A Payson, Utah, youngster, born with serious heart and other defects, was in critical condition Saturday evening after undergoing heart transplant surgery.

Tracy Leonard, 3, son of Chad and Judy Leonard, did well in the 71/2-hour surgery Saturday morning at Loma Linda University Medical Center, according to Anita Rockwell, a hospital spokeswoman.She said the youngster, who was born with the heart on the right side of his chest and without a spleen, had a single ventricle, which means he had only one pumping chamber. Also, Tracy was afflicted with pulmonary atresia, which means there was no blood vessel to the lungs.

Tracy, who was born Jan. 7, 1986, had undergone heart surgery three times before the Saturday procedure. His parents have known for some time the seriousness of their son's condition.

Because Tracy, who was the subject of a Deseret News feature article Jan. 14, doesn't have a spleen, doctors were fearful that the youngster couldn't survive a post-surgery infection. Doctors had considered a heart and spleen transplant. The operation Saturday was only a heart transplant, and no one was available to explain why doctors decided to proceed without transplanting the spleen as well.

Loma Linda, one of two hospitals in the country that would do such an operation, had previously turned the Leonard family down. Surgeons have never attempted to transplant a heart and a spleen into a child before, Mrs. Leonard said.

Kimberly Blanton, Payson, Tracy's aunt, told the Deseret News that the boy's parents called her and her husband, Lonny, Saturday afternoon.

"The operation went great. Tracy has a new heart, which came with new ventricles. He has responded well so far," Mrs. Blanton quoted Tracy's father as saying.

"He (Tracy) is responding well and is still asleep," she quoted the boy's father as saying at about 3 p.m.

Mrs. Blanton said the heart transplant operation was the first to be performed at the medical center on anyone without a spleen. "I think doctors decided not to do the spleen. Earlier, doctors said that they didn't think he could fight off an infection without a spleen. I don't know what made them change their minds," she said.

Mrs. Blanton said Tracy's parents learned Monday that the transplant operation could be performed. The Leonards were informed Friday afternoon that a donor heart was available, and the couple traveled by jet with their son; Gloria Cox, a maternal grandmother; and a nurse and doctor to California.

Two other children in the family are staying with relatives.

Rockwell said Tracy was placed on the heart transplant list Feb. 7. That meant his name was placed on a national computerized list, United Network for Organ Sharing. He was also placed on a list in California known as the Southern California Organ Procurement and Preservation Center, based in Los Angeles.

She said heart transplant surgery has been performed at Loma Linda Medical Center on 32 American and Canadian infants under six months of age since November 1985, with 28 of the 32 having survived. Doctors at the hospital have performed the same operation on nine other children over the age of six months, with eight surviving, Rockwell said.

Last Nov. 12, Whitney Petersen, another Utah youngster, under six months of age, underwent heart transplant surgery at the same medical center. The youngster had hypoplastic left-heart syndrome, a lethal underdevelopment of the left side of the heart. Whitney is doing just fine, Rockwell said Saturday.

Mrs. Blanton said Tracy's parents appealed to Utahns Saturday for financial help. She said the operation alone will cost thousands of dollars. That does not include money for a private jet and $150 a month that will be needed by the youngster for just one type of medication.

Donations may be mailed to the Central Bank of Springville, Tracy Leonard Heart Trust Fund, 202 S. Main St., Springville, Utah, 84663, or any other Central Bank branch.