Chance M. Witt

Recurrent dyspnea following multiple ablations for atrial fibrillation explained by the “stiff left atrial syndrome”

We present the case of a patient who underwent repeated ablations for atrial fibrillation and presented with recurrent dyspnea, elevated left atrial pressure with large V waves in the absence of mitral regurgitation. This case provides an example of “stiff left atrial syndrome” as has been described in patients with mitral valve replacement and only recently in patients with radiofrequency ablations for atrial fibrillation.

Outcomes After Implantable Cardioverter-Defibrillator Generator Replacement for Primary Prevention of Sudden Cardiac Death.

Background—The effectiveness of implantable cardioverter-defibrillators (ICDs) for primary prevention of sudden death in patients with an ejection fraction (EF) ⩽35% and clinical heart failure is well established. However, outcomes after replacement of the ICD generator in patients with recovery of EF to >35% and no previous therapies are not well characterized. Methods and Results—Between 2001 and 2011, generator replacement was performed at 2 tertiary medical centers in 253 patients (mean age, 68.3±12.7 years; 82% men) who had previously undergone ICD placement for primary prevention but subsequently never received appropriate ICD therapy. EF had recovered to >35% in 72 of 253 (28%) patients at generator replacement. During median (quartiles) follow-up of 3.3 (1.8–5.3) years after generator replacement, 68 of 253 (27%) experienced appropriate ICD therapy. Patients with EF ⩽35% were more likely to experience ICD therapy compared with those with EF >35% (12% versus 5% per year; hazard ratio, 3.57; P=0.001). On multivariable analysis, low EF predicted appropriate ICD therapy after generator replacement (hazard ratio, 1.96 [1.35–2.87] per 10% decrement; P=0.001). Death occurred in 25% of patients 5 years after generator replacement. Mortality was similar in patients with EF ⩽35% and >35% (7% versus 5% per year; hazard ratio, 1.10; P=0.68). Atrial fibrillation (3.24 [1.63–6.43]; P<0.001) and higher blood urea nitrogen (1.28 [1.14–1.45] per increase of 10 mg/dL; P<0.001) were associated with mortality. Conclusions—Although approximately one fourth of patients with a primary prevention ICD and no previous therapy have EF >35% at the time of generator replacement, these patients continue to be at significant risk for appropriate ICD therapy (5% per year). These data may inform decisions on ICD replacement.

Right ventricular pacemaker lead position is associated with differences in long-term outcomes and complications

Cardiac pacing from the right ventricular apex is associated with detrimental long‐term effects and nonapical pacing locations may be associated with improved outcomes. There is little data regarding complications with nonapical lead positions. The aim of this study was to assess long‐term outcomes and lead‐related complications associated with differing ventricular lead tip position.

The Inflammatory Hypothesis of Atrial Fibrillation: Diagnostic Marker, Therapeutic Target, or Innocent Bystander?

The majority of research published on treatment of atrial fibrillation (AF) in the past decade has focused on understanding how to perform electrophysiologic ablation better, faster, or more safely. Since demonstration of pulmonary vein isolation as an effective therapy for AF in the 1990s, improved catheters, mapping systems, and understanding of how to minimize procedural risk have substantially improved outcomes. However, there has been an almost insurmountable hurdle of “70–80%” in achievement of successful treatment of paroxysmal AF (and less so in persistent patients). While some studies quote higher numbers, they are often single-center experiences with variable methods of postablation monitoring. In recent years, there has been a renaissance of sorts in the study of AF, with researchers increasingly focused on the mechanisms of AF and trying to understand whether we can better characterize the disease at the patient level, rather than simply identifying the presence of the disease and initiating treatment. Focus on rotors, substrate-based ablation, and better identification of patients most likely to undergo a successful ablation have been some avenues to individualize treatment. Whether offering tests to better select patients most likely to respond to ablation, or identifying patients in whom alternative therapies (e.g., antiarrhythmic drugs, atrioventricular nodal ablation, or novel methods of autonomic modulation) would be preferable may offer the electrophysiologist a way beyond just treating the disease and take us back to treating the patient with the disease rather than simply the disease itself. However, a combination of evolutionary and perhaps revolutionary innovations is needed to achieve such improvements in our current approach to management of patients with AF. In publishing novel approaches—whether incremental advances in ablation, identifying unique methods of autonomic modulation, or improving imaging or biomarker approaches to better understanding the patient presenting with AF—we all seek to change the world in which we live realizing that there is yet a long road to travel. Along this vein, in this issue of the Journal, Yalcin et al. report the use of an inflammatory marker, galectin-3 (Gal-3) to predict the

