Jarrod Yates, DO,
John Salanitri, MD, FRANZCR,
Department of Radiology, Evanston Northwestern Hospital,
A 63-year-old man with known aortic stenosis and increasing
fatigue on exercise was evaluated prior to undergoing aortic valve
replacement. Echocardiography revealed critical aortic stenosis
with a valve area of 0.77 cm
, a mean transvalvular gradient of 55 mm Hg, and a peak forward
velocity of 4.9 m/sec (not shown). Cardiac catheterization
confirmed the presence of severe aortic stenosis and was suggestive
of an ascending aortic aneurysm with a diameter of 6 cm (not
shown). The left main coronary artery could not be cannulated and
was thought to be absent. Mild 3-vessel atherosclerotic coronary
artery disease was present. Thoracic aortic computed tomography
angiography (CTA) was requested to determine the true aneurysm size
prior to operative intervention.
As the patient was in sinus rhythm with a heart rate of 65 bpm,
an electrocardiographic (ECG)-gated thoracic aortic CTA was
performed on a 64-slice MDCT (LightSpeed VCT 64-slice scanner, GE
Healthcare, Waukesha, WI). The entire chest was scanned with
0.625-mm slices in a 9second breath-hold using 90 mL of contrast
injected at 5 mL/sec. A single data set was reconstructed in the
mid-diastolic phase (75% R-R interval) and was analyzed on an
advanced workstation (AWS 4.2, GE Healthcare), with multiplanar
reformats, volume rendering, and vessel analysis performed.
A fusiform aneurysm of the ascending aorta that measured 4.8 cm
in maximum diameter was identified with no evidence of dissection,
significant mural thrombus, or coarctation (Figure 1). The aortic
valve was found to have a bicuspid configuration with heavy
calcification of both annulus and cusp margins (Figure 2).
The absence of the left main coronary artery was confirmed along
with mild ostial stenoses of both the left anterior descending and
left circumflex coronary arteries, which had separate origins from
the left sinus of Valsalva (Figure 3A). The right coronary artery
was found to have mild mixed-density plaque in its proximal and mid
portions with no severe focal stenosis identified (Figure 3B and
Subsequent surgery confirmed the bicuspid aortic valve, which
was replaced along the ascending aorta. Bypass grafts were placed
to the right coronary and left anterior descending arteries. The
patient made an uneventful recovery.
Calcific aortic stenosis, bicuspid aortic valve, ascending
aortic aneurysm, absent left main coronary artery, and coronary
artery atherosclerotic disease
Bicuspid aortic valve occurs in 0.5% to 2% of the general
population and is the most common cause of congenital aortic
stenosis, with degenerative calcification commencing in the fourth
decade of life. Bicuspid aortic valves have a male preponderance
and may be associated with aortic arch coarctation, atresia, or
interruptions as well as hypoplastic heart syndrome. The
identification of aortic valve calcifications implies a severe
degree of stenosis with a pressure gradient >50 mm Hg.
Dilatation of the ascending aorta, which may be aneurysmal (>4
cm diameter), is attributed to jet phenomena caused by the narrowed
valve orifice; however, the degree of aortic dilatation does not
correlate with the severity of the valvular stenosis.
The use of ECG-gated CT can help to determine the valve morphology,
accurately measure the valve annulus diameter, and assess the
severity of the degree of valve leaflet calcification.
Non-ECG-gated helical thoracic CT has long been used to diagnose
thoracic aortic pathology including aneurysm, dissection, and
coarctation. Pseudodissection artifacts due to aortic motion during
the cardiac cycle are well recognized, simulating the appearance of
an ascending aortic dissection.
The use of ECG-gating during image acquisition eliminates this
artifact and permits more accurate measurement of the aneurysm and
aortic valve annulus diameter, as the images are motion-free. This
obviously has important significance for preoperative planning.
The absence of the left main coronary artery with separate ostia
for the left anterior descending and left circumflex arteries is an
uncommon coronary artery anomaly with an incidence of 0.4% in a
series of 20,332 consecutive coronary angiograms.
This anomaly is not associated with an increased incidence of
congenital heart disease, nor is there an increased incidence of
coronary artery disease. Knowledge of this anomaly is important
prior to aortic valve replacement, as both vessels may need
selective bypass grafting.
In many published series, ECG-gated coronary CTA has been shown
to have high sensitivity and specificity for the detection and
grading of coronary artery stenoses, particularly in noncalcified
vessel segments, with increasing accuracy with more sophisticated
multidetector scanners (ie, 16- or 64-slice CT).
With the improving temporal resolution of ECG-gated coronary CTA,
gated functional analysis of the moving aortic valve leaflets may
be possible, in a manner similar to cine magnetic resonance
With the use of high-performance workstation analysis, ECG-gated
contrast-enhanced thoracic aortic CTA accurately measured the
diameter of the ascending aortic aneurysm secondary to an
identified heavily calcified bicuspid aortic valve. The absence of
the left main coronary artery was elegantly visualized along with
multivessel coronary artery disease, which was not considered to be
hemodynamically significant. In the future, ECG-gated CTA may
become the first-line investigation required prior to aortic valve
replacement, since it provides evaluation of the aortic valve,
thoracic aorta, and coronary arteries in a single, minimally