Editing Endovascular access

== Choice of site ==

* '''Consider:'''
** Appropriateness for procedure - size, location
** Ability to obtain haemostasis afterwards - seal with manual compression/closure device
*** Difficult factors: significant calcification; small diameter vessels
** Ability to safely convert to open if there is a complication
** Ensuring that cannulation of that site will have minimal adverse effects on the tissue being supplied by the access vessel
*** Rarely an issue for diagnostic procedures
* Options:
** CFA most common, followed by brachial and radial artery (when a smaller-calibre device can be used and femoral access is disadvantageous)
** Popliteal and tibial can be used for lower extremity interventions, but rarely first choice, and not considered for diagnostic-only procedures
** Others: carotid, subclavian, axillary, iliac

== Vessels: ==

* Axillary
** Easier to use brachial, since it's easier to access and there's minimal difference in calibre
** Technique
*** Upper arm in abduction and flexion
*** Locate intramuscular groove between triceps and coracobrachialis
*** Haemostasis by compression against the humerus (bleeding can create a compartment syndrome for the median nerve)
* Iliac artery
** Open surgical approach is easiest
** Percutaneous techniques are contraindicated due to difficulty in establishing haemostasis
* CFA
** Can be compressed against femoral head
** Can be converted to an open approach easily with a groin cut-down
** Can accommodate devices as large as 26F and suture-based closure devices
** Anatomy:
*** Continuation of EIA as it crosses under the inguinal ligament, giving off circumflex iliac and superficial epigastric branches
*** 5-8cm long
*** Bifurcates into SFA and PFA
*** Medial to femoral nerve, lateral to CFV
*** Overlies medial aspect of femoral head
***
** Antegrade access:
*** Harder than retrograde, as you need to enter CFA above the bifurcation, which means a steep downward angle
*** In obese patients, might need someone to retract the pannus
*** Entering too close to the bifurcation means it will be difficult to selectively cannulate the SFA
** Retrograde access:
*** Aim to obtain access over the femoral head, just above the femoral bifurcation but below the inguinal ligament with the needle pointing cranially
*** Punctures cranial to the IL may be difficult to seal
*** Punctures too distally increase risk AVF from PFA or plaque dissection of the proximal SFA
* Brachial artery
** Can be compressed against the humerus - can be challenging though
** 6F sheaths can be used safely in most patients
** Anatomy
*** Palpable just over the olecranon process when the arm is supinated
*** Use USS in combination with micropuncture technique
*** Risk of median nerve compression with a haematoma
** Technique
*** Need to delineate the bifurcation prior to attempting access, so that entry into the largest part of the vessel is achieved
* Popliteal artery
** USS very useful in differentiating from popliteal veins
** Haemostasis can be difficult, as effective compression in the fatty popliteal space is hard
** Anatomy:
*** Continuation of the SFA as it exits Hunter's canal in the distal medial thigh
*** Divides into ATA and TPT
*** Flanked on each side by dupicated popliteal vein
*** Can be accessed medially either above or below the knee, or posteriorly using a prone position
* Tibial arteries/peroneal arteries
** Commonly accessed using micropuncture technique assisted by USS
** Small sheaths and soft wires
** Anterior tibial artery
*** Anatomy
**** Anterior compartment of leg, dorsal surface of the foot (dorsalis pedis)
** Posterior tibial artery
*** Anatomy
**** Palpable near the ankle, and amenable to access here as it is easily compressed
** Peroneal artery
*** Anatomy
**** Deep posterior compartment of the leg
**** Generally travels between tibia and fibula
**** Hard to reach, rarely used
* Radial artery
** Can accommodate sheaths between 4F and 6F
*

== Adjuncts to obtain access ==

* Manual palpation of pulse
** Two fingers - one proximal and one distal, spread out by a few centimetres
** Access needle inserted directly between the two fingers
* Radiographic guidance
** Useful when a pulse is either absent, or not able to be appreciated due to overlying scarring
* USS guidance

