is Chief of Cardiothoracic and Endovascular Surgery,
is an Interventional Cardiologist,
is an Interventional Cardiologist,
is Director of Cardiovascular Services, and
is the Medical Director, Founder and President, Cardiovascular
Institute of the South, Lafayette, LA. Mr. Hebert is also the
Director of the Cardiac Cath Lab, Southwest Medical Center,
Dr. Allie and Dr. Walker serve as Consultants to Toshiba, Bracco
Diagnostics, and The Spectranetics Corporation. Dr. Patlola and
Dr. Ingraldi have nothing to disclose. Mr. Hebert is a Consultant
to The Spectranetics Corporation.
It is estimated that there are 15 to 20 million patients with
peripheral vascular disease (PVD) in the United States.
Likewise, there are 20 million patients with diabetes mellitus and
a similar number of patients with peripheral venous disease. These
patient populations make the clinical opportunity in peripheral
vascular (PV) computed tomographic angiography (CTA), or PV-CTA,
even greater than it is for cardiac CTA.
It is estimated that 3 to 4 million symptomatic PVD patients are
misdiagnosed or go untreated and that twice that number are
asymptomatic and therefore untreated.
This asymptomatic group includes patients with abdominal aortic
aneurysm (AAA), significant internal carotid artery (ICA) and
vertebral artery disease, renal artery stenosis (RAS), and
mesenteric vascular disease. Peripheral vascular CTA is the ideal
noninvasive tool to identify this large, asymptomatic, yet at-risk
patient population for whom endovascular therapeutic treatments are
now available. Therefore, earlier PVD diagnosis and treatment
facilitated by PV-CTA have the potential to significantly improve
Conventional angiography with digital subtraction angiography
(DSA) remains the gold standard for vascular imaging but has
multiple limitations. Magnetic resonance angiography (MRA) has been
advocated to address the limitations of DSA, but MRA also possesses
significant limitations. This article reviews the contemporary
utilization of PV-CTA and describes the authors' experience with
64-channel PV-CTA. CTA has the potential to become a paradigm shift
in not only the diagnostic, but also the overall therapeutic
management of PVD.
PV-CTA imaging technique
Current 64-channel CTA imaging acquisition and injection
parameters are primarily tailored to cardiac and coronary
pathology. In clinical CTA, the contrast enhancement, acquisition
parameters, coverage speed, and circulating time are accurately
determined by protocols that are based on the clinical information
requested, the imaging modality used, and the patient-specific
variables (age, body size, cardiac output, renal function, etc.).
Therefore, these rapid scan and acquisition times oftentimes are
not optimal for PVD. Optimal contrast enhancement and image
acquisition in PVD patients require 64-channel CTA injection
parameter adjustments to "slow down" or "time" the data acquisition
to the slower blood ﬂow rates in the PVD patient,
especially those with significant infrapopliteal disease. Our group
has reported low-contrast 64-channel CTA protocols in patients with
PVD and critical limb ischemia (CLI).
The PV-CTA protocol also serves as our CLI-CTA protocol by
adding a second below-the-knee scan for infrapopliteal imaging
enhancement. We reported our results of a comparison of DSA versus
CTA in 140 PVD and 98 CLI patients. The DSA versus CTA % stenosis
correlations were strong and included: carotid (r
= 0.957), renal (r
= 0.942), celiac (r
= 0.907), mesenteric (r
= 0.909), iliac (r
= 0.951), superior femoral (r
= 0.903), popliteal (r2 = 0.889), peroneal (r
= 0.882), anterior tibial (r
= 0.907), and posterior tibial (r
Integral to these PV-CTA protocols are the higher iodinated
contrast agents, injection parameter changes, second lower
extremity scans, and low contrast volume while facilitating
postprocessing resolution and image enhancement.
Clinical PV-CTA applications
Carotid artery disease
Conventional angiography with DSA remains the gold standard for
ICA imaging but has a definite risk of periprocedural stroke.
