Impact of the Multicenter Automatic Defibrillator Implantation Trial on Clinical Practice

Background: The first multicenter automatic defibrillator implantation trial (MADIT‐I) was a landmark study that identified a significant reduction in mortality among high‐risk patients with ischemic cardiomyopathy treated prophylactically with an implantable cardioverter defibrillator (ICD), yet the direct and indirect impact of this trial on clinical practice is unknown. Methods: We performed a retrospective analysis of the 679 patients who underwent primary ICD implantation between 1994 and 2000 at a single academic center. The baseline characteristics of each patient were determined at the time of ICD implantation, and the vital status of all patients was determined as of January 1, 2004. Results: The number of patients who received an ICD based on the MADIT‐I criteria increased from 1.4% in 1994 to 6.1% in 2000. An additional 60 patients were identified that met many but not all of the trial criteria and consisted of patients with a history of a recent revascularization or myocardial infarction, syncope, or an ejection fraction ≥35%. The number of patients who received ICDs in this expanded MADIT‐I subset also grew from 5.6% in 1994 to 14.6% in 2000. Mortality during a mean follow‐up of 4.7 years was significantly higher in the MADIT‐I group than in the expanded MADIT‐I, or the remaining primary prevention and secondary prevention subsets. Conclusion: The MADIT‐I has not only led to an increase in the number of patients undergoing prophylactic ICD implantation, but in clinical practice it has also been extrapolated to a broader population that has a different degree of risk than originally studied.     

Comparison of Three Different Automatic Defibrillator Implantation Approaches: Pectoral Implantation Using Conscious Sedation Reduces Procedure Times and Cost

Recent technological advances in implantable defibrillator systems(ICD) have changed implantation approaches. The aim of this study was toinvestigate the influence of these improvements on procedure times,implant-related charges, patient recovery, and morbidity. Ninety-sixconsecutive patients undergoing implantation of a nonthoracotomy ICD werestudied. Implantation was performed under general anesthesia with thegenerator placed abdominally in 22 patients (group I) and pectorally in 40patients (group II). Thirty-four patients underwent pectoral implantationusing conscious sedation (group III). Groups were comparable with respect toclinical variables. Implantation duration and total procedure duration wereshorter in group III (67 ± 21 minutes and 117 ± 30 minutes)when compared with group I (100 ± 25 minutes and 157 ± 39minutes) and group II (86 ± 24 minutes and 153 ± 34 minutes, P< 0.05). Patients in group III did not require admission to thePost-Anesthesia Care Unit. In contrast, patients in groups I and II spent 92± 28 minutes and 91 ± 31 minutes in the Post-Anesthesia CareUnit. Implantation-related charges were reduced in patients having pectoralimplantation using conscious sedation ($1451 ± 217 vs.$2354 ± 550 and $2796 ± 384, P < 0.05).Patients in group III had a lower frequency of postoperative oral analgesicuse (3.2 ± 2.7 doses, P < 0.05) and a shortened postoperative length of stay (1.9 ± 1.6 days, P < 0.05) when compared withgroups I (5.7 ± 4.0 doses and 3.3 ± 1.4 days) and II (5.2± 3.5 doses and 2.6 ± 1.1 days). The overall complication ratewas low (6.3%), with no differences between groups. Advances in ICDtechnology have simplified implantation, leading to shorter, less painful,and less expensive procedures.     

Feasibility of Defibrillation and Automatic Arrhythmia Detection Using an Exclusively Subcutaneous Defibrillator System in Canines

Subcutaneous Defibrillation in Canines. Introduction: This study reports the experimental process leading to development of an automatic totally subcutaneous implantable cardioverter defibrillator (SICD) system engineered for human use. Methods and Results: Two studies were conducted to test defibrillation and detection feasibility of an SICD system located in the left chest. In the first study, 2 pockets were created in 15 canines for placement of an anterior electrode adjacent to the left edge of the sternum and a lateral electrode at the site along the axillary line between the 4th and 6th intercostal space. Stainless steel flat electrodes with active surface areas of 5, 10, 20, and 25 cm² or rod electrodes were subsequently positioned and the defibrillation threshold (DFT) was measured for multiple combinations. In the second study, the ability to induce, detect, and provide shock delivery in response to ventricular fibrillation (VF) using an SICD system engineered for clinical use was tested in 5 canines. One hundred and three DFT tests with 11 different dual electrode combinations were performed. All combinations terminated VF with a DFT of 35 ± 16 J (range: 9–79 J). Nineteen VF episodes were induced and recognized by the chronic SICD, leading to automatic capacitor charge and shock delivery in all cases. Conclusions: Subcutaneous defibrillation using different electrode combinations with shock energies less than 80 J terminated all induced VFs. An automatic SICD proved effective in detecting and activating shock delivery in all cases. (J Cardiovasc Electrophysiol, Vol. 24, pp. 77‐82, January 2013)     

