A study assessing Boston Scientific's (Natick, Massachusetts) EZ FilterWire to catch bits of plaque and blood clot that break loose during percutaneous coronary intervention (PCI) in patients with acute coronary syndrome has been discontinued after it failed to show that it can reduce rates of major cardiovascular complications.

The A-F study was presented in a late-breaking clinical trials session at the annual meeting of the Society for Cardiovascular Angiography and Interventions (SCAI; Washington), in partnership with American College of Cardiology (ACC; Washington) at the ACC annual meeting in Chicago this week.

The EZ system was first approved by the FDA in August 2004 for use in coronary saphenous vein graft, and then for the application of carotid artery stenting in 2006 (Medical Device Daily, Aug. 25, 2004/Dec. 15, 2006).

The device is a coronary guidewire, with a plastic sack attached to it shaped like a windsock. The "windsock"-like sack features small holes allowing blood to flow through but catching larger debris. During PCI the FilterWire is positioned in the coronary artery downstream of the lesion; both the device and, with it, any debris are removed after the procedure.

The study was originally designed to include 450 patients but was stopped after an analysis of the first 150 patients. The researchers found that rates of major cardiovascular complications during hospitalization consisting of death, heart attack, emergency bypass surgery, or repeat procedure in the treated artery were no different in the two groups (12% in the FilterWire group vs. 10% in the control group).

Investigators were focused on patients with arterial blockages that appeared particularly likely to be a source of downstream debris during PCI. In addition, myonecrosis, or debris-caused damage to the heart muscle resulting from blockage of tiny blood vessels, is fairly common. PCI is associated with myonecrosis in about 25% of patients with non-ST-elevation myocardial infarction (STEMI) acute coronary syndromes. The condition also encompasses unstable angina.

"This was a study in a new population," Mark Webster, MD, director of the cardiac catheterization laboratory at Auckland City Hospital (Auckland, New Zealand), told Medical Device Daily. And he called this group "the bread and butter of our work: unstable angina patients. We tried to pick a high-risk group within that population. They were required to have pain at rest and other features, like being at risk for distal embolism."

He added: "I believe that there are a bunch of patients with acute coronary syndrome who would benefit from these devices, but we didn't identify them with this study."

Although the FilterWire captured debris in the bloodstream in nearly half of patients, it did not reduce damage to the heart muscle. This was the first trial to evaluate a vascular protection device in patients with NSTEMI acute coronary syndromes.

"Although there are other mechanisms, distal embolism of atherosclerotic plaque and/or thrombus is recognized to be a frequent cause," Webster said.

Webster said that he did not know of any other studies that are being planned for this particular indication.

In another study from the ACAI-ACCi2 Summit related to aspiration with PCI:

An analysis of the Thrombus Aspiration during Percutaneous Coronary Intervention in Acute Myocardial Infarction (TAPAS) study showed that the link between deep myocardial perfusion and better clinical outcomes, apparent at 30 days, is still strong after one year.

The one-year results of TAPAS analyzing the effectiveness of the Export Aspiration Catheter from Medtronic (Minneapolis) and focusing on patients suffering from STEMI were reported in a late-breaking clinical trials session.

Felix Zijlstra, MD, PhD, of the University Medical Center Groningen (Groningen, the Netherlands) and his colleagues recruited 1,071 patients with STEMI, assigning 535 to PCI, supported by the Export aspiration catheter, and 536 to PCI using conventional techniques.

To assess the quality of myocardial perfusion, the researchers documented myocardial blush grade, a myocardial blush grade of 0 or 1 indicating that little or no X-ray dye has reached from the surface artery into the heart muscle, a sign that the microcirculation is blocked; a myocardial blush grade of 3 indicating that X-ray dye has reached deep into the heart muscle, a sign of good blood flow through the microcirculation. A myocardial blush grade of 2 falls in between.

Analysis of the elevated ST-segment on the electrocardiogram its return to normal baseline was also used to gauge the quality of blood flow to the heart muscle.

During angiography, researchers observed a blush grade of 0 or 1 in 17% of patients treated with the aid of the aspiration catheter and in 26% of patients treated with conventional PCI (p less than 0.001). At 30 days, clinical outcomes were strongly related to the degree of myocardial reperfusion.

The rate of death in patients with a myocardial blush grade of 0/1, 2 and 3 was 5.2%, 2.9% and 1.0% respectively (p equals 0.003). The combined rates of repeat heart attack, repeat procedure in the target artery and death in patients with a myocardial blush grade of 0/1, 2 and 3 were 14.1%, 8.8% and 4.2%, respectively (p less than 0.001).

At one-year follow-up, mortality was significantly lower in patients treated with the aspiration catheter (p equals 0.04), as was a combination of death and heart attack. A similar, highly significant relationship was observed between myocardial blush grade and death, or a combination of death and repeat heart attack (p equals 0.001).

The researchers concluded that the degree of blood perfusion into the heart muscle helps to predict the patient's clinical condition and that aspiration of debris from the treated artery during PCI can reduce the risk of death and repeat heart attack, even one year later.

SCAI is a 4,000-member organization promoting quality in invasive and interventional cardiovascular medicine through physician education and representation.