Angioplasty and Stenting

Angioplasty is the dilatation of a narrowed or occluded blood vessel with a balloon catheter, and stenting is the placement of a metal mesh tube to hold the vessel open. The procedure is done through a percutaneous puncture of an artery (or a vein), under fluoroscopic control after diagnostic angiography.

A wire crosses the lesion, a balloon sized to the adjacent normal vessel (usually 1:1) is inflated to 6 to 20 atmospheres for 30 to 120 seconds, and a stent is deployed if the result is poor (residual stenosis over 30%, a flow limiting dissection, or elastic recoil) or when stenting is the planned treatment.

Bare metal stents, drug eluting stents (releasing an antiproliferative drug to reduce restenosis), drug coated balloons, covered stents (for aneurysm exclusion, rupture and fistula), and self-expanding and balloon expandable designs are used in different territories. Atherectomy and thrombectomy devices treat heavily calcified or thrombotic lesions.

The procedure is used in coronary, carotid, subclavian, renal, mesenteric, iliac, femoropopliteal, tibial, venous and dialysis access disease.

Peripheral arterial disease affects about 200 million people worldwide, with critical limb ischaemia in 1 to 2% of those with disease, and renal artery stenosis occurs in 1 to 5% of hypertensive patients (up to 40% in older patients with vascular disease).

Endovascular treatment has replaced surgery as the first treatment for many lesions because it is less invasive, with shorter stays, lower early morbidity and similar early patency; surgery remains preferred for long occlusions, small vessels and some multilevel disease.

Indications.

• Intermittent claudication limiting lifestyle, after failure of exercise and risk factor treatment, with a lesion suitable for endovascular treatment.
• Critical limb ischaemia (rest pain, ulcers, gangrene) for limb salvage, at multiple levels as needed.
• Acute limb ischaemia after thrombolysis or thrombectomy, to treat the underlying lesion.
• Symptomatic carotid stenosis (generally 50 to 99%) in patients at high surgical risk or with a hostile neck, and vertebral and subclavian stenosis with steal or symptoms.
• Renal artery stenosis (haemodynamically significant) with refractory hypertension, flash pulmonary oedema, or unexplained renal decline, and fibromuscular dysplasia (angioplasty alone).
• Chronic mesenteric ischaemia with symptoms (post-prandial pain and weight loss) and acute mesenteric occlusion.
• Aortic coarctation, aortoiliac occlusive disease, and aneurysm repair with stent grafts (covered stents).
• Venous obstruction: iliac vein compression, superior vena cava syndrome, central vein stenosis in dialysis patients, and dialysis fistula stenosis.
• Complications of surgery: graft stenosis and anastomotic narrowing.

Contraindications. Absolute contraindications are few: uncorrectable bleeding disorder, active infection at the access site or bacteraemia (for stent placement), and a lesion that cannot be crossed or is unsuitable (long diffuse disease with small run off vessels).

Relative contraindications are contrast allergy, severe renal impairment, uncontrolled hypertension, anticoagulation that cannot be paused, and life expectancy that makes the benefit unlikely. In asymptomatic mild disease, treatment does not improve outcome.

Preparation.

• Informed consent, with benefits, alternatives (supervised exercise, medical treatment, surgery) and risks explained.
• Review of renal function, haemoglobin, platelets, clotting, glucose, and medicines (antiplatelet treatment: aspirin and clopidogrel loaded or continued; anticoagulants and metformin managed by the local rule).
• Hydration, fasting for 4 to 6 hours, and a plan for the access site (femoral, radial, brachial or pedal) after ultrasound or diagnostic imaging.
• Local anaesthetic, with sedation as needed, intravenous antibiotics for graft or stent grafting, and monitoring of heart rate, blood pressure, and oxygen saturation.
• Full length arterial imaging (duplex, CT or MR angiography) before the procedure to plan access and treatment.

Technique. The artery is accessed using a micropuncture needle under ultrasound control, and a sheath is placed. Heparin (about 3000 to 5000 units, or 70 to 100 units for each kg) is given.