Case Report: Inappropriate Implantable Cardioverter Defibrillator Discharge from Sensing of External Alternating Current Leak

Implantable cardioverter defibrillators (ICDs) are now an accepted and effective therapy for treatment of survivors of sudden cardiac death (SCD) and prevention of SCD in high-risk patients. Normal ICD function and delivery of therapy depends on appropriate sensing and detection of myocardial electrical potentials. Electromagnetic interference resulting in ICD malfunction is a well-documented phenomenon, however, there are less well-known external sources of interference, which may cause life threatening ICD malfunction. We report a unique case of repeated inappropriate ICD shocks in a ten-year old boy caused by the ICD sensing alternating current from an unexpected external source.     

埋藏式心脏转复除颤器安置的临床经验

总结非开胸经锁骨下静脉穿刺安置埋藏式心脏转复除颤器 (ICD)的手术方法、除颤阈值 (DFT)测定及ICD工作参数设置等临床经验。 10例患者 ,6例有反复晕厥病史。 2例晕厥时心电图证实为心室颤动 (简称室颤 ) ,体外电除颤成功 ,另 8例心内电生理均诱发出持续性室性心动过速或室颤。其中冠心病 8例 (1例合并Brugada综合征 ) ,扩张性心肌病 1例 ,原发性室颤 1例。 5例术前口服胺碘酮治疗。结果 :全部经锁骨下静脉置入ICD ,术中所有患者成功诱发室颤 ,并一次电击成功。手术时间 92± 2 7min。DFT≤ 2 0J,电击阻抗 4 1.2± 15 .3Ω ,R波高度 16 .3± 6 .6mV ,无手术并发症。结论 :经锁骨下静脉置入ICD方法简单 ,安全可靠 ;术前口服适量胺碘酮对术中诱发室颤无影响。     

In-hospital experience with multiprogrammable implantable antitachycardia/antifibrillation devices

Multiprogrammable, automatic internal defibrillators with (n= 45) and without (n = 15) antitachycardia pacing features wereimplanted in 60 consecutive patients with refractory, malignantventricular tachycardia (VT) (n = 42) or fibrillation (VF) (n= 18). Left ventricular (LV) ejectionfraction wasreduced to39% ± 12% as a result of structural heart disease in56 patients. The complexity of the systems caused no additionalrisks to the surgical procedure or postoperative management.VT/VF detection parameters were individually adjusted to thearrhythmia type (detection cycle length 323 ± 40 ms inpatients with VF vs 405 ± 40 ms for VT patients, P<0.05)and incidence (longer detection periods if frequent nonsustainedVT was also present). Shock energy was reduced in patients withVT as compared to VF(11J vs 24J, P<0.05). Antitachycardiapacing was activated in 19/28 (68%) patients with well toleratedVT. Signal, telemetry, as detected by the device, combined withprogrammability allowed the device to be checked for correctdecisions (these were inappropriate in four patients in threeof whom corrections were non-invasive) prior to discharge. Inconclusion, in the automatic tachyarrhythmia control deviceswe studied, programmability and flexibility appeared to be clinicallysafe and useful. Prolonged observation periods are required,however, to evaluate the true clinical safety and persistentefficacy of device programmability and flexibility.     

Exploding Implantable Cardioverter Defibrillator

A 79-year-old man with a pectoral implantable cardioverter defibrillator (ICD) system underwent periodic defibrillation threshold testing 18 months after implant. Attempted delivery of a 15-J shock caused a light flash above the pocket and a loud "pop." High-voltage lead impedance was <20 ohms. Pocket exploration revealed insulation abrasion of the high-voltage portion of the single-coil right ventricular lead. The outer shield of the active can pulse was perforated and scorched due to arcing. Device analysis confirmed a shorted transistor in the high-voltage output circuit. Unsuspected physical contact between high-voltage electrodes of opposite polarity within the pocket can cause catastrophic ICD system failure.     

