Troubleshooting implantable cardioverter
Contents
1. eas oo gt on on On the other hand multiple shocks are more often classified as inappropriate The experience of receiving multiple shocks during consciousness is extremely distressing for both patients and wit nesses and warrants extensive clinical evaluation to reveal the possible cause and to reprogram the device or take other necessary measures to prevent future inappropriate shock episodes Therefore patients presenting after multiple shocks should always be advised to have their ICD interrogated 2 a 4 wyj 1 1 1 7 2 4 19 9 5 Ea 0 oo H 34 9J whereas patients who received a single shock can generally be reassured How does the ICD decide to deliver a shock All devices use the signal rate recorded by the right ventricular lead as the first detection criterion In order to be declared an arrhythmia a specified number or percentage of sensed events must occur at a rate higher than the programmed cut off rate These sensed events may originate from a real Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 Downloaded from heart bmj com on 9 June 2009 Education in Heart Figure 2 Causes for inappropriate shocks with typical examples continued E Source of electromagnetic interference EMI inside the body oversensing of diaphragmatic potentials 2 og The implantable 2 3 cardioverter defibrillator a gt ICD criteria for initial 5 giz ventricular fibrillation VF 5332. Impedance Actual Rate 158 min i Raber Screen Boley cease hey P Zoom In J Zoom Out Intrinsic Parameters Normal Replay Rhythm I0 Lower Rate Limit 68 min 1 Daily Events Max Sensor Rate oe min 1 Measurement Paced Accelerometer Sensed o Activity Threshold VIR Post shock Ss Reaction Time ss sec Response Factor T Recovery Time SE min Snapshot Viewer Trending Setup E amp F J Retrieve System Quick Tachy Brady Setup Therapy EP Summary Check Parameters Parameters History Test Sep 24 2007 10 15 19 B 9966 Software version 4 0 Copyright Medtronic Inc 2002 VT VF episode 26 Report Page 1 ID Date time Type V cycle LastRx Success Duration 26 Sep 23 16 19 00 VT 400 ms VTRx1 Yes 10 sec e V V OA A VF 330ms FVT 370ms VT 440ms 9000 Burst 1700 1400 i a Pri o 09000900 pooogood 00000 0 go co o mS Do2 g 804 z 4 wot ee ece ee eee a E 600 2 4 400 sonce coe ceed 200 r T T T T T T T T T T T T T T T T T T T T T T T T T ji i T T T T T T T T 30 25 20 15 10 5 0 5 10 15 Time s 0 detection These high frequency signals typically start to show some time after an intrinsic or paced beat The algorithm of increasing sensitivity which is typical for ICDs auto gain sensitivity allows sensing of the low amplitude sig
3. Correspondence to Dr Martin J Schalij Department of Cardiology Leiden University Medical Center PO Box 9600 2300 RC Leiden The Netherlands m j schalij lumc nl Downloaded from heart bmj com on 9 June 2009 ARRHYTHMIAS Troubleshooting implantable cardioverter defibrillator related problems Lieselot van Erven Martin J Schalij Since its introduction now more than 20 years ago the implantable cardioverter defibrillator ICD has evolved from a non programmable committed device into a sophisticated multi programmable multi functional device with exten sive diagnostic and therapeutic options The more recent combination with cardiac resynchronisation therapy CRT further expanded its use to selected patients with severe symptoms of heart failure and left ventricular dyssynchrony at risk of sudden cardiac death Whereas ICD technology developed rapidly endocardial ICD leads consisting of an integrated pace sense and shock electrode positioned in the right ventricle remained essentially unchanged after their introduction in the late 1980s aside from a reduction in diameter In the early years ICD implantation was a major surgical procedure associated with significant morbidity and mortality necessitating a thoracot omy to place the epicardial leads and patches and an abdominal incision to insert the bulky first generation device With the introduction of endo cardial shock electrodes and the significant reduc
4. In fig 7 a schematic example of one of these systems Home monitoring Biotronik Erlangen Germany is given At this time all telemonitoring systems provide a one way dataflow from patient to the hospital and it is not possible to program devices using the tele monitoring system PATIENTS WITH A DEVICE OR LEAD UNDER RECALL In recent years a significant number of so called dear doctor letters concerning a possible device or lead malfunction have been issued by almost all device companies To handle such a situation depending on the seriousness of the warning may be a challenging task as although these letters describe a potentially dangerous situation the resulting advice to the clinician is not always straightforward In the recent past this has resulted in large numbers of devices being replaced world wide whereas in retrospect it may have been sufficient to intensify follow up such large scale replacements may even have caused serious com plications To help the clinician among others the Heart Rhythm Society HRS and the European Heart Rhythm Association EHRA installed device com mittees which should issue a clinical advice in case of a device recall In general to deal with such a situation a few things are important for every implanting centre gt Keep track of the device patients implanted at the centre An up to date patient database will ensure patients involved in a recall are informed
5. has been shown to be very effective in terminating ventricular arrhythmias even in the cases of high ventricular rates Empirical programming for example 8 pulses at 88 of the VT cycle length Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 Downloaded from heart bmj com on 9 June 2009 275 260 260 VF VF VF 207 148 VF VF 252 189 VF VF j 229 VF 166 262 230 VI F F VF V 273 182 VF VF 232 VF 221 VF 154 VF 189 VF 205 VF VF 248 VF VF VF ZS nin 1 E 3 g st jj 3 2 Sila 2 538 gt ZN age l j Delivered enpt Type Tine ps ed rapy 184 191 197 141 VF VF VF VF VF VF 137 143 176 VF VF VF VF 256 285 234 191 221 248 VF VF VF VF VF 150 156 266 211 VF VF VF Figure 6 Underdetection of polymorphic ventricular tachycardia due to rarely occurring rapid changes in intrinsic amplitude The sensitivity level auto adjusts but not fast enough resulting in underdetection of intrinsic events consequently intervals fall in a lower zone VS Thus the device is not coming to detection and does not deliver therapy divert reconfirm without tailoring of the ATP sequences has been shown to be safe and effective Therefore ATP should be programmed on even if its efficacy in the individual patient has not been assessed yet Further reduction of the number of shocks can be achieved by othe
