Optimization of transvenous coil position for active can defibrillation thresholds

INTRODUCTION: Lead systems that include an active pectoral pulse generator are now standard for initial defibrillator implantations. However, the optimal transvenous lead system and coil location for such active can configurations are unknown. The purpose of this study was to evaluate the benefit and optimal position of a superior vena cava (SVC) coil on defibrillation thresholds with an active left pectoral pulse generator and right ventricular coil. METHODS AND RESULTS: This prospective, randomized study was performed on 27 patients. Each subject was evaluated with three lead configurations, with the order of testing randomized. Biphasic shocks were delivered between the right ventricular coil and an active can alone (unipolar), or an active can in common with the proximal coil positioned either at the right atrial/SVC junction (low SVC) or in the left subclavian vein (high SVC). Stored energies at defibrillation threshold were higher for the single-coil, unipolar configuration (11.2 +/- 6.6 J) than for the high (8.9 +/- 4.2 J) or low (8.5 +/- 4.2 J) SVC configurations (P < 0.01). Moreover, 96% of subjects had low (< or = 15 J) thresholds with the SVC coil in either position compared with 81% for the single-coil configuration. Shock impedance (P < 0.001) was increased with the unipolar configuration, whereas peak current was reduced (P < 0.001). CONCLUSION: The addition of a proximal transvenous coil to an active can unipolar lead configuration reduces defibrillation energy requirements. The position of this coil has no significant effect on defibrillation thresholds.     

Effect of an active abdominal pulse generator on defibrillation thresholds with a dual-coil, transvenous ICD lead system

INTRODUCTION: Many patients with implantable cardioverter defibrillators (ICDs) have older lead systems, which are usually not replaced at the time of pulse generator replacement unless a malfunction is noted. Therefore, optimization of defibrillation with these lead systems is clinically important. The objective of this prospective study was to determine if an active abdominal pulse generator (Can) affects chronic defibrillation thresholds (DFTs) with a dual-coil, transvenous ICD lead system. METHODS AND RESULTS: The study population consisted of 39 patients who presented for routine abdominal pulse generator replacement. Each patient underwent two assessments of DFT using a step-down protocol, with the order of testing randomized. The distal right ventricular (RV) coil was the anode for the first phase of the biphasic shocks. The proximal superior vena cava (SVC) coil was the cathode for the Lead Alone configuration (RV --> SVC). For the Active Can configuration, the SVC coil and Can were connected electrically as the cathode (RV --> SVC + Can). The Active Can configuration was associated with a significant decrease in shock impedance (39.5 +/- 5.8 Omega vs. 50.0 +/- 7.6 Omega, P < 0.01) and a significant increase in peak current (8.3 +/- 2.6 A vs. 7.2 +/- 2.4 A, P < 0.01). There was no significant difference in DFT energy (9.0 +/- 4.6 J vs. 9.8 +/- 5.2 J) or leading edge voltage (319 +/- 86 V vs. 315 +/- 83 V). An adequate safety margin for defibrillation (> or =10 J) was present in all patients with both shocking configurations. CONCLUSION: DFTs are similar with the Active Can and Lead Alone configurations when a dual-coil, transvenous lead is used with a left abdominal pulse generator. Since most commercially available ICDs are only available with an active can, our data support the use of an active can device with this lead system for patients who present for routine pulse generator replacement.     

Effect of shock polarity on ventricular defibrillation threshold using a transvenous lead system

Objectives. The purpose of this study was to determine whether the polarity of a monophasic shock used with a transvenous lead system affects the defibrillation threshold.Background. The ability to implant an automatic defibrillator depends on achieving an adequate defibriilation threshold.Methods. A transvenous defibrillation lead with distal and proximal shocking electrodes was used in this study. In 29 consecutive patients, the defibrillation threshold, using a step-down protocol was determined twice in random order: 1) with the distal coil as the anode, and 2) with the polarity reversed. Only the 20 patients in whom an adequate defibrillation threshold could be obtained with the transvenous lead alone were included in this study. These patients were 61 ± 14 years old (mean ± SD) and had a mean ejection fraction of 28 ± 12%.Results. The mean defibrillation threshold was 11.5 ± 5.0 J with the distal coil as the anode versus 16.9 ± 7.7 J with the distal coil as the cathode (p = 0.04). The defibrillation threshold was lower by a mean of 9 ± 7 J with the former configuration in 14 patients and was lower by a mean of 7 ± 6 J with the latter configuration in 3 patients; in 3 patients it was the same with both configurations. Use of a subcutaneous patch was avoided in five patients by utilizing the distal electrode as the anode.Conclusions. Defibrillation thresholds with monophasic shocks are ~30% lower with the distal electrode as the anode. The use of anodal shocks may obviate the need for a subcutaneous patch and allow more frequent implantation of a transvenous lead system.     

