Discussion:
In this study, 3D TEE and 2D maximal ASD diameters were found to be
correlated with the device size. 3D Echocardiography has a good ability
to overcome geometric assumptions and the variability in the ASD
measurements.
3D Echocardiography is now widely available and validated protocols for
accurate measurement of different cardiac defects are now established.
Balloon sizing is the widely used and approved technique till the
moment. However, it is thought to overestimate the defect size due
outstretching the defect margins. At the meantime it adds an extra cost
to the procedure besides the prolonged exposure to fluoroscopy.(Zhu et
al., 2000)
Underestimation of the defect size could lead to serious complications
for example device dislodgment. Meanwhile, overestimation of the defect
size is not appropriate too. The routine use of a bigger device has a
safety concerns as it could lead to encroachment on the surrounding
structures. It may result in serious complications like heart block and
aortic erosion.(Zhu et al., 2000)
The main result of this study is the good correlation between the
maximal ASD measurement assessed by 3D-TEE and the device size. We
assumed that the device size was accurate in cases where there was no
residual leak , encroachment on surrounding structures or any major
complications e.g., device dislodgement. We correlated the device size
with the different Echocardiographic maximal diameters.
The correlation between the device size and the Echocardiographic
maximal diameters was higher with 3D TEE than other maximal diameters.
R2 0.72, P ≤0.001
With multiple linear regression analysis, we suggest a formula that can
predict the device size according to the 3D TEE maximal diameter: Device
size = 6.9 + 0.87 x 3D maximal diameter with R2 = 0.72, P ≤0.001 .We can
use 2D TEE maximal diameters but this could have a lower predictive
value than the 3D measurement: Device size =8.9 +0.87 x 2D TEE maximal
diameters R2=0.69, P ≤0.001, However, all these formulas needs to be
validated on a larger number of patients.
Hajizeinali et al compared the 2D TEE maximal diameter with the device
size and suggested a formula to predict the device size using the 2D
maximal diameter. They proposed the following equations to calculate a
device size:
Device size = 2.76 + 1.16 × TEE defect size, R2 = 0.91
Device size = 4.08 + 1.05 × TEE defect size, R2 = 0.91 (Hajizeinali et
al., 2013)
There is some difference between this result and our results. We
attribute this to the difference in sample size, and some technical
aspects; for example, the variability in selecting the device size to be
1-4 mm larger than the defect size.
Hascoet et al suggested that 3D TEE maximal diameter was correlated to
the balloon size. They suggested two formulas BS = 1.07 × 3D TEE max-
0.1 when the ASD shape was oval and BS =1.07 × 3D TEE max+3 when the ASD
shape was round. (P, 0.0001). R2 was 0.78. (Hascoet et al., 2015)
We thought that correlating the 3D maximal diameter directly to the
device size would have an added benefit if the 3D proved efficacy in
accurately assessing the defect size. It reduces the time of the
procedure and minimize radiation exposure and more importantly decreases
the cost.
Another model which was described by (Hascoet et al., 2015) is BS = 4.5
× ASD area+11.5 (P , 0.0001). R2 was 0.74.
Roushdy et al. suggested a formula which used the 3D area and
circumference to predict the device size (Roushdy et al., 2020) . The
suggested formulas were:
a-Device size = 10.8 + 3.95 x 3D ASD area.
b-Device size = 3.85 x 3D ASD circumference −1.02.
However, we used the 3D maximal diameter as it is the previously known
practice and it is easier to apply.
Based upon our results we suggest that 3D TEE can be used solely to
choose the suitable device without the need for balloon sizing .This
will reduce the duration of the procedure, minimize the radiation
exposure, avoid the defect margins distortion that is probable with the
overstretched balloon and more importantly reduces the cost of the
procedure. However, this needs to be validated by a larger study.