Search

OBJECTIVE. An important application of late gadolinium enhancement (LGE) cardiac MRI is accurate assessment of myocardial scar before ablation. However, this is often limited in patients with cardiac implantable electronic devices (CIEDs) because of metal device-induced artifacts. The purpose of this study was to determine whether a modified wideband inversion recovery (IR) LGE MRI technique decreases artifact volume to allow the assessment of myocardial scar. SUBJECTS AND METHODS. Fifty patients (17 women and 33 men; mean age ± SD, 61 ± 12 years; mean ejection fraction ± SD, 35.9% ± 13.3%) with CIEDs underwent cardiac MRI using conventional and modified wideband IR LGE techniques before ablation. The volume of device-induced artifact was quantified and stratified by tertiles on mild, moderate, and severe. Ordinal logistic regression analysis assessed the association between artifact volume on conventional and wideband images adjusted for patients' demographics. RESULTS. Conventional LGE MRI resulted in device-induced hyperintense artifacts that obscured ventricular segments in 32 of 50 (64%) cases. Wideband LGE MRI significantly reduced severe artifact volume (p < 0.0001) and completely resolved all mild and most moderate artifacts. Overall, wideband techniques resulted in a 56% reduction in total artifact volume for the cohort (p < 0.0001). The wideband LGE MRI sequence minimized artifacts in the most commonly obscured segments on the conventional LGE MRI sequence, with persistent artifacts in seven, eight, and four of 32 cases at the basal anterior, midventricular anterior, and midventricular anteroseptal segments, respectively. CONCLUSION. The modified wideband IR technique completely resolves mild and moderate device-induced hyperintense artifacts and significantly reduces the volume of severe artifact to allow accurate identification of myocardial scar in patients with CIEDs before ablation.

A formal communication process was established and evaluated for the management of patients with cardiac implantable electronic devices (CIEDs) receiving radiation therapy (RT). Methods to estimate dose to the CIED were evaluated for their appropriateness in the management of these patients. A retrospective, institutional review board (IRB) approved study of 69 patients with CIEDs treated with RT between 2005 and 2011 was performed. The treatment sites, techniques, and the estimated doses to the CIEDs were analyzed and compared to estimates from published peripheral dose (PD) data and three treatment planning systems(TPSs) - UMPlan, Eclipse's AAA and Acuros algorithms. When measurements were indicated, radiation doses to the CIEDs ranged from 0.01-5.06 Gy. Total peripheral dose estimates based on publications differed from TLD measurements by an average of 0.94 Gy (0.05-4.49 Gy) and 0.51 Gy (0-2.74 Gy) for CIEDs within 2.5 cm and between 2.5 and 10 cm of the treatment field edge, respectively. Total peripheral dose estimates based on three TPSs differed from measurements by an average of 0.69 Gy (0.02-3.72 Gy) for CIEDs within 2.5 cm of the field edge. Of the 69 patients evaluated in this study, only two with defibrillators experienced a partial reset of their device during treatment. Based on this study, few CIED-related events were observed during RT. The only noted correlation with treatment parameters for these two events was beam energy, as both patients were treated with high-energy photon beams (16 MV). Differences in estimated and measured CIED doses were observed when using published PD data and TPS calculations. As such, we continue to follow conservative guidelines and measure CIED doses when the device is within 10 cm of the field or the estimated dose is greater than 2 Gy for pacemakers or 1 Gy for defibrillators.

