PROVIDENCE, R.I. (AP) _ A Rhode Island cardiologist accused of implanting as many as 55 pacemakers in people who did not need them has been convicted of taking kickbacks from pacemaker companies in return for using their products.

The conviction of Dr. Felix M. Balasco, 46, of Cranston was the first time a physician has been charged and convicted in a Medicare fraud trial involving kickbacks from the pacemaker industry, a federal prosecutor said Friday.

A nine-man, three-woman U.S. District Court jury deliberated 16 hours before convicting Balasco of two counts of Medicare fraud and one count each of extortion and conspiracy, but acquitted him on nine other Medicare fraud charges and another conspiracy count.

Assistant U.S. Attorney Ellen Meltzer said Balasco was the first doctor indicted for kickbacks from the pacemaker industry, although she said manufacturers have pleaded guilty to Medicare fraud. She said no similar cases against doctors are pending.

The jury found that Balasco extorted $4,400 from Pacesetter Systems Inc. of Sylmar, Calif., in January 1981 in return for buying pacemakers with Medicare funds. Meltzer said the doctor threatened not to use Pacesetter's products if the company did not pay the kickbacks.

The electronic devices are implanted in the chest and provide mild, regular electric shocks to stimulate the heart muscle and stabilize the heartbeat.

Balasco also was convicted of receiving a $10,000 kickback in April 1981 from Telectronics Proprietary Ltd. of Englewood, Colo., for buying that company's pacemakers with Medicare funds.

During the trial, the government charged that Balasco received $238,450 in loans and outright payments from Pacesetter and Telectronics from 1979 to 1983. The pacemaker operations were performed at Kent County Memorial Hospital in Warwick.

Balasco was suspended by the Warwick hospital earlier this month following newspaper reports that he implanted as many as 55 pacemakers in patients who did not need them. The state Health Department is investigatin the allegations.

Meltzer said in closing arguments Wednesday that Balasco was a man ''who got greedy'' and ''played two pacemaker companies off each other and sold his business to the highest bidder.''

Balasco faces up to 35 years in prison and $70,000 in fines, Meltzer said. No sentencing date was set pending defense appeal motions, and Balasco remained free on $100,000 personal recognizance.

After the trial, Balasco said the jury took ''the easiest way out'' by acquitting on some counts and convicting on others. ''Find him guilty of something to appease those who find him guilty of everything,'' the doctor said.

Balasco faces 20 years in prison and a $10,000 fine on the extortion conviction; five years and $25,000 on each of the two Medicare fraud convictions; and five years and $10,000 on the conspiracy verdict, Meltzer said.