Biphasic Defibrillation Using a Single Capacitor with Large Capacitance: Reduction of Peak Voltages and ICD Device Size

The volume of current implantable cardioverter defibrillators (ICD) is not convenient for pectoral implantation. One way to reduce the size of the pulse generator is to find a more effective defibrillation pulse waveform generated from smaller volume capacitors. In a prospective randomized crossover study we compared the step-down defibrillation threshold (DFT) of a standard biphasic waveform (STD), delivered by two 250-μF capacitors connected in series with an 80% tilt, to an experimental biphasic waveform delivered by a single 450μF capacitor with a 60% tilt. The experimental waveform delivered the same energy with a lower peak voltage and a longer duration (LVLDj. Intraopera-tively, in 25 patients receiving endocardial (n = 12) or endocardial-subcutaneous array (n = 13) defibrillation leads, the DFT was determined for both waveforms. Energy requirements did not differ at DFT for the STD and LVLD waveforms with the low impedance (32 ± 4Ω) endocardial-subcutaneous array defibrillation lead system (6.4 ± 4.4 J and 5.9 ± 4.2 J, respectively) or increased slightly (P - 0.06) with the higher impedance (42 ± 4 Ω) endocardial lead system (10.4 ± 4.6 J and 12.7 ± 5.7 /. respectively), However, the voltage needed at DFT was one-third lower with the LVLD waveform than with the STD waveform for both lead systems (256 ± 85 V vs 154 ± 53 V and 348 ± 76 V vs 232 ± 54 V, respectively). Thus, a single capacitor with a large capacitance can generate a defibrillation pulse with a substantial lower peak voltage requirement without significantly increasing the energy requirements. The volume reduction in using a single capacitor can decrease ICD device size.     

Effects of Antiarrhythmic Drugs on Epicardial Defibrillation Energy Requirements and the Rate of Defibrillator Discharges

Antiarrhythmic drugs are commonly used with the implantable cardioverter/defibrillator to treat recurrent ventricular tachyarrhythmias. Since various antiarrhythmic drugs have been reported to alter defibrillation threshold, an important question is whether the device will provide adequate energy for defibrillation during long-term follow-up and to what extent antiarrhythmic drug treatment will affect defibrillation energy requirements. To answer these questions, the defibrillation thresholds were determined in 20 patients using an epicardial patch-patch lead configuration at the time of implantation and at the time of pulse generator replacement. During a mean follow-up period of 24 ± 6 months, the defibrillation threshold increased significantly from 14.2 ± 3.7 joules to 18.3 ± 5.5 joules in the entire group (P < 0.05). This increase in defibrillation threshold was due to a marked elevation of defibrillation energy requirements in the subgroup of patients taking amiodarone compared with patients receiving mexiletine. Based on these results it is mandatory to retest defibrillation threshold at any time of pulse generator replacement to guarantee continued effectiveness. In particular, if amiodarone treatment is initiated after implantation of a defibrillator, it is recommended to reevaluate defibrillation threshold to ensure an adequate margin of safety.     

Replacing Abdominally Implanted Defibrillators: Effect of Procedure Setting on Cost

Although most ICDs are currently placed using a pectoral approach, there exists a large population of patients with abdominally implanted ICDs who will require device replacement due to a depleted battery. The purpose of this study was to compare the cost, convalescence, and complication rate of replacing abdominally implanted ICDs in the OR versus the EP laboratory. Between August 1993 and September 1994, we prospectively enlisted nine consecutive patients who presented for their second ICD generator replacement and who had a prior generator replacement in the OR 3-4 years earlier. The mean age of the patients was 63 +/- 17 years and their mean ejection fraction was 37% +/- 15%. ICD replacement was performed in the EP laboratory and consisted of explanting the old device, electronic interrogation of the lead system, and confirmation of defibrillation thresholds prior to implanting a new device. Local anesthesia was provided by lidocaine infiltration and sedation was achieved with intravenous (i.v.) midazolam and fentanyl. Following the procedure, the patients were returned to an outpatient monitored setting for 4 hours and were then discharged. Comparisons of the health care charges for the same procedure performed in the two different settings revealed a significant reduction in physician fees (from $3,621 +/- $556 to $2,179 +/- $577, P < 0.05), in hospital charges (from $5,811 +/- $1,102 to $2,306 +/- 696, P < 0.05), and in total charges (from $9,431 +/- $1,375 to $4,541 +/- $1,010, P < 0.05), exclusive of ICD cost, when the procedure was performed on an outpatient basis in the EP laboratory. Inpatient days averaged 3.0 +/- 0.3 when the procedure was performed in the OR. On long-term follow-up there were no complications following abdominal ICD generator replacement in the OR (mean follow-up, 39 +/- 2 months) or in the EP laboratory (mean follow-up, 42 +/- 4 months). Thus, ICD replacements in the EP laboratory cost less than in the OR due to significantly lower physician fees, hospital charges, and a shorter postprocedural convalescence.     

