The defense has rested in the second Vioxx (search) product liability trial after defendant Merck & Co. (MRK) presented a cardiology expert as its final witness.

Dr. John Michael Gaziano, a Harvard Medical School professor, told jurors Wednesday that he believes there is no link between Vioxx and heart attacks, even with long-term use.

In testimony that goes to the heart of Merck's case, Gaziano said low-dose use of Cox-2 inhibitors (search) confers no more risk on users than use of dummy pills. Cox-2 inhibitors block the enzyme that promotes inflammation, but protect the stomach lining, unlike some other anti-inflammatory drugs.

There is no proof that either short-term or long-term use of the now-withdrawn painkiller leads to increased risk of serious cardiovascular complications, according to Gaziano. The seven-week trial has focused on an Idaho postal worker who blames his 2001 heart attack on Vioxx.

Frederick "Mike" Humeston, 60, of Boise, took Vioxx for about two months, to relieve knee pain from a Vietnam War wound, before he was stricken. Merck acknowledges links to heart attacks and strokes after 18 months' use, but contends that Humeston had not been taking Vioxx long enough to be at risk.

Gaziano, an expert in cardiology and epidemiology testifying for Merck, contradicted statements of experts who asserted on Humeston's behalf that Vioxx caused Humeston's heart attack.

He also contradicted the findings of the Food and Drug Administration (search), which last April concluded that Cox-2 inhibitors are associated with increased risk of heart attack, stroke and death with long-term use.

Merck blames the heart attack on Humeston, saying elevated blood pressure, excess weight and on-the-job stress triggered the attack, which Humeston survived.

His case is one of more than 7,000 suits filed against Merck over Vioxx, and plaintiff lawyers say thousands more suits will be filed in the future.

In the first Vioxx trial, a Texas jury in August found Merck liable in a Vioxx user's death, awarding his widow $253 million. That will be cut to about $26 million because Texas caps punitive damages. Merck plans to appeal that verdict.

Merck may call one more witness in its defense, but no decision had been made early Wednesday, spokesman Jim Fitzpatrick said. Closing arguments are expected to begin Friday.