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PubMed2000

Fractally coated defibrillation electrodes: is an improvement in defibrillation threshold possible?

AIMS: In patients with implantable cardioverter-defibrillators (ICD), the goals of lowering the defibrillation threshold (DFT) can be achieved by means of higher defibrillation safety margins, more rapid charging of capacitors, improved battery longevity, implying smaller devices. Whether an increase in the electrically active surface of ICD leads by fractal coating results in decreased DFTs is unknown. METHODS AND RESULTS: In this prospective randomized cross-over study the defibrillation efficacy of a novel right ventricular endocardial defibrillation electrode fractally coated with iridium was compared with an uncoated but otherwise identical electrode in 30 patients undergoing ICD implantation. In each patient, DFT testing was performed twice according to a binary search protocol introducing the two different electrodes in a random order. The mean DFT was 8.4 +/- 4.1 J with the fractally coated lead and 9.6 +/- 3.6 J using the uncoated lead. The improvement of 1.2 J was statistically not significant (P = 0.11). No differences were observed between the patients with an improved DFT (n =12) and those with an unchanged or worsened DFT (n = 18) concerning age, underlying cardiac disease, NYHA class, or left ventricular ejection fraction, respectively. CONCLUSION: Increasing the electrical surface of defibrillation leads by fractal coating does not lead to a substantial clinically relevant reduction in defibrillation thresholds. Defibrillation impedance is not influenced by the increased electrical surface of the defibrillation lead.

Adult↗
PubMed1997

Effect of the addition of an abdominal hot can cardioverter/defibrillator pulse generator on the defibrillation energy requirements in a single-lead endocardial defibrillation system.

AIMS: The effects of a cardioverter/defibrillator system with an electrically active generator can, applied without recourse to thoracotomy, have not been investigated in the abdominal position in humans. The purpose of this acute clinical study was to evaluate the defibrillation efficacy of an abdominally positioned hot can electrode in connection with a single lead endocardial defibrillation system. PATIENTS AND METHODS: Thirty consecutive patients undergoing implantation of a cardioverter/defibrillator or pulse generator replacement were enrolled in this study Each patient received an integrated, tripolar single-lead system. This was tested using an asymmetrical biphasic defibrillation waveform with constant energy delivery. Defibrillation energy, peak voltage, peak current and impedance were compared between two electrode configurations: (A) in this configuration the distal right ventricular coil was negative and the proximal coil positive; (B) in this configuration the distal right ventricular coil was negative and the proximal coil and the abdominal hot can (65 ccm), as common anode, were positive. Defibrillation threshold testing started at 15 J with stepwise energy reduction (10 J, 8 J, 5 J and 3 J) until defibrillation was ineffective. RESULTS: Compared to the single-lead configuration, the abdominal hot can configuration revealed at 17.5% reduction in defibrillation energy requirements (8.6 J +/- 4.3 J vs 10.43 J +/- 3.9 J; P = 0.041), a 15.7% reduction in peak voltage (308.6 V +/- 63 V vs 365.3 V +/- 68 V; P = 0.003), and a 21.6% reduction in impedance (41.1 omega +/- 6.3 omega vs 52.4 omega +/- 6.6 omega; P < 0.001). Peak current showed a significant increase during hot can testing of 8.2% (7.2 A +/- 1.8 A vs 7.8 A +/- 2.2 A; P = 0.16). CONCLUSION: An abdominally placed hot can pulse generator lowered defibrillation energy requirements in patients with an endocardial defibrillation lead system.

Abdominal Muscles↗
PubMed1997

Polarity reversal improves defibrillation efficacy in patients undergoing transvenous cardioverter defibrillator implantation with biphasic shocks.

The purpose of this study was to determine the influence of polarity reversal on DFT in patients undergoing implantation of nonthoracotomy defibrillators with biphasic shocks. Previous studies have shown higher defibrillation efficacy with using the distal electrode as anode implantation of nonthoracotomy defibrillators and monophasic shocks. However, it is as yet unclear whether biphasic shock defibrillation will also be influenced by polarity reversal. Using a transvenous lead system with a proximal electrode in the superior caval vein and a distal electrode in the RV apex, 27 patients undergoing defibrillator implantation were randomized to DFT testing "initial" (distal electrode = cathode) or "reversed" polarity (distal electrode = anode). Defibrillation energy was reduced stepwise until defibrillation failure occurred. At this point, polarity was switched and testing continued until the lowest energy requirement was determined for both polarities. With reversed polarity, DFT was 11.1 +/- 5.7 J versus 13.3 +/- 5.8 J with polarity (P = 0.033). This means a 17% reduction of the DFT. In 10 patients, the threshold was lower with reversed, whereas in 3 patients it was lower with initial polarity. In conclusion, changing electrode polarity in transvenous implantable defibrillators with biphasic shocks may significantly influence defibrillation energy requirements. Therefore, polarity reversal should always be attempted before considering patch implantation.

