Evaluation of atrial refractoriness and atrial fibrillation inducibility immediately after internal cardioversion in patients with chronic persistentatrial fibrillation

Objective: To prospectively evaluate right atrial refractoriness and sustai ned atrial fibrillation (AF) inducibility at programmed electrical stimulat ion in two groups of patient: a series of patients with chronic persistent AF, studied immediately after successful low energy internal atrial cardiov ersion, and a group of control patients without history of supraventricular arrhythmias. Patients: Nineteen patients with chronic persistent AF (mean AF duration 11 +/- 10 months, range 2-61 months) submitted to successful internal low ene rgy atrial cardioversion in fully conscious state and 11 control patients w ithout history of supraventricular arrhythmias. Methods: An electrophysiological evaluation was performed to measure atrial refractoriness and AF inducibility, by delivering single atrial extrastimu li in high right atrium, at decremental coupling, during spontaneous sinus rhythm and after 8 beats at 600, 500, 400 and 330 ms cycle length. If susta ined AF was induced the protocol was terminated. Results: During programmed atrial stimulation sustained AF was induced in 8 out 19 (42%) of the AF patients but in none of the control group. Atrial e ffective refractory period was significantly shorter in AF patients compare d to controls both at basic cycle length, at 600 ms, 500 ms and 400 ms cycl e length, meanwhile no statistically significant differences were found at 330 ms cycle length. An altered relationship between atrial effective refra ctory period and cycle length was found in AF patients compared to controls : the slope of linear correlation slope was significantly lower in AF group than in controls (0.04 +/- 0.07 vs 0.17 +/- 0.10, p < 0.002). Conclusions: Marked abnormalities of atrial refractoriness and of its heart rate relationship are observed after internal cardioversion of chronic per sistent AF in humans and these abnormalities are associated with an high vu lnerability to AF. These observations may explain the high risk of AF recur rences in the early phases following successful cardioversion. In this scen ario antiarrhythmic drug therapy seems to be mandatory for reducing arrhyth mia relapses.