Long-Term Stability of Defibrillation Thresholds with Intrapericardial Defibrillator Patches

From March 1982 to May 1, 1992, 105 consecutive patients underwent initial implant of cardioverter defibrillators (ICD) at our institution. Twenty-nine patients (23 male and 6 female, average ejection fraction 32.24%) with ICD systems implanted via thoracotomy and either intra- or extrapericardial patches, had one or more revisions including 56 generator changes or staged implant procedures, three patch revisions, one patch lead fracture without revision, and one sensing lead revision. The time between pulse generator revisions averaged 19.5 months. Initial defibrillation threshold mean was 12.8 joules (n = 25); at first revision, 14.46 joules (n = 29), (P = NS); by fifth revision, 15.0 joules (n = 2), (P = NS). One patch was noted to be crinkled at 70 months; one patch had migrated by 39 months, and two patch leads had fractured at the costal margin by 69 and 90 months. One patient with marginal defibrillation thresholds had an additional patch placed at revision to an upgraded ICD unit. Once acceptable defibrillation threshold (DFT) is obtained, the long-term intrapericardial DFT remains stable unless a specific problem occurs. As a small, nonstatistically significant increase in DFT may occur, caution must be exercised in patients with marginal DFTs.     

Performance of Implantable Defibrillator Pacing/Sensing Lead Adapters

The wide variety of implantable defibrillators (ICDs) available from different manufacturers and the lack of universal industry standards has resulted in the frequent need for lead adapters at time of ICD implant or change. We analyzed the performance of 81 consecutive ICD sensing/pacing lead adapters used between 1988 and 1993. A total of 66 adapters was used for new epicardial systems, and 15 adapters served as lead connectors during ICD generator replacement, Pacing/sensing lead adapters used were: model LA-201 (n = 28; 34.5%); model 030–308 (n = 26; 32%); model 5866–24 (n = 15; 18.5%); and miscellaneous (n = 12; 15%). After a mean follow-up of 21 ± 16 months, nine pacing/sensing lead adapters had documented or strongly suspected failure. Most often pacing/sensing lead adapters presented clinically as frequent aborted shocks. Actuarial probability of freedom from failure for model LA-201 was 83% at 1 year, and 72% at 2 and 3 years; this was poorer than for the other sensing leads combined (P = 0.01; hazard ratio = 4.92; 95% confidence intervals = 1.2–20; log-rank test). In conclusion, pacing/sensing lead adapters are a potential source of ICD system complications. Performance is dissimilar among different models; specifically, model LA-201 may not be safe in the long-term, and patients with this lead adapter need to be closely monitored.     

The Left Subclavian Vein as an Alternative Site for Implantation of the Second Defibrillation Lead

The optimal placement for the second defibrillation lead in a twolead system has never been addressed. We retrospectively reviewed the data of 33 patients with an average age of 59.2 years (range 41–78 years), predominantly mala (n = 29), who underwent implantation of a cardioverter defibrillator (ICD) for treatment of ventricular tachycardia (n = 19) or ventricular fibrillation (n = 14). In all patients an attempt was made to implant an endovenous ICD device (leads only, no subcutaneous patch). In group I (n = 18) the defibrillation anode, a separate unipolar lead, was placed in the common position, the superior vena cava. In group II (n =15) the lead was placed in the left subclavian vein. At least two consecutive shocks reverting ventricular fibrillation at energies ±24J were required for implantation of the ICD device. All shocks were monophasic. The success rate of endovenous defibrillation was significantly higher in group II than in group I (67% vs 28%, P < 0.05). Thus, it could be demonstrated that the position of the defibrillation anode can influence the defibrillation efficacy in transvenous ICD systems. Prospective randomized trials are needed to investigate the optimal position for the second defibrillation electrode, which may gain increasing importance as soon as dual chamber ICDs become available.     

