Transvenous Defibrillation Lead Research Articles

Abstract 17362: A Multidisciplinary Heart Team Approach to High Risk Transvenous Pacemaker and Defibrillator Lead Extraction Improves Mortality

Introduction: There is a risk of serious complications with high-risk lead extraction (LE) that may increase mortality. Current guidelines do not provide definitive guidance on collaborative involvement of cardiac surgery as compared to other procedures such as TAVR procedures. We report a single center experience of the benefits of a collaborative approach between cardiac surgery and cardiac electrophysiology (EP). Hypothesis: MDHT will improve outcomes in LE Methods: High risk lead extractions had dwell times of at least 4 years for pacemaker leads and 2 years for ICD leads. A multidisciplinary heart team (MDHT) was created based on the TAVR model that includes a combined lead management clinic and a monthly multidisciplinary conference. Prior to MDHT creation, high risk lead extractions were performed either in the hybrid operating room (OR) and cardiology procedure lab with a surgeon on call as needed. After the MDHT creation all cases were performed in the hybrid operating room by a cardiac surgeon, cardiac anesthesiologist and EP together with an interventional radiologist readily available. Results: Prior to MDHT, 169 patients underwent 344 leads extractions. There were six major procedural complications (3.6%) that included 2 procedural deaths (1.2%) during that period (SVC tear, Tricuspid valve avulsion). Following the creation of MDHT, there have been 47 cases performed with 85 leads extracted. There have been two complications requiring surgical repair (one SVC laceration, one RV laceration), which were surgically repaired. With the creation of a MDHT, the rate of major complications was unchanged (Pre vs. Post MDHT 3.6% vs. 4.3%) but there was a lower mortality rate (Pre vs. Post MDHT 1.2% vs. 0%). Conclusions: High risk lead extraction had a fixed complication rate at our institution however a MDHT decreased mortality. A structured multidisciplinary approach, involving EP and cardiac surgery, decreased mortality in a medium sized lead extraction center and should be considered at all centers.

Long-term reliability of the defibrillator lead inserted by the extrathoracic subclavian puncture.

BackgroundAs the transvenous defibrillator lead is fragile and its failure may cause a life‐threatening event, reliable insertion techniques are required. While the extrathoracic puncture has been introduced to avoid subclavian crush syndrome, the reports on the long‐term defibrillator lead survival using this approach, especially the comparison with the cephalic cutdown (CD), remain scarce. We aimed to evaluate the long‐term survival of the transvenous defibrillator lead inserted by the extrathoracic subclavian puncture (ESCP) compared with CD.MethodsBetween 1998 and 2011, 324 consecutive patients who underwent an implantable cardioverter‐defibrillator (ICD) implantation in Hokkaido University Hospital were included. ICD leads were inserted by CD from 1998 to 2003 and by contrast venography‐guided ESCP thereafter. Lead failure was defined as a nonphysiologic high‐rate oversensing with abnormal lead impedance or highly elevated sensing and pacing threshold.ResultsOf 324 patients, CD was used in 37 (11%) and ESCP in 287 patients (89%). During the median follow‐up of 6.2 years (IQR:3.2‐8.3), 7 leads (2 in CD and 5 leads in ESCP group) failed. All patients with lead failure in ESCP group were implanted with either SJM Riata (n = 1) or Medtronic Fidelis lead (n = 4). Five‐year lead survival was 93.8% (CI95%:77.3‐98.4%) in CD compared with 99.1% (CI95%:96.6‐99.8%) in ESCP group (P = 0.903). Univariate Cox regression analysis showed that the use of Fidelis or Riata lead was the strong predictor of the ICD lead failure (HR 13.8, CI95%:2.9‐96.5; P = 0.001).ConclusionsContrast venography‐guided extrathoracic puncture ensures the reliable long‐term survival in the transvenous defibrillator leads.

The story of … a lead.

