Brunel Laurencie, Williams Zoe A, Beijerink Niek J, Robinson Benjamin M, Wise Innes K, Paterson Hugh S, Bannon Paul G
School of Veterinary Sciences, Faculty of Sciences, The University of Sydney, Sydney, NSW, Australia.
DVC Research Portfolio, The University of Sydney, Sydney, NSW, Australia.
JTCVS Open. 2021 May 21;8:251-258. doi: 10.1016/j.xjon.2021.05.005. eCollection 2021 Dec.
The anterior mitral leaflet (AML) contributes to left ventricular (LV) function but is normally excised at the time of a bioprosthetic valve insertion. This study aimed to investigate methods of safely retaining the AML at the time of mitral valve replacement.
Five adult sheep (57 ± 3.8 kg) each underwent 3 insertions of a bioprosthetic mitral valve (asymmetric interstrut sectors) alternating the wide and narrow interstrut distance under the AML. Each insertion was performed on normothermic beating-heart cardiopulmonary bypass, with full retention of the native valve. After each valve insertion, continuous measurements of LV and aortic pressures were recorded with echocardiographic assessment of mitral valve function. If LV outflow tract obstruction (LVOTO) was not seen on the resumption of normal cardiac output, a bolus of adrenaline was given to precipitate it.
Thirteen of 15 valve insertions resulted in LVOTO caused by systolic anterior motion (SAM), independent of valve orientation. The wide interstrut distance subtending the AML was associated with a greater requirement for inotropic stress to precipitate an obstruction and was associated with late systolic rather than holosystolic obstruction.
The predisposition to and nature of LVOTO due to SAM were associated with the bioprosthetic valve interstrut distance subtending the fully retained AML and may explain the survival differences in such patients. This model represents an effective method for research into prevention of LVOTO following mitral valve replacement with preservation of the native valve.
二尖瓣前叶（AML）对左心室（LV）功能有贡献，但在生物瓣膜植入时通常会被切除。本研究旨在探讨在二尖瓣置换时安全保留AML的方法。
5只成年绵羊（体重57±3.8千克），每只均接受3次生物二尖瓣瓣膜（不对称支柱间扇形区）植入，在AML下方交替采用宽支柱间距和窄支柱间距。每次植入均在常温跳动心脏体外循环下进行，保留天然瓣膜。每次瓣膜植入后，连续测量左心室和主动脉压力，并通过超声心动图评估二尖瓣功能。如果在恢复正常心输出量时未发现左心室流出道梗阻（LVOTO），则给予一剂肾上腺素以诱发梗阻。
15次瓣膜植入中有13次导致由收缩期前向运动（SAM）引起的LVOTO，与瓣膜方向无关。AML下方的宽支柱间距与诱发梗阻所需的更大的正性肌力应激相关，并且与晚期收缩期而非全收缩期梗阻相关。
SAM导致的LVOTO的易感性和性质与覆盖完全保留的AML的生物瓣膜支柱间距有关，这可能解释了此类患者的生存差异。该模型是研究保留天然瓣膜的二尖瓣置换术后预防LVOTO的有效方法。
