausted device. The lead system was re-tained because threshold and resistance valueswere in acceptable ranges.
Case 2
A VVIR, CPI model Triumph 1124 (St Paul, MN), wasimplanted in a 78-year-old patient in anotherinstitution in 1994 because of complete AV block,programmed at a low rate of 60 ppm.
This patient was admitted to our Intensive CareUnit because of presyncopal episodes, normoten-sive with an average heart rate of 40 bpm.
The ECG showed 2000 ppm spikes with decreas-ing amplitude without any ventricular capture, andan escape rhythm recorded at 40 bpm followed byisolated captured beats at 60 ppm (Fig. 3).
Magnetic manoeuvres did not provoke anychange.
Telemetric reports were not obtained due tolack of telemetric communication. The patient hadnot attended follow-up for 2 years.
Case 3
This case was referred by another institution andwas admitted to the Intensive Care Unit because ofsyncopal episodes and stroke. A Medtronic ST 8330
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Figure 1 Medtronic Minix ST 8330 patient ECG record. Starting with a pacing burst at approximately 2000 ppm forabout 3 s with decreasing amplitude and rate. Patient’s own rhythm, atrial flutter, with ventricular escape rhythmat 30 bpm. In the middle, three spikes are seen at 60 ppm in VOO mode, the first in ventricular refractory. Later,re-initiation of the phenomenon is shown.
Figure 2 Real time telemetry. Battery depletion detected at 1.83 V. Extremely low battery voltage.
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pacemaker (Minneapolis, MN) had been implanted8 years earlier because of complete AV block.
A typical high rate spike ECG alternating withcaptured beats at 60 ppm was recorded (Fig. 4).
Only the pacemaker was replaced as thresholdand resistance of the ventricular lead were normal.
Case 4
A 55-year-old woman with a history of aortic valvereplacement 24 years earlier, due to severe aortic
stenosis, required a VVIR pacemaker because ofcomplete AV block.
She had undergone five generator replacementsdue to depleted battery, the last in 1996.
She was admitted to our institution for dizzi-ness, presyncopal episodes, and fatigue. Her ECG(Fig. 5) showed a typical runaway phenomenon.The pacemaker was replaced by a Medtronic VVI.During her hospital stay, she presented a ‘‘Torsadede Pointes’’ episode that was successfully defib-rillated (Fig. 6).
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Figure 3 Triumph VR 1124 CPI pacemaker patient ECG recording. Spike burst at approximately 2000 ppm withdecreasing amplitude and frequency. The underlying rhythm is complete AV block with escape beats at 40 bpm.Captured beats at 60 ppm are observed in the middle of the strip. Re-initiation of the phenomenon is shown.
Figure 4 Medtronic Minix ST 8330 pacemaker patient runaway phenomenon. Continuous strip: at the top, somecaptured beats may be observed alternating with rapid, non-captured beats of irregular stimuli at 2000 ppm. Duringthis episode the patient’s spontaneous rhythm is shown. The sequence is randomly repeated.
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Discussion
A typical runaway ECG (Figs. 1, 3e5) shows in-termittent ventricular capture at a rate slowerthan normal, numerous spikes at a very high ratewith different voltages and often without capturebeats, simulating an ECG artifact.
Capture beat rate is low because this phenom-enon occurs at the end of pacemaker life withdepleted battery voltage.
High rate spikes fail to capture because of lowamplitude and due to the fact that at such very highrates the ventricle is refractory to many stimuli.
Two clinical aspects were important:
1. The patients survived because they were notpacemaker-dependent.
2. Runaway did not provoke any potentially lethalarrhythmias. The ‘‘torsade de pointes’’ episodein one patient was related to bradyarrhythmiaand not due to overstimulation.
This phenomenon is observed when electivereplacement is overdue and the battery had lowvoltage, well below the safety margin [4e6].
The runaway phenomenon was first described inexternal and internal pacemakers in 1970 and it is
one of the causes of sudden death due to pace-maker failure [1]. Interestingly, these findings hadalready been attributed to an electric circuitfailure, early in pacemaker implantation in Argentina[7,8].