The totally transvenous implantable defibrillator lead, conceived by Mirowski and Mower 45 years ago, is irrevocably related to the wide acceptance of this therapy. It paved the way for the era for non-thoracotomy implantation. This paper covers the most important details of the evolution--over this 45-year period--of the original (ENDOTAK) transvenous ICD lead and subsequent iterations. Over that time period, there have been over 800 000 patients implanted with this family of leads. The 'story' addresses the multiple problems encountered, technological improvements in materials, design, and testing to overcome them. And, the need for continued close collaboration between physicians and industry focused on reliability and longevity of this critical component of these life-saving systems.

Implantable Cardioverter-Defibrillator Leads

The transvenous defibrillation lead was a critical technological step that enabled widespread adoption of implantable cardioverter-defibrillator (ICD) therapy. This lead is the most vulnerable component of the ICD system. It must remain chemically inert in a hostile biological environment, withstand flexing for hundreds of millions of cardiac cycles, and retain electrical integrity during shocks that would trip a household circuit breaker. Reliability issues concerning leads have led to the rethinking of lead design, reexamination of preclinical testing, implementation of algorithms that warn of lead failure and reduce inappropriate shocks, design of leads that can be extracted more easily, and development of a totally subcutaneous ICD system. The present review summarizes clinical aspects of defibrillation leads and reviews diagnostic and therapeutic approaches to lead failure. Please see the online-only Data Supplement for a brief summary of the engineering of lead design. ### Structural Overview Right ventricular (RV) defibrillation leads comprise a distal tip electrode with a fixation mechanism that anchors the lead to the heart, proximal terminals that connect to the generator, and a lead body that connects the two (Figure 1A). The lead body consists of a flexible insulating cylinder with 3 to 6 parallel longitudinal lumens through which conductors run from the proximal terminals to small pace-sense electrodes and larger shock coil electrodes. This multilumen design (Figure 1B) permits more conductors in smaller-diameter leads than older coaxial designs.1 The subcutaneous ICD uses a parasternal electrode in which the larger shock coil is straddled by 2 small sensing electrodes (Figure 1C). Figure 1. Structure of true bipolar leads in which the active fixation screw acts as the distal pace-sense electrode. A , Top , Dual-coil active fixation lead with DF-1/IS-1 terminal pins. Bottom , Single-coil active fixation lead with DF-4 terminal pins. B , Cross section of multilumen, dual-coil, true bipolar lead (Durata, …

How many transvenous coils are optimal for defibrillators: One, two, or none?

This year marks the 20th anniversary of the transvenous defibrillation lead. Until 1993, implantable cardioverter-defibrillator (ICD) implantation required thoracotomy for the placement of epicardial or extrapericardial patches, sometimes with transvenous pace/sense leads or shocking coils. The early transvenous defibrillation leads consisted of sensing electrodes and 2 coils tunneled to an abdominal pulse generator. Adequate defibrillation was often a challenge, but this problem was markedly reduced with 2 major technological advances: biphasic waveforms and downsizing of pulse generators to allow for pectoral implantation using the pulse generator as part of the shock pathway as an active “can.”

Twiddler’s syndrome in an adolescent patient with ICD during neurological and physical rehabilitation

Sirs: A 20-year-old woman was admitted to our hospital by the emergency physician after resuscitation in cardiac arrest due to a ventricular fibrillation (VF) caused by a non-classified cardiomyopathy with a impaired left ventricular function of about 35% and a long QT-syndrome. As a consequence of cerebral hypoxia the patient suffered from an impaired neurological status with cognitive deficit and sensomotoric disability. After 6 weeks of hospitalization good neurological potential was predicted and a single chamber ICD (Guidant/CPI Prizm VR) was implanted for secondary prevention of ventricular fibrillation [4]. The transvenous defibrillation lead (Guidant, Endotak Reliance) was inserted into the right ventricle via the right subclavian vein, since the left side had been affected earlier by a catheter associated thrombosis. The screw-in lead tip was positioned at the lower interventricular septum with a sensing of 12 mV and a pacing threshold of 0.4 V/0.4 ms. The

Response to Letter Regarding Article, “Annual Rate of Transvenous Defibrillation Lead Defects in Cardioverter-Defibrillators Over a Period of >10 Years”

