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December 23, 2005
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Bart E. Muhs, MD, Arno Teutelink, MD, Matthias Prokop, MD, PhD, Koen L. Vincken, PhD, Frans L. Moll, MD, PhD, Hence J.M. Verhagen, MD, PhD.
Utrecht University Medical Center, Utrecht, The Netherlands.
OBJECTIVES: Traditional sizing and choice of endograft has been primarily based on static aortic CTA images. The consequences of these choices on renal artery movement has not been examined. Different endograft configurations may affect physiologic processes remote from the aorta. It is unclear what comprises natural renal artery motion per cardiac cycle, and how EVAR may distort this normal process. We studied these phenomena dynamically using ECG-gated 40-slice CTA.
METHODS: Twenty-four renal arteries were studied, 12 pre- and 12 post-EVAR using the Talent® device with suprarenal fixation. The pre-EVAR scan was used as the control for the identical patient’s post-EVAR scan. Data was acquired using a novel ECG-gated dynamic 40-slice CT scanner during a single breath hold with a standard dose of 17.5-21 mGy, 1.25 mm collimation and a pitch of 0.2-0.3. Eight gated data sets, covering the cardiac cycle were reconstructed, perpendicular to the center flow lumen of each renal artery at 1.2 cm and 2.4 cm from aortic attachment. Center of mass (COM) was plotted on a cartesian coordinate system and maximal COM displacement determined per cardiac cycle for pre- and post-EVAR renal arteries. The direction of the movement was also recorded. Both normal and post-EVAR renal movement was determined and compared using a students T-test with p≤0.05 considered significant.
RESULTS: Normal renal artery motion is impressive with up to 3 mm movement both near and distant from the aorta (range 1.1 mm - 3.0 mm, mean 2.0 mm, SD 0.57 mm). EVAR with suprarenal fixation significantly inhibits proximal physiologic renal motion resulting a 28% decrease in maximal movement (range 0.3 mm - 1.9 mm, mean 1.4 mm, SD 0.7 mm)(p≤0.05). Distal renal artery motion is unaffected by EVAR with motion similar to the pre-EVAR state. Both pre- and post-EVAR renal arteries typically exhibit a “figure of eight” direction of movement.
CONCLUSIONS: ECG-gated dynamic CTA with standard radiation dose is feasible on a 40-slice scanner and provides insight into (patho) physiology of renal motion before and after EVAR. Suprarenal fixation appears to change renal artery conformation by limiting proximal cardiac cycle renal artery motion while leaving distal motion unaffected. Any ill consequences of these complex dynamic renal artery changes are presently unknown, but with fenestrated and branched procedures emerging, issues of stent durability, fixation systems, and long-term renal artery effects should be considered.
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EVAR Alters Renal Artery Conformation: Dynamic Implications for Renal Sidebranched Endografts
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Bart E. Muhs, MD, Arno Teutelink, MD, Matthias Prokop, MD, PhD, Koen L. Vincken, PhD, Frans L. Moll, MD, PhD, Hence J.M. Verhagen, MD, PhD.
Utrecht University Medical Center, Utrecht, The Netherlands.
OBJECTIVES: Traditional sizing and choice of endograft has been primarily based on static aortic CTA images. The consequences of these choices on renal artery movement has not been examined. Different endograft configurations may affect physiologic processes remote from the aorta. It is unclear what comprises natural renal artery motion per cardiac cycle, and how EVAR may distort this normal process. We studied these phenomena dynamically using ECG-gated 40-slice CTA.
METHODS: Twenty-four renal arteries were studied, 12 pre- and 12 post-EVAR using the Talent® device with suprarenal fixation. The pre-EVAR scan was used as the control for the identical patient’s post-EVAR scan. Data was acquired using a novel ECG-gated dynamic 40-slice CT scanner during a single breath hold with a standard dose of 17.5-21 mGy, 1.25 mm collimation and a pitch of 0.2-0.3. Eight gated data sets, covering the cardiac cycle were reconstructed, perpendicular to the center flow lumen of each renal artery at 1.2 cm and 2.4 cm from aortic attachment. Center of mass (COM) was plotted on a cartesian coordinate system and maximal COM displacement determined per cardiac cycle for pre- and post-EVAR renal arteries. The direction of the movement was also recorded. Both normal and post-EVAR renal movement was determined and compared using a students T-test with p≤0.05 considered significant.
RESULTS: Normal renal artery motion is impressive with up to 3 mm movement both near and distant from the aorta (range 1.1 mm - 3.0 mm, mean 2.0 mm, SD 0.57 mm). EVAR with suprarenal fixation significantly inhibits proximal physiologic renal motion resulting a 28% decrease in maximal movement (range 0.3 mm - 1.9 mm, mean 1.4 mm, SD 0.7 mm)(p≤0.05). Distal renal artery motion is unaffected by EVAR with motion similar to the pre-EVAR state. Both pre- and post-EVAR renal arteries typically exhibit a “figure of eight” direction of movement.
CONCLUSIONS: ECG-gated dynamic CTA with standard radiation dose is feasible on a 40-slice scanner and provides insight into (patho) physiology of renal motion before and after EVAR. Suprarenal fixation appears to change renal artery conformation by limiting proximal cardiac cycle renal artery motion while leaving distal motion unaffected. Any ill consequences of these complex dynamic renal artery changes are presently unknown, but with fenestrated and branched procedures emerging, issues of stent durability, fixation systems, and long-term renal artery effects should be considered.
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