Biomechanics Cardiovascular - Bruce


Flashcard Set Preview

Side ASide B
What is atherosclerosis What are consequences
Artery wall thickens - fatty tissue build up Reduced blood flow and nutrients Amputation, stroke, heart attack, kidney failure
Cellular Mechanisms of Plaque
1. Excess LDL in arterial wall 2. LDL stimulate endothelial cells - adheasion molecules - latch to monocytes = inflammation 3. monocytes - macrophages = inflammation mediators 4. Inflammatory...
Arterial Imaging Methods
1. Angiogram - x-ray based (0.25mm) 2. Intravascular Ultrasound IVUS - planning and post op analysis 3. Optical Coherence Tomography (OCT) near infrared light (+/- 0.015mm)
Atherosclerosis Treatment Options
Angioplasty, atherectomy, force focused angioplasty, cryoplasty, laser, radiation, local drug delivery, stents, bypass surgery, blunt dissection
PTCA - percutaneous transluminal coronary angioplasty POBA - plain old balloon angioplasty
medical devie that is inserted into clogged artery and inflated to high pressures to clear the blockage and allow blood to flow
Angioplasty lumen enlargement happens from what combination?
1. plaque reduction (compression/embolisation) 2. axial plaque redistribution 3. vessel expansion
Describe two types of medical ballons
1. high pressure balloons - molded to inflated geometry, non/low compliant materials that retain size/shape even in high pressure 2. low pressure ballon - molded to tubular shape, expanded...
Balloon Definitions
Diameter: diameter at specific pressure Length: working length/length of body section burst pressure: avg pressure to rupture ballon rated pressure: statisically guaranteed pressure...
Balloon materials
PET: polyethylene terephthalate - high tensile strength, low-medium compliance, high stiffness, low profile, max rated pressure 254psi, 20 atm, radiation Etd Nylon - not as strong but...
Desired Ballon Qualities
1. smallest possible wall thickness 2. burst pressure > 15 bar 3. defined pressure & diameter characteristics
How balloons are made?
extrusion of material into a tube shape - blow molding 1. heating jaws to melt plastic 2. tubing kept in balloon form for a time - at constant pressure 3. after warm up - high pressure...
Balloon mechanics
stress circumferential = pd/2t stress axial = pd/t coronary d = 2.5 mm valvuplasty d = 26 mm would expect much greater stresses in valvuplasty
Design Requirments for Balloon Catheter
1. low profile 2. flexible 3. pushable 4. high burst pressure 5. tensile strength 6. kink resistance 7. pressure transfer properties 8. fast inflation/deflation times
Two main catheter designs
1. Over-the-wire (OTW) catheter (co-axial/dual-lumen design) peripheral procedures 2. Rapid exchance - long SS hypotube & short flexible distal shaft - exit port located along distal...
Testing Requirements
1. Cyclic testing 10-40 cylcles of RPB (rated balloon pressure?) 2. Burst pressure - must tear longitudinally along balloon 3. inflation/deflation (30s max for peripheral catheters) 4....
Drug Eluting Balloons (DEBs) what are they coated with? what is concept?
coated with proprietary solution or dipped in paclitaxol assumption rapid release of drug into tissue is more effective than gradual release of drug (DES)
Application of DEB?
Coronary arteries - bifurcations, small vessels <2.5mmd, left main disease Peripheral arteries - arterias arms, legs, abdomen - pain/gangrene
Angioplasty vs Surgery in Lower Extremity Lessions
Angioplast - short occlusions < 2 cm tibal, < 5cm iliac, < 10 cm superficial femoral artery Surgery favored - long occlusions failure post angioplasty
What is RAS
- renal artery stenosis - arteries that feed kidneys! - occurs in 5% of pop - can lead to renal failure if untreated - angioplasty/stenting effective in halting/retarding
What is CAS what can happen? treatments? complications?
Caratoid arterial stensis - can develop stoeks - angioplasty as alternative to invasive carotid endarterectomy? - not suitable of reg SS stent - intracerebral embolism (plaque fragments) -...
Protection devices during carotid arterial stenting
1. distal occlusion ballon - obstructs bloodflow as well as distal emboli, require aspiration of blood and emboli from artery prior to deflation 2. proximal occlusion - 3. filtration...
What is atherectomy?
removal of atheroslerotic tissue by cutting/shaving tissue off inside of the artery
Problems with Balloon Angioplasty
1. restenosis ~30% cases - elastic recoil, negative vascular remodling maintain acute luminal gain
Stent manufacturing steps
1. alloy tubes 2. laser cut stent pattern 3. grist blast - remove laser burrs 4. electropolish to remove surface debris 5. inspect and clean 6. crimp on to catheter 7. package and sterilize
Stent requirements
1. high expandibility (ratio collapsed to expanded diameter) 2. wall thickness as small as possilbe to offer low profile before and after deployment + increase flexibility 3. postimplant...
Stent Materials
1. plastically deformed alloys (316L/304 SS or CoCr alloy) 2. self expanding nitinol stents 3. biodegradable polymers
(superelastic 20x more that SS, spring loaded stent - biocompatible + corrosion resistant + reshape after externally applied force, physiological compatibility + dynamic interface as...
Problems after stenting
1. cannot abolish restenosis - endothelial injury can create neointimal proliferation 2. ISR can occure up to 40% of the time

Upgrade and get a lot more done!