Catheter mapping of spontaneous and induced atrial fibrillation in man

The clinical electrophysiologic study of atrial fibrillation [AF] has recently progressed from static characterization of the substrate to the dynamic investigation of both induced and spontaneous AF in man. Prior studies have demonstrated inhomogeneity and greater dispersion of atrial refractoriness in patients with AF, but recently atrial electrical remodeling with consequent abbreviation of atrial refractory periods has also been reported. Yet further experimental observations have suggested the existence of additional arrhythmogenic mechanisms for certain AF subsets. These include studies that have demonstrated a stable atrial "flutter" circuit in one atrium with fibrillatory conduction or a "focal" atrial tachyarrhythmia arising commonly in the left atrium. Efforts at catheter mapping of AF are now in progress. New mapping techniques and novel devices are currently being employed. We have performed catheter mapping simultaneously in right and left atrial sites at onset and during sustained pacing-induced and spontaneous AF in patients with ischemic and/or hypertensive heart disease. Atrial premature complexes that initiated spontaneous AF typically had coupling intervals ranging from 260 to 400 ms and most frequently arose in the crista terminalis, right atrioventricular junction or superior left atrium. AF at onset showed discrete electrograms at virtually all right and left atrial regions mapped and the region of earliest atrial activation during AF was in close proximity to the premature complexes in over 90% of patients. The regional atrial activation sequence for the first 10 AF beats demonstrated stable or unstable patterns in individual patients. In contrast to spontaneous AF, the initial arrhythmia of induced AF was seen to have a significantly different site of earliest atrial activation but similar discrete electrograms in different atrial regions. However, as with spontaneous AF, the site of extrastimulus delivery was in close proximity to the first induced beat. We conclude that regional catheter mapping of AF is feasible and safe in man and organized electrical activity is frequently observed at AF onset in patients with heart disease. Both right and left atrial regions can be the source of atrial premature complexes and at the onset of spontaneous AF. Induced AF may have differing activation patterns than spontaneous AF but both demonstrate earliest activation in proximity to the initiating atrial premature complex. These findings may help explain therapeutic benefits of right and left atrial interventions and pacing therapies in AF.