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Background —The Telectronics Accufix pacing leads were recalled in November 1994 after 2 deaths and 2 nonfatal injuries were reported. This multicenter clinical study (MCS) of patients with Accufix leads was designed to determine the rate of spontaneous injury related to the J retention wire and results of lead extraction. Methods and Results —The MCS included 2589 patients with Accufix atrial pacing leads that were implanted at or who were followed up at 12 medical centers. Patients underwent cinefluoroscopic imaging of their lead every 6 months. The risk of J retention wire fracture was ≈5.6%/y at 5 years and 4.7%/y at 10 years after implantation. The annual risk of protrusion was 1.5%. A total of 40 spontaneous injuries were reported to a worldwide registry (WWR) that included data from 34 672 patients (34 892 Accufix leads), including pericardial tamponade (n=19), pericardial effusion (n=5), atrial perforation (n=3), J retention wire embolization (n=4), and death (n=6). The risk of injury was 0.02%/y (95% CI, 0.0025 to 0.072) in the MCS and 0.048%/y (95% CI, 0.035 to 0.067) in the WWR. A total of 5299 leads (13%) have been extracted worldwide. After recall in the WWR, fatal extraction complications occurred in 0.4% of intravascular procedures (16 of 4023), with life-threatening complications in 0.5% (n=21). Extraction complications increased with implant duration, female sex, and J retention wire protrusion. Conclusions —Accufix pacing leads pose a low, ongoing risk of injury. Extraction is associated with substantially higher risks, and a conservative management approach is indicated for most patients.

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

To the Editor: Device therapy for advanced cardiac failure has created the potential for device interactions and raised a significant clinical consideration before implementation of therapy. Here we present 2 case vignettes where implantation of an approved left ventricular assist device (LVAD)

Background Despite using different electrode positions, "conventional" external DC cardioversion in patients with atrial fibrillation is ineffective in 6%-50% of cases. An alternative when DC cardioversion is not successful is low energy internal cardioversion, which is performed at increased risk. We tested the hypothesis that optimization of electrode pad position under fluoroscopy to encompass as much atrial muscle as possible might improve the success rate of external cardioversion and thus minimize the need for internal cardioversion. Methods Fifteen (9 males, 6 females) patients (age: 54 +/- 15 years, weight: 124 +/- 35 kg) with chronic atrial fibrillation (> 8 weeks) who had undergone unsuccessful conventional external cardioversion entered the study. Repeat conventional external cardioversion with electrodes in standard (right anterior and left posterior) positions was followed by "optimized" external cardioversion by positioning electrodes under fluoroscopy (using metallic markers). In case of failure, internal cardioversion was performed. Results All 15 patients had undergone unsuccessful conventional external cardioversion with 360-J shocks. Eight patients (group A) reverted to sinus rhythm with one or two 360-J shocks using fluoroscopy-guided pad placement (53%). Six of the remaining 7 (86%) patients (group B) had successful internal cardioversion with biphasic shocks (12 +/- 3 J). The body weight and body mass index were statistically lower in group A vs group B (106 +/- 27 vs 145 +/- 33 kg, p = 0.03 and 35 +/- 8 vs 45 +/- 8 kg/m2, P = 0.48, respectively). There was no statistically significant in age, height, body surface area, duration of atrial fibrillation, amiodarone therapy, ejection fraction, or underlying heart disease. Conclusion Unsuccessful external DC cardioversion, in some patients, is in part due to suboptimal conventional positioning of electrode pads that can be improved under fluoroscopic guidance by achieving the best possible vector encompassing the right and left atria. The optimized external cardioversion technique may minimize the need for internal cardioversion, which remains an effective approach when external cardioversion fails.

Antegrade activation of the His-Purkinje system (HPS) results in synchronized activation of the right ventricular (RV) and left ventricular (LV) endocardia forming normal, narrow QRS duration (QRSD). An alteration in septal activation and transseptal conduction time have been reported to be the causes for QRSD widening seen with bundle branch block. However, reduced synchronization of activation of RV and LV endocardia as another potential mechanism for QRSD widening has not been systematically studied. Fifteen consecutive patients underwent radiofrequency ablation (RFA) for treatment of supraventricular tachycardia. After RFA, mean QRSD in normal sinus rhythm was 86 +/- 8 ms with mean HV interval of 40 +/- 5 ms. Right atrial (RA), coronary sinus (CS), simultaneous (S) RA-CS, RV apex (RVA), LV apex (LVA), and SRVA-LVA pacing were performed. Mean QRSD with RA, CS, SRA-CS pacing was similar to normal sinus rhythm (87 +/- 7, 87 +/- 8 and 88 +/- 8 ms respectively). Mean QRSD was significantly longer with SRVA-LVA and either RVA or LVA pacing alone compared to normal sinus rhythm (106 +/- 8, 146 +/- 12 and 157 +/- 13 ms, respectively). However, QRSD was significantly shorter with SRVA-LVA pacing compared to either RVA or LVA pacing alone (P < 0.0001). We conclude that shorter QRSD with SRVA-LVA pacing compared to either RVA or LVA pacing alone is due to elimination of transseptal conduction delay; longer QRSD with SRVA-LVA pacing compared to sinus or atrial paced rhythm is due to reduced synchronization of endocardial activation secondary to ectopic entry of impulses into the HPS network and inability to take advantage of the branching structure of the HPS. Therefore, in addition to transseptal conduction delay, reduced synchronization of endocardial activation is another potential mechanism for QRSD widening.

