ATRIAL ELECTROPHYSIOLOGICAL FEATURES IN PATIENTS WITH WOLFF-PARKINSON-WHITE AND ATRIAL-FIBRILLATION - ABSENCE OF RATE ADAPTATION OF INTRAATRIAL CONDUCTION TIME PARAMETERS

Clinical electrophysiology has not yet clearly defined atrial features that can predict spontaneous occurrence of atrial fibrillation (AF). The aim of this work was to identify atrial electrophysiological featu res that can distinguish Wolff-Parkinson-White patients with spontaneo us AF from those without this arrhythmia. Sixty-nine patients with Wol ff-Parkinson-White were divided into three groups: group I (16 patient s) with spontaneous AF; group II (35 patients) with reciprocating tach ycardia but not AF; and group III (18 patients) asymptomatic without d ocumented arrhythmias. Atrial effective refractory periods (ERPs) and intraatrial conduction times in response to premature extrastimuli wer e analyzed. The latter were evaluated as She A,A, interval min us the correspondent S1S2 interval (A(1)A(2)-S1S2), S(2)A(2) and the interval A(1)A(2) following the shortest S1S2 producing atrial activation (FRP '). All the parameters have been evaluated in two atrial sites and at two atrial pacing cycle lengths (600 and 400 ms). For all the paramete rs, the difference (''gradient'') was calculated between the values of the same parameter measured at the atrial pacing cycle length of 600 ms and that found at the atrial pacing cycle length of 400 ms in the s ame recording site in each patient was calculated. Atrial ERP did not differ significantly in the three groups. Intraatrial conduction param eters, evaluated in the high right atrium (HRA), were longer when meas ured at an atrial pacing of 400 ms and showed a lack of rate adaptatio n in patients with spontaneous AF. In group I patients in particular, FRP' became longer with the increase of atrial rate, while in groups 2 and 3, it usually shortened. The mean gradient of HRA FRP' was -15.0 +/- 19 ms in group I as compared to 5.7 +/- 13 ms in group II and 6.4 +/- 13 ms in group III (P < 0. 001); sensitivity, specificity and nega tive predictive value of a negative gradient in the identification of patients with spontaneous AF, were, respectively, 83%, 75%, and 93%. P atients from groups 2 and 3 did not differ in any of the analyzed para meters. Patients with Wolf-Parkinson-White and spontaneous AF showed p rolonged intraatrial conduction times and a different behavior in resp onse to modification of heart rate.