Long-Term Outcomes of Resynchronization-Defibrillation for Heart Failure.

BACKGROUND: The Resynchronization-Defibrillation for Ambulatory Heart Failure Trial (RAFT) showed a greater benefit with respect to mortality at 5 years among patients who received cardiac-resynchronization therapy (CRT) than among those who received implantable cardioverter-defibrillators (ICDs). However, the effect of CRT on long-term survival is not known. 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 a CRT defibrillator (CRT-D). We assessed long-term outcomes among patients at the eight highest-enrolling participating sites. The primary outcome was death from any cause; the secondary outcome was a composite of death from any cause, heart transplantation, or implantation of a ventricular assist device. RESULTS: The trial enrolled 1798 patients, of whom 1050 were included in the long-term survival trial; the median duration of follow-up for the 1050 patients was 7.7 years (interquartile range, 3.9 to 12.8), and the median duration of follow-up for those who survived was 13.9 years (interquartile range, 12.8 to 15.7). Death occurred in 405 of 530 patients (76.4%) assigned to the ICD group and in 370 of 520 patients (71.2%) assigned to the CRT-D group. The time until death appeared to be longer for those assigned to receive a CRT-D than for those assigned to receive an ICD (acceleration factor, 0.80; 95% confidence interval, 0.69 to 0.92; P = 0.002). A secondary-outcome event occurred in 412 patients (77.7%) in the ICD group and in 392 (75.4%) in the CRT-D group. CONCLUSIONS: Among patients with a reduced ejection fraction, a widened QRS complex, and NYHA class II or III heart failure, the survival benefit associated with receipt of a CRT-D as compared with ICD appeared to be sustained during a median of nearly 14 years of follow-up. (RAFT ClinicalTrials.gov number, NCT00251251.).

Management of Inherited Arrhythmia Syndromes: A HiRO Consensus Handbook on Process of Care.

Inherited arrhythmia syndromes are rare genetic conditions that predispose seemingly healthy individuals to sudden cardiac arrest and death. The Hearts in Rhythm Organization is a multidisciplinary Canadian network of clinicians, researchers, patients, and families that aims to improve care for patients and families with inherited cardiac conditions, focused on those that confer predisposition to arrhythmia and sudden cardiac arrest and/or death. The field is rapidly evolving as research discoveries increase. A streamlined, practical guide for providers to diagnose and follow pediatric and adult patients with inherited cardiac conditions represents a useful tool to improve health system utilization, clinical management, and research related to these conditions. This review provides consensus care pathways for 7 conditions, including the 4 most common inherited cardiac conditions that confer predisposition to arrhythmia, with scenarios to guide investigation, diagnosis, risk stratification, and management. These conditions include Brugada syndrome, long QT syndrome, arrhythmogenic right ventricular cardiomyopathy and related arrhythmogenic cardiomyopathies, and catecholaminergic polymorphic ventricular tachycardia. In addition, an approach to investigating and managing sudden cardiac arrest, sudden unexpected death, and first-degree family members of affected individuals is provided. Referral to specialized cardiogenetic clinics should be considered in most cases. The intention of this review is to offer a framework for the process of care that is useful for both experts and nonexperts, and related allied disciplines such as hospital management, diagnostic services, coroners, and pathologists, in order to provide high-quality, multidisciplinary, standardized care.

