An eminent cardiologist has taken issue with Merck & Co’s interpretation of data from the APPROVe study, released last week, which it said showed that Vioxx’ elevated risk of thrombotic diseases did not extend after the treatment was halted.

Merck acknowledged last Thursday that the number of strokes or heart attacks among patients during the one-year follow-up indicated a 64% higher risk of cardiac problems among those who had taken Vioxx compared with a placebo in the year after treatment was stopped.

The company said the overall numbers involved were too small to be of statistical significance. The new APPROVe data found that there were 28 thrombotic events in the Vioxx group, compared to 16 among those on placebo.

But Steve Nissen of the Cleveland Clinic in the USA, said on Friday that the increase in risk might indicate some kind of long-term effect, and patients should be followed for two or three years to assess this, as the result only narrowly missed being a statistically significant difference.

Merck has not yet decided whether it will continue to study the patients in the study, saying it would discuss this with the Food and Drug Administration and the study’s steering committee.

More than 11,500 lawsuits have been filed against Merck by people, or their survivors, claiming to have been harmed by Vioxx, and the company may be able to use the new APPROVe data to argue in court that Vioxx cannot be blamed for heart attacks caused in the months after a patient stopped taking the drug.

The news comes after a bad spell in the courts for Merck, with the last two cases resulting in multimillion damages against the firm.