Inappropriate ICD shocks in pediatrics and congenital heart disease patients: Risk factors and programming strategies Jason M. Garnreiter, MD,* Thomas A. Pilcher, MD, FHRS,† Susan P. Etheridge, MD, FHRS,† Elizabeth V. Saarel, MD, FHRS† From the *Saint Louis University School of Medicine, St. Louis, Missouri, and †University of Utah School of Medicine, Salt Lake City, Utah. BACKGROUND Inappropriate implantable cardioverter-defibrillator (ICD) shocks are a common and significant problem in pediatric patients and patients with congenital heart disease (CHD). OBJECTIVE The purpose of this study was to evaluate the effect of programming high detection rates and long detection duration on inappropriate shocks in this population. METHODS We performed a retrospective review of all patients with ICDs at a single pediatric center. Inappropriate shocks were defined as a shock for any rhythm except ventricular tachycardia or fibrillation. RESULTS A total of 144 patients were included, 63 (44%) with CHD. At implant, mean age and weight were 17 ⫾ 10 years and 57 ⫾ 23 kg. ICDs were single chamber in 35 (24%), dual chamber in 97 (67%), and biventricular in 12 (8%). The mean follow-up duration was 42 ⫾ 39 months. Appropriate shocks occurred in 29 (20.1%) and inappropriate shocks in 14 (9.7%). Causes of inappropriate shocks were supraventricular tachycardia (n ¼ 6), lead malfunction (n ¼ 4), sinus tachycardia (n ¼ 3), and T-wave oversensing (n ¼ 1). The mean ventricular fibrillation detection rate was 222 ⫾ 15 beats/ min, and the detection duration was 18 ⫾ 12 beats. Patients with
Introduction In 3 decades of use, implantable cardioverter-defibrillators (ICDs) have proven to be a safe and effective therapeutic option for pediatric patients and patients with congenital heart disease at risk of sudden death from ventricular arrhythmias.1 However, ICD shocks delivered for a reason other than a life-threatening ventricular arrhythmia, known as inappropriate shocks, occur frequently. Pediatric patients and patients with congenital heart disease have a particularly high rate of this complication, with the largest series reporting Z20% of patients receiving an inappropriate shock.1–3 This is likely a result of multiple factors, including higher heart rates in younger patients as well as a higher risk of lead malfunction related to more active lifestyles and longer duration of implant. Not only are inappropriate shocks painful, but they have also been associated with Address reprint requests and correspondence: Dr Jason Garnreiter, Saint Louis University School of Medicine, 1465 South Grand Blvd, St. Louis, MO 63104. E-mail address: [email protected].
1547-5271/$-see front matter B 2015 Heart Rhythm Society. All rights reserved.
shocks programmed in the ventricular tachycardia zone were more likely to receive an inappropriate shock (P ¼ .03). There were no associations between inappropriate shocks and age or weight at implant, presence of CHD, dual-chamber vs single-chamber device, history of supraventricular tachycardia, or antiarrhythmic use. There were no adverse events as a result of programming. CONCLUSION Programming high detection rates and long detection duration resulted in a low rate of inappropriate shocks without associated adverse events in this large cohort of pediatric and CHD patients with ICDs. KEYWORDS Inappropriate shocks; Implantable cardioverterdefibrillator; Pediatrics; Congenital heart disease ABBREVIATIONS DFT ¼ defibrillation threshold; ICD ¼ implantable cardioverter-defibrillator; SVT ¼ supraventricular tachycardia; VF ¼ ventricular fibrillation; VT ¼ ventricular tachycardia (Heart Rhythm 2015;12:937–942) I 2015 Heart Rhythm Society. All rights reserved.
psychosocial morbidity and increased mortality.4–7 In addition, despite significant technological advancements in ICDs and programming algorithms, the rate of inappropriate shocks has not decreased significantly over time in this population.1–3 Recent studies in adult patients have demonstrated that specific lenient programming practices aimed at increasing programmed detection heart rates and detection duration can significantly reduce the rate of inappropriate shocks while simultaneously decreasing mortality.8,9 However, there are little published data on ICD programming practices for pediatric patients and patients with congenital heart disease. In this study, we sought to report our experience with ICD programming practices and evaluate risk factors for inappropriate ICD shocks in this population.
Methods We performed a single-center retrospective review of all patients with ICDs seen at the University of Utah and http://dx.doi.org/10.1016/j.hrthm.2015.01.028
938 Table 1 Demographic data Total patients Male Congenital heart disease Mean weight at implant (kg) Mean age at implant (y) On antiarrhythmic medication β-Blocker Nadolol Metoprolol Carvedilol Other History of supraventricular tachycardia Implant indication Primary prevention Secondary prevention Device information Single chamber Dual chamber Biventricular Lead information Single coil Dual coil
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144 91 (63.2) 63 (43.8) 56.8 (range 4.1–125.8) 17.1 (range 0.2–64.2) 114 (79.2) 106 (73.6) 31 (29.2) 29 (27.4) 23 (21.7) 23 (21.7) 33 (23) 30 (20.8) 114 (79.2) 35 (24.3) 97 (67.4) 12 (8.3) 93 (64.6) 51 (35.4)
Values are presented as n (%) or as otherwise indicated.
Primary Children’s Medical Center from January 1, 2000 through December 31, 2012. This study received institutional review board approval. Data were obtained from a local clinical device database, in which patients are entered prospectively but outcome variables are not prespecified. Clinical patient characteristics were obtained from electronic medical records at implant and follow-up. Data obtained included demographic information, diagnoses, ICD implant indication, age and weight at implant, as well as device and lead information. Follow-up data were evaluated for the presence of both appropriate and inappropriate shocks, ICD programming information, history of supraventricular tachycardia (SVT), and use of antiarrhythmic medications. ICD programming details were recorded at the time of either inappropriate shock or the most recent follow-up visit if no inappropriate shocks occurred. Programming details obtained included ventricular fibrillation (VF) detection rate and duration as well as ventricular tachycardia (VT) detection rate and duration if shocks were programmed in the VT zone. The detection rate was recorded in beats per minute. The detection duration was recorded in either number of beats or number of seconds, depending on the manufacturer. For comparison purposes, those with detection duration in seconds were converted to duration in beats by using the programmed upper detection rate and detection duration. Inappropriate shocks were defined as those delivered for a rhythm other than VT or VF meeting programmed detection criteria. Statistical analysis was performed using SAS version 9.2 (SAS Institute Inc, Cary, NC). Continuous variables were expressed as means ⫾ SDs. Chi-square or Fisher exact tests were used for categorical variables, and independent t test or Wilcoxon rank sum tests were used for numerical variables.