We are thankful to Drs Suri and Keller for their interest in our study.1 Lead defects can have many causes. Therefore, a multilateral approach is needed to reduce the incidence of lead failure. As stated by Drs Suri and Keller, this includes better lead design, improved implantation techniques, and appropriate choice of device. What is also necessary is a detailed analysis …

Letter by Suri and Keller Regarding Article, “Annual Rate of Transvenous Defibrillation Lead Defects in Cardioverter-Defibrillators Over a Period of >10 Years”

To the Editor: The high failure rates of transvenous defibrillation leads in implantable cardioverter-defibrillators reported by Kleemann et al1 are quite disturbing. This article raises many issues about lead design, implantation techniques, and follow-up. First, the electrophysiology community craves leads with small diameters. This preference may have a negative impact on lead durability. Polyurethane, which is used to produce smaller leads, is more likely to degrade prematurely. Kleemann et al make the case for reevaluating the design of smaller leads. Although the poor performance of older leads is concerning, …

Large septic pulmonary embolism complicating extraction of an infected transvenous defibrillator lead

1 A-53-year-old man with known coronary artery disease and a istory of sustained monomorphic ventricular tachycardia underent placement of a dual-chamber implantable cardioverter-defirillator (ICD) in 2003. He presented to an outside facility with ever. His blood cultures were positive for Staphylococcus epiermidis, and the patient subsequently was transferred to our acility for further treatment. On physical examination he apeared well. He was afebrile, and his left infraclavicular ICD ocket was benign. A transthoracic echocardiogram (Figure 1A) evealed a large mobile vegetation (1.5 cm 1.5 cm) localized to he ICD lead within the right ventricle as it coursed through the ricuspid valve. Mild tricuspid regurgitation was present. A transenous endocardial lead extraction was performed using a comination of locking stylet and electrocautery dissection. All imlanted hardware was extracted without evidence of retained lead ragments. Immediately after the procedure, a transthoracic echoardiogram showed no evidence of vegetation within the heart and o change in valvular regurgitation. After the procedure, the paient developed left-sided pleuritic chest pain associated with feer. Computed tomographic scan of the chest confirmed a large ulmonary embolus (Figure 1B, filling defect) confined to the eft lower lobe pulmonary artery with evidence of pulmonary nfarction and consolidation (arrowhead). Intraoperative cultures f the pocket and lead tips were negative for bacterial growth; the atient had been receiving intravenous (IV) antibiotics for a few ays prior to the procedure. The patient was treated with 6 weeks f IV antibiotics and recovered without sequelae. He subsequently nderwent repeat ICD placement. With the ever-increasing number of cardiac pacemaker and CD placement procedures, physicians are likely to encounter ore patients with infected intravascular device hardware. he risk of pulmonary embolism complicating extraction of acemaker and ICD leads associated with vegetations 1 cm n size has been highlighted in the literature. The original bservation regarding the risk of embolization and larger vegtations was reported by Mugge et al, who demonstrated that 2 (47%) of 47 patients with vegetations 1 cm had evidence

Prevalence of central venous occlusion in patients with chronic defibrillator leads

Background Many patients with previously implanted ventricular defibrillators are candidates for an upgrade to a device capable of atrial-ventricular sequential or multisite pacing. The prevalence of venous occlusion after placement of transvenous defibrillator leads is unknown. The purpose of this study was to determine the prevalence of central venous occlusion in asymptomatic patients with chronic transvenous defibrillator leads. Methods Thirty consecutive patients with a transvenous defibrillator lead underwent bilateral contrast venography of the cephalic, axillary, subclavian, and brachiocephalic veins as well as the superior vena cava before an elective defibrillator battery replacement. The mean time between transvenous defibrillator lead implantation and venography was 45 ± 21 months. Sixteen patients had more than 1 lead in the same subclavian vein. No patient had clinical signs of venous occlusion. Results One (3%) patient had a complete occlusion of the subclavian vein, 1 (3%) patient had a 90% subclavian vein stenosis, 2 (7%) patients had a 75% to 89% subclavian stenosis, 11 (37%) patients had a 50% to 74% subclavian stenosis, and 15 (50%) patients had no subclavian stenosis. Conclusions The low prevalence of subclavian vein occlusion or severe stenosis among defibrillator recipients found in this study suggests that the placement of additional transvenous leads in a patient who already has a ventricular defibrillator is feasible in a high percentage of patients (93%). (Am Heart J 2001;141:813-6.)

