A Modular Communicative Leadless Pacing-Defibrillator System

BACKGROUND

The subcutaneous implantable cardioverter-defibrillator (ICD) is associated with fewer lead-related complications than a transvenous ICD; however, the subcutaneous ICD cannot provide bradycardia and antitachycardia pacing. Whether a modular pacing-defibrillator system comprising a leadless pacemaker in wireless communication with a subcutaneous ICD to provide antitachycardia and bradycardia pacing is safe remains unknown.

METHODS

We conducted a multinational, single-group study that enrolled patients at risk for sudden death from ventricular arrhythmias and followed them for 6 months after implantation of a modular pacemaker-defibrillator system. The safety end point was freedom from leadless pacemaker-related major complications, evaluated against a performance goal of 86%. The two primary performance end points were successful communication between the pacemaker and the ICD (performance goal, 88%) and a pacing threshold of up to 2.0 V at a 0.4-msec pulse width (performance goal, 80%).

RESULTS

We enrolled 293 patients, 162 of whom were in the 6-month end-point cohort and 151 of whom completed the 6-month follow-up period. The mean age of the patients was 60 years, 16.7% were women, and the mean (±SD) left ventricular ejection fraction was 33.1±12.6%. The percentage of patients who were free from leadless pacemaker-related major complications was 97.5%, which exceeded the prespecified performance goal. Wireless-device communication was successful in 98.8% of communication tests, which exceeded the prespecified goal. Of 151 patients, 147 (97.4%) had pacing thresholds of 2.0 V or less, which exceeded the prespecified goal. The percentage of episodes of arrhythmia that were successfully terminated by antitachycardia pacing was 61.3%, and there were no episodes for which antitachycardia pacing was not delivered owing to communication failure. Of 162 patients, 8 died (4.9%); none of the deaths were deemed to be related to arrhythmias or the implantation procedure.

CONCLUSIONS

The leadless pacemaker in wireless communication with a subcutaneous ICD exceeded performance goals for freedom from major complications related to the leadless pacemaker, for communication between the leadless pacemaker and subcutaneous ICD, and for the percentage of patients with a pacing threshold up to 2.0 V at a 0.4-msec pulse width at 6 months. (Funded by Boston Scientific; MODULAR ATP ClinicalTrials.gov NCT04798768.).

Design and rationale of the MODULAR ATP global clinical trial: A novel intercommunicative leadless pacing system and the subcutaneous implantable cardioverter-defibrillator

Background

The subcutaneous implantable cardioverter-defibrillator (S-ICD) has demonstrated safety and efficacy for the treatment of malignant ventricular arrhythmias. However, a limitation of the S-ICD lies in the inability to either pace-terminate ventricular tachycardia or provide prolonged bradycardia pacing support.

Objective

The rationale and design of a prospective, single-arm, multinational trial of an intercommunicative leadless pacing system integrated with the S-ICD will be presented.

Methods

A technical description of the modular cardiac rhythm management (mCRM) system (EMPOWER leadless pacemaker and EMBLEM S-ICD) and the implantation procedure is provided. MODULAR ATP (Effectiveness of the EMPOWER™ Modular Pacing System and EMBLEM™ Subcutaneous ICD to Communicate Antitachycardia Pacing) is a multicenter, international trial enrolling up to 300 patients at risk of sudden cardiac death at up to 60 centers trial design. The safety endpoint of freedom from major complications related to the mCRM system or implantation procedure at 6 months and 2 years are significantly higher than 86% and 81%, respectively, and all-cause survival is significantly >85% at 2 years.

Results

Efficacy endpoints are that at 6 months mCRM communication success is significantly higher than 88% and the percentage of subjects with low and stable thresholds is significantly higher than 80%. Substudies to evaluate rate-responsive features and performance of the pacing module are also described.

Conclusion

The MODULAR ATP global clinical trial will prospectively test the safety and efficacy of the first intercommunicating leadless pacing system with the S-ICD. This trial will allow for robust validation of device-device communication, pacing performance, rate responsiveness, and system safety.

P2857Implantable cardioverter defibrillator and pacemaker lead extraction: is it safe to do it again?

Background/Introduction

There are growing numbers of transvenous implantable devices for patients requiring permanent pacemakers (PPM) as well as Implantable Cardioverter Defibrillators (ICD). As such, there has been a concomitant increased need for lead extraction. Lead extraction is associated with increased morbidity and mortality (Hamid, 2010). Comparative outcomes of repeat lead extraction are not extensively studied.

Purpose

We compared demographics as well as major and minor adverse outcomes in patients undergoing first time vs. repeat lead extraction procedures.

Methods

In our single center study, 1278 extractions took place between January 2004 and December of 2018. Of these 1177 patients underwent PPM or ICD lead extraction for the first time; 101 patients underwent repeat extractions. Baseline characteristics including gender, history of coronary artery bypass graft (CABG) surgery, hypertension (HTN), systolic heart failure (HF) defined as ejection fraction <40%, hyperlipidemia (HLD), diabetes mellitus (DM), and coronary artery disease (CAD) were evaluated using chi-squared analysis. Adverse events, as defined by the 2017 HRS Expert Consensus Statement on Cardiovascular Implantable Electronic Device Lead Management and Extraction, were identified as major complications (death, cardiac arrest, cardiac perforation, coronary venous dissection, pericardial tamponade, or urgent cardiac surgery), and minor complications (coronary sinus dissection, pneumothorax, pocket bleeding requiring drainage, worsening tricuspid valve function, vegetation embolization, venous thrombosis, requirement of blood transfusion or lead migration).

