By Will Boggs, MD
NEW YORK (Reuters Health) May 13 - In patients with acute myocardial infarction, thrombus aspiration before angioplasty reduced major adverse cardiac events (MACE), in a new meta-analysis.
Aspiration thrombectomy didn't affect final infarct size, however.
Still, said Dr. Dharam J. Kumbhani in an email to Reuters Health, "Based on our analysis, we believe that all patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI) should undergo aspiration thrombectomy prior to angioplasty/stenting."
Dr. Kumbhani, from the University of Texas Southwestern Medical Center in Dallas, and colleagues had shown in an earlier meta-analysis that aspiration thrombectomy devices improved myocardial reperfusion parameters and mortality, whereas mechanical thrombectomy devices appeared to increase the risk of death.
In light of additional studies and further follow-up on earlier trials, they performed an updated meta-analysis to determine the relative benefit of adjunctive aspiration and mechanical thrombectomy devices on clinical and surrogate markers of reperfusion as compared with conventional primary PCI alone in patients presenting with STEMI.
Their study included 25 trials with 5,534 patients. Overall, 1,944 patients underwent adjunctive aspiration thrombectomy, 779 underwent adjunctive mechanical thrombectomy, and 2,811 had conventional primary PCI alone.
Eighteen trials with 3,936 patients compared aspiration thrombectomy to conventional primary PCI. Aspiration thrombectomy was linked with significantly higher rates of TIMI 3 blush post-procedure (63.6% vs 48.5%; p<0.0001) and complete ST-segment resolution (55.8% vs 44.3%; p<0.0001). The two strategies did not differ in final infarct size or final ejection fraction, however.
During 5.9 months average follow-up, all-cause mortality (the primary endpoint) was significantly lower with aspiration thrombectomy vs PCI alone (2.7% vs 3.9%; p=0.049). The rate of the composite MACE outcome was also significantly lower after aspiration thrombectomy (10.8% vs 14.0%; p=0.0006).
Reinfarction and target vessel revascularization rates did not differ significantly between the two treatment arms, although they were numerically lower after aspiration thrombectomy.
Seven trials with 1,598 patients compared mechanical thrombectomy to conventional primary PCI. Significantly more patients had complete ST-segment resolution after mechanical thrombectomy (74.9% vs 63.7%; p=0.007). There was, however, no significant difference between the two approaches in TIMI 3 blush post-procedure, final infarct size, all-cause mortality rates, reinfarction, target vessel revascularization, all strokes, or the composite MACE outcome during 6.2 months of follow-up.
"The main message of this analysis is that manual aspiration thrombectomy appears to be safe and efficacious in improving clinical outcomes in patients with ST-elevation MI undergoing primary PCI and should be preferred over routine angioplasty/stenting or mechanical thrombectomy in these patients," Dr. Kumbhani said.
"Our analysis also suggests that routine use of mechanical thrombectomy is not indicated for ST-elevation MI patients undergoing primary PCI," Dr. Kumbhani said. "However, other studies indicate that there may be a role in arteries with extensive clot burden, especially if aspiration thrombectomy fails to provide satisfactory thrombus extraction."
But experts who weren't involved in the study told Reuters Health they're not ready to call for routine aspiration thrombectomy in this setting.
Dr. H. Vernon Anderson from the University of Texas Health Science Center in Houston, who coauthored an editorial published with the report, told Reuters Health in an email, "Aspiration thrombectomy cannot be recommended as a 'standard' in primary PCI at this time. Current guidelines give it only a Class IIa recommendation. That is, it may be helpful in the right settings."
"It would be appropriate to consider it in primary PCI patients when there is visible or suspected thrombus in the culprit (infarct) artery, and if that artery was 'larger,' generally more than 2-2.5 mm in diameter, and relatively 'straight,'" Dr. Anderson said.
"The major issue with primary PCI, in fact with all infarct treatments, is time until treatment," Dr. Anderson said. He added, "The goal of the entire system of care should be to minimize the ischemic time. While the data support the use of aspiration thrombectomy in primary PCI, the focus still remains on ischemic time. The goal has to be to employ aspiration thrombectomy as quickly as possible."
Dr. Gregg W. Stone, Director of Cardiovascular Research and Education at New York Presbyterian Hospital/Columbia University Medical Center, New York, commented by email to Reuters Health, "Whether aspiration thrombectomy reduces adverse cardiac events when used in patients undergoing stenting for heart attack is uncertain, and unfortunately this question is not definitively answered by this study. Despite the benefits of improved ST-segment resolution, without a reduction in infarct size, better survival is unlikely to occur."
"The favorable results in the meta-analysis are largely driven by one large single center study - TAPAS - which had a mortality benefit that is clearly too large to be true," Dr. Stone said. "Top large, simple trials powered for mortality are ongoing which will demonstrate whether the routine use of thrombus aspiration does indeed improve survival."
"For now, it is reasonable to use simple thrombus aspiration in cases of very large thrombus burden," Dr. Stone concluded. "There is little downside except the cost of the catheter. Active mechanical thrombectomy should be reserved for the rare case of refractory thrombosis."
Dr. Gohar Jamil from Tawam Hospital, Al Ain, United Arab Emirates has studied mechanical thrombectomy in the angioplasty setting. Dr. Jamil told Reuters Health, "Manual aspiration thrombectomy is quick, easily done, universally available and likely beneficial."
Dr. Jamil added, "Randomized control trials need to be done to look at the feasibility of manual aspiration thrombectomy without stenting in patients with excellent angiographic results post aspiration."
The new meta-analysis has been accepted for publication online in the Journal of the American College of Cardiology, but the journal has not announced the publication date.
J Am Coll Cardiol 2013.
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