Department of Genetics and Morphology, Brasilia University, Brasilia, Brazil.
University of Birmingham, University College Birmingham, Institute of Clinical Sciences, Birmingham, United Kingdom.
Heart Rhythm. 2020 Jan;17(1):123-130. doi: 10.1016/j.hrthm.2019.07.033. Epub 2019 Aug 1.
The right ventricular outflow tract is the most common source of ventricular arrhythmias in nonstructural heart disease. Most of these arrhythmias are of endocardial origin, but their morphologic substrate is mostly unknown.
The purpose of this study was to identify potential morphologic substrates for such arrhythmias originating within the right ventricular outflow tract.
Three adult human hearts that had been fixed in 4% formaldehyde were examined. In 2 of the hearts, which were obtained subsequent to necropsies, the base of the anterior papillary muscle of the tricuspid valve was removed at the site of its fusion with the moderator band. The block of removed myocardium was submitted to routine histologic processing and sectioned at 5-μm thickness. The free-standing subpulmonary infundibulum also was removed as a series of macroscopic preparations, which were sectioned in their short axis at 5-μm thickness. The third heart was assessed using microcomputed tomography after it had been stained with 7.5% IKI contrast agent for 14 days, with the contrast agent refreshed on the seventh day.
Specialized conducting cardiomyocytes from the base of the anterior papillary muscle to the supraventricular crest and subpulmonary infundibulum were identified and tracked using histology in 2 hearts and microcomputed tomography in the other. Transitional cells were also found at these sites.
The existence of such specialized cardiomyocytes within the infundibulum is of clinical significance because they could be the morphologic substrate for arrhythmias known to originate from these sites.
右心室流出道是无结构性心脏病患者室性心律失常的最常见来源。这些心律失常大多起源于心内膜，但它们的形态学基质大多未知。
本研究旨在确定起源于右心室流出道的此类心律失常的潜在形态学基质。
检查了 3 例固定在 4%甲醛中的成人心脏。其中 2 例心脏是在尸检后获得的，在三尖瓣前乳头肌与节制带融合处去除前乳头肌的基底。去除的心肌块接受常规组织学处理，并以 5μm 厚度切片。游离的肺动脉下漏斗也作为一系列宏观标本被切除，这些标本以 5μm 的厚度沿短轴切片。第三只心脏在使用 7.5%碘化钾对比剂染色 14 天后，用对比剂在第 7 天刷新后，使用微计算机断层扫描进行评估。
通过 2 只心脏的组织学和另一只心脏的微计算机断层扫描，在从前乳头肌基底到窦上嵴和肺动脉下漏斗的部位识别并追踪到专门的传导性心肌细胞，并且在这些部位还发现了过渡细胞。
漏斗内存在这种专门的心肌细胞具有临床意义，因为它们可能是已知起源于这些部位的心律失常的形态学基质。
