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Background: A systematic evaluation of patients with unexplained cardiac arrest (UCA) yields a diagnosis in 50% of the cases. However, evolution of clinical phenotype, identification of new disease-causing mutations, and description of new syndromes may revise the diagnosis., Objective: To assess the evolution in diagnosis among patients with initially UCA., Methods: Diagnoses were reviewed for all patients with UCA recruited from the Cardiac Arrest Survivors with Preserved Ejection Fraction Registry with at least 1 year of follow-up., Results: After comprehensive investigation of 68 patients (age 45.2 ± 14.9 years; 63% men), the initial diagnosis was as follows: idiopathic ventricular fibrillation (n = 34 [50%]), a primary arrhythmic disorder (n = 21 [31%]), and an occult structural cause (n = 13 [19%]). Patients were followed for 30 ± 17 months, during which time the diagnosis changed in 12 (18%) patients. A specific diagnosis emerged for 7 patients (21%) with an initial diagnosis of idiopathic ventricular fibrillation. A structural cardiomyopathy evolved in 2 patients with an initial diagnosis of primary electrical disorder, while the specific structural cardiomyopathy was revised for 1 patient. Two patients with an initial diagnosis of a primary arrhythmic disorder were subsequently considered to have a different primary arrhythmic disorder. A follow-up resting electrocardiogram was the test that most frequently changed the diagnosis (67% of the cases), followed by genetic testing (17%)., Conclusions: The reevaluation of patients presenting with UCA may lead to a change in diagnosis in up to 20%. This emphasizes the need to actively monitor the phenotype and also has implications for the treatment of these patients and the screening of their relatives., (© 2014 Heart Rhythm Society Published by Heart Rhythm Society All rights reserved.)

Background: Approximately 10% of patients who undergo surgical procedures require chronic oral anticoagulation. Physicians must balance the thromboembolic and bleeding risks to make informed decisions on whether to continue anticoagulant medication. Evidence is lacking regarding the perioperative management of novel oral anticoagulant (NOAC) agents. This survey aims to describe the management of perioperative NOAC use during device implantation by Canadian centres., Methods: A Web-based tool was used to survey all Canadian adult pacemaker/defibrillator implant centres. The survey collected data regarding the perioperative management of NOACs in atrial fibrillation patients at high risk for thromboembolism who undergo device implantation., Results: Twenty-two centres performed approximately 14,971 device implants; 1150 (8%) of these implants were in patients who were prescribed a NOAC. In 82% of centres, the NOAC is discontinued in anticipation of device implantation; 73% of these centres do not bridge with heparin. In patients with normal renal function at high risk of thromboembolic events (Congestive Heart Failure, Hypertension, Age, Diabetes, Stroke/Transient Ischemic Attack; CHADS2 ≥ 2), 72% of the centres restart the NOAC within 48 hours of the procedure. For patients with abnormal renal function (glomerular filtration rate < 80 mL/min), the timing of NOAC discontinuation is variable. Hematoma rates vary from 0 to 30%., Conclusions: Most Canadian centres perform device implantation with NOAC interruption without the use of bridging. The timing of stopping and restarting anticoagulation and incidence of bleeding complications is variable. These findings emphasize the need for randomized controlled studies to guide the optimal approach to management of NOACs during device implantation., (Copyright © 2014 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Background: The impact of QRS morphology and duration on the effectiveness of cardiac resynchronization therapy (CRT) has been usually assessed separately. The interaction between these 2 simple ECG parameters and their effect on CRT has not been systematically assessed in a large-scale clinical trial., Methods and Results: The Resynchronization-Defibrillation for Ambulatory Heart Failure Trial showed that implantable cardioverter defibrillator-CRT was associated with a significant reduction in the primary end point of all-cause mortality or heart failure hospitalization. For this substudy, we excluded patients in atrial fibrillation and those with a previous pacemaker. All baseline ECGs were reviewed by a panel of 3 experienced electrocardiographers. A total of 1483 patients were included in this study. Of these, 1175 had left bundle-branch block (LBBB) and 308 had non-LBBB. In patients with LBBB receiving implantable cardioverter defibrillator-CRT, there was a reduction in the primary outcome and in each individual component of the primary outcome. Furthermore, there was continuous relationship between QRS duration and extent of benefit. In patients with non-LBBB and QRS ≥160 ms, the hazard ratio for the primary outcome was 0.52 (0.29-0.96; P=0.033); in patients with QRS <160 ms, the hazard ratio was 1.38 (0.88-2.14; P=0.155)., Conclusions: In patients with LBBB, there was a continuous relationship between broader QRS and greater benefit from implantable cardioverter defibrillator-CRT. However, our data do not support the use of implantable cardioverter defibrillator-CRT in patients with non-LBBB, especially when the QRS duration is <160 ms. There may be some delayed benefit when the QRS is ≥160 ms, but this needs further investigation., Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00251251.

Recent studies have provided the impetus to update the recommendations for cardiac resynchronization therapy (CRT). This article provides guidance on the implementation of CRT and is intended to serve as a framework for the implementation of CRT within the Canadian health care system and beyond. These guidelines were developed through a critical evaluation of the existing literature, and expert consensus. The panel unanimously adopted each recommendation. The 9 recommendations relate to patient selection in the presence of comorbidities, delivery and optimization of CRT, and resources required to deliver this therapy. The strength of evidence was weighed, taking full consideration of any risk of bias, and any imprecision, inconsistency, and indirectness of the available data. The strength of each recommendation and the quality of evidence were adjudicated. Trade-offs between desirable and undesirable consequences of alternative management strategies were considered, as were values, preferences, and resource availability. These guidelines were externally reviewed by experts, modified based on those reviews, and will be updated as new knowledge is acquired., (Copyright © 2013 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Background: There are no published clinical consensus guidelines or systematic evaluation supporting the use of corticosteroids for the treatment of cardiac sarcoidosis. The purpose of this study was to systematically review the published data on corticosteroid treatment of cardiac sarcoidosis., Methods: Studies were identified from MEDLINE, EMBASE, Cochrane Controlled Trials Register, Cochrane Database of Systematic Reviews, and National Institutes of Health Clinical Trials.gov database. The quality of included articles was rated using Scottish Intercollegiate Guidelines Network 50. Outcomes examined were atrioventricular (AV) conduction, left ventricular function, ventricular arrhythmias, and mortality., Results: A total of 1491 references were retrieved and 10 publications met the inclusion criteria. There were no randomized trials and all publications were of poor to fair quality. In the 10 reports, 257 patients received corticosteroids and 42 patients did not. There were 57 patients with AV conduction disease treated with corticosteroids, with 27/57 (47.4%) improving. In contrast, 16 patients were not treated with corticosteroids and 0/16 improved. Four publications reported on left ventricular function recovery, 2 reported on ventricular arrhythmia burden, and 9 reported on mortality. However, the data quality were too limited to draw conclusions for any of these outcomes., Conclusions: Our systematic review identified 10 publications reporting outcomes after corticosteroid therapy. The best data relates to AV conduction recovery and corticosteroids appeared to be beneficial. It is not possible to draw clear conclusions about the utility of corticosteroids for the other outcomes. There is a clear need for large multicentre prospective registries and trials in this patient population., (Copyright © 2013 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Background: Positron emission tomography using (18)F-Fluorodeoxyglucose (FDG) is an emerging modality for diagnosis of cardiac sarcoidosis (CS). We compared the location and degree of FDG uptake in CS patients presenting with either advanced atrioventricular block (AVB) or ventricular tachycardia (VT)., Methods and Results: We included consecutive patients who presented with either AVB or VT with a diagnosis of CS. A cohort of patients with clinically silent CS was included as controls. FDG activity was quantified as standardized uptake values (SUV) and both the overall mean left ventricular (LV) SUV as well as the Maximum Mean Segmental SUV was recorded for each patient. Receiver operator characteristic (ROC) analysis was performed to identify cutoff SUV values that best identified patients with VT. A total of 27 patients with CS were included (13 females; mean age, 56 ± 8 years; 8 VT, 12 AVB, and 7 controls). Both mean LV SUV and Max SUV in CS patients presenting with VT were significantly higher compared with those with AVB (mean SUV: VT median 5.33, range 4.7-9.35 versus AVB median 2.48, range 0.86-8.59, P=0.016; max SUV: VT median 11.07, range 9.24-14.4 versus AVB median 5.63, range 3.42-15.71, P=0.005) and compared with controls. There was no significant difference in SUV values between AVB patients and controls. ROC analysis for identification of patients with VT showed AUCs of 0.93 and 0.895 for a mean LV SUV of >3.42 and a max SUV >8.56, respectively (P<0.001)., Conclusions: CS patients with VT displayed significantly higher FDG uptake when compared with those with AVB and asymptomatic controls. Further prospective studies are required to evaluate this finding.

