Buchalter M B, Rademakers F E, Weiss J L, Rogers W J, Weisfeldt M L, Shapiro E P
Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Cardiovasc Res. 1994 May;28(5):629-35. doi: 10.1093/cvr/28.5.629.
The aim was to investigate the generation of rotation of the left ventricular apex with respect to the base by magnetic resonance tagging, a non-invasive method of labelling the myocardium, in a canine model.
18 dogs were imaged at baseline and during: (1) inotropic stimulation with dobutamine; (2) chronotropic stimulation with atrial pacing; (3) anterior wall ischaemia; (4) posterior wall ischaemia; and (5) varying left ventricular activation site; six dogs underwent each intervention. Apical rotation of the apex (torsion) was quantified. The epicardium and the endocardium were considered separately, as were the anterior and posterior walls.
Mean torsion of the epicardium [anterior 3.1(SEM 1.2) degrees, posterior 9.9(1.0) degrees] was less than that of the endocardium [anterior 8.1(2.6) degrees, posterior 14.9(2.0) degrees, p < 0.05 for both]. Anterior torsion was less than posterior torsion for both the epicardium, p < 0.05, and the endocardium, p < 0.05. Dobutamine increased torsion of both the epicardium [anterior 13.3(2.2) degrees, posterior 12.6(1.7) degrees, p < 0.05 for both] and the endocardium [anterior 24.6(2.3) degrees, posterior 16.5(2.1) degrees, p < 0.05 for both]. Atrial pacing at 160% baseline rate increased torsion of both the anterior wall [epicardium 6.6(1.0) degrees, endocardium 11.3(1.2) degrees, p < 0.05] and the posterior wall [epicardium 13.0(1.3) degrees, endocardium 19.4(1.9) degrees, p < 0.05]. Anterior wall ischaemia reduced torsion of the anterior wall only [epicardium -2.0(1.0) degrees, endocardium 6.7(2.3) degrees, both p < 0.05]. Posterior wall ischaemia reduced torsion of the posterior wall of the epicardium only [7.1(1.2) degrees, p < 0.05] but also reduced torsion of the anterior wall [epicardium 0.7(1.0) degrees, endocardium 2.4(1.6) degrees, p < 0.05 for both]. Altering the pattern of left ventricular activation by atrioventricular pacing reduced torsion of the posterior wall of the epicardium [6.6(1.2) degrees, p < 0.05] and of the anterior [3.6(1.9) degrees, p < 0.05] and posterior [7.1(1.6) degrees, p < 0.05] walls of the endocardium.
Rotational deformation of the left ventricle is dependent on the pattern of left ventricular activation and the contractile state. That a decrease in the contractile state in one area (by ischaemia) can cause a decrease in rotation in another suggests that this rotation depends on the complex fiber arrangement of the whole ventricle.
旨在通过磁共振标记技术（一种标记心肌的非侵入性方法），在犬类模型中研究左心室心尖相对于心底的旋转情况。
对18只犬在基线状态以及以下过程中进行成像：（1）用多巴酚丁胺进行变力性刺激；（2）用心房起搏进行变时性刺激；（3）前壁缺血；（4）后壁缺血；（5）改变左心室激动部位；每种干预措施有6只犬接受。对心尖的旋转（扭转）进行量化。分别考虑心外膜和心内膜，以及前壁和后壁。
心外膜的平均扭转[前壁3.1（标准误1.2）度，后壁9.9（1.0）度]小于心内膜[前壁8.1（2.6）度，后壁14.9（2.0）度，两者p<0.05]。对于心外膜（p<0.05）和心内膜（p<0.05），前壁扭转均小于后壁扭转。多巴酚丁胺增加了心外膜[前壁13.3（2.2）度，后壁12.6（1.7）度，两者p<0.05]和心内膜[前壁24.6（2.3）度，后壁16.5（2.1）度，两者p<0.05]的扭转。以160%基线心率进行心房起搏增加了前壁[心外膜6.6（1.0）度，心内膜11.3（1.2）度，p<0.05]和后壁[心外膜13.0（1.3）度，心内膜19.4（1.9）度，p<0.05]的扭转。前壁缺血仅降低了前壁的扭转[心外膜-2.0（1.0）度，心内膜6.7（2.3）度，两者p<0.05]。后壁缺血仅降低了心外膜后壁的扭转[7.1（1.2）度，p<0.05]，但也降低了前壁的扭转[心外膜0.7（1.0）度，心内膜2.4（1.6）度，两者p<0.05]。通过房室起搏改变左心室激动模式降低了心外膜后壁的扭转[6.6（1.2）度，p<0.05]以及心内膜前壁[3.6（1.9）度，p<0.05]和后壁[7.1（1.6）度，p<0.05]的扭转。
左心室的旋转变形取决于左心室激动模式和收缩状态。一个区域（因缺血）收缩状态的降低可导致另一区域旋转的降低，这表明这种旋转取决于整个心室复杂的纤维排列。