Les syndromes d'arythmie héréditaires sont des troubles génétiques rares qui prédisposent des personnes en apparence en bonne santé à un arrêt cardiaque soudain et à la mort. L'organisation Hearts in Rhythm Organization est un réseau multidisciplinaire canadien qui regroupe des cliniciens, des chercheurs ainsi que des patients et leurs proches dans le but d'améliorer les soins prodigués aux patients atteints de maladies cardiaques héréditaires et à leur famille, en particulier dans le cas des maladies qui entraînent une prédisposition à l'arythmie et à un arrêt cardiaque soudain et/ou à la mort. Puisque ce champ de recherche évolue rapidement, la mise au point d'un guide pratique et simple à l'intention des professionnels de la santé pour le diagnostic et le suivi des patients enfants et adultes présentant une maladie cardiaque héréditaire serait donc un outil intéressant pour améliorer l'utilisation du système de santé et la prise en charge clinique de ces maladies tout en orientant la recherche à ce propos. La présente synthèse expose les trajectoires de soins faisant l'objet d'un consensus pour sept maladies, dont les quatre maladies cardiaques héréditaires les plus courantes qui prédisposent à l'arythmie. Elle présente aussi des scénarios pour orienter les examens, le diagnostic, la stratification du risque et la prise en charge des patients. Ces maladies sont le syndrome de Brugada, le syndrome du QT long, la cardiomyopathie arythmogénique du ventricule droit et les cardiomyopathies arythmogènes associées, et la tachycardie ventriculaire polymorphe catécholaminergique. En outre, une approche pour la prise en charge de l'arrêt cardiaque soudain, de mort subite inattendue et des membres de la famille immédiate de la personne touchée est proposée. L'orientation vers des cliniques spécialisées en cardiogénétique doit être envisagée dans la plupart des cas. L'objectif est d'établir un cadre de soins qui soit utile pour les experts et les non-experts ainsi que pour les professionnels des domaines connexes, par exemple le personnel de l'administration hospitalière et des services diagnostiques, les coroners et les pathologistes, en vue d'offrir des soins multidisciplinaires normalisés de grande qualité.

Patients acceptance and comprehension to written and verbal consent (PAC-VC).

BACKGROUND: Acute myocardial infarction (AMI) research is challenging as it requires enrollment of acutely ill patients. Patients are generally in a suboptimal state for providing informed consent. Patients' understanding to verbal assents have not been previously examined in AMI research. Patients Acceptance and Comprehension to Written and Verbal Consent (PAC-VC) compared patients' understanding and attitudes to verbal and written consents in AMI RCTs. METHODS: PAC-VC recruited patients from 3 AMI trials using both verbal N = 12 and written N = 6 consents. We compared patients' understanding using two survey questionnaires. The first questionnaire used open-ended questions with multiple choice answers. The second questionnaire used a 5-point Likert scale to measure patients understanding and attitudes to the consent process. Overall answers average scores were categorized into three groups: Adequate understanding (71-100) %, Partial understanding (41-70)% and Inadequate understanding (0-40)%. RESULTS: Responses showed patients with verbal assent had adequate understanding to most components of informed consent, close to those of written consent. Most patients did not read written information entirely and believed that it is not important to make a final decision. Patients favoured to have written information be part of the consent but not necessarily presented during the initial consent process. Patients felt less pressured in the verbal assent arm than those of written consent. CONCLUSION: Patients had adequate understanding to most components of verbal assent and comparable to those of written consent. Utilizing verbal assents in the acute care setting should be further assessed in larger trials.

Identification and in-silico characterization of splice-site variants from a large cardiogenetic national registry.

Splice-site variants in cardiac genes may predispose carriers to potentially lethal arrhythmias. To investigate, we screened 1315 probands and first-degree relatives enrolled in the Canadian Hearts in Rhythm Organization (HiRO) registry. 10% (134/1315) of patients in the HiRO registry carry variants within 10 base-pairs of the intron-exon boundary with 78% (104/134) otherwise genotype negative. These 134 probands were carriers of 57 unique variants. For each variant, American College of Medical Genetics and Genomics (ACMG) classification was revisited based on consensus between nine in silico tools. Due in part to the in silico algorithms, seven variants were reclassified from the original report, with the majority (6/7) downgraded. Our analyses predicted 53% (30/57) of variants to be likely/pathogenic. For the 57 variants, an average of 9 tools were able to score variants within splice sites, while 6.5 tools responded for variants outside these sites. With likely/pathogenic classification considered a positive outcome, the ACMG classification was used to calculate sensitivity/specificity of each tool. Among these, Combined Annotation Dependent Depletion (CADD) had good sensitivity (93%) and the highest response rate (131/134, 98%), dbscSNV was also sensitive (97%), and SpliceAI was the most specific (64%) tool. Splice variants remain an important consideration in gene elusive inherited arrhythmia syndromes. Screening for intronic variants, even when restricted to the ±10 positions as performed here may improve genetic testing yield. We compare 9 freely available in silico tools and provide recommendations regarding their predictive capabilities. Moreover, we highlight several novel cardiomyopathy-associated variants which merit further study.

Sex Differences and Utility of Treadmill Testing in Long-QT Syndrome.

