Can we predict, prevent, and minimize defibrillator shocks? Lessons learned from “remote monitoring”

Abstract

Beyond their principal role of successfully detecting and treating ventricular tachycardia (VT) and ventricular fibrillation (VF) with overdrive antitachycardia pacing and defibrillation shocks, modern implantable cardioverter-defibrillators (ICDs) are capable of providing sophisticated pacing and resynchronization therapy. They store enormous amounts of technical and patient-related data, such as arrhythmia burden and heart failure status. Device manufacturers recently introduced “remote monitoring” technology, which allows home transmitters to interrogate devices and to download and transmit collected and stored data via the Internet to a protected network. Remote monitoring not only has rapidly shifted the paradigm in device follow-up but has heightened interest in exploring the wealth of available information to better understand device functionality and disease substrates.Irrespective of the indications for ICD placement, given the associated risk factors and comorbidities, the majority of recipients also would be prone, if they have not already experienced, to develop atrial fibrillation (AF). The presence of AF, with its 5% to 30% incidence in the ICD population, is not merely a “nuisance” because it has many detrimental effects.1Botto G.L. Luzi M. Ruffa F. Russo G. Ferrari G. Atrial tachyarrhythmias in primary and secondary prevention ICD recipients: clinical and prognostic data.Pacing Clin Electrophysiol. 2006; : S48-S53Crossref PubMed Scopus (6) Google Scholar, 2Borleffs C.J. van Rees J.B. van Welsenes G.H. et al.Prognostic importance of atrial fibrillation in implantable cardioverter-defibrillator patients.J Am Coll Cardiol. 2010; 55: 879-885Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar Paroxysmal, persistent, and permanent AF have hazard ratios (HRs) (95% confidence interval] of 1.3 (0.7–2.5), 1.2 (0.6–2.2), and 1.7 (1.0–2.7), respectively, for mortality and 1.2 (0.6–2.2), 1.1 (0.5–2.4), and 2.4 (1.5–4.0), respectively, for appropriate ICD shocks.2Borleffs C.J. van Rees J.B. van Welsenes G.H. et al.Prognostic importance of atrial fibrillation in implantable cardioverter-defibrillator patients.J Am Coll Cardiol. 2010; 55: 879-885Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar A newly detected AF within the first 3 months of ICD placement carries a significant risk for death with HR of 2.86 (1.02–8.05).3Bunch T.J. Day J.D. Olshansky B. et al.Newly detected atrial fibrillation in patients with an implantable cardioverter-defibrillator is a strong risk marker of increased mortality.Heart Rhythm. 2009; 6: 2-8Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar In patients with left ventricular dysfunction, persistent AF has been shown to cause appropriate ICD shocks and deterioration of heart failure.4Rienstra M. Smit M.D. Nieuwland W. et al.Persistent atrial fibrillation is associated with appropriate shocks and heart failure in patients with left ventricular dysfunction treated with an implantable cardioverter defibrillator.Am Heart J. 2007; 153: 120-126Abstract Full Text Full Text PDF PubMed Scopus (38) Google Scholar Furthermore, AF may be proarrhythmic. In the Jewel AF trial, 8.6% of all VT/VF episodes were found to have AF as a preceding or concomitant rhythm.5Stein K.M. Euler D.E. Mehra R. et al.Do atrial tachyarrhythmias beget ventricular tachyarrhythmias in defibrillator recipients?.J Am Coll Cardiol. 2002; 40: 335-340Abstract Full Text Full Text PDF PubMed Scopus (104) Google Scholar Interestingly, for consecutive episodes of VT/VF, time to next episode of VT/VF was longer when AF terminated than when it persisted.5Stein K.M. Euler D.E. Mehra R. et al.Do atrial tachyarrhythmias beget ventricular tachyarrhythmias in defibrillator recipients?.J Am Coll Cardiol. 2002; 40: 335-340Abstract Full Text Full Text PDF PubMed Scopus (104) Google ScholarFrom the device programming standpoint, “inappropriate shocks” due to AF are a complex issue. Data from small ICD registries as well as large prospective trials indicate that AF is the leading cause of inappropriate ICD shocks, with HRs of 2.0 to 2.9.6Nanthakumar K. Dorian P. Paquette M. et al.Is inappropriate implantable defibrillator shock therapy predictable?.J Interv Card Electrophysiol. 2003; 8: 215-220Crossref PubMed Scopus (45) Google Scholar, 7van Rees J.B. Borleffs C.J. de Bie M.K. et al.Inappropriate implantable cardioverter-defibrillator shocks: incidence, predictors, and impact on mortality.J Am Coll Cardiol. 