The mechanisms of the vulnerable window: the role of virtual electrodes and shock polarity

Vulnerability and defibrillation are mechanistically dependent upon shock strength, polarity, and timing. We have recently demonstrated that shock-induced virtual electrode polarization (VEP) may induce reentry. However, it remains unclear how the VEP mechanism may explain the vulnerable window and polarity dependence of vulnerability. We used a potentiometric dye and optical mapping to assess the anterior epicardial electrical activity of Langendorff-perfused rabbit hearts (n = 7) during monophasic shocks (+/-100 V and +/-200 V, duration of 8 ms) applied from a transvenous defibrillation lead at various coupling intervals. Arrhythmias were induced in a coupling interval and shock polarity dependent manner: (i) anodal and cathodal shocks induced arrhythmias in 33.2 +/- 30.1% and 53.1 +/- 39.3% cases (P < 0.01), respectively, and (ii) the vulnerable window was located near the T-wave. Optical maps revealed that VEP was also modulated by the coupling interval and shock polarity. Recovery of excitability produced by negative polarization, known as de-excitation, and the resulting reentry was more readily achieved during the relative refractory period than the absolute refractory period. Furthermore, anodal shocks produced wavefronts propagating in an inward direction with respect to the electrode, whereas cathodal shocks propagated in an outward direction. Wavefronts produced by anodal shocks were more likely to collide and annihilate each other than those caused by cathodal shocks. The probability of degeneration of the VEP-induced phase singularity into a sustained arrhythmia depends upon the gradient of VEP and the direction of the VEP-induced wavefront. The VEP gradient depends upon the coupling interval, while the direction depends upon shock polarity; these factors explain the vulnerable window and polarity-dependence of vulnerability, respectively.

The mechanisms of the vulnerable window: the role of virtual electrodes and shock polarity

Vulnerability and defibrillation are mechanistically dependent upon shock strength, polarity, and timing. We have recently demonstrated that shock-induced virtual electrode polarization (VEP) may induce reentry. However, it remains unclear how the VEP mechanism may explain the vulnerable window and polarity dependence of vulnerability. We used a potentiometric dye and optical mapping to assess the anterior epicardial electrical activity of Langendorff-perfused rabbit hearts (n = 7) during monophasic shocks (+/-100 V and +/-200 V, duration of 8 ms) applied from a transvenous defibrillation lead at various coupling intervals. Arrhythmias were induced in a coupling interval and shock polarity dependent manner: (i) anodal and cathodal shocks induced arrhythmias in 33.2 +/- 30.1% and 53.1 +/- 39.3% cases (P < 0.01), respectively, and (ii) the vulnerable window was located near the T-wave. Optical maps revealed that VEP was also modulated by the coupling interval and shock polarity. Recovery of excitability produced by negative polarization, known as de-excitation, and the resulting reentry was more readily achieved during the relative refractory period than the absolute refractory period. Furthermore, anodal shocks produced wavefronts propagating in an inward direction with respect to the electrode, whereas cathodal shocks propagated in an outward direction. Wavefronts produced by anodal shocks were more likely to collide and annihilate each other than those caused by cathodal shocks. The probability of degeneration of the VEP-induced phase singularity into a sustained arrhythmia depends upon the gradient of VEP and the direction of the VEP-induced wavefront. The VEP gradient depends upon the coupling interval, while the direction depends upon shock polarity; these factors explain the vulnerable window and polarity-dependence of vulnerability, respectively.

Implantable defibrillators impedance measurement using pacing pulses versus shock delivery with intact and modified high voltage lead system.

