Angiogram

Preparation

• Review imaging/previous angiograms
• Hb and eGFR
• Consent
• Orientation of room
• Level of sedation
  • GA required for unco-operative patient, unable to lie flat, difficult to access artery

Therapeutic technique

• Balloon angioplasty
  • Mechanism: blunt dehiscence leading to fracture and separation of the intima from the media, with stretching of media and adventitia
  • Types of systems:
    • Over-the-wire
      • Wire passes through the entire catheter
      • Good support, high pushabiity
      • Allows for guidewire exchange when a lesion is difficult to cross
    • Single-operator exchange aka monorail or rapid exchange
      • Wire enters from the distal tip of the catheter and exits from a side-hole 20-25cm proximal to the balloon
      • Used in coronary interventions and for below-knee lesions
      • Easier to use because a single person can deliver and exchange it close to the insertion point
  • Balloon characteristics
    • Compliance - degree of expansile ability - function of pressure and diameter
      • Compliant balloons are superior in trackability and suitable for lesions in a curved part of the vessel. Not suitable for severely calcific lesions as it may damage the adjacent normal vessel.
      • Non-compliant balloons aka high-pressure or low compliance balloons. Allow for high-pressure expansion and have a higher RBP than compliant balloons.
      • Nominal pressure - the pressure at which the balloon expands to its determined diameter and length, generally 3-10 atmospheres
      • Rated burst pressure is the pressure at which <1% of tested balloons will burst, but beyond which the probability of rupture increases, typically 6-16 atmospheres
      • Mean burst pressure - pressure at which 50% of balloons will rupture - usually 10-27 atmospheres
    • Profile and balloon ability
      • Profile - French size - smaller profile is better than a larger in terms of deliverability to the lesion and the ability to cross severely stenotic lesions
      • Trackability - ability to follow guidewire without loss of wire position, which is important when following a tortuous vessel
      • Pushability - ability to transmit force along the length of the balloon catheter to the target lesions. Better with larger balloons and OTW systems.
      • Crossability - ability to cross stenotic lesions - depends on tip features and low-friction systems
    • Types of balloons
      • Cutting balloons - 3 or 4 artherotomes mounted longitudinally along the surface of a standard PTA balloon
      • Cryoplasty - uses cooling and pressure to dilate the plaque and the vessel wall
      • Focal pressure balloon
      • Drug coated balloon
        • Adopts the technology from DES
        • Coated with anti-proliferative drugs such as paclitaxel
        • Favourable outcomes in terms of lumen size and long-term patency compared to standard balloons, but really long-term data are lacking
        • Perform pre-dilation with a standard balloon before using DCB
  • Technique:
    • Mostly done with 6Fr access
    • Systemic heparinisation - 50-100U/kg prior
    • Pass the wire through the lesion via the true lumen
      • Use a 0.035 hydrophilic wire for most lesions
      • 0.018 for highly stenotic lesions
    • Balloon selection
      • Balloons are available up to 30cm in length
      • Mostly start off with an undersized balloon then work up to target size
    • Balloon placement - re-DSA the lesion just prior to balloon placement
    • Difficulty during balloon passage
      • Exchange the wire for a stiffer wire
      • Advance the sheath or guide catheter closer to the lesion
      • Switch to a lower-profile balloon or one with greater pushability
    • Balloon inflation
      • Ensure it is flushed prior to insertion
      • Replace the existing air inside the balloon with 25-50% contrast
      • Most severe stenotic lesion should be in the middle of the balloon
      • Monitor balloon shape in real time with fluoroscopy
      • Typically keep inflated for 30-60 seconds
      • Risk of rupture if patient complains of severe pain during expansion - maintain position across the lesion in case stenting is required
    • Completion angiography
  • Complications
    • Dissection

Grade A is a small radiolucent area within the lumen of the

vessel disappearing with the passage of the contrast material.

Grade B is a filling defect parallel to the lumen of the vessel

disappearing with the passage of contrast material. Grade C is

a dissection protruding inside the lumen of the vessel persisting

after passage of contrast material. Grade D is a spiral-shaped

filling defect with delayed run-off of the contrast material in

the distal vessel. Grade E is a persistent luminal filling defect

with delayed antegrade flow. Grade F is a filling defect accompanied

by total occlusion. Stenting is typically required with

Grade C to F dissections.

