In this study the effects of different pacing protocols on left ventricular (LV) torsion was evaluated over the full cardiac cycle. A systolic and diastolic series of Magnetic Resonance Imaging scans were combined and used to calculate the torsion of the LV. The asynchronous contraction resulting from ventricular pacing interferes with the temporal evolution of LV torsion. From these experiments we have shown that measuring torsion is an extremely sensitive indicator of the existence of ectopic excitation. The torsion of the left ventricle was investigated under three different protocols: (1) Right atrial pacing, (2) Right ventricular pacing and (3) Simultaneous pacing from the right ventricular apex and left ventricular base. The temporal evolution of torsion was determined from tagged magnetic resonance images and was evaluated over the full cardiac cycle. The peak twist T$-max$/ for the RA paced heart was 11.09 ($POM@3.54) degrees compared to 6.06 ($POM@1.65) degrees and 6.09 ($POM@0.68) degrees for the RV and Bi-V paced hearts respectively. While biventricular pacing has been shown to increase the synchrony of contraction, it does not preserve the normal physiological twist patterns of the heart.
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机译：在这项研究中，在全心动周期中评估了不同起搏方案对左心室（LV）扭转的影响。结合了一个收缩和舒张系列的磁共振成像扫描，并用于计算LV的扭转。由心室起搏产生的异步收缩干扰了LV扭转的时间演变。从这些实验来看，我们表明测量扭转是异位激发存在的极其敏感的指标。在三种不同方案下研究了左心室的扭转：（1）右心房起搏，（2）右心室起搏和（3）同时从右心室顶点和左心室碱上起搏。从标记的磁共振图像确定扭转的时间演变，并在完整的心动周期评估。 Ra节奏心的峰值Twist -max $ / for Ra paced Heart为11.09（$ 33.54）度数，而RV和Bi-V节奏的6.06（¥6.65）度和6.09（¥78）度分别为心。虽然已经显示了五个起搏增加了收缩同步，但它不保留心脏的正常生理扭曲模式。
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