Navy Cmdr. Donal Billig, testifying in his court-martial yesterday, dismissed as "absolutely meaningless" statistics that showed that his patients died at a rate that was more than twice the national average during his last year as chief heart surgeon at Bethesda Naval Hospital.

Under cross-examination, Billig testified that 14 percent of his heart patients died in or soon after surgery in 1984, but said the figure was meaningless in light of the patients' poor health.

Of six patients who died from September through November of that year, three were "very risky candidates for surgery," Billig said.

"You just can't say high mortality," he said after repeated questions from the prosecutor, Lt. Cmdr. Joseph VanWinkle. "You, commander, don't have any idea how to stratify risk. You just know how to play with numbers . . . . Your analysis of the significance is entirely incorrect."

Billig, 54, is charged with involuntary manslaughter in connection with the deaths of five patients in 1983 and 1984. He also has been charged with 24 counts of dereliction of duty for other operations he undertook at the hospital in 1983. In his third day as a witness, Billig discussed why he joined the Navy in 1982.

Billig, who practiced in New Jersey, had his operating privileges revoked at Monmouth Medical Center in Long Branch after a series of hearings in 1981 in which his competence was questioned. At the end of 1981, he said, he was unemployed and $100,000 in debt.

Billig moved to Pittsburgh and joined a private cardiothoracic group. When he applied to the Navy in 1982, Billig said, he no longer was employed by the cardiothoracic group but still had some heavy debts.

"As of May 1982, then, you had been fired by one group and lost privileges at another?" VanWinkle asked.

"No, we terminated our association," Billig said about the Pittsburgh job. He told Navy recruiters when he applied that he was in private practice, he said.

Billig's statement followed earlier testimony that he did not consider his operating privileges at Bethesda to have been revoked as a result of the Navy accusations. "My cardiac privileges have been lifted," he said, but privileges for other types of surgery had simply "run out" during the last year.

Later, Dr. David Bregman, an expert witness and developer of a balloon pump used worldwide in heart surgery, called Billig "a surgeon with the best intent" who used accepted procedures in cases that had "unfortunate results." Bregman based his comments on a review of the case records and said he had never seen Billig operate.