6. or tool J Am Coll Cardiol 2004 44 95 8 Duru F Luechinger R Scharf C et a Automatic impedance monitoring and patient alert feature in implantable cardioverter defibrillator being alert for the unexpected J Cardiovasc Electrophysiol 2005 16 444 8 Vollman D Erdogan A Himmrich E et al for the SAFE Study Investigators Patient alert to detect ICD lead failure efficacy limitations and implication for future algorithms Europace 2006 8 371 6 Vollmann D Nagele H Scheuerte P et a for the European InSync Sentry Observational Study Investigators Clinical utility of intrathoracic impedance monitoring to alert patients with an implanted device of deteriorating chronic heart failure Fur Heart J 2007 28 1835 40 The largest study so far evaluating the predictive value of a diagnostic feature like intrathoracic impedance for decompensated heart failure implemented in one type of CRT D device Ypenburg C Bax JJ van der Wall EE et al Intrathoracic impedance monitoring to predict decompensated heart failure Am J Cardiol 2007 99 554 7 Complications associated the device replacement Gould PA Krahn AD Canadian Heart Rhythm Society Working Group on Device Advisories Complications associated with implantable cardioverter defibrillator replacement in response to device advisories JAMA 2006 295 1907 11 Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762
7. potential sensing setting the sensi tivity level at the lowest level can be helpful but as with T wave oversensing may compromise VF detection and appropriate therapy delivery Therefore increasing the mandatory detection time seems to be more logical advice If despite reprogramming the problem of oversensing dia phragmatic potentials is unsolvable lead reposi tioning may be a reasonable alternative Lead device related problems are frequent and may cause all kind of phenomena Lead fracture or connector problems give rise to make break contacts leading to intermittent high fre quency signals sometimes associated with postural changes and limited to the sensing electrogram Impedance may be within normal limits Shocks may ensue often multiple Isolation defects may lead to oversensing of signals and inappropriate therapy All extracardiac sources of oversensing in pacing dependent patients lead to the additional problem of pacing inhibition Special noise reduction modes implemented in modern devices are not always helpful in this respect In case of a pace sense problem implantation of an additional pace sense lead may overcome these problems In case of a structural problem of the lead lead replacement may become necessary How to reduce the number of appropriate shocks The delivery of appropriate shocks can in the case of a VT be reduced by programming antitachy cardia pacing ATP modes in different zones ATP
8. rate as opposed to for example an exercise induced sinus tachycardia The sudden onset criteria is effective in discriminating VT from sinus rhythm except in the case of only a minimal CL difference when for example during sinus tachycardia a VT is initiated or in case of slow VT This algorithm may lead to false positive as well as false negative therapy delivery decisions Patient tailored programming is thus mandatory to improve both sensitivity and specificity To reduce the chance of a VI going untreated a specified acceptance time for a sustained high ventricular rate can be programmed as an overriding algorithm sustained high ventricular rate However this feature in itself has disadvantages since it can lead to inappropriate shocks for example an appro priately withheld shock during sinus tachycardia will be delivered after expiration of the preset time interval On the other hand sustained high rate duration can also when a long duration has been programmed result in a potentially dangerous delay of therapy delivery Detection algorithms in implantable cardioverter defibrillators intended use Discrimination Algorithm weakness Single and dual chamber device Sudden onset Rate stability Morphology Wavelet Rhythm ID Dual chamber device Atrial ventricular rate Sinus rhythm vs VT VT starting during sinus tachycardia VT below cut off that accelerates AF vs VT Unstable VT Stable conducted AF All S
9. tion in size and weight of the devices the complexity of the implantation procedure was reduced significantly and currently most systems can be implanted in the catheterisation laboratory by the electrophysiologist under local anaesthesia However compared to the relative ease of the current implantation procedure follow up and troubleshooting of ICD patients has become a much more complicated and challenging process demanding extensive knowledge of cardiac electro physiology as well as a thorough understanding of the different features and algorithms incorporated in modern CRT ICDs Combined with the increasing number of ICD patients troubleshoot ing of ICD related problems has become a challenging task In this overview some of the most important device related problems will be discussed TROUBLESHOOTING POLICY Device related problems in ICD patients may vary from relatively simple sensing or pacing problems to life threatening episodes of inappropriate shocks or failure of shock delivery In analysing and solving ICD related problems it is important to Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 maintain a structured approach towards every patient presenting with possible device related issues ICD troubleshooting starts either when a patient with a device presents at the hospital with a possible device related complaint or when a regular technical follow up reveals a possible device devia tion In order to identi
10. 2006 48 330 9 Wathen M Implantable cardioverter defibrillator shock reduction using new antitachycardia pacing therapies Am Heart J 2007 153 S44 52 Standard programming of ATP was shown to reduce the number of appropriate shocks This reference gives a summary of the two painfree trials in which this has been clearly proven ATP before shock in the VF zone is being incorporated as a default programming in current ICDs Ferreira Gonzalez Dos Subira L Guyatt H Adjunctive antiarrhythmic drug therapy in patients with implantable cardioverter defibrillators a systematic review Eur Heart J 2007 28 469 77 Della Bella P Riva S Hybrid therapies for ventricular arrhythmias PACE 2006 29 S40 7 Doenst T Faerber G Grandinac S et a Surgical therapy of ventricular arrhythmias Herzschr Elektrophys 2007 18 62 7 Three overview papers on adjunctive therapies in ICD patients antiarrhythmic drug therapy ablation of ventricular arrhythmias and surgical therapy Singer I Al Khalidi H Niazi et a Azimilide decreases recurrent ventricular tachyarrhythmias in patients with implantable cardioverter defibrillators J Am Coll Cardiol 2004 43 39 43 Tandri H Griffith LS Tang T et a Clinical course and long term follow up of patients receiving implantable cardioverter defibrillators Heart Rhythm 2006 3 762 8 Becker R Rug Richter J Senges Becker JC et a Patient alert in implantable cardioverter defibrillators toy
