The spiral orientation of left ventricular (LV) fibers suggests that twisting about the ventricular long axis of the apex with respect to the base, i.e., torsional deformation, may be characteristic of LV contraction. To demonstrate this twisting motion, 10 orthotopic human cardiac allograft recipients were studied with biplane cineradiography of tantalum helices implanted within the LV midwall at 12 specific sites. Counterclockwise twisting about the LV long axis (as reviewed from apex to base) accompanied ventricular ejection in all patients. Torsional deformation angles, measured relative to a reference minor axis at the base, were substantially smaller in the anteroapical wall, as compared with counterparts in the apical third of the inferior and lateral walls (anterior = 13.3 +/- 6.0 degrees, inferior = 18.7 +/- 6.3 degrees, and lateral = 23.4 +/- 10.7 degrees). Torsional angles at the midventricular level were roughly half as much and exhibited similar regional variabilities (anterior = 7.6 +/- 3.3 degrees, inferior = 9.0 +/- 3.3 degrees, lateral = 10.7 +/- 5.2 degrees, and septal = 8.8 +/- 3.8 degrees). Comparison of control beats and the initial beat after abrupt cessation of rapid atrial pacing (126 +/- 10 beats/min) with return to the control heart rate (96 +/- 9 beats/min) permitted the mild positive inotropic effect of tachycardia to be assessed at similar levels of ventricular load. Torsional deformation of the anteroapical and inferoapical sites increased significantly (p less than 0.05) over control values to 15.6 +/- 7.5 degrees and 21.2 +/- 5.5 degrees, respectively. In contrast, torsional deformation of the lateral wall was essentially unchanged. These data provide direct evidence for torsional deformation of the left ventricle in humans, demonstrate that torsion of the LV chamber is nonuniform, and suggest a dependence of LV torsion upon contractile strength that is attenuated in the lateral wall.
The present study was designed to investigate the anisotropy of systolic chord shortening in the lateral, inferior, septal, and anterior regions of the human left ventricle. At the time of surgery, 12 miniature radiopaque markers were implanted into the left ventricular midwall of the donor heart in 15 cardiac transplant recipients. Postoperative biplane cineradiograms were computer-analyzed to yield the three-dimensional coordinates of these markers at 16.7-msec intervals. In each of the four left ventricular regions, chords were constructed from a central marker to outlying markers, and the percent systolic shortening of each chord was calculated. In each region, chord angles were measured with respect to the circumferential direction (positive angles counterclockwise) and each chord was assigned to one of four angular groups: I. oblique, -45 +/- 22.5 degrees or 135 +/- 22.5 degrees; II. circumferential, 0 +/- 22.5 degrees or 180 +/- 22.5 degrees; III. oblique, 45 +/- 22.5 degrees or -135 +/- 22.5 degrees; or IV. longitudinal, 90 +/- 22.5 degrees. In the lateral, inferior, and septal regions, respectively, systolic shortening (mean +/- SD%) was significantly greater in Group I chords (19 +/- 5%, 17 +/- 5%, and 15 +/- 4%) than those in Group II (15 +/- 5%, 12 +/- 4%, and 11 +/- 4%), Group III (12 +/- 4%, 12 +/- 5%, and 11 +/- 4%), or Group IV (13 +/- 5%, 13 +/- 6%, and 12 +/- 5%). The anterior region was unique in exhibiting equal shortening in both Group I and Group II chords (16 +/- 5%), although the shortening of these chords was significantly greater than that of Group III and Group IV (12 +/- 5%) in this region. A cylindrical mathematical model was developed to relate longitudinal, circumferential, and oblique systolic shortening to torsional deformation about the long axis of the left ventricle. Torsional deformations measured in these 15 hearts were of sufficient magnitude and correct sense to agree with model predictions. These data suggest that torsional deformations of the left ventricle are of fundamental importance in linking the one-dimensional contraction of the helically wound myocytes to the three-dimensional anisotropic systolic shortening encountered in the transplanted human heart.
