pva: don't forget about me
TRANSCRIPT
Polyvinyl Alcohol:
Don’t Forget About Me!
Keigo Osuga, MD, PhD
Department of Diagnostic and Interventional Radiology,
Osaka University Graduate School of Medicine
Keigo Osuga, M.D., Ph.D.
• No relevant financial relationship reported
Drying towel
PVA Products in Our Life
Cleaning sponges
Textile fiber
Synthetic polymer
Biocompatible
Chemical resistant
Elastic and tensile
Water-soluble
Glue
Chemical Structure
Acetate group (Hydrophobic)
Hydroxyl group (Hydrophilic)
• n+m = Degree of polymelization
• n/n+m = Degree of saponification
PVA is obtained by first polymerizing vinyl acetate, and
second by saponification of polyvinyl acetate.
The extent of hydroxylation determines the physical,
chemical and mechanical properties of PVA.
Formalized PVA
Most PVA embolic particles undergo formalization to bridge
between hydroxyl groups to give insolubility, and can be used
as a permanent embolic material.
Contour® PVA, Contour SE™, Cook Medical® PVA
PVA for Medical Applications
Non-implant devices
Surgical sponges
Soft contact lenses
Eye drops
Implantable devices
Artificial cartilage
Patch grafts in cardiac surgery
Skin grafts in burns
Embolic agents
Early History of PVA as Embolic
Compressed PVA plug as a closure of PDAPorstmann W, et al. Radiol Clin North Am 1971
Early History of PVA as Embolic
Compressed PVA plug as a closure of PDAPorstmann W, et al. Radiol Clin North Am 1971
Compressed PVA sponge for postsurgical pelvic
bleeding, vascular tumors and spinal AVMTadavarthy SM, et al. Radiology 1974
Tadavarthy SM, et al. AJR 1975
PVA plug in pre-loaded polyethylene tubes for gas sterilization
Early History of PVA as Embolic
Compressed PVA plug as a closure of PDAPorstmann W, et al. Radiol Clin North Am 1971
Compressed PVA sponge for postsurgical pelvic
bleeding, vascular tumors and spinal AVMTadavarthy SM, et al. Radiology 1974
Tadavarthy SM, et al. AJR 1975
PVA shavings for hypervascular tumors and AVMsHerrera M, et al. Radiology 1982
Rotating rasp to prepare shavings from PVA block
Vibrating sieve for separating shavings into different sizes
Non-spherical PVA Products
Ready-to-use dry particles
Contained in a sterilized vial
Color-coded vials according to size (50-1,200 μm)
PVA
Bearing nsPVA
Contour
A PVA Particle in Microscope
Derdeyn,CP et al. AJNR 1995;16:1335–43
Dry In contrast
Irregular shape Size increases in contrast by 20-40% Rarely, small fragments <50 μm Long & short axis diameter in best-fitting ellipse
Inhomogeneous in size distribution
Calibration improved in the newer product
PVA: Size Distribution
Newer 71%
Older 51%Newer
Older
Newer 72%
Older 38%
www.merit.com
355-500 μm 500-710 μm
PVA: Microcatheter Compatibility
<500 μm
<700 μm
0.027 inch ID
0.021 inch ID
Microcatheter passage <700 μm
PVA: Preparation & Injection
Preparation
Suspension in contrast media for radio-opacity
Albumin, dextran, or ethanol helps decreasing clumping
Injection techniques:
Flow-directed technique
Fluoroscopic guidance
Frequent catheter flushing to avoid its occlusion
Endpoint:
- Slowing of the antegrade flow
- Occlusion faster than expected due to clumping
Irregular shaped particles aggregate and adhere to the
vessel wall ---> blood flow stagnation
Vessel occlusion completed with thrombus among particles.
Recanalization may occur due to resorption of the thrombi
and/or angiogenesis inside the organized thrombus
PVA foam® 180-300 μm
Rabbit kidney 1w (EVx100)
PVA: Mechanism of Action
Preoperative embolization for meningioma
Hemoptysis
TACE/TAE for liver tumors
UFE or post-partum hemorrhage
GI bleeding
Prostate embolization for BPH
etc.
Today, overtaken by microspheres…
PVA: Clinical Applications
Spies JB, et al. JVIR 2004; 15:793-800
PVA vs. Microspheres
Advantages:
Less particle volume
Less contrast volume
Less procedure time (radiation exposure)
Less cost
Disadvantages:
Harder to inject through a microcatheter
Proximal aggregation -- unpredictable occlusion level
PVA vs. Microsphere:
Microcatheter Passage
PVA 355-500 μm Microsphere 400 μm
Aggregation in the hub
PVA(S) 45-150 μm (n=15)
PVA(L) 150-250 μm (n=15)
TGMs 150-300 μm (n=30)
Efficacy of trisacryl gelatin microspheres versus polyvinyl
alcohol particles in the preoperative embolization of
meningiomas.Bendszus M, et al. AJNR2000;21:255-261
PVA vs. Microspheres: Meningioma
• Interval to surgery 6-7 days
TGMs significantly reduced blood loss(mL) at surgery
- PVA mean 886 or 917 vs. TGMS 621 (p<0.05)
TGMs occluded more distal vessels, and induced more
extensive tumor necrosis.
TGMs 500-900 @ “limited” endpoint (n=54)
PVA 355-710 @ “near-stasis” endpoint (n=46)
PVA smaller volume (3.0mL vs. 9.4mL, p=0.0001)
PVA more catheter occlusion (28% vs. 4%, p=0.001)
No difference in VAS pain score (3.1 vs. 3.0, p=0.87)
No difference in fibroid infarction (76% vs. 77%, p=0.89),
symptom relief, patient satisfaction, complications
Spies JB, et al. JVIR 2004; 15:793-800
Polyvinyl alcohol particles and tris-acryl gelatin microspheres
for uterine artery embolization for leiomyomas: Results of
randomized comparative study.Spies JB, et al. JVIR2004; 15:793-800
PVA is as safe and effective as
microspheres in clinical and imaging
outcomes.
PVA vs. Microspheres: UAE
PVA: Conclusion
Safety and effects proven in long-history >40 years
Drawbacks from irregular size/shape
Use diminished by prevalence of microspheres with
deeper penetration
In most regular practice, PVA still contributes to
achieve faster procedure with lower cost.
(Like gelatin sponge in Japan…)
Thank you for your kind attention!
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