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EDITORIAL COMMENT

Insights Into Defibrillator ShocksWhat OPTION Teaches Us*

Kenneth A. Ellenbogen, MD, Gautham Kalahasty, MD

T he mortality benefits of implantablecardioverter-defibrillators (ICD) are wellestablished and accepted (1,2). It is equally

well accepted that inappropriate therapy due toarrhythmia misclassification is associated withincreased morbidity and mortality (3). It is intuitiveto think that the use of an atrial lead will result in alower likelihood of inappropriate shocks. However,this assertion has proved difficult to validate.Although it is not the objective of this editorial to pro-vide a comprehensive review of the publishedresearch, that cited is representative of the contradic-tory findings among studies showing both beneficialand detrimental impacts of dual-chamber deviceswith respect to risk for inappropriate shocks andmorbidity.

Does the use of an atrial lead reduce the risk forinappropriate shocks? In which patients is the use ofatrial leads justified, independent of the need foratrial pacing? These seemingly simple questions havecomplex and incomplete answers. The important trialreported by Kolb et al. (4) in this issue of JACC: HeartFailure sheds some light on these questions. It was aprospective, multicenter, single-blinded, parallel-group trial in which all patients received dual-chamber ICDs (OVATIO DR; Sorin Group, Milan,Italy) but were randomized to single-chamber ordual-chamber settings. In the single-chamber group,the acceleration, stability, and long cycle searchdiscrimination criteria were activated. Morphologic

*Editorials published in JACC: Heart Failure reflect the views of the

authors and do not necessarily represent the views of JACC: Heart Failure

or the American College of Cardiology.

From the Division of Cardiology, Department of Internal Medicine,

Virginia Commonwealth University, Richmond, Virginia. Dr. Ellenbogen

is a consultant for and has received honoraria from Boston Scientific,

Medtronic, and Biosense Webster. Dr. Kalahasty has received honoraria

from Boston Scientific.

criteria were not used. The dual-chamber settingsused the PARADþ algorithm to distinguish ventricu-lar arrhythmias from supraventricular arrhythmias.This proprietary algorithm is based on ventricularrate stability, rate-onset analysis, atrioventricularassociation analysis, long cycle search, and determi-nation of the chamber of origin (for 1:1 tachycardia).The time to first inappropriate therapy was markedlylonger in the dual-chamber group compared with thesingle-chamber group. There was no difference inall-cause death or cardiovascular hospitalization. Thedifference in the rates of inappropriate shocksbetween the 2 groups was primarily driven by sup-raventricular tachycardia–triggered inappropriateshocks (86.6% of all inappropriate shocks in thesingle-chamber group and 29.2% of inappropriateshocks in the dual-chamber group). Interestingly,25.5% of all inappropriate shocks were driven by leadfailure or oversensing issues. Therefore, some inap-propriate therapies occurred because of the presenceof the atrial lead. Even with the use of atriallead–based discriminators, as many as one-third ofinstances of inappropriate therapies are still drivenby supraventricular arrhythmias. One of the mostimportant pieces of data from this study is thenumber needed to treat to prevent 1 instance ofinappropriate therapy: 17 dual-chamber devices needto be implanted to prevent 1 inappropriate shock. Therates of appropriate shock were equivalent in the 2groups. There are 2 additional important aspects ofthe study that may have bearing on its results. First,there was a higher-than-expected crossover ratefrom the single-chamber to the dual-chamber arm(39 patients). Eight patients crossed from the dual-chamber arm to the single-chamber arm because oflead issues or programming errors. Crossovers fromthe dual-chamber settings may have diluted thedifference between the groups. Second, patients withhypertrophic cardiomyopathy and patients who

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underwent cardioversion within the month priorto enrollment were excluded from the trial. Theexcluded patients are known to have a higher riskfor atrial arrhythmias. This likely explains the rela-tively lower rates of inappropriate therapy in bothgroups.

