Failure of Defibrillator Paddle as Mimic for Subcutaneous Patch Lead During Nonthoracotomy Implantable Cardioverter Defibrillator Lead Configuration Assessment

It is a common, although virtually unsubstantiated, practice to assess the efficacy of nonthoracotomy lead systems for implantable cardioverter defibrillators using a defibrillator paddle as mimic for the subcutaneous patch lead. We report a case in which an adequate defibrillation threshold was documented with the nonthoracotomy lead system using a defibrillator paddle but not following implantation of the true subcutaneous patch lead. This case suggests that the substitution of a defibrillator paddle for the subcutaneous patch lead during nonthoracotomy lead system evaluation may have significant limitations in assessing lead configuration efficacy.     

A Prospective, Randomized Evaluation of a Nonthoracotomy Implantable Cardioverter Defibrillator Lead System

Nonthoracotomy lead systems for ICDs have been developed that obviate the need for a thoracotomy and reduce the morbidity and mortality associated with implantation. However, an adequate DFT cannot be achieved in some patients using transvenous electrodes alone. Thus, a new subcutaneous "array" electrode was designed and tested in a prospective, randomized trial that compared the DFT obtained using monophasic shock waveforms with a single transvenous lead alone that has two defibrillating electrodes, the transvenous lead linked to a subcutaneous/submuscular patch electrode, and the transvenous lead linked to the investigational array electrode. There were 267 patients randomized to one of the three nonthoracotomy ICD lead systems. All had DFTs that met the implantation criterion of ≤ 25 J. The resultant study population was 82% male and 18% female, mean age of 63 ± 11 years. The indication for ICD implantation was monomorphic VT in 70%, VF in 19%, monomorphic VT/VF in 6%, and polymorphic VT in 4% of the patients, respectively. The mean LVEF was 0.33 ± 0.13. The mean DFT obtained with the transvenous lead alone was 17.5 ± 4.9 J as compared to 16.9 ± 5.5 J with the lead linked to a patch electrode (P = NS), and 14.9 ± 5.6 with the lead linked to the array electrode (array versus lead alone, P = 0.0001; array versus lead/patch, P = 0.007). The results of this investigation suggest that the subcutaneous array may be superior to the standard patch as a subcutaneous electrode to lower the DFT and increase the margin of safety for successful nonthoracotomy defibrillation.     

Experience with Two Different Nonthoracotomy Systems for Implantable Defibrillator in 170 Patients

Implantation of a nonthoracotomy system (Medtronic PCD or CPI Endotak) was attempted in 170 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) not requiring concomitant cardiac surgery. A nonthoracotomy system could be successfully implanted in 95 of the 115 patients with the PCD system and 49 of 55 patients receiving the Endotak lead system. In 26 patients with failed nontboracotomy system because of defibrillation threshold (DFT) > 25 joules (J), an epicardial system was implanted at the same setting. Patients receiving the two lead systems were comparable with regard to age, sex, and ejection fraction. However, since tbe PCD system offers tiered therapy multiprogrammable options, all attempts were made to implant tbis lead system in patients with VT that could be pace terminated. Mean DFT(15 ± 4.7 vs 17 ± 4.6 J;P = 0.03) and implant time (2.5 ± 0.6 vs 3.3 ± 0.7 hours; P = 0.02) were less with the Endotak lead system. There was no perioperative mortality. During a mean follow-up of 20 ± 4 months, there were eight instances of lead dislodgment in patients receiving the PCD system. Tbere were four nonsudden cardiac deaths and one sudden death in the Endotak group and three nonsudden deaths in the PCD group. Sudden cardiac death and total survival using the intention-to-treat analysis during this follow-up period were 99% and 95%, respectively. In conclusion, successful implantation, perioperative mortality, and survival rate are comparable with both lead systems; however, incorporating two defibrillating electrodes in one lead minimizes lead dislodgment and reduces implant time.     