11. HEART Data supplement References Rapid responses Email alerting service Topic collections Notes Downloaded from heart bmj com on 9 June 2009 Troubleshooting implantable cardioverter defibrillator related problems Lieselot van Erven and Martin J Schalij Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 Updated information and services can be found at http heart bmj com cgi content full 94 5 649 These include web only references http heart bmj com cgi content full 94 5 649 DC1 This article cites 21 articles 11 of which can be accessed free at http heart bmj com cgi content full 94 5 649 BIBL You can respond to this article at http heart bmj com cgi eletter submit 94 5 649 Receive free email alerts when new articles cite this article sign up in the box at the top right corner of the article Articles on similar topics can be found in the following collections Education in Heart 310 articles Drugs cardiovascular system 9790 articles Interventional cardiology 3122 articles Pacing and electrophysiology 503 articles Epidemiology 441 9 articles To order reprints of this article go to http journals bmj com cgi reprintform To subscribe to Heart go to http journals bmj com subscriptions gt Additional references are published online only at http heart bmj com content vol94 issued Department of Cardiology Leiden University Medical Center Leiden The Netherlands
12. T wave oversensing as a cause of inappropriate shocks is an important issue ICD specific char acteristics such as filter settings may make some patients more vulnerable to T wave oversens ing and inappropriate shocks Patient characteris tics like a high T wave amplitude a low R wave and younger age may contribute to this phenom enon T wave oversensing can be prevented by 655 Figure 5 Ventricular tachycardia The ventricular egrams lower channel are clearly faster than the atrial egrams middle channel There is an alternating ventricular cycle length with the cycle length of each second cycle falling below the cut off zone VS leading to non diagnosis of ventricular tachycardia Symptoms of dizziness or syncope may be the effect 656 Downloaded from heart bmj com on 9 June 2009 Education in Heart vs vs vs 492 yT 488 428 426 426 Marker channels programming the sensitivity level of the automatic gain control to a less sensitive level this however may increase the risk of underdetection of or delayed therapy for VF When T wave oversensing is unmanageable the only solution may be changing the device to another brand with more specific filtering to reject T waves R wave double counting another cause of inappropriate detection and therapy can be managed by either reprogramming the ventricular blanking period or by reducing the minimum sensitivity level or when the other options fail by lead r
13. VT vs VT Aberrant conduction Mismatching with template V gt A with VT Atrial undersensing with AT with 1 1 AV relationship Double tachycardia concurrent atrial and ventricular tachycardia Misinterpretation of AV and VA relationship AF atrial fibrillation AT atrial tachycardia AV atrioventricular SVT supraventricular tachycardia VA ventriculoatrial VT ventricular tachycardia 652 Stability This algorithm is intended for discrimination of fast conducted atrial fibrillation flutter from VT It is an effective discriminator except in the case of a relatively stable ventricular rate during atrial fibrillation which occurs more often at higher ventricular rates due to a limited absolute varia tion in RR intervals As with the onset algorithm stability may lead to both false positive and false negative declarations During atrial fibrillation with relatively stable RR intervals inappropriate therapy can be delivered false negative and with relatively unstable VTs therapy may inadvertently be inhibited false positive In this case an overriding algorithm using the elapse of time is useful to overcome the inappropriately inhibited therapy for unstable VT but will lead to more inappropriate therapy in the case of atrial fibrillation Electrogram morphology Morphology St Jude Medical St Paul Minnesota USA Wavelet Medtronic Minneapolis Minnesota USA single chamber ICD and Rhythm ID Boston Scie
14. a patient receiving multiple shocks is to avoid delivery of further shocks while conscious Thus depending on the haemodynamic and mental state of the patient the heart rhythm and the cause of the shocks sedation of the patient is usually helpful in achieving stress reduction If the patient s rhythm is supraventricular in origin it is sound to switch the ICD off either by using a programmer or a magnet The same holds true for all non tachycardia causes of shocks If necessary while the ICD is switched off shocks can still be delivered by the ICD using the emergency button present on the programmers of all manufacturers or by removing the magnet Management of the patient is more difficult when the patient s rhythm is ventricular in origin or when recurrent episodes of ventricular arrhyth mias occur The shocks are appropriate but at the same time a disruptive experience for the patient if conscious In the acute situation antiarrhythmic drug therapy can be effective such as the intravenous administration of amiodarone or procainamide B blocker treatment has been shown to be valuable as well When VTs still recur manual overpacing may be helpful Furthermore suppression of VT can be achieved in some patients by increasing the lower rate of the pacemaker Longer term management includes evaluation and treatment of the underlying cause such as worsening heart failure symptoms or ischaemia or more general causes such as hypert