Results

Comparing first time extractions vs repeat extractions, there was no significant difference in proportion of patients of female gender (32.4% vs. 28.3%, p=0.412), patients with prior CABG (23.0 vs. 23.4%, p=0.227), HTN (66.0% vs. 62.2%, p=0.462), HF (52.3% vs. 62.0%), HLD (39.6% vs 39.7%, p=0.682), DM (35.3% vs. 30.8%, p=0.387), or CAD (55.9% vs 56.0%, p=0.978). There was no significant difference in major complications (1.4% vs. 1.0%, p=0.749) and minor complications (3.5% vs 4.1%, p=0.741).

Conclusion

Patients undergoing repeat lead extractions showed very similar baseline demographics compared to first time lead extractions. Repeat extractions did not have increased rates of major or minor complications.

Differences of Mortality Rates between Pocket and Nonpocket Cardiovascular Implantable Electronic Device Infections

BACKGROUND

A steady rise in the use of cardiovascular implantable electronic devices (CIEDs), particularly in the elderly, has led to an increase in device-related infections. Although often studied and reported as a single entity, these complications in fact comprise a heterogeneous group. Specific subgroups may be associated with distinct mortality risks.

METHODS

Medical records of all patients who underwent device extraction for CIED-related infection at a single tertiary referral center between 1991 and 2007 were reviewed. Infections were divided into four subgroups: primary pocket site infection (PPSI), pocket site infection with bacteremia, primary/isolated bacteremia (PIB), and device-related infective endocarditis (DRIE). Clinical presentation, laboratory data, and mortality rates were obtained by chart review and by querying the Social Security Death Index.

RESULTS

A total of 387 cases were analyzed. The overall in-hospital and 1-year all-cause mortality rates were 7.2% and 25.3%, respectively. Patients with PIB or DRIE had significantly higher mortality rates (hazard ratio [HR] 2.3; 95% confidence interval [CI] 1.2-4.6 and HR 2.5; 95% CI 1.6-4.1, respectively) when compared with patients in the PPSI group. Patients who did not receive a new device during the initial admission also had a higher 1-year mortality rate compared to those who did (HR 2.7; 95% CI 1.8-4.1).

CONCLUSIONS

Our patients with CIED-related infections requiring extraction/hospitalization had a significant mortality risk. Presence of pocket site infection carried a more favorable prognosis, regardless of the presence of bacteremia. Early detection and prevention of CIED-related infections with PIB (i.e., no pocket site involvement), especially for high-risk populations, is needed.

Subcutaneous implantable cardioverter-defibrillator implantation in a patient with a left ventricular assist device already in place

A 56-year-old man with ischemic cardiomyopathy, a biventricular implantable cardioverter-defibrillator (ICD), and a left ventricular assist device (LVAD) developed a pocket hematoma and infection after an ICD generator change. The biventricular ICD was extracted, and the patient was given a full course of antibiotics. Because he had no indications for bradycardia pacing or biventricular pacing, he was implanted with a subcutaneous ICD under full anticoagulation. There was no interference in sensing or shock delivery from the ICD. The LVAD readings were unchanged during and after the procedure. The patient had an uneventful postoperative course, and both devices were functioning normally. To our knowledge, this is the first reported case of the implantation of a subcutaneous ICD in the presence of an LVAD. This report illustrates that both devices can be implanted successfully in the same patient. In addition, the subcutaneous ICD minimizes the risk of bloodstream infections, which can be fatal in patients who have life-supporting devices such as an LVAD.

Abstract 158: Ultrasound-Induced Inhibition and Modulation of Neonatal Ventricular Cardiomyocyte Depolarization

Background: Ultrasound can interact with tissue through either thermal or non-thermal physical mechanisms. Radiation force has been shown to stimulate cardiac and neural tissue in vivo. Ultrasound might hold clinical potential as a noninvasive therapeutic tool via specific bioeffects on cardiomyocytes. This study aims to assess the effect of ultrasound on cardiomyocyte depolarization in a tissue culture model.

Methods: Cardiomyocytes were isolated from neonatal rat ventricular tissue and plated directly on microelectrode arrays to record depolarization patterns. A custom 2.5 MHz unfocused ultrasound transducer was directed at the cardiomyocytes in a tissue culture model. A function generator, with an amplified signal +50 dB, delivered acoustic energy at variable settings of 0.1, 0.3, 0.5 and 1.0 Vpp, pulse durations of 2, 5 and 10 ms, and burst periods of 100, 250 and 300 ms. Five trials were conducted at each setting (36 total trials) with 30s of continuous ultrasound exposure followed by an off interval of 1 minute.

Results: The R-R interval durations (ID) were measured throughout the recording period. Prior to ultrasound delivery, the IDs were highly irregular, ID range = 0.3-2.7 s. As ultrasound was delivered in an asynchronous manner, using 0.1 and 0.3 Vpp and PD = 2 and 5 ms, there was suppression/inhibition of cellular depolarization for the first 5-10 s. Then 10-15 s after the start of ultrasound delivery, the depolarization rate increased and demonstrated less R-R interval variability (ID=0.88-1.03 s, P value<0.05), even after the ultrasound exposure.

Conclusion: Ultrasound can inhibit and modify the frequency of spontaneous electrical depolarizations of neonatal ventricular cardiomyocytes in a tissue culture model. Our observations could be due to conditioning via stretch and compression-mediated mechanosensitive pathways, by modifying intracellular calcium handling or altering cell signaling.