Initial Clinical Experience with a New Small Sized Third-Generation Implantable Cardioverter Defibrillator: Results of a Multicenter Study

This study reports the acute clinical experience with the new CPI VENTAK MINI: a small sized (68 cc), implantable cardioverter defibrillator (ICD) with 33 J stored energy. Implantation of the device was attempted in 113 patients (90 men, mean age 57 ± 16 years, 64 with coronary artery disease, mean left ventricular ejection fraction 41%) with ventricular tachycardia or ventricular fibrillation (VF). All 113 patients (100%) were ultimately implanted, 12% of them for ICD replacement. Transvenous lead implantation was accomplished in all 104 patients (100%) receiving new leads, 95% of them with a single lead configuration. The safety criteria for implantation (2 consecutive VF conversions at 15 J or 3 at 20 J. in both cases without failures to convert) were demonstrated in all but 7 patients (6%). In 6 of these, safety criteria were not fully assessed while in the last patient defibriliation efficacy was not determined. Of the 104 patients with new leads, 90% underwent pectoral implantation. Of the 9 patients (9%) abdominally implanted, only 4 (4%) (3 children) were judged small sized for pectoral implant. At predischarge testing, reliable VF detection and conversion were noted in 96 of 97 patients tested. There was no perioperative mortality. At a 3.6 ± 1.3 months follow-up, 34% of the patients had a spontaneous arrhythmic event, and 24% of the patients received shocks. Clinically inappropriate therapies occurred in 8% of the episodes in which any kind of therapy was delivered. This study demonstrates the short-term clinical efficacy and safety of the new device, and that pectoral implantation can be performed in the large majority of patients.     

Gross and Microscopic Changes Associated with a Nonthoracotomy Implantable Cardioverter Defibrillator

The pathology associated with an invesrigational transvenous defibriliating and sensing lead is described. The lead system had delivered a total of 865 J from the time of implantation to the time of patient death from a noncardiac cause 7 months after implantation and 1 month after his last defibrillator shock. There was mild, superficial fibrous thickening on the endothelial surface of the superior vena cava adjacent to the proximal spring electrode, which did not extend into the vessel wall. The distal portion of endocardial lead was embedded in the interventricular septum near the apex of the right ventricle, surrounded by fibrous thickening, and partially covered by endocardial tissue. Microscopically, there was a thick bed of fibrous connective tissue surrounding the lead with extensive interstitial fibrous connective tissue radiating into the adjacent myocardium. Since this pattern is different from the more generalized fibrotic scarring produced by myocardial infarction, we speculate that the mechanism for the observed interstitial fibrosis is replacement fibrosis following acute myocyte injury that resulted from prior defibrillator shocks and possibly from the trauma produced by the lead compressing adjacent myocardium during systole. Potential effects on device efficacy of these fibrotic changes at the bioelectric interface include their representing a new arrhythmia substrate, the possibility that fibrosis could increase both defibrillation and pacing thresholds, and that the inflammatory reaction may cause deterioration of intracardiac electrograms and interfere with sensing and tachycardia recognition.     

Implantable Cardioverter Defibrillator Implanted by Nonthoracotomy Approach: Initial Clinical Experience with the Redesigned Transvenous Lead System

Standard implantation procedure for the implantable Cardioverter defibrillator (ICD) has traditionary required a thoracotomy approach. A newly revised nonthoracotomy defibrillator lead system that uses a single transvenous tripolar endocardial lead alone or in combination with a subcutaneous/submuscular patch lead was introduced into clinical trials in September, 1990. Fourteen patients requiring a Cardioverter defibrillafor for recurrent sustained ventricular tachycardia (eight patients) or aborted sudden cardiac death (six patients) were evaluated for implantation of this lead system. Primary successful lead system implantation was obtained in nine patients. The remaining five patients had unacceptably high defibrillation thresholds (DFTs) for implantation. One of the nine initially successful implants demonstrated unacceptable DFTs and cross-talk inhibition from a permanent pacemaker necessitating removal of the nonthoracotomy lead system and replacement with a conventional lead system via thoracotomy. All remaining primary implanted patients experienced successful conversion of induced ventricular fibrillation prior to hospital discharge. Continued follow-up and greater experience to confirm the durability and efficacy of the nonthoracotomy AICD lead system are needed.     