Diagnosing isolated cardiac sarcoidosis can be challenging, and requires a high index of suspicion. We report a case of a young woman who presented with sustained ventricular tachycardia, intermittent atrioventricular block and epsilon wave on electrocardiogram. Although the patient fulfilled Task Force criteria for arrhythmogenic right ventricular cardiomyopathy, sarcoidosis was suspected because of the presence of intermittent atrioventricular block. As illustrated in this report, the use of electroanatomic mapping-guided endomyocardial biopsy can be decisive in achieving the diagnosis and is a valuable approach in cases of suspected isolated cardiac sarcoidosis., (Copyright © 2013 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Randomized clinical trials are a major advance in clinical research methodology. However, there are myriad important questions about the effectiveness of treatments used in daily practice that are not informed by the results of randomized trials. This is in part because of important limitations inherent in the methodology of randomized efficacy trials which are performed with tight control of inclusion, exclusion, treatment, and follow-up. This approach enhances evaluation of clinical efficacy (performance in controlled situations) but increases complexity and is not well suited to test clinical effectiveness (performance under conditions of actual use). The cluster crossover trial is a new concept for efficient comparative effectiveness testing. Deep tissue infection occurs in 2% of patients after arrhythmia device implantation, usually requires system extraction, and increases mortality. There is variation in antibiotic prophylaxis used to reduce implanted device infections. To efficiently evaluate the comparative effectiveness of antibiotic strategies now in use, we designed a cluster crossover clinical trial, which randomized implanting centres to 1 of 2 prophylactic antibiotic strategies, which became the standard care at the centre for 6 months, followed by crossover to the other strategy, rerandomization, and second crossover. This method greatly reduces trial complexity because it aligns study procedures with usual clinical care and increases generalizability. Pilot studies have tested the feasibility and an 10,800-patient trial, funded by the Canadian Institutes of Health Research, is now under way. The cluster crossover randomized trial design is well suited to efficiently test comparative effectiveness of existing treatments where there is variability of practice, clinical equipoise, and minimal risk., (Copyright © 2013 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Background: Many patients requiring pacemaker or implantable cardioverter-defibrillator (ICD) surgery are taking warfarin. For patients at high risk for thromboembolic events, guidelines recommend bridging therapy with heparin; however, case series suggest that it may be safe to perform surgery without interrupting warfarin treatment. There have been few results from clinical trials to support the safety and efficacy of this approach., Methods: We randomly assigned patients with an annual risk of thromboembolic events of 5% or more to continued warfarin treatment or to bridging therapy with heparin. The primary outcome was clinically significant device-pocket hematoma, which was defined as device-pocket hematoma that necessitated prolonged hospitalization, interruption of anticoagulation therapy, or further surgery (e.g., hematoma evacuation)., Results: The data and safety monitoring board recommended termination of the trial after the second prespecified interim analysis. Clinically significant device-pocket hematoma occurred in 12 of 343 patients (3.5%) in the continued-warfarin group, as compared with 54 of 338 (16.0%) in the heparin-bridging group (relative risk, 0.19; 95% confidence interval, 0.10 to 0.36; P<0.001). Major surgical and thromboembolic complications were rare and did not differ significantly between the study groups. They included one episode of cardiac tamponade and one myocardial infarction in the heparin-bridging group and one stroke and one transient ischemic attack in the continued-warfarin group., Conclusions: As compared with bridging therapy with heparin, a strategy of continued warfarin treatment at the time of pacemaker or ICD surgery markedly reduced the incidence of clinically significant device-pocket hematoma. (Funded by the Canadian Institutes of Health Research and the Ministry of Health and Long-Term Care of Ontario; BRUISE CONTROL ClinicalTrials.gov number, NCT00800137.).

Ventricular fibrillation (VF) commonly ends in death. Isolated case reports describe the uncommon occurrence of spontaneous termination of VF. Torsades de pointes (TdP), a peculiar form of polymorphic ventricular tachycardia associated with a prolonged QT interval on the surface electrocardiogram, most often spontaneously terminates and then returns to the underlying rhythm. Here, we present an unusual case of TdP degenerating into VF, reorganizing into TdP, and then spontaneously terminating. Our case suggests that the mechanisms underlying the maintenance of TdP and VF are not dissimilar. The precipitants to this event and the likely mechanisms operative are discussed., (©2012, The Authors. Journal compilation ©2012 Wiley Periodicals, Inc.)

Recent landmark trials provided the impetus to update the recommendations for cardiac resynchronization therapy (CRT). This article provides guidance on the prescription of CRT within the confines of published data. A future article will explore the implementation of these guidelines. These guidelines are intended to serve as a framework for the prescription of CRT within the Canadian health care system and beyond. They were developed through a critical evaluation of the existing literature, and expert consensus. The panel unanimously adopted each recommendation. The 8 recommendations relate to ensuring the adequacy of medical therapy before the initiation of CRT, the use of symptom severity to select candidates for CRT, differing recommendations based on the presence or absence of sinus rhythm, the presence of left bundle branch block vs other conduction patterns, and QRS duration. The use of CRT in the setting of chronic right ventricular pacing, left ventricular lead placement, and the routine assessment of dyssynchrony to guide the prescription of CRT are also included. The strength of evidence was weighed, taking full consideration of any risks of bias, as well as any imprecision, inconsistency, and indirectness of the available data. The strength of each recommendation and the quality of evidence were adjudicated. Trade-offs between desirable and undesirable consequences of alternative management strategies were considered, as were values, preferences, and resource availability. These guidelines were externally reviewed by experts, modified based on those reviews, and will be updated as new knowledge is acquired., (Copyright © 2013 Canadian Cardiovascular Society. All rights reserved.)

