Exercise-induced changes in QT interval duration and dispersion in patients with isolated myocardial bridging Irfan Barutcu * ,a , Alpay Turan Sezgin b , Hakan Gullu c , Ergun Topal b , Nusret Acikgoz c , Ramazan Ozdemir c a Kocatepe Heart Education and Research Hospital, Department of Cardiology, Afyon, Turkey b Inonu University Turgut Ozal Medical Center, Turgutlu, Turkey c Department of Cardiology, Baskent University Adana Hospital, Adana, Turkey Received 22 September 2002; received in revised form 25 January 2003; accepted 11 March 2003 Abstract 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. Method: 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 F 20 vs. 421 F 18 ms, p > 0.05 and QT min : 380 F 12 vs. 378 F 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 F 13 vs. 66 F 14 ms, p < 0.05 and 37 F 14 vs. 69 F 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 F 18 vs. 412 F 17 ms, p>0.05 and QT min : 390 F 11 vs. 387 F 10 ms, p>0.05; QT d : 25 F 14 vs. 31 F 16 ms, p>0.05; QT cd : 27 F 15 vs. 33 F 17 ms, p>0.05). Conclusion: 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. D 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: Isolated myocardial bridging; QT dispersion and arrhythmia 1. Introduction Isolated myocardial bridging (MB) is a congenital anom- aly of the coronary artery and it leads to luminal narrowing during systolic period. Although it is often considered to be a simple variant of the normal anatomy of coronary arteries, some data have demonstrated its pathologic potential. Myo- cardial infarction, rhythm disturbances or sudden death have been reported to be associated with MB [1–4]. However, the factors that increase the risk for malignant ventricular arrhythmias have not been identified in patients with MB. Measurement of the variability in the duration of the QT interval among different leads of a standard 12-lead ECG has been proposed as a noninvasive method to detect inhomo- geneity of ventricular recovery times and arrhythmogenic potential. Prolonged QT dispersion is associated with an increased risk of serious ventricular arrhythmias in patients with hypertrophic cardiomyopathy, ischemic heart disease and myocardial infarction [5–7]. However, no previous studies have examined exercise-induced electrocardiograph- ic changes and its relation with susceptibility to arrhythmias in patients with MB. Therefore, this study was designed to test the hypotheses that whether exercise testing increases ventricular vulnerability or induces the development of malignant ventricular arrhythmias in patients with MB. 2. Material and method Between January 1998 and March 2002, 1200 consecu- tive patients who had been referred for investigation of chest 0167-5273/$ - see front matter D 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2003.03.009 * Corresponding author. E-mail address: irfanbarutcu@yahoo.com (I. Barutcu). www.elsevier.com/locate/ijcard International Journal of Cardiology 94 (2004) 177 – 180