Two New Studies Strengthen Case Against Thrombus Aspiration in STEMI

Bolstering results from other recent research, 2 studies have failed to show any clinical benefit from aspiration thrombectomy in STEMI patients undergoing primary PCI, one an observational analysis in an all-comers population and the other a randomized trial in patients presenting later than 12 hours after symptom onset.

The findings are “consistent with the thinking within thrombectomy, they’re consistent with the large randomized trials TASTE and TOTAL, and they’re consistent with the current updated STEMI guidelines from the ACC/AHA,” commented Sanjit Jolly, MD, MSc, of McMaster University (Hamilton, Canada).

Nevertheless, thrombus aspiration will retain a role as a rescue therapy for patients in whom a high thrombus burden continues to impede blood flow after balloon inflation, Jolly told TCTMD. He noted that there are no randomized data to support the bailout approach, but there are studies suggesting that achieving TIMI 3 flow at the end of the procedure is associated with better patient outcomes. Thus, he said, operators will continue to err on the side of removing the thrombus in these types of patients.

The new studies, now available online, will be published in the January 25, 2016, issue of JACC: Cardiovascular Interventions.

Tide Turns Against Thrombectomy

Early trials of aspiration thrombectomy that were underpowered for studying effects on MACE yielded promising results, and the TAPAS trial showed that manual aspiration thrombectomy lowered mortality at 1 year. A 2013 meta-analysis supported that finding.

Larger trials coming after TAPAS, however, were not as favorable. INFUSE-AMI, TASTE, and TOTAL all failed to show a benefit for routinely adding thrombectomy to primary PCI. In TOTAL, thrombectomy led to a small but significant increase in the risk of stroke.

Those more recent findings led to a downgrade for aspiration thrombectomy in an October update to the STEMI guidelines from the American College of Cardiology, American Heart Association, and Society for Cardiovascular Angiography and Interventions. There is now a class III recommendation (indicating no benefit) against routine use of the technique and a class IIb recommendation stating that the usefulness of selective or bailout thrombectomy is not well established.

Selective Use Not Beneficial in All-Comers

The first of the new analyses tackles the impact of selective use using data from a UK PCI registry from the British Cardiovascular Intervention Society and the National Institute for Cardiovascular Outcomes Research. The study, by Alex Sirker, MBBChir, of University College London Hospitals, and colleagues, includes 98,176 patients who underwent primary PCI in England or Wales between 2006 and 2013.

After propensity-score matching, there was no difference in 30-day mortality (primary endpoint) between those who underwent thrombectomy and those who did not (P = .47), with a similar finding at 1 year (P = .18).

Those results were consistent in the subgroup of patients who were treated with manual aspiration devices. The use of complex mechanical thrombectomy devices, however, was associated with a higher risk of 1-year mortality compared with no thrombectomy (P = .017).

The study “provides further evidence against routine aspiration thrombectomy use during primary PCI,” Dharam Kumbhani, MD, SM, of the University of Texas Southwestern Medical Center (Dallas, TX), and Anthony Bavry, MD, MPH, of the University of Florida (Gainesville, FL), write in an accompanying editorial.

“Thrombus removal remains an intuitively valid concept,” they say. “However, thrombus removal is more complex than initially appreciated. Future studies will need to similarly rigorously evaluate the role of selective thrombectomy versus no thrombectomy, determine more effective thrombectomy devices, and better discriminate appropriate lesions to which this therapy can be applied.”

Results No Better in Subacute STEMI

In the second study, which was originally presented at TCT 2015, Steffen Desch, MD, of the University of Lübeck Heart Center (Lübeck, Germany), looked at whether thrombectomy could have any benefits in STEMI patients presenting 12 to 48 hours after symptom onset. The researchers randomized 152 patients to PCI with or without manual thrombus aspiration with the 6-Fr Export AP catheter (Medtronic) at a mean of 28 hours after symptom onset.

Cardiac MRI performed 1 to 4 days after randomization showed that the mean extent of microvascular obstruction (primary endpoint) was 2.5% of LV mass in the thrombectomy group and 3.1% in the control group (P = .47). That equivalence was consistent across subgroups.

There also were no differences in infarct size, myocardial salvage index, LV volumes or ejection fraction, or angiographic and clinical endpoints.

“Treatment modalities other than routine thrombus aspiration are needed to further reduce microvascular injury in patients with STEMI,” the authors conclude.

Aspiration Thrombectomy Not Going Away

Echoing Jolly’s assessment, James Blankenship, MD, MHCM, of Geisinger Medical Center (Danville, PA), says in an editorial accompanying the study by Desch’s team that operators will continue to use thrombectomy in select cases despite the accumulation of evidence suggesting a lack of clinical benefit.

Inspired by the term “oculostenotic reflex” coined by Eric Topol to refer to the temptation to perform angioplasty on any significant residual stenosis after thrombolysis, Blankenship says operators will be driven by the “oculothrombotic reflex” to aspirate thrombi, “particularly when they sometimes extract magnificent red thrombi approaching the size of night crawlers.”

Other factors contributing to continued use are the fact that removing the thrombus makes primary PCI easier, the potential for thrombectomy to be useful in select cases, and evidence from some older trials that the technique could be beneficial, he says.

“New technologies such as novel thrombus retrieval devices or the MGuard mesh stent (InspireMD) may replace [coronary thrombus aspiration] in the future, but for now it seems clear that interventionists will retain [aspiration] catheters in their toolkits,” he concludes.

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Sources: 
1. Sirker A, Mamas M, Kwok CS, et al. Outcomes from selective use of thrombectomy in patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction: an analysis of the British Cardiovascular Intervention Society/National Institute for Cardiovascular Outcomes Research (BCIS-NICOR) registry, 2006-2013. J Am Coll Cardiol Intv. 2016;9:126-134.
2. Desch S, Stiermaier T, de Waha S, et al. Thrombus aspiration in patients with ST-segment elevation myocardial infarction presenting late after symptom onset. J Am Coll Cardiol Intv. 2016;9:113-122.
3. Kumbhani DJ, Bavry AA. The risk and fall of aspiration thrombectomy [editorial]. J Am Coll Cardiol Intv. 2016;9:135-137.
4. Blankenship JC. The oculothrombotic reflex: why we will never stop aspirating coronary thrombi [editorial]. J Am Coll Cardiol Intv. 2016;9:123-125.

Related Stories:

• Guideline Update Boosts Nonculprit PCI, Knocks Down Aspiration Thrombectomy
• Another Strike Against Thrombectomy in 1-Year TASTE Results
• TOTAL: Use of Routine Thrombectomy in Primary PCI Takes Another Blow