Epicardial right atrial free wall mapping in chronic atrial fibrillation: Documentation of repetitive activation with a focal spread--a hitherto unrecognised phenomenon in man

BACKGROUND: Previous studies have shown that atrial fibrillation of recentonset in man is based on a varying number of simultaneouslypresent activation waves re-entering either themselves or eachother. In the present study, right atrial activation duringchronic atrial fibrillation in man was studied. METHODS AND RESULTS: In 16 patients with chronic atrial fibrillation multiple epicardialrecordings of 8 s each were made at the right atrial posteriorfree wall and at the appendage using a 20x35 mm electrode arraywith 56 bipolar measurement points. The preferable activationpattern of each recording and the propagation direction, cyclelength and conduction velocity of individual activation waveswithin each recording were determined. Activation was characterizedby unorganised activation with several simultaneously presentactivation waves: inconsistent preferable activation pattern(n=5), predominantly organised activation with either frequentepisodes of uniform activation; consistent preferable activationpattern (n=7) or frequent episodes of activation with focalspread; focal preferable activation pattern (n=4). Random re-entrywas frequently documented in recordings with the inconsistentpreferable activation pattern and less frequently in recordingswith the consistent and focal preferable activation pattern.Complete re-entry circuits were rarely documented. The medianfibrillation cycle length was 146, 159 (P<0·05) and165 ms (not significant) and the mean conduction velocity duringuniform activation was 64, 67 and 83 cm.s^–1 (not significant)in recordings with the inconsistent, consistent and focal preferableactivation pattern, respectively. CONCLUSIONS: During chronic atrial fibrillation in man, right atrial freewall activation ranges from disorganised activation with multipleco-existing activation waves to predominantly organised activationcharacterized by either uniform activation consistent with thepresence of large re-entry circuits or repetitive activationof unknown mechanism and focal spread.