Safety of pacemaker implantation in patients with transvenous (nonthoracotomy) implantable cardioverter defibrillators

Anesthetic Implications for Patients With Implantable Cardioverter Defibrillators

Implantable cardioverter defibrillators have become one of the preferred methods for treating many life- threatening ventricular arrhythmias. Many tens of thou sands of these devices have been implanted and this, together with the ease of worldwide travel, has made it more likely that anesthesiologists everywhere may come into contact with these patients either for elective or emergency surgery. These patients present unique anesthetic challenges because of the combination of the device and severe underlying cardiac disease. This article presents an overview of the implantable defibril lator as it affects the anesthesiologist, including device function, device assessment, electromagnetic interfer ence, and perioperative management.

Should all implantable cardioverter defibrillators for ventricular arrhythmias be dual-chamber devices?

The advantages of a dual-chamber implantable cardioverter defibrillator (ICD) over a single-chamber ICD include physiologic pacing capability, atrial electrogram storage, enhanced arrhythmia discrimination algorithms, and a potential to treat atrial arrhythmia by pacing or defibrillation. Current evidence supports the supposition that dual-chamber ICDs are definitely indicated in patients who have a concomitant indication for physiologic pacing, such as bradycardia or bradycardia-dependent ventricular tachyarrhythmias. Refined dual-chamber arrhythmia discrimination algorithms and enhanced atrial therapies are probably required for patients with frequent supraventricular arrhythmias. Furthermore, in patients with systolic heart failure, low ejection fraction, and intraventricular conduction delay, triple-chamber ICDs with biventricular pacing may improve their functional status and prevent sudden arrhythmic death. Careful patient selection is required to optimize the cost-effectiveness of these sophisticated technologies.

A prospective randomized-controlled trial of ventricular fibrillation detection time in a DDDR ventricular defibrillator. Ventak AV II DR Study Investigators

Implantable cardioverter defibrillators (ICDs) with dual chamber and dual chamber rate responsive pacing may offer hemodynamic advantages for some ICD patients. Separate ICDs and DDDR pacemakers can result in device to device interactions, inappropriate shocks, and underdetection of ventricular fibrillation (VF). The objectives of this study were to compare the VF detection times between the Ventak AV II DR and the Ventak AV during high rate DDDR and DDD pacing and to test the safety of dynamic ventricular refractory period shortening. Patients receiving an ICD were randomized in a paired comparison to pacing at 150 beats/min (DDD pacing) or 175 beats/min (DDDR pacing) during ICD threshold testing to create a "worst case scenario" for VF detection. The VF detection rate was set to 180 beats/min, and VF was induced during high rate pacing with alternating current. The device was then allowed to detect and treat VF. The induction was repeated for each patient at each programmed setting so that all patients were tested at both programmed settings. Paired analysis was performed. Patient characteristics were a mean age of 69 +/- 11 years, 78% were men, coronary artery disease was present in 85%, and a mean left ventricular ejection fraction of 0.34 +/- 0.11. Fifty-two episodes of VF were induced in 26 patients. Despite the high pacing rate, all VF episodes were appropriately detected. The mean VF detection time was 2.4 +/- 1.0 seconds during DDD pacing and 2.9 +/- 1.9 seconds during DDDR pacing (P = NS). DDD and DDDR programming resulted in appropriate detection of all episodes of VF with similar detection times despite the "worst case scenario" tested. Delays in detection may be seen with long programmed ventricular refractory periods which shorten the VF sensing window and may be avoided with dynamic ventricular refractory period shortening.

ICD therapy in the new millennium

Remarkable progress has been made in the 15 years since ICD therapy was approved for human use. The early "shock boxes" had almost no diagnostic capabilities and required thoracotomy for epicardial patch implantation with typical duration of hospitalization of about a week. Pulse-generator longevity was less than 2 years. Modern devices provide detailed information about the morphology and rate of electrocardiographic signals before, during, and after arrhythmia therapy. The down-sizing of pulse generators and improvements in lead design and shock waveforms allow the simplicity of defibrillator implantation to approach that of pacemakers, with defibrillation thresholds comparable with those initially observed with epicardial patches. Despite the marked reduction in size and increase in diagnostic capabilities, device longevity is now longer than 6 years. Routine outpatient ICD implantation is presently feasible and will increase in frequency if ongoing primary prevention trials prove beneficial. Further advances in lead technology and arrhythmia discrimination should increase the efficacy and reliability of therapy. Finally, devices have the capabilities to treat multiple problems in addition to life-threatening ventricular arrhythmias including atrial arrhythmias and congestive heart failure.