Long-term follow-up of transvenous defibrillation leads: high incidence of fracture in coaxial polyurethane lead.

BACKGROUND: As a result of longer follow-up after implantation of cardioverter defibrillators (ICD), fatigue of the leads has become a concern. The aim of this study was to determine the incidence and clinical presentation of ICD lead failures. METHODS AND RESULTS: The study population consisted of 241 patients with 249 ICD leads who underwent implantation of an ICD with a transvenous lead system. After device implantation, the patients were routinely followed up every 4 months. Five lead failures (2.0%) occurred as an oversensing of artifact during the follow-up period (2.6+/-2.1 years); 4 of those 5 patients received inappropriate shocks and 1 case of lead failure was identified in a patient with frequent episodes of non-sustained ventricular fibrillation. In particular, the right ventricular polyurethane transvenous lead in the Medtronic model 6936 failed in 4 (13%) of 31 cases. Percutaneous lead extraction was not available in all cases, so an additional ICD lead was inserted through the same site of the subclavian vein. CONCLUSIONS: Lead failures may occur 5 years after ICD implantation and polyurethane leads have an especially high incidence of failure. However, there were no follow-up parameters observed that predicted lead failures.     

Effect of first-phase polarity of biphasic shocks on defibrillation threshold with a single transvenous lead system

Objectives. The purpose of this study was to determine whether the polarity of the first phase of a biphasic shock affects the defibrillation threshold.

Background. The polarity of a monophasic shock has been shown to affect the defibrillation threshold.

Methods. A transvenous defibrillation lead with distal and proximal shocking electrodes was used in this study. In 15 consecutive patients, the defibrillation threshold was determined twice using a step-down protocol, in random order: with the distal coil as the anode for the initial phase (anodal biphasic shock) and with the polarity reversed (cathodal biphasic shock). The power to detect a 5.0-J difference in this study is 0.96. These patients were 61 ± 11 years old (mean ± SD), and the mean left ventricular ejection fraction was 0.32 ± 0.10.

Results. Mean defibrillation threshold using anodal biphasic shocks was 9.9 ± 4.8 J, compared with 9.5 ± 4.2 J using cathodal biphasic shocks (p = 0.8). In three patients the defibrillation threshold was lower by a mean of 6.3 ± 2.9 J with the former configuration; in three patients the defibrillation threshold was lower by a mean of 6.7 ± 2.5 J with the latter configuration; and in nine patients it was the same. Using the standard cathodal configuration, a defibrillation threshold 10 J was obtained in to 70% of patients, and a subcutaneous patch was not required in any patient.

Conclusions. The polarity of the first phase of a biphasic shock used with a single transvenous lead does not affect the defibrillation threshold.     

Optimization of atrial defibrillation with a dual-coil, active pectoral lead system

INTRODUCTION: Atrial defibrillation can be achieved with standard implantable cardioverter defibrillator (ICD) leads, but the optimal shocking configuration is unknown. The objective of this prospective study was to compare atrial defibrillation thresholds (DFTs) with three shocking configurations that are available with standard ICD leads. METHODS AND RESULTS: This study was a prospective, randomized, paired comparison of shocking configurations on atrial DFTs in 58 patients. The lead system evaluated was a transvenous defibrillation lead with coils in the superior vena cava (SVC) and right ventricular apex (RV) and a left pectoral pulse generator emulator (Can). In the first 33 patients, atrial DFT was measured with the ventricular triad (RV --> SVC + Can) and unipolar (RV --> Can) shocking pathways. In the next 25 patients, atrial DFT was measured with the ventricular triad and the proximal triad (SVC --> RV + Can) configurations. Delivered energy at DFT was significantly lower with the ventricular triad compared to the unipolar configuration (4.7 +/- 3.7 J vs 10.1 +/- 9.5 J, P < 0.001). Peak voltage and shock impedance also were significantly reduced (P < 0.001). There was no significant difference in DFT energy when the ventricular triad and proximal triad shocking configurations were compared (3.6 +/- 3.0 J vs 3.4 +/- 2.9 J for ventricular and proximal triad, respectively, P = NS). Although shock impedance was reduced by 13% with the proximal triad (P < 0.001), this effect was offset by an increased current requirement (10%). CONCLUSION: The ventricular triad is equivalent or superior to other possible shocking pathways for atrial defibrillation afforded by a dual-coil, active pectoral lead system. Because the ventricular triad is also the most efficacious shocking pathway for ventricular defibrillation, this pathway should be preferred for combined atrial and ventricular defibrillators.     