• Stents
  • Mechanism: useful in reducing the incidence of restenosis or address balloon PTA failure due to elastic recoil or dissection
  • Mostly based on nitinol - an alloy of nickel and titanium
  • Types:
    • Balloon-expanding (BES)
      • Balloon is inflated to deploy the stent
      • Suitable only for vessels that are not prone to external compression (become irreversibly deformed) - avoid in ICA or SFA
      • Can be placed more precisely than SES
      • Tend to be more radio-opaque than SES
      • Good for renal, mesenteric, iliac, subclavian, or brachiocephalic arteries
    • Self-expanding
      • Mostly nitinol
      • More flexible - greater trackability, and resistant to fracture
      • Less likely to cause interference on MRI
      • Most stents are stored in the delivery sheath, and deployed from the distal end to the proximal end by unsheathing, and generally can't be repositioned after that
      • Generally OTW systems
      • Classified as open-cell (cylindrical structure of stacked serrated metal) or closed-cell (all edges and vertices of the stent cells are shared with an adjacent cell - preferable for lesions at risk of embolisation because the mesh is very fine) design
    • Bare metal
      • Mostly stainless steel/nitinol/cobalt chrome or other alloys
    • Covered
      • Can be PTFE, polyurethane, or silicon
    • Stent grafts
      • Balloon-expanding or self-expanding
      • Stent struts with something like PTFE shell
      • Can be used for perforations or for various occlusive lesions
    • Drug-eluting stents
  • Complications:
    • In-stent restenosis
    • Stent fractures

Atherectomy devices

• Ideally achieve patency without the need for stenting - especially useful for areas where stenting should be avoided (CFA, POPA behind knee)
• Types:
  • Direction
    • Carbide cutting blade with a variable height and a plunger used to pack the atheroma into the nose cone
    • Cutting blade rotates at up to 8000rpm
    • Designed for treating severe calcification
  • Rotational
    • Insert a small drill into the artery to fracture a plaque and create a smooth lumen
  • Laser atherectomy

Thromboembolectomy

• Aspiration
  • Simplest way to remove thrombus - aspirate it with a large catheter or sheath (Export, PriorityOne, Pronto)
  • Risk of distal embolisation remains - thrombolytic drugs often used in combination
  • Work better in smaller vessels (<6mm)
• Rheolytic
  • Jet of saline ejected from the tip of the catheter and used to dissolve it
• Rotational
  • Remove the thrombus by rotating the tip of the catheter

Intra-luminal devices to cross chronic total occlusions

• Can be difficult or impossible to cross the plaque or segment of poorly organised thrombus, which often has a fibrotic or calcified cap at both ends, due to an inability to generate enough axial force through the guidewire
• Devices such as Crosser, TruePath, Frontrunner XP can be used to assist

Re-entry devices

• Outback LTD Re-Entry System - penetrates the intimal flap, redirecting the guidewire from the subintimal plane to the true lumen
• Other devices for similar effects

Embolisation devices

• Used to treat bleeding, small aneurysms, fistulas or endoleaks
• Mechanical
  • Coils
  • Vascular plugs
• Particulates
  • Polyvinyl alcohol
  • Gelatin microspheres
• Liquid agents
  • Absolute ethanol
  • N-butyl cyanoacrylate

Vascular closure devices

• So far demonstrated to be non-inferior to manual compression
• AngioSeal - sandwiches the arteriotomy with a bioabsorbable anchor connected with sutures and a collagen sponge that dissolve within 60-90 days. Compatimble with 5-8Fr sheaths.
• Exoseal - bioabsorbable polyglycolic acid to achieve haemostasis. Compatible with 5-7Fr.
• Mynx - polyethylene glycol sealant deployed outside the artery, while a small balloon inflates the arteriotomy site to create temporary haemostasis within the artery. 5-7Fr.
• ProGlide - suture-based - mimics open surgical closure. 5-21Fr.
• Prostar XL - for large bore device closures.