Percutaneous coronary intervention

Synonyms: percutaneous transluminal coronary angioplasty, formerly known as balloon angioplasty

What is percutaneous coronary intervention?

Percutaneous coronary intervention (PCI) is one of the two coronary revascularisation techniques currently used in the treatment of coronary heart disease, the other being coronary artery bypass grafting (CABG).

PCI involves non-surgical widening of the coronary artery, using a balloon catheter to dilate the artery from within. A metallic stent is usually placed in the artery after dilatation. Antiplatelet agents are also used. Stents may be either bare metal or drug-eluting.¹

Indications for percutaneous coronary intervention¹

Note that indications for PCI may change as the procedures continue to be refined, and with emerging evidence.

• ST segment elevation myocardial infarction (STEMI):²
  

  • When available, angioplasty with stenting is the optimal method of reperfusion for STEMI. The target 'door to balloon time' is 90 minutes.

  • As rescue treatment in patients treated by thrombolysis - if there is failure to reperfuse, further ischaemia or further myocardial infarction (MI).

  • As early intervention in patients treated with thrombolysis.

• Non-ST elevation acute coronary syndrome (NSTACS) - unstable angina and non-ST elevation myocardial infarction (NSTEMI):
  

  • For patients who are at medium-to-high risk of subsequent cardiac events, offer angiogram and/or PCI before discharge. Early invasive investigation and revascularisation (compared to conservative treatment) may reduce subsequent MI and refractory angina.

• Overall, PCI treatment for non-acute coronary artery disease has shown no evidence of an effect on death or MI when compared with medical therapy.^{1 3 4}

• Revascularisation is appropriate for patients with stable angina for:¹
  

  • Persistent limiting symptoms despite optimal medical therapy.

  • Certain anatomical patterns of disease or a proven significant ischaemic territory (even in asymptomatic patients). Significant left main artery stenosis, and significant proximal left anterior descending disease, especially in the presence of multivessel coronary artery disease, are strong indications for revascularisation.

  • In the most severe patterns of coronary artery disease, CABG appears to offer a survival advantage and a marked reduction in the need for repeat revascularisation (but with a higher risk of a cerebrovascular event), especially in left main artery disease.

• There is currently little evidence comparing PCI and CABG for patients with coronary artery disease and heart failure.⁵

Contra-indications and other considerations

• Consider the pros and cons of PCI versus optimal drug therapy and/or CABG.^{6 7} For example, multiple comorbidities may increase the risk of complications making medical therapy more appropriate.

• Because antiplatelet drugs are crucially important after PCI (to prevent thrombosis in the stent - see below), decisions about PCI and the type of stent used must bear in mind:⁸
  

  • Is there likelihood that surgery will be needed? Consider the increased risk of bleeding with antiplatelet drugs but risk of thrombosis if these drugs are stopped.

  • Can the patient adhere to antiplatelet treatment (and is there funding to do so)?

  • Are there any contra-indications to antiplatelet drugs?

The procedure⁹

PCI options for patients with coronary artery disease include percutaneous balloon angioplasty, stent placement or percutaneous cutting balloon. Percutaneous laser coronary angioplasty may be used for carefully selected patients for whom conventional angioplasty would otherwise be technically difficult.¹⁰

• PCI should be done by experienced, high-volume operators and institutions.

• No anaesthetic is needed, although patients may be given a sedative. Patients can usually mobilise a few hours afterwards and go home the same or next day.

• The technique involves gaining arterial access via the femoral, radial or brachial arteries. Under fluoroscopy, a guide wire is passed into the coronary artery and across the stenosis; the balloon or stent catheter is passed over it, and the lesion dilated and/or stented.

• Glycoprotein IIb/IIIa inhibitors are given in 'high-risk' procedures; opiates may be used if angina occurs during angioplasty.