Digital subtraction angiography is performed in limited
projections, while CTA provides multiple3-dimensional (3D) views.
Digital subtraction angiography has been shown to underestimate the
degree of ICA stenosis when surgical specimens of cross-sectional
lumens were compared with the results of DSA.
Using helical CTA, Elgersma et al
identified additional ICA (16%) suitable for carotid endarterectomy
(CEA) compared with DSA, therefore further underscoring the
complexity of the ICA bifurcation and the need for multiple views
to accurately determine the degree of stenosis. Likewise, mounting
evidence suggests that carotid plaque morphology characteristics
are associated with outcomes and clinical events.
Carotid CTA holds promise in facilitating this determination and,
therefore, has significant clinical therapeutic treatment
Carotid duplex ultrasound (DU) has been known to have >90%
sensitivity and specificity in diagnosing ICA disease but is still
operator-dependent, moderately time-consuming, and gives
information primarily only on ICA bifurcational disease. Several
reports have shown the diagnostic accuracy of carotid CTA in cases
of 70% to 99% ICA stenosis to have a sensitivity of 100% and
specificity of 94% to 100%.
Multiplanar reconstruction (MPR) methods will allow cross-sectional
luminal and plaque morphology evaluation and will provide
additional pertinent clinical information.
Aortic arch vessel anatomy, tortuosity, and ostial arch vessel
disease along with distal ICA tortuosity are often significant
limitations to carotid artery stenting (CAS), since placement of a
distal protection device (DPD) is now considered the standard of
CTA allows accurate assessment of ICA stenosis, access vessel and
distal ICA tortuosity, and the detection of arch vessel disease,
thus potentially allowing a determination of CAS versus CEA
candidacy noninvasively without the inherent risks of DSA.
Excellent proximal vertebral artery imaging is available on a
routine carotid CTA, allowing identification of additional
symptomatic patients with vertebral artery symptoms who could
benefit from vertebral artery percutaneous transluminal angioplasty
(PTA) or stenting. Carotid CTA has replaced traditional angiography
as our carotid system diagnostic tool of choice, and increasingly
important carotid therapeutic treatment and surveillance decisions
are made relying solely on CTA information (Figure 1).
Renal artery disease
The benefits of RAS diagnosis and revascularization have been
proven in patients with severe hypertension, refractory congestive
heart failure, or angina, and in patients with declining renal
function, which underscores the importance of a simple accurate,
noninvasive diagnostic tool. The limitations of renal artery DU are
well known. Three-dimensional abdominal CTA has addressed many of
these limitations, and Beregi et al
recently reported 100% accuracy and sensitivity comparing the use
of CTA with DSA in RAS. Galanski et al
reported the sensitivity and specificity of CTA versus DSA in RAS
as 92% and 95%, respectively. Abdominal CTA is rapidly replacing DU
and MRA as the primary diagnostic and surveillance tool in
evaluating RAS, especially for in-stent restenosis (ISR). In
patients with RAS, the CTA scanner can pinpoint the juxtarenal
aorta and shorten acquisition times to <10 seconds and reduce
contrast load to <40 mL.
The incidence of renal artery ISR has been reported to be as
high as 15% to 20% and has been associated with vessel size and
Accurate preprocedural knowledge of vessel anatomy and size may
facilitate more precise PTA/stenting and thus decrease ISR. Plaque
morphology and branching anatomy may also facilitate decisions
regarding DPD use, especially in ulcerative lesions. Peripheral
vascular CTA provides an excellent imaging tool for the diagnosis
of and treatment planning for renal artery ISR.
