Inappropriate shocks from implantable cardioverter-defibrillators (ICDs) may occur for many
reasons. Inappropriate shocks are not simply painful inconveniences for patients; they also
may result in the need for further operative procedures, and sometimes even death. Herein, we
report the case of a patient who after upgrade of an ICD to a cardiac resynchronization
therapy-defibrillator device (CRT-D), returned with multiple shocks due to altered sensing and
defibrillation polarities that resulted from actual physical reversal of the distal (&#8211;) and proximal
(+) lead terminals in the header of the device

Dougherty, Anne H.

Francisco, Gregory M.

Kantharia, Bharat K.

Sharma, Saumya

English

Via Medica Journals

www.cardiologyjournal.org 473CASE REPORTCardiology Journal2009, Vol. 16, No. 5, pp. 473–476Copyright © 2009 Via MedicaISSN 1897–5593Address for correspondence: Bharat K. Kantharia, MD, FRCP, FAHA, FACC, FESC, Division of Cardiology, The Universityof Texas, Medical School at Houston, 6431 Fannin Street, Suite MSB 1.246, Houston, Texas 77030, USA, tel: (713) 500 6590,fax: (713) 500 6556, e-mail: Bharat.K.Kantharia@uth.tmc.eduReceived: 12.10.2008 Accepted: 12.01.2009Multiple shocks after upgrade of an implantablecardioverter-defibrillator to a cardiacresynchronization therapy-defibrillator deviceGregory M. Francisco, Saumya Sharma, Anne H. Dougherty, Bharat K. KanthariaDivision of Cardiology, University of Texas, Medical School at Houston, Houston, Texas, USAAbstractInappropriate shocks from implantable cardioverter-defibrillators (ICDs) may occur for manyreasons. Inappropriate shocks are not simply painful inconveniences for patients; they alsomay result in the need for further operative procedures, and sometimes even death. Herein, wereport the case of a patient who after upgrade of an ICD to a cardiac resynchronizationtherapy-defibrillator device (CRT-D), returned with multiple shocks due to altered sensing anddefibrillation polarities that resulted from actual physical reversal of the distal (–) and proxi-mal (+) lead terminals in the header of the device. (Cardiol J 2009; 16, 5: 473–476)Key words: implantable cardioverter-defibrillator, cardiac resynchronizationtherapy, heart failure, shocksIntroductionIn recent years, with the establishment of therole of implantable cardioverter-defibrillators(ICDs) for secondary prevention of sudden cardiacdeath (SCD) in the survivors of cardiac arrest, andfor primary prevention of SCD in select patientswith ischemic and non-ischemic cardiomyopathy,the number of ICD implantations has increased.Because of improvements in survival andheart failure status, ICDs incorporated in cardiacresynchronization therapy devices (CRT-D) arenow also considered and implanted in patients withsevere congestive heart failure and cardiac dyssyn-chrony. Additionally, ICDs have been shown to playan important role in the prevention of SCD in se-lect patients with ’inherited‘ cardiac arrhythmic sub-strates. In spite of improvements in implantationmethodology and device technology, because of theincreased number of implantation of ICDs, the in-cidence of device-related complications may yet risefurther.One of these complications, inappropriateshocks, may occur due to many reasons. These in-clude misinterpretation of supraventricular tachy-cardia as ventricular tachycardia, intracardiac over-sensing (P-wave oversensing, R-wave doublecounting, T-wave oversensing), extracardiac over-sensing (pectoral or diaphragmatic myopotentials),lead or connector problems (lead fracture, loose set-screw), or external noise from electromagnetic in-terference. While some of the causes of ICD mal-function may result from the software or randomcomponent failure, some may occur due to opera-tor error at the time of implantation. Unfortunate-ly, such an error may not become evident until latein the clinical course, and may often be picked upby a different operator/s at a different center.Here, we report the case of a patient who afterupgrade of an ICD to a CRT-D device returned withmultiple shocks due to altered sensing and defibril-lation polarities that resulted from actual physicalreversal of the distal (–) and proximal (+) lead ter-minals in the header of the device.474Cardiology Journal 2009, Vol. 16, No. 5www.cardiologyjournal.orgCase reportA 74 year-old man with ischemic cardiomyopa-thy who had undergone dual chamber ICD implan-tation four years ago presented to the hospital afterreceiving an ICD shock. He had not been followedup after his initial procedure. On interrogation, thedevice (Model 1853, Guidant-Boston Scientific,USA) was found to have delivered an appropriateshock for sustained ventricular tachycardia, eventhough surprisingly the battery had reached end-of-life status 13 months before presentation. Giv-en his persistent NYHA class III heart failure symp-toms, baseline left bundle branch block, and dimi-nished left ventricular ejection fraction of 30%, heunderwent an attempted upgrade to a CRT-D. Thecoronary sinus