Vasodilators after myocardial infarction-ISIS IV.

Although small trials had suggested unrealistically high benefits from the use of vasodilators in acute myocardial infarction (MI), there was considerable statistical uncertainty about these benefits. Angiotensin-converting enzyme (ACE) inhibitors are clearly beneficial for left ventricular dysfunction after MI, but it was uncertain whether there was risk (from hypotension) for some patients in the early hours of an MI. After the GISSI-3 and International Studies of Infarct Survival (ISIS-4) trials it is now clear that nitrates are safe, but used routinely the small mortality reduction was not statistically significant. In ISIS-4 the results with magnesium were disappointing, with a worrying small excess mortality. On the other hand, routine use of ACE inhibitors in this early phase showed a statistically significant 5 to 10% reduction in mortality. There was greatest benefit in those with more obvious left ventricular damage. Since it is not easy to identify all such patients in the first hours, a policy of initial treatment of all, then later reassessment, is safe and would produce the greatest overall benefit.