Univariate and multivariate analyses were performed using exact logistic regression.
Results Patient’s demographic characteristics A total of 144 patients were evaluated. The demographic data are summarized in Table 1. Males comprised 63% and females 37% of the patients. Congenital heart disease was present in 63 patients (44%), with the most common diagnoses being tetralogy of Fallot in 27% and dtransposition of the great arteries in 25%. A breakdown of congenital heart disease diagnoses is shown in Figure 1. Primary electrical or acquired disorders were present in 81 patients (56%), most commonly cardiomyopathy in 48% (hypertrophic in 64% and dilated in 36%) and long QT syndrome in 27%. A breakdown of electrical or acquired diagnoses is shown in Figure 2. The mean follow-up duration was 42 ⫾ 39 months. A total of 33 patients (23%) had a history of SVT, either before ICD placement or during follow-up. At least 1 antiarrhythmic medication was being taken by 79% of patients, with 74% taking a β-blocker (29% nadolol, 22% carvedilol, 27% metoprolol, and 22% other). In general, patients were programmed with relatively high mean VF detection rates (226 ⫾ 15 beats/ min) and detection duration (18 ⫾ 12 beats), as shown in Figure 3.
ICD and implant characteristics At implant, the mean age was 17.1 ⫾ 9.8 years (range 0.2– 64.2 years) and the mean weight was 56.8 ⫾ 23.3 kg (range 4.1–125.8 kg). ICDs were implanted for secondary prevention in the majority of patients (79%). More than 90% of ICDs were transvenous, with only 13 epicardial devices (9%). The majority of patients (67%) received dual-chamber devices, with 24% receiving single-chamber devices. Biventricular devices were placed in 12 patients (8%). Those patients with a history of SVT were more likely to have a dual-chamber device implanted (P o .01). Single-coil leads
Figure 1 Breakdown of congenital structural heart disease diagnoses. AVSD ¼ atrioventricular septal defect; DORV ¼ double outlet left ventricle; dTGA ¼ d-transposition of the great arteries; IAA ¼ interrupted aortic arch; LVOT ¼ left ventricular outflow tract.
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Figure 2 Breakdown of electrical or acquired disorders. ARVC ¼ arrhythmogenic right ventricular cardiomyopathy; CPVT ¼ catecholaminergic polymorphic ventricular tachycardia; HCM ¼ hypertrophic cardiomyopathy; VF ¼ ventricular fibrillation; VT ¼ ventricular tachycardia.
were placed in 65% of patients and dual-coil leads in 35%. ICD manufacturers included Medtronic, Inc (Minneapolis, MN) in 50%, Boston Scientific/Guidant (Boston Scientific Corp, Natick, MA) in 26%, and St Jude Medical, Inc (Minneapolis, MN) in 24%. Defibrillation threshold (DFT) data were available in 114 patients (79%), with a mean DFT of 15.1 ⫾ 7 J. Implant complications occurred in only 3 patients (2%), 2 with pulseless electrical activity after DFT testing, and 1 with unexpected VF during implant requiring external defibrillation. There were no implant-related deaths. In the 63 patients with congenital heart disease, 10 (16%) had ICDs implanted for primary prevention. These patients had various diagnoses, including 3 each with d-transposition of the great arteries and atrioventricular septal defects, 2 with tetralogy of Fallot, and 1 each with Ebstein’s anomaly and coarctation of the aorta. Of these, 9 (90%) had systemic ventricular dysfunction as the indication for ICD placement. The mean systemic ventricular ejection fraction was 28% for these patients, although 2 patients with systemic right ventricles had only qualitative assessments of ventricular function, with 1 moderately and 1 severely reduced. The patient with coarctation of the aorta had documented nonsustained VT as the indication.
Figure 3
In total, 39 patients (27.1%) experienced a shock, with 25 (17.4%) receiving appropriate shocks only, 10 (6.9%) receiving inappropriate shocks only, and 4 (2.8%) receiving both appropriate and inappropriate shocks. Freedom from shocks for the whole cohort is demonstrated in Figure 4. Appropriate shocks were experienced by 29 patients (20.1%). Patients in the secondary prevention group were more likely to receive an appropriate shock than those in the primary prevention group (P ¼ .01; Table 2). There was no association with appropriate shocks and the presence of congenital heart disease (P ¼ .26), or single-chamber vs dual-chamber device (P ¼ .16). There was no significant difference in programming parameters between the primary prevention and secondary prevention groups (Table 2). Inappropriate shocks were experienced by 14 patients (9.7%). Of these, 7 (50%) were female, 5 (36%) had congenital heart disease, and 12 (86%) had ICD implantation for secondary prevention. At the time of implant, the mean age for these patients was 15 ⫾ 6.3 years and the mean weight was 52 ⫾ 19 kg. Dual-coil leads were present in 5 patients (36%) and an epicardial lead in 1 (7%). Ten patients (71%) were prescribed a β-blocker, 1 was prescribed diltiazem, and 3 were not on an antiarrhythmic medication. Causes of inappropriate shocks were SVT or sinus tachycardia in 9 (64%), Sprint Fidelis (Medtronic) lead fracture in 4 (29%), and T-wave oversensing in 1 (7%). Inappropriate shocks occurred at an average of 30 ⫾ 30 months after ICD implant. For those patients receiving an inappropriate shock, the VF detection rate was 226 ⫾ 22 beats/min and duration was 15 ⫾ 8 beats, and VT detection rate was 209 ⫾ 24 beats/ min and duration was 25 ⫾ 17 beats. Programming details at the time of inappropriate shock were unknown for 2 patients, as the inappropriate shock occurred at an outside institution. Inappropriate shocks were associated with the presence of a dual-chamber device (P ¼ .02) in univariate analysis, with all 14 patients receiving an inappropriate shock having a dual-chamber device (Table 3). Inappropriate shocks were also associated with a history of SVT (P ¼ .02) in univariate analysis. However, in multivariate analysis, neither the
VF detection rate programming for the whole cohort. VF ¼ ventricular fibrillation.
