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Evidence summaries

Timing of Thrombolytic Therapy in Acute Myocardial Infarction

The beneficial effect of thrombolytic therapy appears to be substantially higher in patients presenting within 2 hours after symptom onset compared to those presenting later. Level of evidence: "B"

A systematic review 1 including 22 RCTs with a total of 50 246 subjects was abstracted in DARE. The NNT per treatment delay was determined on the basis of 11 RCTs. Of the patients included, 5 762 were randomised within two hours of symptom onset.

Absolute mortality reduction per 1 000 treated patients in patients who presented:

- within one hour of symptom onset: 65 lives saved (95% CI 38 to 93); NNT 15.

- in second hour after symptom onset: 37 lives saved (20 to 55); NNT 27.

- 2 to 3 hours after symptom onset: 26 lives saved (14 to 37); NNT 38.

- 3 to 6 hours after symptom onset: 29 lives saved (19 to 40); NNT 34.

- 6 to 12 hours after symptom onset: 18 lives saved (7 to 29); NNT 56.

- 12 to 24 hours after symptom onset: 9 lives saved (-5 to 22); NNT no significant difference.

Proportionate mortality reduction in patients treated:

- within one hour: 48% (95% CI 31 to 61)

- within two hours: 44% (32 to 53)

- later 20% (15 to 25).

Comment: The quality of evidence is downgraded by inconsistency (the delay between randomization and actual initiation of therapy was not reported) and review quality (limited literature search and the lack of validity criteria applied to the primary studies).

    References

    • Boersma E, Maas AC, Deckers JW, Simoons ML. Early thrombolytic treatment in acute myocardial infarction: reappraisal of the golden hour. Lancet 1996 Sep 21;348(9030):771-5. [PubMed] [DARE]

Primary/Secondary Keywords