Left Ventricular Mechanical Assist Devices and Cardiac Device Interactions: An Observational Case Series

Background: Nonpulsatile left ventricular assist devices (LVADs) are increasingly used for treatment of refractory heart failure. A majority of such patients have implanted cardiac devices, namely implantable cardioverter-defibrillators (ICDs) or cardiac resynchronization therapy-pacemaker (CRT-P) or cardiac resynchronization therapy-defibrillator (CRT-D) devices. However, potential interactions between LVADs and cardiac devices in this category of patients remain unknown.
Methods: We reviewed case records and device logs of 15 patients with ICDs or CRT-P or CRT-D devices who subsequently had implantation of a VentrAssist LVAD (Ventracor Ltd., Chatswood, Australia) as destination therapy or bridge to heart transplantation. Pacemaker and ICD lead parameters before and after LVAD implant were compared. In addition, ventricular tachyarrhythmia event logs and potential electromagnetic interference reports were evaluated.
Results: Right ventricular (RV) sensing decreased in the first 6 months post-LVAD. Mean R-wave amplitude preimplant was 10.9 ± 5.25 mV compared with 7.2 ± 3.4 mV during follow-up (P = 0.02). RV impedance also decreased from 642 ± 240 ohms at baseline to 580 ± 212 ohms at follow-up (P = 0.007). There was a significant increase in RV stimulation threshold following implantation of the LVAD from 0.8 ± 0.6 V at baseline to 1.4 ± 1.0 V in the first 6 months postimplant (P = 0.01). A marked increase in ventricular tachyarrhythmia burden was observed in three patients. One patient displayed electromagnetic interference between the LVAD and defibrillator, resulting in inappropriate defibrillation therapy.
Conclusions: LVADs have a definite impact on cardiac devices in respect with alteration of lead parameters, ventricular tachyarrhythmias, and electromagnetic interference.     

Preliminary Clinical Results of a Biphasic Waveform and an RV Lead System

Biphasic defibrillation waveforms have provided a reduction in defibrillation thresholds in transvenous ICD systems. Although a variety of biphasic waveforms have been tested, the optimal pulse durations and tilts have yet to be identified. A multicenter clinical study was conducted to evaluate the performance of a new ICD biphasic waveform and new RV active fixation steroid eluting lead system. Fifty-three patients were entered into the study. Mean age was 63 years with a mean ejection fraction of 36.8%. Primary indication for implantation was monomorphic ventricular tachycardia alone (54.7%). Forty-eight patients (90.6%) were implanted with an RV shocking lead and active can alone as the anodal contact. The ICD can was the cathode. In four cases (7.5%), an additional SVC or CS had was used due to a high DFT with the RV lead alone. In an additional case, a chronic SVC lead was used although the RV-Can DFT was acceptable. DFT for all cases at implant was 9.8 ± 3.7 J. Repeat testing at 3 months for a subset of patients showed a reduction in DFT (7.4 ± 3.0 J), P value = 0.03. Sensing and pacing characteristics of the RV lead system remained excellent during the study period (acute 0.047 ± 0.005 ms at 5.4 V and 9.9 ± 6.2 mV R wave; chronic 0.067 ± 0.11 ms at 5.4 V and 9.3 ± 5.4 mV R wave). It is concluded that this lead system provides good acute and chronic sensing and pacing characteristics with good DFT values in combination with this waveform.     

Defibrillation Thresholds and Perioperative Mortality Associated with Endocardial and Epicardial Defihrillation Lead Systems

Defibrillation thresholds (DFT) and perioperative mortality were evaluated in 123 patients who had endocardial defibrillation leads implanted in conjunction with the Medtronic model 7216A/7217 (Medtronic, Inc.) cardioverter-defibrillator (ICD). Clinical variables, implant DFTs, and 30-day perioperative mortality were compared with 266 patients who had the ICD implanted with epicardial defibrillation leads. The two groups were comparable in age, gender, and incidence of coronary artery disease. New York Heart Association Class I and II were more frequent in patients with endocardial leads (87.7%) as compared to those with epicardial leads (78.8%; P < 0.001). Mean left ventricular ejection fraction was significantly higher in patients with the endocardial lead system (37% vs 33%; P < 0.05). A significant proportion of patients with epicardial lead systems underwent another cardiac surgical procedure at the time of ICD implantation (13.9%) as compared to none in those who had endocardial leads implanted (P < 0.001). All patients with endocardial leads had implantation of triple lead systems as compared to 53.4% with epicardial leads (P < 0.001). The mean DFT at implant was lower in epicardial lead recipients (8.9 J) as compared to endocardial lead recipients (13.3 J; P < 0.001). Perioperative mortality had a significant trend to lower risk for endocardial lead systems (0.8%) as compared to epicardial systems (4.2%; P = 0.07). We conclude that this endocardial lead system has additional electrode and higher defibrillation energy requirements than the epicardial lead systems used with the Medtronic pacemaker ICD. However, the use of endocardial nonthoracotomy defibrillation leads is associated with a markedly reduced perioperative risk of ICD implantation. This could be due to patient characteristics, a less invasive implant procedure, and absence of concomitant cardiac surgery.     

