Implantable cardioverter defibrillators in diabetics: efficacy and safety in patients at risk of sudden cardiac death

Diabetes mellitus is a major risk factor for arrhythmogenesis and is associated with a two-fold increase in all-cause mortality and a four-fold increase in cardiovascular mortality including sudden cardiac death when compared with nondiabetics. Implantable cardioverter defibrillators (ICD) have been shown to effectively reduce arrhythmic death and all-cause mortality in patients with severe myocardial dysfunction. With a high competing risk of nonarrhythmic cardiac and noncardiac death, survival benefit of ICD in patients with diabetes mellitus could be reduced, but the subanalysis of diabetic patients in randomized clinical trials provides reassurance regarding a similar beneficial survival effect of ICD and cardiac resynchronization therapy in diabetics, as observed in the overall population with advanced heart disease. In this article, the authors highlight some of the clinical issues related to diabetes, summarize the data on the efficacy of ICD in diabetics when compared with nondiabetics and discuss concerns related to ICD implantation in patients with diabetes.

Utility of unipolar recordings for complex Wolff–Parkinson–White ablation

Radiofrequency ablation has been shown to be a safe and effective treatment strategy for the management of symptomatic patients with Wolff–Parkinson–White syndrome. It is supported by a success rate of 95% and a recurrence rate of less than 5%. However, ablation of accessory pathways can be challenging at times. The causes for failure can be grouped into three categories – unusual location of the pathway, technical difficulties in delivering the ablation and localization error [1]. In this case report we are reporting a case of a young male who presented to us with symptomatic Wolff–Parkinson–White syndrome with two failed prior ablations at another institution. This case illustrates the importance of knowing accurate localization and course of the accessory pathway by utilizing the unipolar and bipolar electrograms simultaneously during radiofrequency ablation.

Abstract 198: Noninvasive Approach Assessing Atrial Mechanics and Serum Biomarkers of Collagen Turnover Provides a Surrogate for Fibrosis and Atrial Fibrillation

Introduction: Atrial fibrosis alters myocardial electrophysiological properties, increasing susceptibility to postoperative atrial fibrillation (PoAF); however, its estimation is problematic. We hypothesized that a noninvasive approach using history of AF (HxAF), LA mechanics and serum biomarkers of collagen turnover provides a surrogate for the extent of interstitial atrial fibrosis to identify patients at risk for PoAF.

Methods: In patients undergoing cardiac surgery from April-Dec 2013, concentrations of biomarkers reflecting collagen synthesis/degradation and extracellular matrix remodeling were determined in serum from preoperative blood using an enzyme-linked immunosorbent assay, and echocardiographic evaluation was performed using M-mode, 2D, Doppler and 3D speckle tracking.

Results: Of 66 patients (68 ±11 y, 67% men), 15 had HxAF and 11 of 51 with no HxAF (22%) developed new onset PoAF. In patients with HxAF, biomarkers for collagen turnover were elevated (Fig A) and correlated with a reduction in LA ejection fraction and global and regional relaxation of the LA wall (p=0.01, Fig B). In patients with no HxAF, procollagen type III (PIIINP) was significantly different in those who developed PoAF (p=0.01) and correlated with reduction in contractility in the posterior LA roof (p=<0.001) with a prolonged time to peak end-diastolic volume (p=0.03). LA size or ventricular structure and function were not different between groups.

Conclusion: Surrogate serum and imaging biomarkers correlate with the substrate abnormality that promotes AF. These results need to be validated in larger cohorts to assess the power of these parameters in predicting new onset PoAF.

Polymorphic ventricular tachycardia--part II: the channelopathies

In this article, we explore the clinical and cellular phenomena of primary electrical diseases of the heart, that is, conditions purely related to ion channel dysfunction and not structural heart disease or reversible acquired causes. This growing classification of conditions, once considered together as "idiopathic ventricular fibrillation," continues to evolve and segregate into diseases that are phenotypically, molecularly, and genetically unique.

Abstract 038: A Novel Histology Based Classification System to Identify Patients at Risk for Postoperative Atrial Fibrillation

Postoperative atrial fibrillation (PoAF) is a common complication in up to 40% of patients after cardiac surgery, increasing morbidity, hospital stay and costs. The myocardial substrate underlying PoAF is not fully characterized. The objective was to assess the impact of atrial fibrosis on incident AF and define the fibrosis threshold level predictive of PoAF.