Incidence of nonsustained and sustained ventricular tachyarrhythmias in patients with an implantable cardioverter defibrillator

INTRODUCTION: Nonsustained ventricular tachycardia (NSVT) is a frequent phenomenon in some patients with heart disease, but its association with sustained ventricular tachycardias (ventricular tachycardia [VT]/ventricular fibrillation [VF]) is still not clear. The aim of this study was to determine whether NSVT incidence was associated with sustained VT/VF in patients with an implantable cardioverter defibrillator (ICD). METHODS AND RESULTS: Retrospective data analysis was conducted in 923 ICD patients with a mean follow-up of 4 months. NSVT and sustained VT/VF were defined as device-detected tachycardias. The incidence rates of NSVT and sustained VT/VF as well as ICD therapies were determined as episodes per patient. The NSVT index was defined as the product of NSVT episodes/day times the mean number of beats per episode, i.e., total beats/day. The NSVT index peak was defined as the highest value on or prior to the day with sustained VT/VF episodes. Patients (n = 393) with NSVT experienced a higher incidence of sustained VT/VF (17.2 +/- 63.0 episodes/patient) and ICD therapies (15.2 +/- 61.4 episodes/patient) than patients (n = 530) without NSVT (sustained VT/VF: 0.5 +/- 6.6 and therapies: 0.5 +/- 5.6; P < 0.0001). Approximately 74% of NSVT index peaks occurred on the same day or <3 days prior to sustained VT/VF episodes. The index was higher for peaks < or =3 days prior to the day with sustained VT/VF (94.3 +/- 140.1 total beats/day) than for peaks >3 days prior to the day with sustained VT/VF (32.7 +/- 55.9 total beats/day; P < 0.0001). CONCLUSION: ICD patients with NSVT represent a population more likely to experience sustained VT/VF episodes with a temporal association between an NSVT surge and sustained VT/VF occurrence.     

Implantable Cardioverter Defibrillator Oversensing During Periods of Rate-Related Bundle Branch Block

ICD Oversensing During Rate-Related BBB. A patient with an implantable cardioverter defibrillator (ICD) and a dual chamber pacemaker experienced inappropriate ICD therapies only during periods of rate-dependent right bundle branch block. Analysis of both stored and real-time ICD electrograms was critical to correctly diagnosing the problem and offering a solution.     

Diagnostic Value of Single Versus Dual Chamber Electrograms Recorded from an Implantable Defibrillator

Introduction: The clinical utility of ventricular electrograms in comparison to atrial and ventricular electrograms in diagnosing the type of tachycardias recorded by an implantable defibrillator has not been addressed from the standpoint of a clinician's diagnostic accuracy and confidence in that diagnosis. Methods: Fifty-two tachycardia episodes recorded from dual chamber defibrillators were divided into two tests. The initial test contained only information from the ventricular electrogram and the second test contained information from both the atrial and ventricular electrograms. For each test, the reviewers were asked to provide the specific diagnosis, the originating chamber of origin of the tachycardia, and the confidence of their responses for each question. McNemar's test for matched pairs was used to determine accuracy and an analysis of variance to determine reviewer confidence. Results: The overall accuracy for both the specific diagnosis (61% vs. 79%; p < 0.001) and the chamber of origin (76% vs. 90%; p < 0.001) improved when both the atrial and ventricular electrograms were available for review. Reviewer confidence appeared to correlate with diagnostic accuracy. Conclusions: The data clearly show the favorable impact of dual chamber defibrillators on the diagnostic accuracy and confidence of clinicians faced with a clinical tachycardia recorded from an implantable defibrillator. Such improvements may translate into more focused and appropriate therapeutic interventions.     

Prevention of recurrent ventricular fibrillation by ventricular rate stabilization.

This report describes a post-infarct patient with recurrent ventricular fibrillation in the absence of acute ischaemia, in whom arrhythmia recurrences could be prevented by ventricular rate stabilization of a third-generation cardioverter defibrillator. Review of the literature and clinical implications are discussed.     