Irreversible electroporation for the treatment of cardiac arrhythmias

ABSTRACT Introduction: Cardiac ablation is an established treatment modality for the management of patients with cardiac arrhythmias. Current approaches to cardiac ablation employ thermal based energy to achieve lesions (damage) within the heart. There are many shortcomings and limitations of thermal based approaches. Electroporation (DC energy) is a non-thermal alternative approach to ablation that has shown significant promise in animal studies. Areas covered: An extensive review of the literature on the application of electroporation for ablation (both cardiac and collateral cardiac tissue) was undertaken. This review explores irreversible electroporation as a cardiac ablation modality. Specifically, it focuses and explains the biophysics of electroporation, the limitations of current thermal based approaches and examines the current data published on electroporation cardiac ablation. Expert commentary: Electroporation is a fast-growing novel ablation modality that has many advantages over current thermal based approaches. Current research in animal models shows its can be safely and efficaciously applied to the heart. Although further research is required, electroporation represents an appealing option for the ablation cardiac arrhythmias.

Denervation of the extrinsic cardiac sympathetic nervous system as a treatment modality for arrhythmia

Denervation of the extrinsic cardiac sympathetic nervous system is a method of altering the autonomic tone experienced by the heart and vasculature. It has been studied and employed as a therapy for cardiac disease for decades. Currently, there is a high level of interest in using cardiac denervation for treatment of arrhythmias. This review describes the anatomy and physiology of the cardiac autonomic nervous system followed by a discussion of the mechanistic studies which provide a basis for the therapeutic use of sympathetic denervation. The clinical research supporting its use in human arrhythmias is then appraised, covering the standard indications, such as long QT syndrome, as well as future possibilities. Last, a detailed account of the methods for performing surgical cardiac denervation and percutaneous stellate ganglion anesthetic block is provided, including the complications of each procedure. An understanding of the anatomy and physiology of the cardiac autonomic nervous system along with the techniques of surgical denervation and percutaneous anesthetic block will allow the clinician to effectively discuss and implement these therapies.

Ventricular tachycardia secondary to abandoned epicardial pacemaker lead

Introduction Late complications from pacemaker leads are infrequent. The majority of lead-related issues, such as dislodgment and perforation, occur around the time of implant. Rarely, arrhythmias are triggered by the physical presence of the lead. We present the case of a patient with recurrent ventricular tachycardia (VT) precipitated by positional change and specific movements, and associated with a pacing lead placed 3 decades earlier.

Diagnosis of constrictive pericarditis obscured by hypertrophic cardiomyopathy: Back to basics

In this report, we describe the case of a 41‐year‐old man with hypertrophic cardiomyopathy presenting with right‐sided congestive heart failure symptoms. Noninvasive testing was suggestive, but non‐diagnostic for constrictive pericarditis (CP) and thus invasive hemodynamic catheterization was performed. The unique presence of both hypertrophic cardiomyopathy and constriction in this case led to lack of “modern” echocardiographic and invasive criteria for CP, based upon findings of enhanced ventricular dependence. However, classic hemodynamic criteria of early rapid filling with elevation and end‐equalization of diastolic pressures were present, and the patient ultimately received pericardiectomy with dramatic clinical improvement.

Intrapulmonary Vein Ablation Without Stenosis: A Novel Balloon-Based Direct Current Electroporation Approach.

Background Current thermal ablation methods for atrial fibrillation, including radiofrequency and cryoablation, have a suboptimal success rate. To avoid pulmonary vein (PV) stenosis, ablation is performed outside of the PV, despite the importance of triggers inside the vein. We previously reported on the acute effects of a novel direct current electroporation approach with a balloon catheter to create lesions inside the PVs in addition to the antrum. In this study, we aimed to determine whether the effects created by this nonthermal ablation method were associated with irreversible lesions and whether PV stenosis or other adverse effects occurred after a survival period. Methods and Results Initial and survival studies were performed in 5 canines. At the initial study, the balloon catheter was inflated to contact the antrum and interior of the PV. Direct current energy was delivered between 2 electrodes on the catheter in ECG‐gated 100 μs pulses. A total of 10 PVs were treated demonstrating significant acute local electrogram diminution (mean amplitude decrease of 61.2±19.8%). After the survival period (mean 27 days), computed tomography imaging showed no PV stenosis. On histologic evaluation, transmural, although not circumferential, lesions were seen in each treated vein. No PV stenosis or esophageal injury was present. Conclusions Irreversible, transmural lesions can be created inside the PV without evidence of stenosis after a 27‐day survival period using this balloon‐based direct current ablation approach. These early data show promise for an ablation approach that could directly treat PV triggers in addition to traditional PV antrum ablation.

EXTERNAL COOLING OF THE MYOCARDIUM SLOWS ELECTRICAL CONDUCTION AND TERMINATES ATRIAL FIBRILLATION

Background: Prompt termination of atrial fibrillation (AF) by implantable devices could improve symptoms and outcomes. However, electrical cardioversion is painful, making it impractical. Cooling of the myocardium may slow conduction and terminate AF without producing pain. Methods: Cooling was