At present the only method for measuring the high voltage system lead impedance in patients with an ICD is to deliver a low energy test shock. This is painful, requires sedation, and carries a risk of ventricular fibrillation induction. We sought to assess the shock lead and electrode function by calculating IMP using low voltage pacing pulses, and compared it to the measured impedance of a shock through the same lead. This was performed in both an intact and a modified lead system in order to mimic common clinical scenarios that alter lead system IMP (e.g., lead fracture). In an anesthesized canine model (n = 12) a standard (S) transvenous defibrillation lead (TDL), a modified (M) TDL (two-thirds of coil covered with heat-shrunk tubing), an active can (AC), and a M epicardial patch (EP) (two of four coils were disconnected) were used. Three configurations (C) were tested: C1:S/TDL-->AC, C2:M/TDL-->AC, and C3:M/TDL-->MEP. A measured IMP was obtained by an ICD using a 5-J shock as control. IMP was calculated using a 5-J shock, pacing pulses of 10-, 5-, 2-, and 1-V amplitude, as well as from a square wave drive train of low amplitude/high frequency signals (1 and 0.2 V, at 10 kHz) in all Cs. Ohm's law (V = IR) was utilized for measuring calculated IMP. As the surface area of the high voltage lead system decreased, the mean measured IMP (control) increased from C 1 to 3 (63 +/- 10, 95 +/- 4, and 127 +/- 20 omega, respectively). The correlation of calculated IMP from all Cs to measured impedance (control) remained high throughout the IMP range (range of correlation coefficient (r): 0.921-0.981). Calculated IMP using delivery of pacing pulses is highly correlated to IMP measured during shock delivery. This correlation remains high over a clinically significant range of high voltage lead system IMP changes. This study suggests that pacing pulses can be used to predict the IMP changes in the high voltage lead system which may occur clinically, reducing the need to deliver a shock for IMP measurement.

Late complications in patients with pectoral defibrillator implants with transvenous defibrillator lead systems: high incidence of insulation breakdown.

As the majority of ICDs with transvenous leads are now implanted in the pectoral region, complications associated with the technique are being identified. To determine the incidence of lead complications in patients with transvenous defibrillator leads and ICDs implanted in the pectoral region, 132 unselected consecutive patients with transvenous defibrillator leads had ICDs implanted in the pectoral region. Three lead systems were used: (1) lead system 1 (45 patients) consisted of a transvenous pacing sensing lead and a superior vena cava coil with a submuscular patch used for defibrillation; (2) lead system 2 (36 patients) utilized a CPI Endotak lead system; and (3) lead system 3 (51 patients) utilized a Medtronic Transvene lead system. Patients were followed for 3-54 months (cumulative 2,269, mean 18 months). The average duration of follow-up with the three systems was 32, 12 and 11 months, respectively. At 30 months follow-up, all three lead systems had a low incidence of complications. However, there was a 13% overall incidence (45% actuarial incidence) of erosion of the insulation of the pacing sensing lead of system 1 at 50 months of follow-up. All lead complications were seen in patients with ICDs whose weights were > 195 g and volumes > 115 cc. The erosion was probably a consequence of the pressure by the large ICD against the lead in the pectoral pocket. Follow-up with lead systems 2 and 3 is relatively short (average 12 months) but no lead erosions were seen. Pectoral implantation of ICDs with long transvenous leads and large generators is associated with a moderate risk of late complications in the form of insulation breaks caused by pressure of the generator against the leads. The use of less redundant leads coupled with smaller ICDs will probably eliminate this complication.

Effects of respiration phase on ventricular defibrillation threshold in a hot can electrode system.