15. ance of inappropriate shock delivery Awareness of risk factors for inappropriate shocks can help to prevent them by customising the programming of the ICD at implant For example a history of atrial fibrillation is associated with an increased risk for inappropriate shocks Also especially in young patients sinus rates during exercise may reach the arrhythmia detec tion zones easily and it is therefore important to adjust settings if necessary Theoretically the most effective way to avoid inappropriate shocks in these patients would be to program the ICD as a single zone device with a high rate cut off but obviously this is undesirable for safety reasons since ventricular arrhythmias may be missed However lowering the VF zone cut off rate will increase the number of inappropri ate shocks Therefore the best solution in patients with paroxysmal atrial tachycardia or expected fast sinus rates is multiple zone programming with implementation of discriminators in the lower two zones thereby allowing to program the cut off rate for the VF zone relatively high 210 220 beats min Delivery of shocks for non sustained VT or SVT can be delayed or even prevented by prolong ing the programmed time for the device to detect However it is important to realise that after the first shock the following shock s within a single episode when becoming committed cannot be avoided Inappropriate shocks for other reasons than tachycardia
16. cess the data through the internet GSM global system for mobile communications 658 arrhythmic drugs may help to lower the number of episodes Whereas the aforementioned arrhythmias will be apparent at interrogation of the device a VI with a cycle length below the cut off rate unless ongoing during clinical evaluation is less easily detectable since the detection criteria have not been met and no episodes will be stored However clues hidden in the Cardiac flash back Medtronic or the Trending Boston Scientific fig 4 help to reveal the arrhythmia Such relatively slow VTs particularly occur in patients with jeopardised myocardium using amiodarone to treat faster ventricular arrhythmias Although in general these problems can be solved by lowering the cut off rate in cases of extremely slow ventricular arrhythmias reprogramming is often not possible due to overlap with brady pacing settings or because the lowest programmable cut off rate is reached Boston Scientific 90 beats min Medtronic and Biotronik 100 beats min St Jude 102 beats min In that case additional anti arrhythmic drugs or ablation may be reasonable alternatives Rapidly conducted but well discriminated atrial arrhythmias may cause dizziness as well particu larly in patients with reduced left ventricular ejection fraction Drug therapy or His bundle ablation may resolve this issue Dizziness or even syncope may also occur in the ICD patient who is pacemak
17. d zones and the detection algorithms are and 2 programmable in the two lowest zones in case of To discriminate between SVTs and VTs various programming three different zones The highest algorithms have been developed with the intention programmable zone is meant to detect fast VT or VF to improve specificity for discrimination of VT from without any further discrimination to avoid unne SVT without compromising the sensitivity for cessary therapy delivery delay Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 651 Table 1 and weaknesses Downloaded from heart bmj com on 9 June 2009 Education in Heart Available algorithms include sudden onset sustained high rate duration rate stability and morphology wavelet rhythm ID capabilities for single and dual chamber devices whereas dual chamber devices can use additional information retrieved from the atrial lead like atrial to ventricular timing relationships All currently available algorithms have known limitations table 1 By combining some of these algorithms the amount of inappropriate inhibition or therapy delivery can be further reduced It is important to have knowledge and under standing of the incorporated automatic algorithms for discrimination of arrhythmias in order to apply them effectively Sudden onset The intended use of this algorithm is to discrimi nate sinus tachycardia from VT With the onset of a VI there is usually a sudden increase in ventricular
18. detection are met 8 out of aes 10 intervals classified as st fast but VF is not amp gee reconfirmed as the diaphragm potentials cease and the Duration is not met Duration is Chra programmed to 1 s VF therapy is not delivered Note that after the first intrinsic beat arrow the sensing of noise is reduced due to the auto f gain sensitivity see text g Ti for details F Atrial ay A arrhythmia with fast 3 conduction but initially not ajla 1 1 and a ventricular rate i aali i fulfilling the detection AN W We WV J l VW criteria followed by oan antitachycardia pacing ss es ies i tN e Si a gt sree rhre egret Thereafter the atrial i ast th fas iy si I fast k 5 gel tah yp BP th j arrhythmia is conducted 4 8 S a fe fl z g a a ae b ms 1 1 G Shock delivered g gy Ye fe te fe re Tl am he me me me during sinus tachycardia kh b s Bw amp Tt amp mm aed WA i fs w b em just above the cut off rate SIEEEIIS 3 for VF 188 beats min resulting in a ventricular tachycardia l I 3 2 g B 2 ni d s SB sea E Jj as 3 S Seg Fe 35 ire tachycardia either supraventricular tachycardia detection and treatment of VTs Current ICDs SVT or ventricular tachycardia VT but also can be programmed into three different cycle length from signals originating from another source figs 1 CL relate
19. e Most alerts are programmable on off except system alerts that convey debilitated functioning with respect to proper treatment of tachycardia The system alerts the patient with the intention that he she should contact the physician in case the programmed parameters are undesirable or the measured parameters are not within normal limits The time and character of the alerts and interval You can get CPD CME credits for Education in Heart Education in Heart articles are accredited by both the UK Royal College of Physicians London and the European Board for Accreditation in Cardiology you need to answer the accompanying multiple choice questions MCQs To access the questions click on BMJ Learning Take this module on BMJ Learning from the content box at the top right and bottom left of the online article For more information please go to http heart bmj com misc education dtl gt gt RCP credits Log your activity in your CPD diary online http www rcplondon ac uk members CPDdiary index asp pass mark is 80 EBAC credits Print out and retain the BMJ Learning certificate once you have completed the MCQs pass mark is 60 EBAC EACCME Credits can now be converted to AMA PRA Category 1 CME Credits and are recognised by all National Accreditation Authorities in Europe http Awww ebac cme org newsite hit men02 Please note The MCQs are hosted on BMJ Learning the best available learning website for