Purpose: To assess the effectiveness of the management of patients with cardiac electronic implantable devices (CEIDS) receiving radiotherapy.Method and Materials: In 2005, a formal communication process was established between RadiationOncology and CardiacElectrophysiology (EP) for the management of patients with permanent, implantable cardiac devices receiving radiotherapy. The process requires a pre‐treatment consult with EP. This information is provided to a medical physicist, who works with the primary radiationoncologist and dosimetrist. Based on the estimated dose to the device, EP and RadiationOncology will determine the appropriate oversight required for treatment. To assess the effectiveness of this program, a retrospective analysis of patients with implantable cardiac devices receiving radiotherapy between the years 2005 and 2011 was performed. Results: Sixty‐nine patients with CEIDs (19 implantable cardioverter defibrillators (ICDs) and 50 pacemakers) were treated in RadiationOncology between 2005 and 2011. Patients were treated to a variety of sites, including 21 patients treated to multiple sites. Doses were estimated prior to radiotherapy, and in vivo measurements were obtained for patients near or exceeding our institutional device tolerance (ICDs = 1 Gy and ICPs = 2 Gy), or if the device was less than 10 cm from the edge of a treatment field. Of the patients evaluated, there were only two patients with ICD devices which had a partial reset of diagnostic data during their treatment. There were no major device failures of arrhythmia detection or treatment.Conclusions: Our multi‐disciplinary team has worked together to develop a process to manage the care of patients with permanent implantable cardiac devices. There have been few device events noted in our patient cohort. The team will continue to follow our institutional management methodology to assess the appropriate amount of EP care necessary during radiation therapy. Laura Horwood is on the speakers bureau for Medtronic. Frank Pelosi is on the advisory board for Boston Scientific Corp and St. Jude Medical, is receiving an educational grants from Medtronic, St Jude, Boston Scientific, Biotronik, and a research grants from Medtronic.

Aims Magnetic resonance imaging (MRI) has been reported to be safe in patients with cardiac implantable electronic devices (CIED) provided a specific protocol is followed. The objective of this study was to assess whether this is also true for patients excluded from published protocols. Methods and results A total of 160 MRIs were obtained in 142 consecutive patients with CIEDs [106 patients had an implantable cardioverter defibrillator (ICD) and 36 had a pacemaker implanted] using an adapted, pre-specified protocol. A cardiac MRI was performed in 95 patients, and a spinal/brain MRI was performed in 47 patients. Forty-six patients (32%) had either abandoned leads (n = 10), and/or were pacemaker dependent with an implanted ICD (n = 19), had recently implanted CIEDs (n = 1), and/or had a CIED device with battery depletion (n = 2), and/or a component of the CIED was recalled or on advisory (n = 32). No major complications occurred. Some device parameters changed slightly, but significantly, right after or at 1-week post-MRI without requiring any reprogramming. In one patient with an ICD on advisory, the pacing rate changed inexplicably during one of his two MRIs from 90 to 50 b.p.m. Conclusion Using a pre-specified protocol, cardiac and non-cardiac MRIs were performed in CIED patients with pacemaker dependency, abandoned leads, or depleted batteries without occurrence of major adverse events. Patients with devices on advisory need to be monitored carefully during MRI, especially if they are pacemaker dependent.

More patients who are receiving therapy with a left ventricular assist device (LVAD) also have an implantable cardioverter-defibrillator (ICD). The aim of the present study was to describe the outcomes and device interactions of simultaneous therapy with an ICD and a LVAD. We evaluated 76 patients with class IV heart failure (age 52 + or - 12 years, left ventricular ejection fraction 0.13 + or - 0.05%, 88% men, 61% nonischemic cardiomyopathy) with both an ICD and a LVAD. The median follow-up with both devices was 156 days. A LVAD with a pulsatile and continuous flow pump was used in 53 (70%) and 23 (30%) patients, respectively. Of the 76 patients, 12 (16%) received a total of 54 ICD therapies. Of the ICD therapies, 88% were appropriate. Of the 76 patients, 55 (72%) underwent heart transplantation a median of 146 days after LVAD implantation. Twelve patients (16%) died during simultaneous ICD and LVAD therapy. Interactions between the LVAD and ICD occurred in 2 patients (2.7%) with continuous flow pumps (HeartMate II). In both cases, telemetry failure occurred after LVAD implantation with 2 different models of ICDs from the same manufacturer. No ICD therapies occurred because of device-related interactions. In conclusion, simultaneous ICD and LVAD therapy in patients with severe congestive heart failure is safe and clinically feasible. Interactions between the devices are uncommon and appear limited to specific models of ICDs.