Low Incidence of Lead Related Complications Associated with Nonthoracotomy Implantable Cardioverter Defibrillator Systems

Implantable cardioverter defibrillators (ICDs) are increasingly being implanted without the need for thoracotomy. Long-term lead performance and stability were evaluated in 150 consecutive patients in whom 1 of 3 nonthoracotomy ICD lead systems was implanted over a 3-year period from September 1990. Results: Twelve (8%) patients (7 males, 5 females) experienced 13 lead complications during a follow-up period of 12 ± 10 months. Complications were related to intracardiac leads in 7 (4 dislodgments, 2 fractures, 1 right ventricular perforation) and patch leads in 6 (2 folding, 1 fracture, 1 erosion, and 2 hematomas) cases. Freedom from lead related complications at 1 year was 92% (95% confidence interval, 86%–95%). A significant difference in freedom from lead complications between the two most frequently implanted lead systems was observed (P = 0.02). Complication rates were similar in the initial 75 and the more recent 75 implants (P= 0.5). The median time between lead implant and detection of complications was 37 days (range 3–1,147). Complications were diagnosed before hospital discharge in only two cases. In five patients, complications were asymptomatic and in three of these, reoperation was required due to inadequate defibrillation thresholds. Reoperation was necessary in 9 of 12 patients. Conclusions: Nonthoracotomy ICD lead systems are associated with a low complication rate. Complications may or may not cause symptoms, usually occur after hospital discharge, and require reoperation. Complications are not related to a "learning curve." There is a significant difference in performance between different lead systems.     

Implantable Cardioverter Defibrillator Events in Patients with Asymptomatic Nonsustained Ventricular Tachycardia:

Primary prevention trials have demonstrated that patients with coronary disease, reduced left ventricular function, and nonsustained ventricular tachycardia (NSVT) have improved survival with implantable cardioverter defibrillator (ICD) therapy, presumably secondary to effective termination of life-threatening arrhythmias. However, stored intracardiac electrograms were not always available and specific arrhythmias leading to ICD therapy were not always known. We examined the occurrence of ICD events in 51 consecutive patients who match the described patient profile to determine the frequency of appropriate and inappropriate ICD therapy. ICD detections were noted in 18 (35%) patients during a median follow-up period of 13.1 months. Appropriate therapy for sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) occurred in 11 (22%) patients, with appropriate shocks in 8 (16%) patients and appropriate antitachycardia pacing (ATP) in 4 (8%) patients. The time to first appropriate therapy occurred at a mean of 17 +/- 12 months (median 18 months, range 3-36 months). Inappropriate therapy occurred in 5 (10%) patients with inappropriate shocks in 4 patients and inappropriate ATP in 2 patients. Inappropriate therapy was delivered for supraventricular arrhythmias (SVAs) in 4 patients and for T wave oversensing in 1 patient. The reason for shock therapy was unknown in 1 patient (2%) due to ICD malfunction. The mean arrhythmia rate leading to appropriate therapy for VT/VF was 232 +/- 72 beats/min (range 181-400 beats/min), and the mean rate leading to inappropriate therapy for SVT was 168 +/- 10 beats/min (range 160-180 beats/min). Patients with coronary disease and asymptomatic NSVT commonly receive appropriate defibrillator therapy. These results support the need for ICD implantation for primary prevention, with attention to careful programming of the detection rate to prevent inappropriate therapy.     