Clinical predictors of atrial defibrillation thresholds with a dual-coil, active pectoral lead system.

OBJECTIVES: The purpose of this study was to identify clinical predictors of atrial defibrillation thresholds (DFTs) with standard implantable cardioverter-defibrillator (ICD) leads. BACKGROUND: Atrial defibrillation can be achieved with active pectoral, dual-coil transvenous ICD lead systems. If clinical predictors of atrial defibrillation efficacy with these lead systems were identified, they could be used to predict which patients may require more complex lead systems for atrial defibrillation, such as a coronary sinus electrode. METHODS: This was a prospective study of 135 consecutive patients undergoing initial ICD implant for standard indications. The lead system evaluated was a transvenous defibrillation lead with coils in the superior vena cava (SVC) and right ventricular apex (RV), and a left pectoral pulse generator emulator (CAN). The shocking pathway was RV-->SVC+CAN. Atrial DFT was measured using a step-up protocol. Clinical and echocardiographic parameters were evaluated as predictors of atrial DFT and multiple linear regression was performed. RESULTS: Mean atrial DFT was 4.6 +/- 3.8 J. Atrial DFT was < or =3 J in 70 patients (52%) and < or = 10 J in 97% of patients. The highest atrial DFT was 20 J (one patient). Left atrial size (r = 0.21, P = .01) and left ventricular end-diastolic diameter (r = 0.19, P = .02) were independent predictors of atrial DFT. However, these two predictors accounted for only 6% of the variability in atrial DFT. CONCLUSIONS: Clinical parameters are of limited use in predicting atrial DFT with a dual-coil, active pectoral ICD lead system. Because the RV--> SVC + CAN shocking pathway provides reliable atrial and ventricular defibrillation, this configuration should be preferred for combined atrial and ventricular ICDs.     

Temporal decline in defibrillation thresholds with an active pectoral lead system

OBJECTIVES: The objective of this study was to characterize temporal changes in defibrillation thresholds (DFTs) after implantation with an active pectoral, dual-coil transvenous lead system. BACKGROUND: Ventricular DFTs rise over time when monophasic waveforms are used with non-thoracotomy lead systems. This effect is attenuated when biphasic waveforms are used with transvenous lead systems; however, significant increases in DFT still occur in a minority of patients. The long-term stability of DFTs with contemporary active pectoral lead systems is unknown. METHODS: This study was a prospective assessment of temporal changes in DFT using a uniform testing algorithm, shock polarity and dual-coil active pectoral lead system. Thresholds were measured at implantation, before discharge and at long-term follow-up (70 +/- 40 weeks) in 50 patients. RESULTS: The DFTs were 9.2 +/- 5.4 J at implantation, 8.3 +/- 5.8 J before discharge and 6.9 +/- 3.6 J at long-term follow-up (p < 0.01 by analysis of variance; p < 0.05 for long-term follow-up vs. at implantation or before discharge). The effect was most marked in a prespecified subgroup with high implant DFTs (> or =15 J). No patient developed an inadequate safety margin (< 9 J) during follow-up. CONCLUSIONS: The DFTs declined significantly after implantation with an active pectoral, dual-coil transvenous lead system, and no clinically significant increases in DFT were observed. Therefore, routine defibrillation testing may not be required during the first two years after implantation with this lead system, in the absence of a change in the cardiac substrate or treatment with antiarrhythmic drugs.     

Comparison of defibrillation efficacy using implantable cardioverter-defibrillator with single- or dual-coil defibrillation leads and active can

