Dewar M L, Drinkwater D C, Wittnich C, Chiu R C
J Thorac Cardiovasc Surg. 1984 Mar;87(3):325-31.
We studied the feasibility of augmentation of impaired myocardium with synchronously paced skeletal muscle grafts. The short contractile period of skeletal muscle required development of a new stimulator to ensure that the pedicle graft contraction would simulate that of the myocardium. In four dogs each, rectus and diaphragmatic muscles were wrapped around a balloon and electrically stimulated in synchrony with the electrocardiogram, varying stimulation currents and frequency of discharge during systole. For this purpose, a prototype hybrid stimulator was developed which senses the cardiac R wave and modulates the electrical output to the skeletal muscle by delivering a train of impulses of varying frequencies within the systolic intervals. The contraction characteristics in response to such stimulation were similar in rectus and diaphragmatic muscles, but the former developed higher maximum tensions because of the greater muscle bulk. Square-wave output was found to be more effective than sine-wave stimulation, and a single stimulating electrical pulse of 40 msec duration produced a maximum tension of 60 mm Hg lasting for 120 msec, whereas a train of 4 pulses within a 320 msec period was able to achieve a maximum tension of 100 mm Hg lasting nearly 400 msec, the latter approximating that of the myocardium. In six other dogs, the rectus muscle pedicle graft was used to replace a segment of the left ventricle (25.5% +/- 2.1% of left ventricular mass) excised under cardiopulmonary bypass. Left ventricular isometric contraction was studied using a left ventricular balloon with stimulators turned on and off. Significant augmentations of left ventricular maximum tension (+19.3% +/- 2.5%, p less than 0.001, paired t test) and left ventricular contractility (+38.3% +/- 9.4%, p less than 0.001) were achieved when the skeletal muscle grafts were stimulated. Thus, in this preliminary study, skeletal muscle graft properly oriented and stimulated is able to augment the left ventricular isometric contractile function after significant loss of left ventricular myocardial mass.
我们研究了用同步起搏的骨骼肌移植物增强受损心肌功能的可行性。骨骼肌较短的收缩期需要开发一种新的刺激器，以确保带蒂移植物的收缩能够模拟心肌的收缩。在每组4只狗中，将腹直肌和膈肌包裹在一个球囊周围，并与心电图同步进行电刺激，在收缩期改变刺激电流和放电频率。为此，开发了一种原型混合刺激器，它能感知心脏R波，并通过在收缩期内传递一系列不同频率的脉冲来调节对骨骼肌的电输出。腹直肌和膈肌对这种刺激的收缩特性相似，但由于腹直肌体积较大，其产生的最大张力更高。发现方波输出比正弦波刺激更有效，持续时间为40毫秒的单个刺激电脉冲可产生持续120毫秒的60毫米汞柱的最大张力，而在320毫秒内的4个脉冲序列能够达到持续近400毫秒的100毫米汞柱的最大张力，后者接近心肌的最大张力。在另外6只狗中，使用腹直肌带蒂移植物替换在体外循环下切除的一段左心室（占左心室质量的25.5%±2.1%）。使用带有刺激器开启和关闭的左心室球囊研究左心室等长收缩。当刺激骨骼肌移植物时，左心室最大张力（+19.3%±2.5%，p<0.001，配对t检验）和左心室收缩力（+38.3%±9.4%，p<0.001）显著增强。因此，在这项初步研究中，正确定向和刺激的骨骼肌移植物能够在左心室心肌质量显著损失后增强左心室等长收缩功能。