A patient with an ICD accidentally grasped a power line and was electrocuted. He was unable to release the cable during electrocution though he remained conscious. After receiving a shock from his ICD, the powerline was released. ICD interrogation revealed inappropriate detection of alternating current and delivery of a shock. Language: en

Patients with an equivocal signal averaged electrocardiogram (SAECG) had less heart disease and better prognosis than patients with overtly abnormal SAECGs. An equivocal SAECG should not prompt further invasive diagnostic testing for ventricular tachycardia unless other clinical risk factors are present.

A new pacemaker algorithm designed to automatically verify pacemaker capture and determine pacing threshold by detection of a stimulus evoked potential was studied in 20 patients undergoing permanent pacemaker implantation. To eliminate pacing stimulus afterpotential and detect an evoked response, a hardware feedback circuit and a software template matching algorithm were used to produce a triphasic charge-balanced pacing pulse. After charge balancing the pacing lead, a residual artifact is measured. A capture window is defined as the area integral of the first 24 msec of the evoked depolarization, and a capture threshold as one third the amplitude of the capture window. The maximum allowable residual artifact is one eighth the amplitude of the capture window. Once the stimulus afterpotential is eliminated and the evoked response detected, capture threshold is automatically and continuously determined and the algorithm adds a 0.8-V safety margin to the pacemaker output. This algorithm was run automatically and after simulated loss of capture, produced by manually decreasing pacer output below threshold, in the bipolar (13 patients) and unipolar (20 patients) pacing modes. In each patient loss of capture was immediately detected. The data were consistent (P = NS) between algorithm runs. During unipolar pacing the area integral of the first 24 msec of the evoked response was 412 +/- 137 versus 413 +/- 144 and the residual artifact 5.8 +/- 4.8 versus 8.1 +/- 7.5. The resulting ratio (signal/noise) of the two parameters was 150 +/- 141 versus 145 +/- 181. Automatically determined threshold was 0.69 +/- 0.43 V versus 0.69 +/- 0.42.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine appears to be an important mediator of hypotension and bradycardia in certain subsets of patients with vasodepressor syncope. Adenosine receptor blockade with methylxanthines may hypothetically prevent the vasodepressor spell. We studied the chronotropic, hemodynamic, and cardiac autonomic responses to head-up tilt in patients (mean age 40.7 ±18.1 years) with vasodepressor syncope before and after treatment with oral theophylline. At baseline, hypotension and syncope or near syncope were induced at 11.7±2.3 minutes of 60° head-up tilt in all patients. Cardiac vagal and sympathetic tone showed biphasic and directionally opposite changes during tilt. Repeat tilt during oral theophylline therapy (6-12 mg/kg/day for 14±6 days) did not provoke symptomatic hypotension in 82% of patients, During 10.7±6.1 months of follow-up, seven patients had no recurrence of vasodepressor syncope and seven patients discontinued theophylline because of adverse reactions. Low-dose theophylline prevents tilt-induced vasodepressor syncope and may prevent spontaneous vasodepressor syncope in selected patients who can tolerate theophylline. ( Arch Intern Med . 1991;151:2425-2429)

Objectives This study was undertaken to determine the safety and feasibility of extraction of the Sprint Fidelis (Medtronic, Minneapolis, Minnesota) lead. Background The reported failure rate of the Sprint Fidelis defibrillator lead has increased to a range greater than initially appreciated with emerging evidence of an accelerating rate of fracture. At present, consensus guidelines continue to recommend against prophylactic extraction of the lead, citing major complication rates between 1.4% and 7.3%. However, data regarding the safety and feasibility of extraction of small-diameter, backfilled implantable cardioverter-defibrillator leads such as the Sprint Fidelis are limited. Methods We performed a retrospective cohort study of consecutive patients undergoing extraction of Sprint Fidelis (models 6930, 6931, 6948, 6949) leads at 5 high-volume centers. Patient characteristics, indications for extraction, and use of countertraction sheath (CTS) assistance are reported. The risk of major and minor complications was determined. A multivariable logistic regression model was developed to predict factors associated with the use of CTS assistance. Results Between May 2005 and August 2009, 349 Sprint Fidelis leads were extracted from 348 patients. All leads were removed completely. The average duration of the implanted lead was 27.5 months (range 0.03 to 58.8 months). Approximately one-half of the extracted leads were fractured (49.4%), and 26.5% were extracted prophylactically. The other major indication for extraction was infection (22.8%). Extraction was achieved with simple traction in 49.4% leads; CTS assistance was required in 174 cases (50.6%). In multivariable models, length of time since implantation was directly related to the need for CTS assistance (odds ratio per month since implantation: 1.035; 95% confidence interval: 1.010 to 1.061; p = 0.006). There were no major procedural complications or deaths. Conclusions Extraction of the Sprint Fidelis lead can be performed safely by experienced operators at high-volume centers with a complication rate lower than that reported for older generation leads. However, leads with longer implant durations are associated with the use of CTS assistance. Recommendations regarding prophylactic Sprint Fidelis lead extraction may warrant reconsideration.

To the Editor: Studies have demonstrated equivalent defibrillation efficacy and all-cause mortality in patients with single and dual coil implantable cardioverter-defibrillator (ICD) leads ([1,2][1]). Despite this equivalency, the vast majority of implanted ICD leads are dual coil ([3][2]). The