Akiba T, Neirotti R, Becker A E
Department of Cardiovascular Pathology, University of Amsterdam, The Netherlands.
J Thorac Cardiovasc Surg. 1993 Jan;105(1):142-6.
The study was initiated by reports on right ventricular outflow tract obstruction in complete transposition of the great arteries after an arterial switch repair. We investigated 39 heart specimens with native, unoperated transposition of the great arteries. Of these, 14 hearts had a ventricular septal defect; 25 had an intact ventricular septum. In each heart specimen the narrowest site of the subaortic outflow tract was measured and compared with the circumference of the aortic orifice. Obstruction was considered to be present if the outflow tract circumference was less than that of the aortic orifice. In addition, the diameter of the ascending aorta immediately above the level of the valve orifices was measured and compared with that of the pulmonary trunk. An obstruction was present in the subaortic right ventricular outflow tract of two hearts (5.1%): one of the obstructions, in a neonatal heart with intact ventricular septum, was caused by a prominent supraventricular crest and anterior trabeculations; the other obstruction was an additional extensive muscular hypertrophy, in the heart of a 13-year-old patient with a similar anatomy, and a septal defect. A mismatch between the diameters of the ascending aorta and the pulmonary trunk was present in 15 of 32 hearts measured. Our observations and a review of the literature confirm that subvalvular right ventricular outflow tract obstruction in hearts with native transposition of the great arteries is infrequent. Nevertheless, the anatomic characteristics of the right ventricular outflow tract are such that the tract is intrinsically narrow and muscular hypertrophy may easily lead to obstruction. After an arterial switch operation, subvalvular obstruction could be caused by dynamic processes analogous to those observed after relief of isolated pulmonary valve stenosis. Anatomic subvalvular obstruction could be due to either an obstruction that was not identified before operation or (a purely speculative hypothesis) subtle degrees of mismatch in size between the proximal aorta and the pulmonary trunk, which may be considered irrelevant at time of operation but may also set into pace a process of ongoing adaptive infundibular hypertrophy.
该研究始于关于大动脉完全转位经动脉调转修复术后右心室流出道梗阻的报告。我们研究了39例未经手术的大动脉转位的心脏标本。其中，14例心脏有室间隔缺损；25例心脏室间隔完整。在每个心脏标本中，测量主动脉下流出道最窄部位并与主动脉口周长进行比较。如果流出道周长小于主动脉口周长，则认为存在梗阻。此外，测量瓣膜口水平上方紧邻的升主动脉直径并与肺动脉干直径进行比较。2例心脏（5.1%）的主动脉下右心室流出道存在梗阻：其中一例梗阻发生在室间隔完整的新生儿心脏，由突出的室上嵴和前部小梁引起；另一例梗阻是一名13岁解剖结构类似且有室间隔缺损患者心脏中额外的广泛肌肉肥厚。在测量的32例心脏中，15例存在升主动脉与肺动脉干直径不匹配。我们的观察结果及文献回顾证实，大动脉转位心脏的瓣膜下右心室流出道梗阻并不常见。然而，右心室流出道的解剖特征使其本质上狭窄，肌肉肥厚可能容易导致梗阻。动脉调转手术后，瓣膜下梗阻可能由与孤立性肺动脉瓣狭窄解除后观察到的类似动态过程引起。解剖性瓣膜下梗阻可能是由于术前未识别的梗阻或（一种纯粹的推测性假设）近端主动脉与肺动脉干之间细微的尺寸不匹配，这在手术时可能被认为无关紧要，但也可能启动持续的适应性漏斗部肥厚过程。