Protection from outpatient sudden cardiac death following ICD removal using a wearable cardioverter defibrillator

BACKGROUND

An implantable cardioverter defibrillator (ICD) is effective in preventing sudden cardiac death (SCD). Once an ICD is removed and reimplantation is not feasible, a wearable cardioverter defibrillator (WCD) may be an alternative option. We determined the effectiveness of WCD for SCD prevention in patients who were discharged after ICD removal.

METHODS

A retrospective study was conducted on all WCD (LifeVest, ZOLL, Pittsburgh, PA, USA) patients who underwent ICD removal due to cardiac device infections (CDIs) at two referral centers between January 1, 2005 and December 31, 2009. Clinical characteristics, device information, and WCD data were analyzed. Sudden cardiac arrest was defined as all sustained ventricular tachycardia (VT) and ventricular fibrillation occurring within a single 24-hour period.

RESULTS

Ninety-seven patients (mean age 62.8 ± 13.3, male 80.4%) were included in the study. The median duration of antibiotic use was 14.7 days (interquartile range [IQR] 10-30). The median daily WCD use was 20 hours/day and the median length of use was 21 days (IQR 5-47). A total of three patients were shocked by WCD. Two patients had four episodes of sustained VT, successfully terminated by the WCD. A third patient experienced two inappropriate treatments due to oversensitivity of the signal artifact. Three patients experienced sudden death outside the hospital while not wearing the device. Five patients died while hospitalized.

CONCLUSION

WCD can prevent SCD, until ICD reimplantation is feasible in patients who underwent device removals for CDI. However, patient compliance is essential for the effective use of this device.

ATPace™: injectable adenosine 5'-triphosphate : Diagnostic and therapeutic indications

ATPace™, a novel injectable formulation of adenosine 5'-triphosphate (ATP), is developed by Cordex Pharma, Inc. (Cordex) as a diagnostic and therapeutic drug for the management of cardiac bradyarrhythmias. Extracellular ATP exerts multiple effects in various cell types by activating cell-surface receptors known as P2 receptors. In the heart, ATP suppresses the automaticity of cardiac pacemakers and atrioventricular (AV) nodal conduction via adenosine, the product of its degradation by ecto-enzymes, as well as by triggering a cardio-cardiac vagal reflex. ATP, given as a rapid intravenous bolus injection, has been used since the late 1940s as a highly effective and safe therapeutic agent for the acute termination of reentrant paroxysmal supraventricular tachycardia (PSVT) involving the AV node. In addition, preliminary studies have shown that ATP can also be used as a diagnostic agent for the identification of several cardiac disorders including sinus node dysfunction (sick sinus syndrome), dual AV nodal pathways, long QT syndrome, and bradycardic syncope. The US Food and Drug Administration has approved Cordex formulation for ATP as an Investigational New Drug and two pathways for its marketing approval; one therapeutic, i.e., acute termination of paroxysmal PSVT, and the other diagnostic, i.e., the identification of patients with bradycardic syncope who can benefit from pacemaker therapy. The scientific rationale for the development of ATPace™ is discussed.

Decremental Ramp Atrial Extrastimuli Pacing Protocol for the Induction of Atrioventricular Nodal Re-entrant Tachycardia and Other Supraventricular Tachycardias

AIM

The primary aim of this study was to evaluate the utility of decremental ramp atrial extrastimuli pacing protocol (PRTCL) for induction of atrioventricular nodal re-entrant tachycardia (AVNRT), and other supraventricular tachycardias (SVTs), compared to standard (STD) methods.

METHODS

The study cohort of 121 patients (age 57.51 +/- 14.02 years) who presented with documented SVTs and/or symptoms of palpitations and dizziness, and underwent invasive electrophysiological evaluation was divided into Group I (AVNRT, n = 42) and Group II (Control, n = 79). The PRTCL involved a train of six atrial extrastimuli, delivered in a decremental ramp fashion. The STD methods included continuous burst and rapid incremental pacing up to atrioventricular (AV) block cycle length, and single and occasionally double atrial extrastimuli. Prolongation in the Atrio-Hisian (Delta-AH) intervals achieved by both methods were compared, as were induction frequencies.

RESULTS

In Group I, three categories of responses--(1) induction of AVNRT, (2) induction of echo beats only, and (3) none--were observed in 29 (69%), 11 (26%), and 2 (5%) patients with the PRTCL, when compared with 14 (33%), 16 (38%), and 12 (29%) patients with STD methods in the baseline state without the use of pharmacological agents. The Delta-AH intervals for each of these three categories were larger using PRTCL versus STD methods; 293.3 +/- 95.2 ms versus 192.9 +/- 61.4 ms (P < 0.005), 308.6 +/- 68.5 ms versus 189. 9 +/- 64.9 ms (P < 0.0005), and 203.0 +/- 86.3 ms versus 145.8 +/- 58.9 ms (P = NS), respectively. In Group II, in one patient with dual AV nodal physiology but no clinical tachycardia, the PRTCL induced nonsustained (12 beats) AVNRT. Additionally, in this group, both PRTCL and STD methods induced atrial tachycardia in two patients and orthodromic AV re-entrant tachycardia in one patient.