Background Diagnosis of congenital long-QT syndrome (LQTS) is complicated by phenotypic ambiguity, with a frequent normal-to-borderline resting QT interval. A 3-step algorithm based on exercise response of the corrected QT interval (QTc) was previously developed to diagnose patients with LQTS and predict subtype. This study evaluated the 3-step algorithm in a population that is more representative of the general population with LQTS with milder phenotypes and establishes sex-specific cutoffs beyond the resting QTc. Methods and Results We identified 208 LQTS likely pathogenic or pathogenic KCNQ1 or KCNH2 variant carriers in the Canadian NLQTS (National Long-QT Syndrome) Registry and 215 unaffected controls from the HiRO (Hearts in Rhythm Organization) Registry. Exercise treadmill tests were analyzed across the 5 stages of the Bruce protocol. The predictive value of exercise ECG characteristics was analyzed using receiver operating characteristic curve analysis to identify optimal cutoff values. A total of 78% of male carriers and 74% of female carriers had a resting QTc value in the normal-to-borderline range. The 4-minute recovery QTc demonstrated the best predictive value for carrier status in both sexes, with better LQTS ascertainment in female patients (area under the curve, 0.90 versus 0.82), with greater sensitivity and specificity. The optimal cutoff value for the 4-minute recovery period was 440 milliseconds for male patients and 450 milliseconds for female patients. The 1-minute recovery QTc had the best predictive value in female patients for differentiating LQTS1 versus LQTS2 (area under the curve, 0.82), and the peak exercise QTc had a marginally better predictive value in male patients for subtype with (area under the curve, 0.71). The optimal cutoff value for the 1-minute recovery period was 435 milliseconds for male patients and 455 milliseconds for femal patients. Conclusions The 3-step QT exercise algorithm is a valid tool for the diagnosis of LQTS in a general population with more frequent ambiguity in phenotype. The algorithm is a simple and reliable method for the identification and prediction of the 2 major genotypes of LQTS.

Bidirectional Ventricular Tachycardia: Challenges and Solutions.

Bidirectional ventricular tachycardia (BiVT) is a rare form of ventricular tachycardia that manifests on surface electrocardiogram by dual QRS morphologies alternating on a beat-to-beat basis. It was first reported in the 1920s as a complication of digoxin, and since then, it has been reported in other conditions including fulminant myocarditis, sarcoidosis, catecholaminergic polymorphic ventricular tachycardia, and Andersen-Tawil syndrome. The mechanism for BiVT is not as well known as other forms of ventricular tachycardia but appears to include typical mechanisms including triggered activity from afterdepolarizations, abnormal automaticity, or reentry. This review will go beyond the definition, surface electrocardiogram, mechanisms, causes, and treatment of BiVT as per our current understanding.

Return of Results Policies for Genomic Research: Current Practices and the Hearts in Rhythm Organization (HiRO) Approach.

Research teams developing biobanks and/or genomic databases must develop policies for the disclosure and reporting of potentially actionable genomic results to research participants. Currently, a broad range of approaches to the return of results exist, with some studies opting for nondisclosure of research results and others following clinical guidelines for the return of potentially actionable findings from sequencing. In this review, we describe current practices and highlight decisions a research team must make when designing a return of results policy, from informed consent to disclosure practices and clinical validation options. The unique challenges of returning incidental findings in cardiac genes, including reduced penetrance and the lack of clinical screening standards for phenotype-negative individuals, are discussed. Finally, the National Hearts in Rhythm Organisation (HiRO) Registry approach is described to provide a rationale for the selective return of field-specific variants to those participating in disease-specific research. Our goal is to provide researchers with a resource when developing a return of results policy tailored for their research program, based on unique factors related to study design, research team composition, and availability of clinical resources.

Clinical utility of 12-lead electrocardiogram in evaluating heart disease in patients with muscular dystrophy: Assessment of left ventricular hypertrophy, conduction disease, and cardiomyopathy.

