Primary PCI in the treatment of acute ST elevation myocardial infarction

The optimal logistics are to get the patient with sudden chest pain lasting > 15 minutes quickly to the cath-lab. An immediate call to central emergency is to be placed, which sends an ambulance equipped with 12-leads ECG. Typical ECG changes  (ST elevations, ST depressions, bundle branch block) should trigger an immediate transfer to the cath-lab table. During the transfer, optimal treatment includes aspirin, clopidogrel and unfractioned heparin. In the cath lab, coronary nitrates are to be given, clopidogrel then for a month thereafter and aspirin for life.

During the last three years (2003-5) primary percutaneous coronary intervention (p-PCI) has become the dominant reperfusion treatment for ST-elevation acute myocardial infarction (STEMI) in most European countries. With this change in the organisation of acute coronary care many practical questions arise.

The aim of this contribution is to provide practical recommendations based on current ESC guidelines for PCI (1) and on the large experience of the Czech Republic, where almost all (93%) STEMI presenting within 12 hours after symptom onset are treated by p-PCI and the use of thrombolysis in this setting is very rare (7%). Transfer for primary PCI and the choice of reperfusion therapy in relation to symptoms duration was described by Kristensen et al. (2, 3).

1. Optimal logistics: get the patient quickly to the cath-lab

The optimal logistics means that a 12-leads electrocardiogram (ECG) is recorded during the first medical contact and the patient is transferred immediately after diagnostic ECG directly to cath-lab table.

 The key steps are optimally as follows:

• The patient with sudden chest pain lasting > 15 minutes calls the central emergency phone number (e.g. 112 in most countries, 155 in the Czech Republic)
• The emergency operator sends an ambulance equipped with 12-leads ECG and other necessary equipment to each patient with sudden onset chest pain suspected to be acute infarction
• ECG is registered at the first medical contact place
• When for any reason the diagnostic ECG has to be recorded in the nearest hospital without cath-lab, the ambulance should wait until the ECG diagnosis is confirmed and immediately take the patient "back on board" and continue to PCI center
• ECG is immediately analysed for possible ST elevations, ST depressions or bundle branch block either by an emergency physician or by a specially educated nurse or is transmitted via GSM phone to the PCI center for immediate analysis
• The presence of any above mentioned ECG changes (ST elevations, ST depressions, bundle branch block) triggers immediate transfer to the cath-lab with the below mentioned medication
• The below mentioned medication is given and the nearest PCI center is informed about the patient and about expected arrival time
• While the patient is transferred, the cath-lab is simultaneously prepared to accept the patient (preparation of the cath-lab includes the arrival of interventional cardiologist)
• Upon arrival at the PCI hospital, the patient is taken from the emergency ambulance (or helicopter) directly to the cath-lab table. This sequence enables arrival at the cath-lab 60 minutes after patient call in many instances and call - cathlab time < 90 minutes in most places in Europe. The organisation and discipline in adherence to this regimen is more important than the distance to the PCI center in kilometers in terms of time saving.

Whenever possible, the following steps should be avoided:

• The ambulance - despite a diagnostic prehospital ECG - brings the patient to the nearest hospital without PCI facilities (this leads to a 30-60 minutes time loss)
• The ambulance leaves the patient at the nearest hospital for the purpose of a diagnostic ECG (additional 30 minutes lost by arranging another ambulance for transfer to a PCI center)
• The patient is taken from the ambulance to the central emergency room or coronary care unit to confirm the diagnosis (this carries an inherent delay of 20-30 minutes compared to the direct route of the ambulance to the cathlab)

2. The antithrombotic treatment before arrival at cath-lab

Aspirin should be given to all patients with STEMI (if no contraindication is present) as soon as possible after the diagnosis is established. The preferred route is intravenous (lysin salicylate 0,5 g) or oral (200 - 400 mg) with chewing the drug.

Clopidogrel is increasingly used, preferably with a loading dose of 600 mg. Despite lacking large evidence from randomised trials, the indirect data clearly benefit this approach. Due to the fact that ca 90% of patients arriving at the cath-lab with suspected STEMI finally undergo PCI and 90% of these receive a stent, clopidogrel would be given anyhow. Our own approach currently is that when a STEMI patient did not receive prehospital clopidogrel, we give him (her) 600 mg immediately upon arrival at the cath-lab.

Unfractionated heparin is still the "golden standard" therapy in patients with STEMI undergoing primary PCI. Most ambulances in the Czech Republic give the iv. bolus of 5000 or 10000 units in the prehospital phase before / during transfer to PCI center.

Thrombolytics are not indicated in this setting. The concept of "lytics-facilitated PCI" has been proved to be inferior compared to simple primary PCI strategy by several randomised trials (LIMI, PRAGUE, ASSENT-4 PCI). The explanation is complex: more strokes and more reinfarctions (stent thrombosis) after "facilitated PCI", rather short "ECG - PCI" time delays in primary PCI patients (short delay makes additional benefit from lytics unlikely), etc.

3. Drugs used in the cath-lab

Intracoronary nitrates are injected to unmask vasospasm and to estimate true vessel sizes (for more appropriate selection of a stent).

GP IIb/IIIa inhibitors for PCI in STEMI are less well investigated compared with acute coronary syndromes without ST elevation. This holds true especially for tirofiban and eptifibatide. Abciximab has been evaluated in five randomised, controlled trials (RAPPORT, ISAR-2, CADILLAC, ADMIRAL and ACE) in association with primary PCI.

A recent meta-analysis concluded that abciximab, as adjunctive therapy to PCI, reduces mortality, TVR, and MACE at 6 months after STEMI. The long-term benefits of abciximab administered during coronary artery stenting in patients with STEMI require more investigation. However, it is not known whether these benefits are still true with the current clopidogrel pre-treatment. All the mentioned trial tested abciximab in the setting without clopidogrel pre-treatment.

No-reflow / slow-flow fenomenon are sometimes treated by intracoronary verapamil, adenosin, nitroprusside or even diluted (1:100 000) epinephrine. None of these drugs was clearly shown to improve the outcome.

Low molecular weight heparins have no evidence to support their use over UFH for PCI in STEMI.

There is currently no evidence-based recommendation to use direct thrombin inhibitors for PCI in STEMI.

We specifically warn against the "bailout" use of thrombolytics in the cath-lab in efforts to recanalise the infarct arteries when primary PCI fails. The success rate of primary PCI in achieving TIMI 2-3 flow in the infarct vessel is 90-95%. In those few patients in whom primary PCI fails to open the vessel, there is a very small likelihood that thrombolytics will be successfull. The opposite is true: the unsucessfull PCI is frequently associated with vessel dissection or even guide wire penetration outside the vessel. This usually has no clinical consequences unless lytics are used. When lytics are given to a patient with failed primary PCI, cardiac tamponade may be the final result of this effort...

4. Early and long-term post-PCI pharmacotherapy

• Aspirin 100 mg / day should be used "for the rest of life" if no contraindication or intolerance is present.
• Clopidogrel 75 mg / day should be used for a minimum of 1 month in patients with bare metal stent and 6 months for those with drug eluting stent.
• Heparin (including LMWH) is not needed after primary PCI unless there is other indication (e.g. atrial fibrillation, deep venous thrombosis, etc.).
• GPIIb/IIIa inhibitors are used during 12-24 hours following PCI in those patients who received this drug during the procedure.
• Statins, betablockers and angiotensin converting enzyme inhibitors are used as in any other STEMI.

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.