CONCLUSION

Decremental ramp atrial extrastimuli pacing PRTCL demonstrates a superior response for induction of typical AVNRT as compared to STD techniques. Because of easy and reliable induction of AVNRT and echo beats by the PRTCL, we recommend it as a method to increase the likelihood of induction of AVNRT. For induction of other SVTs, the PRTCL and the STD methods are comparable.

Electroanatomical Mapping and Radiofrequency Catheter Ablation of Atrial Tachycardia Originating from the Recipient Heart with Recipient-to-Donor Atrio-Atrial Conduction After Orthotopic Heart Transplantation

Atrial tachycardias resulting from recipient-to-donor atrio-atrial conduction after orthotopic heart transplantation are difficult to treat. We present two patients in whom atrial tachycardia originating in the recipient heart were successfully treated by radiofrequency ablation guided by electroanatomical CARTO mapping system. These cases illustrate that such atrial tachycardia are curable by radiofrequency ablation. Electroanatomical CARTO mapping is useful in identifying the site of origin of the tachycardia and the atrio-atrial conduction sites.

Usefulness of pindolol for treatment of neurocardiogenic syncope

This study evaluated the efficacy of pindolol, a noncardioselective beta blocker with intrinsic sympathetic activity, on neurocardiogenic syncope using a head-up tilt-table test in 66 patients. Pindolol was equally effective in men and women and the 2 age groups (>60 and <60 years) of the study cohort. The earliest benefit was seen </=3 days after initiating treatment. Side effects were better tolerated in younger patients (age <60 years).

Pacemaker and defibrillator lead extraction

PURPOSE OF REVIEW

Continued growth in the elderly population and expanding indications have resulted in a progressive increase in the number of implants of pacemakers and defibrillators. Concomitant with these expanding numbers, more leads require removal, due especially to mechanical dysfunction, the need to upgrade to more complex devices, or local or systemic infection. Further, leads have become more complex, particularly for defibrillator systems, resulting in the development of powered extraction sheaths to expedite their removal. For these reasons, it is important to understand the expanding indications, procedural aspects, and limitations of arrhythmia device extraction.

RECENT FINDINGS

Expanded indications for lead extraction include upgrade to more complex systems, particularly pacemaker to defibrillator or biventricular device, extraction through occluded vasculature to produce a conduit for reimplantation, more frequent removal due to vascular overload with multiple leads, and a finite frequency of infection, occurring particularly with device replacement or revision. Powered sheaths now include laser and electrocautery systems, both improving the ease of lead explantation.

SUMMARY

Complication rates remain low but constant with extraction of larger numbers of leads using new technologies. Expansion of the use of biventricular systems, with implantation of coronary sinus electrodes, will continue to challenge lead extraction in terms of technology and safety. Design of leads that are easier to remove remains of paramount importance.

Dual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator: the Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial

CONTEXT

Implantable cardioverter defibrillator (ICD) therapy with backup ventricular pacing increases survival in patients with life-threatening ventricular arrhythmias. Most currently implanted ICD devices provide dual-chamber pacing therapy. The most common comorbid cause for mortality in this population is congestive heart failure.

OBJECTIVE

To determine the efficacy of dual-chamber pacing compared with backup ventricular pacing in patients with standard indications for ICD implantation but without indications for antibradycardia pacing.

DESIGN

The Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial, a single-blind, parallel-group, randomized clinical trial.

SETTING AND PARTICIPANTS

A total of 506 patients with indications for ICD therapy were enrolled between October 2000 and September 2002 at 37 US centers. All patients had a left ventricular ejection fraction (LVEF) of 40% or less, no indication for antibradycardia pacemaker therapy, and no persistent atrial arrhythmias.

INTERVENTIONS

All patients had an ICD with dual-chamber, rate-responsive pacing capability implanted. Patients were randomly assigned to have the ICDs programmed to ventricular backup pacing at 40/min (VVI-40; n = 256) or dual-chamber rate-responsive pacing at 70/min (DDDR-70; n = 250). Maximal tolerated medical therapy for left ventricular dysfunction, including angiotensin-converting enzyme inhibitors and beta-blockers, was prescribed to all patients.

MAIN OUTCOME MEASURE

Composite end point of time to death or first hospitalization for congestive heart failure.

RESULTS

One-year survival free of the composite end point was 83.9% for patients treated with VVI-40 compared with 73.3% for patients treated with DDDR-70 (relative hazard, 1.61; 95% confidence interval [CI], 1.06-2.44). The components of the composite end point, mortality of 6.5% for VVI-40 vs 10.1% for DDDR-70 (relative hazard, 1.61; 95% CI, 0.84-3.09) and hospitalization for congestive heart failure of 13.3% for VVI-40 vs 22.6% for DDDR-70 (relative hazard, 1.54; 95% CI, 0.97-2.46), also trended in favor of VVI-40 programming.

CONCLUSION

For patients with standard indications for ICD therapy, no indication for cardiac pacing, and an LVEF of 40% or less, dual-chamber pacing offers no clinical advantage over ventricular backup pacing and may be detrimental by increasing the combined end point of death or hospitalization for heart failure.

Prolonged sustained ventricular fibrillation without loss of consciousness in patients supported by a left ventricular assist device

Patients with cardiomyopathy of either ischemic or nonischemic origin are at increased risk for malignant ventricular arrhythmias. Normally sustained ventricular fibrillation (VF) leads to death very rapidly. We report two patients who remained in sustained VF, supported by a left ventricular assist device, for a prolonged period of time. Perfusion pressure through the device was sufficient to allow the patients to remain awake and responsive for several hours while in VF. The cases represent two of the longest reported episodes of sustained VF recorded in awake patients implanted with such devices.