INTRODUCTION: Heart disease remains a leading cause of mortality in patients with muscular dystrophy (MD), and cardiac assessment by standard imaging modalities is challenging due to the prominence of physical limitations. METHODS: In this prospective cohort study of 169 MD patients and 34 negative control patients, we demonstrate the clinical utility of a 12-lead electrocardiogram (ECG) as an effective modality for the assessment of cardiac status in patients with MD. We assessed the utility of conventional criteria for electrocardiogram-indicated left ventricular hypertrophy (ECG-LVH) as well as ECG morphologies. RESULTS: Cornell voltage, Cornell voltage-duration, Sokolow-Lyon voltage, and Romhilt-Estes point score criteria demonstrated low sensitivity and minimal positive predictive value for ECG-LVH when compared with cardiac imaging. Patients with LBBB had a high probability of a cardiomyopathy (relative risk [RR], 2.75; 95% confidence interval [CI], 2.14-3.53; p < .001), and patients with QRS fragmentation (fQRS) had a high probability of a cardiomyopathy (RR, 1.76; 95% CI, 1.20-2.59; p = .004), requiring cardiac medication and device intervention. We found that an R/S ratio >1 in V1 and V2 is highly specific (specificity, 0.89; negative predictive value [NPV], 0.89 and specificity, 0.82; NPV, 0.89, respectively) for patients with dystrophinopathies compared with other types of MD. CONCLUSION: The identification of LBBB and fQRS was linked to cardiomyopathy in patients with MD, while ECG-LVH was of limited utility. Importantly, these findings can be applied to effectively screen a broad cohort of MD patients for structural heart disease and prompt further evaluation and therapeutic intervention.

Plasma Exchange for Immune Checkpoint Inhibitor-Induced Myocarditis.

Immune checkpoint inhibitor therapy has been shown to improve outcomes across many types of malignancies. However, immune checkpoint inhibitor has been associated with several immune-related adverse events including myocarditis. We describe the case of a 69-year-old man with fulminant myocarditis likely due to pembrolizumab therapy, complicated by biventricular failure with cardiogenic shock. Because of deterioration in hemodynamic status refractory to conventional immunosuppression, therapeutic plasma exchange was performed, resulting in a rapid reduction of serum pembrolizumab levels, and marked clinical, radiological, and biochemical improvement. To our knowledge, this is the first reported case on the successful use of plasma exchange for pembrolizumab-associated fulminant myocarditis.

Il a été montré que le traitement par un inhibiteur du point de contrôle immunitaire améliore les résultats dans de nombreux types de cancer. Un inhibiteur du point de contrôle immunitaire a toutefois été associé à plusieurs effets indésirables d'origine immunologique, y compris la myocardite. Nous vous présentons le cas d'un homme de 69 ans ayant présenté une myocardite fulminante, probablement causée par un traitement par le pembrolizumab, compliquée par une insuffisance biventriculaire accompagnée d'un choc cardiogénique. En raison de la détérioration de l'état hémodynamique réfractaire à une immunosuppression classique, un échange plasmatique thérapeutique a été effectué, lequel a entraîné une réduction rapide des taux sériques de pembrolizumab, et une amélioration marquée sur les plans clinique, radiologique et biochimique. À notre connaissance, il s'agit du premier cas signalé dans lequel un échange plasmatique a été utilisé avec succès pour traiter une myocardite fulminante associée au pembrolizumab.

The Hearts in Rhythm Organization: A Canadian National Cardiogenetics Network.

BACKGROUND: The Hearts in Rhythm Organization (HiRO) is a team of Canadian inherited heart rhythm and cardiomyopathy experts, genetic counsellors, nurses, researchers, patients, and families dedicated to the detection of inherited arrhythmias and cardiomyopathies, provision of best therapies, and protection from the tragedy of sudden cardiac arrest. METHODS: Recently, existing disease-specific registries were merged into the expanded National HiRO Registry, creating a single common data set for patients and families with inherited conditions that put them at risk for sudden death in Canada. Eligible patients are invited to participate in the registry and optional biobank from 20 specialized cardiogenetics clinics across Canada. RESULTS: Currently, there are 4700 participants enrolled in the National HiRO Registry, with an average of 593 participants enrolled annually over the past 5 years. The capacity to enable knowledge translation of research findings is built into HiRO's organizational infrastructure, with 3 additional working groups (HiRO Clinical Care Committee, HiRO Active Communities Committee, and HiRO Annual Symposium Committee), supporting the organization's current goals and priorities as set alongside patient partners. CONCLUSION: The National HiRO Registry aims to be an integrated research platform to which researchers can pose novel research questions leading to a better understanding, detection, and clinical care of those living with inherited heart rhythm and cardiomyopathy conditions and ultimately to prevent sudden cardiac death.