20. e study describes the causes of and solutions for oversensing by the ICD in a relatively large patient group leading to ICD interpreted arrhythmias Nanthakumar K Dorian P Paquette M et al Is inappropriate implantable defibrillator shock therapy predictable J Interv Card Flectrophys 2003 8 215 20 This is an interesting article on the predictability of shocks New York Heart Association functional class and prior atrial fibrillation predicted the occurrence of inappropriate shock Sacher F Probst V lesaka Y et a Outcome after implantation of a cardioverter defibrillator in patients with Brugada syndrome A multicenter study Circulation 2006 114 2317 24 20 21 22 Pinski SL Electromagnetic interference and implantable devices In Ellenbogen Kay Lau Wilkoff eds Clinical cardiac pacing defibrillation and resynchronization therapy Saunders 2007 1149 76 This book chapter provides a good and balanced overview of the nature and sources of electromagnetic interference with ICDs and of the measures that can be taken with patients exposed to it Kolb C Zrenner B Schmitt C Incidence of electromagnetic interference in implantable cardioverter defibrillators PACE 2001 24 465 71 Wilkoff BL Ousdigian KT Sterns LD et al A comparison of empiric to physician tailored programming of implantable cardioverter defibrillators result from the prospective randomized multicenter EMPIRIC trial J Am Coll Cardiol
21. ed by the device This information can also be used in combination with the above mentioned algorithms to enhance sensitivity and specificity of arrhythmia discrimi nation or it can be used for separate AV time relationship algorithms Weaknesses with these AV sequence time algorithms are 1 1 conducted atrial Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 Downloaded from heart bmj com on 9 June 2009 Education in Heart Figure 3 Schematic representation of the possible causes of shock delivery Shocks can be either delivered because of a tachycardia ventricular appropriate or supraventricular inappropriate or because of oversensing problems all inappropriate SVT supraventricular tachycardia VF ventricular fibrillation VT ventricular tachycardia tachycardias with prolonged AV time and VTs with 1 1 retrograde conduction Although no studies have been conducted to support this statement the value of the atrial lead information for the human interpretation of stored electro grams is significant particularly during the onset of the arrhythmia which device based algorithms currently do not take into account How to evaluate the appropriateness of a delivered shock ICDs are not perfect in their judgment of the perceived signals The annotated interval markers and other markers provide information and insight into the decision making process of the ICD However a careful review of stored electrogra
22. er dependent when the pacemaker is erroneously inhibited Treatment is guided by the cause of inhibition see sections above PALPITATIONS Although patients do not usually present com plaining of palpitations in an emergency setting like those with shocks dizziness and or syncope palpitations are a frequent complaint at regular ICD follow up Palpitations can be due to several reasons overlapping with those causing dizziness or syncope box 1 ICD interrogation will give more insight into the underlying cause since it may reveal the occurrence of irregular or fast atrial arrhythmias ventricular extrasystole or non sus tained VTs Sustained VTs with a cycle length below the cut off rate are especially difficult to diagnose when the VT is not ongoing during follow up The already mentioned Trending fea ture Boston Scientific may be helpful in revealing the arrhythmia The Flashback memory Medtronic stores the egrams preceding an episode or preceding interrogation If history is pointing in this direction the monitor zone can be adjusted to store these arrhythmias Particularly patients with single chamber ICDs may complain of palpitations at rest at times keeping them from their sleep caused by lower rate pacing Decreasing the lower rate of the pacemaker or lowering the B blocker dosage may resolve these complaints Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 Downloaded from heart bmj com on 9 June 2009 Troubles
23. evision change of lead position Electromagnetic interference EMI The potential sources of EMI are ubiquitous especially in the hospital for example electrocautery mag netic resonance imaging lithotripsy but also at work for example welding high voltage power source electric motors and in daily life for example metal detectors electronic article surveil lance devices cellular telephone The most frequent responses to EMI are inappropriate inhibition or triggering of pacemaker stimuli and spurious ICD tachycardia detection and inap propriate therapy The effects of EMI on pace makers and ICDs depend on the intensity of the electromagnetic field the frequency of the signal the distance and orientation of the device relative to the source device characteristics and patient factors Measures have been taken to make ICDs less susceptible for example by incorporating a filter The fear for EMI is high compared to the real clinical problem In fact EMI is only rarely a cause of inappropriate shocks The best way to avoid EMI related shocks device inhibition is to keep a sufficient distance from the EMI emitting source Good advice is essential and when indicated a field evaluation may be necessary to identify possible hazards However testing for EMI is not 100 conclusive PVC VT 1 492 424 424 426 Sensing of diaphragmatic potentials infre quently results in shock delivery In case of diaphragmatic
24. fy and solve the problem the device should be interrogated extensively and the retrieved data should be stored on disc to allow offline analysis and comparison with historical data After identification of the problem the possible cause is analysed Different methods of evaluation may be needed such as manipulation of the device observing the effect of postural changes and deep inspiration and expiration 12 lead electrocardio graphy a chest x ray and 24 h Holter monitoring Patients with an ICD related problem present with complaints which generally fall into one of the following four categories gt Shocks appropriate inappropriate or failure to deliver therapy gt Dizziness fainting gt Palpitations gt Alerts audible beeps or sensed vibrations originating from the ICD SHOCKS Whereas ICD therapy improves survival of selected patient groups and patients may have the feeling of being protected the actual delivery of shocks both appropriate and inappropriate may have signifi cant psycho sociological consequences Several studies have demonstrated that the occurrence of ICD shocks negatively influences patients sub jective feeling of physical and mental wellbeing This is caused by the fact that shock delivery is a traumatic physical experience and because of the psychological effect of confronting the patient with his her compromised physical status or with his her risk of developing life threatening a
