The most widely used classification system for antiarrhythmic drugs is a modification of the system proposed by Vaughan Williams. It classifies drugs according to their effects on action potentials in individual cells. Class I drugs block sodium channels responsible for the fast response in atrial, ventricular, and Purkinje tissues, thus depressing conduction velocity.
(Guest Authored by Roger Kersten, DO, FACC)
One of the major advances in the management of cardiac arrhythmias during the past 25 years has been the innovation of catheter ablation. Initially performed in the early 1980s, this technique may be attributed to the pioneering work of Dr. Melvin Scheinman.
Nonfluoroscopic three-dimensional mapping of the myocardium has been very helpful for isolating focal and nonfocal tachycardias. The technique is very similar to localization using the global positioning system. Using reference electrodes in the XYZ planes, one can identify the location of catheters and tachycardias within the heart.
(Guest Authored by Daniel Kersten)
To induce arrhythmias, a technique known as programmed electrical stimulation is performed. Programmed electrical stimulation uses standard pacing of the atrium or ventricle at a predetermined heart rate or cycle length with the placement of premature extrastimuli. The premature extrastimuli start at a preset interval and get progressively more premature.
Atrial fibrillation is one of the most common arrhythmias. According to the most recent American Heart Association/American College of Cardiology/Heart Rhythm Society Atrial Fibrillation Guidelines, approximately 2.7 million people in the United States are living with atrial fibrillation. This number is expected to double in the next 25 years.
In AV node reentrant tachycardia, the atrial electrogram is typically encompassed within or at the tail end of the QRS complex. In this chapter, we show an example that demonstrates baseline recordings in a patient who has AV node reentrant tachycardia. In this patient, the AH and HV intervals are normal.
Atrial tachycardia is a common atrial arrhythmia seen in individuals who have valvular disease or other structural heart disease; it is sometimes seen in people who have a structurally normal myocardium as well. Less common than atrial fibrillation and AV node reentrant tachycardia, it is probably more common than AV-reciprocating tachycardias (those that use an accessory pathway).
Typical atrial flutter is a macro-reentrant tachycardia. It differs from an atrial tachycardia (which emanates from a discrete focus) by its continuous electrical activity around a relatively large anatomic structure, such as the right tricuspid valve. It is principally a right atrial disease, but can occasionally occur in the left atrium or around surgical scars.