Results
In this cohort of 21,336 unique patients aged 50-85 years who underwent
CT including the chest (49.3% (n=10,508) were CT scans with intravenous
contrast and 2.5% (n=540) were EKG-gated) for any clinical indication,
arch anomalies were reported in 2.8% (n=603 patients). Bovine arch was
the most common variant (n=354, 58.7% of all anomalies), followed by
aberrant right subclavian artery (n=147, 24.4%), aberrant left
vertebral artery (n=95, 15.8% ), aberrant left subclavian artery
combined with right sided arch (n=12, 2%), double arch (n=1, 0.2%),
pseudocoarctation (n=1, 0.2%) (Figure 1). Aberrant left subclavian
artery arising from Kommerell’s diverticulum was noted in 5 patients and
aberrant right subclavian artery arising from Kommerell’s diverticulum
was reported in 3 patients. On bivariate analysis, patients with arch
anomalies were more likely to be females (p<0.001),
non-Caucasian (p<0.001), hypertensive (p<0.001),
diabetic (p=0.012), had hyperlipidemia (p=0.037), and with significantly
higher prevalence of aortic valve disease (p<0.001) and TAA
(p<0.001). Patients with arch anomalies less commonly had
history of smoking and COPD (Table1).
The prevalence of TAA disease was different according to the type of
arch anomaly (Figure 3). Subjects with aberrant left subclavian artery
combined with right sided arch had the highest prevalence of TAA (33%
versus 4.4%; 4 out of 12 patients; P<0.001), followed by
bovine arch (13% versus 4.4%,; 46 out of 354 patients with bovine
aortic arch; P<0.001), and aberrant right subclavian artery
(8% versus 4.4%; 12 out of 147 patients with aberrant right subclavian
artery; P<0.001). Aberrant left vertebral artery was not
associated with increased prevalence of TAA (3% versus 4.4%; 3 out of
95 patients with aberrant left vertebral artery; P=0.99). The regional
distribution of TAA was not different between the arch anomaly group and
the no anomaly group. TAA in both groups were more likely to affect the
ascending aorta > descending aorta > aortic
root > aortic arch (Figure 2). The aortic diameter in the
respective region was also not different between the 2 groups. In the
region of the root: mean aortic diameter was 4.2 ± 0.3 cm versus 4.3 ±
0.4 cm, P=0.68; in the ascending aorta: 4.3 ± 0.3 cm versus 4.3 ± 0.4
cm, P=0.92; in the arch: 4.6 ± 0.5 cm versus 4.6 ± 0.7 cm, P=0.96; and
in the descending aorta: 3.6 ± 0.6 cm versus 3.7 ± 0.8 cm, P=0.60. In
the validation sample, 49 cases were previously known to have TAA and
were excluded from the analysis. In the remaining 151 scans, 32 patients
were found to have bovine arch (prevalence=21%). Type 1 arch was
present in 28 cases and type 2 was present in 4 cases. Also, the
aberrant left vertebral artery was encountered in 10 patients (6.6%).
Other anomalies were not encountered in the validation sample.
To define independent risk factors for TAA and dilatations, a
multivariable logistic regression analysis was performed. The model
included patient’s age, male sex, Caucasian race, BSA, smoking,
hypertension, hyperlipidemia, COPD, aortic valve disease, and arch
anomalies. Age (OR = 1.04 CI[1.03-1.05]), male sex (OR = 2.38
[2.01-2.80]), BSA (OR = 1.45 [1.13-1.86]), hypertension (OR =
1.47[1.25-1.73]), aortic valve disease (OR = 2.93 [2.31-3.73]),
and arch anomalies (OR = 2.85 [2.16-3.75]) were independent risk
factors for TAA (Figure 4).