Effect of surgical revascularization in patients with coronary artery disease and ventricular tachycardia or fibrillation in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Registry

BACKGROUND

Patients who undergo resuscitation from near-fatal ventricular arrhythmias often have significant coronary artery disease, and revascularization has been shown to reduce myocardial ischemia and cardiac arrest episodes in this patient population. The magnitude of benefit attributed to revascularization has varied by study, and the use of adjunct implantable cardioverter defibrillator (ICD) therapy has not been well-characterized.

METHODS AND RESULTS

The Antiarrhythmics Versus Implantable Defibrillators (AVID) registry included 3117 patients with life-threatening ventricular arrhythmias, of whom 2321 (77%) had documented coronary artery disease and 281 (17%) underwent a coronary artery bypass grafting revascularization procedure after the index event. Patients who underwent a revascularization procedure were younger, had a lower incidence rate of prior myocardial infarction and ventricular arrhythmia, had a higher left ventricular ejection fraction, had less congestive heart failure, and were more likely to have had ventricular fibrillation as the presenting arrhythmia. Patients who underwent revascularization had a better survival rate than did those who did not undergo such a procedure after the index event, and adjustment for differing baseline patient covariates did not alter the relative survival rate benefit. Further, ICD implantation offered a similar survival rate advantage to those patients in the AVID registry with coronary artery disease independent of revascularization.

CONCLUSION

Coronary revascularization in the AVID registry patients with coronary artery disease effected a survival rate benefit that was not attributable to differences in baseline patient characteristics. The benefit of ICD on patient survival rate was not attenuated by a revascularization procedure.

Proarrhythmic effects of adenosine: one decade of clinical data

In 1989, adenosine was introduced into the American clinical setting as an antiarrhythmic drug for the acute management of reentrant supraventricular tachycardia involving the atrioventricular node. During this decade of use, evidence for proarrhythmic effects of the drug have been documented. In addition to the mostly benign transient episodes of atrial fibrillation, several cases of life-threatening ventricular arrhythmias induced by adenosine have been reported. This article summarizes the proarrhythmic effects of adenosine as they were reported in the literature as well as data from the manufacturer files. The causes of these adverse effects of adenosine are analyzed, and factors to be considered before using the drug are discussed.

Quality of life in the antiarrhythmics versus implantable defibrillators trial: impact of therapy and influence of adverse symptoms and defibrillator shocks

BACKGROUND

Implantable cardioverter defibrillator (ICD) use reduces mortality in patients with serious ventricular arrhythmias compared with antiarrhythmic drug (AAD) use. However, the relative impact of these therapies on self-perceived quality of life (QoL) is unknown.

METHODS AND RESULTS

Three self-administered instruments were used to measure generic and disease-specific QoL in Antiarrhythmics Versus Implantable Defibrillators trial participants. Generalized linear models were used to assess the relationships between self-perceived QoL and treatment (AAD versus ICD) and adverse symptoms and ICD shocks. To minimize the impact of missing data, only patients surviving 1 year were included in the primary analyses. Baseline characteristics among QoL participants (n=905) and nonparticipants (n=111) were similar, but participants who survived 1 year (n=800) were healthier at baseline than nonsurvivors (n=105). Of the 800 patients in the primary analysis, characteristics of those randomized to AAD (n=384) versus ICD (n=416) were similar. Overall, ICD and AAD use were associated with similar alterations in QoL. The development of sporadic shocks and adverse symptoms were each associated with reduced physical functioning and mental well-being and increased concerns among ICD recipients, whereas development of adverse symptoms was associated with reduced physical functioning and increased concerns among AAD recipients.

CONCLUSIONS

ICD and AAD therapy are associated with similar alterations in self-perceived QoL over 1-year follow-up. Adverse symptoms were associated with reduced self-perceived QoL in both groups, and sporadic shocks were associated with reduced QoL in ICD recipients.

Ventricular assist device support for management of sustained ventricular arrhythmias

We describe herein the cases of 2 patients who had ventricular arrhythmias. In one, a short-term biventricular assist device, the ABIOMED BVS 5000, was placed because the patient had sustained ventricular tachycardia and could not be weaned from cardiopulmonary bypass. Excellent hemodynamic support was maintained for several days while the antiarrhythmic therapy was maximized. Sinus rhythm was restored, and the patient was successfully weaned from the ventricular assist device. However, the substrate for the arrhythmia persisted, and a recurrence, 1 week later, resulted in the patient's death. In the 2nd patient, the use of an implantable left ventricular assist device was successful in temporarily alleviating the ventricular tachycardia associated with ischemic cardiomyopathy. However, after 2 days of device assistance, the patient experienced a recurrence of the tachycardia, which degenerated into ventricular fibrillation with a marked deterioration in the patient's hemodynamics. The arrhythmia persisted despite multiple attempts at external cardioversion, and internal cardioversion and placement of an automatic implantable cardioverter-defibrillator were necessary. This treatment, along with repeated boluses of amiodarone, led to successful suppression of the arrhythmias, and the patient eventually underwent transplantation. The mechanical hemodynamic support of the circulation by ventricular assist devices was effective in supporting these 2 patients who had sustained ventricular arrhythmias.

