No abstract

Background: To understand the impact of myocardial bridge (MB) on left ventricle (LV) function, we evaluate the myocardial function in patients with MB of the left anterior descending coronary artery (LAD), using real-time 3-dimensional speckle tracking echocardiography (RT3D-STE). Methods: The LAD MB was diagnosed by coronary angiography in 82 patients. According to the percentage of systolic compression (SC), patients were divided into 3 groups: SC <50% defined as Group I (n=24), SC 50%-75% as Group II (n=28), and SC >75% as Group III (n=30). Thirty age and gender matched normal subjects were studied as controls. The traditional echocardiography was performed, and LV deformation was estimated by RT3D-STE. Results: The LV ejection fraction was normal in patients with LAD MB. However, the peak longitudinal (LS) and area strain (AS) of the LAD territory were significantly reduced in Group II and III when compared with controls and Group I (p<0.05). The peak circumferential (CS) and radial strain (RS) were significantly reduced only in Group III (p<0.05) (Table). Furthermore, the amplitude of strain variables were significantly reduced in patients with symptom than those without (AS: 17.7±6.4 vs. 25.3±8.4%; LS:-13.0±1.9 vs. -16.2±2.5%; CS:-15.4±3.3 vs. 18.9±3.0 %; RS: 36.6±3.8 vs. 49.4±2.7%; all p<0.0001). The severity of LAD compression correlated the best with with AS at LAD territory (r=–0.90, p<0.0001), although it was also significant in conventional strain variables (LS: r =–0.79, CS: r =–0.69, RS: r =–0.64, all p <0.0001). Conclusions: Despite apparently normal ejection fraction, myocardial strain is abnormal in the LAD territory which had MB. Such abnormality is more pronounced in patients with progressively more severe MB and in those with symptoms. Furthermore, the area strain by RT3D-STE appeared to be most accurate in detection of subclinical systolic dysfunction in patients with LAD MB than conventional 2D strain parameters.