Mesenteric artery disease
Asymptomatic and symptomatic mesenteric artery disease (MAD)
(celiac and superior-inferior mesenteric artery disease) has been
difficult to diagnose, both clinically and by traditional imaging
techniques; therefore, MAD is underappreciated, underdiagnosed, and
undertreated. This is likely analogous to our understanding and
treatment of RAS 2 decades ago. Recent reports have identified the
benefits of PTA/stenting in appropriately diagnosed patients with
There are no reports of 64-channel CTA evaluating MAD, but our
initial experience indicates that CTA will be as accurate in
diagnosing MAD as it is in RAS. Stents are well imaged, allowing
the potential for improved accuracy in detecting MAD ISR, which,
like RAS, has a 15% to 20% incidence
An abdominal aorta CTA with distal runoff begins acquiring
images at the diaphragm level and thus will potentially identify a
significant incidence of MAD. It is likely the incidence of MAD is
as common as RAS and, therefore, will be a new vascular territory
available for PTA/stenting. Traditionally, the treatment of MAD has
required difficult major vascular surgical reconstructions with
high mortalities and morbidities. The endovascular MAD treatment
techniques are very similar to treating RAS.
It is likely that with CTA and endovascular treatments, the
incidence of MAD treatment will increase in the near future with
Aortoiliac occlusive disease
Several studies have shown the sensitivity and specificity of
CTA in detecting significant aortoiliac occlusive disease (AIOD) to
Rubin et al
recently reported 100% concordance between CTA and DSA in AIOD
using 2.5-mm slices covering 120 mm in a 30-second acquisition
time. Digital subtraction angiography can fail to detect aneurysmal
disease, and the diagnostic accuracy is adversely affected by
vascular calcification. Single planar DSA frequently "misses"
eccentric lesions, which are prevalent posteriorly at the distal
aortic bifurcation and the entire iliac artery segment. CTA has
been shown to be superior to DSA in evaluating vascular trauma,
dissections, and aneurysms. Recent reports have shown a reduction
in contrast use and a 4-fold reduction in radiation exposure when
comparing CTA with DSA for the diagnosis of AOID.
Several asymptomatic >5.0-cm AAAs and significant iliac
aneurysms are diagnosed each month at our institute in patients who
are imaged for suspected occlusive disease.
Our routine CTA for AIOD includes cephalocaudad coverage from
the supra-celiac aorta to the proximal thigh (approximately 30 to
40 cm). Native common femoral artery (CFA) disease is not uncommon,
and frequently patients will present with "stick site injuries"
from multiple prior procedures. Avoiding a "diagnostic stick" with
CTA versus diagnostic DSA has significant clinical implications. We
have found CTA to be particularly useful in avoiding "sticking into
CFA disease" or "stick site injuries" (Figure 3). It is always
recommended to scan both legs, since most endovascular procedures
are performed via a CFA approach.
Abdominal aortic aneurysm
Since the introduction of aortic stent grafts and endovascular
aneurysm reconstruction (EVAR), CTA has rapidly become the gold
standard for abdominal aortic pathology diagnosis, treatment
planning, and postoperative surveillance. CTA offers several
potential advantages over traditional imaging, including: 1)
superiority in identifying mural thrombus and in evaluating
periaortic tissues for rupture, endoleak, and
inﬂammatory AAA identification; 2) more precise
determinations of size, length, angulation, and transverse
dimensions of the AAA superior neck; 3) more accurate
characterization of postprocedural juxtarenal AAA endograft
deformation, kinking, or migration with identification of branch
vessels; 4) 3D reconstruction that allows improved assessment of
iliac tortuosity and detection of endoleaks; and 5) post-EVAR AAA
volume determinations that may allow earlier detection of device
failure, rupture, or endoleak.
The femoral and infrapopliteal vessels are among the most
diseased and calcified vessels in the body and are thus a challenge
for vascular imaging. There are no published data that compare DSA
or DU with 64-channel CTA in infrainguinal vessels, and few data
that evaluate 4- to 16-chan-nel CTA.
