二维超声心动图评价局部心肌缺血的新指标

心肌缺血引起局部左室收缩功能减低常伴有心室内径增大和局部室壁变薄。收缩末期半径与局部室壁厚度比值（Ｒ／Ｔｈ）是二维超声心动图（２ＤＥ）评价局部左室收缩功能的一种新指标，并不受心脏位置移动的影响。１２只麻醉犬用自制微米缩窄器造成暂时性不同程度心肌缺血。以２ＤＥ短轴切面等分１２节段分别计测收缩末期Ｒ／Ｔｈ和半轴缩短率。在心肌缺血区，收缩末期Ｒ／Ｔｈ缺血前平均１．５０±０．７０％，缺血时增加至２．２０＋０．８％，再灌注后逐渐恢复正常；局部半径缩短率从正常时平均３８．１±８．２％减低至１．７±７．９％，再灌注后逐渐恢复到基础状态。实验发现收缩末期Ｒ／Ｔｈ和室壁增厚率及半轴缩短率各自相关良好（Ｒ＝－０．８８和０．７６）。结论：测定收缩末期Ｒ／Ｔｈ为定量局部左室收缩功能提供一种超声心动图指标，与现在的２ＤＥ方法比较，具有独特的判断标准并且不受心脏移动的影响。

An new index of two-dimensional echocardiography for estimating regional myocardial ischemia:end-systolic radius to thickness ratio

Regional left ventricular contractile dysfunction induced by ischemia is associated with less thickening of regional wall and a larger ventricular radius at end-systole.End-syotolic radius to regional wall thickness ratio (R/Th)measured by two dimensional echorardiography (2DE) may provide a new accurate index of regional left ventricular contractile function that is totally independent of cardiac motion. A total of 12 transient different degree of myocardial ischemia were performed with the contractor in anesthetic dogs.End-systolic R/ Th and regional hemiaxis shortening fraction were derived from the 2DE short-axis view along 12 equidistant radii.In the ischemic zone, end-systolic R/Th averaed 1.50±0.7% before and increased to 2.20±0.8% during ischemia with a gradual return to baseline after reporfusion.Regional hemiaxis shortening averaged 38.1 ±8.2% during baseline,decreased to 1.7±7.9% during myocardial ischemia with return to baseline after reperfusion. A significant correlation was found between regional wall thickening fraction and end-systolic R/ Th as well as hemiaxis shortening fraction for absolute values (R=-0.88 and 0.76).Conclusion:measurements of end-systolic R/Th provide an alternative echocardiographic index for quantitating regional left ventricular contractile function that compares well with an independent standard and,in contrast to existing methods, is not independent standard,and not affected by external cardiac motion.