Survey of Prophylactic Defibrillator Implantation Following MADIT

The Multicenter Automatic Defibrillator Implantation Trial (MADIT) established an indication for implantable defibrillators (ICD) in patients with previous infarction, ejection fraction (EF) < 35%, nonsustained ventricular tachycardia (VT), and inducible sustained VT not suppressed by Class I drugs. Few data exist regarding implementation of this indication in clinical practice. We surveyed 72 active ICD implanting centers (26 United States, 46 Europe) with respect to screening and implantation practices related to MADIT for the year 1998. Prophylactic ICD implantation using MADIT indications comprised 9% of all initial implants (15% United States, 9% Germany, 5% other European), but ranged broadly from 0% (11 centers) to < 20% (7 centers). Implant rate was related to total annual ICD volume: 13% at high volume (> 100) and 7% at low volume (< 40) centers. Only 4% of responders conducted systematic Holter screening of postinfarction patients with low EF, and 41% screened for MADIT indications only in patients referred specifically for that purpose. Among implanting physicians (1) 61% do not routinely perform drug testing following induction of qualifying VT, (2) 38% would implant an ICD in selected patients with nonsustained VT and EF < 35% if qualifying VT was induced, (3) 18% would implant ICDs in selected patients without nonsustained VT, but with EF< 35% if qualifying VT was induced. Extrapolation of these results to the total number of new implants in 1998 suggests that approximately 5000 ICDs were placed for MADIT indications. However, individual practices were highly variable, with some extrapolation from strict indications based on patient presentation and physician judgment. A.N.E. 2000; 5(3):248–254     

Cardioversor desfibrilhador implantável subcutâneo – experiência de um centro

BackgroundImplantable cardioverter‐defibrillators (ICDs) are important tools in the prevention of sudden death, but implantation requires transvenous access, which is associated with complications. Subcutaneous implantable cardioverter‐defibrillators (S‐ICDs) may prevent some of these complications.AimTo evaluate the therapeutics and complications associated with S‐ICD systems.MethodsS‐ICD implantation was planned in 23 patients, for whom the indications were vascular access problems, increased risk of infection or young patients with long predicted follow‐up. The population consisted of four patients with ischemic heart disease, three of them on hemodialysis (two with subclavian vein thrombosis), five with left ventricular noncompaction, four with Brugada syndrome, three with arrhythmogenic right ventricular cardiomyopathy, one with transposition of the great vessels, two with dilated cardiomyopathy and four with hypertrophic cardiomyopathy.ResultsS‐ICDs were implanted in 21 patients, two having failed to fulfil the initial screening criteria. Mean implantation time was 77 minutes, with no complications. Defibrillation tests were performed, and in one patient the generator had to be repositioned to obtain an acceptable threshold.In a mean follow‐up of 14 months, 10 patients had S‐ICD shocks, which were appropriate in half of them; one developed infection, one needed early replacement due to loss of telemetry and one patient died of noncardiac cause.ConclusionsS‐ICD implantation can be performed by cardiologists with a high success rate. Initial experience appears favorable, but further studies are needed with longer follow‐up times to assess the safety and efficacy of this strategy compared to conventional devices.     

Fatal outcome from inappropriate defibrillation

We present a 51-year-old morbidly obese man who underwent insertionof a single-chamber implantable cardioverter defibrillator formonomorphic ventricular tachycardia occurring after myocardialinfarction. After a period of satisfactory device function,a sudden change in R-wave with atrial over-sensing heraldedinappropriate defibrillation and induction of ventricular fibrillation,with subsequent death of the patient.     

Clinical Experience with a Dual-Chamber Implantable Cardioverter Defibrillator to Treat Atrial Tachyarrhythmias