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Figure 4
Freedom from appropriate and inappropriate shocks over time for the whole cohort. ICD ¼ implantable cardioverter-defibrillator.
presence of a dual-chamber device nor a history of SVT was independently associated with inappropriate shocks (Table 4). Those patients who had a shock programmed in a VT zone were more likely to receive an inappropriate shock than those who did not (P ¼ .03). There was no association of inappropriate shocks with sex (P ¼ .28), presence of congenital heart disease (P ¼ .28), age at implant (P ¼ .39), weight at implant (P ¼ .45), or device manufacturer (P ¼ .37). There was no association between VF or VT detection rate or duration and inappropriate shocks. However, the majority of patients were programmed with relatively high detection rates and long detection duration as an institutional practice (Figure 3). This limited the ability to detect differences in outcomes related to programming parameters.
Adverse events A total of 8 patients (5.6%) died. One died in the intensive care unit with pulseless electrical activity after a successful ICD shock for VF. One patient with a history of Duchenne muscular dystrophy died secondary to a respiratory arrest at home. Postmortem device interrogation disclosed no high rate events and no shocks delivered. Three patients died secondary to a stroke, 2 from suicide, and 1 from cancer. The details of 1 death could not be obtained from the medical record. One patient experienced a syncopal episode secondary to undersensing of VF, which eventually broke spontaneously Table 2
and the patient had full recovery. A review of the electrogram revealed that undersensing was secondary to lowamplitude R waves during VF and was not secondary to detection rate or duration programming. There were no instances of syncope or death secondary to untreated VT or VF failing to meet programmed detection rate or duration.
Discussion Despite previous reports of higher rates of inappropriate ICD shocks, in this study we report a o10% rate of inappropriate ICD shocks in a large cohort of pediatric and congenital heart disease patients with ICDs. This is less than half the rate that has been reported in other large series in this patient population.1–3 This is an important finding, as the high rate of inappropriate shocks experienced by these patients has been a major problem that has not been significantly reduced in over 20 years of ICD use in this population. As a standard practice, this center programs ICDs with relatively high detection rates (typically 4220 beats/min) and relatively long detection duration (typically Z18 beats). There are little published data from other centers on ICD programming practices in pediatric patients and patients with congenital heart disease for comparison. This study was intended in part to investigate whether this practice was associated with a lower rate of inappropriate shocks. Although we found a low rate of inappropriate shocks, given that nearly all patients were programmed with relatively high detection rates and long detection durations, our ability to
Comparison of primary vs secondary prevention groups
Characteristic
Primary prevention (n ¼ 30)
Secondary prevention (n ¼ 114)
P
Congenital heart disease Appropriate shocks Inappropriate shocks Mean programmed VF detection rate (beats/min) Mean programmed VF detection duration (beats)
10 (30) 3 (10) 2 (7) 222 ⫾ 12 17 ⫾7
53 26 12 227 20
.20 .01 .74* .08 .20
Values are presented as mean ⫾ SD or as n (%). Results in bold indicate statistical significance. VF ¼ ventricular fibrillation. * Fisher exact test.
(47) (23) (11) ⫾ 15 ⫾ 13
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Univariate associations with inappropriate shocks With inappropriate shocks
P
Characteristic
Without inappropriate shocks
All patients (N ¼ 144) Sex Female Male CHD No Yes On antiarrhythmic medication No Yes Type of device Single chamber Dual chamber Device manufacturer Medtronic Boston Scientific St Jude Medical History of SVT Age at implant (y) Weight at implant (kg) VF detection rate (beats/min) VF detection duration (beats) Shocks programmed in the VT zone
130 (90.3)
14 (9.7)
46 (35.4) 84 (64.6)
7 (50) 7 (50)
.28
64 (49.2) 66 (50.8)
9 (64.3) 5 (35.7)
.28
27 (20.8) 103 (79.2)
3 (21.4) 11 (78.6)
.95
35 (26.9) 95 (73.1)
0 (0) 14 (100)
.02
66 (50.8) 31 (23.8) 33 (25.4) 26 (20) 17.4 ⫾ 10.1 57.3 ⫾ 23.7 226 ⫾ 14 18.7 ⫾ 8.4 80 (62)
6 (42.9) 6 (42.9) 2 (14.3) 7 (50) 15 ⫾ 6.6 52.1 ⫾ 19.9 226 ⫾ 23 16.9 ⫾ 7.3 11 (92)*
.37 .02 .40 .45 .97 .46 .03
Values are presented as mean ⫾ SD or as n (%). Results in bold indicate statistical significance. CHD ¼ congenital heart disease; SVT ¼ supraventricular tachycardia; VF ¼ ventricular fibrillation; VT ¼ ventricular tachycardia. * Excludes 2 patients receiving an inappropriate shock for whom these data are unknown.