Sudden cardiac death is the leading cause of mortality in adults with complex congenital heart disease. Challenges to implanting cardioverter-defibrillators (ICDs) may arise as a result of vascular or intracardiac access issues. For example, conduits may divert systemic venous return to extracardiac structures such as pulmonary arteries or tunnels. Creative approaches to ICD implantation have previously involved subcutaneous arrays, often associated with thoracotomy to implant intrathoracic coils. We describe a patient with complex congenital heart disease and no transvenous access via the superior vena cava in whom ICD implantation involved placement of a coil within the azygos vein., (Copyright © 2013 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Introduction: The need to perform defibrillation testing (DT) at the time of implantable cardioverter defibrillator (ICD) insertion is controversial. In the absence of randomized trials, some regions now perform more than half of ICD implants without DT., Methods: During the last year of enrolment in the Resynchronization for Ambulatory Heart Failure Trial, a substudy randomized patients to ICD implantation with versus without DT., Results: Among 252 patients screened, 145 were enrolled; 75 randomized to DT and 70 to no DT. Patients were similar in terms of age (65.9 ± 9.3 years vs 67.9 ± 8.9 years); LVEF (24.7 ± 4.6% vs 23.6 ± 4.6%), QRS width (154.8 ± 23.5 vs 155.8 ± 23.6 ms), and history of atrial fibrillation (5% vs 6%). All 68 patients in the DT arm tested according to the protocol achieved a successful DT (≤25 J); 96% without requiring any system modification. No patient experienced perioperative stroke, myocardial infarction, heart failure (HF), intubation or unplanned ICU stay. The length of hospital stay was not prolonged in the DT group: 20.2 ± 26.3 hours versus 21.3 ± 23.0 hours, P = 0.79. One patient in the DT arm had a failed appropriate shock and no patient suffered an arrhythmic death. The composite of HF hospitalization or all-cause mortality occurred in 10% of patients in the no-DT arm and 19% of patients in the DT arm (HR = 0.53, 95% CI: 0.21-1.31, P = 0.14)., Conclusions: In this randomized trial, perioperative complications, failed appropriate shocks, and arrhythmic death were all uncommon regardless of DT. There was a nonsignificant increase in the risk of death or HF hospitalization with DT., (© 2012 Wiley Periodicals, Inc.)

Background: Current guidelines recommend bridging anticoagulation in patients undergoing cardiac rhythm device surgery with a "moderate to high risk" of thromboembolism. Patients at "low risk" are advised to stop oral anticoagulation without bridging to the procedure. This study examines real world adherence to accepted guidelines and the clinical sequelae of nonadherence., Methods: We performed a review of all patients undergoing device surgery receiving chronic anticoagulation over a prespecified time period of 14 months. Patients were classified per American College of Chest Physician guidelines as "moderate/high risk" or "low risk" of thromboembolism. We then compared perioperative management of anticoagulation to guideline recommendations and assessed the rate of perioperative bleeding and thromboembolism., Results: One hundred and twenty-nine patients were included in this study. Sixty-two (48%) were classified as "moderate/high risk" and 67 (52%) "low risk." In the "moderate/high risk" group 47/62 (76%) received perioperative anticoagulation but only 25/62 (40%) were bridged both pre- and postprocedure or maintained on uninterrupted warfarin. In the "low risk" group, 22/67 (33%) received bridging therapy. Device pocket hematoma or perioperative bleeding occurred in 10/129 (8%) with 4/10 receiving inappropriate bridging for a calculated low risk of thromboembolism. There were no perioperative thromboembolisms., Conclusions: Our study identified significant underutilization of bridging, particularly in the postoperative period, in patients at "moderate/high risk" of thromboembolism. Conversely, bridging was overused in "low risk" patients and associated with bleeding complications. Physicians should be urged to follow current expert guidelines in regard to bridging anticoagulation for cardiac rhythm device surgery. (PACE 2012;35:1480-1486)., (©2012, The Authors. Journal compilation ©2012 Wiley Periodicals, Inc.)

Background: Cardiac resynchronization (CRT) prolongs survival in patients with systolic heart failure and QRS prolongation. However, most trials excluded patients with permanent atrial fibrillation., Methods and Results: The Resynchronization for Ambulatory Heart Failure Trial (RAFT) randomized patients to an implantable cardioverter defibrillator (ICD) or ICD+CRT, stratified by the presence of permanent atrial fibrillation. Patients with permanent atrial fibrillation were randomized to CRT-ICD (n=114) or ICD (n=115). Patients receiving a CRT-ICD were similar to those receiving an ICD: age (71.6±7.3 versus 70.4±7.7 years), left ventricular ejection fraction (22.9±5.3% versus 22.3±5.1%), and QRS duration (151.0±23.6 versus 153.4±24.7 ms). There was no difference in the primary outcome of death or heart failure hospitalization between those assigned to CRT-ICD versus ICD (hazard ratio, 0.96; 95% CI, 0.65-1.41; P=0.82). Cardiovascular death was similar between treatment arms (hazard ratio, 0.97; 95% CI, 0.55-1.71; P=0.91); however, there was a trend for fewer heart failure hospitalizations with CRT-ICD (hazard ratio, 0.58; 95% CI, 0.38-1.01; P=0.052). The change in 6-minute hall walk duration between baseline and 12 months was not different between treatment arms (CRT-ICD: 19±84 m versus ICD: 16±76 m; P=0.88). Patients treated with CRT-ICD showed a trend for a greater improvement in Minnesota Living with Heart Failure score between baseline and 6 months (CRT-ICD: 41±21 to 31±21; ICD: 33±20 to 28±20; P=0.057)., Conclusions: Patients with permanent atrial fibrillation who are otherwise CRT candidates appear to gain minimal benefit from CRT-ICD compared with a standard ICD.