A Second Defibrillator Chest Patch Electrode Will Increase Implantation Rates for Nonthoracotomy Defibrillators

Nonthoracotomy defibrillator systems can be implanted with a lower morbidity and mortality, compared to epicardial systems. However, implantation may be unsuccessful in up to 15% of patients, using a monophasic waveform. It was the purpose of this study to prospectively examine the efficacy of a second chest patch electrode in a nonthoracotomy defibrillator system. Fourteen patients (mean age 62 ± 11 years, ejection fraction = 0.29 ± 0.12) with elevated defibrillation thresholds, defined as ≥ 24 J, were studied. The initial lead system consisted of a right ventricular electrode (cathode), a left innominate vein, and subscapular chest patch electrode (anodes). If the initial defibrillation threshold was ≥ 24 J, a second chest patch electrode was added. This was placed subcutaneously in the anterior chest (8 cases), or submuscularly in the subscapular space (6 cases). This resulted in a decrease in the system impedance at the defibrillation threshold, from 72.3 ± 13.3 Ω to 52.2 ± 8.6 Ω. Additionally, the defibrillation threshold decreased from ≥ 24 J, with a single patch, to 16.6 ± 2.8 J with two patches. These changes were associated with successful implantation of a nonthoracotomy defibrillator system in all cases. In conclusion, the addition of a second chest patch electrode (using a subscapular approach) will result in lower defibrillation thresholds in patients with high defibrillation thresholds, and will subsequently increase implantation rates for nonthoracotomy defibrillators.     

Patient Acceptance of the Implantable Cardioverter Defibrillator in Ventricular Tachyarrhythmias

Besides surgical problems, recipierifs of implantable cardioverter defibrillators (ICDs) are faced with psychological and social adjustments. Successful ICD therapy is influenced by the patients' perceived concerns regarding device, discharge, changes in life style, and complications. In order to assess patients' acceptance of the ICD, the psychological profile of 57 consecutive patients was evaluated using a specifically designed questionnaire and the State Trait Anxiety Inventory (STAI). The results showed that 20 patients staled fear of ICD discharge, 12 patients revealed physical discomfort due to the device, and limited quality-of-life occurred in 8 patients. Fifty-five of 57 patients answered that it was worth having an ICD device implanted, 30 (53%) patients returned to active life, and 56 (98%) would advise another patient to undergo implantation if necessary. Overall, there was only a slight, but insignificant, decrease in the level of anxiety within the total patient population after ICD implantation. However, a comparison of two subgroups indicated that the state of anxiety was significantly higher in patients < 50 years of age as well as in patients having received > 5 shocks versus those > 50 years of age and having experienced < 5 shocks. In general, the acceptance of the ICD as a tool in managing life-threatening ventricular tachyarrhythmias is high. Besides the increased survival rate, quality-of-life and patient acceptance are important criteria for successful ICD therapy.     

Sudden Death Mortality in Implantable Cardioverter Defibrillator Patients

Implanfable Cardioverter defibrillator (ICD) prevention of sudden cardiac death (SCD) is not absolute and our experience was reviewed to determine the frequency and nature of SCO in this population. The incidence and cause of mortality in 56 consecutive patients, who underwent ICD implantation beginning May 1982 with follow-up through May 19, 1990 were analyzed. Twenty-one patients died, 33% of the mortality was due to SCD, and 52% of deaths may be considered arrhythmic. The cumulative 1, 3, and 5 year SCD survivals were 93%, 89%, and 75%. All seven patients dying of SCD presented initially with SCD, all received previous shocks prior to SCD, and two of the seven patients had devices that were probably inactive at the time of death. We conclude that ICDs reduce but by no means eliminate arrhythmic death, particularly in those at highest risk for SCD. Arrhythmic death remained the most common cause of death in this population.     

Long-Term Follow-Up of Patients with Nonischemic Dilated Cardiomyopathy and Ventricular Tachyarrhythmias Treated with Implantable Cardioverter Defibrillators

We analyzed our 10-year cumulative experience of 40 consecutive patients with idiopathic dilated Cardiomyopathy and associated ventricular tachyarrhythmias, treated with implantable Cardioverter defibrillators. Dilated Cardiomyopathy was defined as left ventricular ejection fraction (EF) ≤50% with no defineable etiology. Patient characteristics included: 24 male, mean age 52 years, mean EF = 33%, New York Heart Association Class I–III, presenting syndrome—cardiac arrest (n = 28), syncope/near syncope (n = 12). At 2.5 years mean follow-up, there were 16 deaths: one operative, three sudden, two incessant ventricular tachycardia/ventricular fibrillation (VT/VF), six heart failure, and four noncardiac. The actuarial mortality at 1 and 4 years was 0% and 14% for sudden death, 11% and 34% for cardiac death. The projected mortality was 52% and 78% for same time intervals (P < 0.01). No useful baseline variable predicted who would or would not receive an ICD shock in follow-up. ICD therapy appears effective in reducing sudden death mortality in this high risk population.     

