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Increased risk of lethal ventricular arrhythmia is generally caused by increased heterogeneity of ventricular repolarization probably due to ischemia or myocardial disarray. Recently novel parameters derived from T wave and QT interval and representative of increased electrical heterogeneity were defined. We aimed to evaluate the latter issue in patients with myocardial bridge (MB) on coronary arteries.
Totally, 37 healthy subjects (age 36.8±5.7) and 34 patients with MB (age 40.1±4.7) who underwent MSCT coronary angiography were enrolled to the study. MB was detected when an intramural segment of epicardial coronary artery was visualized on axial and multiplanar reconstruction images. Twelve lead ECG of all participants were recorded and digitally analyzed. Tpeak-Tend interval, Tpeak-Tend dispersion, Tpeak-Tend/QTc ratio, QT interval and QTc durations were calculated. Statistical analysis were performed by independent samples t-test using SPSS 11.0.
There were no differences about heart rate, QRs duration, QT and QTc interval among groups (p>0.05). QTcdisp (43.29±4.06 vs 45.11±3.68, p=0.052), Tp-Te (83.14±8.28 vs 88.12±6.17, p=0.006), (Tp-Te)/QT ratio (0.23±0.03 vs 0.26±0.02, p=0.000), (Tp-Te)/QTc ratio (0.21±0.02 vs 0.23±0.04, p=0.002), (Tp-Te)/QTd (1.86±0.28 vs 2.05±0.23, p=0.002) were significantly prolonged in patients with MB except (Tp-Te) disp (33.22±4.90 vs 34.47±3.78, p=0.234)
As we know our study is the first one which evaluated T peak-T end interval and its dispersion and their ratio which were the novel parameters representatives of propensity of arrhythmia in patients with MB on coronary artery. We found they were significantly increased in those patients. MB may limit the coronary flow when the myocardial oxygen demand increased and may induce ischemia and myocardial electrical heterogeneity; the most powerful trigger of ventricular arrhythmia. Also MB may be a representative of locally myocardial disarray as well as in hypertrophic cardiomyopathy. As a conclusion MB may not be so much innocent. So it should be reminded in any case of ventricular arrhythmia induced by exercise. It should be sought and also reported on imaging of coronary arteries by MSCT. Further studies may be designed in order to determine the presence of clinical arrhythmia and to guide the therapy.