25. hooting ICD related problems key points gt Implantable cardioverter defibrillator ICD troubleshooting starts when a patient presents with a possible device related problem or when technical follow up reveals a possible problem ICD troubleshooting should be performed in a structured manner following interrogation of the device and examining the patient Important issues include complaints of patient related to device activity device activity arrhythmia related or caused by malfunction of device or lead or both or related to an external source device activity caused by supraventricular or ventricular arrhythmia device activity appropriate or inappropriate device activity adjustment of settings necessary Patients with an ICD related problem present with complaints which generally fall into one of the following four categories shocks appropriate inappropriate or failure to deliver therapy dizziness fainting alerts audible beeps or sensed vibrations originating from the ICD ALERTS Most ICDs have alerts that notify the patient of undesired settings or electrical events of the ICD and or leads Recently Medtronic has intro duced a diagnostic feature intended to predict a forthcoming episode of heart failure box 2 7 The alerts produce audible signals Medtronic Boston Scientific or a vibrational sensation St Jude Alerts are repetitive discontinuous signals that can be programmed to a specified tim
26. hyroidism or a systemic infection 1 DIZZINESS AND SYNCOPE Dizziness is a well known frequently occurring symptom in patients with an impaired left ventricular function as in the majority of ICD patients Mild heart failure is associated with autonomic derangement especially weakening of the arterial baroreflex sensitivity with permanent activation of the sympathetic nervous system Dizziness is often distinct in these patients in whom the autonomic nervous system is further affected by heart failure medication History taking is helpful in differentiating this form of dizziness from other causes for dizziness and syncope in ICD patients box 1 To reveal a non arrhythmogenic origin of dizziness or syncope interrogation of the 657 Data transmission Event types Detection amp Therapy j Downloaded from heart bmj com on 9 June 2009 Education in Heart device may be helpful as these symptoms may be caused by arrhythmias also Dizziness or even syncope may also be caused by underdetection of ventricular arrhythmias Underdetection may occur when there is a variation in cycle length during VT and the cycle length alternates around the cut off rate of the detection zone fig 5 This may be solved by lowering the cut off rate It may also be caused by a variation in amplitude of the intracardiac signals as may occur during a poly morphic VT or VF fig 6 Committed shock delivery still a feature in mode
27. hythmics Versus Implantable Defibrillator trial impact of therapy and influence of adverse symptoms and defibrillator shocks Circulation 2002 105 589 94 These are two large studies in which the quality of life was assessed after ICD implant with a follow up of more than a year The occurrence of ICD shocks was associated with decreased mental wellbeing and increased patient concerns Dorian P Philippon F Thibault B et a for the ASTRID Investigators Randomized controlled study of detection enhancements versus rate only detection to prevent inappropriate therapy in a dual chamber implantable cardioverter defibrillator Heart Rhythm 2004 1 540 7 Theuns DA Rivero Ayerza M Boersma E et a Prevention of inappropriate therapy in implantable defibrillators a meta analysis of clinical trials comparing single chamber and dual chamber arrhythmia discrimination algorithms nt J Cardio 2007 April 17 Epub ahead of print Friedman PA McClelland RL Bamlet WR et a Dual chamber versus single chamber detection enhancements for implantable defibrillator rhythm diagnosis The Detect Supraventricular Tachycardia study Circulation 2006 113 2871 9 Three papers giving more insight into discrimination of SVT vs VT in single and dual chamber ICDs Rauwolf T Guenther M Hass N et al Ventricular oversensing in 518 patients with implanted cardiac defibrillators incidence complications and solutions Europace 2007 9 1041 7 This retrospectiv
28. medical professionals from the BMJ Group If prompted subscribers must sign into Heart with their journal s username and password All users must also complete a one time registration on BMJ Learning and subsequently log in with a BMJ Learning username and password on every visit Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 between alerts inform the physician or technician about its cause without interrogation of the device Instruction may be helpful and relatively easy Although the alerting systems have been shown to be valuable in many cases the sensitivity is limited Furthermore the alerts have an under estimated distressing effect on patients who generally feel well at the moment of the alert and do not anticipate being alerted Instruction does not eliminate all of the confusion and inconve nience coinciding with an alert Thus efforts should be made to avoid false negative alerts and when programming the alerts it is important to be aware of this effect and ensure the patient is well informed Presently remote monitoring systems are becoming available for evaluation of ICD lead systems which may replace the necessity of alerts in the future Monitoring systems allow system integrity checks usually on a daily basis Furthermore these systems allow continuous following of the clinical status of the patient which may help in the near future to prevent deterioration of the clinical status by timely interventions
