One day after he became the world's fifth recipient of a permanent artificial heart, Jack C. Burcham was returned to surgery this afternoon to stem bleeding inside his chest cavity.

Blood was seeping from sutures connecting his aorta to the Jarvik-7 heart, but the condition was "not life-threatening," said Dr. Allan Lansing, medical spokesman for Humana Heart Institute International. Burcham, he said, was in critical but stable condition.

The problem was similar to the one that necessitated a second open-heart operation for William J. Schroeder hours after he received an artificial heart last November.

Lansing said Burcham's doctors suspect that the bleeding was caused by the strain of the synthetic device's motion on the stitches that connect the remnant of Burcham's natural heart to the flexible cuff of the artificial heart. That problem has not occurred in laboratory animals and the cuff is made of woven Dacron, which is used routinely to replace damaged sections of blood vessels in humans.

Burcham lost at least 21 pints of blood the night after his surgery -- the average adult male has about 10 pints -- and doctors at first thought the bleeding was caused by the additional maneuvering that was required to fit the heart into Burcham's chest cavity.

In one sense, today's episode was gratifying for the medical team here because it will help doctors define some of the questions yet to be answered about the experimental device.

"I think that we are learning that . . . a human aortic wall is different from an animal's. And that even though the same type of synthetic material is used for vascular grafts in other situations, the motion of the mechanical heart in pumping action, putting strain perhaps on the back of the aorta, the suture line that should hold does not," Lansing said.

As a result, Lansing said, doctors will seriously consider changing their technique for future patients by wrapping another synthetic material such as Teflon around the juncture between the human tissue and the cuff and stitching the material into place in order to "buttress" the suture line.

"I think the situation is that that's why we're doing this, that it's an experimental procedure. We're trying to find out what the problems are, what the difficulties are and how you prevent them. In other words, how you make it a routine procedure in everybody rather than an adventure," Lansing said.

Doctors had hoped that they could avoid taking Burcham back into surgery today. This morning they inserted an extra drainage tube in his chest but blood continued to accumulate.

Instead of reopening Burcham's chest at the breastbone, Dr. William C. DeVries, the lead surgeon, made a lateral incision in Burcham's left side to help drain the chest and give doctors a better view of the back of the heart.

Their main concerns now are the increased risk of infection from the second, two-hour operation and the effect that the added stress will have on Burcham's kidneys, which were barely functioning before his implant.

Burcham, a retired railroad engineer from LeRoy, Ill., will be carefully monitored tonight for signs of further bleeding. If none occurs, doctors hope to begin giving him doses of anticlotting medication. While that will increase the likelihood of further bleeding, it apparently is necessary to prevent strokes such as the one that disabled Schroeder last December.

Excessive bleeding has plagued all four of DeVries' artificial-heart patients, as the medical team tries by trial and error to find the right level of anticlotting medication.

The world's first recipient of a permanent artificial heart, Barney B. Clark, suffered nosebleeds and blood pooling in his joints throughout the 112 days he lived after his implant.

Thirteen days after the third recipient, Murray P. Haydon, got the plastic-and-metal heart, he underwent a second open-heart operation because blood began accumulating in his chest after a monitoring tube was removed from a large blood vessel near the artificial heart.