Macoviak J A, Stephenson L W, Spielman S, Greenspan A, Likoff M, Sutton M S, Reichek N, Rashkind W J, Edmunds L H
J Thorac Cardiovasc Surg. 1981 Apr;81(4):519-27.
A pedicled diaphragmatic skeletal muscle graft was used to replace a portion of resected right ventricle in 35 dogs. The graft contracted when electrically stimulated directly or via the phrenic nerve before and after insertion. The electrical pacing threshold was lower for phrenic nerve stimulation (0.9 +/- 0.20 mamp) than for direct graft stimulation (2.3 +/- 1.19 mamp). The heart could be captured and paced by stimulating the muscle graft with higher current (16.2 +/- 4.49 mamp). The delay from pacing stimulus to muscle graft contraction when the graft was paced directly was 10 msec. The epicardial activation time delay when the heart was paced through the muscle graft was 27.0 +/- 9.08 msec. When the muscle graft pedicle was transected, the graft lost its ability to contract. The heart, however, could still be captured electrically through the graft for up to 4 hours. Strain gauge studies of the nonstimulated muscle graft showed tension development during pre-ejection ventricular contraction identical to that of the right ventricle. In the ejection phase, muscle graft tension slowly declined. The stimulated muscle graft developed active tension and echographically demonstrated muscle thickening during contraction. This study demonstrates that a vascularized, neurally innervated diaphragmatic muscle graft can be placed into the right ventricle. The graft retains its ability to contract in response to direct or phrenic nerve stimulation. It can be made to contract during any phase of the cardiac cycle. Thus diaphragmatic muscle grafts may provide a method to augment ventricular cavity size with synchronously contracting muscle.
在35只犬中，采用带蒂膈部骨骼肌移植物替代部分切除的右心室。在植入前后，直接或通过膈神经进行电刺激时，移植物会收缩。膈神经刺激的电起搏阈值（0.9±0.20毫安）低于直接移植物刺激的阈值（2.3±1.19毫安）。通过更高电流（16.2±4.49毫安）刺激肌肉移植物可使心脏被捕获并起搏。直接刺激移植物时，从起搏刺激到肌肉移植物收缩的延迟为10毫秒。通过肌肉移植物起搏心脏时，心外膜激活时间延迟为27.0±9.08毫秒。当切断肌肉移植物的蒂时，移植物失去收缩能力。然而，心脏仍可通过移植物进行电捕获长达4小时。对未受刺激的肌肉移植物进行应变计研究表明，在心室射血前期收缩过程中，其张力发展与右心室相同。在射血期，肌肉移植物的张力缓慢下降。受刺激的肌肉移植物产生主动张力，超声心动图显示收缩时肌肉增厚。本研究表明，血管化、有神经支配的膈部肌肉移植物可植入右心室。该移植物保留了对直接或膈神经刺激作出收缩反应的能力。它可在心动周期的任何阶段收缩。因此，膈部肌肉移植物可能提供一种通过同步收缩的肌肉来增大心室腔大小的方法。