Background: Following recent cases of nonphysiologic noise noted early after defibrillator implantation, the Canadian Heart Rhythm Society Device Committee decided to evaluate the implications of this problem., Objective: To determine the incidence and consequences of nonphysiologic noise early after defibrillator implantation., Methods: The Canadian Heart Rhythm Society Device Committee surveyed all Canadian defibrillator implanting centers regarding their implant volumes and number of cases where nonphysiologic noise had been noted early (< 24 hours) after implant over the preceding 2 years. For such cases, information regarding the manufacturer and occurrence of inappropriate shock or inhibition of pacing was reported., Results: Responses were obtained from 20 of 23 surveyed implanting centers, with a total implant volume of 4960 defibrillators per year. The occurrence of nonphysiologic noise early after implantation was noted in 25 cases over the preceding 2 years (0.25%). Noise was detected in devices of all 3 of the leading volume device manufacturers. There were 2 cases of inappropriate shocks and 2 cases of symptomatic pacing inhibition. In 4 cases, removal of the lead from the header and retesting with the analyzer confirmed normal lead function. In all cases, the noise resolved within 24 hours., Conclusion: Nonphysiologic noise early after defibrillator implantation was noted in 0.25% of procedures and was not limited to one specific manufacturer. This noise may result in an inappropriate shock or inhibition of pacing in a pacemaker-dependent patient. This transient phenomenon, possibly related to fluid and/or air in the header, appears to always resolve without surgical intervention., (Copyright © 2012 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Warning symptoms may provide an opportunity to diagnose genetic disorders leading to preventative therapy. We explored the symptom history of patients with apparently unexplained cardiac arrest to determine the frequency of sentinel symptoms., Methods: Patients with apparently unexplained cardiac arrest and no evident cardiac disease underwent systematic clinical evaluation. Patients and first-degree relatives were interviewed to determine the presence of cardiac symptoms, and those with syncope underwent 2 structured Calgary Syncope Score questionnaires to determine the probable mechanism of syncope., Results: One hundred consecutive cardiac arrest patients (age 43.0 ± 13.4 years, 60% male) and 63 first-degree relatives (age 37.6 ± 16.3 years, 54% female) were enrolled. Previous cardiac symptoms were present in 69% of cardiac arrest patients compared to 43% of family members (P = 0.001). Prior syncope was present in 26% of cardiac arrest patients, compared to 22% of family members (P = 0.59). Twenty-four of 25 cardiac arrest patients who completed the syncope questionnaires had a syncope versus seizure score <1 favoring syncope. The area under the receiver operator curve (ROC) for the syncope mechanism score was 0.79 for identifying patients with subsequent cardiac arrest (95% CI, 0.6328-0.9395, P = 0.004). A score of ≤-2 had a sensitivity of 68% and specificity of 85%. Thirty percent of patients with a proven genetic cause had preceding syncope versus 19% in patients with noninherited or idiopathic causes (P = 0.032)., Conclusions: Syncope that may represent a sentinel event is present in a modest proportion of patients and family members, and is often suggestive of an arrhythmia., (© 2011 Wiley Periodicals, Inc.)

Objectives: We evaluated the prevalence and characteristics of early repolarization in patients in CASPER (Cardiac Arrest Survivors With Preserved Ejection Fraction Registry)., Background: Early repolarization has been implicated in a syndrome of polymorphic ventricular tachycardia and fibrillation in patients without organic heart disease., Methods: One hundred patients with apparently unexplained cardiac arrest and preserved ejection fraction underwent extensive clinical and genetic testing to unmask subclinical electrical or structural disease. A blinded independent analysis of the 12-lead electrocardiogram (ECG) was performed. Early repolarization was defined as ≥0.1 mV QRS-ST junction (J-point) elevation with terminal QRS slurring or notching in at least 2 contiguous inferior and/or lateral leads., Results: One hundred cardiac arrest patients were enrolled (40 females, age 43 ± 14 years). Forty-four were diagnosed with an established cause for cardiac arrest. Significant early repolarization was found in 19 patients, including 6 with a primary diagnosis that explained their cardiac arrest (14%), compared with 23% of the 56 patients with idiopathic ventricular fibrillation (IVF) (p = 0.23). J-point elevation in IVF patients had higher amplitude (0.25 ± 0.11 mV vs. 0.13 ± 0.05 mV, p = 0.02) and wider distribution (4.3 ± 1.3 leads vs. 2.8 ± 0.8 leads; p = 0.01) than those with an established cause of cardiac arrest. J-wave amplitude was fluctuant on serial ECGs; at least 1 ECG failed to demonstrate early repolarization in 58% of patients., Conclusions: Early repolarization is present in a significant proportion of causally diagnosed and idiopathic VF. It is often intermittent and more pronounced in IVF patients. (Registry of Unexplained Cardiac Arrest; NCT00292032)., (Copyright © 2011 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Whether patients with right bundle branch block (RBBB) benefit from cardiac resynchronization therapy (CRT) is unclear., Objective: The purpose of this study was to systematically review the published data from randomized clinical trials of CRT on the outcomes in patients with baseline RBBB., Methods: Randomized controlled trials of CRT in heart failure and left ventricular systolic dysfunction were identified from MEDLINE (1950-2010), EMBASE (1980-2010, week 45), Cochrane Controlled Trials Register (2009), Cochrane Database of Systematic Reviews, National Institutes of Health Clinical Trials.gov database., Results: A total of 112 references were retrieved. Four publications from five studies reported data on patients with RBBB and were included in this investigation, with 259 patients randomized to CRT and 226 randomized to non-CRT. None of the available data showed more favorable outcomes (soft or hard) in patients with CRT., Conclusion: None of the available data showed more favorable outcomes with CRT in patients with RBBB. A meta-analysis of RBBB patients from the major CRT trials is urgently needed. Results of the meta-analysis can direct further research, perhaps indicating a need for randomized trials in RBBB. Physicians and patients should be aware of the likely reduced benefit form CRT in patients with RBBB, and this should be factored into decision making. However, until more data are available it is too early to change guidelines., (Copyright © 2011 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is characterized by adrenergically induced ventricular tachycardia (VT) associated with syncope and sudden death., Objective: This study sought to characterize arrhythmias associated with CPVT with respect to provocation by exercise and drugs, electrocardiographic characteristics, and association with long-term outcomes; and to explore the relation between age and clinical presentation., Methods: Seventy patients from 16 families were evaluated with exercise and selective adrenaline challenge, and screened for RyR2 mutations. CPVT was diagnosed in probands with symptoms and stress- or adrenaline-provoked VT, or in asymptomatic relatives with provoked VT or RyR2 mutations. Patients were followed up for recurrent syncope, VT, and sudden death., Results: Twenty-seven patients including 16 probands were identified (median age 35 years, 67% female). Presentation was cardiac arrest in 33% and syncope in 56%, and 11% were asymptomatic. Polymorphic or bidirectional VT was provoked with exercise in 63% and adrenaline in 82%. The initiating beat of VT was late-coupled and wide (coupling interval 418 ± 42 ms; QRSd 131 ± 17 ms), and QRS morphology suggested an outflow tract origin in 59%. During follow-up of 6.2 ± 5.7 years, 2 patients died despite an implantable cardioverter-defibrillator (ICD), 4 patients received ICD therapy for VT, and 5 patients had inappropriate therapy for supraventricular tachycardia. Patients presenting with late-onset CPVT (age > 21; n = 10) were often female (80%) and less likely to have RyR2 (Ryanodine receptor type 2) mutations (33%), and fatal events were not observed during follow-up (4.1 ± 3.6 years)., Conclusion: Ventricular arrhythmia in CPVT is often initiated from the outflow tract region. Despite β-blocker therapy and selective ICD implantation, breakthrough arrhythmias occur and may be associated with adverse outcomes., (Copyright © 2011. Published by Elsevier Inc.)