The first year experience with the dual chamber ICD

In July 1997, a dual chamber pacemaker combined with a tiered therapy implantable cardioverter defibrillator (ICD) first became available in the United States. We report the first-year experience of one center in the United States with this dual chamber ICD. Of a total of 174 ICDs, 95 (55%) were dual chamber devices and 79 (45%) were single chamber. New dual chamber ICD insertions averaged 57.4 +/- 8.9 minutes, though there was a learning curve as the last 30 implants averaged 45.1 +/- 6.1 minutes with a negative slope to the regression line of procedure duration (-0.52, P < 0.05). New single chamber ICD implants were 18.5 minutes quicker (38.9 +/- 7.2 minutes). The most challenging implants were dual chamber upgrades (mean procedure duration 64.9 +/- 15.8 minutes), especially if there was a previously implanted pacemaker and ICD at separate sites. Indications for a new dual chamber device were grouped into classic pacemaker indications (52.5%), which comprised the Class I ACC/AHA guidelines, ICD-specific indications (24.6%), and other (23.0%). In the 34 patients undergoing dual chamber upgrade, the classic and ICD-specific groups were equal (47.0% each). Complications were rare (2.8%), though 3 (8.8%) of 34 undergoing a dual chamber upgrade developed late infections requiring explantation. In its first year, the dual chamber ICD has become a common device at our institution comprising 55% of new implants. As experience grows, we anticipate similar usage at most institutions.

A stepwise testing protocol for modern implantable cardioverter-defibrillator systems to prevent pacemaker-implantable cardioverter-defibrillator interactions

Current use of newer implantable cardioverter-defibrillators (ICDs) has changed the spectrum of pacemaker-ICD interactions and provided new tools for testing and understanding those interactions. Testing for pacemaker-ICD interactions was performed in 31 procedures involving 22 patients. The protocol included: (1) evaluation of pacemaker stimulus artifact amplitude and its ratio to that of the evoked ventricular electrogram, (2) testing for inhibition of ventricular fibrillation (VF) detection by the ICD during asynchronous pacing at maximum output, (3) evaluation by pacemaker event marker recordings of pacemaker sensing behavior while programmed to nonasynchronous mode during ventricular tachycardia (VT) or VF, and (4) evaluation of postshock interactions. Inhibition of detection of VT/VF was found in 6 of 22 patients (27.2%). Large stimulus artifact amplitude (>2 mV) or stimulus artifact:evoked QRS ratio > 1/3 had a positive predictive accuracy of 18% and 14.4%, respectively, and a negative predictive accuracy of 100% and 92.3%, respectively, for clinically significant interaction. Asynchronous pacing occurred in 16 of 31 procedures (51.6%), and was due to underdetection by the pacemaker in 4 of 16 (25%) and noise reversion in 12 of 16 (75%). Postshock phenomena occurred in 6 cases, 3 of which were clinically significant. Overall, 11 of 22 patients (50%) had clinically significant interactions discovered by this protocol, which led to system revisions in 6 and to pacemaker output reprogramming in 5. Thus, pacemaker-ICD interactions are frequently detected using a thorough and systematic protocol. Most cases can be managed by system revision or pacemaker reprogramming.

Combined use of a true-bipolar sensing implantable cardioverter defibrillator in a patient having a prior implantable spinal cord stimulator for intractable pain

Reported is a case involving a patient with a previously implanted spinal cord stimulator (SCS) who presented for an implantable cardioverter defibrillator (ICD). The SCS device was located in the left lower abdominal quadrant with a stimulation electrode array placed on the dorsal aspect of the spinal cord at the T-11 thoracic level. Interaction testing demonstrated that the biopolar sensing transvenous ICD system (Medtronic 7221 Cx PCD) did not detect the stimulator's output at burst rates ranging from 20-130 pulses/s, even with the ICD set to its maximum sensitivity of 0.15 m V and the stimulator programmed to the highest patient tolerated output combinations of 5 V, 0.45 ms in the bipolar configuration and 3 V, 0.45 ms in the unipolar (i.e., case-electrode) configuration.

Indications for implantation of a dual-chamber pacemaker combined with an implantable cardioverter-defibrillator

Of 122 patients with single-chamber implantable cardioverter-defibrillators (ICDs) reviewed retrospectively, 35 had traditional indications, 14 had other indications, and 18 had ICD-specific indications for dual-chamber pacing therapy. Thus, 67 patients (55%) were potential candidates for dual-chamber pacing, which has only recently become available combined with ICD therapy.

