A cardiologist told jurors that plaque, hypertension, obesity, and job-related stress, not Merck’s Vioxx painkiller, caused the heart attack that an Idaho postal worker blames on the drug.

Frederick Humeston, 60, had a “small, modest heart attack” on September 18, 2001, one day after learning details of a secret videotape made by U.S. Postal Service inspectors who questioned his knee injury, a Merck expert, Dr. Theodore Tyberg, said. Mr. Humeston took Vioxx for two months for the injury before his heart attack.

“I believe it was a combination of risk factors” that caused a heart attack “triggered by an acutely stressful event in his life,” Dr. Tyberg testified in Atlantic City, N.J.

“There’s no significant evidence that Vioxx, when used for less than three months, predisposes anyone to a heart attack.”

Dr. Tyberg’s testimony was the most extensive at the five-week trial to refute Mr. Humeston’s claim that Vioxx triggered his heart attack. Mr. Humeston claims that Merck, the no. 3 American drugmaker, hid the drug’s risks before withdrawing it last year, saying that long-term use doubled the risk of heart attacks.

Dr. Tyberg, who has appeared on Oprah Winfrey’s television show, said people with Mr. Humeston’s risk factors have heart attacks “all the time.” He walked jurors through evidence that he said showed how those risks built up for 30 years.

Dr. Tyberg said that Mr. Humeston’s left knee, which he first injured as a decorated U.S. Marine in the Vietnam War, is severely arthritic. That injury forced Mr. Humeston into a sedentary life in recent years, increasing the strain on his heart, Dr. Tyberg said. He also injured his right knee in July 2001, Dr. Tyberg said.

Stress affected Mr. Humeston for years and forced clashes with postal supervisors who questioned limitations on his work duties that physicians imposed to protect his knee, Dr. Tyberg said. A Merck attorney, Diane Sullivan, showed letters and memos that Mr. Humeston wrote complaining that his bosses made him exceed those limitations.

“There’s a drumbeat of anger and frustration and hostility and stress,” Dr. Tyberg told jurors.

Mr. Humeston’s heart attack was triggered, he said, by a videotape made in July 2001 by postal inspectors who questioned if he exceeded his work restrictions. His doctor reviewed the tape on September 17, 2001, and told Mr. Humeston about it and the postal service’s desire to reduce its workforce by “a sizeable number of people,” Dr. Tyberg said.

Earlier in the trial, which began September 14, Mr. Humeston and his cardiologist testified about the videotape incident.

On cross examination, an attorney for Mr. Humeston, Moshe Horn, suggested that Dr. Tyberg exaggerated the role that stress played in Mr. Humeston’s heart attack. He said Mr. Humeston had stress for three decades and never had a heart attack.

“In all the other things you talked about, would you agree with me that he wasn’t on Vioxx?” Horn asked. The cross examination continues today.