== Technique ==

* Needles
** Single-wall: almost universally used for percutaneous access. 18-gauge needle for 0.035-inch guide wire. 21 gauge needle for 0.018-inch guide wire.
** Double-wall: blunt-tipped hollow needle with an inner bevelled stylet. Historically used to puncture both anterior and posterior walls, then inner stylet removed, then needle slowly withdrawn until blood comes back.
* Micropuncture needle technique
** Vessel identified with USS
** 21-gauge needle inserted at 30-45 degrees, so it enters the vessel at site of visualisation
** 0.018-inch floppy tip guidewire inserted into the vessel
** Needle removed from over the wire
** 4F introducer sheath
** Inner canula of sheath removed, along the guidewire
** 0.035-inch wire can be inserted at this point and sheath upsized to 5F or 6F if needed for definitive access
* Standard needle technique (for easily palpable femoral pulses in otherwise uncomplicated anatomy)
** 18-gauge needle and 0.035-inch J-tip moveable core steel guidewire (don't use hydrophilic-coated guidewire for initial entry as the coating can shear off and embolise from the needle)
** Straight to 5F or 6F sheath
** This technique is helpful in situations where tracking the 4F sheath over the less supportive 0.018-inch wire can be hard, like in scarred groins or when accessing a Dacron graft
* Sheaths
** Inside calibre measured by French size, from 4F to 11F
** Have a haemostatic valve at the end
** Braided sheaths can be used when cannulating a vessel through dense tissue or making sharp turns that can lead to kinking of the sheath
** Most commonly 10cm length for diagnostic purposes, but available 5-100cm
** 45cm sheath typically used working on the contralateral iliac system or beyond, and a 90cm sheath used to work on the carotids. Chosen sheath should be no longer than necessary.
**
* Guidewires
** Jagwire (Boston Scientific) commonly used at Austin
*** Nitinol with Endo-Glide coating
*** 5cm hydrophilic tip
*** 0.025 or 0.035-inch diameters
*** 260 or 450cm length
*** Straight or angled tip
*** Good for use in biliary duct cannulation from top or bottom
* Catheters
** Vehicles used to deliver the radiographic contrast agent to the area of interest
** Most catheters 2F-6F
** 2F and 3F are microcatheters for delivery of embolisation coils
** Types of diagnostic catheters:
*** Non-selective - used to inject a high volume of contrast into relatively large blood vessels, typically using power injection. Multiple side holes along the last 15mm to reduce the 'jet effect'.
*** Selective - their shape facilitates engagement in the orifice of a branch vessel, for either direct injection or subsequent guidewire passage. Generally have an end hole only (no side-holes), and therefore can't inject with too much pressure. Divided into single-curved, double-curved and reverse-curved configurations.
**** Single-curved: ideal for cannulating a side branch vessel coming off at less than 45-degree angle from the aorta.
**** Double-curved: angle up to 90 degrees or greater.
**** Reverse-curved: typically have a 180-degree curve, for vessels that come off steeply.
** Interventional catheters:
*** Crossing 
**** Used for crossing occluded/stenotic vessels
*** Guiding catheters - essentially sheaths with tips with different lengths and shapes to permit selective cannulation
**

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* Closure devices
** Simple manual compression
*** Not too tight - lead to thrombosis
*** Hold for 5-20 minutes
*** 6 hours mandated bedrest
** Closure devices
*** Seal the access hole in some way or another
*** Minimise need for compression and bed rest
*** Increase risk of groin infection and leg ischaemia.
*** Angio-Seal - intra-arterial absorbable anchor is placed against an externally placed collagen sponge, and these are sandwiched together. Good for arteries >5mm without significant calcification, and can be used to close sites up 8F. Can get ischaemic complications when deployed incorrectly.
*** Mynx - polyethylene glycol polymer closes the tissue track over the puncture site, which dissolves within 30 days. Haemostasis for up to 6F. Higher risk of ischaemic and bleeding complications.
*** ProGlide - single polypropylene stitch to suture close arteriotomy sites up to 6F. Can be used off-label to close large arteries by putting two of them together. Device failure - manual compression, additional ProGlide use, or open repair.


