TAPAS Serves up One-Year Data, Strengthens Case for Pre-PCI Thrombus Aspiration in Acute MI

March 30, 2008

March 30, 2008 (Chicago, IL) - The better 30-day reperfusion and clinical outcomes achieved by extracting culprit thrombus prior to stenting in acute ST-elevation MI (STEMI), seen in a recently published randomized trial, were sustained to at least a year, reported investigators here at the American College of Cardiology 2008 Scientific Sessions/i2 Summit-SCAI Annual Meeting [1].

The finding strengthens the case for myocardial "blush" grade as a predictor of clinical outcomes after PCI-treated acute MI, at which it is so effective, one of the trial's lead investigators says, that it supports thrombus aspiration as a routine prelude to the procedure. Blush grade reflects contrast density in the myocardium at angiography.

However, not all observers who saw the trial's one-year data think they necessarily point to a major, routine role for thrombus aspiration in acute STEMI, and even the trial's investigators acknowledge that the study wasn't powered to solidly show whether the catheter can improve mortality or clinical event rates; they say a far larger trial would be needed to confirm that.

The Thrombus Aspiration During Percutaneous Coronary Intervention in Acute Myocardial Infarction (TAPAS) study compared stenting for acute STEMI with or without prior application of the Export Aspiration Catheter (Medtronic), which is designed to suck out and capture thrombus from within an infarct-related artery, presumably thrombus that is causing the MI. More than 1000 patients with acute STEMI were randomized, prior to angiography, to stenting preceded by thrombus aspiration (and predilatation only as necessary) or to stenting always preceded by balloon inflation. Bare-metal stents were the only kind used in the study.

As reported about two months ago and covered by heartwire at the time, thrombus aspiration was associated with significantly improved myocardial reperfusion as gauged by blush grade, compared with stenting with predilatation [1]. The better reperfusion with aspiration was accompanied by significantly better resolution of ST-segment changes. Mortality and rate of major adverse cardiac events were similar between the groups at 30 days, but both end points correlated significantly with blush grade and resolution of the ST-segment changes independently of baseline clinical and angiographic features.

In his presentation of the TAPAS one-year data that show the sustained effect of blush grade, Prof Felix Zijlstra (Thoraxcentre Academic Hospital Groningen, the Netherlands) recommended thrombus aspiration as an "excellent" first step in PCI for acute STEMI. "It's quite clear that [myocardial blush grade] is a principal surrogate end point for mortality; it's an excellent predictor of outcome at one year," he said. "I think we should remove these thrombi before we stent an infarct-related coronary artery."

Outcomes at one year by myocardial blush grade* in TAPAS

End point Grade 3 (%) Grade 2 (%) Grade 0 or 1 (%) p for trend
Death 3.7 4.7 11.0 0.001
Death/nonfatal reinfarction 6.1 7.6 14.8 0.001
*0–1=no or minimal myocardial blush; 2=moderate blush; and 3=normal blush, reflecting no or minimal, moderate, and normal myocardial perfusion
Outcomes at one year by treatment group, aspiration vs no aspiration, in TAPAS
End point Stenting with predilatation, n=536 (%) Aspiration before stenting, n=535 (%) p
Death 7.9 4.2 0.040
Death/nonfatal reinfarction 11.6 6.7 0.016

Dr William W O'Neill (University of Miami, FL), a comoderator for the late-breaking trials session that featured TAPAS, called it the first major trial in 15 years "to show that mortality is changed by an adjunctive intervention."

Indeed, Zijlstra and others appear satisfied that prestent thrombus aspiration is worth doing in the setting of acute STEMI, even though the TAPAS primary end point was defined in terms of myocardial blush grade, not clinical outcomes. "I think it's beyond any reasonable doubt that aspiration improves myocardial reperfusion. And I think it's very reasonable and logical to assume that that will translate into clinical benefit. And our figures, in fact, support that," Zijlstra told heartwire . "I think there's enough evidence to suggest that it's better to take the clots out than to let them go distally."

He continued, "If you really want to have very solid and firm conclusions about mortality, then you have to enroll at least 5000 to 10 000 patients." But such a trial isn't necessary, he said. "I don't see the point in doing that, but maybe others will."

Also on board with prestent thrombus aspiration is Dr William D Knopf (St Joseph's Hospital of Atlanta, GA), who officiated at a media briefing on the TAPAS study. The thrombus aspiration procedure, he said, is "fairly easy" to perform and low risk when performed with caution. "I think this is an important adjunct to the treatment of acute MI. I see very little downside. The catheters are relatively inexpensive, and it doesn't take long to do this procedure." Based on TAPAS, which was a fairly large trial, he observed, prestent thrombus aspiration "is something that should be widespread for the treatment of acute MI."

Apparently among those who see a point to first doing a large randomized mortality trial is Dr David A Cox (Lehigh Valley Hospital and Health Network, Allentown PA), the discussant whose comments followed Zijlstra's TAPAS presentation. He predicted the trial would be "practice-changing." He said before TAPAS, it seemed to be widely viewed that thrombus aspiration should be reserved for especially large clots.

On the other hand, Cox observed, the trial has some limitations and is subject to other interpretations. For example, it was a single-center study conducted by experienced operators. "I would like to see this done in a multicenter trial," he said, reiterating also that TAPAS wasn't powered to show differences in clinical outcomes. Also, many interventionalists believe that direct stenting--which in TAPAS was done exclusively in the aspiration group--produces better results than stenting with predilatation, which was mandated in the control group. "That might explain the data right there."

TAPAS was partially supported by Medtronic. There were no other potential conflicts of interest to disclose, the authors observe in their published report. O'Neill reports modest ownership or partnership interest in Alexion and Proctor & Gamble. Cox reports receiving consulting fees or honoraria as well as having ownership or partnership interest in The Medicines Company.

  1. Svilaas T. Thrombus aspiration during coronary angioplasty for acute myocardial Infarction. American College of Cardiology 2008 Scientific Sessions/i2 Summit-SCAI Annual Meeting; March 30, 2008; Chicago, IL.

  2. Svilaas T, Vlaar PJ, van der Horst I, et al. Thrombus aspiration during primary percutaneous coronary intervention. N Engl J Med 2008; 358: 557-567. Abstract

 

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