Bidirectional Defibrillation Using Implantable Defibrillators: A Prospective Randomized Comparison Between Pectoral and Abdominal Active Generators

SANDSTEDT, B., et al. : Bidirectional Defibrillation Using Implantable Defibrillators: A Prospective Randomized Comparison Between Pectoral and Abdominal Active Generators. The objective of this study was to compare the effects of active abdominal and pectoral generator positions on DFTs in a bidirectional tripolar ICD system. Twenty-five consecutive patients had ICD systems implanted under general anesthesia. A transvenous single lead bipolar defibrillation system and an active 57-cc test emulator in the abdominal and pectoral positions were used in the same patient. A randomized, alternating stepdown protocol was used starting at 15 J with 3-J decrements until failure. The mean implantation time was  114 ± 23 minutes  , the mean arrhythmia duration was  14.5 ± 1.5 seconds  , and the mean recovery time was  5.4 ± 1.1 minutes  . The mean DFTs in the abdominal and pectoral positions were  10.9 ± 5.1  and  9.7 ± 5.2 J  , respectively (NS), the mean intraindividual DFT difference (abdominal minus pectoral) was  −0.89 ± 4.15 J  (  range −9.5 to + 5.8 J  ). The 95% confidence interval showed a  −2.60 to + 0.82 J  mean difference (NS). The DFT was < 15 J in 72% and 88% of the patients and the defibrillation impedance was  41 ± 3  and  44 ± 3 Ω  , abdominal versus pectoral positions. There was no difference in DFT between active abdominal and pectoral generator bidirectional tripolar defibrillation. The pectoral position may be considered the primary option, but in cases of high DFTs the abdominal site should be considered an alternative to adding a subcutaneous patch. In some patients, the anatomy may favor an abdominal position. Possible differences in the long-term functionality on the leads are not yet well known and need to be further evaluated.     

Implantation of a Dual Chamber Pacing and Sensing Single Pass Defibrillation Lead

GRADAUS, R., et al. : Implantation of a Dual Chamber Pacing and Sensing Single Pass Defibrillation Lead. Dual-chamber ICDs are increasingly used to avoid inappropriate shocks due to supraventricular tachycardias. Additionally, many ICD patients will probably benefit from dual chamber pacing. The purpose of this pilot study was to evaluate the intraoperative performance and short-term follow-up of an innovative single pass right ventricular defibrillation lead capable of bipolar sensing and pacing in the right atrium and ventricle. Implantation of this single pass right ventricular defibrillation lead was successful in all 13 patients (  age 63 ± 8 years  ; LVEF  0.44 ± 0.16  ; New York Heart Association [NYHA]  2.4 ± 0.4  , previous open heart surgery in all patients). The operation time was  79 ± 29  minutes, the fluoroscopy time  4.7 ± 3.1  minutes. No perioperative complications occurred. The intraoperative atrial sensing was  1.7 ± 0.5 mV  , the atrial pacing threshold product was  0.20 ± 0.14 V/ms  (  range 0.03–0.50 V/ms  ). The defibrillation threshold was  8.8 ± 2.7 J  . At prehospital discharge and at 1-month and 3-month follow-up, atrial sensing was  1.9 ± 0.9, 2.1 ± 0.5, and 2.7 ± 0.6 mV  , respectively, (  P = NS, P < 0.05, P < 0.05  to implant, respectively), the mean atrial threshold product  0.79, 1.65, and 1.29 V/ms  , respectively. In two patients, an intermittent exit block occurred in different body postures. All spontaneous and induced ventricular arrhythmias were detected and terminated appropriately. Thus, in a highly selected patient group, atrial and ventricular sensing and pacing with a single lead is possible under consideration of an atrial pacing dysfunction in 17% of patients.     