2011; 57: 556-562Abstract Full Text Full Text PDF PubMed Scopus (326) Google Scholar, 8Daubert J.P. Zareba W. Cannom D.S. et al.Inappropriate implantable cardioverter-defibrillator shocks in MADIT II: frequency, mechanisms, predictors, and survival impact.J Am Coll Cardiol. 2008; 51: 1357-1365Abstract Full Text Full Text PDF PubMed Scopus (659) Google Scholar The time to first “inappropriate shocks” due to AF also depends on the severity of heart failure. In patients with New York Heart Association (NYHA) class III or IV heart failure, the 1- and 2-year “inappropriate” shock-free survival is reported to be 79% and 70% compared to 92% and 88% for patients in NYHA class I or II heart failure, respectively.9Hreybe H. Ezzeddine R. Barrington W. et al.Relation of advanced heart failure symptoms to risk of inappropriate defibrillator shocks.Am J Cardiol. 2006; 97: 544-546Abstract Full Text Full Text PDF PubMed Scopus (21) Google ScholarTo prevent “inappropriate shocks” resulting from supraventricular tachyarrhythmias, several rhythm discrimination algorithms have been developed. These algorithms are device-manufacturer specific and in many cases are device-model specific. The shortcomings of rhythm discrimination algorithms may occur in two ways: (1) when attempting to determine the true nature of the arrhythmia and valuable time elapses while treating the arrhythmia appropriately; and (2) when the ventricular rate is too rapid and erring on the side of caution results in the ICD delivering shocks anyway. Strategic programming of ICDs prevents “inappropriate shocks” and reduces “appropriate-but-unnecessary shocks.” In the PREPARE (Primary Prevention Parameters Evaluation) study, when the key programming strategies of (1) detecting only fast tachycardias (VT/VF rates ≥182 bpm, (2) detecting only sustained tachycardias (VT/VF maintained for at least 30–40 beats, (3) applying antitachycardia pacing as first therapy for fast VTs with rates of 182–250 bpm, (4) using supraventricular tachyarrhythmia discriminators for rhythms ≥200 bpm; and (5) using high-output first shock, the morbidity index (combined incidence of device-delivered shocks, arrhythmic syncope, and untreated sustained symptomatic VT/VF) was found to be significantly lower at 0.26 events per patient-year vs 0.69 events per patient-year in the control setting.10Wilkoff B.L. Williamson B.D. Stern R.S. et al.Strategic programming of detection and therapy parameters in implantable cardioverter-defibrillators reduces shocks in primary prevention patients: results from the PREPARE (Primary Prevention Parameters Evaluation) study.J Am Coll Cardiol. 2008; 52: 541-550Abstract Full Text Full Text PDF PubMed Scopus (454) Google ScholarWith regard to “remote monitoring,” several studies, notably the ALTITUDE survival study, the CONNECT (Clinical Evaluation of Remote Notification to Reduce Time to Clinical Decision) study, and the TRUST (the Lumos-T Safely Reduces Routine Office Device Follow-Up) trial, using LATITUDE (Boston Scientific Corporation, Natick, MA, USA), CareLink Network (Medtronic, Inc, Minneapolis, MN, USA), and Home Monitoring (Biotronik, Berlin, Germany), respectively, showed that remote monitoring technology is safe, allows more rapid detection of actionable events, reduces time to clinical intervention, and improves patients survival.11Saxon L.A. Hayes D.L. Gilliam F.R. et al.Long-term outcome after ICD and CRT implantation and influence of remote device follow-up: the ALTITUDE survival study.Circulation. 2010; 122: 2359-2367Crossref PubMed Scopus (408) Google Scholar, 12Crossley G.H. Boyle A. Vitense H. et al.The CONNECT (Clinical Evaluation of Remote Notification to Reduce Time to Clinical Decision) trial: the value of wireless remote monitoring with automatic clinician alerts.J Am Coll Cardiol. 2011; 57: 1181-1189Abstract Full Text Full Text PDF PubMed Scopus (394) Google Scholar, 13Varma N. Epstein A.E. Irimpen A. et al.Efficacy and safety of automatic remote monitoring for implantable cardioverter-defibrillator follow-up: the Lumos-T Safely Reduces Routine Office Device Follow-up (TRUST) trial.Circulation. 2010; 122: 325-332Crossref PubMed Scopus (442) Google Scholar However, adequate long-term follow-up data on remote monitoring are not available. In addition, the report of early withdrawal from remote monitoring of up to 7.1% of patients due to transmission failure despite use of the GSM network rather than analog phone-line technology in the TRUST trial is alarming.13Varma N. Epstein A.E. Irimpen A. et al.Efficacy and safety of automatic remote monitoring for implantable cardioverter-defibrillator follow-up: the Lumos-T Safely Reduces Routine Office Device Follow-up (TRUST) trial.Circulation. 