FEBRUARY 2014
ISSUE 59
Ultra-low Contrast Dose CTA for TAVR Planning with a Total Dose of 20cc
Contrast in a Patient with Renal Insufficiency
Andy Chan, MD, Jonathan Passeri, MD, Ignacio Inglessis, MD, Maureen Daher, RN, Sanjeev Francis, MD,
Brian Ghoshhajra, MD, MBA
Clinical History
An 82-year-old male presented with two weeks of dyspnea
at rest and exertion, and orthopnea and lower extremity
edema. Physical examination revealed a grade 3 out of 6
systolic ejection murmur, crackles at both lung bases and
distended jugular venous pressure. His presentation was
consistent with acute diastolic heart failure in the setting of
severe aortic stenosis (AS). He was overweight and weighed
189 pounds, with a body-mass index of 27.8 kg/m2.
Transthoracic echocardiography demonstrated a peak
trans-aortic valve gradient of 63 mm Hg and a calculated
aortic valve area of 0.5 square cm by the continuity equation,
consistent with critical AS. He was referred to our center
for consideration of transcatheter aortic valve replacement
(TAVR) after he was deemed at high surgical risk given
multiple comorbidities including acute on chronic renal
insufficiency, with a 30-day mortality of at least 14% based
on the Society of Thoracic Surgeons (STS) score.
Figure 1
Figure 2
Findings
Ultra-low dose protocol high-pitch dual-source computed
tomography angiography was performed with a total dose
of 20 mL contrast to evaluate the aortoiliac vessels for
access planning. This confirmed suitable vascular sizes
and angulation for the delivery sheath system, with a
minimal luminal diameter of 8mm on left side and 8mm on
the right. The aortic annulus and proximal aortic root were
assessed concurrently via transthoracic echocardiography
(not shown) as well as CTA, to determine the annular size
for TAVR device sizing, and to ensure adequate coronary
ostial height. Preoperative invasive coronary angiography
was also performed to exclude the presence of significant
epicardial coronary stenosis.
Discussion
TAVR has revolutionized the care of the non-operable patient
with critical aortic stenosis by allowing a durable minimally
invasive repair (1). The procedure is preferably performed via
a transfemoral approach, which is contingent upon suitable
aortic root and annular dimensions, and several other
Figure 3
parameters. Because the delivery sheath system
is large, the aortoiliac vessels must be screened
to ensure adequate vascular diameters between
at least one common femoral artery and the entire
route to the aortic annulus. CTA has evolved into
a valuable tool for obtaining these measurements
prior to the TAVR procedure (2). In patients with
renal insufficiency, CTA can be performed with ultra
low contrast dose technique via contrast dilution
and rapid scanning, if equipment and operator
experience allows (3). In this case, minimizing the
contrast dose was essential given the concomitant
renal insufficiency and the planned intervention
necessitating further contrast administration.
Figure 1: The heavily calcified, elliptical aortic annulus is visualized with the use of a 3D workstation which allows
accurate biplanar, area, and circumference measurement of the annulus size (2). This anatomic assessment
confirmed the measurements provided by echocardiography, which is the first-line tool for aortic stenosis
imaging. Echocardiography offers repeatable, physiologic assessments, and transesophageal echocardiography
is mandatory for intraoperative TAVR procedural guidance.
Figure 2: 3D volume rendered images allow rapid depiction of characteristics of the aortoiliac vessels that may render
the TAVR procedure challenging (such as tortuosity or kinking of vessels, severe or circumferential vascular
calcifications). This patient’s aortoiliac morphology was amenable to transfemoral TAVR access.
Figure 3: Adequate opacification of the aortoiliac vessels was achieved even with an ultra-low dose of contrast, thus
allowing centerline extraction by the 3D workstation for accurate measurements of short axis diameters.
REFERENCES
1. Leon, M. B., Smith, C. R., Mack, M., Miller, D. C., Moses, J. W., Svensson, L. G., et al. (2010). Transcatheter aortic-valve
implantation for aortic stenosis in patients who cannot undergo surgery. The New England Journal of Medicine, 363(17),
1597–1607. doi:10.1056/NEJMoa1008232.
2. Achenbach S, Delgado V, Hausleiter J, Schoenhagen P, Min JK, Leipsic JA. SCCT expert consensus document on
computed tomography imaging before transcatheter aortic valve implantation (TAVI)/transcatheter aortic valve
replacement (TAVR). J Cardiovasc Comput Tomogr. 2012 Nov-Dec;6(6):366-80. doi: 10.1016/j.jcct.2012.11.002. Epub
2012 Nov 14. PubMed PMID: 23217460.
3. Azzalini, L., Abbara, S., & Ghoshhajra, B. B. (2014). Ultra-Low Contrast Computed Tomographic Angiography (CTA) With
20-mL Total Dose for Transcatheter Aortic Valve Implantation (TAVI) Planning. Journal of Computer Assisted Tomography,
38(1), 105–109. doi:10.1097/RCT.0b013e3182a14358.
Editors:
Brian Ghoshhajra, MD, MGH Department of Radiology
Sanjeev A. Francis, MD, MGH Division of Cardiology