The government should have required more tests before it approved two drugs for use by heart patients, who suffered a startling increase in death rates after taking them, two cardiologists said Wednesday.

Federal officials put new restrictions on the drugs in 1989 after a study found unusually high death rates among patients being treated for arrhythmia. The drugs remain on the market for treatment of life-threatening arrhythmias, and their use for that purpose is not being questioned.The Food and Drug Administration's approval of the drugs flecainide in 1985 and encainide in 1986 for broader purposes was the subject of a hearing Wednesday by a House Government Operations subcommittee.

"We need to examine why, for over three years, FDA allowed these potentially lethal drugs to be given to persons whose lives were not immediately threatened by their mild arrhythmias," said Rep. Ted Weiss, D-N.Y., chairman of the human resources subcommittee.

In other prepared testimony, Dr. Thomas Graboys, clinical director for Lown Cardiovascular Center in Boston, said the FDA should have had results from a mortality study before it allowed the drugs to be used to treat moderate arrhythmias.

Dr. Bertram Pitt, director of cardiology at the University of Michigan Medical Center, said that at the time the FDA was considering the drugs, many cardiologists felt it "might not be appropriate" to approve them for patients with mildly irregular heartbeats.

A board monitoring the safety of the study in April 1989 found that of 730 patients who received the drugs for about 10 months, 57 died or suffered cardiac arrest; of 725 patients receiving only placebos, 22 died of cardiac arrest.