Placing this study in the context of previousstudies highlights the competing considerations forclinicians. As stated before, the number needed totreat to prevent 1 inappropriate shock is 17. Data fromthe National Cardiovascular Data Registry indicateabout 62% of patients who receive ICDs on the basisof primary prevention criteria receive dual-chamberdevices. Of these, 60% receive dual-chamberdevices in the absence of pacing indications (5).Implantation of a dual-chamber ICD has consistentlybeen shown to be associated with increasedin-hospital complications and mortality (5) as well ascomplications after discharge (5). Peterson et al. (5)analyzed a large cohort of patients from theNational Cardiovascular Data Registry and found thatthe incidence of cardiac tamponade was twofoldhigher in patients receiving dual-chamber ICDscompared with single-chamber ICDs. Dewland et al.(6) found mechanical complications requiring systemrevision at 90 days to be significantly more fre-quent in the dual chamber cohort. Cost is also animportant consideration. Friedman et al. (7) esti-mated an immediate cost savings of $200 millionannually if single-chamber ICDs were implantedpreferentially over dual-chamber ICDs. This does notinclude costs associated with management of device-related complications.

Previous clinical trials have yielded contradictoryresults. In DATAS (Dual Chamber and Atrial Tachy-arrhythmias Adverse Events Study), the use of acomposite end point and a limited follow-up periodlimited the applicability of its findings. The compos-ite end point of clinically significant adverse eventsfavored dual-chamber devices over single-chamberdevices (8). Interestingly, 2 or more inappropriateshocks were more likely to occur with dual-chamberdevices. Weeke et al. (9) studied data from theDanish ICD Register and found the occurrence ofinappropriate shocks was higher in patients withdual-chamber ICDs compared with single-chamberdevices. This study was limited by its observationalnature and nonstandardized device programming.More recently, a prospective, randomized study byFriedman et al. (6) showed no improvement in therate of inappropriate shocks with the use of dual-chamber devices. The study was limited by itsrelatively small size (100 patients). In addition, aretrospective study of the ICD arm of the MADIT-CRT

(Multicenter Automated Defibrillation Trial–CardiacResynchronization Therapy) showed no significantdifference in appropriate therapy in patients treatedwith single- versus dual-chamber ICDs (10).

Device programming is also an important deter-minant of risk for inappropriate therapy. In an anal-ysis of the French OPERA registry, Leenhardt et al.(11) found that 50% of first inappropriate shocks couldhave been avoided with more optimal programming,including disabling Sustained Rate Duration (BostonScientific, Natick, MA), adjusting the atrial blankingperiod, and programming the ventricular fibrillationzone to a higher rate. The importance of device pro-gramming is also highlighted in recent trials such asMADIT-RIT (Multicenter Automated Defibrilla-tion Trial–Reduction in Inappropriate Therapy) andADVANCE III (Avoid Delivering Therapies for Non-sustained Arrhythmias in ICD Patients). In MADIT-RIT, increasing the ventricular fibrillation detectionrate to 200 beats/min or extending the initial detec-tion duration was associated with reductions inthe first occurrence of inappropriate therapy (12).In the ADVANCE III trial, the reduction in inappro-priate therapies (part of a composite end point) wasassociated with extending the initial detection inter-val and allowing antitachycardia pacing duringcharging (13).

Another important variable to consider is the utilityof the atrial lead in diagnosing, treating, or preventingatrial fibrillation (AF). Friedman et al. (7) found thatthe use of a dual-chamber ICD led to the detection ofnew AF in 24% of patients compared with 0% amongpatients with single-chamber devices. This, of course,has implications for anticoagulation and strokeprevention. Furthermore, a subanalysis of DATASrevealed that dual-chamber ICDs were associated witha reduced incidence of a clinical end point composedof permanent AF, AF-related hospitalizations, andcardiac embolic events (14). Despite these intriguingresults, there is not enough information to recommenddual-chamber ICDs on the sole grounds of AF detectionor prevention.

As with most therapeutic options in medicine, thequestion is not which therapy is best. Rather, it iswhich therapy is better for a given patient. This isequally true for high-voltage ICD therapies. TheOptimal Anti-Tachycardia Therapy in ImplantableCardioverter-Defibrillator (ICD) Patients WithoutPacing Indications study supports the concept thatwith careful programming and patient selection, thelikelihood of inappropriate shocks in an individualpatient can be reduced by the presence of an atriallead. However, a number needed to treat of 17 makesit difficult to recommend dual-chamber devices in

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all patients. The uniqueness of the present study’scontribution is its relatively long follow-up periodand its per patient analysis. Although it can be arguedthe findings of this study are limited to Sorin ICDs,equivalent (or similar) discriminators are available foreach of the other 4 manufacturers. Nonetheless,extrapolation of these findings to other manufac-turers’ algorithms and devices is uncertain.

