Waldman L K, Nosan D, Villarreal F, Covell J W
Department of Medicine, University of California, San Diego, La Jolla 92093.
Circ Res. 1988 Sep;63(3):550-62. doi: 10.1161/01.res.63.3.550.
To determine the relation between local myofiber anatomy and local deformation in the wall of the left ventricle, both three-dimensional transmural deformation and myofiber orientation were examined in the anterior free wall of seven canine left ventricles. Deformation was measured by imaging columns of implanted radiopaque markers with high-speed, biplane cineradiography (16 mm, 120 frames/sec). Hearts were fixed at end diastole and sectioned parallel to the local epicardial tangent plane to determine the transmural distribution of fiber directions at the site of strain measurement. The principal direction of deformation associated with the greatest shortening was compared with the local fiber direction in the outer (21 +/- 8% of the wall thickness from the epicardium) and inner (65 +/- 9%) halves of the wall. Although the fiber direction varied substantially with depth from the epicardium, the principal direction did not. In the outer half of the wall, fiber direction averaged -8 +/- 24 degrees, while the principal direction averaged -33 +/- 24 degrees from circumferential (counterclockwise angles are positive). In the inner half, fiber direction averaged 69 +/- 10 degrees, while the principal direction averaged -22 +/- 21 degrees. Therefore, while fiber and principal directions were not substantially different in the outer half, the greatest shortening occurred orthogonally to the fiber direction in the inner half. Normal and shear strains measured in a cardiac coordinate system (circumferential, longitudinal, and radial coordinates) were rotated (transformed) to "fiber" coordinates in both halves of the wall. In the outer half, normal strains observed in the fiber (-0.09 +/- 0.04) and cross-fiber (-0.04 +/- 0.04) directions were not significantly different (paired t test, p less than 0.05). In the inner half, more than twice as much strain occurred in the cross-fiber (-0.17 +/- 0.03) than in the fiber direction (-0.06 +/- 0.06). Moreover, the only shear strain that remained substantial after transformation was transverse shear in the plane of the fiber and radial coordinates. These results suggest that both reorientation and cross-sectional shape changes of myofibers or the interstitium may contribute to the large wall thickenings observed during contraction, particularly in the inner half of the ventricular wall.
为了确定左心室壁局部肌纤维解剖结构与局部变形之间的关系，对7只犬左心室前游离壁的三维透壁变形和肌纤维方向进行了研究。通过高速双平面电影血管造影术（16毫米，120帧/秒）对植入的不透射线标记柱进行成像来测量变形。心脏在舒张末期固定，并沿局部心外膜切线平面切片，以确定应变测量部位纤维方向的透壁分布。将与最大缩短相关的主要变形方向与壁外（距心外膜壁厚的21±8%）和内（65±9%）半部的局部纤维方向进行比较。尽管纤维方向随距心外膜深度的变化很大，但主要方向没有变化。在壁的外半部，纤维方向平均为-8±24度，而主要方向平均为-33±24度（逆时针角度为正）。在内半部，纤维方向平均为69±10度，而主要方向平均为-22±21度。因此，虽然在壁的外半部纤维方向和主要方向没有显著差异，但在内半部最大缩短发生在与纤维方向正交的方向。在心脏坐标系（圆周、纵向和径向坐标）中测量的法向应变和剪应变在壁的两半部分都转换为“纤维”坐标。在壁的外半部，在纤维（-0.09±0.04）和跨纤维（-0.04±0.04）方向观察到的法向应变没有显著差异（配对t检验，p＜0.05）。在内半部，跨纤维方向（-0.17±0.03）的应变比纤维方向（-0.06±0.06）多两倍以上。此外，转换后仍然显著的唯一剪应变是纤维平面和径向坐标平面内的横向剪应变。这些结果表明，肌纤维或间质的重新定向和横截面形状变化可能都有助于在收缩过程中观察到的大量壁增厚，特别是在心室壁的内半部。
