Evaluation of Left Ventricular Function by Three-Dimensional Speckle-Tracking Echocardiography in Patients with Myocardial Bridging of the Left Anterior Descending Coronary Artery

Abstract

To understand the influence of myocardial bridging (MB) on left ventricular (LV) function, myocardial function was studied in patients with MB of the left anterior descending coronary artery (LAD) using three-dimensional speckle-tracking echocardiography (STE). Left anterior descending coronary artery MB was diagnosed by coronary angiography in 82 subjects. Patients were divided into three groups according to the percentage of systolic narrowing of the compressed segment: 30% to 49% was defined as group I (24 patients), 50% to 74% as group II (28 patients), and ≥75% as group III (30 patients). Thirty gender- and age-matched normal subjects were included as controls. Left ventricular myocardial deformation was estimated by three-dimensional STE. Left ventricular ejection fractions were normal in all patients, but diastolic function was impaired in groups II and III (E/E' ratio, 9±3 and 10±3, respectively). The amplitudes of longitudinal strain (LS) and area strain (AS) of the LAD territory was significantly reduced in groups II and III compared with controls and group I (LS, -15 ± 2% and -12 ± 1% vs -19 ± 2% and -18 ± 2%; AS, -22 ± 2% and -13 ± 2% vs -33 ± 4% and -33 ± 3%; P<.0001), but the amplitudes of circumferential and radial strain showed no intergroup differences. Longitudinal strain and AS were significantly lower in patients with fractional flow reserve < 0.75 than in those with fractional flow reserve ≥ 0.75 (P<.0001), with relative preservation of circumferential and radial strain. The severity of LAD compression was significantly associated with AS and LS of the LAD territory (r= -0.92 and r= -0.84, respectively, P<.0001), but the correlations with circumferential and radial strain were modest (r= -0.36 and r= -0.32, respectively, P<.05). With the increasing severity of systolic compression of the mural coronary artery, LV diastolic function and regional systolic deformation (AS and LS) of the MB perfusion territory were reduced. Three-dimensional STE can detect subtle myocardial dysfunction in patients with MB.