Adult↗
PubMed1998

Relationship between the upper limit of vulnerability determined in normal sinus rhythm and the defibrillation threshold in patients with implantable cardioverter defibrillators.

The upper limit of vulnerability is the strength above which ventricular fibrillation is no longer inducible with a shock delivered during the vulnerable phase of the cardiac cycle. It has been demonstrated that the upper limit of vulnerability correlates with the defibrillation threshold in a paced rhythm. The purpose of this study is to evaluate the correlation of the upper limit of vulnerability determined in normal sinus rhythm with the defibrillation threshold using a simplified protocol in patients undergoing placement of an ICD. We studied 28 patients who underwent ICD implantation. CPI generators and Endotak leads were used in all patients. Device-based testing was used to determined the defibrillation threshold and the upper limit of vulnerability. The upper limit of vulnerability was tested with three shocks delivered at 0, 20, and 40 ms before the peak of the T wave during normal sinus rhythm. The defibrillation threshold was determined by a simple step up-down protocol. The upper limit of vulnerability (9.0 +/- 4.5 J) did not significantly differ from the defibrillation threshold (9.9 +/- 4.0 J), P = NS. A close correlation was present, correlation coefficient = 0.75, P < 0.0001. The upper limit of vulnerability was within 5 J of the defibrillation threshold in 27 (96%) of the 28 patients. The upper limit of vulnerability underestimated the defibrillation threshold by 10 J in one patient who had a defibrillation threshold of 15 J. The upper limit of vulnerability determined in normal sinus rhythm correlates significantly with the defibrillation threshold in patients undergoing ICD implantation. The protocol is simple and easily implemented clinically.

Anti-Arrhythmia Agents↗
PubMed1998

Influence of polarity reversal on defibrillation success with biphasic shocks and a transvenous/subcutaneous defibrillator system in a porcine animal model.

Clinical studies show that polarity reversal affects defibrillation success in transvenous monophasic defibrillators. Current devices use biphasic shocks for defibrillation. We investigated in a porcine animal model whether polarity reversal influences defibrillation success with biphasic shocks. In nine anesthetized, ventilated pigs, the defibrillation efficacy of biphasic shocks (14.3 ms and 10.8 ms pulse duration) with "initial polarity" (IP, distal electrode = cathode) and "reversed polarity" (RP, distal electrode = anode) delivered via a transvenous/subcutaneous lead system was compared. Voltage and current of each defibrillating pulse were recorded on an oscilloscope and impedance calculated as voltage divided by current. Cumulative defibrillation success was significantly higher for RP than for IP for both pulse durations (55% vs 44%, P = 0.019) for 14.3 ms (57% vs 45%, P < 0.05) and insignificantly higher for 10.8 ms (52% vs 42%, P = ns). Impedance was significantly lower with RP at the trailing edge of pulse 1 (IP: 44 +/- 8.4 vs RP: 37 +/- 9.3 with 14.3 ms, P < 0.001 and IP: 44 +/- 6.2 vs RP: 41 +/- 7.6 omega with 10.8 ms, P < 0.001) and the leading edge of pulse 2 (IP: 37 +/- 5 vs RP: 35 +/- 4.2 omega with 14.3 ms, P = 0.05 and IP: 37.5 +/- 3.7 vs RP: 36 +/- 5 omega with 10.8 ms, P = 0.02). In conclusion, in this animal model, internal defibrillation using the distal coil as anode results in higher defibrillation efficacy than using the distal coil as cathode. Calculated impedances show different courses throughout the shock pulses suggesting differences in current flow during the shock.

Animals↗
PubMed1998

The cost-effectiveness of automatic implantable cardiac defibrillators: results from MADIT. Multicenter Automatic Defibrillator Implantation Trial.

