Michael J. Kilborn

Impact of new task force criteria in the diagnosis of arrhythmogenic right ventricular cardiomyopathy

BACKGROUND Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy that can lead to sudden cardiac death. The diagnostic criterion has recently been revised and through the use of cardiac magnetic resonance (CMR) imaging this study aimed to assess the clinical impact of comparing the original 1994 task force (TF) criterion to the revised 2010 criterion. METHODS We evaluated 173 consecutive CMR scans of patients referred with clinical suspicion of ARVC between 2008 and 2011. We then compared the prevalence of major and minor CMR criteria by applying the two criteria. RESULTS Using the 1994 TF criterion, 13 (7.5%) patients had definite, 11 (6.4%) had borderline, and 39 (22.5%) had possible ARVC. Using the 2010 TF criterion, 10 (5.8%) patients had definite, 1 had borderline, and 7 had (0.04%) possible ARVC. With the 1994 criterion, 81 patients satisfied CMR criterion, of which 36 (44%) had major and 45 (56%) had minor criteria. Upon reclassification with the revised criterion, 61 of the 81 patients were not assigned any criteria, even though many patients had significant risk factors. The negative predictive values (NPV) for both CMR criteria were 100% but the positive predictive values (PPV) for combined CMR major or minor criteria improved from 23% to 55%. CONCLUSIONS Revision of the criterion has enhanced the diagnostic capabilities of CMR but has resulted in a large cohort of patients not classified. In these patients, there is presently no official consensus on imaging or clinical strategy for surveillance of the evolution of pathology over time.

Systematic Review of Defibrillation Threshold Testing at De Novo Implantation

Background—Recent results from the largest multicenter randomized trial (Shockless IMPLant Evaluation [SIMPLE]) on defibrillation threshold (DFT) testing suggest that while shock testing seems safe, it does not reduce the risk of failed shocks or prolong survival. A contemporary systematic review of DFT versus no-DFT testing at the time of implantable cardioverter–defibrillator implantation was performed to evaluate the current evidence and to assess the impact of the SIMPLE study. Methods and Results—Electronic searches were performed using 6 databases from their inception to March 2014. Relevant studies investigating implant DFT were identified. Data were extracted and analyzed according to predefined clinical end points. Predefined outcomes for interrogation were all-cause mortality, composite end point of implantable cardioverter–defibrillator efficacy (arrhythmic deaths and ineffective shocks), and composite safety end point (the sum of complications recorded at 30 days). Meta-analysis was performed including 13 studies and 9740 patients. No significant differences between DFT versus no-DFT cohorts were found in terms of all-cause mortality (risk ratio, 0.90; 95% confidence interval, 0.71–1.15; P=0.41), composite efficacy outcome (risk ratio, 1.24; 95% confidence interval, 0.65–3.37; P=0.51), and 30-day postimplant complications (risk ratio, 1.18; 95% confidence interval, 0.87–1.60; P=0.29). No significant difference was found in the trends observed when the results of the SIMPLE study were excluded or included. Conclusions—This systematic review of contemporary data suggests a modest average effect of DFT, if any, in terms of mortality, shock efficacy, or safety. Therefore, DFT testing should no longer be compulsory during de novo implantation. However, DFT testing may still be clinically relevant in specific patient populations.

Hypoglycaemia and QT interval prolongation: Detection by simultaneous Holter and continuous glucose monitoring

This study using simultaneous Holter and continuous glucose monitoring demonstrates that prolongation of QT interval can occur with hypoglycaemia in an ambulatory setting in people with type 1 and type 2 diabetes treated with insulin. This highlights the potential proarrhythmic harms associated with hypoglycaemia.

Chapter 79 – Electrocardiographic Manifestations of Supernormal Conduction, Concealed Conduction, and Exit Block

Supernormal conduction, concealed conduction, and exit block are related phenomena of cardiac conduction. The first two terms are badly named although this is entirely understandable in view of the limited investigative techniques available at the time these terms were coined. Concealed conduction can cause both apparent supernormal conduction and exit block.

Inappropriate sinus tachycardia: focus on ivabradine.

