Methods
A prospective study was performed on 100 consecutive patients less than
18 years old who were undergoing either CT or MRI of the chest for any
indication. These advanced imaging studies served as gold standard for
diagnosis of AoA anatomy. A priori power analysis was completed assuming
null proportion of successful tracheal imaging of 85% and demonstrated
power > 0.95 with a sample size of 100 when proportion was
97%. If a more conservative null proportion of 90% was used, power
remained significant at > 0.80 with when proportion was
97%.
Four total echocardiographic clips in two separate planes were obtained
for each patient in 2D and color Doppler with Phillips IE33 or Phillips
EPIQ echocardiography machines (Philips Electronics, Washington, USA).
In all patients, a right-to-left sagittal sweep was performed with
echocardiography from the suprasternal notch or high right parasternal
view and used to categorize 1) Left AoA = right superior vena cava
(SVC)-trachea-AoA, Figure 1, Video 1; 2) Right AoA = SVC-AoA-trachea,
Video 2; 3) DAA = SVC-AoA-trachea-AoA, Video 3. A parasternal short-axis
view at the base of the heart showing the PA bifurcation straddling the
trachea was used to rule out PA sling, Video 4. No additional
echocardiography images were obtained as a part of this study. Study
approval was granted by the University of Iowa institutional review
board. Age appropriate consent/assent was obtained on the day of
advanced imaging to participate in additional research-only
echocardiographic images completed either directly before or after
CT/MRI.
Patient acuity, use of sedation or anesthesia, imager experience, and
subjective ease of obtaining echo were collected. Independent review for
AoA sidedness, DAA, and absence of PA sling was performed by 2
advanced-imaging pediatric cardiologists for all echocardiography images
and advanced imaging scans. Those obtaining echo images and those
reading images were blinded to any previous diagnoses. Kappa coefficient
was calculated to determine inter-reader reliability with independent
read, and then in cases of initial disagreement, consensus was attained
by joint review. Continuous variables were reported as median and range.
Categorical variables were reported as percent. The proportion of
successful imaging of the trachea and diagnostic accuracy with tracheal
sweep were calculated as mean percent values with 95% confidence
interval (CI). A one-tailed z-test was used to assess for statistical
significance. These calculations were repeated for successful imaging of
tracheal-PA bifurcation relationship for both the entire cohort and then
again excluding patients who had previous surgical intervention on their
PA (ie: Glenn/Fontan, RV-to-PA conduit, LeCompte).