BACKGROUND: The recently reported Multicenter Automatic Defibrillator Implantation Trial (MADIT) showed improved survival in selected asymptomatic patients with coronary disease and nonsustained ventricular tachycardia. The economic consequences of defibrillator management in this patient population are unknown. METHODS AND RESULTS: Patients were followed up to quantify their use of healthcare services, including hospitalizations, physician visits, medications, laboratory tests, and procedures, during the trial. The costs of these services, including the costs of the defibrillator, were determined in patients randomized to defibrillator and nondefibrillator therapy. Incremental cost-effectiveness ratios were calculated by relating these costs to the increased survival associated with the use of the defibrillator. The average survival for the defibrillator group over a 4-year period was 3.66 years compared with 2.80 years for conventionally treated patients. Accumulated net costs were $97,560 for the defibrillator group compared with $75,980 for individuals treated with medications alone. The resulting incremental cost-effectiveness ratio of $27,000 per life-year saved compares favorably with other cardiac interventions. Sensitivity analyses showed that the incremental cost-effectiveness ratio would be reduced to approximately $23,000 per life-year saved if transvenous defibrillators were used instead of the older devices, which required thoracic surgery for implantation. CONCLUSIONS: An implanted cardiac defibrillator is cost-effective in selected individuals at high risk for ventricular arrhythmias.

Cost-Benefit Analysis↗
PubMed1994

Sotalol in patients with implanted automatic defibrillators: effects on defibrillation and comparison with amiodarone.

OBJECTIVES: Although many patients receiving implanted cardioverter defibrillators receive concomitant antiarrhythmic therapy, the risks and benefits of different agents for such patients are not well understood. It was hypothesized that sotalol, a drug with beta-blocking and class II antiarrhythmic properties would be useful in these patients. DESIGN: Nonrandomized prospective cohort study of the effects of sotalol versus other antiarrhythmic therapy on defibrillation energy requirements. SETTING: Tertiary care referral centre. PATIENTS: Patients referred for management of life threatening ventricular arrhythmia in whom an implanted cardioverter defibrillator was indicated on standard clinical grounds. INTERVENTIONS: Intraoperative testing of defibrillation energy requirements, exercise testing, electrophysiological testing. MAIN RESULTS: Fifteen patients were treated with oral sotalol (173.3 +/- 59.8 mg/day). Sotalol blunted maximal heart rate during treadmill exercise (120.9 +/- 29.9 beats/min). Mean right ventricular effective refractory period increased from 251.7 +/- 21.7 to 276.7 +/- 25.7 ms (P = 0.05). All patients received one large (28 cm2) and one small (14 cm2) epicardial electrode patch. The lowest energy to defibrillate successfully from induced ventricular fibrillation (VF) was 5.9 +/- 3.7 J (median 4.1 J), with all patients defibrillated at 15 J or less. In a concurrent comparison group of 16 similar patients not treated with sotalol (13 on amiodarone and three on beta-blockers), with identical or larger patch size, and identical placement, the lowest successful energy to defibrillate from induced VF was significantly higher (16 +/- 8.8 J) (P < 0.05). Mean cycle length of VF from intracardiac recordings was 232 +/- 37 ms, and was significantly inversely correlated with lowest successful energy (r = 0.61, P < 0.05). CONCLUSIONS: Oral sotalol may be useful in conjunction with an automatic defibrillator; it is associated with low defibrillation energy requirements in humans, and may alter VF.

Administration, Oral↗
PubMed1990

Management of complications associated with a first-generation endocardial defibrillation lead system for implantable cardioverter-defibrillators.

An automatic cardioverter-defibrillator could be implanted using an endocardial defibrillation lead system (consisting of a tripolar defibrillation electrode catheter in conjunction with an epicostal patch electrode) in 9 of 10 patients with sustained ventricular tachycardia or ventricular fibrillation. Six lead system complications were observed during a follow-up period of 51 +/- 36 weeks. Three catheter electrode conductor fractures occurred and manifested as oversensing and subsequent delivery of inappropriate shocks (1 patient), inability to defibrillate during electrophysiologic testing 3 months after implant (1 patient) and sudden cardiac death (1 patient). Asymptomatic patch electrode conductor fractures were detected on a routine chest roentgenogram in 2 patients. Endocardial defibrillation threshold testing performed at the time of implantation resulted in malfunction of a previously implanted permanent pacemaker pulse generator in 1 patient. Catheter and patch electrode replacement procedures were performed in 3 consenting patients under local anesthesia. Endocardial defibrillation thresholds after lead replacement were comparable to those obtained at time of initial implant. Serial clinical, roentgenographic and electrophysiologic evaluation should be included in follow-up procedures for endocardial defibrillation lead systems. Monitoring for deleterious effects of endocardial defibrillation threshold testing on previously implanted pacemaker systems should be performed at the time of implant and during follow-up. Improved lead designs are necessary for long-term use of endocardial defibrillation electrodes, but replacement procedures are feasible without thoracotomy.

