Debate Continues over Distal Protection in MI Patients
AIMI trial results sobering; limitations may have influenced results.
Some lesions may be more amenable to distal protection than others, according to a speaker at the TCT meeting yesterday.
In a flash debate and discussion, three leaders in the field, David Antoniucci, MD, in the Department of Cardiology, Careggi Hospital, Florence, Italy, Joseph P. Carrozza, Jr, MD, of Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, and Franz-Josef Neumann, MD, PhD, Arztlicher Director of Herz-Zentrum Bad Krozingen, discussed the pros and cons of distal protection in treating patients with acute myocardial infarction (MI).
The primary focus of the debate was on the AIMI trial results, which examined the use of the Angiojet device (Possis) in patients with acute MI.
These results were “sobering,” according to Carrozza. The primary endpoint of infarct size measured at one month was higher in patients treated with thrombectomy vs. controls (See Figure).
The AIMI trial randomized 480 patients with ST-elevation MI to principle percutaneous coronary intervention (PCI) or rheolytic thrombectomy followed by definitive PCI.
Angiographic myocardial blush post-PCI was the secondary endpoint, and some benefit was seen with respect to the blush grade.
There were no significant differences between the two groups in terms of “hard criteria” such as TIMI flow grade, Neumann said. He said this is similar to findings reported in other studies.
Differing viewpoints
Using the EMERALD trial as an example, Neumann said the distal protection device did not reduce infarct size or improve microvascular blood flow or event-free survival.
The problems with the EMERALD trial results, Antoniucci said, are flaws in the study design. He said that the absence of cardiogenic shock and the criteria for the use of the Guardwire in that trial may have influenced the results.
Antoniucci argued that occlusive antiembolic devices, filters and thrombectomy devices have intrinsic limitations that could result in incomplete protection, or even an increased risk of embolism, noting specifically that some stenting techniques have been associated with differing risks of embolism.
Antoniucci said that the higher incidence of baseline grade-3 TIMI flow in AIMI favored the control groups (19% with rheolytic thrombectomy vs. 27% control; P<.05)
He also pointed to the fact that seven out of nine randomized controlled trials have been positive for the use of various distal protection devices, including Angiojet, in patients with AMI. Carrozza and Neumann countered that those trials were smaller than the AIMI trial.
Although it is true that thromboembolism and atheroembolism both occur after primary PCI, Carrozza said, and that both conditions are associated with adverse events, despite removal of thrombus and atheroma by embolic protection devices, it may not be accurate to deduce that removal of atheroma improves clinical outcomes. “There are no data for that,” Carrozza said.
Summing up his part of the debate, Carrozza said, “there are little data supporting the clinical benefit of thrombectomy, thrombus aspiration and distal protection devices in acute myocardial infarction. If there is no benefit, there is no indication for routine use.”
Neumann echoed these sentiments, with the caveat that some lesions may be more amenable to distal protection than others.
He noted data from Mizote et al, which examined the Guardwire compared with usual care.
In that trial, consecutive patients with AMI who had been treated with distal protection and those who did not have distal protection were subdivided according to whether or not they had angioscopically defined ruptured plaque at the culprit lesion.
Researchers in the trial noted improvements in ST-segment resolution, myocardial blush grade, and left ventricular ejection fraction in patients with distal protection among patients with ruptured plaque. This suggests that preventing ruptured plaque in the first place could improve circulation, Neumann said.
Neumann said the jury is still out as to whether distal protection and thrombectomy in AMI can be fixed. The keys to the question might lie in better devices or techniques and in properly identifying the appropriate setting for distal protection.