The effect of bipole tip-to-ring distance in atrial electrodes upon atrial tachyarrhythmia sensing capability in modern dual-chamber pacemakers.
BACKGROUND
Accurate atrial arrhythmia discrimination is important for dual chamber pacemakers and defibrillators. The aim was to assess the accuracy of atrial arrhythmia recording using modern devices and relate this to atrial tip-to-ring (TTR) distance.


METHODS
One hundred eighty-two patients (72 + or - 9 years, 55% male) with paroxysmal atrial fibrillation were enrolled and were included in the study if they had an atrial fibrillation (AF) burden of 1-50% during a monitoring phase. Seventy-nine patients fulfilled these criteria and were followed for at least 5 months. Electrodes were classified as having short (<10 mm), medium (10-12), or long (13-18) atrial TTR spacing.


RESULTS
Two thousand eight hundred eighty-three detailed onset reports were analyzed; 730 (25%) demonstrated aberrant sensing. Six percent were due to farfield R wave oversensing (FFRWO) and 19% due to undersensing, sometimes occurring in the same patient and study phase. FFRWO was significantly reduced with short TTR electrodes (P < 0.05). Undersensing due to sensitivity fallout was 18% (short), 24% (medium), and 17% (long) (P = ns). Undersensing due to pacemaker blanking was 11% (short), 11% (medium), and 12% (long) (P = ns). Active fixation electrodes did not show any difference from passive fixation.


CONCLUSIONS
Atrial electrodes with a short TTR (<10 mm) significantly reduce FFRWO without increasing undersensing and should be used routinely in patients with paroxysmal atrial tachyarrhythmias. However, 20% of atrial tachyarrythmia episodes were incorrectly classified as terminated by these modern devices due to undersensing. Clinicians should be wary of using device-derived endpoints that rely on AF episode number or duration as these may be falsely increased or reduced, respectively.
Silberbauer
John
J
Cardiology Department, Eastbourne General Hospital, Eastbourne, UK.
Arya
Anita
A
Veasey
Rick A
RA
Boodhoo
Lana
L
Kamalvand
Kayvan
K
O'Nunain
Sean
S
Hildick-Smith
David
D
Paul
Vince
V
Patel
Nikhil R
NR
Lloyd
Guy W
GW
Sulke
Neil
N
D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis; D004566:Electrodes; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial; D012680:Sensitivity and Specificity; D013610:Tachycardia / Q000175:diagnosis*