Effect of different location of atrial lead position on nearfield and farfield electrograms in dual chamber pacemaker-defibrillators

The normal functioning of dual chamber pacemaker-cardioverter defibrillator (AV pacer/ICD) may be affected by oversensing of the farfield R wave (FFRW) by the atrial channel. This study aimed to investigate whether placement of the AV pacer/ICD's atrial lead at a lateral (LAT) wall location compared to a medial (MED) location i.e. the appendage of the right atrium, would reduce the amplitude of FFRWs but not the nearfield atrial electrograms (AEGMs) during sinus rhythm (SR) and ventricular fibrillation (VF). In 17 patients, real time electrograms were recorded during SR and induced VF through the atrial lead initially at the MED and subsequently at the LAT location. In 10 patients the electrograms in SR were also recorded on a computerized data acquisition and recording system at different band-pass filter settings. Although FFRWs were recorded both at MED and LAT locations, they were much smaller, 3.5+/-4.1mm during SR and 1.7+/-2.2mm during VF at the LAT location. At 30-500Hz band-pass filter, lower amplitudes of FFRWs 0.14+/-0.09 mV were recorded at the LAT location. The V/A ratios of the amplitudes of FFRWs and AEGMs were smaller at the LAT location during SR and VF. The nearfield AEGMs were of similar amplitudes at the MED and LAT locations. These data indicate that lower amplitudes of FFRWs are recorded by placement of the atrial lead at the lateral wall of the right atrium. Oversensing of FFRWs may be prevented to improve functioning of the AV pacer-ICD.

Early detection of acute allograft rejection by linear and nonlinear analysis of heart rate variability

OBJECTIVE

The first months after orthotopic heart transplantation are associated with the highest risk of acute allograft rejection. This study explores the utility and reliability of linear and novel nonlinear metrics of heart rate variability as predictors of graft rejection. The underlying hypothesis is that the transplanted heart, in response to inflammatory mediators, alters the dynamic properties of its rhythm-generating system.

METHODS

In a cross-sectional study of 45 patients who had undergone heart transplantation, spanning a period of 4 months after the operation, heart rate variability was examined by time- and frequency-domain analysis. The nonlinear features of heart rate variability were studied by computing a pointwise correlation dimension of R-R interval time series. The results of heart rate variability analysis were compared with those of endomyocardial surveillance biopsy studies using the International Society for Heart and Lung Transplantation scoring system.

RESULTS

Duration of heart transplantation itself exhibited a significant (P<.05) association with the onset of rejection. Specific predictors of acute rejection based on heart rate variability were identified, including shortening of the R-R interval (from 700 +/- 68 to 648 +/- 72 ms), an increase in the ratio of low-frequency (0.04-0.15 Hz) to high-frequency (0.15-0.40 Hz) spectral power (from 0.3 +/- 0.2 to 0.6 +/- 0.4), and a decrease in pointwise correlation dimension values (from 1.7 +/- 0.7 to 0.9 +/- 0.3 units). Multivariable logistic regression analysis (R (2) = 0.4) revealed that the only significant independent risk predictors were pointwise correlation dimension (odds ratio, 2.2 per 0.1 unit) and duration of heart transplantation (odds ratio, 1.7 per week).

CONCLUSION

Nonlinear measures of heart rate variability provide noninvasive means for identifying patients undergoing cardiac transplantation with acute rejection, thereby enabling the assessment of the time-dependent adaptive response of the donor heart to its host.

Feasibility, safety, and determinants of extraction time of percutaneous extraction of endocardial implantable cardioverter defibrillator leads by intravascular countertraction method

Previous studies of the removal of implantable cardioverter defibrillator (ICD) leads have been restricted to case reports or small series. In this report, we describe our experience in ICD lead extraction by intravascular countertraction method using Cook's extraction kit. A total of 47 high-voltage (HV) leads, 3 rate sensing (S) leads, and 2 subcutaneous arrays were removed from 42 patients (33 men, 9 women; mean age 59 years [range 14 to 81]). One HV superior vena cava (SVC) lead and 11 HV right ventricular (RV) leads were explanted by manual traction only and defined in the "lead removal" category. One S lead was removed using a femoral venous approach. The remaining 37 leads were explanted by SVC approach using extraction sheaths and defined in the "lead extraction" category. Twenty leads were extracted for "infectious" (group A) and 17 leads for "noninfectious" (group B) etiologies for which extraction times of 27.0+/-18.0 and 27.0+/-15.0 minutes (mean+/-SD), respectively, were not different. Although extraction time, 34.0+/-11.0 minutes, for leads implanted for >48 months was longer than 23.0+/-16.0, 28.0+/-18.0, and 24.0+/-14.0 minutes, for leads with implant durations of 12, 24, and 48 months, respectively, such differences were not statistically significant. The extraction time, however, was directly related to the degree of fibrosis around the lead, 39.0+/-15.0 minutes for leads with severe fibrosis compared with 13.0+/-6.0 minutes for the leads with mild fibrosis (p<0.001). Patient's age, sex, or history of coronary artery bypass graft surgery did not significantly affect extraction time. All except the initial 2 lead extractions were performed in the electrophysiology laboratory. No mortality or serious complications associated with the procedure using these methods were observed.

Efficacy and safety of catheter ablation in octogenarians

OBJECTIVES

To determine whether catheter ablation is safe and effective in patients over the age of 80.

BACKGROUND

There is a tendency to withhold invasive therapy in the elderly until it has been proven safe and effective.