Methods: Right atrial appendages removed from patients undergoing elective CABG with no history of AF or class III/IV heart failure were used to characterize the ratio of collagen to myocardium (Masson’s trichrome; NIH ImageJ software; Fig A), which was correlated with incident AF. Percentage burden of fibrosis predictive of PoAF with high sensitivity and specificity was determined by ROC curve.

Results: Of 28 patients (67±10 years, 64% males), 15 had PoAF. There were no age, gender or comorbidity differences between groups. Compared to the group that remained in sinus rhythm, patients with PoAF had a significantly higher ratio of extracellular collagen to myocardium (45±16% vs. 5±4%, p <0.001; Fig B). A threshold ratio of 12.7% collagen to myocardium (ROC area under the curve 0.997; z statistic 137; P<0.0001) with 96% sensitivity and 97% specificity identified those with PoAF (Fig C). A classification system based on histological extent of atrial fibrosis is proposed for identifying patients at risk for PoAF (Fig D).

Conclusion: Ongoing studies will confirm the predictive value of this new classification system for identifying the atrial substrate predisposing PoAF and correlate with preoperative cardiac imaging and circulatory serum biomarkers to provide a novel noninvasive tool to stratify patients at risk for PoAF.

Left Atrial Anatomy in Patients Undergoing Ablation for Atrial Fibrillation

Background: Left atrial anatomy is highly variable, asymmetric, irregular and three-dimensionally unique. This variability can affect the outcome of atrial ablation. A catalog of anatomic varieties may aid patient selection and ablation approach and provide better tools for left atrial ablation. Methods: We analyzed computed tomography scans from 514 patients undergoing left atrial ablation. Images were processed on Advantage Windows with CardEP™ software (GE Healthcare, Waukesha, WI). Measurements of pulmonary vein (PV) ostial size along the long and short axes were made using double oblique cuts, and area of the ostia was calculated. Results: Patients with 2 left (LPV) and 2 right PVs (RPV) (62.6%), 2 LPVs and 3 RPVs (17.3%) and 1 LPV and 2 RPVs (14.2%) made up the three most common variants. In the 2-LPV/2-RPV anatomy, the ostial size and area of the RPVs were larger than their corresponding LPVs (p<0.001), and the ostial size and area of the superior PVs were larger than their corresponding inferior PVs (p<0.001). In the 2-LPV/3-RPV anatomy, the total area of the RPVs was larger than the total area of the LPVs (p<0.001). In the 1-LPV/2-RPV anatomy, the ostial size of the left common PV was larger than either right PV (p<0.007). However, the total area of the RPVs was larger than the area of the left common PV (p<0.002). The left common PV was also larger than any of the left veins in any of the other anatomies. The total PV area between the three most common anatomies was not significantly different. Conclusions: More than 37% of patients have a left atrial anatomy other than 2 left and 2 right PVs. This data may help in designing approaches for left atrial ablation, tailoring the procedure to individual patients and improving ablation tools.

Repolarization syndromes

Repolarization syndromes, including early repolarization, Brugada, and short and long QT, have been implicated increasingly as causes of sudden cardiac death (SCD) despite no obvious mechanical cardiac abnormalities. So-called idiopathic ventricular fibrillation is now often reassigned to one of the aforementioned entities. Underlying causes are diverse; genetic mutation has been proven in many but not all cases. Although high-risk individuals generally can be identified, most of the potential victim pool is still unknown and cannot be discovered at this time. Awareness of these entities' existence, knowledge of family history, and 12-lead electrocardiography are the initial steps toward preventing SCD in this population. Underlying mechanisms for ventricular tachycardia/fibrillation in such individuals include phase 2 reentry, early after depolarization, and vortex reentry. For the time-being, although most forms of long QT syndrome can be treated with β-blockers, an implantable cardioverter-defibrillator remains the only definitive therapy for the prevention of arrhythmic death among high-risk populations.

Left ventricular pacing in right ventricular cardiomyopathy: blessing or blunder?

Arrhythmogenic right ventricular dysplasia (ARVD) predominantly involves the right ventricle, and myocardium is progressively replaced by fat and fibrous tissue in the apex, base, and outflow tract regions. This pathology, and the progressive nature of the disease, poses special challenges for implant and subsequent appropriate functioning of an implantable cardioverter-defibrillator. This case report describes a solution to problems during lead placement in patients with ARVD.

A Prospective Comparison of Cardiac Imaging Using Intracardiac Echocardiography With Transesophageal Echocardiography in Patients With Atrial Fibrillation

Background—

The Intracardiac Echocardiography Guided Cardioversion Helps Interventional Procedures study evaluated the concordance of intracardiac echocardiography (ICE) with transesophageal echocardiography (TEE) in patients with atrial fibrillation (AF).