Several promising image enhancement-processing techniques are
available, especially for infrapopliteal vessels. Curved planar
reformation (CPR) and semitransparent volume rendering (STVR) with
automated measurements are new 3D imaging modalities that improve
the accuracy of CTA in highly calcified vessels. The editing of
boney structures (osseous segmentation) is now available at the
workstation with the use of automatic region-growing imaging
techniques. Segmentation of the tibia, fibula, and tarsal osseous
structures can have significant clinical implications in achieving
limb salvage. Maximum-intensity projection imaging is a 3D
workstation application that allows maximal contrast opacification
and vessel interrogation. CTA holds promise in the clinical
evaluation of the emerging problem of SFA stent fracture and ISR
(Figure 4 A).
Rubin et al
reported the identification of 26 additional infrainguinal arterial
segments utilizing CTA that were not identified with DSA because of
the improved arterial opacification distal to an occluded segment.
CTA-facilitated identification of "distal targets" could identify
patients for tibial bypass or endovascular revascularization who
otherwise may be offered only amputation. One of the most common
reasons for an amputation recommendation is "no distal runoff
target" (Figures 4B and C). Underscoring the need for simpler,
accurate, noninvasive diagnostic imaging, we reported a series of
417 CLI patients of whom 67% had a primary amputation as their
initial treatment without undergoing vascular evaluation.
Of these primary amputated patients, only 49% had an ankle-brachial
index (ABI), and only 16% underwent diagnostic angiography.
This becomes important when considering the excellent >93%
6-month limb salvage rates reported by Laird et al
utilizing the excimer laser (Spectranetics Corporation, Colorado
Springs, CO) in the multicentered LACI trial. Similar 12-month
results were reproduced by our group in the "LACI-equivalent"
Clinical therapeutic benefits of PV-CTA
We have experienced the following understated clinical benefits
with PV-CTA. Illustrative cases will be provided.
1. Vascular access (VA) planning.
An underestimated benefit of PV-CTA is the ability to assist in VA
planning, which is much more complex in peripheral vascular
interventions (PVI) than in coronary interventions. The PVD patient
often has limited VA with poor or no femoral pulses, complex
femoral grafts, heavy femoral calcification, significant groin
scarring, and previously deployed stents, which often impinge upon
the CFA (Figure 5). For these reasons, VA complications are high in
PVI, with a reported incidence of 8% to 16%.
We have drastically decreased our incidence of VA complications
since utilizing preprocedural PV-CTA planning. The choice of
alternate VA directed by PV-CTA (ie, brachial and radial artery)
has significantly expanded our use of endovascular interventions,
decreased vascular access complications, and improved outcomes in
patients who otherwise would have required major open surgical
revascularization procedures or suffered VA complications during
2. Clinical diagnostic accuracy.
The combination of a thorough clinical examination and outpatient
PV-CTA has facilitated an accurate preprocedural diagnosis in even
our most complex PVD patients. The diagnosis is often rendered in
the office in minutes, not hours and days. Onsite PV-CTA and
conventional angiographic validation studies have been performed at
our facility in all vascular territories, revealing >95%
sensitivity and specificity and further providing confidence in our
preprocedural diagnosis and PVI planning.
3. Therapeutic treatment planning and case performance.
Likewise, PV-CTA facilitates reliable procedure planning, even
including revascularization options and device planning. Lesion
morphology characterizations now assist in treatment planning and
periprocedural decision making. Calcified lesions are treated
differently from soft lesions (ie, laser versus PTA versus
cryoplasty versus stenting), and thrombus-containing lesions are
treated differently from intimal hyperplastic lesions (ie, laser
versus plaque excision versus DPD use versus mechanical
thrombectomy versus lysis) (Figure 5, D through F). Peripheral
vascular intervention cases are often complex in performance and
decision making and are therefore longer in duration and have a
much higher risk for overall complications than coronary
interventions. The number of periprocedural PVI "surprises" we
encounter today is dramatically diminished when utilizing PV-CTA;
therefore, decreasing our overall therapeutic PVI procedural times,
radiation exposure, and contrast utilization would facilitate
overall improved outcomes.