A wire and catheter cross the lesion (for occlusions, subintimal or retrograde techniques may be required), and angiography with contrast measures the stenosis and the reference vessel diameter.

Pre-dilatation with a balloon is followed by stent deployment (self-expanding for tortuous and mobile vessels such as the femoropopliteal and carotid segments, balloon expandable for ostial and rigid lesions such as renal and iliac origins). Embolic protection devices are used in carotid stenting.

Final angiography checks the residual stenosis (aim under 30%), flow, dissection, perforation and distal embolism. Pressure gradients across the lesion (over 10 to 20 mmHg for a significant stenosis, or a peak systolic gradient over 5 to 10 mmHg at rest) can be measured. The sheath is removed with a closure device or manual pressure.

Findings on completion.

• Technical success: residual stenosis under 30% with brisk flow, and no flow limiting dissection.
• Residual stenosis, recoil or dissection: further balloon inflation or stent placement.
• Distal embolism: aspiration thrombectomy, thrombolysis or stent deployment.
• Perforation or rupture: balloon tamponade, covered stent, reversal of heparin and surgical help.
• Slow flow or no reflow (coronary and carotid): vasodilators, thrombus aspiration.
• Haemodynamic results: improvement in the ankle brachial index of over 0.15 after leg revascularisation, reduction of the pressure gradient, and improved distal flow.

Critical findings needing immediate action. Arterial rupture with extravasation and hypotension (covered stent, balloon tamponade, surgery), acute stent thrombosis (thrombolysis or thrombectomy), distal embolisation with limb or organ ischaemia, stroke during carotid stenting (urgent neurological assessment, intracranial angiography and thrombectomy),

pseudoaneurysm or expanding groin haematoma (compression under ultrasound control, thrombin injection, or surgery), retroperitoneal haemorrhage (resuscitation, CT, intervention), contrast anaphylaxis, and acute kidney injury.

Complications. Access site complications are the commonest: haematoma (up to 5 to 10%), pseudoaneurysm (0.5 to 2%), arteriovenous fistula, retroperitoneal bleeding (about 0.5% with femoral access), and nerve injury.

Procedural complications include dissection, vessel perforation or rupture, distal embolism (blue toe syndrome), acute thrombosis, contrast nephropathy, stroke (carotid stenting, about 2 to 5%), cholesterol embolism, stent fracture or migration, and infection.

Late complications are restenosis (20 to 40% at 1 year for bare balloon angioplasty in the femoropopliteal segment, lower with drug coated devices and stents), stent thrombosis, and graft infection. Mortality in elective procedures is under 1%.

Aftercare.

• Bed rest for 2 to 6 hours after femoral access (shorter with closure devices or radial access), with observation of vital signs, the puncture site, and distal pulses for the first hours.
• Continue hydration, and check creatinine at 48 to 72 hours in patients with risk factors.
• Antiplatelet treatment: aspirin lifelong, and a second antiplatelet agent (clopidogrel) for 1 to 3 months after peripheral stenting, and for 6 to 12 months after drug eluting coronary stents or carotid stenting (duration set by the treating specialist).
• Statin treatment, blood pressure and diabetes control, smoking cessation, and exercise programmes.
• Surveillance by duplex ultrasound at 1, 6 and 12 months and yearly, with ankle brachial index measurement; recurrent symptoms prompt early imaging.
• Return for groin swelling, bleeding, limb pain, coldness, colour change, fever, chest pain, or neurological symptoms.

Special groups.

• Diabetes and renal failure: higher restenosis, calcified tibial disease, and a risk of contrast nephropathy; limb salvage teams manage the diabetic foot.
• Elderly patients: lower procedural risk with endovascular treatment than surgery.
• Women and small vessels: higher access complication rates.
• Children: rare (coarctation, renal artery stenosis in fibromuscular dysplasia, Takayasu arteritis) with specialist teams.
• Pregnancy: avoid unless essential.
• Regions: Takayasu arteritis, thromboangiitis obliterans, diabetic limb disease and late presentation with gangrene are common; access to endovascular treatment is limited to a few centres.