Percutaneous coronary intervention

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Percutaneous coronary intervention (PCI) involves procedures on coronary arteries via catheters introduced via peripheral arteries. These are usually:


General considerations

The techniques are widely used and have been refined as a result of multiple clinical trials. Essentially they are either done acutely at primary presentation (primary PCI) of acute coronary syndrome, semi-electively shortly after a presentation with an acute myocardial infarction or electively in the management of coronary artery disease. While like any technique there will be a degree of operator dependence and preference some generalisations are possible and the risks and benefits compared to alternative management strategies are reasonably well understood. We know that in primary PCI, that while the choice of femoral or radial route of initial arterial access makes no significant difference to mortality, incidence of myocardial infarction or stroke, radial access has a lower rate of local vascular complications and is likely to increasingly replace femoral access[1]. The major risk factors for adverse outcome are age and prior general and neurological conditions, particularly cerebrovascular events [2]. Interestingly emergency presentations are more clearly associated with adverse outcomes in the elderly than elective procedures and this may partially reflect better opportunities for evaluating procedure risk in the later group resulting in case selection[3].

Stable coronary artery disease

Successful right coronary artery angioplasty

It is known that optimal medical therapy alone is as efficacious in terms of the outcomes of death and myocardial infarction as optimal medical therapy and percutaneous coronary intervention (PCI) for treatment of patients with stable coronary artery disease[4]. In the case of PCI determined by fractional flow reserve (FFR) at angiographically demonstrated lesions in stable coronary artery disease there is a highly significant reduction in the need for urgent revascularisation compared to best medical therapy[5].

Primary PCI

Disease caused by the slow or sudden blocking of an artery could toward the end of the 20th century be treated by putting tethered devices back along an artery to the site and unblocking it

In the case of myocardial infarction primary percutaneous coronary intervention (primary PCI) is probably economically justifiable in societies with good transport infrastructure and organisation of acute health services, if it can be done within 90 minutes of presentation when the alternative is thrombolysis[6]. Thrombolysis can be combined with late PCI in the window 1 to 3 hours for superior outcome in ST elevation myocardial infarction[7]. There is good evidence for clinical benefit of PCI within 6 hours of thrombolysis in high risk patients [8] from the TRANSFER-AMI trial[9]and fair clinical risk-benefit stratification is possible from meta-analysis[10].

There has been controversy as to the benefit of thrombus aspiration at primary PCI resolved to no net favour due to risk of stroke[11] with primary outcome being very similar[12]. Earlier work such as the TAPAs study had suggested that up to one year in ST-elevation myocardial infarction treated with PCI and stenting [13] an absolute benefit in terms of one year mortality of just over 3%.[14]


Optimal and safe primary PCI depends upon optimal choice of antiplatelet and anticoagulant before, during and after the procedure. A large literature exists and optimal regimes have been defined for many combinations of individual circumstances and interventions such as stents. Specialist guidelines exist and both patients and their non cardiological doctors need to understand some of the issues involved, such as non compliance, with its risk of stent thrombosis. Some very complex regimes designed for example to maximise anticoagulation with its risk of bleeding for the minimal possible time have failed, often due to unforeseen properties of the product such as its antigenicity[15].

Coronary stents

Survival curves for first year after index myocardial infarction in New Jersey over the last 16 years. The crude mortality has decreased acutely for both weekday and weekend admissions (prefixed WE), but after 1999 some factor seems to have increased mortality after 180 days. From Table 3[16]

Coronary artery stents were historically either bare metal or drug-eluting. Bioresorbable vascular scaffolds have become the third main stream technology. Drug-eluting stents have evolved into the standard of care but their rigid walls do not reproduce the plasticity of biological vessels and neo-atherosclerosis can still occur leading to stent thrombosis and repeat vascularisation. The relative merits of the three (and different drugs that are eluted) are currently subject to controversy with financial implications. The drug eluting ones are less likely to re-occlude than the plain ones in the long term[17], but until the endothelium has regrown over them - the process the eluted drugs retard - they are more prone to clotting and occluding.[18][19]. Very early target vessel failure seems slightly more common with bioresorbable vascular scaffolds but over 30 months both have a failure rate of 10%. With current drug thromboprophylaxis strategies (they do differ depending upon the stent!) scaffolds based on everolimus elution have a 2% rate of device thrombosis at 30 months versus less than 1% rate in everolimus eluting metallic stent[20].

In multivessel disease generally coronary-artery bypass grafting has better outcomes than either plain[21] or drug-eluting stents[22] in the domains of:

  1. Mortality rates
  2. Myocardial infarction
  3. Repeat revascularization
  4. Those with diabetes and more than 2 vessel disease[23]

Much of the benefit seems to be in reduced long term complication rate[24] and in selected subgroups such as those with severe left ventricular dysfunction drug-eluting stents are likely to offer better outcome[25]

Dual antiplatelet therapy

At the time of stent insertion, particularly with primary PCI the patient is likely to have a special, probably triple therapy loading regime.