2010; 122: 325-332Crossref PubMed Scopus (442) Google Scholar Remote monitoring has not yet become the standard of care. In busy physicians' practices, the process of retrieving data from manufacturers' repositories and checking daily reports, which require significant support from trained personnel, may be overwhelming. Plus, it is not possible to physically examine, evaluate, and perform intervention, including remote programming of ICDs.In a study by Fischer et al14Fischer A. Ousdigian K.T. Johnson J.W. Gillberg J.M. Wilkoff B.L. The impact of atrial fibrillation with rapid ventricular rates and device programming on shocks in 106,513 ICD and CRT-D patients.Heart Rhythm. 2012; 9: 24-31Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar reported in this issue of HeartRhythm, the authors evaluated a very large patient population by retrospective observational analysis for the impact of AF and device programming on ICD shocks using a remote monitoring system. The main findings of the study were as follows: (1) 21% of patients received ICD shocks over a follow-up period of 2.5 ± 1.4 years, and (2) patients with AF with rapid ventricular rate whose devices were programmed with slower VT/VF detection thresholds and shorter VF detection intervals were associated with more shocks. To clinicians who treat patients with ICDs, heart failure, and AF, such results are not surprising. The authors' attempts to define AF with or without a rapid ventricular response and no/little AF based on the duration of AF and average ventricular rate and further defining it into paroxysmal, persistent, or permanent AF have scientific merit. However, one of the major limitations of the study is the lack of clinical data and the fact that no attempts were made toward adjudication of ICD shocks. How many patients received “appropriate” vs “inappropriate” shocks is unknown. In addition, whether patients who received shocks were sicker with worse heart failure and comorbidities and were less well treated than patients without shocks is unknown. Without the clinical variables, the association of ICD programming with shocks is questionable. Likewise, due to the lack of clinical data, one should be cautious in drawing conclusions about continuous monitoring of AF with rapid ventricular rate being a predictor of future ICD shocks. The topics of antiarrhythmic drugs, statins, and other upstream pharmacologic therapies and ablation therapies in the patient population with ICDs, heart failure, and arrhythmias are constantly debated. The opportunity to learn more about the role and impact of antiarrhythmic drugs, ablative procedures such as pulmonary vein isolation and left and right atrial ablation for atrial arrhythmias, and therapeutic or prophylactic substrate modification ablation for VT/VF in this patient population with ICDs was not taken. We could have learned much more from this study, which gathered a vast amount of technical information from one of the largest remote monitoring databases. Nonetheless, given the optimism derived from this study, we should be able to generate a few hypotheses that can be evaluated prospectively in the future.A significant number of patients with ICDs experience both appropriate and inappropriate shocks in the form of “electrical storms.” Although not a perfect comparison, I cannot help comparing cardiac “electrical storms” to “meteorological storms.” Taking that analogy, most weather storms, hurricanes, blizzards, and tornados can be assessed for their strength ahead of time and even tracked successfully so that appropriate actions can be taken to minimize destruction, damage, and loss of human and nonhuman lives. It would be nice if we had a foolproof practical system or technology that could predict and track cardiac “electrical storms” in patients with ICDs so that with adequate alert appropriate management actions could be taken promptly. In that regard, I believe, studies such the one reported here not only are necessary but ultimately will lead to improved and more uniform practice standards to predict, prevent, and minimize both appropriate and inappropriate ICD shocks. Beyond their principal role of successfully detecting and treating ventricular tachycardia (VT) and ventricular fibrillation (VF) with overdrive antitachycardia