MI- IV BETA BLOCKER CAN REDUCE VASCULAR MORTALITY BUT HAS SIDE-EFFECTS (ISIS-1)

Three-part Question: In a patient with acute MI, does immediate use of IV beta blocker decrease mortality?

Search Terms: (Medline) myocardial infarction, beta antagonists

The Study:
Single-blinded randomised controlled trial with intention-to-treat. Pts entering CCU with suspected MI, within 12 hrs of onset of symptoms and not already on beta blockers or calcium antagonists.
Control group: (N=7990) no placebo given, beta blockers avoided unless they were clearly indicated
Experimental group: (N=8037) atenolol 5-10 mg IV immediately followed up by 100 mg/d for 7 days

The Evidence:

Outcome	Time to Outcome	RRR	ARR	NNT
overall mortality	7 days	13%	0.006	167
	95% Confidence Intervals:	-1% to 27%	-0.000 to 0.012	NNH = 3555 to inf; NNT = 81 to inf
vascular mortality	1 yr	11%	0.013	77
	95% Confidence Intervals:	3% to 19%	0.003 to 0.023	44 to 315

Comments:

1. 25% of pts on control group discharged on beta blockers compared with 35% in the treatment group which influenced mortality results at 1 yr.
2. increased use of inotropes in treatment group (5% vs 3.4%) on day 0-1, but no increase in deaths
3. trend for more complete heart block in treatment group but no increase in deaths
4. see also systematic overview, Yusuf S, Peto R, Lewis J, Collins R, Sleight P. Beta blockade during and after myocardial infarction: an overview of the randomised trials. Prog Cardiovasc Dis 1985;27:335-71.

Expiry date: March 1998

References:

1. ISIS-1 Collaborative Group. Randomised trial of intravenous atenolol among 16027 cases of suspected acute myocardial infarction: ISIS-1.

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