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Original Articles: Adult Cardiac

Invited Commentary

Department of Thoracic Surgery, Royal Brompton Hospital, Sydney St, London, SW3 6NP United Kingdom

(Email: e.lim{at}rbht.nhs.uk).

In relation to current expenditure on research to improve outcomes after coronary surgery and the costs of patient care, it is unlikely that any new discovery will achieve a better cost–benefit ratio than postoperative aspirin prescription at today's prices. Because aspirin is widely available as a generic drug, free from patent and no longer associated with corporate branding of a single multi-national pharmaceutical giant, it has certainly suffered from lack of commercially funded research and notable absence of marketing, rendering it the frumpy cousin (in accordance with a general rule in life) to the more glamorous, seductive but phenomenally more expensive alternatives.

After a large cohort study [1] and numerous randomized trials [2], it is widely accepted that optimum antiplatelet therapy reduces in-hospital mortality and ischemic events in association with improved graft patency, although not necessary causal to it. However, it is a mistake to assume that the beneficial effects are experienced uniformly by all patients receiving standard dose aspirin in light of accumulating reports identifying aspirin resistance. Unfortunately, definitions of aspirin resistance remain broad and encompass both biochemical (markers of platelet activation) and clinical (clinical events, despite aspirin administration) outcomes, with measure that are as yet not standardized. At present there is no cut-off limits defined for the multitude of measures of platelet activation (aggregometery, platelet function analyzer (PFA)-100 measurements, p-selectin expression, and others), the multitude of activating agents (collagen, epinephrine, adenosine-diphosphate, and others) and number of type of clinical outcome measures (cardiovascular, peripheral arterial, and other events).

Bevilacqua and colleagues [3] are to be commended in conducting a study that links biochemical to clinical outcomes. Aspirin resistance was measured using the PFA-100 device and residual platelet reactivity defined as a collagen-epinephrine closure time of less than 190 seconds (see article for details). They identified an independent association between residual platelet activity after a month of aspirin administration with nearly a two-fold increase in adverse outcome (at a mean follow time of 32 months) a composite of death, myocardial infarction, recurrent angina, and documentary evidence of ischemia and graft failure. One of the strengths of the study was a routine stress testing and protocol managed further investigations eliminating the bias of differential investigation performed for symptoms alone.

Prior to changing their practice, most clinicians usually prefer to wait for reassurance (by similar reports) that this is not a chance finding. Ideally this should be a proactive process rather allowing our patients to experience possible adverse events while waiting for others to confirm or refute these findings. If this observation proves robust, much more work will be required for a line of investigation to overcome aspirin resistance, ideally starting with a uniform definition (avoiding specific cut-off values if there is a continuous gradation of risk) before addressing controversies of different dosage regimens [4] and alternative agents [5] to improve the outcomes for our patients.

	References

Top References

 

1. Mangano DT. Aspirin and mortality from coronary bypass surgery N Engl J Med 2002;347:1309-1317.[Medline]
2. Collaborative overview of randomised trials of antiplatelet therapy - II: maintenance of vascular graft or arterial patency by antiplatelet therapy BMJ 1994;308:159-168.[Abstract/Free Full Text]
3. Bevilacqua S, Alkodami AA, Volpi E, et al. Risk stratification after coronary artery bypass surgery by a point-of-care test of platelet function Ann Thorac Surg 2009;87:496-502.[Abstract/Free Full Text]
4. Lim E, Ali Z, Ali A, et al. Indirect comparison meta-analysis of aspirin therapy after coronary surgery BMJ 2003;327:1309.[Abstract/Free Full Text]
5. Lim E, Cornelissen J, Routledge T, et al. Clopidogrel did not inhibit platelet function early after coronary bypass surgery: a prospective randomized trial J Thorac Cardiovasc Surg 2004;128:432-435.[Abstract/Free Full Text]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Eric Lim Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lim, E. Search for Related Content PubMed PubMed Citation Articles by Lim, E. Related Collections Extracorporeal circulation Related Article