Bioprosthetic interstrut distance subtending the preserved anterior mitral leaflet mitigates left ventricular outflow tract obstruction

Laurencie Brunel; Zoe A Williams; Niek J Beijerink; Benjamin M Robinson; Innes K Wise; Hugh S Paterson; Paul G Bannon

doi:10.1016/j.xjon.2021.05.005

Bioprosthetic interstrut distance subtending the preserved anterior mitral leaflet mitigates left ventricular outflow tract obstruction

JTCVS Open. 2021 May 21:8:251-258. doi: 10.1016/j.xjon.2021.05.005. eCollection 2021 Dec.

Authors

Laurencie Brunel¹, Zoe A Williams², Niek J Beijerink¹, Benjamin M Robinson³, Innes K Wise⁴, Hugh S Paterson², Paul G Bannon^{3

5}

Affiliations

¹ School of Veterinary Sciences, Faculty of Sciences, The University of Sydney, Sydney, NSW, Australia.
² DVC Research Portfolio, The University of Sydney, Sydney, NSW, Australia.
³ Institute of Academic Surgery, Royal Prince Alfred Hospital, Sydney, NSW, Australia.
⁴ Department of Laboratory Animal Services, The University of Sydney, Sydney, NSW, Australia.
⁵ Central Clinical School, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.

Abstract

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Keywords: AML, anterior mitral leaflet; CI, contractility index; CPB, cardiopulmonary bypass; LV, left ventricle/ventricular; LVOT, left ventricular outflow tract; LVOTO, left ventricular outflow tract obstruction; SAM, systolic anterior motion; animal model; bioprosthetic valve; left ventricular contractility; left ventricular outflow tract obstruction; mitral valve replacement.