Sensing Lead Insulation Defect Resulting in a Damage of the ICD Pulse Generator Case

Eight months after ICD implantation with an electrically active case the patient presented with ICD system sensing failure. Upon re-operation, we found an insulation defect of the proximal sensing lead and the generator case showed arc marks suggesting a short circuit between the sensing lead and case. the generator was replaced, the original sensing lead insulated, and a new sensing lead inserted. Bench testing of the explanted generator showed a damaged internal circuitry. Proximal lead insulation defects combined with electrically active cases may result in damage of the case. The potential damage of internal circuitry warrants generator replacement.     

AutoCapture with Dual-Coil Leads of Implantable Cardioverter Defibrillator

AutoCapture™ (AC) can confirm ventricular capture with true bipolar single coil leads of implantable cardioverter defibrillators (ICD). The compatibility of AC with a new, true bipolar, dual-coil ICD lead needed to be evaluated. This multicenter study enrolled 46 patients (69 ± 10 years, 37 men) undergoing ICD implantation. All patients received a true bipolar, dual-coil lead. Evoked response (ER) sensitivity and AC threshold tests were performed using a pulse generator with the AC algorithm. Mean capture threshold was 0.85 ± 0.67 V, pacing impedance 612 ± 225 Ω, R wave amplitude 13.85 ± 6.17 mV, and defibrillation threshold 14.4 ± 5.1 J. AC was recommended in 45 patients (97.8%) with ER and polarization values of 14.86 ± 7.32 mV and 0.87 ± 0.69 mV, respectively. The AC algorithm was highly compatible with true bipolar, dual-coil ICD leads. An AC algorithm specifically designed for an ICD may improve the generator longevity. Further examination of AC compatibility with other leads is warranted.     

Thoracoscopic Approach to Implantable Cardioverter Defibrillator Patch Electrode Implantation

Even if transvenous lead system for automatic implantable Cardioverter defibrillators (ICDs) has been one of the main surgical advances in the recent past, its major limitation is the high defibrillation thresholds in some cases. Thus, an additional patch may be required and implanted either in a subcutaneous position or in an epicardial position. We describe another possibility: the implantation of extrapericardial patch under video-thoracoscopic control. This new technique allows a deep implantation of the whole material without thoracotomy. Seven patients were included in our preliminary experience. During defibrillation threshold evaluation, two patients required 34 J with the single transvenous lead system, and five patients were not defibrillated with the single lead system; therefore, they required a 300-J external rescue shock. We decided to implant an additional patch in those seven patients with high defibrillation thresholds. This patch was inserted into the pleural cavity through a left subcostal incision. Under video thoracoscopy, it was positioned and stitched onto the pericardium. The defibrillation generator was then implanted through the left subcostal incision in a subdiaphragmatic space. As a result, pre-operative defibrillation thresholds were significantly reduced (14.29 ± 3.45 J, mean ± SD) and remained stable during follow-up controls (eighth day and second month). Long-term follow-up (14 ± 4.5 months) was uneventful, with an excellent tolerance for the patients. In conclusion, extrapericardial implantation of defibrillation patches under video thoracoscopy is an easy technique that allows low defibrillation thresholds.     

Improved Sensing Signals After Endocardial Defibrillation with a Redesigned Integrated Sense Pace Defibrillation Lead

Adequate sensing is a basic requirement for appropriate therapy with ICDs. Integrated sense pace defibrillation leads, which facilitate ICD implantation, show a close proximity of sensing and defibrillation electrodes that might affect the sensing signal amplitude by the high currents of internal defibrillation. In 99 patients, we retrospectively examined two integrated sense pace defibrillation leads, eitherboth with a distance of 6 mm between the tip of the lead (sensing cathode) and the right ventricular defibrillation electrode (sensing anode) or one with a distance of 12 mm. Three seconds after a shock of 20 J, mean sensing signal amplitude during sinus rhythm (SR) decreased from 10.5 ± 4.3 mVto 5.1 ± 3.7 mV (P < 0.001) for the 6-mm lead, but showed no significant decrease for the 12-mm lead. The degree of signal reduction was inversely related to the time passed since defibrillation. Significant differences in reduction of sensing signal amplitude concerning monophasic and biphasic shocks could not be observed. Mean sensing signal amplitude of VF after shocks that failed to terminate it decreased in the same order as during SR (from 8.3 ± 4.1 mV to 4.1 ± 3.2 mV), but resulted in no failure of redetection during ongoing VF. DFTs did not differ for the 6-mm and the 12-mm lead. In conclusion, close proximity of the right ventricular defibrillation coil to the sensing tip of an integrated sense pace defibrillation lead causes energy and time related reductions in sensing signal amplitude after defibrillation, and might cause undersensing in the postshock period. A new lead design with a more proximal position of the right ventricular defibrillation coil avoids these problems without impairing DFTs.     

