Lorenz C H, Pastorek J S, Bundy J M
Cardiovascular Division, Barnes-Jewish Hospital, Washington University Medical Center, St. Louis, Missouri, USA.
J Cardiovasc Magn Reson. 2000;2(2):97-108. doi: 10.3109/10976640009148678.
Myofibril shortening and the oblique fiber orientation of the left ventricular myocardium results in a twisting motion of the left ventricle. Advances in cardiac magnetic resonance imaging (MRI) have made it possible to label the myocardium noninvasively and track this motion (twist) through the cardiac cycle, but little data exist on its complete systolic time course. The purpose of this study was to delineate the normal human systolic time course of ventricular twist using tagged cine-MRI. Tagged cine-MRI was performed in 10 healthy subjects. The mean systolic twist angle relative to the short axis centroid for the 10 volunteers was calculated. Interstudy and intra- and interobserver variability were assessed. During isovolumic contraction, all ventricular twist was counterclockwise. Later in systole, the basal segments changed direction and rotated in a clockwise direction, whereas the apical segments continued counterclockwise rotation. The midpoint for rotation was 45+/-8% of ventricular length. The mean short axis net ventricular twist (apex-base) at 80% systole was 12.6+/-1.5 degrees. The four wall segments showed heterogeneity in twist (lateral wall, 20.6+/-1.7 degrees; anterior wall, 17.5+/-5.1 degrees; inferior wall, 8.8+/-4.9 degrees; septum, 3.5+/-2.4 degrees). The anterior and lateral walls demonstrated significantly higher twist than the other walls (p < 0.01). Torsion increased steadily throughout systole after isovolumic contraction, whereas twist displayed rate changes. The mean interstudy and intra- and interobserver differences were less than 2.1 degrees. The close similarity in twist between subjects and the low interstudy and inter/intraobserver variation indicates that twist is a robust parameter of myocardial function. Torsion varies smoothly during systole, which may play a role in minimizing oxygen consumption. These data can serve as a baseline from which to compare alterations in regional myocardial function in disease.
肌原纤维缩短以及左心室心肌的斜纤维取向导致左心室产生扭转运动。心脏磁共振成像（MRI）技术的进步使得无创标记心肌并在心动周期中追踪这种运动（扭转）成为可能，但关于其完整收缩期时程的数据却很少。本研究的目的是使用标记电影MRI描绘正常人心室扭转的收缩期时程。对10名健康受试者进行了标记电影MRI检查。计算了10名志愿者相对于短轴质心的平均收缩期扭转角度。评估了研究间以及观察者内和观察者间的变异性。在等容收缩期，所有心室扭转均为逆时针方向。在收缩期后期，基底节段改变方向并顺时针旋转，而心尖节段继续逆时针旋转。旋转中点位于心室长度的45±8%处。收缩期80%时的平均短轴净心室扭转（心尖-心底）为12.6±1.5度。四个壁段的扭转表现出异质性（侧壁，20.6±1.7度；前壁，17.5±5.1度；下壁，8.8±4.9度；室间隔，3.5±2.4度）。前壁和侧壁的扭转明显高于其他壁（p<0.01）。等容收缩后，扭转在整个收缩期稳步增加，而扭转显示出速率变化。研究间以及观察者内和观察者间的平均差异小于2.1度。受试者之间扭转的高度相似性以及研究间和观察者间/内的低变异性表明扭转是心肌功能的一个可靠参数。扭转在收缩期平稳变化，这可能在最小化氧消耗中起作用。这些数据可作为比较疾病中局部心肌功能改变的基线。
