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Performing manual aspiration thrombectomy during primary percutaneous coronary intervention (PCI) reduces major adverse cardiac events (MACE) including mortality, but the same benefit is not seen with mechanical thrombectomy, according to a large meta-analysis scheduled to be published online May 7, 2013, ahead of print in the Journal of the American College of Cardiology.

Investigators led by Dharam J. Kumbhani, MD, SM, of the University of Texas Southwestern Medical Center (Dallas, TX), analyzed 25 trials in which 5,534 patients were randomized within 12 hours of acute MI to primary PCI with or without adjunctive thrombectomy. In 18 aspiration thrombectomy trials (n = 3,936), 1,944 patients underwent the adjunctive procedure, while in 7 mechanical thrombectomy trials (n = 1,598), 779 patients received the add-on procedure.

Aspiration Thrombectomy Gets the Nod

Aspiration thrombectomy improved immediate myocardial perfusion, achieving higher rates of TIMI 3 blush grade (63.6% vs. 48.5%) and ST-segment resolution (55.8% vs. 44.3%; both P < 0.0001) compared with PCI alone. However, there was a high degree of heterogeneity among the studies for both endpoints.

At a mean follow-up of 35.9 days, no difference was seen between the aspiration and PCI-only groups for final infarct size (17.1% vs. 17.3%; P = 0.64). Final ejection fraction values were also similar between the arms (53.0% vs. 52.8%; P = 0.32).

At a weighted mean follow-up of 5.9 months, risks of all-cause mortality (primary endpoint) and MACE (composite of death, reinfarction, and TVR) were lower with aspiration vs. PCI alone. The odds of reinfarction and stroke, meanwhile, were similar between the treatment arms, while there was a trend toward reduced TVR with aspiration (table 1).

Table 1. Six-Month Clinical Outcomes: Aspiration Thrombectomy vs. Primary PCI Alone

 
In a sensitivity analysis that excluded the TAPAS trial, which showed a 1-year mortality benefit for aspiration thrombectomy but according to the paper also received extensive criticism, aspiration’s mortality advantage was lost (P = 0.42). 

No Benefit for Mechanical Thrombectomy

In the mechanical thrombectomy trials, the adjunctive procedure did not improve TIMI 3 blush grade compared with PCI alone (48.8% vs. 49.5%; P = 0.48) but increased the incidence of ST-segment resolution (74.9% vs. 63.7%; P = 0.007).

At a mean follow-up of 33.2 days, final infarct size was similar between the thrombectomy and PCI-only arms (12.7% vs. 13.3%; P = 0.47). Final ejection fraction could not be analyzed due to insufficient data.

At a weighted mean follow-up of 6.2 months, no difference was seen between mechanical thrombectomy and PCI alone for mortality, MACE, or other individual endpoints, while a trend emerged for increased stroke with thrombectomy (table 2).

Table 2. Six-Month Clinical Outcomes: Mechanical Thrombectomy vs. Primary PCI Alone

According to the authors, the meta-analysis supports the routine use of manual aspiration in STEMI patients undergoing primary PCI, and the class IIa recommendation in the current American College of Cardiology/American Heart Association guidelines appears justified. On the other hand, the data fail to back use of mechanical thrombectomy, they assert.

In an accompanying editorial, Prakash Balan, MD, and H. Vernon Anderson, MD, both of the University of Texas Health Science Center (Houston, TX), agree, writing that the study provides “solid if indirect evidence” for the usefulness of aspiration thrombectomy in primary PCI. They add that “like all infarct treatments, [it] should be applied as fast as possible, ideally within 120 minutes of ischemic time.” 

A Lead-in to More Definitive Trials

The current study is the latest in a series of meta-analyses of thrombectomy trials over the past few years, with each adding only a little incremental data, Sanjit Jolly, MD, of McMaster University (Hamilton, Canada), told TCTMD in a telephone interview.

In this case, he said, the investigators likely wanted to integrate the results of the recent INFUSE-AMI trial—which found no reduction in infarct size at 30 days with aspiration thrombectomy—to see if the procedure still showed a benefit. But Dr. Jolly cautioned that since the underlying trials are powered only for surrogate endpoints, no definitive clinical conclusions can be drawn from the meta-analysis.

To Dr. Jolly, the study’s main virtue lies in building anticipation for results from 2 large randomized trials of aspiration thrombectomy, TOTAL and TASTE, each with about 7,000 patients and thus powered for hard clinical endpoints. Initial data are expected to be reported within 6 to 9 months, he said, adding that if a benefit is confirmed, “that’s when both guidelines and practice will be modified.”

Even if the trials are not positive overall, he noted, benefits may yet be seen in prespecified subgroups, such as patients with a high thrombus burden.

Part of aspiration thrombectomy’s problem is that it is not effective in certain settings, Dr. Jolly observed. For example, the current generation of manual catheters may not remove thrombus that is large or disseminated along the sides of the vessel, and the devices often cannot negotiate tortuous vessels. But newer catheters that overcome such limitations are on the horizon, he reported.

Procedural Benefit May Justify Use 

In a telephone interview with TCTMD, Jeffrey W. Moses, MD, of Columbia University Medical Center/Weill Cornell Medical Center (New York, NY), said the current study reinforces the view that the “weight of evidence is tilted toward benefit [for aspiration thrombectomy], but it also keeps the controversy going. It’s not the final answer.” He noted that in the sensitivity analysis, removal of the TAPAS trial—whose finding of a survival benefit he called “probably an anomaly”—neutralized thrombectomy’s mortality advantage.

But even if reductions in hard clinical endpoints remain uncertain, he contended, aspiration thrombectomy does no harm and carries enough procedural advantages, such as the ability to determine lesion length and better size a stent, to warrant routine use.

On the other hand, Dr. Moses dismissed mechanical thrombectomy as rarely used in the coronaries, adding that it is “very disruptive [of clot] and the stroke signal is disturbing.”

Dr. Jolly simply noted that data evaluating the procedure are limited.

 

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Sources:
1. Kumbhani DJ, Bavry AA, Desai MY, et al. Role of aspiration and mechanical thrombectomy in patients with acute myocardial infarction undergoing primary angioplasty: An updated meta-analysis of randomized trials. J Am Coll Cardiol. 2013;Epub ahead of print.

2. Balan P, Anderson HV. Aspiration thrombectomy: It’s about time. J Am Coll Cardiol. 2013;Epub ahead of print.

 

• Dr. Moses reports no relevant conflicts of interest.

 

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