Durability of repaired sensing leads equivalent to that of new leads in implantable cardioverter defibrillator patients with sensing abnormalities

Breaks in the insulation portions of implantable cardioverter defibrillator (ICD) leads may cause nonphysiological sensing and subsequent inappropriate ICD therapy, and may also interfere with the sensing and pacing functions of the ICD. Previously, leads with insulation breaks have been replaced with new sensing leads. However, repair of leads, utilizing a commercially available patch kit may reduce the morbidity, hospital stay, and cost of lead replacement. The long-term durability of these repairs has not previously been reported and is the subject of this study. Patients undergoing ICD sensing lead repair or replacement constituted the study population. Patients were followed at 3 month intervals with an endpoint of new lead abnormalities necessitating repeat lead repair or replacement. Twenty-five patients underwent lead repair and 27 individuals underwent lead replacement for either preoperative nonphysiological sensing (n = 25) or intraoperative evidence of insulation break (n = 27). There was no significant difference between the individuals undergoing lead repair or replacement in age (59 +/- 9 vs 60 +/- 12 years), mean left ventricular ejection fraction (40%+/- 18% vs 33%+/- 17%) or age of the lead being repaired or replaced (4.5 +/- 2.0 years vs 5.0 +/- 2.0 years). During follow-up of 44 +/- 23 months, 4 of the repaired leads and 4 of the replaced leads developed new insulation breaks requiring surgical intervention (P = 0.43). In conclusion, in nearly 4 years of follow-up of patients with sensing lead insulation breaks, there was no difference is subsequent lead survival in those with lead repair compared to those with new sensing leads inserted. The strategy of lead repair, when technically feasible, should thus be considered in all patients with sensing abnormalities secondary to insulation breaks.     

Comparison of Subxiphoid and Traditional Approaches for ICD Implantation

We compared clinical and electrophysiological data in 18 patients undergoing ICD implantation via a traditional (median sternotomy or left lateral thoracotomy) with 29 patients with a Subxiphoid approach. Both groups were similar in terms of age, sex, left ventricular ejection fraction, presence of coronary artery disease, and clinical indication for the device. Fifteen patients (83%) with the traditional approach had previous cardiac surgery compared with 6 patients (21%) who had a subxiphoid approach (P < 0.001). Both groups had similar patch R wave and sensing R wave measurements. Patients with the traditional approach had a lower energy for defibrillation than patients with a subxiphoid approach (13.6 ± 6.8 J vs 17.9 ± 4.1) (P < 0.05). Postoperative hospital days were fewer in the subxiphoid group compared with the traditional approaches (9.8 ± 5.3 vs 13.7 ± 7.5 days) but the differences did not reach statistical significance, possibly due to small numbers. The subxiphoid approach appears to be a reasonable alternative approach to the traditional approach in selected patients undergoing ICD implantation.     

ICD Implantation in infants and small children: the extracardiac technique

BACKGROUND: There is no clear methodology for implantation of an internal cardioverter-defibrillator (ICD) in infants and small children. The aim of this study was to assess efficacy and safety of an extracardiac ICD implantation technique in pediatric patients. PATIENTS AND METHODS: An extracardiac ICD system was implanted in eight patients (age: 0.3-8 years; body weight: 4-29 kg). Under fluoroscopic guidance a defibrillator lead was tunneled subcutaneously starting from the anterior axillar line along the course of the 6th rib until almost reaching the vertebral column. After a partial inferior sternotomy, bipolar steroid-eluting sensing and pacing leads were sutured to the atrial wall (n = 2) and to the anterior wall of the right ventricle (n = 8). The ICD device was implanted as "active can" in the upper abdomen. Sensing, pacing, and defibrillation thresholds (DFTs) as well as impedances were verified intraoperatively and 3 months later, respectively. RESULTS: In seven of eight patients, intraoperative DFT between subcutaneous lead and device was <15 J. In the eighth patient ICD implantation was technically not feasible due to a DFT >20 J. During follow-up (mean 14.5 months) appropriate and effective ICD discharges were noted in two patients. DFT remained stable after 3 months in four of six patients retested. A revision was required in one patient due to lead migration and in another patient due to a lead break. CONCLUSIONS: In infants and small children, extracardiac ICD implantation was technically feasible. Experience and follow-up are still limited. The course of the DFT is unknown, facing further growth of the patients.     

