近藤 寛也

Hiroya KONDO

大阪大学附属病院医療情報部

Department of Medical Information Science, Osaka University Hospital

キーワード : High frame rate echocardiography, Subtraction technique, Coronary artery disease, Asynchrony, Diastolic dysfunction

Myocardial ischemia frequently impairs left ventricular diastolic function, even if systolic function is maintained within normal limits. Detection of the regional diastolic dysfunction has been described as a potential means of diagnosing the presence of chronic myocardial ischemia or reduced coronary flow. We investigated whether a system that combined high-frame-rate two-dimensional echocardiography with a subtraction technique could be used to identify regional delays of relaxation and to distinguish coronary involved regions from normal regions. We obtained high-frame-rate echocardiograms (60 fps) in 32 normal subjects and 23 patients with effort angina. The images were processed by a frame-by-frame subtraction of digitized echocardiograms. The onset in the outward motion of left ventricular wall was detected during the isovolumic relaxation period or early diastole on the subtracted echograms in all segments studied. We defined the relaxation index as the interval from the second heart sound to the onset of the outward wall motion. The relaxation index was evaluated in each left ventricular segment using a 16-segment model. All patient segments were classified into coronary involved regions and normal regions on the basis of the coronary angiographic findings. The mean relaxation index in normal subjects was 31±15 ms. In angina patients, the relaxation index of the coronary involved segments was prolonged: 33±16 ms in the normal segments and 94±28 ms in the coronary involved segments. Our results suggest that this new technique is capable of identifying the retardation of relaxation as delayed onset of outward wall motion. The present non-invasive technique may be a clinically useful means of possively detecting the coronary involved area in patients with underlying coronary artery stenosis.