CONTEXTE: La Hearts in Rhythm Organization (HiRO) est une équipe d'experts canadiens en matière de rythmes cardiaques et de cardiomyopathies héréditaires, de conseillers en génétique, d'infirmières, de chercheurs, de patients et de familles qui se consacrent à la détection des arythmies et des cardiomyopathies héréditaires, à la mise en place des meilleures thérapies et à la protection contre la tragédie que représente une mort subite d'origine cardiaque. MÉTHODES: Récemment, les registres existants relatifs à des maladies spécifiques ont été fusionnés en un registre national élargi de l'HiRO, créant ainsi un ensemble de données commun unique à destination des patients et leurs familles, atteints de maladies héréditaires, qui sont à risque de mort subite au Canada. Les patients admissibles sont invités à s'associer au registre et à la biobanque facultative regroupant 20 cliniques spécialisées en cardiogénétique au Canada. RÉSULTATS: Actuellement, 4 700 participants sont inscrits au registre national de l'HiRO, avec une moyenne de 593 participants inscrits chaque année au cours des cinq dernières années. La capacité à favoriser l'application des connaissances issues de la recherche fait partie de la structure organisationnelle de l'HiRO, avec trois groupes de travail supplémentaires (comité des soins cliniques de l'HiRO, comité des communautés cctives de l'HiRO et comité du symposium annuel de l'HiRO), soutenant les objectifs et les priorités actuels de l'organisation tels qu'ils ont été fixés en partenariat avec les patients. CONCLUSION: Le registre national de l'HiRO vise à devenir une plateforme de recherche intégrée au sein de laquelle les chercheurs peuvent exposer des questions de recherche inédites permettant de mieux comprendre, détecter et soigner les personnes atteintes de troubles du rythme cardiaque et de cardiomyopathie héréditaires et, à terme, de prévenir la mort subite d'origine cardiaque.

Comparison of Usefulness of Cardiac Resynchronization Therapy in Patients With Type 1 Myotonic Dystrophy With Versus Without Left Bundle Branch Block.

Patients with type 1 myotonic dystrophy show reduced left ventricular systolic function in the presence of left bundle branch block due to electromechanical dys-synchrony. Our prospective study tracked a cohort of 64 type 1 myotonic dystrophy patients that demonstrated a high burden of atrial and ventricular arrhythmias and conduction delays. Of these patients, 12 (19%) patients had left bundle branch block, which was associated with reduced left ventricular systolic function. Eight of these patients received cardiac resynchronization therapy devices resulting in reduction of median QRS complex duration from 173 to 166 ms (p = 0.04), and improvement in median left ventricular ejection fraction from 37% to 46% (p = 0.007). In conclusion, cardiac resynchronization therapy device therapy is both feasible and effective in treating advanced cardiac disease in this vulnerable group of patients by improving left ventricular function.

A Population-Based Study of Adherence to Guideline Recommendations and Appropriate-Use Criteria for Implantable Cardioverter Defibrillators.

Studies evaluating physician adherence to guideline recommendations for implantable cardioverter defibrillator (ICD) therapy are sparse, and none exist for the application of appropriate-use criteria (AUC) in clinical practice. As part of a quality improvement initiative, a review of all ICD procedures was performed from January 1, 2015 to December 31, 2016 in Alberta, Canada, to evaluate the proportion of patients receiving appropriate ICD therapy and to identify reasons for nonadherence. Our device-implant process involves an electrophysiologist or implanting cardiologist evaluation, reminders of ICD eligibility criteria on the device requisition, and peer-review consensus. Implants were classified according to the 2008 American College of Cardiology/American Heart Association/Heart Rhythm Society (ACC/AHA/HRS) ICD guidelines, 2013 Canadian Cardiovascular Society (CCS) Cardiac Resynchronization Therapy (CRT) guidelines, and 2013 AUC. There were 1,300 ICD procedures performed, and the mean age was 63.8 ± 12.9 years; 79% were male; the mean ejection fraction was 0.32 ± 0.13, and 69% were for primary prevention. Among all implants, < 1% were discordant with American College of Cardiology/American Heart Association/Heart Rhythm Society (ACC/AHA/HRS) recommendations. Among CRT implants, 10% were inconsistent with Canadian Cardiovascular Society (CCS) recommendations. According to AUC, 92% of implants were appropriate. Reasons for nonadherence to ACC/AHA/HRS recommendations included QRS width < 120 msec (n = 3), LVEF > 0.35 (n = 2) and recent myocardial infarction (MI) (n = 1). The most common reason for nonadherence to AUC was the absence of criteria for classification (n = 57, 4%). In this population-based study, we found that a process of specialist evaluation, eligibility reminders on device forms, and peer-review consensus may improve adherence to guideline recommendations and AUC for ICD therapy.