statistically correlate this programming strategy with a reduction in inappropriate shocks was limited. However, patients with shocks programmed in the VT zone were more likely to receive an inappropriate shock, implying that programming shocks at lower heart rates may increase the likelihood of inappropriate shocks. Although we believe that programming high detection rates and long detection duration is in part responsible for our low rate of inappropriate shocks, additional data are needed to further investigate this finding. Other potential explanations include improved device technology in our cohort relative to historical controls or that our population represents a lower-risk population in general. However, the fact that our rate of appropriate shocks (20%) is similar to that reported previously (26%) would argue against this latter point.2 Similarly, although we found no association between the use of antiarrhythmic medications and inappropriate shocks, there was a high rate of antiarrhythmic use, in particular β-blockers ( 75% of patients). This frequent use of β-blockers may be in part responsible for the low rate of inappropriate shocks in this series. Other risk factors for inappropriate shocks identified with univariate analysis were the presence of a dual-chamber device and a history of SVT. However, patients with a history of SVT were more likely to have a dual-chamber device implanted, and in multivariate analysis neither of these factors were independently associated with inappropriate shocks. Nevertheless, the presence of a dual-chamber device did not confer any protection from inappropriate shocks. This is despite the fact that discrimination algorithms that use data from an atrial lead are often thought to be better
at reducing inappropriate shocks secondary to sinus tachycardia and SVT than are single-chamber algorithms. However, data from studies in adult patients are mixed in this regard, some showing reduced rates of inappropriate shocks in dual-chamber devices10–13 and others showing no improvement or worse outcomes as compared with singlechamber devices.14–16 A single large study that investigated this question in pediatric patients and patients with congenital heart disease found no reduction of inappropriate shocks in dual-chamber devices.3 Our data support this finding, further emphasizing that placement of an atrial lead should be reserved for patients with a specific pacing indication, rather than solely for the purpose of enhanced rhythm discrimination.
Conclusion In this study, we report a low rate of inappropriate shocks in a large cohort of pediatric patients and patients with congenital heart disease with ICDs. This low rate may be a result of programming strategies using high detection rates and long detection duration, as well as frequent use of β-blockers. Despite this strategy, there were no adverse events as a result of device programming. Additional data are needed to Table 4
Multivariate associations with inappropriate shocks
Characteristic
P
Dual-chamber device History of SVT
.13 .17
SVT ¼ supraventricular tachycardia.
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evaluate these associations. Dual-chamber devices did not confer any protection from inappropriate shocks relative to single-chamber devices, underscoring the need to reserve dual-chamber ICDs for those patients with a clear pacing indication.
References
9. 10.
11.
1. Silka MJ, Kron J, Dunnigan A, Dick M II; The Pediatric Electrophysiology Society. Sudden cardiac death and the use of implantable cardioverterdefibrillators in pediatric patients. Circulation 1993;87:800–807. 2. Berul CI, Van Hare GF, Kertesz NJ, Dubin AM, Cecchin F, Collins KK, Cannon BC, Alexander ME, Triedman JK, Walsh EP, Friedman RA. Results of a multicenter retrospective implantable cardioverter-defibrillator registry of pediatric and congenital heart disease patients. J Am Coll Cardiol 2008;51:1685–1691. 3. Lawrence D, Von Bergen N, Law IH, Bradley DJ, Dick M, Frias PA, Streiper MJ, Fischbach PS. Inappropriate ICD discharges in single-chamber versus dualchamber devices in the pediatric and young adult population. J Cardiovasc Electrophysiol 2009;20:287–290. 4. Daubert JP, Zareba W, Cannom DS, et al. Inappropriate implantable cardioverterdefibrillator shocks in MADIT II: frequency, mechanisms, predictors, and survival impact. J Am Coll Cardiol 2008;51:1357–1365. 5. van Rees JB, Borleffs CJ, de Bie MK, Stijnen T, van Erven L, Bax JJ, Schalij MJ. Inappropriate implantable cardioverter-defibrillator shocks: incidence, predictors, and impact on mortality. J Am Coll Cardiol 2011;57:556–562. 6. Poole JE, Johnson GW, Hellkamp AS, et al. Prognostic importance of defibrillator shocks in patients with heart failure. N Engl J Med 2008;359:1009–1017. 7. Marcus GM, Chan DW, Redberg RF. Recollection of pain due to inappropriate versus appropriate implantable cardioverter-defibrillator shocks. Pacing Clin Electrophysiol 2011;34:348–353. 8. Wilkoff BL, Williamson BD, Stern RS, Moore SL, Lu F, Lee SW, BirgersdotterGreen UM, Wathen MS, Van Gelder IC, Heubner BM, Brown ML, Holloman KK. Strategic programming of detection and therapy parameters in implantable cardioverter-defibrillators reduces shocks in primary prevention patients: results
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from the PREPARE (Primary Prevention Parameters Evaluation) study. J Am Coll Cardiol 2008;52:541–550. Moss AJ, Schuger C, Beck CA, et al. Reduction in inappropriate therapy and mortality through ICD programming. N Engl J Med 2012;367:2275–2283. Friedman PA, McClelland RL, Bamlet WR, et al. Dual-chamber versus singlechamber detection enhancements for implantable defibrillator rhythm diagnosis: the detect supraventricular tachycardia study. Circulation 2006;113: 2871–2879. Almendral J, Arribas F, Wolpert C, Ricci R, Adragao P, Cobo E, Navarro X, Quesada A. Dual-chamber defibrillators reduce clinically significant adverse events compared with single-chamber devices: results from the DATAS (Dual chamber and Atrial Tachyarrhythmias Adverse events Study) trial. Europace 2008;10:528–535. Diemberger I, Martignani C, Biffi M, Frabetti L, Valzania C, Cooke R, Rapezzi C, Branzi A, Boriani G. Arrhythmia discrimination by physician and defibrillator: importance of atrial channel. Int J Cardiol 2012;154: 134–140. Ricci RP, Quesada A, Almendral J, Arribas F, Wolpert C, Adragao P, ZoniBerisso M, Navarro X, DeSanto T, Grammatico A, Santini M. Dual-chamber implantable cardioverter defibrillators reduce clinical adverse events related to atrial fibrillation when compared with single-chamber defibrillators: a subanalysis of the DATAS trial. Europace 2009;11:587–593. Deisenhofer I, Kolb C, Ndrepepa G, Schreieck J, Karch M, Schmieder S, Zrenner B, Schmitt C. Do current dual chamber cardioverter defibrillators have advantages over conventional single chamber cardioverter defibrillators in reducing inappropriate therapies? A randomized, prospective study. J Cardiovasc Electrophysiol 2001;12:134–142. Berenbom LD, Weiford BC, Vacek JL, Emert MP, Hall WJ, Andrews ML, McNitt S, Zareba W, Moss AJ. Differences in outcomes between patients treated with single- versus dual-chamber implantable cardioverter defibrillators: a substudy of the Multicenter Automatic Defibrillator Implantation Trial II. Ann Noninvasive Electrocardiol 2005;10:429–435. Theuns DA, Klootwijk AP, Goedhart DM, Jordaens LJ. Prevention of inappropriate therapy in implantable cardioverter-defibrillators: results of a prospective, randomized study of tachyarrhythmia detection algorithms. J Am Coll Cardiol 2004;44:2362–2367.
