title: Changes in evoked QT intervals according to variations in atrioventricular delay and cardiac function in patients with implanted QT-driven DDDR pacemakers.
abstract: In patients with implanted DDD pacemaker, cardiac output is maximal when atrioventricular (AV) delay is set to give the maximum QT interval (QTI). QTI is used as a sensor of a rate-responsive pacemaker and the evoked QTI (eQTI) is measured as the time duration from the ventricular pace-pulse and the T sense point, which is the steepest point of the intracardiac T wave. The relationship between the changes in eQTI according to AV delay variations and cardiac function was studied in 13 patients (74.2+/-9.3 [SD] years old) with an implanted QT-driven DDDR-pacemaker. A special software module was downloaded into the pacemaker memory and a personal computer equipped with the special software was connected to the programmer for eQTI date-logging. AV delay was set at 100, 120, 150, 180 and 210 ms. Delta eQTI was defined as maximal eQTI - minimal eQTI. The ejection fraction (EF) was measured by echocardiography. When the AV delay was prolonged, eQTI gradually increased and reached a peak, and then decreased. Delta eQTI in patients with reduced cardiac function (EF <40%) was significantly greater than that in normal cardiac function (EF >55%, 7.6+/-4.9 vs 2.7+/-9.8 ms, p<0.05). There was significant negative correlation between EF and delta eQTI (r=-0.63, p<0.05). The peak of changes in eQTI according to AV delay variations was steeper in patients with reduced cardiac function than in those with normal cardiac function. In conclusion, changes in eQTI according to AV delay variation are greater in patients with reduced cardiac function than in those with normal cardiac function, and the AV delay that gives the maximal eQTI can be easily determined in patients with reduced cardiac function.
authors.affiliation: Second Department of Internal Medicine, Yokohama City University School of Medicine, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Teruyasu
authors.initials: T
authors.lastname: Sugano
authors.forename: Shinichi
authors.initials: S
authors.lastname: Sumita
authors.forename: Masami
authors.initials: M
authors.lastname: Kosuge
authors.forename: Izumi
authors.initials: I
authors.lastname: Kobayashi
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Yohei
authors.initials: Y
authors.lastname: Yamakawa
authors.forename: Kohei
authors.initials: K
authors.lastname: Matsusita
authors.forename: Katsumi
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ohkusu
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Uchino
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kimura
authors.forename: Takashi
authors.initials: T
authors.lastname: Usui
authors.forename: Satoshi
authors.initials: S
authors.lastname: Umemura
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004562:Electrocardiography; D004581:Electronics; D004867:Equipment Design; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006327:Heart Block / Q000503:physiopathology* / Q000628:therapy; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D012984:Software; D013318:Stroke Volume; D013686:Telemetry; D014463:Ultrasonography