lead placement was unsuccessful,and hence the patient underwent surgical epicar-dial lead placement three days later.The new system thus comprised the followingcomponents: a previously implanted right atrial lead(model 4086), a previously implanted right ventricu-lar (RV) lead (model 0158), a new generator (mod-el H217 Contak Renewal), and a new left ventricu-lar lead (model 4047). All of these were manufac-tured by Guidant-Boston Scientific, USA. With thissystem, at the time of the surgery, during defibril-lation threshold (DFT) testing, defibrillation wassuccessfully accomplished with 25 J, providinga reasonable 10 J safety margin. The pacing thresh-old, sensing threshold, pacing impedance, and thehigh voltage (HV) shock impedance of the RV leadwere 0.8 V at 0.5 ms, 16.0 mV, 500 W, and 36 W re-spectively. After a satisfactory post-operativeclinical course and pre-discharge interrogation ofthe ICD for its appropriate function, the patient wasdischarged. As a routine post-operative instruction,the patient was advised to limit left arm movement,especially at the shoulder and to avoid lifting heavyobjects for at least ten days.He returned to the hospital six weeks latercomplaining of recurrent shocks from the ICD. Eachshock occurred with left arm movement, predomi-nantly when scratching the right side of the abdo-men with his left hand. Interrogation of the devicedemonstrated many diverted charges, as well as11 delivered shocks (Fig. 1). The pacing and sens-ing thresholds data and the pacing and shock coilsimpedances were all unchanged from the implantdata. The findings on the intracardiac electrograms(EGMs) recorded during the shocks were repro-duced with the left arm movement at the bedside.Chest X-ray did not demonstrate any apparent con-ductor or lead fracture.The patient returned to the electrophysiologylaboratory for further examination and potentialrevision of the system. The RV lead appeared in-tact. However, the proximal (+) superior vena cavaand the distal (–) RV high voltage lead terminalswere found to be reversed in the header of the ICD.Figure 1. Interrogation of the defibrillator shows stored intracardiac electrograms (EGMs) of the event. The EGMs arerecorded from the right atrial (RA) channel (top), the right ventricular (RV) pace/sense channel (middle), and the highvoltage (HV) shock coil channel (bottom). The device misinterprets high frequency low voltage noise as ventricularsensed (VS), ventricular tachycardia (VT) and ventricular fibrillation (VF) events. When the therapy criteria for VF aremet, the device charges (Chrg) and delivers shock (shock).475Gregory M. Francisco et al., Multiple shocks after upgrade of an ICDwww.cardiologyjournal.orgIt is also worth noting that the words ‘proximal’ and‘distal’ on this four year old lead were difficult toread. Due to the battery drain from the multipleshocks and diverted charges, a new CRT-D devicewas implanted as recommended by the manufactur-er. The patient did well post-operatively and had nofurther inappropriate shocks or device malfunctionduring a follow-up period of six months.DiscussionFor pacemakers and ICDs to function normal-ly, it is important that they appropriately sense anddetect intracardiac electrical potentials. Errors insensing function of the devices leading to eitherwithholding or delivery of therapy are still causesof concern, despite advances in device technology.ICD malfunction may be due to oversensing of int-racardiac events such as R-wave double counting,T-wave oversensing and/or oversensing of extrac-ardiac potentials such as pectoral or diaphragmaticmyopotentials or external noise from electromag-netic interference, resulting in inappropriateshocks. Sensing failure may also result from leador connector problems, for example coil fracture ora loose set-screw.Pertinent to our case, normal RV lead parame-ters made the possibility of lead fracture unlikely.The presence of high frequency, low-amplitudenoise with arm movement raised the suspicion ofmyopotential oversensing. Diaphragmatic myopo-tential oversensing is more common during peri-ods of straining or valsalva maneuvers, while armmovement makes pectoral myopotential oversens-ing more likely.In our patient’s ICD system, the RV lead wasan integrated bipolar lead. In this lead, bipolar sens-ing is accomplished from the tip of the RV lead tothe distal RV coil (black and white arrowheads re-spectively, Fig. 2A). The proximal (+) port in theheader is hardwired to the generator. Therefore,when the distal (–) and proximal (+) pins are physi-cally reversed in the ICD header ports, a broadunipolar sensing configuration occurs between thelead tip and the generator itself (black arrowheadand a broad white arrow respectively, Fig. 2B).In addition, unlike reversing the shocking po-larity with electronic programming (Fig. 2A), withphysical reversal of the pins in the header, a shock-ing configuration occurs which diverts energy awayfrom the ventricles, potentially leading to highDFTs or inability to defibrillate (Fig. 2B). This latterFigure 2. The chest X-ray shows cardiac resynchronization therapy-defibrillator device (CRT-D) system with the rightventricular (RV), left ventricular epicardial and the right atrial leads. As shown in (A), normal bipolar sensing vector isfrom the tip of the RV lead to the distal RV coil (black and white arrowheads respectively). With conventionalconnection, the defibrillator shock energy flows from the RV distal coil (–) to the superior vena cava (SVC) coil (+)and the generator (+) (black arrows). When the reversed lead polarity is ’programmed‘, the defibrillator shock energyflows from the SVC coil (–) and the generator (–) to the RV distal coil (+) (white arrows). In both cases, the shockenergy is focused in the ventricle. As shown in (B), when the distal (–) and proximal (+) pins are physically reversedin the implantable cardioverter defibrillator header ports, a broad unipolar sensing configuration occurs between thelead tip and the generator (black arrowhead and a broad white arrow respectively), and the defibrillator shock energyflows from the SVC coil (–) to the generator (–) and to the RV distal coil (+) (black arrows).A B476Cardiology Journal 2009, Vol. 16, No. 5www.cardiologyjournal.orgpoint was reported by Maagh et al. [1] in a sim-ilar case involving a patient with a failed defibrilla-tion and inability to determine DFTs. Their casealso involved a Guidant-Boston Scientific ICD, asdid the other reports [2, 3]. However, a unique caseof repeated, inappropriate shock delivery due to ab-normal sensing of external noise resembling60-Hz alternating current on the sensing channelof the ICD that resulted from the reversal of thepins in the header in a Medtronic device has alsobeen reported [4].Inappropriate shocks are not simply a painfulinconvenience for patients; they may lead to theneed for further operative procedures, and rarelyeven death, as in the recent case reported byCatanchin et al. [5]. Troubleshooting ICD malfunctionrequires detailed analysis of all available data, in-cluding chest x-ray, programmer interrogation, andevaluation of clinical factors such as electrolyteabnormalities, presence of myocardial ischemia, etc.Clues to the diagnosis of our patient included thenormal lead parameters, the EGM appearance dur-ing the inappropriate shocks, and the ability to re-produce the finding with left arm movement. Thepresence of equal degrees of noise on both theshock coil and RV pace/sense channels with nor-mal RV pace/sense parameters and the pacing andHV impedances further suggest HV coil polarityreversal. In addition, one may see farfield P-waveson the RV lead due to the broad unipolar sensingconfiguration. Patients with this problem oftenpresent in the first month after implantation, whenthe incision has healed and they begin using theirarms more.ConclusionsOur case demonstrates the risk of myopoten-tial oversensing and inappropriate shocks in thesetting of inadvertent physical reversal of the dis-tal (–) and proximal (+) lead terminals of an inte-grated bipolar ICD lead. This problem should besuspected in the presence of inappropriate shocksearly after implant due to myopotential oversens-ing, especially when other lead parameters are nor-mal. In the future, this risk may be removed withthe use of a ’universal‘ IS-4 defibrillator lead com-prising only one terminal. In the meantime, vigi-lance at the time of device implantation, and moreso at generator change-outs where one may encoun-ter poor legibility of the manufacturer’s symbols andletters on older leads, is essential to avoid this com-plication.AcknowledgementsThe authors do not report any conflict of inter-est regarding this work.References1. Maagh P, Trappe H-J, Meissner A. Non-determinable defibrilla-tion threshold and inefficacy of implantable cardioverter/defi-brillator shocks due to defective connections of the defibrillatorlead terminals in the device header port. Europace, 2007; 9:1161–1162.2. Jeevanantham V, Levine E, Budzikowski A, Shah AH, Daubert JP.Defibrillation coil reversal: A rare cause of abnormal noise andinappropriate shocks. Pacing Clin Electrophysiol, 2008; 31:375–377.3. Karanam S, John R. Inappropriate sensing of pectoral myopoten-tials by an implantable cardioverter defibrillator system. PacingClin Electrophysiol, 2004; 27: 688–689.4. Garg A, Wadhwa M, Brown K et al. Inappropriate implantablecardioverter defibrillator discharge from sensing of externalalternating current leak. J Interv Card Electrophysiol, 2002; 7:181–184.5. Catanchin A, Anderson L, Jones S, Ward D. When life-savingdevices terminate life. J Cardiovasc Electrophysiol, 2008; 19:316–318.

Multiple shocks after upgrade of an implantable cardioverter-defibrillator to a cardiac resynchronization therapy-defibrillator device

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Multiple shocks after upgrade of an implantable cardioverter-defibrillator to a cardiac resynchronization therapy-defibrillator device

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