Unlabelled: Psychological Adjustment and Fidelis ICD Leads. , Introduction: Implantable cardioverter defibrillators (ICD) advisory notices present treatment dilemmas for physicians and patients. On one side, the risk of device malfunction and the likely severity of clinical sequelae have to be estimated. This estimate has to be weighed against the risks of surgery to replace the advisory component. It is unclear whether there is important psychological morbidity associated with living with an ICD under advisory and whether this should be factored into decision making. The study had 2 objectives: (1) to examine whether there is adverse psychological adjustment when an ICD is under advisory, and (2) to assess the psychological sequel of advisory ICD component malfunction., Methods: This study focused on the Sprint Fidelis advisory. All patients in our practice who still had an in service Medtronic Fidelis lead were included in the study. Three groups were compared: advisory group but no fracture (n = 249), advisory group with lead fracture (n = 24), and a control group (n = 143). For both objectives, we used a general anxiety and depression instrument and also device-specific measures of psychological well being., Results and Conclusions: First, there was no evidence of differences in the psychological functioning of patients at risk of ICD lead malfunction compared to a control group. Second, patients who had experienced an ICD lead fracture had adverse psychological morbidity compared to control patients, and this appeared, primarily, to be related to receiving inappropriate shock(s) at the time of the fracture., (© 2010 Wiley Periodicals, Inc.)

Background: Cardiac-resynchronization therapy (CRT) benefits patients with left ventricular systolic dysfunction and a wide QRS complex. Most of these patients are candidates for an implantable cardioverter-defibrillator (ICD). We evaluated whether adding CRT to an ICD and optimal medical therapy might reduce mortality and morbidity among such patients., Methods: We randomly assigned patients with New York Heart Association (NYHA) class II or III heart failure, a left ventricular ejection fraction of 30% or less, and an intrinsic QRS duration of 120 msec or more or a paced QRS duration of 200 msec or more to receive either an ICD alone or an ICD plus CRT. The primary outcome was death from any cause or hospitalization for heart failure., Results: We followed 1798 patients for a mean of 40 months. The primary outcome occurred in 297 of 894 patients (33.2%) in the ICD-CRT group and 364 of 904 patients (40.3%) in the ICD group (hazard ratio in the ICD-CRT group, 0.75; 95% confidence interval [CI], 0.64 to 0.87; P<0.001). In the ICD-CRT group, 186 patients died, as compared with 236 in the ICD group (hazard ratio, 0.75; 95% CI, 0.62 to 0.91; P = 0.003), and 174 patients were hospitalized for heart failure, as compared with 236 in the ICD group (hazard ratio, 0.68; 95% CI, 0.56 to 0.83; P<0.001). However, at 30 days after device implantation, adverse events had occurred in 124 patients in the ICD-CRT group, as compared with 58 in the ICD group (P<0.001)., Conclusions: Among patients with NYHA class II or III heart failure, a wide QRS complex, and left ventricular systolic dysfunction, the addition of CRT to an ICD reduced rates of death and hospitalization for heart failure. This improvement was accompanied by more adverse events. (Funded by the Canadian Institutes of Health Research and Medtronic of Canada; ClinicalTrials.gov number, NCT00251251.).

Background: increasingly, ICD implantation is performed without defibrillation testing (DT)., Objectives: To determine the current frequency of DT, the risks associated with DT, and to understand how physicians select patients to have DT., Methods: between January 2007 and July 2008, all patients in Ontario, Canada who received an ICD were enrolled in this prospective registry., Results: a total of 2,173 patients were included; 58% had new ICD implants for primary prevention, 25% for secondary prevention, and 17% had pulse generator replacement. DT was carried out at the time of ICD implantation or predischarge in 65%, 67%, and 24% of primary, secondary, and replacement cases respectively (P = <0.0001). The multivariate predictors of a decision to conduct DT included: new ICD implant (OR = 13.9, P < 0.0001), dilated cardiomyopathy (OR = 1.8, P < 0.0001), amiodarone use (OR = 1.5, P = 0.004), and LVEF > 20% (OR = 1.3, P = 0.05). A history of atrial fibrillation (OR = 0.58, P = 0.0001) or oral anticoagulant use (OR = 0.75, P = 0.03) was associated with a lower likelihood of having DT. Age, gender, NYHA class, and history of stroke or TIA did not predict DT. Perioperative complications, including death, myocardial infarction, stroke, tamponade, pneumothorax, heart failure, infection, wound hematoma, and lead dislodgement, were similar among patients with (8.7%) and without (8.3%) DT (P = 0.7), Conclusions: DT is performed in two-thirds of new ICD implants but only one-quarter of ICD replacements. Physicians favored performance of DT in patients who are at lower risk of DT-related complications and in those receiving amiodarone. DT was not associated with an increased risk of perioperative complications.

Aims: Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, is an important cause of morbidity and mortality. A genetic mutation in the NPPA gene, which encodes the atrial natriuretic peptide, has been identified as the putative causative factor in a family with an autosomal dominant pattern of inheritance for AF. Two common single nucleotide polymorphisms (SNPs) in NPPA, rs5063 and rs5065, result in amino acid changes of the primary peptide and have been previously implicated in conditions associated with AF, including stroke and hypertension. Recently, the rs5063 SNP has been reported to confer an increased risk of AF development in a Chinese population. We sought to examine the associations of both rs5063 and rs5065 with AF in two separate North American cohorts of European ancestry., Methods and Results: Patients with early-onset AF, along with healthy controls, were recruited at the University of Ottawa Heart Institute (UOHI) and the Massachusetts General Hospital (MGH). Study participants were genotyped for rs5063 and rs5065 using a combination of restriction fragment length polymorphism analysis and DNA microarrays. The study genotyped a total of 620 AF cases and 2446 healthy controls. The UOHI arm of the study identified an odds ratio (OR) of 0.72 [95% confidence interval (CI): 0.42-1.24] for rs5063, whereas an OR of 1.33 (95% CI: 0.80-2.21) was observed in the MGH arm. The combined OR approximated unity (OR 0.99; 95% CI: 0.54-1.80). Analysis of rs5065 revealed an OR of 1.12 (95% CI: 0.84-1.48) in UOHI, 1.08 (95% CI 0.80-1.45) in MGH, and 1.10 (95% CI 0.90-1.35) when combined., Conclusion: Common non-synonymous genetic variants within NPPA in these two large North American cohorts of European ancestry are not associated with the development of AF.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an arrhythmogenic disease that manifests as syncope or sudden death during high adrenergic tone in the absence of structural heart defects. It is primarily caused by mutations in the cardiac ryanodine receptor (RyR2). The mechanism by which these mutations cause arrhythmia remains controversial, with discrepant findings related to the role of the RyR2 binding protein FKBP12.6. The purpose of this study was to characterize a novel RyR2 mutation identified in a kindred with clinically diagnosed CPVT. Single-strand conformational polymorphism analysis and direct DNA sequencing were used to screen the RyR2 gene for mutations. Site-directed mutagenesis was employed to introduce the mutation into the mouse RyR2 cDNA. The impact of the mutation on the interaction between RyR2 and a 12.6 kDa FK506 binding protein (FKBP12.6) was determined by immunoprecipitation and immunoblotting and its effect on RyR2 function was characterized by single cell Ca(2+) imaging and [(3)H]ryanodine binding. A novel CPVT mutation, E189D, was identified. The E189D mutation does not alter the affinity of the channel for FKBP12.6, but it increases the propensity for store-overload-induced Ca(2+) release (SOICR). Furthermore, the E189D mutation enhances the basal channel activity of RyR2 and its sensitivity to activation by caffeine. The E189D RyR2 mutation is causative for CPVT and functionally increases the propensity for SOICR without altering the affinity for FKBP12.6. These observations strengthen the notion that enhanced SOICR, but not altered FKBP12.6 binding, is a common mechanism by which RyR2 mutations cause arrhythmias.