Consent: bleeding, infection, thromboemboli, failure, additional procedures, contrast allergy or nephropathy, limb loss, anaesthetic, neurovascular


== Complications ==

* Access site
** Risk factors
*** Obesity
*** Diseased access vessels
*** Large sheath size
*** Anticoagulation
** '''Bleeding (1%)'''
*** Initial management:
**** Apply pressure while the patient is stabilised (push against an anatomic structure)
**** Reverse anticoagulation
**** Reassess with imaging (?CTA or USS)
**** Endovascular balloon control as an adjunctive technique while definitive management is obtained
*** Definitive management:
**** Continued bleeding may need open repair
**** Endovascular treatment with peripheral endografting
** '''Haematoma (3%)'''
*** Initial management:
**** Apply pressure while the patient is stabilised (push against an anatomic structure)
**** Reverse anticoagulation
**** Check Hb every 6 hours
**** DUS to exclude pseudoaneurysm
*** Open surgical repair
**** Indications: haemodynamic instability, persistent anaemia despite transfusions, pseudoaneurysm unsuitable for thrombin injection; skin compromised, nerve compression, severe pain
*** Retroperitoneal haematoma:
**** Suspect in hypotension, diaphoresis, groin pain, abdominal pain, bradycardia, back pain
**** CT is best test
**** Indications for intervention - neurologic deficits in the extremity, haemodynamic instability, ongoing blood loss, severe pain
**** Open procedure:
***** Either groin incision or an incision above inguinal ligament
***** Expose arteriotomy and repair
**** Endovascular option would be a covered stent, good in high injuries
** '''Thrombosis (2%)'''
*** Risk factors - significant local atherosclerotic disease, previous groin reconstruction
*** Usually becomes apparent after manual compression is complete
*** Endovascular - mechanical thrombectomy, thrombolysis, atherectomy
*** Surgical - groin exploration with femoral endarterectomy, patch angioplasty, thromboembolectomy
** '''AVF (0.9%)'''
*** Tend to occur with more distal punctures, especially of PFA itself
*** Detected by palpable thrill or continuous bruit
*** Check for distal ischaemia and cardiac dysfunction
*** DUS best test to diagnose
*** Many are asymptomatic and will close spontaneously (38% within 12 months). Need follow-up DUS.
*** Persistent, symptomatic or enlarging AVF should undergo repair
**** Surgical: open cut-down
**** Endovascular - balloon-expandable stent grafts
** '''Pseudoaneurysm (0.6%)'''
*** Pulsatile groin mass, systolic bruit
*** Perform DUS if suspicious
*** If there is significant extension into the retroperitoneum, CT might help to fully define its extent
*** Complications: nerve compression, distal embolisation, skin necrosis
*** Observation alone is reasonable in small PSAs
*** USS-guided compression works 74%-93%. Less effective on anticoagulation, large pseudoaneurysms, patient discomfort.
*** Thrombin injection for pseudoaneurysm
**** Allows fibrin clot to form and thrombose the PSA
**** Indications: persistent, enlarging, symptomatic
**** Needs to be a long pseudo aneurysm with a narrow neck (<0.55cm) to reduce the risk of injecting thrombin into the artery (very difficult to get out if that happens)
**** Anticoagulation use associated with incomplete thrombosis
*** Surgery:
**** Larger PSAs
**** Wide neck
**** Failed alternative treatment
**** Endovascular is a possibility
* Catheter/guidewire related
** Perforation
*** Confirm with extravasation of contrast
*** Usually seals with conservative management
*** Management depends on vessel and clinical status
*** Can use covered stents
*** Angioplasty-induced perforation of infra-inguinal vessels isn't life-threatening but can result in pseudoaneurysm or occlusion
** Dissection (7% after PTA)
*** Balloon inflation causes stretching and disruption of the plaque and overlying intima that results in a tear or dissection. This can be propagated distally and result in flow-limiting obstruction or arterial occlusion.
*** Seen on arteriography - luminal flap with contrast on both sides
*** Usually treated by sustained inflation of low-pressure angioplasty balloon in an attempt to 'tack down' the dissection flap
*** If unsuccessful (>30% or flow-limiting dissection), stent can be used
** Embolisation (1-3%)
*** Any wire, catheter or sheath manipulation (especially atherectomy though) can result in embolisation, in patients with large-volume atheromatous disease
*** Can result in trashing of runoff vessels, or stroke if in aortic arch
*** Prevention better than cure - institute anticoagulation prior and minimise manipulation across the lesion, and can use embolic prevention devices in setting of large-volume plaque burden, significant thrombus burden or single-vessel runoff
*** Management:
**** Endovascular rescue - heparinise, trial with aspiration catheter, or trial with AngioJet if you think it's thrombus, thrombolytics
**** If unsuccessful and there are signs of acute ischaemia, treat with standard open procedures
* Systemic
** HIT
** Contrast nephropathy

[[Category:Vascular]]