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A bundle of myocardium that bridges over the epicardial coronary artery is called as Myocardial Bridging (MB). It is supposed to restrict the coronary flow anatomically and functionally when myocardial oxygen demand increased due to strenuous exercise. While ST/T changes on ECG during exercise may represent abnormality of coronary flow and also ischemia upon exertion, ST/T changes on rest ECG may represent silent ischemia due to coronary pathology. However abnormalities of myocardium such as local myocardial thickening, isolated papillary muscle hypertrophy, etc. may cause ST/T changes on resting ECG. We aimed to evaluate and discuss whether it could be associated with variable ST and T wave changes on resting ECG and to discuss its anatomically significance.
We retrospectively evaluated the changes on resting ECG in 36 patients with MB diagnosed with MSCT angiography.
Of the 36 subjects; 16 had ST and T wave changes, 17 had only ST changes. Downsloping and horizontal ST despression was observed in 16 and 17 patients, respectively. 25 had <0.5 mm ST depression and 8 had <1 mm ST depression. Flattening or inversion of T wave was observed in 16 and 16 subjects, respectively. ECG changes were localized on inferior, lateral and inferior-lateral derivations in 15, 3 and 17 patients with MB.
Various types of ECG changes may accompany with the presence of MB in patients with. <0.5 mm depression of ST segment and flattening/inversion of T wave are the predominant changes. Downsloping depression of ST segment accompanied with not deeply but minimally inverted T wave inversion may remind the ECG changes which may be observed in local myocardial diseases clinically represented with myocardial wall thickening or myocardial disarray such as e.g. isolated papillary hypertrophy. Thus those ECG changes observed on the resting ECG in patients with MB may represent not only a silent ischemia but also a histological or regional abnormality of myocardium consisting bridging segment. Further studies in order to evaluate that regional abnormality of myocardial tissue by means of cardiac magnetic resonance imaging may be designed in the future.