Angina: long-term oral anticoagulation increased bleeding without reducing cardiovascular events

Clinical bottom line (level 1b)

  1. Patients with unstable angina who received long-term oral anticoagulation compared with control were not less likely to have a cardiovascular death, myocardial infarction or a stroke.
  2. Patients on long-term anticoagulation were at increased risk of major bleeding (NNH = 76 at 5 months) .
OASIS Investigators : J Am Coll Cardiol 2001; 37 : 475-484
Expires March 2004

The study

Single-blinded concealed randomised trial with intention-to-treat
Setting: hospitals, worldwide

3712 patients (aged mean 64, 60% male) with chest pain suspected to be due to unstable angina or myocardial infarction without ST elevation

Excluded if
  • expected poor compliance
  • cardiogenic shock
  • normal coronary vessels
  • other unrelated diseases that might limit life expectancy to < 6 months
  • contraindication to heparin, hirudin or warfarin; or bleeding on heparin or hirudin
  • stroke in previous year
  • renal impairment
  • need for long-term anticoagulant therapy
  • recent or planned PTCA; CABG within 1 weeks
  • pregnancy
  • aged < 21 or > 85

Control Group: (n = 1848, 1848 analysed): control
Experimental Group: (n = 1864, 1864 analysed): warfarin 10 mg bolus then 3 mg for 3 days, then adjusted so INR 2.0 to 2.5
Patients were intially randomised to heparin or hirudin for 3 days. Patients were randomised into this study after 12 to 48 hours.
99.6% followed for 5 months

The evidence

Outcome Time to outcome CER EER RRR
(95% CI)		 ARR
(95% CI)		 NNT
(95% CI)
cardiovascular death, myocardial infarction or stroke 5 months 155
(8.32%)		 140
(7.58%)		 9%
(-13% to 27%)		 0.74%
(-1.00% to 2.48%)		 140
(NNT = 100 to infinity;
NNH = 40 to infinity)
readmission to hospital with unstable angina 5 months 172
(9.23%)		 168
(9.09%)		 1%
(-21% to 20%)		 0.14%
(-1.72% to 1.99%)		 730
(NNT = 58 to infinity;
NNH = 50 to infinity)
PTCA or CABG 5 months 460
(24.7%)		 445
(24.1%)		 2%
(-9% to 13%)		 0.60%
(-2.16% to 3.36%)		 170
(NNT = 46 to infinity;
NNH = 30 to infinity)
major bleeding 5 months 25
(1.34%)		 49
(2.65%)		 -98%
(-220% to -23%)		 -1.31%
(-2.21% to -0.41%)		 -76
(-240 to -45)

Comments

  1. 28% of patients in the warfarin group had stopped therapy at 35 days.

Citation

  1. OASIS Investigators , : effects of long-term moderate-intensity oral anticoagulation in addition to aspiring in unstable angina. J Am Coll Cardiol 2001; 37 : 475-484
Search Terms: from ACP Journal Club other articles noted
Contributor: Chris Ball, March 2002
Reviewer:

Clinical Question.
Patient unstable angina
Intervention or Exposure long-term oral anticoagulation
Comparison placebo
Outcome death, myocardial infarction, revascularisation, major bleeding