We have found CTA of infrapopliteal arteries to be particularly
helpful in periprocedural planning in patients with CLI. Utilizing
our CLI protocol and a second lower extremity scan, we regularly
identify patent distal infrapopliteal and pedal vessels-"distal
targets"-that have not been previously imaged by angiography. We
advocate at least our CLI-CTA on all patients before amputation.
The identification of these "CTA-identified" but "not
angiography-identified" vessels have significant therapeutic
implications for the CLI patient, facilitating appropriate PVI or
surgical bypass planning strategies (Figure 4, B through D).
4. Bypass graft and stent surveillance.
Infrainguinal bypass grafts and PVIs have a 20% to 30% secondary
intervention rate to achieve an acceptable 1- to 2-year patency,
which underscores the need for noninvasive postprocedural
Angiography in patients after bypass grafting can be complex and is
associated with increased VA complications. We avoid "sticking" a
previous bypass graft for PVI unless no other access is available,
and we use CTA in all patients with bypass grafts to decrease
complications. Willmann et al
reported 98% sensitivity and specificity in comparing DSA versus
4-channel CTA in 85 bypass grafts. In our experience, CTA has
allowed more accurate diagnosis and planning for graft
reintervention than has DU and has decreased complications by
facilitating vascular access planning during PVI. Unlike coronary
stents, which are small and not well imaged on CTA, peripheral
stents are much larger, and current software technology allows CTA
to be an excellent tool for stent interrogation for stent fracture,
ISR, and edge dissections (Figure 6).
5. Decreased overall complications.
Peripheral vascular CTA has almost totally eliminated the need for
and risk of diagnostic carotid angiography with its small but
definite risk of stroke. Contrast-induced nephropathy (CIN) has
been reported in 14% of PCI patients, with high mortalities and
The incidence and impact of CIN in PVI is unknown and is very
likely underestimated. The PVD patient is generally 10 to 15 years
older than the PCI patient, and, invariably, PVD patients require
multiple procedures and secondary reinterventions.
The risk of CIN is highly associated with intra-arterial
contrast exposure but less associated with intravenous (IV)
contrast exposure as used during PV-CTA. With proper patient
selection and when outpatient oral and IV hydration protocols are
used, CT-induced CIN should be exceedingly rare. We have developed
PV-CTA protocols to decrease IV contrast volume exposure to 70 mL
while retaining imaging quali-
Consequently, our periprocedural PVI intra-arterial contrast volume
and CIN incidence has dramatically decreased when combining a
preprocedural CTA-contrast planning strategy with clinically
validated periprocedural IV hydration protocols during PVI.
6. Incidental vascular and nonvascular disease.
CTA imaging acquisition also retains traditional CT nonvascular
tissue capabilities. Occult neoplasms, severe degenerative
arthropathies, spinal stenosis, and cholelithiasis are examples of
additional clinical information with therapeutic implications that
are frequently encountered during PV-CTA. Severe RAS, AAAS, and
iliac, visceral, and popliteal artery aneurysms are also frequently
encountered during abdominal CTA with runoff for the assessment of
lower extremity occlusive disease. Likewise, vascular occlusive
disease is often encountered in patients being investigated for
aneurysmal disease. The identification and treatment of unknown RAS
during the treatment of elderly patients with CLI is commonplace
and facilitates the overall therapeutic care of this high-risk
patient population who often require bilateral procedures with
frequent reinterventions and, thus, receive significant contrast
Peripheral vascular CTA is an emerging tool in not only the
diagnostic but also the overall therapeutic treatment of PVD.
Further experience will expose the many understated clinical
benefits of this technology in the comprehensive management of PVD.
Peripheral vascular CTA has become an equally important tool in our
PVD "therapeutic tool box" as wires, balloons, lasers, and
The authors wish to thank Kelly Tilbe, NCMA, NCPT, for her
assistance with technical manuscript preparation.
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