Stent occlusion is opposed by aspirin and a thienopyridine which it is very important to continue for a suitable period, currently given as 6 months to a year for the drug eluting stent, and notably shorter for the plain metal one. If you run into bleeding issues, try not to stop antiplatelet therapy and if you do have to stop it, only the cardiologist is likely to be able to estimate accurately the risk of so doing in terms of stent thrombosis, as it will be a stent specific function of time since implantation.

The combination of aspirin and clopidogrel may be accompanied by bruising, sometimes impressive (particularly if it is sub-conjunctival), but ceasing treatment is a serious decision to be made only with the utmost caution.

Risk benefit of continuing dual antiplatelet therapy

This is an individualised assessment but has an evidence base. The DAPT prediction rule is a score, ranging from −2 to 10 that may help inform clinicians of the relative balance in benefit and harm of dual antiplatelet therapy beyond 1 year following percutaneous coronary intervention[26].

DAPT prediction score
Parameter Score Comment
Younger than 65 years 0
Age 65 to 75 years -1
Age 75 years or older -2 In elderly risk of bleeding on anti-platelets tends to out weigh benefits
Vein graft stent 2 Patients whose vein grafts secondary stenose are high risk of myocardial infarction
Smoking within past year 1
Diabetes mellitus 1
Myocardial infarction at presentation 1 ACS patient proceeding to PCI more likely to benefit from prolonged dual platelet therapy
History of CHF or left ventricular ejection fraction lower than 30%, 2 Disabled heart very likely to benefit from prolonged dual platelet therapy
Stent diameter less than 3 mm 1 Small stents increase relative benefit from antiplatelet agents
Paclitaxel-eluting stent 1 Antiplatet therapy more important in paclitaxel-eluting stents

Combined antiplatelet and anticoagulation therapy

This is likely to be indicated in acute coronary syndrome when the patient is already on anticoagulation for another indication at the time of presentation. ESC consensus guidelines exist[27] and have evolved (latest guideline at into ever greater use of DOAC (NOAC)s at expense of warfarin and the use only of aspirin and clopidogrel rather than other antiplatelet agents. The trade offs had lead to the resources necessary in very tight warfarin control but now reduced dose DOACs are being tried. Essentially in patients at low to moderate bleeding risk, and a good indication anticoagulation (warfarin) is continued with the antiplatelet agents covering the highest risk period of stent thrombosis. Thus elective metal stents get 1 month of triple therapy, elective 'olimus coated stents get 3 months triple therapy and to 12 months an antiplatelet and anticoagulant, while elective paclitaxel coated stents get 6 months triple therapy, then up to 12 months an antiplatelet and anticoagulant. This last regime also applies to all stents used in primary PCI. If risk of haemorrhage is high use bare metal stents in all indications and up to 4 weeks of triple therapy, then in elective patients revert to warfarin but in primary PCI ACS patients give 6 months antiplatelet and anticoagulant before reverting to anticoagulation alone.

Brief overview

The intensive analysis of the clinical trial data suggests:

  • Diabetic patients and those with acute coronary syndrome may be better off with a bare metal stent[28][29]
  • The extensive take up of drug eluting stents based on short term studies showing benefit for easily measured primary cardiac outcome measures rather than awaiting total mortality and cardiac event rates over several years was premature[30]. Not all drug eluting stents are equivalent and indeed the drug of choice is definitely evolving.
  • Patients need to be selected for stent type and this selection needs to consider multiple patient parameters, the cost of the therapy and cost and convenience of long term drug prophylaxis.
  • In patients with stable coronary artery disease on optimal medical therapy of antiplatelet agent, betablockers, calcium channel blockers, nitrates, ACE inhibitors (or proven Angiotensin II inhibitors) and statins the COURAGE trial has confirmed previous studies that the addition of percutaneous coronary intervention (PCI) with stents:
    • reduction myocardial infarction and death is unlikely to be benefical
    • symptom control of angina is likely to be beneficial for the first 3 years but unlikely to be benefical after this with PCI[31]
  • Early stent thrombosis after PCI is associated with[32]:
  • The risk of plain stent thrombosis is associated with[33]:
    • Discontinuing clopidogrel therapy
      • First 30 days after the index PCI hazard ratio = 36 (8 - 168)
      • 30 days to 6 months after the index PCI hazard ratio = 4.6 (1.4 - 15.3)
      • Beyond 6 months hazard ratio = 5.9 (1.7 to 19.8)
    • Undersizing of the coronary stent
    • Poor flow through stent and other technical issues like lesion at arterial bifurcation
    • Concurrent malignancy
    • Coronary artery disease proximal and distal to the stent
    • Dissection
    • No aspirin
    • Ejection fraction <30%
    • Younger age
  • The risk of drug-eluting stent thrombosis is associated with[34][35]:
    • Premature antiplatelet therapy discontinuation
    • Renal failure
    • Lower ejection fraction
    • Acute coronary syndrome at presentation
    • Diabetes mellitus
  • Few doctors, including most cardiologists would have the time to navigate the massive amount of information published in the last few years and translate it into advice that is objective and not subject to selection or other bias.


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