INTRODUCTION: The reduction of defibrillation threshold (DFT) in patients treated with an implantable cardioverter-defibrillator increases patients' safety and prolongs ICD battery life. AIM: To evaluate the possibility of reducing the defibrillation threshold in ICDs with an active can and an additional atrial defibrillation coil instead of the typical intracardiac single-coil lead. METHOD: This study involved 138 patients (36 F and 102 M, mean age 54+/-15 years) including 62 subjects with dual-coil defibrillation lead (group A) and 76 ones with single-coil defibrillation lead (group B). No statistically significant differences with respect to age, left ventricular function, main disease or exacerbation of heart failure according to the NYHA functional class were observed between groups. The defibrillation threshold was measured using the DFT+ protocol. RESULTS: No significant differences between groups were identified with respect to pacing and sensing parameters. The comparison of DFT values between the two studied groups revealed significant improvement (by 14% mean) of defibrillation efficacy in group A. In group A, the mean DFT was 9.8+/-4.6 J (3-20 J) and mean defibrillation resistance - 45+/-7 W (32-73 W), whereas in group B: 11.45+/-5.25 J (3-28 J) and 72+/-12.8 W (38-106 W), respectively. In 93% of patients from group A, DFT was below 15 J, in comparison to 81% of patients from group B (p=0.046). The odds ratio of a higher defibrillation threshold (?15 J) in group A vs. group B was 0.3 (95% confidence interval: 0.09-0.98). The DFT reduction associated with modified ICD system use was independent of following clinical parameters: patient age, gender, main disease, end-diastolic left ventricular diameter, left ventricular ejection fraction, NYHA functional class and concomitant treatment with antiarrhythmic agents. CONCLUSIONS: Modification of the electric field during defibrillation, achieved with the use of active-can ICDs with dual-coil defibrillation leads, allows a reduction of DFT by 14%. At the same time, it reduces the risk of a higher (> or =15 J) DFT by three times compared to patients with a standard single-coil defibrillation lead.     

Pacemaker and ICD lead extraction with electrosurgical dissection sheaths and standard transvenous extraction systems: results of a randomized trial.

AIMS: The purpose of this prospective randomized study was to evaluate the safety and efficacy of transvenous pacemaker and implantable cardioverter-defibrillator (ICD) lead extraction with an electrosurgical dissection sheath (EDS) system in a single-centre experience. Methods Over 10 years, 462 patients have undergone transvenous lead extraction in our institution. From these, 120 consecutive patients (with 161 leads) were randomized to either radiofrequency (RF) current supported extraction or standard countertraction lead removal (60 patients in each arm, 96 men and 24 women). The mean age of randomized patients was 62.7 +/- 9.6 years. In 16 patients, we explanted 17 ICD leads. The average time from the date of implantation to the extraction procedure was 73.4 +/- 15.7 months. The most common reason for lead extraction was infection (95.6%). Results The complete extraction of 78 leads (93%) was achieved in the RF group and 56 leads (73%) with the standard transvenous lead extraction system by counter-traction (P < 0.01). Among these leads, we successfully removed nine of 10 ICD leads (90%) in the RF group and only four of seven ICD leads (57%) in the standard group. We also observed a significant reduction in the time taken for the successful removal of pacemaker and ICD leads using the RF system (9.6 +/- 6.2 min versus 21 +/- 9 min, P < 0.01). Partial success was achieved in six patients with the RF system and in 11 with standard sheaths. In those cases where we failed to remove the lead from the body we sent all but one patient to cardiac surgery. Serious complications were associated with the standard system in two patients, both of whom developed septic pulmonary embolization. Serious bleeding occurred in three patients, one with standard and two with the EDS lead extraction system. CONCLUSION: The EDS extraction system is significantly more effective and quicker. However, the standard counter-traction method is still an effective alternative when used in a highly experienced centre.     

Dual-coil vs single-coil active pectoral implantable defibrillator lead systems: defibrillation energy requirements and probability of defibrillation success at multiples of the defibrillation energy requirements.

AIMS: The aim of the study was to compare the defibrillation energy requirements and the probability of successful defibrillation at multiples of the minimum defibrillation energy requirements in active pectoral implantable defibrillators with single- and dual-coil lead systems. METHODS AND RESULTS: Eighty-three consecutive patients undergoing implantation of an active pectoral cardioverter-defibrillator were randomized to receive a dual- or single-coil lead system. Defibrillators of two manufacturers with a fixed tilt biphasic defibrillation waveform were used. Defibrillation energy requirements were determined using a step-down defibrillation testing protocol. According to the randomization protocol, the patients were assigned to three additional consecutive defibrillation attempts during device implantation and during pre-discharge testing of either 1.0, 1.5 or 2.0 times the determined defibrillation energy requirement. Patients presenting defibrillation energy requirements > 15 J were excluded from analysis. Eighty of 83 patients (96%) completed the study protocol. Three patients were excluded due to elevated defibrillation energy requirements. The defibrillation energy requirements in the dual- and single-coil patient groups were 8.0 +/- 3.6 J and 8.4 +/- 3.7 J (ns), respectively. A comparable percentage of study patients showed defibrillation energy requirements <10 J (dual-coil: 88% vs single-coil: 83%). Defibrillation impedance was significantly different (dual-coil: 50 +/- 5.8 Ohm; single-coil: 39.8 +/- 4.2 Ohm). Regarding the probabilities of successful defibrillation, there were no significant differences between the two patient groups. The probabilities of defibrillation at the three multiples of the defibrillation energy requirement using a dual- and single-coil lead system were 82, 89.7 and 93.6 and 77.8, 94.1 and 95.8%, respectively (P=0.88, P=0.42, P=0.62, respectively). CONCLUSIONS: Dual- and single-coil active pectoral defibrillator systems show no difference in defibrillation energy requirements and no difference in the probability of successful defibrillation at multiples of the minimum defibrillation energy requirement. The use of more simplified defibrillator lead systems may contribute to a future lead design focusing on improvement in lead durability.     