Methods and Results—

Patients with AF undergoing right heart catheterization underwent left atrium (LA) and interatrial septal (IAS) imaging by TEE and ICE. A blinded comparison of the 2 modalities was performed at a core laboratory. Ninety-five patients aged 58±12 years completed the study. The LA was profiled in all patients with both techniques, and concordance for image quality was 96%. LA appendage (LAA) imaging was achieved in 85% with ICE and 96% with TEE. There was no difference in the presence of spontaneous echo contrast between ICE and TEE during LA imaging, but there was a trend toward a greater incidence in the LAA with TEE ( P =0.109). Intracardiac thrombus was uncommonly seen (TEE, 6.9%; ICE, 5.2%). The concordance for the presence or absence of thrombus was 97% in the LA and 92% in the LAA, but the latter was detected more frequently with TEE. IAS imaging was achieved in 91% with ICE and in 97% with TEE ( P =0.177). Concordance for patent foramen ovale and atrial septal aneurysms was 100% and 96%, respectively. A negative ICE examination was associated with absence of dense echo contrast or thrombus on TEE in 86%.

Conclusions—

This study provides validation for the use of ICE for LA and IAS imaging. ICE imaging was less sensitive compared to TEE for LAA thrombus identification.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00281073.

A case of flecainide-induced hyponatremia

We present a case of flecainide-induced hyponatremia in a 67-year-old woman who was treated for paroxysmal atrial tachycardia. She developed dizziness after starting flecainide and was found to be hyponatremic with a sodium level of 122 mmol/L (decreased from 136 mmol/L). Work-up failed to reveal other causes of hyponatremia. She was not on diuretics, laxatives, or herbal medications. After discontinuation of flecainide, her symptoms and sodium levels improved. Hyponatremia is a previously unrecognized entity as an adverse effect of flecainide. We will discuss the clinical presentation, lab findings, and a possible explanation for this patient's unusual reaction to flecainide.

Incessant interfascicular reentrant ventricular tachycardia as a result of catheter ablation of the right bundle branch: case report and review of the literature

A 72-year-old woman developed incessant interfascicular (IF) ventricular tachycardia immediately after successful right bundle branch (RBB) catheter ablation for the treatment of sustained bundle branch reentrant tachycardia. Catheter ablation of the left bundle branch and the left anterior fascicle was successful in eliminating the tachycardia (in 2 different sessions). This report discusses the direct link between the creation of an RBB block and the development of IF tachycardia, in our case, and in prior cases of IF reentry reported in the literature.

Pacing lead implantation without live fluoroscopy: feasibility of acute success in the live canine model

INTRODUCTION

Fluoroscopic visualization for transvenous pacing lead placement necessitates lead shielding to minimize radiation exposure. An electromagnetic (EM) navigation system that integrates real-time intracardiac tracking within an anatomic navigation environment may provide an effective alternative for lead delivery that obviates live fluoroscopy. We assessed feasibility of pacing lead implantation with electromagnetic tracking guided solely by radiographic virtual navigation and compared this to fluoroscopy-guided implants in a canine model.

METHODS

Seven mongrel dogs with normal hearts were randomized to 47 pacing lead placements in the right atrium (RA) or right ventricle (RV) guided by single-plane fluoroscopy, or an experimental EM navigation system guided by registered fluoroscopic snapshots obtained before implant (EMN). Ability to achieve successful lead delivery acutely was assessed, and pacing parameters as well as fluoroscopy and implant times were measured. Means were compared using a paired t-test.

RESULTS

All lead delivery attempts were acutely successful. One atrial lead dislodged with EMN, resulting in 46 successful pacing attempts. There was no statistical difference in pacing parameters and time for lead placement between the approaches (EMN vs fluoroscopic navigation [mean +/- SD]: RA threshold 1.15 V +/- 0.98 V vs 1.95 V +/- 0.98 V [P = NS], RV threshold 1.18 V +/- 0.58 V vs 1.42 V +/- 0.63 V [P = NS], implant time 4:38 +/- 2:37 minutes vs 4:44 +/- 2:38 minutes [P = NS]). No live fluoroscopy was required for EMN implants.

CONCLUSION

Pacing lead placement with an EM system guided by preprocedural fluoroscopic views is feasible and comparable to fluoroscopic navigation, and avoids the use of live fluoroscopy.