CLINICAL PERSPECTIVES Inappropriate implantable cardioverter-defibrillator (ICD) shocks are common in pediatric patients and patients with congenital heart disease with ICDs and can contribute to increased morbidity and mortality. Although studies in adult patients have demonstrated that ICD programming practices aimed at increasing the detection rate and duration of ventricular arrhythmias can reduce the frequency of inappropriate ICD shocks, there are little published data on ICD programming practices in pediatric patients and patients with congenital heart disease. In this study, we present a lower rate of inappropriate shocks in our cohort than that in other studies, as well as data on ICD programming practices that may be in part responsible for this lower rate of inappropriate shocks. This information can help physicians make informed decisions about programming parameters for these patients and potentially reduce the rate of inappropriate ICD shocks. Additional studies will be needed to verify the safety and efficacy of these programming strategies in this cohort, which could then help to generate guidelines for ICD programming in pediatric patients and patients with congenital heart disease.
Introduction In 3 decades of use, implantable cardioverter-defibrillators (ICDs) have proven to be a safe and effective therapeutic option for pediatric patients and patients with congenital heart disease at risk of sudden death from ventricular arrhythmias.1 However, ICD shocks delivered for a reason other than a life-threatening ventricular arrhythmia, known as inappropriate shocks, occur frequently. Pediatric patients and patients with congenital heart disease have a particularly high rate of this complication, with the largest series reporting Z20% of patients receiving an inappropriate shock.1–3 This is likely a result of multiple factors, including higher heart rates in younger patients as well as a higher risk of lead malfunction related to more active lifestyles and longer duration of implant. Not only are inappropriate shocks painful, but they have also been associated with Address reprint requests and correspondence: Dr Jason Garnreiter, Saint Louis University School of Medicine, 1465 South Grand Blvd, St. Louis, MO 63104. E-mail address: [email protected].
1547-5271/$-see front matter B 2015 Heart Rhythm Society. All rights reserved.
shocks programmed in the ventricular tachycardia zone were more likely to receive an inappropriate shock (P ¼ .03). There were no associations between inappropriate shocks and age or weight at implant, presence of CHD, dual-chamber vs single-chamber device, history of supraventricular tachycardia, or antiarrhythmic use. There were no adverse events as a result of programming. CONCLUSION Programming high detection rates and long detection duration resulted in a low rate of inappropriate shocks without associated adverse events in this large cohort of pediatric and CHD patients with ICDs. KEYWORDS Inappropriate shocks; Implantable cardioverterdefibrillator; Pediatrics; Congenital heart disease ABBREVIATIONS DFT ¼ defibrillation threshold; ICD ¼ implantable cardioverter-defibrillator; SVT ¼ supraventricular tachycardia; VF ¼ ventricular fibrillation; VT ¼ ventricular tachycardia (Heart Rhythm 2015;12:937–942) I 2015 Heart Rhythm Society. All rights reserved.
psychosocial morbidity and increased mortality.4–7 In addition, despite significant technological advancements in ICDs and programming algorithms, the rate of inappropriate shocks has not decreased significantly over time in this population.1–3 Recent studies in adult patients have demonstrated that specific lenient programming practices aimed at increasing programmed detection heart rates and detection duration can significantly reduce the rate of inappropriate shocks while simultaneously decreasing mortality.8,9 However, there are little published data on ICD programming practices for pediatric patients and patients with congenital heart disease. In this study, we sought to report our experience with ICD programming practices and evaluate risk factors for inappropriate ICD shocks in this population.
Methods We performed a single-center retrospective review of all patients with ICDs seen at the University of Utah and http://dx.doi.org/10.1016/j.hrthm.2015.01.028
938 Table 1 Demographic data Total patients Male Congenital heart disease Mean weight at implant (kg) Mean age at implant (y) On antiarrhythmic medication β-Blocker Nadolol Metoprolol Carvedilol Other History of supraventricular tachycardia Implant indication Primary prevention Secondary prevention Device information Single chamber Dual chamber Biventricular Lead information Single coil Dual coil
Heart Rhythm, Vol 12, No 5, May 2015
144 91 (63.2) 63 (43.8) 56.8 (range 4.1–125.8) 17.1 (range 0.2–64.2) 114 (79.2) 106 (73.6) 31 (29.2) 29 (27.4) 23 (21.7) 23 (21.7) 33 (23) 30 (20.8) 114 (79.2) 35 (24.3) 97 (67.4) 12 (8.3) 93 (64.6) 51 (35.4)
Values are presented as n (%) or as otherwise indicated.
