Electrophysiology Year in Review 2008: Technology Paving the Way for EPs

The year 2007 was heralded as the year of the three R’s: robotics, recalls, and reimbursement. While those topics were still echoed at the 2008 annual Heart Rhythm Society scientific sessions, the new zeitgeist was the continuing evolution of technologies facilitating complex electrophysiology procedures, thus paving the way for mainstream electrophysiologists to perform complex ablations. Atrial Fibrillation (AF) Technologies The past year was characterized by an increasing use in clinical practice of robotic technology. Approval of Hansen Medical's Sensei Robotic Catheter System in 2007, as well as the continuing interest with the Stereotaxis Niobe Magnetic System, remained hot topics among EPs.^1-5 Additionally, anticipation surrounded the U.S. release of Hansen Medical’s CoHesion™ 3D Visualization Module, which integrates 3D visualization with 3D robotic navigation. The year 2009 is expected to bring the 4-mm irrigation catheter for the Stereotaxis system, and broadening indications for remote systems, such as using them to perform ablation of ventricular tachycardia and to drive wires in interventional procedures such as biventricular pacemaker lead implantations. Among balloon technologies, cryo systems appear to be the most popular. However, long-term data are required to understand the role of this approach in managing atrial fibrillation patients. Balloon systems will most likely remain limited to paroxysmal patients. Endpoints for Catheter Ablation for Atrial Fibrillation We have come a long way in understanding the ideal procedural strategy for different subtypes of atrial fibrillation.^6-15 In a subset of paroxysmal patients, atrial pulmonary vein (PV) isolation could be sufficient. This group could be the target of balloon devices.^16,17 It is also clear that posterior wall ablation increases success rates in some of the paroxysmal patients and certainly in persistent and longstanding persistent AF. In the latter group, adjunctive lesions and ablation targets can increase success, at times, at the expense of extensive destruction.¹⁸ Whether ablation of more limited tissue driven by documentation of firing leading to AF is a better approach is out for debate. Promising New Antiarrhythmics for the Management & Prevention of AF Restoration of sinus rhythm by ablation without antiarrhythmic drugs (AADs) or cardioversion is not always possible. Therefore, room exists for improvement in drug-based treatments and strategies for AF. The Antiarrhythmics After Ablation of Atrial Fibrillation study (5A) assessed the use of AAD therapy for six weeks after ablation, and found it significantly reduces the incidence of recurrent AF and the need for cardioversion or cardiovascular hospitalization.^{19, 20} One of the drugs in late-stage development that could help usher in a new era for the management of AF is dronedarone. The ATHENA, ERIDIS and ADONIS trials have reported that dronedarone improves safety and significantly reduces the rate of cardiovascular hospitalizations and mortality.^20-25 The ongoing study comparing dronedarone to amiodarone (DYONISOS trial) may further provide guidance on the clinical use of this AAD.²⁶ Nevertheless, it is important to remember that patients on dronedarone have a 60% recurrence of AF/AFL within a 12-month follow-up. While both the ATHENA and the 5A trials investigated drugs in patients with established AF, there is also a marked effort to find primary preventions for AF. The Heart and Estrogen-Progestin study (HERS) showed that there is a positive link between statin use and the primary prevention of AF in postmenopausal women.²⁷Implantable Cardioverter Defibrillators (ICDs) The untimely and extremely tragic death of Tim Russert brought a heightened awareness of coronary artery disease and the underuse of ICDs for the prevention of sudden cardiac death (SCD). During the last decade, the focus of ICD trials has been prophylactic implantation of devices in high-risk patients for the prevention of SCD. In a study of 49,517 patients admitted to the hospital with a primary diagnosis of cardiac arrest who survived to hospital discharge, only 31% received a defibrillator.²⁹ ICDs are extremely underused in women and African Americans; they ultimately reap the same or better benefits than Caucasian males who receive ICDs.^30-32 The future of ICDs is to accurately identify patients with risk factors for SCD. It is imperative to break down barriers and encourage dissemination of ICD therapy to address this major public health issue.^33,34 Future research will focus on enhanced monitoring devices, better methods to reduce inappropriate shocks, and development of smaller devices with components and features allowing for more efficient and convenient care at implant and follow-up. Remote Monitoring of ICDs Remote monitoring of ICDs and CRTs has the potential to replace the traditional quarterly or semi-annual direct ambulatory device interrogations. These devices enable wireless remote interrogation and monitoring. With future technological improvements, a better understanding of the clinical implications, and economic benefits of telecardiology, we will be able to predict which patients need more aggressive care, resulting in fewer CHF hospitalizations.^35-37MRI Compatible Devices In the past, patients with devices were not able to undergo an MRI. However, there is now growing experience that MRI scanning at 1.5T is safe.³⁸ In addition, MRI-compatible pacemakers are being manufactured. Ventricular Tachycardia (VT) and Ventricular Fibrillation (VF) Ablation, and Imaging Advances Catheter ablation is a potentially powerful strategy for the treatment VT and VF.^39-45 However, even with an open irrigated catheter, VT can be suppressed in no more than 60-65% of patients. Epicardial ablations are being performed more frequently as a way to improve the success rates of these procedures. In addition, imaging modalities can be integrated with electroanatomical mapping systems.^46,47 Positron emission tomography (PET)/CT has been shown to be excellent in defining scar, and may obviate the need for voltage maps during VT ablations.⁴⁸ Integration of electroanatomical mapping and 2D intracardiac echocardiography is available, allowing real-time imaging of ventricular cardiac structures. Early human experience found that it is possible to create a 3D shell of the left ventricle, including a limited substrate map based on regional wall abnormalities, without the need to enter the left chambers.49 Future advances in VT ablation could include the use of a saline needle catheter for ablation and the use of 3D ultrasound, intraoperative 3D angiography (Dyna CT), and MRI for better understanding of the anatomy and visualization of the scar tissue.^50,51Conclusion This has been a hallmark year for advances in enabling technology. We believe the future of electrophysiology is to find ways to increase awareness and treatment of arrhythmias in the general population, and to continue on the path of technological innovations. Future innovations will increasingly allow every electrophysiologist to be a “rock star” to their patients, irrespective of their experience and/or manual skills.