Deaths and hospitalizations caused by chronic heart failure can be reduced by nearly one-third by giving patients a 30-year-old diuretic called Aldactone, which was not thought to be useful in treating heart patients, according to a new study released Monday.

Nearly 4.7 million Americans suffer from chronic heart failure, in which the heart has grown too weak to pump effectively, and about 250,000 die from it each year. Powerful new drugs, such as ACE inhibitors, beta-blockers and stronger diuretics, were thought to have made Aldactone superfluous in treating heart disease. But researchers have recently found that it has other actions that complement the effects of these drugs.

Studies in the last five years or so, however, have shown that ACE inhibitors do not block a number of other adverse effects produced by the hormone. Aldosterone causes stiffness of heart and blood vessel tissues, and stimulates production of hormones, such as norepinephrine, that overstimulate the heart and increase the risk of heart failure. Unlike ACE inhibitors, Aldactone can block these hormone actions.