INTRODUCTION: This study evaluated the safety and efficacy of a new dual-chamber implantable cardioverter defibrillator (ICD) to detect and treat atrial tachyarrhythmias in patients with drug-refractory atrial fibrillation (AF) and no indication for a ventricular ICD. METHODS AND RESULTS: A dual-chamber ICD (Medtronic 7250 Jewel AF) was implanted in 144 of 146 patients. The device discriminates atrial tachycardia from AF based on cycle length and regularity, and uses atrial overdrive pacing as well as shocks to terminate tachyarrhythmia episodes. Patients were followed for an average of 12.6+/-6.2 months. Use of antiarrhythmic drugs was 63% at baseline and did not change over time. Kaplan-Meier estimates of 12-month complication-free survival, device therapy survival, and patient survival were 85%, 91%, and 98%, respectively. Positive predictive accuracy of spontaneous atrial tachyarrhythmia detection was 99%, while atrial overdrive pacing and shocks terminated 40% and 87% of treated episodes, respectively. Median duration of successfully treated episodes was 8.9 minutes versus 144 minutes for the therapy failures. There was no reduction in the use of patient-activated shock therapy over time; at the 12-month follow-up evaluation, 94% of patients were in sinus rhythm. Ventricular tachyarrhythmias (67 episodes) were detected and appropriately treated in 7.6% of patients. CONCLUSION: This dual-chamber ICD appears to be safe and well tolerated in patients with drug-refractory symptomatic atrial tachyarrhythmias. The device, used in combination with drugs, effectively treats atrial tachyarrhythmias with pacing and/or shock therapies and decreases the median episode duration. In addition, the device protects from ventricular tachyarrhythmias in patients with AF and structural heart disease.     

Atrial Fibrillation/Flutter Induced by Implantable Ventricular Defibrillator Shocks:

Atrial Fibrillation/Flutter Induced by Defibrillator Shocks. Introduction : We evaluated the incidence and energy dependence of atrial fibrillation/flutter (AF) induced by implantable ventricular defibrillator shocks in 63 patients tested in the operating room or electrophysiology laboratory.
Methods and Results : Defibrillator shocks were epicardial monophasic in 32 patients, and through an Endotak® lead endocardial monophasic in 19 and biphasic in 12 patients. The epicardial and endocardial patient groups had similar clinical characteristics. A total of 517 defibrillator shocks were given. The epicardial group received 336 total defibrillator shocks and 10 ± 6 shocks (mean ± SD) per patient compared with the endocardial group, which received 181 total shocks and 6 ± 4 defibrillator shocks per patient (P = 0.004). In the epicardial group, AF occurred in 13 (41 %) patients and in 17 (5%) of the 336 shocks. No AF was induced with endocardial defibrillator shocks. The epicardial mean energy was 16 ± 9 J, lower than the endocardial mean energy of 20 ± 9 J (P < 0.004). In the epicardial monophasic group, energy correlated with AF induction. Each patient received 7 ± 6 defibrillator shocks < 15 J and 4 ± 2 shocks ≥ 15 J, yet AF occurred in only 2.3% versus 9.6% (P < 0.05) of defibrillator shocks < 15 J and ≥ 15 J, respectively. Of note, AF was not induced with energy < 4 J or > 31 J.
Conclusions : In the epicardial configuration, AF induction is energy dependent, with an apparent lower and upper limit of vulnerability. AF induction by defibrillator shocks delivered through an Endotak lead is very rare, possibly related to an apparent upper limit of vulnerability of less energy, avoidance of thoracotomy, or different energy field distribution.     

Body Surface Potentials During Discharge of the Implantable Cardioverter Defibrillator

Body Surface Potentials During ICD Discharge. Introduction: Little is known about the hazard for persons in contact with patients experiencing a high-voltage discharge of their implantable cardioverter defibrillator (ICD). Compared to epicardial systems, this risk may be increased with transvenous electrode systems and particularly in active can configurations. Methods and Results: In 23 patients with a transvenous active can ICD system, body surface potentials V_S and current through an external resistance were measured during 35 discharges. V_S was detected using skin electrodes positioned over the left subpectorally implanted pulse generator [C], apex of the heart [A], and the right pectoral region [RP]. Mean V_S during discharges without an external shunt resistance ranged between 13 and 63.8 V [C to A] and 12.5 to 47.3 V [C to RP] (ICD peak stored/output voltage V_cap= 183 to 606 V, n = 20). Mean current flow [C to A] was 8.2 to 46.8 mA (V_cap= 288 to 633 V. n = 10) and 42 to 120.7 mA (V_cap= 447 to 579 V, n = 5) across a resistance of 1.696 and 797 ω, respectively. Conclusion: During high-output shocks, a considerable potential difference is present on the hody surface of ICD patients that, according to the literature, may induce a single cardiac response in a bystander. Analogous to spontaneous extrasystoles, there is only a minimal chance of triggering a tachyarrhythmia by this stimulated extra beat. Direct induction of ventricular fibrillation is unlikely, since reported fibrillation threshold values are much higher than the ohserved magnitudes of current and voltage.