Methods:
All patients who underwent isolated SAVR with a tissue valve between
January 2012 and January 2020 were included in this study (n= 154).
Patients were excluded if they had prior cardiac surgery before the SAVR
or did not have adequate MDCT images for analysis. (Figure 1) Clinical
information was collected from the patient chart and surgical reports.
MDCT images were analyzed by two experienced readers. Each reader was
randomly assigned half of the scans to interpret. CT readers were
blinded to patient data/operative reports.
Surgical Aortic Valve Replacement
All operations were performed using cardiopulmonary bypass with mild
systemic hypothermia (30-34 °C). The majority of procedures were
performed with a mini-sternotomy or right thoracotomy, though there were
~20% with full median sternotomy. Intraoperative
assessment of the aortic annulus size was conducted after resection of
the aortic valve cusps and complete debridement of the calcifications.
The sizing obturator was then inserted into the annulus and the largest
size valve possible was chosen. The replica end of the sizer was then
used to ensure correct valve size. No patients underwent aortic root
surgery, coronary artery bypass grafting (CABG) or coronary
re-implantation (isolated SAVR only). Valve type was left up to the
discretion of the operator. The majority of valves implanted were
Edwards Magna Ease.
Annulus/Sinus/Root Measurements
To detect the annulus we obtained two measurements during an
end-systolic phase. The annulus was defined as the virtual basal plane
of attachment for the aortic valve leaflets. Measurements of the sinus
of Valsalva (SOV), sinotubular junction (STJ) and coronary heights were
obtained during diastolic phases.
Valve Sizing for MDCT measurements and Assessment for Future ViV
Feasibility
We assumed that the sizer (which corresponds to the outer diameter of
the valve frame) cannot be forced into an annulus smaller than the valve
sizer (i.e.- an average diameter of 24.5 would not be able to
accommodate a 25mm valve, so it would be sized for a 23mm valve). Based
on the MDCT, we used the average annulus diameter to predict surgical
valve sizing as follows;
Average diameter of 19.0 to 20.9mm= Valve size 19mm
Average diameter of 21 to 22.9mm= Valve size 21mm
Average diameter of 23 to 24.9= Valve size 23mm
Average diameter of 25 to 26.9= Valve size 25mm
Average diameter of 27 to 28.9= Valve size 27mm
Averaged diameter >29mm= Valve size 29mm.
We then implanted a virtual valve with the same dimensions as a
Carpentier-Edwards Magna Ease at the level of the annulus. We used this
valve since it is the most common valve used at our institution.
Subsequently, we were able to calculate a virtual valve to coronary
ostial distance (VTC) and determine if the patient would be at risk for
sinus sequestration, sealing of the aortic root with the virtual valve.
We considered patients high risk for future ViV if VTC was
<4mm and/or the virtual struts contacted the STJ without room
for blood flow around. (6) (FIGURE 2, FIGURE 3)
MDCT Measurements versus Intraoperative Measurements
An important part of virtual valve placement is ensuring that we are
placing a proper sized surgical valve. If our measurements on MDCT
cannot predict actual valve implanted, then virtual valve sizing may be
misguiding. Furthermore, the ability to properly predict SAVR size may
be important for procedural planning (i.e.- in patients with small
annuli, they might require root enlargement to reduce the risk of
patient prosthesis mismatch (PPM)). We therefore evaluated how often we
predicted the correct SAVR size implanted. We also assessed the
correlation strength between annular diameter, area and perimeter
compared to actual valve size implanted.
Statistical Analysis
For patient characteristics, continuous variables were reported as mean
with standard deviation (SD) and compared between two groups using a
2-sample independent t tests or Mann–Whitney U test (non-uniform data).
A Pearson coefficient of determination (R2) for all
diameters, area and perimeter acquired by MDCT imaging was used for
comparison with the intraoperative valve chosen. R2values were considered very weak if <0.3, weak if 0.3-0.5,
moderate if 0.5-0.7, strong if >0.7. (Moore D.S et al) P
values ≤0.05 were considered statistically significant. All statistical
analyses were performed with the use of SAS software, version 9.2 (SAS
institute, Cary, NC).