[Electrophysiologic characteristics of the atrium during chronic atrial fibrillation in man].
OBJECTIVE
To evaluate the electrophysiologic characteristics of human atria during chronic atrial fibrillation.


METHODS
The study was performed in 24 patients who underwent low energy intracardiac atrial cardioversion for chronic atrial fibrillation before the procedure itself. No patients have been assuming antiarrhythmic drugs for a period of at least 5 half-lives of the drug. In 10 patients the possibility of local capture in several atrial sites (7 tested) by means of high-rate atrial pacing was evaluated. A Franz catheter for recording of monophasic action potential (MAP) and for atrial stimulation was positioned in the right atrium at a distance of 1 cm from a quadripolar catheter which was also positioned for the recording of the bipolar electrogram by the distal and proximal pairs and of the unipolar electrogram by the distal electrode. A decapolar catheter for shock delivery was positioned in the coronary sinus as well. In the remaining 14 patients an additional quadripolar catheter for His recording was positioned but atrial stimulation was not performed. Furthermore, recordings of the bipolar and unipolar electrograms were obtained in several sites and the correlation between MAP and bipolar electrogram morphology was evaluated. The existence of a difference in fibrillation cycle-length in different sites suggestive of a dispersion of refractory periods was also screened. Wells' and Waldo's classification was used for bipolar electrograms whereas MAP was classified into type 1 (regular), type 2 (partially irregular), and type 3 (totally irregular).


RESULTS
In 10 patients submitted to atrial stimulation, local capture was obtained in 37 out of 43 stimulation sites (86%). Local capture was more frequently obtained in the lateral wall than in other sites (p < 0.05). The capture was obtained only in type 1 and type 2 atrial fibrillation. In the remaining 14 patients a perfect correlation (100%) between type 1 and 3 atrial fibrillation and type 1 and 3 MAP respectively was observed. In type 2 atrial fibrillation the correspondence was lower (67%). Fibrillation cycle-length contemporary recorded in the 6 different atrial sites were significantly different in 8 patients out of 12 (67%) in whom a stable recording could be obtained in basal conditions.


CONCLUSIONS
1) In chronic atrial fibrillation an excitable gap allowing local capture is present in the majority of patients and in most atrial sites, at least in the right atrium. 2) The morphology of bipolar and MAP recordings are fairly correlated and they reflect the complexity and the degree of synchronization of the arrhythmia. 3) A dispersion of refractoriness seems to contribute to the maintainance of the arrhythmia.
Pandozi
C
C
Divisione di Cardiologia Ospedale S. Filippo Neri, Roma.
Bianconi
L
L
Villani
M
M
Castro
A
A
Toscano
S
S
Altamura
G
G
Jesi
A P
AP
Auriti
A
A
Gentilucci
G
G
Magris
B
B
Santini
M
M
D000200:Action Potentials / Q000502:physiology; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy; D002304:Cardiac Pacing, Artificial; D002908:Chronic Disease; D004554:Electric Countershock; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006325:Heart Atria / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012032:Refractory Period, Electrophysiological / Q000502:physiology
Caratteristiche elettrofisiologiche dell'atrio durante fibrillazione atriale cronica nell'uomo.