Boston Scientific Corp. and J&J on Tuesday released separate data showing their drug-eluting stents helped keep blood vessels clear of blockages in high-risk patients with coronary artery disease.

Stents are tiny wire-mesh tubes inserted into the blood vessels to prop them open. The drug-eluting varieties slowly release drugs that stop the vessels re-clogging.

This companies presented the data at the Paris Course on Revascularization, the largest interventional cardiology conference in Europe.

Boston Scientific said follow-up results from its Taxus V study, using ultrasound within the vessels, showed improvement in patients with small vessels, large vessels and severe blockages requiring multiple, overlapping stents, compared with a control group.

Recipients of the Taxus stent developed vessel obstructions in 13.2 percent of cases at nine months, versus 31.8 percent of patients in the control group. The study tracked 1,172 patients at nine months.

In a second Boston Scientific study, called Taxus VI, a continued reduction in the rate of repeat procedures was demonstrated after two years in 428 patients. The rate of patients living free of serious complications was 90.3 percent, versus 79 percent for the bare-metal stent control group, the company said.

Rival stent maker Johnson & Johnson released positive data from two studies measuring the performance of its Cypher drug-coated stent in diabetic patients, who can be more difficult to treat because of smaller blood vessels.

In a study of 607 diabetic patients, called Arts II, J&J said those receiving a Cypher stent had lower rates of major complications such as death, Stroke and Heart attack than diabetic patients who underwent bypass surgery in a predecessor trial.

The company also looked at Cypher’s effectiveness in a group of 274 diabetic patients in a Portuguese study, where it found results that compared favorably with those for non-diabetic patients.

Johnson & Johnson also released longer-term results from its Ravel study that showed patients who received the Cypher drug-coated stent required fewer repeat procedures after four years than those receiving bare-metal stents. In that study, 91.8 percent of patients with a Cypher stent were free of major complications including Heart attack  and death after four years, compared with 73.4 percent in the control group.