29. ms is often mandatory to verify appropriateness and efficacy of therapy delivery The stored episode electrograms retrieved from a far field dipole are in general helpful for analysis especially when it is possible to compare these electrograms with a real time reference electrogram Furthermore stored electrograms can be used to analyse A V sequence and timing The first step in analysing a possible arrhythmic episode is to differentiate a real tachycardia SVT or VT from a device interpreted tachycardia figs 1 and 2 This is essentially carried out by analysis of stored episode signals and comparing these with the information as it is perceived by the ICD which is represented by the annotation markers A decision tree is shown in fig 3 Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 Inappropriately device interpreted tachycardia When the stored electrograms do not show a real tachycardia but the markers reveal that the device interpreted the signals as tachycardia the next step is to trace back the origin of the signals as intra or extracardiac figs 1 and 2 Intracardiac signals that may cause oversensing and false arrhythmia detection are usually the T wave or infrequently the P wave fig 1 panel A In both cases VI VF detection criteria are already met at relatively low heart rates since each heart cycle leads to two sensed signals T wave over sensing occurs more frequently during exercise Another phen
30. nals from the diaphragm This will lead to VF detection and therapy delivery unless the sensing level is suddenly reduced with a subsequent intrinsic beat or by release of the diaphragm As these myopotential related signals may also inhibit pacing when no intrinsic beat occurs as in patients with no or slow intrinsic rhythms a shock may follow Fortunately most patients relax at an earlier moment and the diaphragmatic potentials cease Myopotentials originating from the pectoral muscle may be sensed in case of an isolation defect of the pace sense lead part of the ICD electrode Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 Downloaded from heart bmj com on 9 June 2009 Appropriately device interpreted tachycardia When after an episode the retrieved signals are judged not to be due to oversensing but to an actual tachycardia further evaluation of the arrhythmia has to be performed to verify appro priateness of the shock since SVI VT discrimina tion algorithms are not always perfect This evaluation essentially follows the same algorithms that are described above However whereas the ICD starts applying the algorithm formulas after the criteria for initial detection are met the human interpretation has a wider scope and can start at the actual onset of the arrhythmia In certain ICDs Medtronic Boston Scientific this extra informa tion is graphically represented as the interval cycle length versus the time elapsed si
31. nce the onset of the episode fig 4 Other information can be retrieved by comparing the episode electrograms and annotations with data obtained at device examination For example the similarity of the morphology of an isolated ventricular extrasystole recorded by the shock electrode and the morphol ogy during VT may lead to the diagnosis Also the absence of retrograde conduction during ventricu lar pacing may help to reject the diagnosis of ventricular tachycardia when during tachycardia a 1 1 AV relation exist High ventricular rates during atrial fibrillation or atrial flutter are the most frequent cause of inappropriate detection and therapy fig 2 panel F Atrial fibrillation causes typically an unstable ventricular rate although this becomes less at higher ventricular rates as mentioned earlier but usually does not fulfil the sudden onset criterion Atrial flutter also results in unstable ventricular rates and is often clearly distinguishable in a dual chamber device unless 1 1 AV conduction occurs Sinus tachycardia fig 2 panel G is sometimes hard to differentiate from 1 1 conducted atrial tachycardia except for the gradual onset seen in sinus tachycardia The Flashback memory Medtronic or Trending feature Boston Scientific may provide helpful information to discriminate between the different supraventricu lar arrhythmias To distinguish a VI with 1 1 Box 1 Causes of dizziness syncope and palpitations Most ca
32. ntific Natick Massachusetts USA are features incorporated into the different devices to discriminate an SVT from a VT especially in single chamber devices that lack additional information retrieved from the atrial lead These algorithms are based on retrieving a template of the electrogram during baseline rhythm Morphology uses the near field rate electrogram derived from the small intracar diac bipole Wavelet uses the far field shock electrogram analysing the electrical activity between a shock electrode and the intracardiac electrode and taking the electrical axis into account Rhythm ID uses the far field shock electrogram aligned in time to the rate electro gram combining electrical axis and timing When an event is detected in the applied zone the morphology of each electrogram is compared to the baseline template and the percentage of match or mismatch is calculated The advantage of these algorithms is the independence of the atrioven tricular AV sequence and timing relationship No comparative studies on efficacy are however available Atrioventricular AV sequence timing algorithms Dual chamber devices enable the use of informa tion provided by the atrial lead If the ventricular rate exceeds the atrial rate V gt A the diagnosis is VT Comparison of atrial and ventricular rate during tachycardia can be used as an initial step in the decision tree or as an overrider after other algorithms have been appli
33. omenon which occurs infrequently in the current generation of ICDs is double counting of the R wave fig 1 panel B Oversensing of extracardiac signals can be easily recognised as high frequency low amplitude signals that are not related to the intrinsic electrical activity of the heart Electromagnetic interference from an external source such as a power drill fig 1 panel C usually has a more continuous character may be visible on several channels and can generally be tracked back by careful history taking Internal sources causing oversensing are signals produced in case of lead or connector related make break contacts fig 1 panel D Since these phenomena may occur intermittently impedance threshold and sensing parameters may be normal at the time of examination However pocket manipulation or postural changes may reveal changes in these parameters or may show noise on the real time intracardiac electrogram 653 Figure 4 A Trending Boston Scientific or B Cardiac flash back Medtronic revealing a ventricular rate under the detection zones 654 Downloaded from heart bmj com on 9 June 2009 Education in Heart A Tachy Mode Ea Back Fwd MonitortIherapy Utilities Profiles Print ECG 28 SEP 2667 14 19 54 175 Battery Status Intrinsic Amplitude Lead AE A ViTALITY2 ae gLead II Trending Sampled Every 16 sec 28 SEP 2007 14 36 58
