MedWire - ACC.08 Scientific Sessions (Chicago, IL, USA), March 30, 2008: In high-risk patients undergoing percutaneous coronary intervention (PCI) for non-ST segment elevation acute coronary syndromes (ACS), the use of the EZ FilterWire system does not improve clinical outcomes over the conventional method.
This was the main finding of the Angioplasty Balloon-Associated Coronary Debris and the EZ FilterWire (A-F) randomized clinical trial, which was presented during a late-breaking clinical trials session organised by the Society for Cardiovascular Angiography and Interventions and held during the ACC Annual Scientific Sessions [1].
A-F trial: FilterWire EZ fails to improve PCI outcomes in NSTEMI
Mark Webster, Auckland City Hospital, New Zealand
Dr. Webster presented data from the A-F trial [1], which looked at the use of coronary artery stenting over the FilterWire EZ system versus a conventional guidewire in patients with non-ST segment elevation myocardial infarction (NSTEMI).
The rationale for the study was that there had been no prior randomized trials investigating the use of the FilterWire EZ in such patients, although studies have been conducted in patients with stable angina, ST segment elevation myocardial infarction (STEMI), and vein graft disease.
However, in the high-risk NSTEMI population, Dr. Weber concluded that, “there is not a role for routine use of vascular protection devices.”
Vascular protection devices such as the FilterWire EZ system are used to catch thrombotic and other material that may become dislodged during stent placement.
Dr. Weber and team prospectively recruited patients at 14 centers in Australia, New Zealand, and Canada. A total of 151 patients were recruited into the unblinded trial as part of a pilot protocol. The study was designed to allow for expansion of up to 450 patients.
The recruited patients were randomized to PCI with or without the FilterWire EZ. Two sizes of device were used: one with a diameter of 3.5-5.5 mm and the other with a slightly smaller diameter of 2.25-3.5 mm.
Dr. Weber noted that patients were selected to be at “high-risk,” meaning that they had to have clinical features of non-ST segment elevation ACS 24 hours before angiography. Patients had to have elevated levels of troponin, angina at rest, and a demonstrable and dynamic ST/T-wave change on electrocardiograph (ECG), but not STEMI.
Patients also needed to have a “high-risk” culprit lesion with two or more of the following angiographic features: intra-coronary filling deficit consistent with the presence of thrombus, lesion ulceration, eccentric shape, an irregular or a scalloped border, abrupt edges to the lesion, or a lesion that was over 2 cm in length.
At baseline, Dr. Weber noted that 77 patients in the FilterWire EZ group had a mean age of 58 years, while 74 patients in the conventional PCI (control group) had a mean age of 60 years. He commented that the patients’ age was “a little younger than in other intervention trials.”
There were also fewer patients with diabetes than in previous trials (16% of patients in the FilterWire EZ group and 26% in the control group).
The majority of patients in each arm were male (83% and 89%, respectively) and 40-42% had previous angina, around one third had never smoked, 39-46% had hypertension and one half to two thirds had dyslipidemia.
Baseline angiographic findings were similar among the groups, except for lesion ulceration, which affected 5.6% of lesions in patients undergoing PCI with the vascular protection device and 11.2% of lesions in those who underwent conventional PCI.
Dr. Weber stated that around two-thirds of patients, 60% in the FilterWire EZ arm and 67% in the control group, had TIMI grade III flow at entry.
In terms of the primary endpoint of the trial - the in-hospital rate of major adverse cardiovascular events (MACE), namely death, recurrent myocardial infarction, emergency coronary artery bypass grafting, and repeat target vessel revascularization - there was no significant difference between the two groups.
In-hospital MACE occurred in 11.7% of patients in the FilterWire EZ arm and in 9.5% of the patients in the control group. No differences in secondary endpoints were noted (see Table below).
Secondary endpoints
| EZ FilterWire | Conventional PCI (control) |
| MACE at 30 days (%) | 12 | 11 |
| Change in CK-MB | 5.1 | 4.1 |
| Change in troponin T | 0.4 | 0.4 |
| Device success (%) | 97 | n/a |
| Embolic recovery (%) | 42 | n/a |
| Post-PCI TIMI III (%) | 94 | 94 |
CK-MB, creatine kinase-muscle bone; TIMI III, thrombolysis in myocardial infarction grade III; n/a, not available
After performing subset analyses - in patients who had been treated with glycoprotein IIb/IIIa inhibitors, those who had diabetes, patients who had received clopidogrel before PCI, and those who had received previous thrombotic therapy - there was still no difference between the results achieved with the FilterWire EZ and conventional PCI.
Dr. Weber commented on the disappointing results: “This finding came as something of a surprise” adding that there is “pretty good evidence that distal emboli do develop during PCI in patients with NSTEMI.”
So, he questioned, were the wrong patients selected? Did they not look at the right lesions in these patients? Was the FilterWire EZ not positioned correctly such that it wasn’t catching all the emboli? Or was the study population too small?
Dr. Weber concluded that the FilterWire EZ does not appear to be suitable for routine use in NSTEMI, although further analysis of data from the trial may identify patients who could be at particular risk of embolism and may therefore benefit more than others from using the FilterWire EZ.
Reference
- Weber M, Whitbourn R, McClean D, et al. Vascular protection in high-risk non-ST elevation acute coronary syndromes: The Angioplasty Balloon-Associated Coronary Debris and the EZ FilterWire (A-F) Randomized, Controlled Trial. Abstract 2404-3. SCAI-ACCi2 Late-Breaking Clinical Trials II: Acute Myocardial Infarction. SCAI-ACCi2 Scientific Sessions, March 29 to April 1, 2008, Chicago, Illinois, USA.