Importance of pacemaker noise reversion as a potential mechanism of pacemaker-ICD interactions

Numerous types of interactions between pacemakers and implantable cardioverter defibrillators (ICDs) have been described. Pacemaker outputs preventing appropriate detection of ventricular tachycardia or ventricular fibrillation by the ICD is one of the more serious. Asynchronous pacemaker activity during ventricular arrhythmias may be caused by either nonsensing of the arrhythmia or by noise reversion, which is an algorithm that causes the pacemaker to switch to asynchronous pacing when repetitive sensing at a high rate occurs. We analyzed the mechanisms underlying asynchronous pacemaker activity in ventricular arrhythmias using pacemaker telemetry during the arrhythmia. Thirty-nine induced arrhythmias from 26 different procedures in 19 patients with both pacemakers and ICDs were analyzed. Of the 39 arrhythmias, asynchronous pacemaker activity occurred in 16. The underlying mechanism was nonsensing in 4 episodes and noise reversion in 12 episodes. Clinically significant interference with detection arose on three occasions. Conditions favoring the occurrence of noise reversion include specific pacemaker models, arrhythmia cycle lengths in the range causing noise reversion of the individual pacemaker model, long noise sampling periods, and VVI pacing mode. Noise reversion can be diagnosed by telemetering the pacemaker marker channel during ventricular arrhythmias as a part of routine pacemaker-ICD interaction evaluation. It can be prevented or minimized by programming short ventricular refractory periods or using pacemakers with short retriggerable refractory periods.

Permanent pacing from the coronary sinus in a patient with an implantable defibrillator

A woman with an ICD underwent permanent pacemaker implantation for bradycardia-tachycardia syndrome. Despite multiple right atrial positions, oversensing secondary to "double counting" was always noted. A coronary sinus pacing catheter was inserted and left atrial pacing was accomplished with acceptable pacing and sensing characteristics. The patient has since done well without further shocks.

Combined use of non-thoracotomy cardioverter defibrillators and endocardial pacemakers

OBJECTIVE

To study the potential interactions in patients with endocardial permanent pacemakers and non-thoracotomy implantable cardioverter defibrillator (ICD) systems.

DESIGN

Case series and cohort study.

SETTING

Tertiary referral centre.

PATIENTS

Fifteen consecutive patients with both endocardial pacemakers (12 dual chamber and three single chamber) and non-thoracotomy ICD systems.

MAIN OUTCOME MEASURES

Detection inhibition of induced ventricular fibrillation; double counting; and pacemaker function after shocks. In the evaluation of detection inhibition, 124 VF inductions were analysed for detection duration compared with induced VF episodes in controls with an ICD but without a pacemaker.

RESULTS

Two patients (13%) showed detection inhibition of VF and required pacemaker system change at the time of the ICD implant. With the final lead position, despite frequent pacemaker undersensing of VF, ICD detection of VF was not inhibited during any induction, and neither initial detection nor redetection times for VF were different from controls. Double/triple counting of pacemaker artefact and evoked electrogram was noted in three patients (20%). In two, this was remedied during the implantation procedure, and in the other it was abolished when amiodarone treatment was discontinued. Pacemaker function was affected by ICD discharges in two patients, one who showed postshock atrial undersensing and loss of capture, and another whose pacemaker reverted to VVI mode.

CONCLUSIONS

When careful testing is performed at implantation to detect and remedy device interactions, non-thoracotomy ICD treatment and endocardial pacemakers can be used safely in combination.

ICD-antiarrhythmic drug and ICD-pacemaker interactions

Antiarrhythmic drugs and separate bradycardia pacing systems are prescribed commonly in patients with implantable cardioverter defibrillators (ICDs). Adverse effects of antiarrhythmic drugs on ICD function and adverse interactions between ICDs and pacemakers have been documented. The effect of antiarrhythmic drugs on the defibrillation threshold (DFT) in patients has not been well assessed. Most studies have been performed in animal models in which cardiac function was normal and drug doses were supraphysiologic. In addition, most studies have utilized monophasic defibrillation shock waveforms and epicardial lead systems. Despite the lack of clinical data applicable to current defibrillation systems, it appears that chronic amiodarone administration causes a significant DFT increase. In addition, antiarrhythmic drugs can influence antitachycardia pacing and tachycardia sensing. Defibrillation shocks can cause transient failure of pacemaker sensing and pacing, and cause spurious pacemaker reprogramming. Pacemaker function can result in ICD oversensing, leading to inappropriate therapy, or cause ICD undersensing, potentially resulting in failure to deliver therapy during ventricular fibrillation. The susceptibility of an ICD to undersensing appears related to the amplitude of the pacing stimulus artifact recorded by the ICD rate-sensing circuit and to the characteristics of the fibrillation electrogram. Preliminary data suggest that undersensing of ventricular fibrillation by current ICDs is an unlikely event.