Introduction: The Sprint Fidelis 6949 implantable cardioverter defibrillator (ICD; Medtronic Inc., Minneapolis, MN, USA) lead has a high rate of fracture. Identification of predictors of subsequent fracture is useful in decision making about lead replacement and for future lead design. We sought to determine if there are clinical, procedural, or radiological features associated with a greater risk of subsequent lead fracture., Methods: Patients with Sprint Fidelis 6949 lead fractures (Fracture group) were identified from our institutional database. Each patient in the Fracture group was matched to two controls, immediately preceeding and succeeding Sprint Fidelis 6949 implant. Clinical and procedural characteristics were compared. Chest radiographs performed 2 weeks after ICD implant were reviewed by an observer blinded to outcomes. The following features were assessed: ICD tip location, lead slack, kinking of the lead body (> or =90 degrees ), and presence of lead "crimping" within the anchoring sleeve., Results: Twenty-six patients with Sprint Fidelis 6949 lead fractures were identified and were matched to 52 control patients. On univariate analysis, a higher left ventricular ejection fraction (LVEF), prior ipsilateral device implant, history of prior ICD lead fracture, and noncephalic venous access were associated with risk of lead fracture. On multivariate analysis, a higher LVEF was the only independent predictor of lead fracture (P = 0.006). Radiological features were similar between the two groups., Conclusions: In this study, a higher LVEF was associated with a greater risk of lead fracture in patients with Sprint Fidelis 6949 ICD leads. Radiographic features did not predict subsequent risk of lead fracture in our population. (PACE 2010; 437-443).

Background: There is uncertainty about the proper role of defibrillation testing (DT) at the time of implantable cardioverter defibrillator (ICD) insertion., Methods: A prospective registry was conducted at 13 sites in Canada between January 2006 and October 2007., Objectives: To document the details of DT, the reasons for not conducting DT, and the costs and complications associated with DT., Results: DT was conducted at implantation in 230 of 361 patients (64%). DT was more likely to be conducted for new implants compared with impulse generator replacements (71% vs 32%, P = 0.0001), but was similar for primary and secondary prevention indications (64% vs 63%, P = NS). Among patients not having DT, the reason(s) given were: considered unnecessary (44%); considered unsafe, mainly due to persistent atrial fibrillation (37%); lack of an anesthetist (20%); and, patient or physician preference (6%). When performed, DT consisted of a single successful shock > or = 10J below maximum device output in 65% of cases. A 10J safety-margin was met by 97% of patients, requiring system modification in 2.3%. Major perioperative complications occurred in 4.4% of patients having DT versus 6.6% of patients not having DT (P = NS). ICD insertion was $844 more expensive for patients having DT (P = 0.16), largely due to increased costs ($28,017 vs $24,545) among patients having impulse generator replacement (P = 0.02)., Conclusions: DT was not performed in a third of ICD implants, usually due to a perceived lack of need or relative contraindication.

Background: In patients undergoing cardiac rhythm device surgery, it is common practice to discontinue oral anticoagulation and to perform heparin bridging in order to reduce the risk of bleeding and minimize the risk of thromboembolic events., Objective: The purpose of this study was to determine the perioperative anticoagulation strategies currently in use., Methods: A survey presented four clinical scenarios of patients on oral anticoagulation undergoing cardiac rhythm device surgery. The scenarios represented a gradient of perceived thromboembolic risk based on the presence of atrial fibrillation, a mechanical heart valve, previous stroke, and the remainder of the CHADS(2) risk factors (congestive heart failure, hypertension, age >75 years, diabetes, previous stroke or transient ischemic attack). Respondents were offered six options that included discontinuing oral anticoagulation without heparin, three different heparin bridging protocols, and ongoing oral anticoagulation with reduced or therapeutic dose warfarin., Results: Based on responses from 38 (61%) of 62 electrophysiologists surveyed across Canada, 83% of respondents held warfarin without bridging in a low-risk, 78-year-old patient with atrial fibrillation (CHADS(2) score 1). In three higher-risk patient scenarios, 67% to 100% of respondents chose heparin bridging or ongoing warfarin; 38% to 72% of respondents chose heparin bridging, with 23% to 36% choosing variable use of ongoing warfarin. In all three cases where respondents indicated that they would bridge, each of the three heparin regimens was chosen by at least 20% of respondents., Conclusion: There is a wide range of approaches to perioperative management in patients on oral anticoagulation undergoing cardiac rhythm device surgery. Clinical equipoise is evident and supports the need for comparative studies.

Background: There are few data on the frequency and predictors of tachycardia-induced cardiomyopathy (TICM) in patients with persistent atrial flutter., Objectives: To examine the incidence of TICM in patients undergoing ablation for persistent atrial flutter, and to examine predictors for the development of TICM., Methods and Results: One hundred eleven patients met the inclusion criteria for the present study. Twenty-eight of 111 (25%) patients had cardiomyopathy before ablation. Sixteen of 28 (57%) patients showed significant improvement in their left ventricular (LV) function postablation. LV function improved to normal in 12 of 16 (75%) patients. Nineteen of 28 (68%) cardiomyopathy patients had preablation LV function in the range in which they would be considered for an implantable cardioverter defibrillator for primary prevention of sudden cardiac death. In nine of 19 (47%) patients, the ejection fraction improved such that an implantable cardioverter defibrillator was no longer indicated. In multivariate analysis, average ventricular rate during atrial flutter was the only independent predictor of reversibility of cardiomyopathy (P=0.013)., Conclusions: Sixteen of 28 (57%) cardiomyopathy patients with persistent atrial flutter had significantly improved LV function postablation. In 75% of these patients, LV function improved to normal.

