The role of angioplasty in acute myocardial infarction.

Thrombolysis has achieved startling improvements in cardiac mortality over the last few years and has traditionally been the first-line treatment for patients presenting with ST-segment elevation. Recently, new preparations have meant thrombolysis can be given more quickly and easily, in many cases even before the patient arrives at the hospital. The patient usually has an angiogram, angioplasty or stent insertion at a later date.

Angioplasty
Coronary angioplasty has been used during the acute stage of MI since the 1980s. In my experience of working in a district general hospital, this technique is mainly used when reperfusion has failed following more traditional thrombolytic therapy. Despite an increase in the number of hospitals opening cardiac catheterisation laboratories ('cath labs'), it seems that the smaller centres tend to concentrate on diagnostic angiography and angioplasty in low-risk cases.

Research has shown good results when comparing the effects of primary angioplasty to thrombolysis. Primary angioplasty has been associated with lower mortality rates and reinfarction (Michels and Yusuf, 1995).

It normally takes longer to organise a patient's transfer to a cath lab than to undertake the simple administration of an intravenous drug. However, research suggests that a delay in primary angioplasty does not affect patency rates and clinical outcomes in the same way as if thrombolytic therapy is delayed (FTTCG, 1994). The use of stents and glycoprotein IIb-IIIa receptor inhibitors has optimised the results of primary angioplasty (McLenachan, 2003).

The Australian system
In Sydney, Australia, most patients with acute MI are treated using primary angioplasty. Thrombolysis is rarely used. The patient is transferred directly from the emergency department to the cath lab, which is staffed 24 hours a day, and angioplasty is performed. The aim is to perform the procedure within two hours of the patient's acute MI, as this provides maximum benefit from the procedure.

Under this regimen, benefits were noted in patients who, if treated in the current UK system, would not be eligible for thrombolysis because of the risk of bleeding. Similarly, in patients in cardiogenic shock or with non-diagnostic ECGs, the choice is often made to withhold thrombolysis if uncertain, rather than risk its complications.

The procedure of angiography in these patients gives medical staff essential knowledge of their coronary anatomy, and immediate diagnosis is possible. This is important, as inappropriate administration of thrombolysis in patients with non-cardiac chest pain has been well documented and is not without complication (Blankenship and Almquist, 1989).

Medical staff are able to perform a ventricular gram during the procedure to establish the patient's left ventricular function. The direct approach appears to reduce the length of hospital stay and the need for diagnostic tests, with obvious time and financial implications. It is also noted that in a few patients acute MI was not due to a thrombotic coronary artery but to problems like intimal dissection and coronary artery spasm. In these cases thrombolysis would be ineffective and it was problems like these and the limited efficiency of thrombolysis (Blankenship and Almquist, 1989) that promoted the development of primary angioplasty for acute MI.

Application in the UK
It is accepted that primary angioplasty is being used in larger specialist hospitals in the UK, but is not readily available to patients admitted to smaller hospitals. It is commonly cited that such hospitals do not have the same outcomes (Vogt et al, 1998).

There is a need for quality assurance but it seems that primary angioplasty may be the only alternative for a large number of patients with acute MI, such as those who present too late for thrombolysis, patients with contraindications or those with non-diagnostic ECGs. The reality is that these patients would not get any reperfusion therapy in a non-specialist hospital, with an adverse effect on in-hospital mortality rates (Barron et al, 1998).

The major issue here seems to be one of logistics. Substantial reorganisation of cardiology facilities and staff would be required in order for all patients in this country to receive primary angioplasty for acute MI. This would require a network of specialist angioplasty centres around the UK, fully staffed with appropriately trained medical, nursing and technical staff, available 24 hours a day, every day of the year. In addition, there would need to be a specialist transportation system in place to ensure that patients in all areas of the UK could have quick access to these centres. The advantages and disadvantages of thrombolysis and primary angioplasty in acute MI are compared in Box 1 and Box 2.

The future
Changes to the UK system would have significant financial implications. On the strength of favourable research into primary angioplasty, the government is investigating its cost-effectiveness (Department of Health, 2000).

Recent research has suggested a possible cheaper and logistically less complicated solution may be to combine thrombolysis and primary angioplasty and that the combination of the two may actually be more beneficial to the patient than either procedure on its own (Fernandez-Aviles, 2004). This would mean that even if the patient has received thrombolysis, they may still be eligible for angioplasty. It would also mean that patients who do not live near a specialist service could still receive their thrombolysis quickly in their local hospital and then be transferred to a specialist centre for angioplasty within 24 hours.

Conclusion
In conclusion, the treatment of acute MI is an area in which research has guided us to think about updating and changing our practice. Although primary angioplasty appears to have additional benefits over thrombolysis on mortality rates, reinfarction and stroke, it is not easy to set up a fast-track primary angioplasty service without major organisational changes and considerable increases in both human and financial resources. This article has been double-blind peer-reviewed.

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