Aged↗
PubMed1991

Defibrillation efficacy. Comparison of defibrillation threshold versus dose-response curve determination.

When an automatic defibrillator is implanted, it is essential to determine the efficacy of the defibrillating system accurately, while balancing the need to keep the number of fibrillation episodes to a minimum. Two methods have evolved to assess defibrillation efficacy: 1) the "defibrillation threshold," which requires few ventricular fibrillation episodes, and 2) the "dose-response curve," which requires many ventricular fibrillation episodes and relates percent success to energy. The purpose of this study was to compare these two methods directly. Twenty open-chest anesthetized pigs had triplicate defibrillation threshold determinations. To produce a dose-response curve, six shocks then were delivered at 0.5, 0.75, 1.0, 1.25, 1.5, and 2.0 times the mean defibrillation threshold, in a balanced randomized order, during separate episodes of ventricular fibrillation. The data were fitted by logistic regression, conversions of the logistic regression, and a saturable exponential and nonsaturable growth exponential. A comparison was made of the mean defibrillation threshold and the 50% point on the dose-response curve (ED50) for each model, for each animal. In addition, the reliability of each measure was assessed by comparing the coefficients of variation. There was no statistical difference between the group defibrillation threshold (6.6 +/- 0.5 J) and group ED50 values (ED50 range of the models, 5.7 +/- 1.9 to 7.0 +/- 0.9 J). However, the variability about the defibrillation threshold was less than that of the ED50 values for all mathematical models except the true logistic equation, which was virtually the same.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2004

Is defibrillation testing required for defibrillator implantation?

The assessment of defibrillation (DFT) efficacy has long been the standard of care during defibrillator implantation. To ensure an acceptable DFT safety margin, early defibrillator systems frequently required that the shock polarity and the location, type, or number of electrodes had to be altered. Advances in defibrillator and lead technology have resulted in lower and more consistent DFT thresholds in the range of 10 J, with an infrequent requirement to modify the DFT system. Yet, one can make an argument for and against continuation of DFT testing at the time of defibrillator implantation. The goal of this paper is to address both the data that do support and the data that do not support continuation of DFT testing at the time of device implantation. Scientifically, DFT testing should be abandoned only when prospective evidence demonstrates that defibrillator implantation without testing is as safe and has the same mortality benefits as implantation with testing. The most attractive aspect of eliminating DFT efficacy testing is that more patients may have the opportunity to be treated with this life-saving therapy. Perhaps there are alternative strategies to improve accessibility to defibrillator therapy without possibly eroding its effectiveness. In the end, will lives be saved or lost if we discontinue DFT efficacy testing and lower the barriers to implantable defibrillator therapy?

Defibrillators, Implantable↗
PubMed1996

Atrial defibrillation: can modifications in current implantable cardioverter-defibrillators achieve this?

Atrial fibrillation (AF), the most common arrhythmia resulting in hospital admission, is a major health problem. The limited efficacy of antiarrhythmic drugs to control this rhythm disorder and their potential proarrhythmic risk led to the development of new techniques to ameliorate the treatment of AF. Transvenous atrial defibrillation using endocardial electrodes has been shown to be effective at low energy levels. An implantable atrial defibrillator could be a potentially valuable treatment option for patients with paroxysmal AF that is medically refractory. Research is currently under way to investigate several critical issues concerning this new therapeutic concept: long-term efficacy, safety, patient's tolerance, and an acceptable cost/benefit ratio. It is well known that AF often complicates the use of the implantable cardioverter-defibrillator (ICD) for ventricular tachyarrhythmias. Therefore, it would seem desirable to implement the capability for atrial defibrillation into current ICD systems. It has been shown that atrial defibrillation, using endocardial lead configurations specifically designed for ventricular defibrillation, is feasible at energies well within the capabilities of current ICD technology. Further research is needed to evaluate if some enhancement of the lead configuration in combination with possible advanced technology could reduce the atrial defibrillation threshold to a well tolerated level as a prerequisite for automated atrial defibrillation, in ICD recipients with concomitant paroxysmal AF.

