First International Study of Infarct Survival - ISIS-1

Description:

Early beta-blockade for mortality after acute myocardial infarction.

Hypothesis:

To assess the effects of early beta-blockade following acute myocardial infarction.

Study Design

Study Design:

Patients Screened: Not given
Patients Enrolled: 16,027
Mean Follow Up: 20 months
Mean Patient Age: 58

Patient Populations:

Acute MI within 12 hours

Primary Endpoints:

Vascular mortality

Drug/Procedures Used:

Atenolol 5-10mg IV over 5 minutes, followed by 100 mg/day for 7 days.

Principal Findings:

A total of 8037 patients were randomized to atenolol, and 7990 to control.

Vascular mortality during the treatment period (days 0-7) was significantly lower (2p less than 0.04) in the treated group, (3.9% versus 4.6%), but this 15% relative difference had wide 95% confidence limits (from 1 to 27%). No subgroups were identified in which the relative reduction in days 0-7 was clearly better, or clearly worse, than 15%.

At one year, overall vascular mortality was significantly lower for the atenolol group (life-table estimates: 10.7% atenolol vs 12.0% control; 2p less than 0.01).

A substudy reviewed records for 193 of 217 early deaths (79 allocated to atenolol and 114 allocated to control). There was a lower rate of deaths attributed to myocardial rupture or electromechanical dissociation in the atenolol group. There was a slightly higher incidence of fatal ventricular fibrillation and aortic dissection in the control group, and of bradycardia/asystole in the atenolol group. The data did not indicate any substantial contribution from mechanisms such as limitation of infarct size or prevention of reinfarction or cardiac arrest.

Interpretation:

Beta blockade, administered early in the course of myocardial infarction, improves clinical outcome.

References:

1. Lancet 1986; 2 (8498):57-66 Final results
2. Lancet 1988; 1(8591):921-3 Mechanisms of early mortality reduction

Clinical Topics: Arrhythmias and Clinical EP, Implantable Devices, SCD/Ventricular Arrhythmias

Keywords: Myocardial Infarction, Ventricular Fibrillation, Heart Arrest, Bradycardia


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