Clinical experience with a new transvenous atrial lead

Although systems using atrial pacemakers offer potential clinical advantages for many patients now receiving ventricular devices, atrial systems have been used in less than 1% of the implantations of permanent pacemakers. The unavailability of clinically successful, easily positioned atrial leads is regarded as the most significant factor in the underutilization of atrial pacing systems. A permanent transvenous atrial lead has been developed and has performed well in 16 months of evaluation in 28 patients. Acute thresholds for voltage at a pulse width of 1 msec ranged from 0.40 v to 2.0 v (average, 1.1 v). Acute peak-to-peak amplitudes of the atrial electrogram were notably high, ranging from 2.5 mv to 7.5 mv (average, 5.1 mv) as measured oscilloscopically. Intermittent failure of sensing occurred in three patients during the period immediately after implantations. Spontaneous dislodgment of the lead from the right atrial appendage occurred in two patients. Atrial sensing and pacing functions remained intact in the first case, and no revision was performed. The lead was repositioned in the second patient and has remained in good position. No complications relating to the lead have been noted in the remaining patients.     

Randomized comparison of aspirin and phenprocoumon for prevention of right-sided thromboembolic complications associated with transvenous defibrillation leads

Death due to pulmonary embolism caused by thrombosis formationalong a pacing wire has been reported in patients with antibradycardiapacemakers. The purpose of this prospective and randomized studywas to evaluate the effects of prophylactically assigned aspirin(100 mg per day) or phenprocoumon (a coumarin derivative) onthe incidence of right-sided thromboembolic complications associatedwith transvenous defibrillation leads. Multiplane transoesophageal echocardiography and pulmonary scintigraphywere performed in 62 consecutive patients immediately and 6± 2 months after transvenous defibrillator implantation.Aspirin or phenprocoumon was administered to the patients ina randomized and parallel manner. By means of multiplane transoesophageal echocardiography andpulmonary scintigraphy no thromboembolic events were observedimmediately after transvenous defibrillator implantation. After6 ± 2 months, however, multiplane transoesophageal echocardiographydisclosed thrombi on the transvenous leads in 13 of 62 patients(21%) despite antithrombotic therapy. At the same time, pulmonaryscintigraphy did not reveal any defects compatible with pulmonaryembolism. Although thrombi occurred in only four patients treatedwith phenprocoumon, but in nine patients receiving aspirin,this difference was statistically insignificant. Other variablesassociated with the occurrence of thrombosis formation werenot identified. One fatal intracranial haemorrhage occurredin the phenprocoumon group. These findings suggest that pulmonary embolism was effectivelyprevented, but thrombosis formation associated with transvenousdefibrillation leads occurred in a significant number of patientsdespite antithrombotic therapy. A carefully balanced medicaldecision is required to determine whether the tendency towarda higher prevention of thrombosis formation related to the useof phenprocoumon will actually outweigh the inherent risk ofmajor bleeding events.     

Evaluation of body weight as a predictive factor for transvenous ventricular defibrillation characteristics.

AIMS: To investigate the correlation between body weight and defibrillation threshold (DFT) for transvenous lead systems using a porcine model. METHODS AND RESULTS: Twenty-eight pigs were anaesthetised and DFTs assessed in single and dual coil configurations using a four-reversal binary search method. DFT was correlated with body weight in the RV --> Can and RV --> SVC + Can configurations. A Pearson correlation coefficient and a two-sided p-value were calculated. A positive correlation exists between body weight and DFT in RV --> Can (r=0.66, p<0.000) and RV --> SVC + Can (r=0.44, p=0.018). CONCLUSION: There is a significant correlation between body weight and DFT in swine. This tends to be greater in the two-electrode than in the three-electrode configuration. With these and previous human observations, one may predict a higher DFT in heavy individuals and make appropriate procedural adjustments.