Antiplatelet therapy: reduces deaths, strokes, MI.

Clinical bottom line (level 1a)

  1. Antiplatelet therapy should be considered for almost all patients with suspected acute myocardial infarction, previous MI, stroke or transient ischaemic attack, angina, arterial bypass surgery, or angioplasty- it reduces deaths, strokes and MIs (NNT = 31 at 1-3 years) .
  2. Patients continue to gain benefit for at least three years.
  3. 75 to 325 mg of aspirin daily is as effective as higher doses.
  4. No antiplatelet medication has been shown to be better than another.
  5. Patients without previous cardiovascular disease do not benefit from prophylactic antiplatelet therapy.
Antiplatelet Trialists' Collaboration : British Medical Journal 1994; 308: 81-106
Expires July 2004

The study

Systematic review of unconfounded randomised controlled trials of
  • Patients: history of MI, suspected or define AMI, stroke or transient ischaemic attack; other high risk patients (unstable angina, post-CABG, post-PTCA, stable angina or coronary artery disease, atrial fibrillation, rheumatic valve disease, valve surgery, intermittent claudication, peripheral grafts, peripheral angioplasty, renal dialysis, diabetes and other); low risk patients in primary prevention trials
  • Intervention: who received at least one month's treatment antiplatelet therapy: cyclooxygenase inhibitors- aspirin, flurbiprofen ibuprofen, indobufen, naproxen, sulphinpyrazone, trifusal; phosphodiesterase inhibitors- dipyridamole, E5510, RA233; platelet calcium ion channel inhibitors- suloctidil; phospholipase inhibitors- hydroxychloroquine; thromboxane synthetase inhibitors, receptor blockers or both- dazoxiben, piracetam, picotamide, ridogrel, sulotroban, daltroban, GR32191; agents with direct effects on platelets- ticlopidine compared with another treatment or placebo
  • Outcome: all deaths, deaths with a vascular cause, probable or definite non-fatal myocardial infarction and strokes
Articles found in all using MEDLINE and Current Contents, 1966 to March 1990 (search terms: not detailed) and manual searches of journals, references of studies found, abstracts from Proceedings, inquiry with antiplatelet manufacturers, collaboration with the trial register of International Committee on thrombosis and Haemostasis and colleagues who coordinated the studies. Both published and unpublished studies available for review by 30 th March 1990 were included

Selection criteria: set criteria (detailed in text)
Appraisal criteria: reviewed by the collaborative review group. Intention to treat analyses were performed for all studies, extra data being requested where necessary. Final analyses were checked with principal investigators before inclusion in the overview. Results combined using the Peto method of meta-analysis
Articles excluded if:

  • 11 studies in prior MI (19791 patients (adjusted figure))
  • 9 studies in acute MI (18773 patients (adjusted figure))
  • 18 studies in prior stroke/TIA (11707 patients (adjusted figure))
  • 104 studies of other high risk (22976 patients (adjusted figure))
  • 3 studies of primary prevention (22212 patients (adjusted figure))

Not significantly heterogeneous for high risk groups. Significant heterogeneity between high and low risk groups.

The evidence

Outcome Time to outcome CEREERARR
(95% CI)		NNT
(95% CI)
MI, stroke, vascular death in all patients 1-3 years 5400
(11.5%)		 4183
(14.7%)		 3.26%
(2.77% to 3.75%)		 31
(27 to 36)
MI, stroke, vascular death in prior MI 1-2 years 1693
(17.1%)		 1331
(13.5%)		 3.60%
(2.60% to 4.60%)		 28
(22 to 38)
MI, stroke, vascular death in acute MI 1-2 years 1348
(14.4%)		 992
(10.6%)		 3.80%
(2.85% to 4.74%)		 26
(21 to 35)
MI, stroke, vascular death in prior stroke/TIA 2-3 years 1301
(22.2%)		 1076
(18.4%)		 3.73%
(2.27% to 5.18%)		 27
(19 to 44)
MI, stroke, vascular death in unstable angina 6-12 months 285
(14.1%)		 182
(9.14%)		 4.92%
(2.95% to 6.89%)		 20
(15 to 34)
MI, stroke, vascular death in other high risk 1-2 years 1058
(9.20%)		 784
(6.90%)		 2.31%
(1.61% to 3.01%)		 43
(33 to 62)
MI, stroke, vascular death in low risk (primary prevention) 5-6 years 708
(4.80%)		 652
(4.50%)		 0.38%
(-0.10% to 0.87%)		 260
(NNT = 115 to infinity;
NNH = 1020 to infinity)

  • In this overview, no antiplatelet medication was more effective than any other. Further trials have been performed after this publication.

Comments

  1. Aggregating of a variety of disparate conditions into the category 'other high risk' may not be applicable as the outcomes in these groups vary, and the amount of data available for some of the conditions is low.
  2. Benefits continued to end of studies. No information on length of time antiplatelet medication should be used.
  3. Non-significant trend for increased number of non-fatal strokes for low-risk patients on anti-platelet medication. Haemaorrhagic strokes may be reduced if tight control of blood pressure is performed.

Citation

  1. Antiplatelet Trialists' Collaboration , : Collaborative overview of randomised trials of antiplatelet therapy I: Prevention of death, MI and stroke by prolonged antiplatelet therapy in various categories of patients. British Medical Journal 1994; 308: 81-106
Search Terms: aspirin and angina in Cochrane
Contributor: Nick Shenker and Chris Ball, July 2000
Reviewer: Deepak L Bhatt

Clinical Question.
Patient cardiac disease
Intervention or Exposure aspirin
Outcome death, infarction, stroke, TIA, revascularisation