NONINVASIVE QUANTIFICATION OF LEFT-VENTRICULAR ROTATIONAL DEFORMATION IN NORMAL HUMANS USING MAGNETIC-RESONANCE-IMAGING MYOCARDIAL TAGGING
NONINVASIVE QUANTIFICATION OF LEFT-VENTRICULAR ROTATIONAL DEFORMATION IN NORMAL HUMANS USING MAGNETIC-RESONANCE-IMAGING MYOCARDIAL TAGGING
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DOI：
10.1161/01.cir.81.4.1236
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发表时间：
1990-04-01
期刊：
影响因子：
37.8
通讯作者：
SHAPIRO, EP
中科院分区：
文献类型：
--
作者：
BUCHALTER, MB;WEISS, JL;SHAPIRO, EP
人们一直认为，左心室顶点相对于基底的旋转是人类正常收缩功能的一个组成部分，但很难进行无创测量。标记是一种新的磁共振成像技术，在获取图像之前，通过选择性地对与成像平面正交的窄平面进行射频激励，对特定的心肌区域进行标记。标签显示为黑线，在心肌中持续400-500毫秒，如果在舒张末期使用，将随着心肌穿过收缩期而移动。标记用于无创量化人类左心室扭转和圆周-纵向剪切（shearCL）。8名年龄在24-38岁的正常志愿者在0.38 t铁芯电阻磁体上成像。在收缩期末分别获得五张短轴左心室图像，定位于整个左心室（LV）。在舒张末期应用四个等角径向标签，在8个位置与心肌相交。我们计算了每个心外膜和心内膜标签点（标签点是标签穿过心外膜或心内膜的地方）在收缩期末与相应标签点在基面上的收缩期位置的角位移差异。这个值被称为扭转角。由此，shearCL，心外膜或心内膜表面上收缩期标签位置与相应的基底标签位置之间的夹角，及其在感兴趣的切片上的投影可以在左室壁的32个点上计算出来。心尖片上8个位置的扭转角相对于心内膜点基底扭转角的平均值（心内膜扭转）为19.1 +-。2.0.degree。(意思。+ -。扫描电镜，p < 0.001)，从顶点看逆时针。心外膜扭转（逆时针，11.2±）。1.3.degree。P < 0.001)为8。1.9.degree。小于心内膜（p < 0.01）。两种心内膜后间隔区域的扭转（基底和顶点之间扭转角的平均值）小于前外侧区域(12.4 .+-。2.9.degree。Vs. 23.1 .+-。4.4度，p < 0.001)和心外膜（6.4度+- 0.001）。3.学位。Vs. 12.8 .+-3.1度，p < 0.04)。心外膜和心内膜的扭转角随距基底的距离增加而增加。然而，发现不同的扭转量导致两种心外膜的剪切cl量相似(5.0 .+-。0.6℃)和心内膜(4.0℃+-。0.5度)，不随离基底距离的增加而增加。因此，扭力随离基底和离左室中心的距离而变化，但在左室各层的剪切力是恒定的。这种剪切cl的稳定性可能代表了一个重要的原理，通过该原理，在正常射血过程中，通过左室壁和沿左室壁的应力是均匀的。
It has been postulated that rotation of the left ventricular apex with respect to the base is a component of normal systolic function in humans, but it has been difficult to measure it noninvasively. Tagging is a new magnetic resonance imaging technique that labels specific areas of myocardium by selective radio-frequency excitation of narrow planes orthogonal to the imaging plane before acquiring an image. Tags appear as black lines and persist in myocardium for 400-500 msec and, if applied at end diastole, will move with the myocardium through systole. Tagging was used to noninvasively quantify left ventricular torsion and circumferential-longitudinal shear (shearCL) in humans. Eight normal volunteers, aged 24-38 years, were imaged in a 0.38-T iron-core resistive magnet. Five short-axis left ventricular images, positioned to encompass the entire left ventricle (LV), were obtained separately at end systole. Four equiangular radial tags had been applied at end diastole, intersecting the myocardium at eight locations. We calculated the difference in angular displacement of each epicardial and endocardial tag point (a tag point being where the tag crossed the epicardium or endocardium) at end systole from the systolic position of the corresponding tag point on the basal plane. This value was called the torsion angle. From this, shearCL, the angle inscribed on the epicardial or endocardial surface between the systolic tag position, the corresponding basal tag position, and its projection onto the slice of interest could be calculated at 32 points in the left ventricular wall. The mean of the torsion angles of the eight locations on the apical slice, relative to the mean of the torsion angles of the base for endocardial points (endocardial torsion), was 19.1 .+-. 2.0.degree. (mean .+-. SEM, p < 0.001), counterclockwise when viewed from the apex. Epicardial torsion (counterclockwise, 11.2 .+-. 1.3.degree.; p < 0.001) was 8 .+-. 1.9.degree. less than the endocardium (p < 0.01). Torsion (mean of torsion angles between base and apex) in the posteroseptal regions was less than in anterolateral regions for both endocardium (12.4 .+-. 2.9.degree. vs. 23.1 .+-. 4.4.degree., p < 0.001) and epicardium (6.4 .+-. 3.degree. vs. 12.8 .+-. 3.1.degree., p < 0.04). The torsion angle increased with distance from the base for both epicardium and endocardium. Different amounts of torsion, however, were found to result in similar amounts of shearCL for both epicardium (5.0 .+-. 0.6.degree.) and endocardium (4.0 .+-. 0.5.degree.), which did not increase with distance from the base. Therefore, torsion varies with distance from the base and from the center of the LV but constancy of shearCL at each level of the LV is achieved. This constancy of shearCL may represent an important principle by which stress through and along the left ventricular wall is equalized during normal ejection.