Evaluation by Contrast-Enhanced Electron Beam Computed Tomography of Myocardial Perfusion and Tissue Characteristics in Congenital Aortic Stenosis

Abstract

The evaluation of myocardial perfusion and tissue characteristics gives useful information regarding the indication for surgery. In the present study, two-phase contrast enhanced electron beam computed tomography (EBT) was used to quantitatively examine myocardial perfusion and the tissue characteristics of the left ventricular (LV) myocardium in congenital aortic stenosis (AS). The AS group comprised 15 patients and the control group had 14 non-AS patients. Myocardial ischemia and tissue characteristics were evaluated by the ratio of the incremental CT number of the myocardium (M) and the lumen (L) of the LV (M/L) in, the early phase with and without dipyridamole (Dp) loading and in the late phase after enhancement (respectively). In a comparison between the AS group and the controls, mean early M/Ls were significantly lower in the AS group than in the controls (20±5% vs 37±10%, p<0.01) and mean late M/Ls in the AS group were also significantly lower (47±11% vs 62±13%, p<0.01). In the AS patients, early M/Ls in the subendocardial and apical regions were especially lower than those of other segments, but the late M/Ls in these segments were inversely higher than those of other segments. These results suggest 2 things: (1) the existence of latent LV myocardial ischemia in AS patients, which is probably because of a hypertrophied LV wall, in turn caused by afterload, and (2) the presence of more myocardial ischemia and interstitial fibrosis in the subendocardial and apical regions of the AS heart. Using Dp loading for the AS patients increased the clarity of the contrast images. Contrast-enhanced EBT is useful for evaluating myocardial characteristics and perfusion in AS, and gives new insight into the LV wall characteristics in AS, as well as an indication for surgical correction of congenital AS.