PROLONGED AND FRACTIONATED RIGHT ATRIAL ELECTROGRAMS DURING SINUS RHYTHM IN PATIENTS WITH PAROXYSMAL ATRIAL-FIBRILLATION AND SICK SINUS NODE SYNDROME

Intraatrial catheter mapping of the right atrium was performed during sinus rhythm in 92 patients: Group I = 43 control patients without paroxysmal atrial fibrillation or sick sinus node syndrome; Group II = 31 patients with paroxysmal atrial fibrillation but without sick sinus node syndrome; and Group III = 18 patients with both paroxysmal atrial fibrillation and sick sinus node syndrome. Atrial electrograms were recorded at 12 sites in the right atrium. The duration and number of fragmented deflections of the atrial electrograms were quantitatively measured. The mean duration and number of fragmented deflections of the 516 atrial electrograms in Group I were 74 +/- 11 ms and 3.9 +/- 1.3, respectively. The criteria for an abnormal atrial electrogram were defined as a duration of greater-than-or-equal-to 100 ms or eight or more fragmented deflections, or both. Abnormal atrial electrograms were observed in 10 patients (23.3%) in Group I, 21 patients (67.7%) in Group II and 15 patients (83.3%) in Group III (Group II versus Group I, p < 0.001; Group III versus Group I, p < 0.001). The mean number of abnormal electrograms per patient with an abnormal electrogram was 1.3 +/- 0.7 in Group I, 2.5 +/- 1.9 in Group II and 3.5 +/- 2.5 in Group III (Group I versus Group II, p < 0.01; Group II versus Group III, p < 0.05). A prolonged and fractionated atrial electrogram characteristic of paroxysmal atrial fibrillation can be closely related to the vulnerability of the atrial muscle. The area of diseased atrial muscle in patients with both paroxysmal atrial fibrillation and sick sinus node syndrome was more extensive than that in patients with paroxysmal atrial fibrillation alone.