Animals↗
PubMed1997

Influence of patient characteristics in the selection of patients for defibrillator implantation (the AVID Registry). Antiarrhythmics Versus Implantable Defibrillators.

The Antiarrhythmics Versus Implantable Defibrillators (AVID) trial is a prospective, randomized study of treatment for life-threatening ventricular arrhythmias. Patients who are eligible for the main trial but who are not enrolled for any reason are followed in a registry. The objective of the present study was to determine whether there are identifiable patient characteristics among these registry patients that may influence whether a patient is treated with an implantable defibrillator. The 914 patients in the registry were divided into 2 groups according to whether the primary treatment was an implantable defibrillator. The mean age of defibrillator patients was 60 years, compared with 65 years in the nondefibrillator group (p <0.001). Only 11.2% of defibrillator recipients were minorities, whereas the percentage of minorities in the nondefibrillator group was 18.7% (p <0.003). A history of recurrent ventricular fibrillation was more likely in the group treated with defibrillators (8.9% vs 4.4%, p <0.01), whereas a history of atrial fibrillation or diabetes mellitus were both significantly more likely in the nondefibrillator group. Among defibrillator patients, a higher proportion had ventricular fibrillation as the index arrhythmia; patients with ventricular tachycardia were significantly more likely to be treated without devices. In this prospective but nonrandomized cohort of patients treated for life-threatening ventricular arrhythmias, older age, minority status, and comorbidity reduced the chances that a patient would be treated with a defibrillator.

Aged↗
PubMed2002

Measurement of body surface energy leakage of defibrillation shock by an implantable cardioverter defibrillator.

Leakage of electrical current from the body surface during a defibrillation shock delivery by an ICD device was evaluated in 27 patients with life-threatening ventricular tachyarrhythmias. All patients underwent the implantation of the Medtronic Jewel Plus ICD system, and the defibrillation shocks were delivered between the active can implanted in the left subclavicular region and the endocardial lead placed in the right ventricle. At the time of measurement of the effect of electrical energy delivery for defibrillation, the shocks were delivered in a biphasic form at the energy level of 20 or 30 J. During each delivery of the defibrillation shock, the electrical current to the body surface was measured through large skin electrodes (6.2 cm2) that were pasted at the following positions: (1) parallel position: the electrodes were placed at the left shoulder and the right low-chest, and the direction of the electrode vector was parallel to the direction of the defibrillation energy flow, and (2) cross position: the electrodes were placed at the right shoulder and the left low-chest, and the vector of the electrodes was roughly perpendicular to the direction of the energy flow. The energy leakages were measured in 80 defibrillation shocks. The peak leakage current during the shock delivery at energy of 30 J was 48 +/- 26 mA at the parallel position and 19 +/- 15 mA at the cross position (P = 0.0002). The energy leakage at a 30-J shock was 7.4 +/- 7.2 mJ at the parallel position and 1.4 +/- 2.3 mJ at the cross position (P = 0.0002). The actual maximum energy leakage was 105 mA, 29 mJ, and 106 V that appeared at the parallel position. The body surface leakage of the defibrillation energy of the ICD device was evaluated. The power of the energy leakage strongly depended on the angle between the alignment of the recording electrodes and the direction of the energy flow. The highest current leakage to the body surface reached a considerable level, but the energy leakage was small because of the short duration of the defibrillation shock.

Adult↗
PubMed1993

Total pectoral implantation: a new technique for implantation of transvenous defibrillator lead systems and implantable cardioverter defibrillator.

We describe a new approach to total pectoral implantation of cardioverter defibrillators with an endocardial defibrillation lead system. Endocardial lead configuration used was an FDA approved right atrial-superior vena cava defibrillation spring electrode, right ventricular bipolar sensing electrode, and a pectoral patch. Endocardial leads were implanted via a cephalic or an axillary venesection. Pectoral patch was placed in a submuscular position. In case of failure to obtain satisfactory thresholds, a small intercostal thoracotomy was performed via the same skin incision and patch placed over the epicardium instead of submuscular position and used with the right atrial spring electrode. The device was implanted in the pectoral region, submuscularly, over the patch. Sixteen consecutive patients underwent this approach. With a submuscular patch, adequate defibrillation thresholds (< or = 15 joules [J]) were obtained in 14 (87.5%) patients. In the other two, defibrillation thresholds of < or = 15 J were obtained with a epicardial patch. Pectoral implantation of the device was feasible in all 16 patients and none needed repositioning. Average postimplant hospital stay was 5 days. During follow-up period (average 5 months), none of the patients reported any major local symptoms and no problems have been encountered in device interrogation. Thus, total pectoral implantation of the cardioverter defibrillator including the patch, leads, and the device is feasible. Furthermore, in case of failure to obtain adequate defibrillation thresholds with submuscular patch, an epicardial patch can easily be implanted and allows 100% successful defibrillation at energy levels of < or = 15 J with right atrial patch configuration.