Does the addition of an atrial lead decrease therisk for inappropriate shocks from supraventriculararrhythmias? The answer is probably yes, withappropriate programming. In which patients is the

implantation of a dual-chamber ICD justified? Thisshould be the focus of future studies. Until then,dual-chamber ICDs cannot be recommended to allpatients indicated for ICDs, and clinicians remaincharged with the duty of patient selection and(equally important) optimal, individualized pro-gramming guided by current research.

REPRINT REQUESTS AND CORRESPONDENCE: Dr.Kenneth A. Ellenbogen, Medical College of Virginia,PO Box 980053, Richmond, Virginia 23298-0053.E-mail: kellenbogen@mcvh-vcu.edu.

RE F E RENCE S

1. Moss AJ, Zareba W, Hall WJ, Klein H, et al., forthe Multicenter Automatic Defibrillator Implanta-tion Trial II Investigators. Prophylactic implanta-tion of a defibrillator in patients with myocardialinfarction and reduced ejection fraction. N Engl JMed 2002;346:877–83.

2. Bardy GH, Lee KL, Mark DB, et al., for theSudden Cardiac Death in Heat Failure Trial (SCD-HeFT) Investigators. Amiodarone or implant-able cardioverter-defibrillator for congestive heartfailure. N Engl J Med 2005;352:225–37.

3. Poole JE, Johnson GW, Hellkamp AS, et al.Prognostic importance of defibrillator shocks inpatients with heart failure. N Engl J Med 2008;359:1009–17.

4. Kolb C, Sturmer M, Sick P, Reif S, et al.Reduced risk of inappropriate ICD shocks withdual-chamber therapy compared with single-chamber therapy-results of the randomizedOPTION study. J Am Coll Cardiol Heart Fail 2014:00:000–000.

5. Peterson PN, Varosy PD, Heidenreich PA, et al.Association of single- vs dual-chamber ICDs withmortality, readmissions, and complications amongpatients receiving an ICD for primary prevention.JAMA 2013;309:2025–34.

6. Dewland TA, Pellegrini CN, Wang Y, et al. Dual-chamber implantable cardioverter-defibrillatorselection is associated with increased complica-tion rates and mortality among patients enrolledin the NCDR implantable cardioverter-defibrillatorregistry. J Am Coll Cardiol 2011;58:1007–13.

7. Friedman PA, Bradley D, Koestler C, et al. Aprospective randomized trial of single or dual-chamber implantable cardioverter-defibrillatorsto minimize inappropriate shock risk in primarysudden cardiac death prevention. Europace 2014;16:227–34.

8. Almendral J, Arribas F, Wolpert C, et al.Dual-chamber defibrillators reduce clinically sig-nificant adverse events compared with single-chamber devices: results from the DATAS (DualChamber and Atrial Tachyarrhythmias AdverseEvents Study) trial. Europace 2008;10:528–35.

9. Weeke P, Johansen JB, Jordensen OD, et al.Mortality and appropriate and inappropriate ther-apy in patients with ischaemic heart disease andimplanted cardioverter-defibrillators for primaryprevention: data from the Danish ICD Register.Europace 2013;15:1150–7.

10. Ruwald AH, Sood N, Ruwald MH, et al.Frequency of inappropriate therapy in patients

implanted with dual- versus single-chamber ICDdevices in the ICD arm of MADIT-CRT. J CardiovascElectrophysiol 2013;24:672–9.

11. Leenhardt A, Defaye P, Mouton E, et al. Firstinappropriate implantable cardioverter defibril-lator therapy is often due to inaccurate deviceprogramming: analysis of the French OPERA reg-istry. Europace 2012;14:1465–74.

12. Moss AJ, Schuger C, Beck CA, et al. Reduction ininappropriate therapy and mortality through ICDprogramming. N Engl J Med 2012;367:2275–83.

13. Gasparini M, Proclemer A, Klersy C, et al.Effect of long-detection interval vs standard-detection interval for implantable cardioverter-defibrillators on antitachycardia pacing and shockdelivery: the ADVANCE III randomized clinical trial.JAMA 2013;309:1903–11.

14. Ricci RP, Quesada A, Almendral J, et al. Dual-chamber implantable cardioverter defibrillatorsreduce the clinical adverse events related to atrialfibrillation when compared with single-chamberdefibrillators: a subanalysis of the DATAS trial.Europace 2009;11:587–93.

KEY WORDS defibrillation, pacing, shock,survival, tachyarrhythmias