The impedance of defibrillation pathways is an important determinant of ventricular defibrillation efficacy. The hypothesis in this study was that the respiration phase (end-inspiration versus end-expiration) may alter impedance and/or defibrillation efficacy in a "hot can" electrode system. Defibrillation threshold (DFT) parameters were evaluated at end-expiration and at end-inspiration phases in random order by a biphasic waveform in ten anesthetized pigs (body weight: 19.1 +/- 2.4 kg; heart weight: 97 +/- 10 g). Pigs were intubated with a cuffed endotracheal tube and ventilated through a Drager SAV respirator with tidal volume of 400-500 mL. A transvenous defibrillation lead (6 cm long, 6.5 Fr) was inserted into the right ventricular apex. A titanium can electrode (92-cm2 surface area) was placed in the left pectoral area. The right ventricular lead was the anode for the first phase and the cathode for the second phase. The DFT was determined by a "down-up down-up" protocol. Statistical analysis was performed with a Wilcoxon matched pair test. The median impedance at DFT for expiration and inspiration phases were 37.8 +/- 3.1 omega, and 39.3 +/- 3.6 omega, respectively (P = 0.02). The stored energy at DFT for expiration and inspiration phases were 5.7 +/- 1.9 J and 6.0 +/- 1.0 J, respectively (P = 0.594). Shocks delivered at end-inspiration exhibited a statistically significant increase in electrode impedance in a " hot can" electrode system. The finding that DFT energy was not significantly different at both respiration phases indicates that respiration phase does not significantly affect defibrillation energy requirements.

Twiddler's Syndrome Complicating a Transvenous Defibrillator Lead System

Twiddler's syndrome is a rare complication seen in patients with implanted pacemakers or defibrillators. The condition typically presents with device malfunction and occurs when the patient either consciously or unconsciously twists and rotates the implanted device in its pocket, resulting in torsion and dislodgement of the implanted lead. A case of twiddler's syndrome involving a transvenous defibrillation lead and an abdominally implanted defibrillator is described. This is the first report of this complication with this particular lead. The patient in this report was a middle-aged obese diabetic woman who presented 7 months after defibrillator implantation with device noncapture and intermittent nonsensing. Review of the literature reveals that the majority of patients with this complication are middle-aged obese women with a defibrillator pocket that exceeds the size of the defibrillator. Treatment measures are discussed both for the patient with this complication and for the patient at increased risk for its occurrence.

Effect of failed defibrillation shocks on electrogram amplitude in a nonintegrated transvenous defibrillation lead system

Concern has been raised regarding the ability of a nonthoracotomy integrated lead system to redetect ventricular fibrillation following failed defibrillation shocks due to diminution in postshock intracardiac electrogram amplitude. Whether such a problem could occur with other lead systems is not known, leading to uncertainty regarding a potential ongoing risk of sudden cardiac death in some patients despite implantable cardioverter-defibrillator therapy. To investigate this problem, we measured the amplitude of 10 consecutive ventricular fibrillation endocardial electrograms immediately before and immediately after failed defibrillation shocks in 15 patients at the time of implantation of a nonintegrated, transvenous, pace/sense/defibrillation lead. Overall, mean electrogram amplitude decreased 21%, from 10.7 ± 4.6 mV before to 8.5 ± 4.9 mV immediately after failed defibrillation shocks. The change in electrogram amplitude postshock was directly related to shock energy (r = 0.85, p < 0.0005), but shock waveform had no differential effect. Electrogram amplitude could also increase after failed shocks, particularly following those of low energy. No failures to redetect ventricular fibrillation were found. Thus, intracardiac electrogram amplitude is reduced following failed defibrillation shocks in this nonintegrated lead system, but by an amount less than that previously reported for some integrated lead systems. Our findings reveal that failed low energy defibrillation shocks are likely to result in less diminution in postshock intracardiac electrogram amplitude than high energy shocks, and that the postshock amplitude may even increase after some failed shocks.

927-38 Noninvasive Predictors of Successful Implantation of Transvenous Defibrillator Lead Systems

Successful implantation of transvenous defibrillator lead systems depends on achieving an intraoperative defibrillation threshold (DFT) of ≤ 25 J. Since defibrillation is related to a critical mass of myocardium, we sought to determine whether left ventricular (LV) mass or LV volume could predict successful implantation of a transvenous lead system. 20 echocardiography was therefore performed in 46 pts who underwent implantation of a transvenous lead system. Fifteen pts were excluded because of inadequate 20 images. OFT (J) &gt; 25 (n = 22) OFT (J) ≤ 25(n = 9) P LV Volume (ml) 359 ± 72 263 ± 88 002 LV Mass (g) 229 ± 52 214 ± 51 NS Posterior Wall Thickness (mm) 0.87 ± 0.19 0.94 ± 0.17 NS Septal Thickness (mm) 1.64 ± 2.33 1.17 ± 1.32 NS Enddlastolic LV Diameter (mm) 5.56 ± 1.96 6.14 ± 0.92 NS In addition, age and LV ejection fraction were not significantly different between the 2 groups. All pts with DFT &gt; 25 J but only 28% of pts with DFT ≤ 25 J had an LV volume &gt;275 ml (P &lt; 0.01). All pts with an LV volume &lt; 275 ml had acceptable DFTs. These results suggest that LV volume is an important determinant of successful defibrillation with transvenous lead systems since it may in part determine transmyocardial current density for a given defibrillation shock.