Impact of Cardiac Resynchronization Therapy on Daily Physical Activity in Heart Failure Patients.

PURPOSE: Cardiac resynchronization therapy (CRT) has emerged as a beneficial therapy for heart failure (HF) patients. It has been shown to enhance cardiac pump function and increase exercise capacity in patients with HF who display wide QRS complex on their electrocardiogram. To date, few studies have assessed daily physical activity (PA) in CRT patients. The objective of this pilot study was to assess the impact of CRT on the physical function and daily PA of HF patients who met the standard indications for CRT implantation. METHODS: The daily PA of 18 CRT patients was measured using a SenseWear Armband for ∼3 d. Daily PA measurements included steps/d and time spent sedentary (≤1.5 metabolic equivalent tasks), in light PA (1.6-2.9 metabolic equivalent tasks), and in moderate-vigorous PA (≥3 metabolic equivalent tasks). To assess exercise capacity, a 6-min walk test was performed pre- and post-CRT. RESULTS: There was no significant change in the 6-min walk test distance from pre- to post-CRT (383 ± 99 m at baseline vs 402 ± 104 m post-CRT). There was a decrease in total steps/d from 3405 ± 2334 pre-CRT to 2553 ± 1692 post-CRT (P = .017). Furthermore, no significant changes were observed pre- to post-CRT with regard to the additional PA assessments. CONCLUSIONS: Our patients exhibited a sedentary lifestyle pre- and post-CRT. These findings underscore the need for a cardiac rehabilitation program that encourages post-CRT patients to decrease sedentary time.

Defibrillation success is not associated with near field electrogram complexity or shock timing.

BACKGROUND: It has been suggested that more-complex fibrillation requires higher energy shocks to terminate. Furthermore, animal studies have demonstrated that shock timing also plays a role. The objective of this study was to test these assertions in a clinical context. METHODS: Near- and far-field electrograms were collected during defibrillation threshold testing. Fibrillation complexity was measured by quantifying the organization in the signals with wavelet-based methods, scaling exponent, and cross-correlation analysis. Receiver operator characteristic curves were used to determine predictive value. The effect of the phase at which defibrillation shocks were applied was also determined. RESULTS: No measure was able to classify whether a particular shock would be successful. All performed very poorly. Shock timing played no role in defibrillation outcome. CONCLUSIONS: Signal organization of a local electrogram and phase of shock delivery do not relate to minimum defibrillation shock energy immediately after ventricular fibrillation onset.

Predicting defibrillation outcome based on phase of ventricular activity during ICD implantation.

Implantable cardioverter-defibrillators (ICDs) are well known medical device for patients who are at a risk of sudden cardiac death caused by ventricular fibrillation (VF). The relationship between VF mechanisms and successful ICD therapy to terminate of VF is still not well understood. The purpose of this work is to evaluate the timing of ICD therapy as a predictor of successful VF termination. Clinical data sets were recorded from the patients who underwent ICD implantation in 6 Canadian centers. Timing of the defibrillation attempt (phase) was analyzed by using the ICD Marker Channel which monitors and displays cardiac events sensed by ICD. Phase, based on the VF period, was divided into 10 equally distributed bins and number of successful defibrillation episodes in each bin was compared. A total of 187 defibrillation attempts were identified from the 65 subjects. 126 of the defibrillation attempts were successful, while 61 failed. The optimal case was observed at a phase value of 1.2pi with 2 successful attempts. The lowest performance rate was found at a phase value of 1.4pi and 1.8pi with 50% (3 and 2 successful attempts, respectively). The probability of success was analyzed by using generalized estimating equations (GEE) approach with an exchangeable correlation structure. The results of the GEE logistic regression model indicate no correlation between successful defibrillation attempts and phase of ventricular activity during VF (p-value = 0.78). From our results, timing of defibrillation shock attempt is not a factor in successful termination of VF for patients undergoing ICD implantation.