Primary Children’s Medical Center from January 1, 2000 through December 31, 2012. This study received institutional review board approval. Data were obtained from a local clinical device database, in which patients are entered prospectively but outcome variables are not prespecified. Clinical patient characteristics were obtained from electronic medical records at implant and follow-up. Data obtained included demographic information, diagnoses, ICD implant indication, age and weight at implant, as well as device and lead information. Follow-up data were evaluated for the presence of both appropriate and inappropriate shocks, ICD programming information, history of supraventricular tachycardia (SVT), and use of antiarrhythmic medications. ICD programming details were recorded at the time of either inappropriate shock or the most recent follow-up visit if no inappropriate shocks occurred. Programming details obtained included ventricular fibrillation (VF) detection rate and duration as well as ventricular tachycardia (VT) detection rate and duration if shocks were programmed in the VT zone. The detection rate was recorded in beats per minute. The detection duration was recorded in either number of beats or number of seconds, depending on the manufacturer. For comparison purposes, those with detection duration in seconds were converted to duration in beats by using the programmed upper detection rate and detection duration. Inappropriate shocks were defined as those delivered for a rhythm other than VT or VF meeting programmed detection criteria. Statistical analysis was performed using SAS version 9.2 (SAS Institute Inc, Cary, NC). Continuous variables were expressed as means ⫾ SDs. Chi-square or Fisher exact tests were used for categorical variables, and independent t test or Wilcoxon rank sum tests were used for numerical variables.
Univariate and multivariate analyses were performed using exact logistic regression.
Results Patient’s demographic characteristics A total of 144 patients were evaluated. The demographic data are summarized in Table 1. Males comprised 63% and females 37% of the patients. Congenital heart disease was present in 63 patients (44%), with the most common diagnoses being tetralogy of Fallot in 27% and dtransposition of the great arteries in 25%. A breakdown of congenital heart disease diagnoses is shown in Figure 1. Primary electrical or acquired disorders were present in 81 patients (56%), most commonly cardiomyopathy in 48% (hypertrophic in 64% and dilated in 36%) and long QT syndrome in 27%. A breakdown of electrical or acquired diagnoses is shown in Figure 2. The mean follow-up duration was 42 ⫾ 39 months. A total of 33 patients (23%) had a history of SVT, either before ICD placement or during follow-up. At least 1 antiarrhythmic medication was being taken by 79% of patients, with 74% taking a β-blocker (29% nadolol, 22% carvedilol, 27% metoprolol, and 22% other). In general, patients were programmed with relatively high mean VF detection rates (226 ⫾ 15 beats/ min) and detection duration (18 ⫾ 12 beats), as shown in Figure 3.
ICD and implant characteristics At implant, the mean age was 17.1 ⫾ 9.8 years (range 0.2– 64.2 years) and the mean weight was 56.8 ⫾ 23.3 kg (range 4.1–125.8 kg). ICDs were implanted for secondary prevention in the majority of patients (79%). More than 90% of ICDs were transvenous, with only 13 epicardial devices (9%). The majority of patients (67%) received dual-chamber devices, with 24% receiving single-chamber devices. Biventricular devices were placed in 12 patients (8%). Those patients with a history of SVT were more likely to have a dual-chamber device implanted (P o .01). Single-coil leads
Figure 1 Breakdown of congenital structural heart disease diagnoses. AVSD ¼ atrioventricular septal defect; DORV ¼ double outlet left ventricle; dTGA ¼ d-transposition of the great arteries; IAA ¼ interrupted aortic arch; LVOT ¼ left ventricular outflow tract.
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ICD shocks
Figure 2 Breakdown of electrical or acquired disorders. ARVC ¼ arrhythmogenic right ventricular cardiomyopathy; CPVT ¼ catecholaminergic polymorphic ventricular tachycardia; HCM ¼ hypertrophic cardiomyopathy; VF ¼ ventricular fibrillation; VT ¼ ventricular tachycardia.
were placed in 65% of patients and dual-coil leads in 35%. ICD manufacturers included Medtronic, Inc (Minneapolis, MN) in 50%, Boston Scientific/Guidant (Boston Scientific Corp, Natick, MA) in 26%, and St Jude Medical, Inc (Minneapolis, MN) in 24%. Defibrillation threshold (DFT) data were available in 114 patients (79%), with a mean DFT of 15.1 ⫾ 7 J. Implant complications occurred in only 3 patients (2%), 2 with pulseless electrical activity after DFT testing, and 1 with unexpected VF during implant requiring external defibrillation. There were no implant-related deaths. In the 63 patients with congenital heart disease, 10 (16%) had ICDs implanted for primary prevention. These patients had various diagnoses, including 3 each with d-transposition of the great arteries and atrioventricular septal defects, 2 with tetralogy of Fallot, and 1 each with Ebstein’s anomaly and coarctation of the aorta. Of these, 9 (90%) had systemic ventricular dysfunction as the indication for ICD placement. The mean systemic ventricular ejection fraction was 28% for these patients, although 2 patients with systemic right ventricles had only qualitative assessments of ventricular function, with 1 moderately and 1 severely reduced. The patient with coarctation of the aorta had documented nonsustained VT as the indication.
Figure 3
In total, 39 patients (27.1%) experienced a shock, with 25 (17.4%) receiving appropriate shocks only, 10 (6.9%) receiving inappropriate shocks only, and 4 (2.8%) receiving both appropriate and inappropriate shocks. Freedom from shocks for the whole cohort is demonstrated in Figure 4. Appropriate shocks were experienced by 29 patients (20.1%). Patients in the secondary prevention group were more likely to receive an appropriate shock than those in the primary prevention group (P ¼ .01; Table 2). There was no association with appropriate shocks and the presence of congenital heart disease (P ¼ .26), or single-chamber vs dual-chamber device (P ¼ .16). There was no significant difference in programming parameters between the primary prevention and secondary prevention groups (Table 2). Inappropriate shocks were experienced by 14 patients (9.7%). Of these, 7 (50%) were female, 5 (36%) had congenital heart disease, and 12 (86%) had ICD implantation for secondary prevention. At the time of implant, the mean age for these patients was 15 ⫾ 6.3 years and the mean weight was 52 ⫾ 19 kg. Dual-coil leads were present in 5 patients (36%) and an epicardial lead in 1 (7%). Ten patients (71%) were prescribed a β-blocker, 1 was prescribed diltiazem, and 3 were not on an antiarrhythmic medication. Causes of inappropriate shocks were SVT or sinus tachycardia in 9 (64%), Sprint Fidelis (Medtronic) lead fracture in 4 (29%), and T-wave oversensing in 1 (7%). Inappropriate shocks occurred at an average of 30 ⫾ 30 months after ICD implant. For those patients receiving an inappropriate shock, the VF detection rate was 226 ⫾ 22 beats/min and duration was 15 ⫾ 8 beats, and VT detection rate was 209 ⫾ 24 beats/ min and duration was 25 ⫾ 17 beats. Programming details at the time of inappropriate shock were unknown for 2 patients, as the inappropriate shock occurred at an outside institution. Inappropriate shocks were associated with the presence of a dual-chamber device (P ¼ .02) in univariate analysis, with all 14 patients receiving an inappropriate shock having a dual-chamber device (Table 3). Inappropriate shocks were also associated with a history of SVT (P ¼ .02) in univariate analysis. However, in multivariate analysis, neither the
VF detection rate programming for the whole cohort. VF ¼ ventricular fibrillation.