Amiodarone Effect on Defibrillation Energy Requirement. Introduction: The effect of oral amiodarone therapy on defibrillation energy requirements in patients with an implantable defibrillator has not been established. Methods and Results: Twenty-one consecutive patients with implantable biphasic waveform defibrillators underwent a step-down determination of the defibrillation energy requirement 211 ± 12 days before and 73 ± 22 days after initiation of amiodarone therapy (mean total dose 26.7 ± 11.1 g). Serum amiodarone and desethylamiodarone concentrations were measured at the time of defibrillation energy requirement determination. The mean defibrillation energy requirement before amiodarone therapy was 9.9 ± 4.6 J. After initiation of amiodarone therapy, the mean defibrillation energy requirement increased to 13.7 ± 5.6 J (P = 0.004). A linear relationship between the amiodarone (P = 0.02, r = 0.6), desethylamiodarone (P = 0.02, r = 0.6), and combined amiodarone-desethylamiodarone concentrations (P = 0.001, r = 0.6) and the defibrillation energy requirement was noted. Stepwise regression analysis demonstrated that the combined amiodarone-desethylamiodarone concentration was the only independent predictor of increase in the defibrillation energy requirement. Conclusion: Chronic oral amiodarone therapy increases the defibrillation energy requirement by approximately 62% in patients with an implantable defibrillator. The combined amiodarone-desethylamiodarone concentration is directly related to the increase in the defibrillation energy requirement.

The main finding of this prospective, controlled study is that amiodarone and desethylamiodarone plasma concentrations < 1 mg/L are associated with a 23% increase in the acute defibrillation energy requirement and with a 31% increase in the requirement for a subcutaneous patch or array. The defibrillation energy requirement does not correlate with the plasma concentrations of amiodarone, desethylamiodarone, amiodarone plus desethylamiodarone, or with the duration or daily dosage of amiodarone therapy.

Biphasic shocks are believed to be superior to monophasic shocks. Monophasic anodal shocks, as opposed to cathodal shocks, are associated with improved defibrillation energy requirements (DERs). However, it is unclear how the DER of anodal monophasic shocks compare with conventional biphasic shocks. Therefore the purpose of this study was to prospectively compare the DER of an anodal monophasic shock with that of a cathodal biphasic shock. A transvenous defibrillation lead with distal and proximal shocking electrodes was used. The subjects of this study were 20 consecutive patients with a mean age of 64.2 +/- 10.5 years ( +/- SD) and a mean left ventricular ejection fraction of 0.36 +/- 0.18. Six had had cardiac arrest. The DER, defined as the lowest energy that converted ventricular fibrillation to sinus rhythm, was determined twice with a step-down protocol (25 J, 20 J, 15 J, 10 J, 5 J, 3 J, 1 J). If the DER wasor = 25 J, then a subcutaneous patch was deemed necessary for system implantation. In random order the DER was determined with a monophasic anodal shock (distal electrode positive) and then with a cathodal (first phase, distal electrode negative) biphasic shock. The mean DER with anodal monophasic shocks was 15.1 +/- 8.5 J compared with 13.6 +/- 8.1 J with cathodal biphasic shocks (p = 0.4). A DERor = 25 J was present in three patients with the monophasic waveform and in three patients with the biphasic waveform (p = NS). In conclusion, the DER and frequency of subcutaneous patch use with an anodal monophasic waveform is comparable to that obtained with cathodal biphasic waveform.

Coronary revascularization has been suggested as sole therapy for secondary prevention of sudden cardiac arrest associated with ischemia. The use of implantable defibrillators (ICD) in combination with coronary revascularization for this patient population is unclear. Among 412 consecutive patients receiving an ICD, 23 (6%) were identified as sudden cardiac arrest survivors who were noninducible with programmed stimulation and had unstable angina or ischemia on a functional study; they underwent successful coronary revascularization. During a follow-up of 34 ± 18 months, 10 (43%) of the 23 patients received ICD shocks (8 ± 8 per patient, range 1 to 22 shocks), and nine of the 10 patients had syncope/presyncope associated with at least one ICD discharge. Patients with ICD discharges were compared with those without ICD discharges, and no clinical characteristics were statistically different between the two groups. In conclusion, revascularization alone may be inadequate therapy for survivors of sudden cardiac arrest associated with ischemia who are noninducible with programmed stimulation, and clinical variables cannot predict which patients are likely to have recurrent malignant ventricular arrhythmias.