METHODS

Over a two-year period from February 1, 1996 to February 1, 1998, 695 consecutive patients underwent 744 catheter ablation procedures of supraventricular and ventricular arrhythmias. These patients were divided into three groups based on age: > or =80 years, 60 to 79 years and <60 years. Acute ablation success, using standard criteria and complication rates for these three groups were determined.

RESULTS

There were 37 patients > or =80 years, 275 patients 60 to 79 years and 383 patients <60 years old. The overall acute ablation success rate for the entire group was 95% with no difference in rates among the three groups (97%, > or =80 years; 94%, 60-79 years; 95%, <60 years). The percentage of patients undergoing His bundle ablation was greatest in the > or =80-year-old group (43% vs. 19% vs. 2%, p < 0.01), and the percentage of patients undergoing accessory pathway ablation was greatest in the <60-year-old patients (0% vs. 4% vs. 25%, p < 0.01). The overall complication rate for the entire group was 2.6%, and there was only one major/life-threatening complication. There was no difference in complication rates among the groups (0%, > or =80 years; 2.2%, 60 to 79 years; 3.1%, <60 years). Based on the sample size, the 95% confidence interval is 0% to 7.8% for an adverse event in the octogenarian.

CONCLUSIONS

Catheter ablative therapy for the arrhythmias attempted in the very elderly appears to be effective with low risk. Ablation results appear to be comparable with those noted in younger patients.

Prevalence and characteristics of escape rhythms after radiofrequency ablation of the atrioventricular junction: results from the registry for AV junction ablation and pacing in atrial fibrillation. Ablate and Pace Trial Investigators

BACKGROUND

Radiofrequency ablation of the atrioventricular junction is a well-established procedure for the management of atrial fibrillation refractory to medical therapy. However, there are few data available on the prevalence and characteristics of the escape rhythms that are present after the procedure.

METHODS

The Ablate and Pace Trial was a prospective, multicenter registry of atrioventricular junction ablation and pacing in atrial fibrillation. Ablation of the atrioventricular junction was accomplished with radiofrequency energy with standard techniques. Before discharge from the hospital, patients underwent a systematic analysis of the rate and morphologic features of the escape rhythm, if any, that was present when the pacing rate was gradually decreased.

RESULTS

There were 156 patients from 16 centers who underwent attempted radiofrequency ablation of the atrioventricular junction. The procedure was successful in 155 (99%) of 156 patients. An escape rhythm was present in 104 patients (67%) after radiofrequency ablation. The escape rate ranged from 11 to 65 beats/min (mean 39 +/- 10 beats/min). Only 49 patients (31%) had an escape rate >/=40 beats/min. Of the 104 patients with an escape rhythm, 53 patients (51%) had a QRS that was unchanged from baseline. There was no correlation between the number of radiofrequency applications and the presence of an escape rhythm.

CONCLUSION

The majority of patients who undergo radiofrequency catheter ablation of the atrioventricular junction are pacemaker dependent after the procedure, as defined by lack of an escape rhythm or the presence of an escape rhythm that is <40 beats/min.

Radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia after orthotopic heart transplantation

Patients with orthotopic heart transplantation may develop a variety of arrhythmias. Successful radiofrequency catheter ablation for tachyarrhythmias from manifest and concealed accessory bypass tracts in transplant patients has been previously reported. We present a patient with orthotopic heart transplantation who developed typical atrioventricular nodal tachycardia, which was successfully treated by radiofrequency catheter ablation.

Intravascular extraction of problematic or infected permanent pacemaker leads: 1994-1996. U.S. Extraction Database, MED Institute

Of the 400,000-500,000 permanent pacemaker leads implanted worldwide each year, around 10% may eventually fail or become infected, becoming potential candidates for removal. Intravascular techniques for removing problematic or infected leads evolved over a 5-year period (1989-1993). This article analyzes results from January 1994 through April 1996, a period during which techniques were fairly stable. Extraction of 3,540 leads from 2,338 patients was attempted at 226 centers. Indications were: infection (27%), nonfunctional or incompatible leads (25%), Accufix or Encore leads (46%), or other causes (2%). Patients were 64+/-17 years of age (range 5-96); 59% were men, 41% women. Leads were implanted 47+/-41 months (maximum 26 years), in the atrium (53%), ventricle (46%), or SVC (1%). Extraction was attempted via the implant vein using locking stylets and dilator sheaths, and/or transfemorally using snares, retrieval baskets, and sheaths. Complete removal was achieved for 93% of leads, partial for 5%, and 2% were not removed. Risk of incomplete or failed extraction increased with implant duration (P<0.0001), less experienced physicians (P<0.0001), ventricular leads (P<0.005), noninfected patients (P<0.0005), and younger patients (P<0.0001). Major complications were reported for 1.4% of patients (<1% at centers with >300 cases), minor for 1.7%. Risk of complications increased with number of leads removed (P<0.005) and with less experienced physicians (P<0.005); risk of major complications was higher for women (P<0.01). Given physician experience, appropriate precautions, and appropriate patient selection, contemporary lead removal techniques allow success with low complication rates.

Escape capture bigeminy: a manifestation of sinoatrial conduction block

Sinoatrial block (SAB) is often difficult to identify in the presence of bradycardic rhythms. This study demonstrates several manifestations of so-called escape capture bigeminy in 14 patients. Although periods of 1:1 sinoatrial conduction can aid in the analysis of SAB, the electrocardiographic pattern of bigeminal rhythm may be the only electrocardiographic clue of SAB. In one case, both sinoatrial entrance and exit block were identified. In eight instances, digitalis or digitalis plus a beta or calcium blocking agent could be partially implicated as the cause of SAB. In 6 of 14 patients, a permanent pacemaker was required to correct the bradycardia, in spite of discontinuation of aggravating antiarrhythmic agents or electrolyte derangement.