Automatic Implantable Cardioverter/ Defibrillator (AICD) and Antitachycardia Pacemaker (Tachylog): Combined use in Ventricular Tachyarrhythmias

Antitachycardia pacing in ventricular tachyarrhythmias (VT) is associated with potential acceleration of VT: frequency of VT and discomfort of the patient (pt) can limit treatment with the AICD. We therefore evaluated the combined use of antitachycardia pacing and AICD in 6 of 14 patients (age 50–70. mean 60 years) with AICD implantation because of VT, which could he terminated by temporary overdrive pacing. With the interactive mode of the Tachylog, termination of VT by the pacemaker as well as by the AICD was assessed after implantation. In the automatic mode, the Tachylog functioned as a bipolar VVI device with antitachycardia burst stimulation: 2–5 stimuli, interval 260–300 ms. 1–2 interventions. During follow-up of 12±5 months, the Tachylog terminated VT reliably 20 to 327 times per patient. In three patients, burst stimulation accelerated VT, which was terminated then by the AICD discharge. Conclusion: Drug resistant ventricular tachyarrhythmias can be terminated by the Tachylog pacemaker avoiding patients' discomfort. In case of acceleration. ventricular tachyarrhythmias can be controlled by the automatic implantable cardioverter/defibrillator. A universal pacemaker should combine antitachycardia pacing with back-up defibrillation mode.     

Ventricular Pacing Induced Ventricular Tachycardia in Patients with Implantable Cardioverter Defibrillators

Appropriately timed noncompetitive ventricular pacing potentially may initiate ventricular tachycardia in patients prone to these arrhythmias. The combination of bradycardia pacing and stored electrograms in a currently available cardioverter defibrillator provides an opportunity to evaluate the occurrence of such pacing induced ventricular tachycardia. During a surveillance period of 18.7 ± 11.4 months, stored electrograms documented 302 episodes of ventricular tachycardia in 77 patients. Five patients (6.5%) demonstrated 25 episodes (1–16 per patient) of ventricular tachycardia that were immediately preceded by an appropriately paced ventricular beat (8.3% of all episodes of ventricular tachycardia). All five patients had prior myocardial infarctions and a history of monomorphic ventricular tachycardia occurring both spontaneously and in response to programmed electrical stimulation. Antitachycardia pacing terminated pacing induced ventricular tachycardia in 22 episodes; in one episode antitachycardia pacing accelerated ventricular tachycardia. In two cases shock therapy was aborted for nonsustained ventricular tachycardia. We conclude that, in selected postinfarction patients with recurrent sustained monomorphic ventricular tachycardia treated with implantable cardioverter defibrillators, appropriately timed ventricular pacing may induce ventricular tachycardia.     

Implantable Cardioverter Defibrillator Detection During Radiofrequency Catheter Ablation of Ventricular Tachycardia

Right ventricular radiofrequency catheter ablation was performed in an ICD patient with frequent ventricular tachycardia without prior inactivation of the device. The registrations of inlracardiac ECG and marker channel were excellent during energy delivery: the surface ECG was affected. The device did not show dysfunction during and after energy delivery.     

Infections in Implantable Cardioverter Defibrillator Patients

Implantable cardioverter de;fibrillators fICDsj have been documented as an effective modality in reducing arrhythmic mortality. A serious complication associated with implantation of the device is infection. Few studies have addressed this issue. Two hundred seven patients with refractory ventricular arrhythmias underwent 207 ICD implantations, and 56 subcutaneous generator changes at our institution. Eight patients developed wound infections, four following ICD implantation (4 out of 207 or 1.9%), and four following a generator change (4 out of 56 or 7.1%). Wound cultures most commonly revealed Staphylococcus aurous and Staphylococcus epidermidis. Infections treated with antibiotics alone, or with only generator removal, frequently recurred (four out of five attempts). There were no recurrences following total patch/lead and generator system removal. In jive patients, the same generator unit was successfully emplaned following ethylene oxide sterilization without infection recurrence. We conclude that treatment of device-associated infection generally requires total generator and patch/lead system removal, and that generator units can be successfully reimplanted yielding substantial cost savings.     