Objectives To determine whether risk for implantable cardioverter-defibrillator (ICD) therapy varies by body mass index (BMI) in systolic heart failure (HF). Background It is unknown whether obesity increases sudden death risk in patients with systolic HF. Methods Secondary analysis of patients with HF, left ventricular ejection fraction ≤0.40 and ICD (N = 464) was performed using Cox regression modeling to assess risk for first delivered ICD therapy, with patients grouped by BMI (kg/m2): normal (18.5 to

BACKGROUND Radiation therapy's (RT's) effects on cardiac implantable electronic devices (CIEDs) such as implantable cardioverter-defibrillators (ICDs) and pacemakers (PMs) are not well established, leading to device removal or relocation in preparation for RT. OBJECTIVE To determine the effect of scattered RT on CIED performance. METHODS We analyzed 69 patients—50 (72%) with PMs and 19 (28%) with ICDs—receiving RT at the University of Michigan. Collected data included device model, anatomic location, and treatment beam energies, treatment type, and estimated dose to the device. Patients were treated with either high-energy (16-MV) and/or low-energy (6 MV) photon beams with or without electron beams (6–16 MeV). The devices were interrogated with pre- and post-RT and/or weekly with either in-treatment or home interrogation, depending on the patient's dependence on the device and the estimated or measured delivered dose. Outcomes analyzed were inappropriate ICD therapies, device malfunctions, or device-related clinical events. RESULTS The PMs were exposed to 84.4±99.7 cGy of radiation, and the ICDs were exposed to 92.1±72.6 cGy of radiation. Two patients with ICDs experienced a partial reset of the ICD with the loss of historic diagnostic data after receiving 123 and 4 cGy, respectively. No device malfunction or premature battery depletion was observed at 6-month follow-up from RT completion. CONCLUSIONS CIED malfunction due to indirect RT exposure is uncommon. Regular in-treatment or home interrogation should be done to detect and treat these events and to ensure that diagnostic data are preserved.

Background: Tachycardia detection in first-generation biventricular pacemaker-implantable cardioverter defibrillators (BiV ICD) occurs through both the right ventricular (RV) and left ventricular (LV) leads, creating the potential for inappropriate detection and therapies. Little is known regarding the prevalence and management of patients with BiV ICDs and inappropriate detection. Methods and Results: A transvenous, first-generation BiV ICD was implanted in 77 consecutive patients (age 61 ± 11 years) for drug-refractory heart failure. The mean New York Heart Association class, QRS duration, and ejection fraction were 3.1 ± 0.4, 168 ± 24 ms, and 0.19 ± 0.07, respectively. Among the 77 patients, 17 (22%) experienced inappropriate detection at a mean of 154 ± 140 days after implantation. Fifteen of the 17 patients (88%) experienced inappropriate ICD therapy. In 16 of the 17 (94%) patients, the cause of inappropriate detection was double counting during sinus (8) or atrial rhythm (3), and nonsustained ventricular tachycardia (5). Despite reprogramming of the ICD, 9 patients (53%) required an additional procedure because of inappropriate therapies, including an upgrade to a dedicated BiV ICD (5), revision of the LV lead (2), ablation of the atrioventricular junction (1), and repeat defibrillation threshold testing (2). Conclusions: Inappropriate detection in patients with a first-generation BiV ICD is common and often results in inappropriate ICD therapy. The most common mechanism of inappropriate detection is double counting that often creates the need for additional procedures. Although devices in which tachycardia detection occurs only through the RV lead now are available, close follow-up of the many patients who received a first-generation BiV ICD is necessary.