992-108 Redetection of Ventricular Fibrillation after a Failed First Shock in Transvenous Defibrillation Lead Systems

Redetection (RD) of ventricular fibrillation after a failed first shock may be delayed. Although algorithms in individual devices (ICD) differ, criteria for RD are uniformly less stringent than for initial detection of ventricular fibrillation (DET). If failed first shocks have no adverse effect on sensing performance, then the time required for RD should be less than that for DET; that is, the RD time minus DET time (RD-DET) should be consistently &lt;0. The mean RD time (159 RD episodes, 70 pts) was 4.3 ± 2.2 sec. Individual episodes of prolonged RD, defined as &gt; mean + 2SD (&gt;8.7 sec), were also identified. ICD Pts RD-DET (sec) p (RDvsDET) RD &gt; 8.7 sec Cadence-Endotak 60 28 -0.9 ± 3.3 NS 7 Ventak P-Endotak 60 16 1.3 ± 2.6 NS 4 Jewel-Transvene 13 -1.8 ± 0.7 0.0001 0 Cadence-TVL 13 -1.6 ± 0.9 0.0001 0 All Endotak 60 44 -0.1 ± 3.2 NS 11 All other leads 26 -1.7 ± 0.8 ** 0.0001 0 ** RED-DET Endotak 60 vs all other leads p = 0.016 In ICD systems that allowed analysis of the sensed electrogram, prolonged RD episodes consistently demonstrated substantial variation in signal amplitude during post-shock ventricular fibrillation. In ICDs coupled with leads other than the Endotak 60 lead: 1) RED time was significantly &lt; DET time and 2) prolonged RD times were not seen during testing conditions against induced ventricular fibrillation. Although the clinical significance is unclear, these data have important implications for lead design and device programming.

Options in managing the patient with high defibrillation thresholds

The desired defibrillation threshold (DFT) obtained during intraoperative testing of an implantable cardioverter defibrillator (ICD) should be 10 J lower than the maximal energy delivered by the ICD generator. Of the 206 patients undergoing ICD implantation since December 1986, 8 (3.9%) have had initial DFTs with less than the 10-J safety margin using the standard large patch-large patch configuration. Patches were implanted by left thoracotomy in 6 and sternotomy in 1, and 1 had implantation of a transvenous defibrillation lead and subcutaneous patch. Of note, 6 (75%) of the 8 patients with high DFTs had prior open heart operations, half were on a regimen of long-term amiodarone therapy, and the mean left ventricular mass index was quite large but not significantly greater than that of patients with low DFTs. Multiple techniques were tried to improve the DFTs in this group. Satisfactory DFTs were eventually obtained in 7 (88%); the threshold was lowered from a mean of 41.4 ± 3.8 J to 26.9 ± 8.8 J ( p = 0.002). The most effective techniques were addition of a superior vena cava lead attached by a Y connector to one of the large patch leads in some patients and conversion to a biphasic-waveform generator in 2 others. Adding a third epicardial lead did not lower the DFTs. There were no major postoperative complications or deaths attributable to these supplemental procedures. Using these techniques, satisfactory DFTs were obtained in almost all patients with an ICD. Consideration should be given to insertion of a superior vena cava lead at the initial ICD implantation should an unacceptably high DFT be obtained with standard patch configurations. Biphasic-waveform generators and other newer devices may reduce the number of patients who require multiple leads for reliable DFTs.