doi: 10.1016/j.jcmg.2016.01.017. Epub 2016 May 18.
Predicting LVOT Obstruction After TMVR
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- PMID:27209112
- PMCID: PMC5106323
- DOI: 10.1016/j.jcmg.2016.01.017
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Predicting LVOT Obstruction After TMVR
Dee Dee Wang et al. JACC Cardiovasc Imaging.2016 Nov.
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Keywords: 3D print; LVOT obstruction; computer aided design; transcatheter mitral valve replacement.
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Pre-procedural imaging utilizes a contrast-enhanced, retrospectively electrocardiogram-gated computed tomography (CT) angiography acquisition without application of electrocardiogram-dose modulation (Table 1). Four-dimensional cine clips of the mitral annulus (MA) motion are generated. The MA plane is defined as the basal-most insertion of the mitral leaflets, characterized by a hinge-point motion of the leaflet base during the mid-to-late diastolic phase of the cardiac cycle, or in the case of a degenerative mitral ring/bioprosthesis, by prosthesis-artifact on CT. Using the double-oblique method, crosshairs are aligned to the MA plane in sagittal and coronal cross-sections (A and B) allowing for MA dimensions to be obtained on axial thin sections (C). Once the proposed THV size is identified, computer-aided design (CAD)-generated Sapien, Sapien XT (SXT) and Sapien 3 valves (Edwards Lifesciences, Irvine, California) are then virtually tested on-screen and again physically in the patient’s 3DP anatomy to confirm sizing and estimate risk of LVOT obstruction (D). For difficult to-conceptualize computer-based 3D imaging anatomy, 3DP THV models were implanted into the 3DP patient-specific systolic left ventricular outflow tract (LVOT) model to help the structural heart team visualize the predicted LVOT obstruction to anatomical scale. HU = Hounsfield unit(s); TAVR = transcatheter aortic valve replacement; 3D = 3-dimensional; 3DP = 3-dimensionally printed; TMVR = transcatheter mitral valve replacement.
The blood volume of the mid-to-late systolic phase demonstrating the smallest LVOT surface area between the basal anteroseptal wall of the LV and the most inferior/ventricular hinge of the anterior mitral leaflet or surgical frame strut is segmented out for 3D modeling. CAD models are generated with the proposed THV deployed in different LV landing zones (60% LV/40% atrial to 80% LV/20% atrial) within the patient’s MA/ring (A). In the setting of surgical bioprosthesis, modeling is performed with 0% defined within the confines of the inferior border of the surgical prosthesis strut, and 10% as inferior to the surgical prosthesis plane into the LV. The post-TMVR residual LVOT, “neo-LVOT,” surface area is then calculated for proposed THV by various depths of LV deployment and angulations of THV delivery system toward/away from aortic outflow tract (B and C). In order to predict percentage of LVOT obstruction, the ratio of neo-LVOT to native LVOT surface area is calculated: (native LVOT area – neo LVOT area)/native LVOT area. Abbreviations as inFigure 1.
Preliminary data utilizing 2-dimensional (2D) echo imaging correlated acute angulation of the mitral aorta-outflow-angle (mAOA) with higher risk of LVOT obstruction compared with that of more obtuse mAOA. On the basis of our single-center experience, the association between mAOA and risk of LVOT obstruction was not reproducible (A and B). LVOT obstruction is not solely dependent on mAOA. Personalization and determination of feasibility of TMVR in patient-specific anatomy may not be accounted for if relying on 2D measurements of a 3D anatomy (A). CT and CAD 3DP analysis of the “neo-LVOT” surface area overcomes the limitations of traditional 2D imaging planes. THV implantation in the mitral position results in permanent anterior motion/displacement of the surgical/native anterior mitral leaflet. Both THV frame and permanent anterior motion/displacement can result in severe LVOT obstruction (C). The importance of understanding the application of this technology is the ability to test devices in patient-specific cardiac anatomy ex vivo for LVOT encroachment. Abbreviations as inFigure 1.
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