Acute coronary syndromes

Cardiovascular diseases
Volume 192 - Issue 12

The invasive approach to acute coronary syndrome: true promise or false premise?

Author:  Peter L Thompson

Med J Aust 2010; 192 (12): 694-695. || doi: 10.5694/j.1326-5377.2010.tb03704.x
Published online: 21 June 2010
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Debating early invasive versus medical management

When there is an apparent threat of myocardial damage from unstable angina or non-ST-elevation myocardial infarction (NSTEMI) (collectively referred to as the non-ST-elevation acute coronary syndromes, or NSTEACS), early opening of the culprit atherothrombotic coronary artery would seem logical. Clinical trials of early coronary intervention (the invasive approach) have shown variable results when applied to all patients with NSTEACS, but clear benefits when applied to high-risk patients.1,2

On this basis, the 2006 National Heart Foundation of Australia (NHFA) guidelines3 concluded that the evidence was strong enough to recommend that all high-risk patients with NSTEACS should be transferred urgently to a cardiac catheterisation facility to permit early coronary angiography and percutaneous coronary intervention or coronary artery bypass surgery, if appropriate. The advice is consistent with United States1 and European2 guidelines and has recently been reaffirmed and followed with recommendations for implementation in Australia.4 But does the invasive approach show true promise, or is it based on a false premise, as suggested by Forge in this issue of the Journal?5

Forge makes the point that the ICTUS (Invasive versus Conservative Treatment in Unstable Coronary Syndromes) trial, published in 2005,6 was overlooked in drawing up the NHFA guidelines and did not show any benefit of an invasive strategy in patients with NSTEACS. It is certainly a valid point that the ICTUS study was conducted with treatments that were more modern and effective than the earlier studies, which were conducted in the 1990s, before the widespread use of enoxaparin, clopidogrel and high-dose statins.7 However, several important points are relevant in analysing the results of the ICTUS study.

Firstly, the 1-year mortality in the ICTUS study was 2.5%, which was lower than the 1-year mortality in typical Australian patients with NSTEACS (10.5% for NSTEMI and 3.3% for unstable angina),8 indicating that patients in the ICTUS trial were not high-risk patients.

Secondly, the lack of difference in outcome between the conservative and the invasive approach in the ICTUS study was largely due to an apparent increase in minimal myocardial infarction in the interventional group, driven by small rises in creatine kinase MB levels that accompanied the interventional procedure. Such periprocedural infarctions have nowhere near the same long-term prognostic impact as spontaneous infarctions.9

Thirdly, despite the enhanced medical management, selection of a conservative approach in the ICTUS trial did not preclude subsequent coronary intervention. Forty per cent of patients in the conservative treatment arm of the trial required coronary intervention during the initial hospital course.

Finally, the ICTUS study was conducted in hospitals with ready access to interventional procedures when they were thought to be necessary. This was not a study whose results can be readily applied to the management of patients in Australian regional hospitals.

Forge’s suggestion that modern medical management could render invasive treatment irrelevant takes an unduly optimistic view of the power of medicines. There is no doubt that intensive therapy with statins and antiplatelet agents can significantly improve outcomes for patients with NSTEACS,10,11 but the conclusion that conservative management alone will remove the need to open a blocked artery is hardly justified based on the ICTUS study results, which comprise just over 10% of the evidence base.1-3,6,7

Nor is it valid for Forge to conclude that a strategy of early transfer of patients with NSTEACS to hospitals providing percutaneous coronary intervention is not in agreement with US guidelines. In the 2007 revision of the US guidelines for acute coronary syndromes,1 which considered the ICTUS results in detail, an initial conservative approach treatment option was accorded the status of only a Class IIB recommendation (ie, “may be considered”), whereas the early invasive approach was accorded Class IA status (“recommended”).1 The European guidelines2 concur with these recommendations. The Australian guidelines3 and the recommendations for implementing them4 are also consistent with these conclusions.

In summary, the active use of evidence-based medical treatments for NSTEACS should be encouraged, as these are underutilised in patients with acute coronary syndromes in Australia.12 However, if a patient with an acute coronary syndrome with high-risk features presents to a regional hospital, guidelines based on sound evidence support early invasive treatment, and arrangements should be made for early transfer to a hospital that can provide coronary angiography and, if appropriate, percutaneous coronary intervention.

Author

  • Peter L Thompson MD, FRACP, FACC1
  • 1. Gairdner Campus, West Australian Heart Research Institute, Perth, WA.

Correspondence: peter.thompson@health.wa.gov.au

Competing interests

I have received royalties from Churchill Livingstone/Elsevier for the textbook Coronary care manual. I have also received speaker fees from Merck Sharp & Dohme, Schering-Plough, Pfizer, AstraZeneca and Solvay, and reimbursement of travel expenses from AstraZeneca and Pfizer.

References

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