Suture Forces for Closure of Transapical Transcatheter Aortic Valve Replacement: A Mathematical Model
Importance:
Transcatheter aortic valve replacement (TAVR) has revolutionized treatment of severe aortic stenosis in high-risk and inoperable patients. TAVR has multiple access routes, transfemoral (TF), transapical (TA), direct aortic (DA), axillary, transcarotid, and transcaval. The most commonly applied algorithm is a TF first approach, where only when patients are unsuitable for TF, are alternatives, such as transapical considered. However, an infrequent, but dreaded risk, is left ventricular (LV) apical bleeding from tearing or rupture with TA approach. With burgeoning transcatheter mitral technology which requires TA, the Holy Grail would be to predict patient-specific risk of apical tearing or rupture based upon myocardial biomechanics.
Objective:
To develop a mathematical model to determine suture forces for transapical closure.
Design:
Preoperative cine-cardiac magnetic resonance imaging (MRI) was used to acquire 3D LV geometry at end-systole and end-diastole. Endo- and epi-cardial boundaries were manually contoured using MeVisLab, a surface reconstruction software. Three-dimensional surfaces of endo- and epi-cardium were reconstructed, and surfaces at end-systole were used to create a 3D LV finite element (FE) mesh. TA access was mimicked by developing a 10mm defect within the LV FE model. LV apex was closed using a virtual suture technique in FE analysis with application of two virtual sutures. After virtual closure, FE analysis was performed of LV model diastolic filling and systolic contraction.
Setting:
This pilot study was performed using the clinical TAVR program from San Francisco VA Medical Center.
Participants:
Severe aortic stenosis patient eligible for TAVR was recruited.
Exposure:
TAVR patient was consented for preoperative research MRI.
Main Outcome Measure:
To determine suture forces for closure of transapical access.
Results:
Proof of concept was achieved to develop an LV transapical access site and perform FE analysis to achieve closure. FE method of virtual suture technique successfully approximated LV apical defect. Peak axial force on virtual sutures at end-diastole and end-systole was 0.445N and 0.736N, respectively.
Conclusions:
We mathematically developed a LV TA access model that evaluated suture tension of the transapical closure process. Further development of this approach may be useful to risk-stratify patients in the future for LV apical tearing.
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