• When administered during PCI, intravenous glycoprotein IIb/IIIa blockers reduce the risk of all-cause death at 30 days but not at six months, and reduce the risk of death or myocardial infarction at 30 days and at six months, at a price of an increase in the risk of severe bleeding.¹¹

Types of coronary stent

Currently, stents are implanted in nearly all patients undergoing PCI because the stent gives various advantages over simple balloon dilatation.

The two main types are:

• Bare metal stent (BMS) - usually stainless steel.

• Drug-eluting stent (DES) - metal struts are coated with a growth-inhibiting agent that inhibits smooth muscle cell proliferation:
  

  • This reduces the frequency of restenosis (by about 50%).

  • However, it also slows the process of re-endothelialisation, thus prolonging the risk of stent thrombosis.

  • In the UK, most DESs utilise paclitaxel - an anti-cancer agent, or sirolimus - an immunosuppressant.

  • Use of a DES is preferred to use of a BMS.¹

A DES is recommended for use in PCI if:¹²

• The target artery to be treated has a calibre <3 mm, or the lesion is longer than 15 mm; and

• The price difference between a DES and a BMS is no more than £300.

Post-procedure

Antiplatelet drug treatment following PCI^{1 13}

• All patients should take aspirin indefinitely (as secondary prevention of cardiovascular disease).

• 'Dual antiplatelet therapy' is required for patients with coronary stents, to reduce the risk of stent thrombosis:
  

  • This normally comprises aspirin and clopidogrel. The duration of clopidogrel treatment depends on the clinical setting but current recommendations are usually:
    

    • For a BMS, clopidogrel for at least one month.

    • For a DES, clopidogrel for at least 12 months. Some cardiologists feel that clopidogrel should be continued indefinitely.

• Antiplatelet agents should not be stopped. Patients are advised to carry a warning card. Cards are available from the United Kingdom Clinical Pharmacy Association (admin@ukcpa.com).¹⁴

• If surgery is required, consider whether the antiplatelet drugs can be continued; consult with a cardiologist as to the risks of discontinuing these drugs and any necessary precautions.

• The use of proton pump inhibitors (PPIs) together with clopidogrel (to prevent gastric bleeding) is controversial, after evidence suggesting that PPIs may worsen outcomes and that the two drugs may interact.

Driving¹⁵

After elective PCI:

• Group 1 licence - stop driving for one week; can recommence thereafter if there is no other disqualifying condition. DVLA need not be notified.

• Group 2 licence - must not drive and must notify DVLA. May be relicensed/licensed after at least 6 weeks if LV ejection fraction is at least 40%, the requirements for exercise or other functional tests can be met, and there is no other disqualifying condition.

Complications¹⁶

There is a greater risk of complications if aged over 65 years, female, renal dysfunction or diabetes. The potential complications include:

• Coronary artery or aortic injury: dissection, rupture.

• Bleeding: usually at the access site (groin if femoral approach; wrist if radial approach), but may be internal bleeding, including cardiac tamponade.

• Infection: local at the access site, or bacteraemia.

• Renal failure: contrast used in angiograms can worsen renal function, especially in patients with prior renal dysfunction.

• Stroke: embolic from blood clots formed during the procedure.

• Myocardial infarction: secondary to dissection or thrombosis (which may be within the stent or distal to PCI from plaque debris). Stent thrombosis is most frequent during the first month but can occur months or years after the PCI.

• Restenosis of the stent: typically develops within 3-6 months and presents as a return of angina. It rarely causes acute myocardial infarction.

• Minor complications are allergy to the contrast medium, nephropathy and complications at the access site, such as bleeding and haematoma.

Possible future developments

• Bioabsorbable stents are being trialled and have potential advantages.¹⁷ However, NICE recommends that bioresorbable stent implantation to treat coronary artery disease should only be used in the context of research as evidence on efficacy is inadequate and evidence on its safety has shown an increased risk of serious complications in the longer term.¹⁸

• Triple antiplatelet therapy may be beneficial.¹⁹

• New antithrombotic drugs, such as thrombin receptor (protease-activated receptor-1 (PAR-1)) antagonists might reduce thrombosis without affecting haemostasis.²⁰