Timing of the narrowest neoLVOT with trans-catheter mitral valve implantation, a cardiac computed tomography study
Authors: Mahmoud-Elsayed H , Emam A Y , Hekal S , Thabet N , Shaaban M N , Bahaa H , Elguindy A 
Published: June 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Trans-catheter mitral valve replacement (TMVR) procedures had emerged as an alternative solution for patients who have surgical high risk for mitral valve surgery. One of the main challenges faced during the percutaneous approach is the degree of left ventricular outflow tract (LVOT) narrowing after implanting the new percutaneous mitral prosthesis. The remaining LVOT area (NeoLVOT) can be estimated by a commercially available CT analysis software that allows the insertion of a virtual valve within the CT dataset in the native annulus and/or the degenerated bioproshesis and hence allows measurement of the NeoLVOT using the multi-planar reconstruction (MPR) mode.
The systolic phase that shows the narrowest NeoLVOT is not fully understood, and hence there is a considerable variability between operators in choosing the best phase in systole at which they should insert the virtual valve within the mitral annulus in the CT dataset to measure the narrowest NeoLVOT.

Purpose
To detect the systolic phase that shows the narrowest NeoLVOT and hence standardize the way to use the software to decrease variability among operators.

Methods
A retrospective observational single center study, including 20 patients (age 62± 4 years, 70% men), who had undergone a clinically indicated cardiac computed tomography (CT). All these patients were in sinus rhythm, had no significant coronary artery disease bases on CT report, and had normal left ventricular systolic function with no regional wall motion abnormalities, we excluded patients who had previous cardiac surgeries, hypertrophic cardiomyopathy, significant pulmonary hypertension or congenital heart disease that may affect septal motion.
CTs were performed using a 128 slice dual-source (Somatom Definition Flash, Siemens Healthineers, Erlangen, Germany) with a retrospective ECG-gated acquisition
CT analysis was done by a single operator using the commercially available software (3mensio Structural Heart 10.3, Pie Medical Imaging, The Netherlands).
Multiphase scans were used and mid-diastole (80%), early-systole (10%), mid-systole (20%), late-systole (30–40%) were identified and analysed.
Measurements done were; mitral annulus (MA) antero-posterior (AP) diameter, inter-commissural (IC) diameter, annulus area (Area), annulus perimeter (Peri), aorto-mitral angel, and the NeoLVOT area. (Figure 1).

Results
All measurements were feasible in all phases for all patients. The neoLVOT area was significantly narrower at end-systole (224 ± 62mm²), compared to early-systole (299 ± 70mm²) & mid-systole (261 ± 75 mm²), (p = 0.005). All other measurement did not show statistically significant changes despite taking certain trends. (Figure 2).

Conclusions
End-systole is the cardiac phase that shows the narrowest predicted Neo-LVOT area and hence it should be the standard phase to be used during CT analysis before TMVR to predict the narrowest NeoLVOT.