Extraction of pacemaker and implantable cardioverter defibrillator leads

The common reasons for removal of pacing and defibrillator leads are infection, malfunction, or design defects such as fracture of J wires in Teletronics Accufix leads (Telectronics Pacing, Englewood, CO), which impose considerable risk for cardiac morbidity and mortality. Chronically implanted leads are fixed to the myocardium by fibrous tissue. Fibrous scar tissue may also encase the lead along its course. Furthermore, fragility of the lead and its tendency to break when extraction force is applied to overcome resistance imparted by the scar tissue add to the challenge of lead extraction. Thus, the extraction of chronically implanted leads is an important issue. Until a few years ago, the only methods available for the removal of chronically implanted leads were traction on the proximal segment of the lead and cardiac surgery. New techniques were developed to extract the leads by a transvenous approach using locking stylets, sheaths, snares, and retrieval baskets. Lead extraction using intravascular countertraction methods has since evolved as a specialty of its own. Progress has also been made in developing other system, such as Excimer laser energy for lead extraction. In this article, we discuss principles, techniques, and experience with these methods of extraction of chronic pacemaker and defibrillator leads.

Extraction and replacement of permanent pacemaker leads through occluded vessels: use of extraction sheaths as conduits--balloon venoplasty as an adjunct

Patients (pts) may present for lead extraction with symptomatic or asymptomatic subclavian vein or superior vena cava thrombosis. Replacement of permanent pacemaker leads (PPLs) in these pts may be difficult and may require accessing a new site. We examined the utility of replacing PPLs through completely occluded vessels using extraction sheaths as conduits through the total occlusion. Over six years, a total of 210 atrial and/or ventricular PPLs were extracted from 137 pts. Two pts presented with angiographically documented thrombotic occlusion of the subclavian vein. One additional pt. who had presented with a superior vena cava (SVC) syndrome, had a totally occluded innominate vein and SVC occlusion. Balloon venoplasty was used as an adjunct to dilate the SVC. In all pts, after PPLs were removed via a subclavian extraction sheath through the occluded vessel, the retained sheath was used to place a guide wire, then a peel away dilating sheath, to insert new PPLs, in each case on the side of total venous occlusion. Seven PPLs and two lead fragments were extracted, and five new PPLs replaced, ipsilateral to the venous occlusion. These data show that extraction of PPLs through thrombosed veins may be performed successfully and may not require replacing the leads through a new site. This technique spares the pt the need to access the opposite subclavian vein, and it avoids an excessive number of PPLs in the subclavian vein and SVC. The procedure illustrates an efficient means to reintroduce new PPLs with the potential to reduce associated morbidity, since repeat puncture of the subclavian vein is not required. Safety of the procedure as a whole must be considered with regard to the known risks of lead extraction, some complications of which may be substantial using current techniques.

Adenosine in the mammalian heart: nothing to get excited about

Until quite recently, the cardiodepressant actions of adenosine were widely accepted. A nucleoside that produces negative chronotropic and ionotropic effects, adenosine, has been used clinically as the drug of choice for terminating supraventricular (atrioventricular node) tachycardia and is likely to play an important part in regulating arrhythmogenic activity as an endogenous antiarrhythmic metabolite. Despite this, recent experimental data, particularly resulting from in vitro studies using animal models, have shown a paradoxical excitable action of adenosine in the heart. In this article, Amir Pelleg and Steven Kutalek present the reasons why they continue to believe that any excitatory actions of adenosine in the heart are clinically irrelevant.

Management of distal electrode detachment during lead extraction

A telectronics 330-801 atrial active fixation lead with multiple J retention wire fractures was extracted. Separation of the distal electrode occurred due to antecedent inner conductor fracture between the endocardial electrode pair. Techniques for removal of the free distal electrode are described, including use of biopsy forceps and a snare.

The automated implantable cardiac defibrillator. Prophylaxis in cardiac sarcoidosis

A patient with cardiac sarcoidosis proved by biopsy specimen and no history of sudden death or clinical sustained ventricular tachycardia prophylactically received an implantable cardioverter defibrillator (ICD) that later reversed an episode of near syncope. The patient was supported with the ICD until heart transplantation. The physiology and treatment of arrhythmias associated with cardiac sarcoidosis is described. Consideration for use of the ICD in asymptomatic patients and as bridge therapy until heart transplantation is discussed.

Inappropriate discharge by an implantable cardioverter defibrillator: recognition of myopotential sensing using telemetered intracardiac electrograms

Inappropriate therapy from implantable anti-tachyarrhythmia devices is a common problem with a variety of etiologies. The verification of arrhythmias or other sensed events that precipitate defibrillating shocks is difficult with first- and second-generation devices due to the absence of sufficient data storage and the inability to examine stored and real-time intracardiac electrograms. In addition, the absence of premonitory symptoms is an unreliable marker for the appropriateness of defibrillator shocks. The incorporation of improved data storage and the ability to inspect intracardiac electrograms in newer devices have greatly increased the ability to diagnose abnormal device behavior as shown in the following case report. Inappropriate implantable cardioverter defibrillator discharge due to myopotential sensing is described. The diagnosis was facilitated by telemetered intracardiac electrograms.