pacing and defibrillation shocks, modern implantable cardioverter-defibrillators (ICDs) are capable of providing sophisticated pacing and resynchronization therapy. They store enormous amounts of technical and patient-related data, such as arrhythmia burden and heart failure status. Device manufacturers recently introduced “remote monitoring” technology, which allows home transmitters to interrogate devices and to download and transmit collected and stored data via the Internet to a protected network. Remote monitoring not only has rapidly shifted the paradigm in device follow-up but has heightened interest in exploring the wealth of available information to better understand device functionality and disease substrates. Irrespective of the indications for ICD placement, given the associated risk factors and comorbidities, the majority of recipients also would be prone, if they have not already experienced, to develop atrial fibrillation (AF). The presence of AF, with its 5% to 30% incidence in the ICD population, is not merely a “nuisance” because it has many detrimental effects.1Botto G.L. Luzi M. Ruffa F. Russo G. Ferrari G. Atrial tachyarrhythmias in primary and secondary prevention ICD recipients: clinical and prognostic data.Pacing Clin Electrophysiol. 2006; : S48-S53Crossref PubMed Scopus (6) Google Scholar, 2Borleffs C.J. van Rees J.B. van Welsenes G.H. et al.Prognostic importance of atrial fibrillation in implantable cardioverter-defibrillator patients.J Am Coll Cardiol. 2010; 55: 879-885Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar Paroxysmal, persistent, and permanent AF have hazard ratios (HRs) (95% confidence interval] of 1.3 (0.7–2.5), 1.2 (0.6–2.2), and 1.7 (1.0–2.7), respectively, for mortality and 1.2 (0.6–2.2), 1.1 (0.5–2.4), and 2.4 (1.5–4.0), respectively, for appropriate ICD shocks.2Borleffs C.J. van Rees J.B. van Welsenes G.H. et al.Prognostic importance of atrial fibrillation in implantable cardioverter-defibrillator patients.J Am Coll Cardiol. 2010; 55: 879-885Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar A newly detected AF within the first 3 months of ICD placement carries a significant risk for death with HR of 2.86 (1.02–8.05).3Bunch T.J. Day J.D. Olshansky B. et al.Newly detected atrial fibrillation in patients with an implantable cardioverter-defibrillator is a strong risk marker of increased mortality.Heart Rhythm. 2009; 6: 2-8Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar In patients with left ventricular dysfunction, persistent AF has been shown to cause appropriate ICD shocks and deterioration of heart failure.4Rienstra M. Smit M.D. Nieuwland W. et al.Persistent atrial fibrillation is associated with appropriate shocks and heart failure in patients with left ventricular dysfunction treated with an implantable cardioverter defibrillator.Am Heart J. 2007; 153: 120-126Abstract Full Text Full Text PDF PubMed Scopus (38) Google Scholar Furthermore, AF may be proarrhythmic. In the Jewel AF trial, 8.6% of all VT/VF episodes were found to have AF as a preceding or concomitant rhythm.5Stein K.M. Euler D.E. Mehra R. et al.Do atrial tachyarrhythmias beget ventricular tachyarrhythmias in defibrillator recipients?.J Am Coll Cardiol. 2002; 40: 335-340Abstract Full Text Full Text PDF PubMed Scopus (104) Google Scholar Interestingly, for consecutive episodes of VT/VF, time to next episode of VT/VF was longer when AF terminated than when it persisted.5Stein K.M. Euler D.E. Mehra R. et al.Do atrial tachyarrhythmias beget ventricular tachyarrhythmias in defibrillator recipients?.J Am Coll Cardiol. 2002; 40: 335-340Abstract Full Text Full Text PDF PubMed Scopus (104) Google Scholar From the device programming standpoint, “inappropriate shocks” due to AF are a complex issue. Data from small ICD registries as well as large prospective trials indicate that AF is the leading cause of inappropriate ICD shocks, with HRs of 2.0 to 2.9.6Nanthakumar K. Dorian P. Paquette M. et al.Is inappropriate implantable defibrillator shock therapy predictable?.J Interv Card Electrophysiol. 2003; 8: 215-220Crossref PubMed Scopus (45) Google Scholar, 7van Rees J.B. Borleffs C.J. de Bie M.K. et al.Inappropriate implantable cardioverter-defibrillator shocks: incidence, predictors, and impact on mortality.J Am Coll Cardiol. 2011; 57: 556-562Abstract Full Text Full Text PDF PubMed Scopus (326) Google Scholar, 8Daubert J.P. Zareba W. Cannom D.S. et al.Inappropriate implantable cardioverter-defibrillator shocks in MADIT II: frequency, mechanisms, predictors, and survival impact.J Am Coll Cardiol. 