Indications for predismissal testing with arrhythmia-induction in patients receiving an implantable cardioverter defibrillator

Arrhythmia induction during implantation of cardioverter defibrillators (ICD) is a standard procedure. However, controversy exists regarding the need for routine arrhythmia induction before discharge from hospital (pre-hospital discharge (PHD) test). In order to reduce the number of tests we identified risk factors that predict relevant ICD malfunction. METHODS AND RESULTS: 965 patients receiving a first device implantation (n=724) or device/system replacement (n=241) between 1998 and 2004 were analysed. During implantation 176 (18%) complications (intraoperative undersensing of induced arrhythmias, unsuccessful arrhythmia-therapy or low DFT safety margin) occurred. Frequent (>4 times) intraoperative lead repositioning due to low sensing values was present in 44 patients (5%). 9% of the patients with first ICD implantation, 21% with device replacement and 27% with system replacement developed complications during PHD testing with arrhythmia induction. Intraoperative complications, although corrected during implantation, were independent risk factors for malfunction during PHD testing (p<0.05). Additional predictors for malfunction were intraoperative lead repositioning (>4 times) and a history of both VF and VT (p<0.05). Patients without intraoperative complications rarely developed malfunction during PHD testing (3.7% first device, 6.25% system replacement). Only in patients undergoing device replacement was a higher risk for failure (13%) evident. No risk factors could be identified for these subgroups. CONCLUSION: Routine arrhythmia induction during PHD is recommended in ICD patients with intraoperative complications, although corrected during implantation, as well as frequent intraoperatives lead repositioning. Patients undergoing device/system replacement uncomplicated implantation are not generally at low risk for device failure.     

Pectoral cardioverter defibrillators: comparison of prepectoral and submuscular implantation techniques

The purpose of this study was to compare the two techniques of pectoral ICD implantation, prepectoral and submuscular, performed by an electrophysiologist in the catheterization laboratory with use of general or local anesthesia in 45 consecutive patients. Over a period of 30 months, we implanted pectoral transvenous ICDs in 43 men and 2 women, aged 59 +/- 12 years, with use of general (n = 20) or local (n = 25) anesthesia in the catheterization laboratory. Patients had coronary (n = 30) or valvular (n = 4) disease, cardiomyopathy (n = 10) or no organic disease (n = 1), a mean left ventricular ejection fraction of 31%, and presented with ventricular tachycardia (n = 40) or fibrillation (n = 5). One-lead ICD systems (18 Endotak, 10 Transvene/8 Sprint, 2 EnGuard) were used in 38 patients, 2-lead (5 Transvene, 1 EnGuard) systems in 6 patients, and 1 atrioventricular lead ICD system in 1 patient. The prepectoral technique was employed in 29 patients with adequate subcutaneous tissue, while the submuscular technique was used in 16 patients who had a thin layer of subcutaneous tissue. The defibrillation threshold averaged 9-10 J in both groups and there were no differences in pace/sense thresholds. All implants were entirely transvenous with no subcutaneous patch. Biphasic ICD devices were employed in all patients. Active or hot can devices were used in 39 patients. There were no complications, operative deaths, or infections. Patients were discharged at a mean of 3 days. All devices functioned well at predis-charge testing. Over 14 +/- 8 months, 20 patients received appropriate device therapy (antitachycardia pacing or shocks). No late complications occurred. One patient died at 3 months of pump failure; there were no sudden deaths. In conclusion, for exclusive pectoral implantation of transvenous ICDs, electrophysiologists should master both prepectoral and submuscular techniques. One can thus avoid potential skin erosion or need for abdominal implantation in patients with a thin layer of subcutaneous tissue. Finally, there are no differences in pacing or defibrillation thresholds between the two techniques.