However, in the last decade only isolated caseshave been published [9,10].
The most frequent causes of runaway areassociated with:
(a) Sudden failure in one of the pacemaker cir-cuits [3].
(b) Battery depletion.(c) Circuit destruction or deterioration due to
electric diathermy or therapeutic radiation [5].
Runaway was also described in implantablecardioverter defibrillator patients due to crystaloscillator failure [2].
Today, pacemakers and defibrillators havesecurity designed to prevent runaway: the pres-ence of a maximum rate, hermetic sealing, anda decrease in pulse amplitude at high rates withconcomitant loss of capture. Despite these meas-ures, correct performance of the pacemakerbelow the security battery voltage is not guar-anteed [5].
Figure 5 ECG showing pacemaker rhythm alternating with the patient’s own rhythm with different intervals. Afterthe first beat, a typical runaway phenomenon is observed with a 2100 ms pause and a subsidiary escape rhythm. Thefollowing paced beat is delivered without correct sensing. The last two paced beats have an interval of 1000 ms.
Figure 6 ECG shows a storm of ventricular fibrillation. Spikes with different intervals. Previously the patientpresented ventricular tachycardia (torsade de pointes) and had to be defibrillated.
Even though the potential runaway hazard isinduction of ventricular fibrillation or other ven-tricular arrhythmias, loss of capture and bradyar-rhythmias or asystole in pacemaker-dependentpatients must also be considered.
The patients in this report did not have frequentfollow-up visits after implantation. In fact, it wasimpossible to determine the presumed replace-ment period.
Patients were almost asymptomatic at rest so noactive measure was taken at day 1. Pacemakerswere replaced on the day after admission. Themost appropriate behaviour should have beenurgent pacemaker removal because, as mentionedearlier, during runaway periods ventricular ar-rhythmias might occur. Furthermore, intermittentcapture could induce subsidiary foci suppressionby overdrive pacing and the bradycardia in thecomplete heart block can provoke ‘‘torsade depointes’’.
This potentially lethal phenomenon can beavoided by having appropriate follow-up. We pre-sume that there might have been other caseswhich were not identified because their firstepisode was lethal.
Conclusions
The runaway phenomenon is associated with verylow battery voltage together with late pacemakerreplacement.
It is a potentially lethal clinical entity.
Few reports do not mean an absence of thisphenomenon.
Appropriate follow-up programmes will preventfuture pacemaker failures.
References
[1] Furman S, Escher D. Principles and techniques of cardiacpacing. New York, NY: Harper and Row; 1970. p. 101e2.
[2] Mickley H, Anderson C, Nielson H. Runaway pacemaker:a still existing complication and therapeutic guidelines.Clin Cardiol 1989;12:412e4.
[3] Solow E, Bacharach B, Chung EK. Runaway pacemaker.Unpredictable pacemaker failure. Arch Intern Med 1979;139:1190e1.
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[5] Katzenburg CA, Marcus F, Heusinkveld RS, et al. Pacemakerfailure due to radiation therapy. Pacing Clin Electrophysiol1982;5:156e9.
[6] Vijayaraman P, Vaidya K, Kim SG, Gross JN, Ferrick KJ,Palma E, et al. Runaway pulse generator malfunctionresulting from undetected battery depletion. Pacing ClinElectrophysiol 2002;25:220e2.
[7] Posse R, Bein IJ, D’Aiutolo R. Arritmias cardıacas enpacientes con marcapaso electronico implantado. Rev ArgCardiol 1967;34:47e9.
[8] D’Aiutolo R, Posse R. Tratamiento de las arritmiascardıacas. BsAs Argentina: Cabrera y Rey editores; 1968.p. 69e71.
[9] Bohm A, Hajdu L, Pinter A, Duray G, Preda L. Runawaysyndrome and intermittent nonoutput as manifestations ofend of life of a VVI pacemaker. Pacing Clin Electrophysiol2000;23:2143e4.
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