Exercise-induced changes in QT interval duration and dispersion in patients with isolated myocardial bridging.
BACKGROUND
Isolated myocardial bridging (MB) often is considered to be an unimportant angiographic finding; however, its association with cardiovascular event has been shown. In this study we aimed to assess exercise-induced electrocardiographic (ECG) changes and susceptibility to arrhythmia in patients with MB.


METHODS
21 consecutive patients who had angiographically proven MB (group I) and 25 subjects (group II) who had normal coronary arteries underwent exercise test using Bruce protocol. Before and after the exercise test the changes in QT interval duration and dispersion were compared.


RESULTS
Baseline characteristics of both groups were similar. Heart rate significantly increased after exercise test in both groups. In group I, after exercise mean QT(max) and QT(min) durations did not change significantly compared to baseline values, respectively. (QT(max): 411+/-20 vs. 421+/-18 ms, p>0.05 and QT(min): 380+/-12 vs. 378+/-10 ms, p>0.05). However, following exercise test QT dispersion (QT(d)) and corrected QT dispersion (QT(cd)) significantly increased when compared to baseline values, respectively. (34+/-13 vs. 66+/-14 ms, p<0.05 and 37+/-14 vs. 69+/-17 ms, p<0.05) On the other hand, in control group QT(max) and QT(min) durations, QT(c) and QT(cd) did not change significantly compared to baseline values, respectively. (QT(max): 408+/-18 vs. 412+/-17 ms, p>0.05 and QT(min): 390+/-11 vs. 387+/-10 ms, p>0.05; QT(d): 25+/-14 vs. 31+/-16 ms, p>0.05; QT(cd): 27+/-15 vs. 33+/-17 ms, p>0.05).


CONCLUSIONS
Treadmill exercise test significantly increased QT dispersion in patients with MB. This increase may result from exercise-induced ischemia at the area perfused by bridged artery.
Barutcu
Irfan
I
Kocatepe Heart Education and Research Hospital, Department of Cardiology, Afyon, Turkey. irfanbarutcu@yahoo.com
Sezgin
Alpay Turan
AT
Gullu
Hakan
H
Topal
Ergun
E
Acikgoz
Nusret
N
Ozdemir
Ramazan
R
D000328:Adult; D001145:Arrhythmias, Cardiac / Q000209:etiology / Q000503:physiopathology*; D001158:Arteries / Q000002:abnormalities; D003330:Coronary Vessel Anomalies / Q000503:physiopathology*; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000209:etiology / Q000503:physiopathology*