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Figure 4
Freedom from appropriate and inappropriate shocks over time for the whole cohort. ICD ¼ implantable cardioverter-defibrillator.
presence of a dual-chamber device nor a history of SVT was independently associated with inappropriate shocks (Table 4). Those patients who had a shock programmed in a VT zone were more likely to receive an inappropriate shock than those who did not (P ¼ .03). There was no association of inappropriate shocks with sex (P ¼ .28), presence of congenital heart disease (P ¼ .28), age at implant (P ¼ .39), weight at implant (P ¼ .45), or device manufacturer (P ¼ .37). There was no association between VF or VT detection rate or duration and inappropriate shocks. However, the majority of patients were programmed with relatively high detection rates and long detection duration as an institutional practice (Figure 3). This limited the ability to detect differences in outcomes related to programming parameters.
Adverse events A total of 8 patients (5.6%) died. One died in the intensive care unit with pulseless electrical activity after a successful ICD shock for VF. One patient with a history of Duchenne muscular dystrophy died secondary to a respiratory arrest at home. Postmortem device interrogation disclosed no high rate events and no shocks delivered. Three patients died secondary to a stroke, 2 from suicide, and 1 from cancer. The details of 1 death could not be obtained from the medical record. One patient experienced a syncopal episode secondary to undersensing of VF, which eventually broke spontaneously Table 2
and the patient had full recovery. A review of the electrogram revealed that undersensing was secondary to lowamplitude R waves during VF and was not secondary to detection rate or duration programming. There were no instances of syncope or death secondary to untreated VT or VF failing to meet programmed detection rate or duration.
Discussion Despite previous reports of higher rates of inappropriate ICD shocks, in this study we report a o10% rate of inappropriate ICD shocks in a large cohort of pediatric and congenital heart disease patients with ICDs. This is less than half the rate that has been reported in other large series in this patient population.1–3 This is an important finding, as the high rate of inappropriate shocks experienced by these patients has been a major problem that has not been significantly reduced in over 20 years of ICD use in this population. As a standard practice, this center programs ICDs with relatively high detection rates (typically 4220 beats/min) and relatively long detection duration (typically Z18 beats). There are little published data from other centers on ICD programming practices in pediatric patients and patients with congenital heart disease for comparison. This study was intended in part to investigate whether this practice was associated with a lower rate of inappropriate shocks. Although we found a low rate of inappropriate shocks, given that nearly all patients were programmed with relatively high detection rates and long detection durations, our ability to
Comparison of primary vs secondary prevention groups
Characteristic
Primary prevention (n ¼ 30)
Secondary prevention (n ¼ 114)
P
Congenital heart disease Appropriate shocks Inappropriate shocks Mean programmed VF detection rate (beats/min) Mean programmed VF detection duration (beats)
10 (30) 3 (10) 2 (7) 222 ⫾ 12 17 ⫾7
53 26 12 227 20
.20 .01 .74* .08 .20
Values are presented as mean ⫾ SD or as n (%). Results in bold indicate statistical significance. VF ¼ ventricular fibrillation. * Fisher exact test.
(47) (23) (11) ⫾ 15 ⫾ 13
Garnreiter et al Table 3
Inappropriate ICD Shocks in Pediatrics
941
Univariate associations with inappropriate shocks With inappropriate shocks
P
Characteristic
Without inappropriate shocks
All patients (N ¼ 144) Sex Female Male CHD No Yes On antiarrhythmic medication No Yes Type of device Single chamber Dual chamber Device manufacturer Medtronic Boston Scientific St Jude Medical History of SVT Age at implant (y) Weight at implant (kg) VF detection rate (beats/min) VF detection duration (beats) Shocks programmed in the VT zone
130 (90.3)
14 (9.7)
46 (35.4) 84 (64.6)
7 (50) 7 (50)
.28
64 (49.2) 66 (50.8)
9 (64.3) 5 (35.7)
.28
27 (20.8) 103 (79.2)
3 (21.4) 11 (78.6)
.95
35 (26.9) 95 (73.1)
0 (0) 14 (100)
.02
66 (50.8) 31 (23.8) 33 (25.4) 26 (20) 17.4 ⫾ 10.1 57.3 ⫾ 23.7 226 ⫾ 14 18.7 ⫾ 8.4 80 (62)
6 (42.9) 6 (42.9) 2 (14.3) 7 (50) 15 ⫾ 6.6 52.1 ⫾ 19.9 226 ⫾ 23 16.9 ⫾ 7.3 11 (92)*
.37 .02 .40 .45 .97 .46 .03
Values are presented as mean ⫾ SD or as n (%). Results in bold indicate statistical significance. CHD ¼ congenital heart disease; SVT ¼ supraventricular tachycardia; VF ¼ ventricular fibrillation; VT ¼ ventricular tachycardia. * Excludes 2 patients receiving an inappropriate shock for whom these data are unknown.