Complications associated with defibrillation threshold testing: the Canadian experience.

BACKGROUND: Defibrillation threshold (DFT) testing has traditionally been a routine part of implantable cardioverter-defibrillator (ICD) implantation, despite a lack of compelling evidence that it predicts or improves outcomes. In the past, when devices were much less reliable, DFT testing seemed prudent; however, modern ICD systems have such a high rate of successful defibrillation that many electrophysiologists now question whether DFT testing is still worthwhile, particularly since DFT testing may now be the highest acute risk component of ICD implantation. OBJECTIVE: The purpose of this study was to systematically document complications directly attributable to intraoperative DFT testing. METHODS: We obtained data on DFT-related complications from all 21 adult ICD implant centers in Canada, covering the period from January 1, 2000, to September 30, 2006. RESULTS: There were a total of 19,067 ICD implants in Canada during the study period. There were three DFT testing-related deaths, five DFT testing-related strokes, and 27 episodes that required prolonged resuscitation. Two patients had significant clinical sequelae after prolonged resuscitation. CONCLUSIONS: The risk of severe complications from intraoperative DFT testing appears small, even allowing for the underestimation of its true rate with the current study methodology. These slight but measurable risks must be considered when assessing the risk-benefit ratio of the procedure. Additional data from ongoing prospective ICD registries and/or clinical trials are required.

Proportion of patients followed in a specialized heart failure clinic needing an implantable cardioverter defibrillator as determined by applying different trial eligibility criteria.

Numerous trials have demonstrated survival benefits using implantable cardioverter defibrillators (ICDs) for primary prevention in selected patients with left ventricular (LV) systolic dysfunction. However, eligibility criteria differed across these trials. Without a risk stratification scheme that clearly identifies those who will benefit, there remains debate about which patients with heart failure (HF) should receive ICDs for primary prevention. To explore the implications of applying different eligibility criteria, this study evaluated all patients seen in a specialized HF clinic from August 2003 to January 2004. Of the 309 consecutive patients in the cohort, 46 were excluded because their HF complicated recent myocardial infarcts (n = 3); their LV ejection fractions were not measured (n = 9); or their HF was due to valvular disease, myocarditis, or peripartum cardiomyopathy (n = 34). The Multicenter Automatic Defibrillator Implantation Trial-II criteria were met by 85 patients (32%), and 134 patients (51%) met the Sudden Cardiac Death in Heart Failure Trial criteria. Even allocation decisions based on randomized trial evidence can have vastly different resource implications depending on which trial is chosen. Thus, the development and validation of a risk stratification scheme to identify those patients most likely to benefit from ICDs for primary prophylaxis should be a research priority.

How many patients with heart failure are eligible for cardiac resynchronization? Insights from two prospective cohorts.

AIMS: To determine what proportion of patients with heart failure are eligible for cardiac resynchronization therapy (CRT). METHODS AND RESULTS: Eligibility criteria from the trials establishing the efficacy of CRT were applied to two prospective cohorts: the first enrolled patients with newly diagnosed heart failure discharged from 103 hospitals between April 1999 and March 2001 ('the hospital discharge cohort'); the second enrolled patients seen in a specialized clinic between August 2003 and January 2004 ('the specialty clinic cohort'). In the hospital discharge cohort, 73 patients (3% of the 2640 patients with ischaemic or dilated cardiomyopathy and 1% of all 9096 patients with heart failure discharged alive) met trial eligibility criteria: LVEF< or =0.35, QRS > or =120 ms, sinus rhythm, and NYHA class III or IV symptoms despite the treatment with ACE-inhibitor/angiotensin receptor blocker and beta-blocker. In the specialty clinic cohort, 54 patients (21% of the 263 patients with ischaemic or dilated cardiomyopathy and 17% of all 309 patients with heart failure) met these criteria. If persistent symptoms despite taking spironolactone were required for CRT eligibility, then the proportions qualifying dropped to 1% in the hospital discharge cohort and 18% in the specialty clinic cohort. CONCLUSION: Few heart failure patients meet trial eligibility criteria for CRT.