Bradley P. Knight, MD, FACC, FHRS
Chester C. and Deborah M. Cooley Distinguished Professor of Cardiology
Director of Cardiac Electrophysiology
Bluhm Cardiovascular Institute of Northwestern
Feinberg School of Medicine
This supplement to The Journal of Innovations in Cardiac Rhythm Management is focused on Cardiac Electrophysiology (EP) Fellows Education. As the Guest Editor for this special edition, I invite you to read, critique, and enjoy this outstanding content. Both the sponsor, Biotronik, Inc, and Innovations in Cardiac Rhythm Management should be commended for continuing to place EP fellowship training and education as a top priority at both institutions.
There are certain topics that absolutely must be understood by end of one's training in cardiac electrophysiology. One such topic is what to do at the time of defibrillator implantation when the defibrillator fails to do its job. There was a time, when transvenous defibrillator systems were first being implanted, that defibrillation testing was performed using an External Cardioverter Defibrillator (ECD) rather than the implantable device itself. The lead was attached to this large, non-sterile device using specialized high-voltage connector cables, cables much sturdier that those commonly used to test pacing thresholds with a Pacing System Analyzer (PSA). If the patient could not be defibrillated using the ECD, the package containing the ICD generator was never opened. Only since biphasic waveforms, active cans, and rapid charge times were available did device-based testing become reliable and predictable.
Still, however, it can be difficult to defibrillate a patient with a modern transvenous ICD in the Electrophysiology lab. In this supplement, Dr. Sumeet Mainigi discusses defibrillation testing and the management of high defibrillation energy requirements. Although there are several legitimate arguments against routine defibrillation threshold testing with contemporary devices, it remains a critical concept. Every electrophysiologist needs to know the noninvasive and invasive options that can lower the defibrillation threshold. Interestingly, as implantable defibrillator technology evolves further, with the recent availability of the IS-4 defibrillator connector that limits one's ability to invasively address the problem of high defibrillation energy requirements, and the potential for technologies based on completely new approaches, such as a totally subcutaneous defibrillator, this topic could paradoxically gain relevance.
On the opposite end of the ventricular arrhythmia spectrum are patients with idiopathic ventricular tachycardia (VT), who very rarely need defibrillator therapy. Although, these patients are usually at a very low risk for cardiac arrest, they are often highly symptomatic and refractory to medical therapy. Catheter ablation has been an excellent treatment option for the most common form of idiopathic VT, arising from the right ventricular outflow tract (RVOT), for the past 15 years. During the early years of ablation for RVOT VT, however, the expectations for success were low relative to other arrhythmias such as AV nodal reentry. Patients were commonly told that the likelihood of successful ablation for VT that appeared to be arising from the RVOT was about 80%. In the cases when ablation was unsuccessful, it was assumed that the site of origin was epicardial and beyond the reach of conventional catheter ablation.
Since those early years, much has been learned from mapping and ablating outflow tract tachycardias that has lead to a better understanding of the sources of these arrhythmias, and higher success rates with ablation. In this supplement, one of the contributors to our better understanding, Dr. David Callans, comprehensively reviews the mechanisms of various types of idiopathic VTs, localization techniques using the electrocardiogram, and modern localization approaches that include activation mapping of the aortic valve cusps and middle cardiac vein to tackle challenging cases that were once considered refractory to ablation.
During EP training in the mid-1990s, the field was well established and growing, but there was a limit to the types of procedures and technologies that needed to be learned. Heart rhythm management was primitive compared with what it is today. At that time, commonly used drugs included procainamide and bretylium, patients who needed dual-chamber pacing and defibrillator therapy needed to have two separate devices implanted, diagnostic EP testing for risk stratification of sudden death accounted for a large proportion of EP procedures, and the target of most ablation procedures was an accessory or slow atrioventricular nodal pathway. Procedures were often done using a simple stimulator and paper recording system. Today, EP fellows are required to learn much more: how to safely use newer antiarrhythmic drugs and anticoagulants, and how to master coronary sinus lead implantation, transseptal catheterization, pericardial access for epicardial ablation, catheter ablation for atrial fibrillation, and the use of advanced mapping systems.
Despite having to master a more sophisticated set of skills than twenty years ago, EP fellows must do this in the same amount of time, and in a very different training environment. Although many fellows spend two years training in EP, the Accreditation Council for Graduate Medical Education fellowship for EP has remained officially a one-year program. This continues to lead to challenges in getting enough experience in a limited amount of time. In addition, duty hours have been restricted during that one-year experience and documentation requirements have been increased.
As we try to meet these challenges, a very important source of support for EP fellowship trainees continues to come from the health-care industry. Industry-sponsored EP fellow educational programs that are supported by manufacturers of implantable devices and ablation tools are invaluable. These programs continue to avoid promotional activity, contain content that is generated and controlled by physician speakers, and take advantage of animal and training facilities that are difficult and expensive to reproduce at academic medical centers.
Industry sponsorship of this special edition to Innovations in Cardiac Rhythm Management is another example of a productive and legitimate relationship between medical education and industry. We must continue to be grateful for these positive interactions, and defend such activities at a time when any relationship between a physician and a company is often assumed to be illegitimate.