Prevalence of conduction delay of the right atrium in patients with SSS: implications for pacing site selection.
OBJECTIVE
To evaluate the prevalence of severe right atrial conduction delay in patients with sinus node dysfunction (SND) and atrial fibrillation (AF) and the effects of pacing in the right atrial appendage (RAA) and in the inter-atrial septum (IAS).


METHODS
Forty-two patients (15 male, 72 +/- 7 years) underwent electrophysiologic study to measure the difference between the conduction time from RAA to coronary sinus ostium during stimulation at 600 ms and after extrastimulus (DeltaCTos). Patients were classified as group A if DeltaCTos > 60 ms and group B if < 60 ms. Each Group was randomized to RAA/IAS pacing and algorithms ON/OFF.


RESULTS
Fifteen patients (36%, group A) had DeltaCTos = 76 +/- 11 ms and 27 patients (64%, group B) had DeltaCTos = 36 +/- 20 ms. Twenty-two patients were paced at the RAA and 20 at the IAS. During the study, no AF recurrences were reported in 11 of 42 (26%) patients, independently of RAA or IAS pacing. Patients from group A and RAA pacing had 0.79 +/- 0.81 episodes of AF/day during DDD, which increased to 1.52 +/- 1.41 episodes of AF/day during DDDR + Alg (P = 0.046). Those with IAS pacing had 0.5 +/- 0.24 episodes of AF/day during DDD, which decreased to 0.06 +/- 0.08 episodes of AF/day during DDDR + Alg (P = 0.06). In group B, no differences were reported between pacing sites and pacing modes.


CONCLUSIONS
Severe right atrial conduction delay is present in one-third of patients with SND and AF: continuous pacing at the IAS is superior to RAA for AF recurrences. In patients without severe conduction delay, no differences between pacing site or mode were observed.
Verlato
Roberto
R
Cardiology Department, General Hospital, Via P. Cosma 1, 35012 Camposampiero, Italy. roberto.verlato@libero.it
Zanon
Francesco
F
Bertaglia
Emanuele
E
Turrini
Pietro
P
Baccillieri
Maria Stella
MS
Baracca
Enrico
E
Bongiorni
Maria Grazia
MG
Zampiero
Aldo
A
Zonzin
Pietro
P
Pascotto
Pietro
P
Venturini
Diego
D
Corbucci
Giorgio
G
D000368:Aged; D000465:Algorithms; D001281:Atrial Fibrillation / Q000503:physiopathology / Q000628:therapy*; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D005260:Female; D006325:Heart Atria / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D010865:Pilot Projects; D015995:Prevalence; D011446:Prospective Studies; D012804:Sick Sinus Syndrome / Q000503:physiopathology / Q000628:therapy*