Adult↗
PubMed1996

Comparison of a unipolar defibrillation system with a dual lead system using an enlarged defibrillation anode.

The unipolar system for transvenous defibrillation, consisting of a single right ventricular lead as the cathode and the device shell as anode, has been shown to combine low defibrillation thresholds (DFTs) and simple implantation techniques. We compared the defibrillation efficacy of this system with the defibrillation efficacy of a dual lead system with a 12-cm long defibrillation anode placed in the left subclavian vein. The data of 38 consecutive patients were retrospectively analyzed. The implantation of an active can system was attempted in 20 patients (group 1), and of the dual lead system in 18 patients (group 2). Both groups had comparable demographic data, cardiac disease, ventricular function, or clinical arrhythmia. The criterion for successful implantation was a DFT of < or = 24 J. This criterion was met in all 18 patients of group 2. The active can system could not be inserted in 3 of the 20 group 1 patients because of a DFT > 24 J. In these patients, the implantation of one (n = 2) or two (n = 1) additional transvenous leads was necessary to achieve a DFT < or = 24 J. The DFTs of the 17 successfully implanted group 1 patients were not significantly different from the 18 patients in group 2 (12.3 +/- 5.7 J vs 10.8 +/- 4.8 J). The defibrillation impedance was similar in both groups (50.1 +/- 6.1 omega vs 48.9 +/- 5.2 omega). In group 1, both operation duration (66.8 +/- 17 min vs 80.8 +/- 11 min; P < 0.05) and fluoroscopy time (3.3 +/- 2.1 min vs 5.7 +/- 2.9 min; P < 0.05) were significantly shorter. Thus, the active can system allows reliable transvenous defibrillation and a marked reduction of operation duration and fluoroscopy time. The dual lead system, with an increased surface area defibrillation anode, seems to be a promising alternative for active can failures.

Defibrillators, Implantable↗
PubMed1998

Effect of a single element subcutaneous array electrode added to a transvenous electrode configuration on the defibrillation field and the defibrillation threshold.

Even with the use of biphasic shocks, up to 5% of patients need an additional subcutaneous lead to obtain a defibrillation safety margin of at least 10 J. The number of patients requiring additional subcutaneous leads may even increase, because recent generation devices have a < 34 J maximum output in order to decrease their size. In 20 consecutive patients, a single element subcutaneous array lead was implanted in addition to a transvenous lead system consisting of a right ventricular (RV) and a vena cava superior lead using a single infraclavicular incision. The RV lead acted as the cathode; the subcutaneous lead and the lead in the subclavian vein acted as the anode. The biphasic defibrillation threshold was determined using a binary search protocol. Patients were randomized as to whether to start them with the transvenous lead configuration or the combination of the transvenous lead and the subcutaneous lead. In addition, a simplified assessment of the defibrillation field was performed by determining the interelectrode area for the transvenous lead only and the transvenous lead in combination with the subcutaneous lead from a biplane chest X ray. The intraoperative defibrillation threshold was reconfirmed after 1 week, after 3 months, and after 12 months. The mean defibrillation threshold with the additional subcutaneous lead was significantly (P = 0.0001) lower (5.7 +/- 2.9 J) than for the transvenous lead system (9.5 +/- 4.6 J). With the subcutaneous lead, the impedance of the high voltage circuit decreased from 48.9 +/- 7.4 omega to 39.2 +/- 5.0 omega. In the frontal plane, the interelectrode area increased by 11.3% +/- 5.5% (P < 0.0001) and in the lateral plane by 29.5% +/- 12.4% (P < 0.0001). The defibrillation threshold did not increase during follow-up. Complications with the subcutaneous electrode were not observed during a follow-up of 15.8 +/- 2 months. The single finger array lead is useful in order to lower the defibrillation threshold and can be used in order to lower the defibrillation threshold.

Aged↗