34. quickly Furthermore an up to date database will make it easy to follow the performance of implanted devices and leads Preferably a nationwide database should be available 659 gt REF 1 660 Downloaded from heart bmj com on 9 June 2009 Education in Heart Follow the initial guidance of the company and adjust according to the final guidance by HRS or EHRA If a patient with a device or lead under recall presents with problems for example shocks investigate if the problem is related to the recall In the case of an unexpected death of a patient try to retrieve information from the device to establish the cause of death Inform the company that a device or lead related problem occurred This is the only way to obtain a reliable picture Competing interests In compliance with EBAC EACCME guidelines all authors participating in Education in Heart have disclosed potential conflicts of interest that might cause a bias in the article Dr Schalij and Dr van Erven received research grants from Boston Scientific Medtronic and Biotronik Dr Schalij received speaker fees from Boston Scientific and Biotronik Dr van Erven received speaker fees from Boston Scientific and Medtronic ERENCES Irvine J Dorian P Bakker B et a Quality of life in the Canadian Implantable Defibrillator Study CIDS Am Heart J 2002 144 282 9 Schron EB Exner DV Yao O et a for the AVID Investigators Quality of life in the Antiarr
35. r measures B blockers sotalol and amiodarone and other antiarrhythmic drugs are usually helpful although side effects may limit their use Azimilide was shown to be effective but is not clinically available yet In general it is of course important that in ICD patients with a low left ventricular ejection fraction other drugs Box 2 Events eliciting alerts in ICDs list not complete gt gt gt gt gt gt gt Battery voltage low Prolonged charge time Magnet applied or in neighbourhood Ventricular fibrillation VF detection off VF therapy partially programmed Electrical reset of system Lead impedance out of range pacing high voltage Pacing programmed to fixed rate Intrathoracic impedance change vv Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 Education in Heart such as angiotensin converting enzyme ACE inhibitors and diuretics are given In patients with recurrent VTs for which ICD therapy is delivered radiofrequency catheter abla tion may be an effective approach to reduce or abolish the number of VT episodes and ICD discharges acutely and in the long term If refractory to other treatment options surgical elimination of arrhythmogenic foci may be per formed usually in combination with other opera tive goals such as revascularisation surgical ventricular reconstruction and valvular repair How to deal with multiple shocks The first objective in the management of
36. rn ICDs may be used to solve this issue Adjustment of the sensitivity level or shortening of the detection time if possible may also be helpful to solve these problems Another reason for dizziness may be the occurrence of non sustained VTs that do produce symptoms but do not continue long enough to meet the programmed detection criteria of the device In the case of non sustained VT anti Home monitoring l Service centre M Atrial pacing impedance lt 250 ohm or gt 1500 ohm Ventricular pacing impedance lt 250 ohm or gt 1500 ohm Impedance of last shack lt 25 ohm or gt 110 ohm V 7 g g T gt V p 7 7 ERI Special implant status ind YT VF detection inactive VTL detected WT2 detected YF detected SVT detected 30 J shock ineffective Ventricular intrinsic rhythm lt 90 First mode switching since last follow up C First mode switching per day Epimode details Episode number Termination Durstion Detection in Redetection Delivered ATPs Delivered shocks SMART Remark Duration of mode switching gt 75 18h z Mean VES h gt 50 gt Figure 7 Example of a telemonitoring system Homemonitoring Biotronik The unit transmits data to a receiver which sends the data to a service centre through the GSM network From the service centre alerts in the case of preprogrammed deviations device or arrhythmias are sent to the treating physician who can ac
37. rrhyth mias In general most single shocks are appropriately and successfully delivered to terminate an episode of ventricular tachycardia fibrillation and because the ICD worked properly the patient may even be reassured 649 Figure 1 Causes for inappropriate shocks with typical examples A Non tachycardia Oversensing of P or T waves may result in shock delivery In this example oversensing caused the sensing of giant T waves and as a consequence the device is activated B Double counting of R waves starts with the appearance of frequency dependent bundle branch block resulting in incorrect ventricular fibrillation VF detection C Lead or connector problems may cause electrical noise resulting in device activation D Source of electromagnetic interference EMI outside the body the patient was installing a pump in a pool EMI may cause therapy delivery However EMI may also cause inhibition of a pacemaker 650 Downloaded from heart bmj com on 9 June 2009 Education in Heart Aaa VF a vifit a af ae at ag a aN lt 8 2R 23 23 23 28 TT I TT TT VY VT n no Nuo A e Nui Y LULO LUO LULO gt 7O gt gt n Ea Saat Spor Sor Sam VF detected Biotronik 2 1 0 3 43 9 9 1s g an 5 5 rs y oo u i 0 141 7 5 a Nae 1200 232 1 o j3 3 00 0 o io o 21 9J on ooe N Cal ouno gt jospa ne oo ouv
38. uses for dizziness and syncope may also give rise to palpitations gt Causes of dizziness and syncope undersensing of ventricular arrhythmias polymorphic ventricular tachycardia VT unstable VT around cut off rate VT below cut off rate non effective therapy non sustained VT gt Causes of palpitations atrial tachyarrhythmias frequent premature ventricular contractions PVCs ventricular pacing Heart 2008 94 649 660 doi 10 1136 hrt 2007 122762 retrograde conduction from a supraventricular tachycardia with 1 1 AV conduction both onset of the tachycardia and the morphology recorded with the far field dipole may be of help Lastly after a first unsuccessful shock in case of concurrent termination of the episode of VT SVT or device interpreted tachycardia an inappropriate second shock may be delivered This second shock is so called committed meaning that it is delivered without further pre evaluation for rea sons of safety to prevent underdetection and undertreatment of arrhythmias Commitment also starts when the first therapy of an episode has been diverted but the arrhythmia restarts before the episode has ended How to reduce the chance of delivering inappropriate shocks Since most inappropriate shocks are delivered for supraventricular arrhythmia and shocks have an important negative effect on the quality of life of patients all efforts should be undertaken to reduce the ch
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