2008; 51: 1357-1365Abstract Full Text Full Text PDF PubMed Scopus (659) Google Scholar The time to first “inappropriate shocks” due to AF also depends on the severity of heart failure. In patients with New York Heart Association (NYHA) class III or IV heart failure, the 1- and 2-year “inappropriate” shock-free survival is reported to be 79% and 70% compared to 92% and 88% for patients in NYHA class I or II heart failure, respectively.9Hreybe H. Ezzeddine R. Barrington W. et al.Relation of advanced heart failure symptoms to risk of inappropriate defibrillator shocks.Am J Cardiol. 2006; 97: 544-546Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar To prevent “inappropriate shocks” resulting from supraventricular tachyarrhythmias, several rhythm discrimination algorithms have been developed. These algorithms are device-manufacturer specific and in many cases are device-model specific. The shortcomings of rhythm discrimination algorithms may occur in two ways: (1) when attempting to determine the true nature of the arrhythmia and valuable time elapses while treating the arrhythmia appropriately; and (2) when the ventricular rate is too rapid and erring on the side of caution results in the ICD delivering shocks anyway. Strategic programming of ICDs prevents “inappropriate shocks” and reduces “appropriate-but-unnecessary shocks.” In the PREPARE (Primary Prevention Parameters Evaluation) study, when the key programming strategies of (1) detecting only fast tachycardias (VT/VF rates ≥182 bpm, (2) detecting only sustained tachycardias (VT/VF maintained for at least 30–40 beats, (3) applying antitachycardia pacing as first therapy for fast VTs with rates of 182–250 bpm, (4) using supraventricular tachyarrhythmia discriminators for rhythms ≥200 bpm; and (5) using high-output first shock, the morbidity index (combined incidence of device-delivered shocks, arrhythmic syncope, and untreated sustained symptomatic VT/VF) was found to be significantly lower at 0.26 events per patient-year vs 0.69 events per patient-year in the control setting.10Wilkoff B.L. Williamson B.D. Stern R.S. et al.Strategic programming of detection and therapy parameters in implantable cardioverter-defibrillators reduces shocks in primary prevention patients: results from the PREPARE (Primary Prevention Parameters Evaluation) study.J Am Coll Cardiol. 2008; 52: 541-550Abstract Full Text Full Text PDF PubMed Scopus (454) Google Scholar With regard to “remote monitoring,” several studies, notably the ALTITUDE survival study, the CONNECT (Clinical Evaluation of Remote Notification to Reduce Time to Clinical Decision) study, and the TRUST (the Lumos-T Safely Reduces Routine Office Device Follow-Up) trial, using LATITUDE (Boston Scientific Corporation, Natick, MA, USA), CareLink Network (Medtronic, Inc, Minneapolis, MN, USA), and Home Monitoring (Biotronik, Berlin, Germany), respectively, showed that remote monitoring technology is safe, allows more rapid detection of actionable events, reduces time to clinical intervention, and improves patients survival.11Saxon L.A. Hayes D.L. Gilliam F.R. et al.Long-term outcome after ICD and CRT implantation and influence of remote device follow-up: the ALTITUDE survival study.Circulation. 2010; 122: 2359-2367Crossref PubMed Scopus (408) Google Scholar, 12Crossley G.H. Boyle A. Vitense H. et al.The CONNECT (Clinical Evaluation of Remote Notification to Reduce Time to Clinical Decision) trial: the value of wireless remote monitoring with automatic clinician alerts.J Am Coll Cardiol. 2011; 57: 1181-1189Abstract Full Text Full Text PDF PubMed Scopus (394) Google Scholar, 13Varma N. Epstein A.E. Irimpen A. et al.Efficacy and safety of automatic remote monitoring for implantable cardioverter-defibrillator follow-up: the Lumos-T Safely Reduces Routine Office Device Follow-up (TRUST) trial.Circulation. 2010; 122: 325-332Crossref PubMed Scopus (442) Google Scholar However, adequate long-term follow-up data on remote monitoring are not available. In addition, the report of early withdrawal from remote monitoring of up to 7.1% of patients due to transmission failure despite use of the GSM network rather than analog phone-line technology in the TRUST trial is alarming.13Varma N. Epstein A.E. Irimpen A. et al.Efficacy and safety of automatic remote monitoring for implantable cardioverter-defibrillator follow-up: the Lumos-T Safely Reduces Routine Office Device Follow-up (TRUST) trial.Circulation. 