Implantable cardioverter-defibrillators (ICDs) with nonthoracotomy lead systems are widely available, and are implanted either in the electrophysiology laboratory or the operating room. The purpose of this study was to prospectively evaluate the safety and efficacy of nonthoracotomy ICD implantation in an electrophysiology laboratory versus an operating room. During a 7-month period, 62 consecutive ICDs with nonthoracotomy lead systems were implanted in patients in an electrophysiology laboratory. During the next 10 months, 110 consecutive ICDs were implanted in patients in a surgical operating room. All ICD implantations were performed under general anesthesia by electrophysiologists. There were no differences in age (58 ± 14 vs 62 ± 12 years , p = 0.06), gender distribution ( p = 0.3), frequency of structural heart disease (97% vs 97%, p = 0.9), ejection fraction (0.31 ± 0.15 vs 0.29 ± 0.13, p = 0.3), or presentation with cardiac arrest (65% vs 53%, p = 0.2) between patients undergoing ICD implantation in the electrophysiology laboratory and operating room, respectively. The rate of successful implantation and of complications for systems implanted in the electrophysiology laboratory (95% and 13%, respectively) and in the operating room (98% and 14%, respectively) were similar ( p = 0.4 and p = 0.8, respectively). Specifically, the rate of infection (0% vs 4%, p = 0.3) and hematoma formation (2% vs 4%, p = 0.8) were not statistically significantly different. Three patients who had undergone ICD implantation in an operating room died within 30 days. ICDs with nonthoracotomy lead systems can be implanted with a similarly high rate of success and acceptable complication rate in the electrophysiology laboratory and in the operating room.

Despite an array of treatment modalities, the overall prognosis for patients with severe heart failure remains bleak. Biventricular pacing, or cardiac resynchronization therapy, is gaining increasing acceptance as a compelling treatment for those individuals with advanced heart failure (New York Heart Association functional class III or IV). This article provides a brief description of the atrial and ventricular conduction disturbances common in patients with advanced heart failure. Current indications for therapy are outlined, as are recent results of cardiac resynchronization therapy trials. The implant procedure is described to provide a comprehensive overview of this innovative approach to re-establishing normal electromechanical activity and synchronous right and left ventricular contractions. Patient care, before and after device implant, is also summarized. The focus on patient education throughout this article may allow it to serve as a reference for health care providers involved in the care of patients with severe heart failure.

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.)

Defibriiiation Energy Requirements. Introduction: Defibrillation energy requirements in patients with nonthoracotomy defibrillators may increase within several months alter implantation. However, the stability of the defibrillation energy requirement beyond I year has not heen reported. The purpose of this study was to characterize the defihrillation energy requirement during 2 years of clinical follow-up. Methods and Results: Thirty-one consecutive patients with u biphasic nonthoracotomy defihrillation system underwent defibrillation energy requirement testing using a step-down technique (20, 15, 12. 10, 8, 6, 5, 4, 3, 2, and I J) during defibrillator implantation, and then 24 hours, 2 months, 1 year, and 2 years after implantation. The mean defihrillation energy requirement during these evaluations was 10.9 ± 5.5 J, 12.3 ± 7.3 J, 11.7 ± 5.6 J, 10.2 ± 4.0 ,|, and 11.7 ± 7.4 J, respectively (P = 0.4). The defibrillation energy requirement was noted to have increased hy 10 J or more after 2 years of follow-up in five patients. In one of these patients, the defihrillation energy requirement was no longer associated with an adequate safety margin, necessitating revision of the defihrillation system. There were no identifiahle clinical characteristics that distinguished patients who did and did not develop a 10-J or more increase in the defihrillation energy requirement. Conclusion: The mean defibrillation energy requirement does not change significantly after 2 years of hiphasic nonthoracotomy detihrillator system implantation. However, approximately 15% of patients develop a 1((-J or greater elevation in the defihrillation energy requirement, and 3% may require a defihrillation system revision. Therefore, a yearly evaluation of the defibrillation euergy requirement may he appropriate. (J Cardiovasc Electrophysiol, Vol. 9, pp. 916-920. Septemtwr 1998)

Implantable cardioverter-defibrillator (ICD) generator replacement due to a depleted battery is a frequently performed procedure. The frequency with which sensing and defibrillation system failures are identified during device replacement procedures has not been previously described. Therefore, the purpose of this study was to prospectively determine the frequency of lead system malfunction detected at the time of device replacement in 55 consecutive patients undergoing ICD generator replacement. The mean age of the patients was 63 +/- 10 years and 40 of them were men. Forty-nine patients had an epicardial lead system, and six patients had a nonthoracotomy lead system. Four [7%] of these 55 patients were noted to have previously undetected lead system failure, either sensing (n = 3) or defibrillation (n = 1), necessitating system revision. The lead systems that failed were 40 +/- 6 months old (33-49 months). In summary, during ICD generator replacement, previously undetected problems with sensing or defibrillation may be identified in approximately 10% of patients. Therefore, a comprehensive evaluation of the sensing and the defibrillation functions should be an essential component of the ICD generator replacement procedure.