Effectiveness of Noninvasive Programmed Stimulation for Initiating Ventricular Tachyarrhythmias in Patients with Third-Generation Implantable Cardioverter Definrillators

Previous generations of implantable cardioverter defibrillators (ICDs) required invasive electrophysiological testing to assess defibrillator function. Newer third-generation ICDs include the capability for performing noninvasive programmed stimulation (NIPS) and may reduce the need for invasive studies to assess tachycardia recognition and antitachycardia therapy algorithms. The effectiveness of ICD-based NIPS for the induction of ventricular arrhythmias has not, however, been formally assessed. Third-generation ICDs were implanted in 79 patients, who underwent a total of 166 postoperative defibrillator tests. NIPS with rapid ventricular pacing was performed in all patients in an attempt to induce ventricular fibrillation. In patients with prior sustained uniform ventricular tachycardia, programmed stimulation with up to three extrastimuli was performed in order to attempt to initiate the clinical ventricular tachcardia. Ventricular fibrillation was induced with NIPS in 146 of 166 studies (88%). Ventricular tachycardia was initiated with NIPS in 104 of 123 studies (85%). The type of defibrillator and the use of endocardial or epicardial rate sensing/ pacing leads did not influence the efficacy of NIPS. NIPS with third-generation ICDs is generally effective at inducing ventricular fibrillation and clinically relevant ventricular tachycardias, and reduces the need to perform invasive electrophysiological testing following device implantation. In a minority of patients temporary transvenous pacing catheters must still be used to facilitate arrhythmia induction.     

Implantation of a Nonthoracotomy Defibrillator Using a Second Defibrillator Patch in the Abdominal Pocket

Successful implantation of a biphasic nonthoracotomy implantable cardioverter defibrillator may not be achieved with a conventional system. We describe a successful device implantation using a pectoral and abdominal patch electrode system.     

Cost and Length of Hospital Stay: Comparisons Between Nonthoracotomy and Epicardial Techniques in Patients Receiving Implantable Cardioverter Defibrillators

Twenty-five patients with implantable Cardioverter defibrillators (ICDs) implanted intrathoracically (group I) were compared with 25 patients who underwent implant using the nonthoracotomy approach (group II). AH systems were implanted by the same medical team, in the same high volume implanting center. Indications for implantation were comparable in both groups. Patient characteristics were not statistically different with the exception of age fee-group I vs 71-group II; P < 0.05). Although left ventricular ejection fractions appeared to differ (32% vs 37%, respectively), this difference was not statistically significant (P = 0.06). ICD models used in group I were: Ventritex Cadence (16), Telectronics Guardian 4211 (2), Medtronic PCD (7); in group II they were: Ventritex Cadence (15), Guardian 4211 (2), and CPI 1600 (1). Total length of hospital stay was 16 ± 6 days for group I versus 12 ± 5 for group II (P < 0.05). Number of postoperative days in an intensive care unit was 3.2 ± 2.8 for group I versus 0.5 ± 0.6 for group II (P < 0.0001). Postoperative length of stay was 8.2 ± 3.1 for group I versus 5.7 ± 4.4 for group II (P < 0.001). Mean total hospital charges for the entire length of stay were $72,918 ±$26,770 in group I versus $55,031 ±$42,870 in group II, representing a mean reduction of 21 % in global costs for group II patients. These data confirm that nonthoracotomy ICD implantation in an experienced center is associated with significantly shorter hospital stays, a virtual elimination of the need for postoperative intensive care, and globally lower total hospital costs. In addition, the presence of a statistically older population in group II does not negate these beneficial effects.