Myocardial infarction: urgent angioplasty did not improve prognosis.

Clinical bottom line (level 1b)

  1. In patients with first myocardial infarction, a strategy of urgent angiography after thrombolysis did not reduce death or reinfarction at 12 months (NNH = 40 at 12 months) .
SWIFT (Should We Intervene Following Thrombolysis?) Trial Study Group : British Medical Journal 1991; 302: 555-560
Expires November 2003

The study

Unblinded ?concealed randomised trial with intention-to-treat
Setting: 21 district hospitals and regional cardiac centres in UK and Ireland

800 patients (aged mean 55y (SD 9y), 82% male) first myocardial infarction thrombolysed within 3.5 hours of onset of symptoms (diagnosed by symptoms & ST elevation)

Excluded if
  • >69 years old
  • shock (systolic BP <80 mmHg) or hypertension (BP >200/120 mmHg)
  • bleeding diathesis or menstruation
  • active peptic ulceration <1 year
  • surgery or trauma <3 months
  • streptokinase or anistreplase <6 months
  • diabetic proliferative retinopathy
  • life expectancy <2 years


Note:
  • 68% of the experimental group received a further intervention; angioplasty or CABG.


Control Group: (n = 403, 369 analysed): angiography at standard clinical indication
Experimental Group: (n = 397, 374 analysed): urgent angiography within 48h of infarct, with angioplasty or bypass surgery as indicated
Patients also received anistreplase and heparin; and oral beta-adrenoceptor antagonists if there were no contraindications.
93% followed for 12 months

The evidence

Outcome Time to outcome CEREERRRR
(95% CI)		ARR
(95% CI)		NNT
(95% CI)
in hospital mortality . unknown 13
(3.23%)		 11
(2.77%)		 14%
(-89% to 61%)		 0.46%
(-1.91% to 2.82%)		 220
(NNT = 52 to infinity;
NNH = 35 to infinity)
death or reinfarction 12 months 67
(16.6%)		 76
(19.1%)		 -15%
(-55% to 15%)		 -2.52%
(-7.83% to 2.79%)		 -40
(NNT = 13 to infinity;
NNH = 36 to infinity)

  • Mortality in the registered but non-randomised group was markedly higher; 13% vs 3% (in-hospital).

Comments

  1. This study is too small to rule out an important clinical difference in mortality alone.
  2. The combined clinical endpoint of death or reinfarction is not improved, and may be worsened, by a strategy of urgent angiography.

Citation

  1. SWIFT (Should We Intervene Following Thrombolysis?) Trial Study Group , : SWIFT trial of delayed elective intervention v conservative treatment after thrombolysis with anistreplase in acute myocardial infarction. British Medical Journal 1991; 302: 555-560
Contributor: Bob Phillips and Clare Wotton, November 1999
Reviewer:

Clinical Question.
Patient patients with first myocardial infarction
Intervention or Exposure urgent angiography with consideration of surgery/angioplasty
Comparison elective angiography as per usual clinical course
Outcome mortality; reinfarction