The purpose of this study was to determine if the polarity of the first phase of a biphasic shock used with a transvenous lead system affects the defibrillation threshold (DFT). The Endotak (Cardiac Pacemakers, Inc., Model 0074) transvenous defibrillation lead with distal and proximal shocking electrodes was used in this study. In 15 consecutive patients, the DFT was determined twice using a step-down protocol, in random order: with the distal coil as the anode forthe initial phase (anodal biphasic shock), and then with the polarity reversed (cathodal biphasic shock). These patients were 61 ± 11 years old (± standard deviation) and their mean left ventricular ejection fraction was 0.32 ± 0.10. The mean DFT using anodal biphasic shocks was 9.9 ± 4.8 joules, compared to 9.5 ± 4.2 joules using cathodal biphasic shocks (p = 0.8). In 3 patients the DFT was lower by a mean of 6.7 ± 2.9 joules with the former configuration, in 3 patients the DFT was lower by a mean of 6.3 ± 2.5 joules with the latter configuration, and in 9 patients it was the same. Using the standard cathodal configuration, a DFT of 15 joules was obtained in all patients, a DFT of 10 joules or less was obtained in 67% of patients (10/15) and a subcutaneous patch was not required in any patient. The polarity of the first phase of a biphasic shock used with a single transvenous lead does not affect the DFT. With either polarity configuration, a DFT of 10 joules or less is obtainable in approximately 70% of patients, and a subcutaneous patch is rarely, if ever, required.

BACKGROUND Traditional lead systems for implantable cardioverter defibrillators (ICDs) require a thoracotomy for placement. Nonthoracotomy lead systems are available and are usually implanted by an electrophysiologist and a surgeon. The purpose of this study was to prospectively evaluate the safety and efficacy of ICD implantation with a nonthoracotomy lead system by electrophysiologists. METHODS AND RESULTS A consecutive series of 100 patients (mean age, 61 +/- 13 years, +/- SD) underwent ICD implantation with a nonthoracotomy lead system while intubated and under general anesthesia. Seventy-seven patients had coronary artery disease, 15 had idiopathic cardiomyopathy, 6 had miscellaneous heart disease, and 2 had structurally normal hearts. The mean ejection fraction was 0.29 +/- 0.13. Sixty-eight patients had suffered a cardiac arrest, and 32 had had ventricular tachycardia or syncope. All patients except 9 underwent electrophysiological testing and had failed 1 +/- 1 drug trials before ICD implantation. Three types of nonthoracotomy lead systems were used. The nonthoracotomy lead with an ICD was successfully implanted in 96 patients (96%). Of the unsuccessful implants, 1 patient did not have venous access, the passive fixation lead in 1 would not remain lodged, 1 had elevated defibrillation thresholds, and 1 developed a hemopneumothorax while venous access was being obtained. The mean defibrillation threshold was 17 +/- 6 J. The mean procedure duration was 161 +/- 57 minutes. When a subcutaneous patch was used (n = 58), the procedure duration was 189 +/- 5 minutes, and when a subcutaneous patch was not required (n = 40), the procedure lasted 123 +/- 37 minutes (P < .0001). Patients remained in the hospital 4.5 +/- 4.1 days after implantation, with no procedure-related deaths. Acute complications occurred in 10 patients; 2 had lead dislodgments, 1 with previous abdominal surgery had his abdominal cavity entered (without other complications) while the ICD pocket was being made, 1 had postoperative heart failure, 1 developed a large hematoma when anticoagulation therapy was initiated, 3 required reintubation because of excessive anesthesia, 1 developed superficial cellulitis, and 1 developed a hemopneumothorax secondary to a lacerated subclavian vein. During 6 +/- 3 months of follow-up, 2 patients developed lead fractures. CONCLUSIONS (1) Electrophysiologists can implant an ICD with a nonthoracotomy lead system safely and with a high success rate; (2) use of a subcutaneous patch correlates with longer procedure durations; and (3) special precautions should be taken in patients with previous abdominal surgery.