Background/objective: The Canadian Heart Rhythm Society (CHRS) Device Advisory Committee was commissioned in 2006 to develop a mechanism for responding to advisories regarding cardiac rhythm device and lead performance., Methods: In the event of an advisory, the Chair classifies the advisory as urgent, semi-urgent, or routine based on the nature of the threat to the patient and the number of patients affected. The Chair uses an e-mail network with the committee members to disseminate advisory information and to assemble a consensus recommendation. Committee membership is broadly representative of the Canadian device community, including both academic and nonacademic centers, adult and pediatric specialists, and includes balanced regional representation. Recommendations are approved by the CHRS executive and made available to all implant and follow-up centers on the CHRS website., Results: With the Medtronic Fidelis lead advisory of October 15, 2007, the Chair classified the advisory as semi-urgent and initiated an e-mail discussion and preliminary survey of all Canadian implantable cardioverter-defibrillator (ICD) centers within 3 hours of advisory announcement. A CHRS membership statement was issued within 48 hours. Within 5 working days, sample letters to physicians and patients were posted for local adaptation and distribution. Complete data collection was obtained from all Canadian defibrillator centers. Analyses at 20, 25, 30, and 32 months suggest an accelerating course of failures (3.91% at 32 months, P <.0001), with a reduced likelihood of presentation with inappropriate shocks (from 56% to 21%, P = .0003)., Conclusion: A collaborative approach using an e-mail network provides a mechanism for a rapid national response to device advisories. The network allows collection of focused data on implanted device system performance and facilitates timely reporting of clinically relevant data to patients and clinicians.

Short QT syndrome (SQTS) is a rare genetic disease with a risk of sudden cardiac death. The present report describes syncope in a young man that resulted in a motor vehicle accident. An electrocardiogram and initial investigations were unremarkable, but treadmill testing showed a lack of adaptation of the QT interval, which has been described in SQTS. To evaluate the possible diagnosis of SQTS, DNA sequencing of genes known to be associated with SQTS was performed and identified a novel mutation in the KCNH2 gene. Consequently, the patient was diagnosed with SQTS and the recommendation of implantable cardioverter defibrillator implantation was accepted by the patient before discharge from the hospital.

Genetic mutations of the cardiac sodium channel (SCN5A) specific only to the phenotype of atrial fibrillation have recently been described. However, data on the biophysical properties of SCN5A variants associated with atrial fibrillation are scarce. In a mother and son with lone atrial fibrillation, we identified a novel SCN5A coding variant, K1493R, which altered a highly conserved residue in the DIII-IV linker and was located six amino acids downstream from the fast inactivation motif of sodium channels. Biophysical studies of K1493R in tsA201 cells demonstrated a significant positive shift in voltage-dependence of inactivation and a large ramp current near resting membrane potential, indicating a gain-of-function. Enhanced cellular excitability was observed in transfected HL-1 atrial cardiomyocytes, including spontaneous action potential depolarizations and a lower threshold for action potential firing. These novel biophysical observations provide molecular evidence linking cellular "hyperexcitability" as a mechanism inducing vulnerability to this common arrhythmia.

Aims: It is unclear whether there is important psychological morbidity associated with living with an implantable cardioverter defibrillator (ICD) under advisory and whether this should be factored into decision-making., Methods and Results: Our study focused on patients living with advisory Medtronic Marquis ICDs. Patient adjustment to the ICD was evaluated using a validated device-specific metric of patient acceptance, the Florida Patient Acceptance Survey (FPAS). A comparison group of patients with other models of ICDs that were not under an advisory also completed the study measure. The questionnaire return rate was 86/122 (70.5%) in the advisory group and 94/134 (70.1%) in the non-advisory group. Only one patient in our clinic elected for generator change due to severe anxiety. There were no differences in demographic or clinical variables between the groups. There were no differences in the mean total FPAS score between the two patient groups (advisory patients 85.97 +/- 14.95 and 86.23 +/- 15.76 for non-advisory, P=0.340). Also there were no differences in any of the subscores. Correlates of poor device acceptance were younger age and a history of electrical storm., Conclusion: We found no evidence of increased long-term psychological morbidity in patients living with an ICD under advisory compared with patients with an ICD not under advisory. Our data suggest that patients and physicians should avoid hasty decisions about ICD replacement for psychological reasons.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a familial condition that presents with exercise-induced syncope or sudden death in children or young adults. In most cases the disease is caused by a mutation in the cardiac ryanodine receptor (RyR2) gene. Current evidence suggests that primary therapy for CPVT is beta blockade and implantable cardioverter defibrillator (ICD) placement. There is a recent report of a patient with CPVT who died despite appropriate ICD therapies, and we report a similar case. Our patient died after probably initially receiving inappropriate ICD shocks for atrial fibrillation. We recommend that utmost efforts should be made to prevent shocks including repeated exercise testing to confirm suppression of PVT.

Background: Sprint Fidelis (Medtronic Inc., Minneapolis, Minnesota) is a 6.6-F implantable cardioverter-defibrillator lead. In October 2007 the manufacturer suspended distribution of Sprint Fidelis leads secondary to high early fracture rates. Reprogramming of lead impedance alerts was recommended to try to reduce inappropriate shocks., Objective: This study sought to assess how the hazard of Fidelis fracture varies with time, whether lead impedance alert thresholds programmed after recall have prevented inappropriate shocks, and predictors of lead fracture., Methods: We collected clinical and device interrogation data on all lead fractures and performed a Kaplan-Meier analysis. We performed a case control study to examine univariate and multivariate predictors of lead fracture., Results: There have been 17 lead fractures in our cohort of 480 Sprint Fidelis (model 6949) leads, median follow-up 19.8 months. The hazard of fracture increased significantly with time by a power of 2.74 (95% confidence interval: 2.57 to 2.91, P <.0001). Reprogrammed lead impedance thresholds prevented inappropriate shocks in only 1 of 6 patients. Independent predictors of lead fracture were greater left ventricular ejection fraction (P = .0011) and noncephalic venous access (P = .0224)., Conclusion: The risk of lead fracture increased with time by a power of 2.74. Reprogrammed lead impedance thresholds prevented inappropriate shocks in only 1 of 6 patients. Independent predictors of lead fracture were greater left ventricular ejection fraction and noncephalic access.

Background: It has been suggested that remote magnetic navigation (RMN) may provide enhanced catheter stability and substrate contact to aid in ablation. To date, no study has examined this claim. Accordingly, we compared the characteristics of the successful ablation of atrioventricular reentry tachycardia (AVNRT) using RMN with a matched population ablated using a conventional (CON) manual approach., Methods: Sixteen patients who underwent RMN-assisted ablation of typical AVNRT were matched with 16 patients who had a CON-AVNRT ablation., Results: All patients had successful slow pathway modification without complication. The mean catheter temperature achieved with the successful ablation was significantly lower with RMN than with CON (42 +/- 7 degrees C vs 47 +/- 3 degrees C, P