Interactions between transvenous nonthoracotomy cardioverter defibrillator systems and permanent transvenous endocardial pacemakers

Limited information is available regarding potential adverse interactions between transvenous nonthoracotomy cardioverter defibrillators and pacemakers. We describe our experience with 37 patients who have undergone successful implantation of both a transvenous defibrillator and pacemaker. The patients' mean age was 64 +/- 12.9 years. Thirty-three were male and four were female. The mean LVEF was 30.8% +/- 11.8%. The indications for pacemaker implantation included sick sinus syndrome in 13 patients, complete heart block in 15 patients, sinus bradycardia secondary to medications in 8 patients, and neurocardiogenic syncope in 1 patient. The indications for insertion of a defibrillator included medically refractory VT in 27 patients and sudden cardiac death in 10 patients. Twenty-three patients received an Endotak lead and 14 patients received a Transvene lead. Eighteen patients had a pacemaker prior to an ICD, 14 patients had an ICD prior to a pacemaker, and 4 patients had both devices placed simultaneously. Interaction was evaluated at implant of the second device and 1-3 days after both devices were placed. Detection of VF/VT was analyzed during asynchronous pacing (DOO/VOO) with maximum pacing output. In addition, in six patients, DFT was determined before and after pacemaker implantation. In 14 patients (38%), device interactions that could not always be optimally corrected were observed. In five patients, the pacemaker was reset to the "noise reversion" mode after high energy ICD discharge. Oversensing of atrial pacemaker stimuli resulted in inappropriate ICD firings in four patients. This was observed only with a specific device and could not be prevented by atrial lead repositioning in two of them, but required reprogramming of the pacemaker to the VVI mode. An increase in DFT was observed in five patients who had a pacemaker implanted after an ICD. Compared with previously published studies, a greater frequency of transvenous ICD and pacemaker interactions were observed. Considering that almost 50% of the patients already have a pacemaker at the time of ICD implant, the availability of defibrillators with dual chamber pacing capability will not eliminate the potential for this problem.

Impact of implant techniques on complications with current implantable cardioverter-defibrillator systems

Implantable cardioverter-defibrillator (ICD) treatment has been in use since 1980 to prevent sudden cardiac death. The high efficacy of the original epicardial systems to terminate tachyarrhythmias was impaired by a substantial perioperative mortality and morbidity. The more "modern" transvenous ICD systems have shown a similar high efficacy in terminating ventricular tachyarrhythmias, but with a lower mortality and morbidity. As a background for discussing the impact on complications with present transvenous implantation techniques, the literature was reviewed. A large pacemaker series was used for comparison. Lead complications clearly related to design, material, or manufacture were not reviewed. The present review, covering 107 references over 40 years, gives support for the notion that in transvenously implanted ICD patients the incidence of acute and late complications related to implantation technique is now acceptable. The rate of hematomas, symptomatic thromboembolic complications, perforations, and to a certain degree infections could be improved, however. The major risk factors for implantation-related complications are discussed, and suggestions for future improvement are given.

Transvenous defibrillation lead systems

The use of the implantable cardioverter defibrillator has grown dramatically over the past 10 years. One of the major advances in defibrillation technology is the development of transvenous lead systems. Compared with traditional epicardial lead systems, transvenous defibrillation leads reduce perioperative mortality, hospitalization, and costs. Transvenous lead systems provide reliable sensing of ventricular tachyarrhythmias, although redetection of ventricular fibrillation can be prolonged, especially with integrated lead systems. Both ramp and burst adaptive pacing are equally effective for the termination of ventricular tachycardia and are successful in up to 90% of spontaneous events. Defibrillation thresholds are higher with transvenous leads than with epicardial patches. These thresholds are reduced with the use of multiple transvenous leads, subcutaneous patches, or with reversing shock polarity. However, the development of biphasic waveforms has made the largest impact on the efficacy of these lead systems, allowing dual coil transvenous systems to be effective in about 90% of patients. Defibrillation efficacy is further enhanced and implantation simplified by the incorporation of an active pulse generator located in the left pectoral region. Active pectoral pulse generators with biphasic waveforms will be the primary lead system for new implants.