SASEAP 2002 Proceedings

Basic Electrophysiology Sgt. Albert Paul, CVIS Walter Reed Army Medical Center Washington, DC My opening lecture at SASEAP 2002 was on Principles of Electrophysiology Studies. This talk was designed to give beginners in the field of electrophysiology a base on which to expand their knowledge during the rest of the conference. It also allowed those more experienced professionals among us a chance to review the basic principles that are important for success in the EP lab. The anatomy of the specialized conduction system was discussed. Special attention was paid to the anatomy and physiology of the atrioventricular node, as an understanding of conduction through this structure is vital to an appreciation of the methods and purposes of the programmed electrical stimulation that is performed in the EP lab. Fluoroscopic images of catheter placement during a typical EP study were also presented and discussed. Next, we talked about the normal intervals that are measured during an EP study. The programmed electrical stimulation that is performed at Walter Reed Army Medical Center and most other institutions was also presented. These tests include sinus node recovery time, rapid atrial pacing, rapid ventricular pacing, atrial extra-stimulus, and ventricular extra-stimulus. Currently working as a Cardiovascular Invasive Specialist and Electrophysiology Technician at Walter Reed Army Medical Center, Albert Paul has been active in the field of Cardiology for over 8 years. Advanced Electrophysiology Kamron Y. Benfield, PA Wake Forest University Baptist Medical Center Raleigh, North Carolina This lecture assumes the attendee has at least a basic knowledge of cardiac electrophysiology, the EP study, and selected arrhythmias, including bradyarrhythmias, arterioventricular conduction disturbances and supraventricular tachycardias. Bradycardia sinus node dysfunction, how to test for it and its implications were discussed first. Bradycardia-Tachycardia syndrome is the most common form of symptomatic sinus node dysfunction and is associated with the highest incidence of syncope. Disturbances of atrioventricular conduction were examined next. This included an explanation linking the site of block to the degree of block and what the significance is at each level of block. The different parts of the EP study used to evaluate atrioventricular conduction were discussed. Selected supraventracular tachycardias were explored, including atrioventricular nodal reentry tachycardia, AV reciprocating tachycardia, atrial fibrillation and flutter. A detailed explanation of AVNRT, ORT and ART was given, including tests used during the EP study used to differentiate among the three and also rule/out atrial tachycardias. It was explained that atrial flutter has been reclassified into the following system: Typical atrial flutter is any reentrant rhythm, which travels up the right atrial septum and then down the right atrial free wall, previously called counterclockwise. Reverse typical atrial flutter uses the same circuit but travels in the opposite direction, previously called clockwise. Left atrial flutter is any rhythm confined to the left atrial, which is at the rate of atrial flutter. Incisional atrial flutter is a reentry rhythm around an incisional line of block in the rate range for atrial flutter. Atypical atrial flutter is any reentrant atrial rhythm in the rate range for atrial flutter not described above. Typical atrial flutter was demonstrated via cadaver heart sections and then the concept of block was introduced and displayed. Typical atrial flutter can be eliminated by a linear radiofrequency lesion in the isthmus between the tricuspid annulus and the inferior vena cava. Atrial fibrillation was discussed as to classification and ablation therapy, which led to a brief overview of EP mapping systems. Kamron Benfield is a Physician s Assistant at the Dept. of Cardiology and EP Lab at Wake Forest University Baptist Medical Center in Winston-Salem, North Carolina. Re-Entrant Tachycardia Richard G. Sheahan, MD University of North Carolina-Chapel Hill Chapel Hill, North Carolina Reentrant tachycardia. Reentrant tachycardia is one of the most common mechanisms for supraventricular tachycardia (SVT). Critical criteria are required to facilitate the presence of reentrant tachycardias. Two pathways (or myocardial tissue) with different conduction properties (fast and slow), different repolarization periods or intervals (faster or slower recovery), and a critically timed initiating trigger (premature atrial or premature ventricular complex) are required in patients presenting with reentrant tachycardias. Atrioventricular nodal reentrant tachycardia. Atrioventricular nodal reentrant tachycardia (AVNRT) is one of the most common reentrant tachycardias. In AVNRT, both a fast and a slow pathway are present in or close to the AV node. During sinus rhythm, a normal impulse conducts more rapidly over the fast pathway than the slow pathway. Once the impulse has conducted over the fast pathway, the tissue becomes refractory. Because of the slower conduction over the slow pathway, the same impulse reaches the AV node when it is refractory. The impulse just stops. It is important to remember that the recovery or repolarization is shorter in the slow pathway than in the fast pathway. However, when a critically timed premature atrial complex occurs at a time when the fast pathway is refractory, antegrade conduction can occur over the slow pathway. The slower conduction allows further time for the fast pathway to recover. Once the impulse reaches the AV node and the fast pathway has recovered, an impulse can simultaneously conducts antegradely over the AV node and retrogradely over the fast pathway. A single beat is called an AV nodal echo beat. Reentrant tachycardia occurs when the retrograde conduction from the fast pathway activates the atrium with antegrade conduction over the slow pathway, retrograde over the fast pathway, repeating the sequence over and over again until the tachycardia terminates. Wolff-Parkinson-White syndrome or Concealed Accessory Pathway. In patients with atrioventricular reentrant tachycardia (AVRT), there is an additional pathway, but the basic concepts are similar. In AVRT, conduction over the accessory is similar to the fast pathway, and conduction over the AV node is equivalent to the slow pathway from the previous example. In AVRT, a critically timed premature ventricular complex may occur when the AV node is refractory, but retrograde conduction over the accessory pathway can occur. This activates the atrium. The additional time allows the AV node to recover now there is antegrade conduction over the AV node, which activates the ventricules. The delay in conduction over the AV node (decremental conduction) allows the accessory pathway additional time to recover. Conduction can then occur over the accessory pathway, and the sequence is repeated. This is know as orthodromic tachycardia. In patients with Wolff-Parkinson-White syndrome, anterograde conduction over the accessory pathway and retrograde conduction over the AV node (VA nodal conduction) can occur leading to antidromic tachycardia. Patients with isthmus dependent atrial flutter do not have a discrete pathway. Conduction slows as the impulse passes over the isthmus, and conducts faster over the remainder of the circuit within the right atrium. A linear ablation through the isthmus between the tricuspid valve and the inferior vena cava can successfully terminate the circuit and prevent atrial flutter recurrences. Radiofrequency ablation of the slow pathway or the accessory pathway respectively removes a critical limb of the circuit, and therefore provides a curative approach for both reentrant tachycardias. Syncope Douglas Beinborn, MA, RN Mayo Clinic, Rochester, Minnesota Syncope is defined as a temporary interruption of cerebral perfusion manifested by a loss of consciousness followed by spontaneous recovery. Syncope affects 30-50% of the general population during their lifetime. This accounts for 3% of all emergency room visits and between 2-6% of all hospital admissions. There are multiple ways to differentiate syncope. One way is to define which patients are at high risk versus low risk. Syncope patients at high risk include those with previous myocardial infarctions, left ventricular ejection fractions of