Benefits of rate-responsive pacing in patients with sick sinus syndrome.
The effect of changing a rate-responsive pacemaker program (which reacts to evoked QT interval) to fixed-rate ventricular pacing was studied in 10 patients with sick sinus syndrome (SSS). After the patients had been in the rate-responsive mode (VVIR) for at least one year, the exercise capacity (maximal oxygen consumption [peak VO2], anaerobic threshold [AT], and cardiac output [CO] at these points) was examined. Three hours later on the same day, the pacemaker was reprogrammed to the fixed-rate pacing (VVI) and the exercise capacity was examined again (VVI-S). One month later, a similar exercise test was also done in the VVI mode (VVI-L). There was no significant difference in peak VO2 and AT between VVIR and VVI-S, but both peak VO2 and AT were significantly lower in VVI-L than in VVIR. However, there were no significant differences in the CO at peak VO2 or AT between any of the pacing modes. These findings indicate that a VVIR pacemaker should not be reprogrammed to the VVI mode in SSS patients, because the change can cause the exercise capacity to deteriorate.
Nishino
M
M
Division of Cardiology, Osaka Rosai Hospital, Japan.
Ito
T
T
Miyawaki
M
M
Nakagawa
T
T
Kuryu
T
T
Tanahashi
H
H
Yamada
Y
Y
Abe
H
H
D000368:Aged; D015308:Anaerobic Threshold; D015150:Echocardiography, Doppler; D004562:Electrocardiography; D005080:Exercise Test / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D010138:Pacemaker, Artificial / Q000706:statistics & numerical data; D012804:Sick Sinus Syndrome / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*