Inappropriate sinus tachycardia (IST) is an incompletely understood condition, characterised by an elevation in heart rate (HR) accompanied by wide ranging symptoms in the absence of an underlying physiological stimulus. The condition often takes a chronic course with significant adverse effects on quality of life. Currently, there is no effective treatment for IST. Beta‐blockers, generally considered the cornerstone of treatment, are often ineffective and poorly tolerated. Ivabradine is a novel sinus node If ‘funny current’ inhibitor, which reduces the HR. It has been approved for the treatment of beta‐blocker refractory chronic systolic heart failure and chronic stable angina but more recently has shown promise in the treatment of IST. This review provides an overview of IST prevalence and mechanisms followed by an examination of the evidence for the role and efficacy of ivabradine in the treatment of IST.

Defibrillator Threshold Testing at Generator Replacement: Is it Time to Abandon the Practice?

Rapid improvements in implantable cardioverter-defibrillator (ICD) technology in recent years have spurred the debate of whether defibrillation threshold (DFT) testing at the time of implantation is required.1–3 DFT testing was traditionally the gold standard for ensuring electrical integrity, reliable sensing, and reliable defibrillation by the ICD. However, there are concerns regarding the potential for serious adverse events related to DFT testing such as circulatory arrest,1 myocardial ischemia,4 refractory ventricular fibrillation (VF),27 respiratory depression, central nervous system hypoperfusion,25,26 and thromboembolism.5 Moreover, several cohort studies have reported no difference in clinical outcomes associated with routine DFT testing.1,6–8 This was confirmed in the recent Shockless IMPLant Evaluation (SIMPLE) trial.32 In light of these emerging data, routine DFT testing at the time of new ICD implants has been abandoned by many physicians.3,10 In parallel, there has been a growing reluctance among physicians to perform routine DFT at the time of ICD generator replacement.11 However, data regarding DFT testing during new ICD implants may not be directly applicable to generator replacement because chronically implanted ICD leads may develop integrity issues over time.12,13 Although several reports have cautioned against the abandonment of DFT testing during generator replacement,14–16 the issue has been sparingly addressed in the existing literature.

Periprocedural Management of Novel Oral Anticoagulants During Atrial Fibrillation Ablation: Controversies and Review of the Current Evidence.

Oral anticoagulation (OAC) has been the cornerstone for the prevention of thromboembolic complications in patients with atrial fibrillation (AF) at significant risk of stroke. Catheter ablation is an established efficacious technique for the treatment of AF. Ameliorating the risk of stroke or transient ischaemic attack (TIA) in patients with AF undergoing ablation requires meticulous planning of pharmacotherapy. The advent of non-vitamin K oral anticoagulants (NOACs) has broadened the therapeutic scope, representing a viable alternative to traditional vitamin K antagonists (VKA) in non-valvular AF. Potential advantages of NOACs include greater pharmacokinetic predictability, at least comparable efficacy as compared to VKA and a superior haemorrhagic complication profile. However, robust evidence for the safety and efficacy of periprocedural NOAC use for AF ablation remains uncertain with a non-uniform clinical approach between and within institutions. The following review will summarise the current and emerging evidence on periprocedural management of NOACs in patients undergoing catheter ablation of AF. An overview of NOAC pharmacology will provide a foundation for the review of reversal agents in the context of catheter ablation of AF. The purpose of the review is to outline key studies and identify key areas for further critical research with the ultimate aim of developing evidence-based guidelines for optimal care.

Posterior cardiac compression from a large hiatal hernia—A novel cause of ventricular tachycardia

Large hiatal hernia (HH) can cause extensive posterior cardiac compression, including frequent compression of the basal inferior left ventricular (LV) wall, with such changes resolving post HH repair. We present the first case of ventricular tachycardia (VT) associated with HH-induced compression.

Tachycardia, Both Narrow and Broad Complex: What are the Mechanisms? How to Treat?

A 48-year-old male presented with a several week history of palpitations. He had no significant past medical or family history. Physical examination and echocardiogram were normal. His baseline electrocardiogram (ECG) is shown in Figure 1A. During palpitations, both a narrow and a broad complex tachycardia were documented (Figs. 1B and C). The broad complex tachycardia showed apparent atrioventricular (AV) dissociation. What are the mechanisms of the tachycardias? Should he receive an implantable cardioverterdefibrillator?

Atrial septal defect complicating cryoablation for atrial fibrillation during concomitant valve surgery

Cryoablative therapy for the treatment of atrial fibrillation (AF) is increasingly favoured due to its lower reported complication rate. We present the case of a 74 year old man presenting with an atrial septal defect (ASD) following cryoablation for AF which was performed concomitantly with mitral valve surgery. Our case demonstrates that loss of tissue integrity can occur even with cryoablation, which is reported to better preserve the underlying tissue architecture compared to other energy modalities.