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.

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.

OBJECTIVES The purpose of this study was to determine the outcome of patients with nonischemic dilated cardiomyopathy, unexplained syncope and a negative electrophysiology test who are treated with an implantable defibrillator. BACKGROUND Patients with nonischemic cardiomyopathy and unexplained syncope may be at high risk for sudden cardiac death, and they are sometimes treated with an implantable defibrillator. METHODS This study prospectively determined the outcome of 14 consecutive patients who had a nonischemic cardiomyopathy, unexplained syncope and a negative electrophysiology test and who underwent defibrillator implantation (Syncope Group). Nineteen consecutive patients with a nonischemic cardiomyopathy and a cardiac arrest who were treated with a defibrillator (Arrest Group) served as a control group. RESULTS Seven of 14 patients (50%) in the Syncope Group received appropriate shocks for ventricular arrhythmias during a mean follow-up of 24 ± 13 months, compared with 8 of 19 patients (42%) in the Arrest Group during a mean follow-up of 45 ± 40 months (p = 0.1). The mean duration from device implantation until the first appropriate shock was 32 ± 7 months (95% confidence interval [CI], 18 to 45 months) in the Syncope Group compared to 72 ± 12 months (95% CI, 48 to 96 months) in the Arrest Group (p = 0.1). Among patients who received appropriate shocks, the mean time from defibrillator implantation to the first appropriate shock was 10 ± 14 months in the Syncope Group, compared with 48 ± 47 months in the Arrest Group (p = 0.06). Recurrent syncope was always associated with ventricular tachyarrhythmias. CONCLUSIONS The high incidence of appropriate defibrillator shocks and the association of recurrent syncope with ventricular arrhythmias support the treatment of patients with nonischemic cardiomyopathy, unexplained syncope and a negative electrophysiology test with an implantable defibrillator.

At least a 10J defibrillation safety margin is usually required for implantation of a defibrillator (ICD). While the defibrillation threshold (DFT) with a nonthoracotomy lead (NTL) system is known to rise during the initial 6 months following implantation, revision of the defibrillation system previously has not been reported. For epicardial lead systems, the DFT is thought to be stable. Six patients (pt) were identified with a rise in their chronic DFT resulting in a loss of a 10J DFT safety margin necessitating revision of the lead system. The mean age was 64 ± 10 and 5 pts were men. Four pts had an ischemic and 2 had a nonischemic cardiomyopathy. Two pts had epicardial and 4 pts had NTL systems and each ICD generator delivered monophasic waveform shocks. The acute DFT was determined by a step-down protocol in 5 pts. For these pts, the mean acute DFT was 17.5 ± 3.9J. Elevated DFT's were observed in 4 pts with NTL's during a 2 month post-ICD implantation evaluation of the DFT (2.8 ± 1 month), and in 2 pts with epicardial leads at replacement of the ICD generator for end-of-life battery status (at 36 and 41 months). The chronic DFT was determined by a step-down protocol and was 31.4 ± 3.8J. The integrity of the lead system was evaluated and was intact for each pt. A 10J defibrillation safety margin was achieved in each pt by either placing an additional defibrillating electrode (n = 2). placing an ICD with biphasic shocks (n = 2), or a combination of these two (n = 1). In the 2 pts with epicardial leads, one was managed with placement of a biphasic ICD and the other required placement of a transvenous defibrillating electrode and a biphasic ICD. In the 4 pts with NTL's, 1 required a biphasic lCD, 2 required the addition of epicardial patches and 1 pt refused ICD revision. The mean DFT was 17.0 ± 6.8J acutely after lead revision and, 2 months later, the mean DFT was 16.8 ± 7.5J. This is the first report describing a rise in the chronic DFT-eliminating a 10J DFT safety margin necessitating ICD lead revision for both epicardial and NTL systems. This anecdotal report suggests that routine reevaluation of the chronic DFT is necessary. When loss of the 10J safety margin is demonstrated, management is directed at obtaining an adequate defibrillation safety margin by revising either the lead configuration or the defibrillation waveform.