2010; 122: 325-332Crossref PubMed Scopus (442) Google Scholar Remote monitoring has not yet become the standard of care. In busy physicians' practices, the process of retrieving data from manufacturers' repositories and checking daily reports, which require significant support from trained personnel, may be overwhelming. Plus, it is not possible to physically examine, evaluate, and perform intervention, including remote programming of ICDs. In a study by Fischer et al14Fischer A. Ousdigian K.T. Johnson J.W. Gillberg J.M. Wilkoff B.L. The impact of atrial fibrillation with rapid ventricular rates and device programming on shocks in 106,513 ICD and CRT-D patients.Heart Rhythm. 2012; 9: 24-31Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar reported in this issue of HeartRhythm, the authors evaluated a very large patient population by retrospective observational analysis for the impact of AF and device programming on ICD shocks using a remote monitoring system. The main findings of the study were as follows: (1) 21% of patients received ICD shocks over a follow-up period of 2.5 ± 1.4 years, and (2) patients with AF with rapid ventricular rate whose devices were programmed with slower VT/VF detection thresholds and shorter VF detection intervals were associated with more shocks. To clinicians who treat patients with ICDs, heart failure, and AF, such results are not surprising. The authors' attempts to define AF with or without a rapid ventricular response and no/little AF based on the duration of AF and average ventricular rate and further defining it into paroxysmal, persistent, or permanent AF have scientific merit. However, one of the major limitations of the study is the lack of clinical data and the fact that no attempts were made toward adjudication of ICD shocks. How many patients received “appropriate” vs “inappropriate” shocks is unknown. In addition, whether patients who received shocks were sicker with worse heart failure and comorbidities and were less well treated than patients without shocks is unknown. Without the clinical variables, the association of ICD programming with shocks is questionable. Likewise, due to the lack of clinical data, one should be cautious in drawing conclusions about continuous monitoring of AF with rapid ventricular rate being a predictor of future ICD shocks. The topics of antiarrhythmic drugs, statins, and other upstream pharmacologic therapies and ablation therapies in the patient population with ICDs, heart failure, and arrhythmias are constantly debated. The opportunity to learn more about the role and impact of antiarrhythmic drugs, ablative procedures such as pulmonary vein isolation and left and right atrial ablation for atrial arrhythmias, and therapeutic or prophylactic substrate modification ablation for VT/VF in this patient population with ICDs was not taken. We could have learned much more from this study, which gathered a vast amount of technical information from one of the largest remote monitoring databases. Nonetheless, given the optimism derived from this study, we should be able to generate a few hypotheses that can be evaluated prospectively in the future. A significant number of patients with ICDs experience both appropriate and inappropriate shocks in the form of “electrical storms.” Although not a perfect comparison, I cannot help comparing cardiac “electrical storms” to “meteorological storms.” Taking that analogy, most weather storms, hurricanes, blizzards, and tornados can be assessed for their strength ahead of time and even tracked successfully so that appropriate actions can be taken to minimize destruction, damage, and loss of human and nonhuman lives. It would be nice if we had a foolproof practical system or technology that could predict and track cardiac “electrical storms” in patients with ICDs so that with adequate alert appropriate management actions could be taken promptly. In that regard, I believe, studies such the one reported here not only are necessary but ultimately will lead to improved and more uniform practice standards to predict, prevent, and minimize both appropriate and inappropriate ICD shocks. The impact of atrial fibrillation with rapid ventricular rates and device programming on shocks in 106,513 ICD and CRT-D patientsHeart RhythmVol. 9Issue 1PreviewThe relationship between shocks, device programming, and atrial fibrillation (AF) with a rapid ventricular rate (AF + RVR) using continuous daily monitoring has not been studied in large number of patients with implantable cardioverter-defibrillators (ICDs). Full-Text PDF