statistically correlate this programming strategy with a reduction in inappropriate shocks was limited. However, patients with shocks programmed in the VT zone were more likely to receive an inappropriate shock, implying that programming shocks at lower heart rates may increase the likelihood of inappropriate shocks. Although we believe that programming high detection rates and long detection duration is in part responsible for our low rate of inappropriate shocks, additional data are needed to further investigate this finding. Other potential explanations include improved device technology in our cohort relative to historical controls or that our population represents a lower-risk population in general. However, the fact that our rate of appropriate shocks (20%) is similar to that reported previously (26%) would argue against this latter point.2 Similarly, although we found no association between the use of antiarrhythmic medications and inappropriate shocks, there was a high rate of antiarrhythmic use, in particular β-blockers ( 75% of patients). This frequent use of β-blockers may be in part responsible for the low rate of inappropriate shocks in this series. Other risk factors for inappropriate shocks identified with univariate analysis were the presence of a dual-chamber device and a history of SVT. However, patients with a history of SVT were more likely to have a dual-chamber device implanted, and in multivariate analysis neither of these factors were independently associated with inappropriate shocks. Nevertheless, the presence of a dual-chamber device did not confer any protection from inappropriate shocks. This is despite the fact that discrimination algorithms that use data from an atrial lead are often thought to be better
at reducing inappropriate shocks secondary to sinus tachycardia and SVT than are single-chamber algorithms. However, data from studies in adult patients are mixed in this regard, some showing reduced rates of inappropriate shocks in dual-chamber devices10–13 and others showing no improvement or worse outcomes as compared with singlechamber devices.14–16 A single large study that investigated this question in pediatric patients and patients with congenital heart disease found no reduction of inappropriate shocks in dual-chamber devices.3 Our data support this finding, further emphasizing that placement of an atrial lead should be reserved for patients with a specific pacing indication, rather than solely for the purpose of enhanced rhythm discrimination.
Conclusion In this study, we report a low rate of inappropriate shocks in a large cohort of pediatric patients and patients with congenital heart disease with ICDs. This low rate may be a result of programming strategies using high detection rates and long detection duration, as well as frequent use of β-blockers. Despite this strategy, there were no adverse events as a result of device programming. Additional data are needed to Table 4
Multivariate associations with inappropriate shocks
Characteristic
P
Dual-chamber device History of SVT
.13 .17
SVT ¼ supraventricular tachycardia.
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evaluate these associations. Dual-chamber devices did not confer any protection from inappropriate shocks relative to single-chamber devices, underscoring the need to reserve dual-chamber ICDs for those patients with a clear pacing indication.
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from the PREPARE (Primary Prevention Parameters Evaluation) study. J Am Coll Cardiol 2008;52:541–550. Moss AJ, Schuger C, Beck CA, et al. Reduction in inappropriate therapy and mortality through ICD programming. N Engl J Med 2012;367:2275–2283. Friedman PA, McClelland RL, Bamlet WR, et al. Dual-chamber versus singlechamber detection enhancements for implantable defibrillator rhythm diagnosis: the detect supraventricular tachycardia study. Circulation 2006;113: 2871–2879. Almendral J, Arribas F, Wolpert C, Ricci R, Adragao P, Cobo E, Navarro X, Quesada A. Dual-chamber defibrillators reduce clinically significant adverse events compared with single-chamber devices: results from the DATAS (Dual chamber and Atrial Tachyarrhythmias Adverse events Study) trial. Europace 2008;10:528–535. Diemberger I, Martignani C, Biffi M, Frabetti L, Valzania C, Cooke R, Rapezzi C, Branzi A, Boriani G. Arrhythmia discrimination by physician and defibrillator: importance of atrial channel. Int J Cardiol 2012;154: 134–140. Ricci RP, Quesada A, Almendral J, Arribas F, Wolpert C, Adragao P, ZoniBerisso M, Navarro X, DeSanto T, Grammatico A, Santini M. Dual-chamber implantable cardioverter defibrillators reduce clinical adverse events related to atrial fibrillation when compared with single-chamber defibrillators: a subanalysis of the DATAS trial. Europace 2009;11:587–593. Deisenhofer I, Kolb C, Ndrepepa G, Schreieck J, Karch M, Schmieder S, Zrenner B, Schmitt C. Do current dual chamber cardioverter defibrillators have advantages over conventional single chamber cardioverter defibrillators in reducing inappropriate therapies? A randomized, prospective study. J Cardiovasc Electrophysiol 2001;12:134–142. Berenbom LD, Weiford BC, Vacek JL, Emert MP, Hall WJ, Andrews ML, McNitt S, Zareba W, Moss AJ. Differences in outcomes between patients treated with single- versus dual-chamber implantable cardioverter defibrillators: a substudy of the Multicenter Automatic Defibrillator Implantation Trial II. Ann Noninvasive Electrocardiol 2005;10:429–435. Theuns DA, Klootwijk AP, Goedhart DM, Jordaens LJ. Prevention of inappropriate therapy in implantable cardioverter-defibrillators: results of a prospective, randomized study of tachyarrhythmia detection algorithms. J Am Coll Cardiol 2004;44:2362–2367.
CLINICAL PERSPECTIVES Inappropriate implantable cardioverter-defibrillator (ICD) shocks are common in pediatric patients and patients with congenital heart disease with ICDs and can contribute to increased morbidity and mortality. Although studies in adult patients have demonstrated that ICD programming practices aimed at increasing the detection rate and duration of ventricular arrhythmias can reduce the frequency of inappropriate ICD shocks, there are little published data on ICD programming practices in pediatric patients and patients with congenital heart disease. In this study, we present a lower rate of inappropriate shocks in our cohort than that in other studies, as well as data on ICD programming practices that may be in part responsible for this lower rate of inappropriate shocks. This information can help physicians make informed decisions about programming parameters for these patients and potentially reduce the rate of inappropriate ICD shocks. Additional studies will be needed to verify the safety and efficacy of these programming strategies in this cohort, which could then help to generate guidelines for ICD programming in pediatric patients and patients with congenital heart disease.