Background: The Medtronic Sprint Fidelis family of leads has recently been the subject of a widespread advisory. Lead failure rates are estimated at 2.3% at 30 months, 2.6 times the failure rate of the reference Medtronic 6947 lead., Objective: The purpose of this study was to contact pediatric and adult implantable cardioverter-defibrillator (ICD) implant centers across Canada to determine the short-term response to the October 15, 2007 Medtronic Fidelis lead advisory., Methods: All centers completed an 11-part survey to assess the frequency and presentation of lead failure, operator characteristics, and center's response., Results: Lead failure was noted in 80 (1.29%) of 6,181 patients at 21.0 months, with inappropriate shocks experienced in 45 (56%) of the 80 patients (overall risk 0.73%). No deaths were attributed to lead failure. Sensing was the primary form of failure, seen in 60 leads (75%), with pacing failure in 10 (13%), and high-voltage failure in 15 (19%). Assessment of the previous routine ICD interrogation prior to the advisory or lead failure demonstrated evidence of altered lead performance in only 8 (10%) of the 80 leads. Inappropriate shocks typically were multiple (median 7, range 1-122), with a single shock seen in only 5 patients. Lead failure was noted in 18 of 23 centers, representing 89.8% of leads implanted, with at least one failure noted in 15 of 16 centers that implanted more than 200 leads. Forty-seven of the 135 operators in the 23 institutions implanted the 80 leads that subsequently failed. Only 16 operators were involved in more than a single lead that subsequently failed; seven operators participated in three or more leads that subsequently failed. Seven centers planned to replace leads in most pacing-dependent patients, and two centers planned to replace leads in patients unable to hear the alert tone., Conclusion: This national experience suggests a Fidelis lead failure rate of 1.29% at 21 months, most often presenting with multiple inappropriate shocks without evidence of impending failure from routine lead follow-up. Lead failure did not appear to cluster around specific operators or around high-volume or low-volume implant centers.

Standard autopsy of young victims with sudden cardiac death commonly does not identify a specific pathological diagnosis. In such cases, sudden cardiac death may be secondary to a genetic condition predisposing the patient to ventricular arrhythmias. Failure to identify a genetic etiology for an unexpected sudden death may leave surviving family members at risk for a similar tragedy. The case of a 21-year-old woman who died suddenly while at rest is presented. Molecular genetic analysis of tissue retrieved from the regional coroner's office identified a novel missense mutation in the KCNH2 gene, a gene known to cause the long QT syndrome.

Background: Cardiac arrest due to ventricular arrhythmia in the absence of a reversible cause or contraindication has been a class I indication for insertion of an implantable cardioverter defibrillator since 1998. We compared and contrasted the use of implantable cardioverter defibrillator therapy in Canada and the United States among adults who survived a cardiac arrest., Method: Data on hospital separations from April 1, 1994 through March 31, 2003 were obtained from the Health Person-Oriented Information Database maintained by Statistics Canada and from the US National Hospital Discharge Survey on all patients with a primary diagnosis of cardiac arrest, ventricular fibrillation or ventricular flutter for the same 9-year period. We excluded all records of patients with a secondary diagnosis of acute myocardial infarction., Results: In Canada, 3793 patients survived to discharge after a cardiac arrest; 628 (16.6%) of these were implanted with a cardioverter defibrillator before discharge. The implant rate rose steadily from 5.4% in 1994/95 to 26.7% in 2002/03. In the United States, 23 688 (30.2%) of 78 538 such survivors received an implantable cardioverter defibrillator before discharge. Logistic regression analysis indicated that sex, age, fiscal year, the hospital's teaching status, hospital size and patient history of heart failure were positive predictors of implantable cardioverter defibrillator implantation. Age, renal failure, liver failure and cancer were negative predictors of receiving an implantable cardioverter defibrillator., Interpretation: The rate of use of implantable cardioverter defibrillator therapy for cardiac arrest survivors in Canada is increasing, but still is lower than the rate in the United States.

Aims: This study sought to investigate the influence of gender on access to ICD therapy and examine the influence of gender on subsequent ICD shock experience., Methods and Results: The records of 353 consecutive patients (140 and 213 secondary prevention, respectively) who received their first ICD between January 2000 and March 2004 were reviewed. All patients fulfilled criteria for primary or secondary prevention ICD implantation. Baseline characteristics and ICD shock experiences were compared. Female patients were younger and less likely to have a history of ischaemic heart disease or atrial arrhythmias (P<0.01). In contrast, female patients were more likely to have heart failure and diabetes (P<0.01). Markedly fewer females received an ICD for either primary (M:F ratio 8.5:1, P<0.01) or secondary (M:F ratio 4.5:1, P<0.01) prevention. Further, significantly fewer female patients received an ICD for MADIT II indications (M:F 11.2:1, P<0.01). Over the mean follow-up of 1.8+/-1.1 years, gender had no influence upon the likelihood of receiving either an appropriate or an inappropriate shock (P=ns)., Conclusion: Although male patients accounted for the great majority (85%) of all ICD recipients, there was no evidence of influence of gender on the likelihood of receiving an appropriate or inappropriate shock.

The authors report a case of transient left ventricular apical ballooning after a prolonged electrophysiology procedure. Interventional electrophysiologists should be aware of this syndrome as a potential complication.

A case of inappropriate detection of an ungrounded external AC current by an implantable cardioverter defibrillator (ICD) is reported. The resultant ICD shock dislodged the patient from the electrical source, thus preventing injury or electrocution.

Objective: Using conventional catheters, ablation of concealed parahisian accessory pathways may be difficult and high risk for heart block., Methods and Results: We describe the case of a concealed parahisian accessory pathway with three prior attempts to ablate using conventional methods (RF and cryotherapy). Using a remote magnetic navigation system, successful ablation occurred following a single RF lesion (total fluoroscopy time 17 min). In contrast to previous attempts, the patient remained asymptomatic during follow-up (12 months)., Conclusions: This is the first report of successful remote magnetic catheter ablation of a concealed parahisian AP. Magnetic catheter stability during RF application likely contributed to the success of this procedure and may have minimized the risk of AV block.

Reports from case series have estimated the incidence of peripartum cardiomyopathy (PC) at 1 case/1,485 live births to 1 case/15,000 live births and probable mortality rates of 7% to 60%. The objective of this study was to produce the first population-based study of the incidence, mortality, and risk factors for PC. The National Hospital Discharge Survey was used. Discharge information was available for 3.6 million patient discharges from 1990 to 2002. There were an estimated 16,296 cases of PC from 1990 to 2002. During this period, there were 51,966,560 live births in the United States. Thus, the incidence of PC was 1 case/3,189 live births. There was a trend toward an increase in PC incidence during the study period, with an estimate for the years 2000 to 2002 of 1 case/2,289 live births. The in-hospital mortality rate was 1.36% (95% confidence interval 0% to 10.2%). The total mortality rate was 2.05% (95% confidence interval 0.29% to 10.8%). Patients with PC were older (mean age 29.7 vs 26.9 years), were more likely to be black (32.2% vs 15.7%), and had a higher incidence of pregnancy associated hypertensive disorders (22.5% vs 5.87%) compared with national data. In conclusion, the incidence of PC is relatively uncommon, occurring at an average frequency of 1 case/3,189 live births from 1990 to 2002. The estimated mortality of 1.36% to 2.05% (95% confidence interval 0.29% to 10.8%) is less than previously reported from most case series.

A case of complex atrial tachyarrhythmias following orthotopic heart transplantation is presented. The ablation strategy in such a situation and the outcome achieved are discussed.