In patients with a high thrombus burden undergoing primary percutaneous coronary intervention (PCI), use of thrombectomy helps resolve ST elevation and improves reperfusion but does not reduce infarct size or provide longer-term clinical benefit, according to a study published in the December 2012 issue of JACC: Cardiovascular Interventions.

Data from the MUSTELA (MUltidevice thrombectomy in acute ST-Segment ELevation Acute myocardial infarction) trial were originally presented at the annual Transcatheter Cardiovascular Therapeutics scientific symposium in November 2011 in San Francisco, CA.

For the multicenter study, investigators led by Marco De Carlo, MD, PhD, of Azienda Ospedaliero-Universitaria Pisana (Pisa, Italy), randomized 208 STEMI patients to PCI with (n = 104) or without (n = 104) adjunctive thrombectomy. Thrombectomy was performed either manually (Export AP; Medtronic CardioVascular, Santa Rosa, CA; n = 50) or rheolytically (AngioJet Ultra; Possis Medical, Minneapolis, MN; n = 54).

No thrombectomy complications were seen. The procedure was associated with greater likelihood of complete ST elevation resolution, the primary endpoint, as well as final myocardial blush grade of 3. There also was a trend toward final TIMI flow grade of 3 with thrombectomy (table 1).

Table 1. Procedural Results

At 3 months, late gadolinium-enhanced MRI, performed in about three-quarters of both groups, showed similar infarct size and transmurality but a lower prevalence of microvascular obstruction and a higher rate of inhomogeneous myocardial scar (islands of viable myocardium covering > 5% of scar) in the thrombectomy arm (table 2).

Table 2. MRI Results at 3 Months

^a Percentage of LV mass.
^b Percentage of LV segments.

LVEF, end-diastolic volume, and stroke volume were similar between the groups.

In a subanalysis of the thrombectomy cohort, complete thrombus aspiration was more common with rheolytic than with manual catheters (94.4% vs. 78.0%; P = 0.02). The difference had no impact on the primary endpoint, although use of the rheolytic device was associated with a trend toward smaller infarct size at 3 months (17.5 ± 9.6% vs. 21.3 ± 11.3%; P = 0.10).

By 1 year, 5 patients in the thrombectomy group died due to cardiac causes, 2 suffered reinfarction, and 1 underwent TVR. In the PCI-only group, 4 died because of cardiac causes, 2 experienced recurrent MI, and 1 received TVR. Overall there was no difference between the thrombectomy and PCI-only groups in freedom from MACE (composite of death, reinfarction, and TVR; 91.4 ± 2.8% and 90.2 ± 2.9% respectively; P = 0.97).

A Mixed Message

Sanjit Jolly, MD, of McMaster University (Hamilton, Canada), told TCTMD in a telephone interview, “This is the same message we’ve seen before in several small trials,” namely that thrombectomy does not reduce the surrogate endpoint of infarct size regardless of how it is measured. But other surrogate measures were encouraging, he noted, and the single-center TAPAS trial showed a clinical benefit.

“These trials were initial steps, but it’s important to take the evidence to the next level,” Dr. Jolly said. “That’s why we’re conducting a large-scale randomized trial called TOTAL, to see if we can reproduce those findings in terms of improvement in hard clinical outcomes.”

Both TOTAL and the Swedish randomized TASTE trial, which is enrolling more than 5,000 patients, aim to determine whether manual thrombectomy as a routine strategy can improve clinical outcomes, he said, adding that results from TOTAL should be available within 6 months to 1 year.

A Case for Rheolytic Thrombectomy?

In an e-mail communication with TCTMD, David Antoniucci, MD, of Careggi Hospital (Florence, Italy), suggested that the most convincing data will come from trials that not only have hard clinical endpoints but also use the same types of thrombectomy, stenting, and adjunctive pharmacotherapy in both randomized arms.

This was not the case in TAPAS or MUSTELA, he pointed out. “In the latter, 2 different thrombus-removal devices were used in a nonrandomized fashion, favoring the control arm, since manual aspiration is completely ineffective in more than 30% of cases, and also, even if effective in retrieving macrodebris, invariably leaves a large residual [amount of] thrombus, as shown by OCT.”

Rheolytic thrombectomy is more effective and more predictable in removing thrombus, as shown by the JETSTENT and SMART trials, he added. Moreover, Dr. Antoniucci said, in the current study “the imbalance in [baseline] TIMI flow grade between the groups favored the control arm, since intervention in an already open artery with normal flow may have little or no impact on myocardial salvage.”

However, Dr. Jolly noted, a recent US registry study showed that less than 1% of STEMI patients received rheolytic thrombectomy, suggesting that clinicians are reluctant to use an expensive procedure that has little trial data to support a clinical benefit.

Commenting that current STEMI guidelines back manual aspiration as a “reasonable” strategy, he agreed with the authors that it is most appropriate in patients with a large thrombus burden.

Study Details

Baseline clinical characteristics were similar between the groups. In particular, the rate of anterior wall STEMI was balanced due to stratification before randomization. The PCI-alone group showed a trend toward a shorter pain-to-balloon time (P = 0.07) and was more than 4 times more likely to have baseline grade 3 TIMI flow (16.3% vs. 3.8%; P = 0.002).

 

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Source:
De Carlo M, Aquaro GD, Palmieri C, et al. A prospective randomized trial of thrombectomy versus no thrombectomy in patients with ST-segment elevation myocardial infarction and thrombus-rich lesions: MUSTELA (MUltidevice thrombectomy in acute ST-Segment ELevation Acute myocardial infarction) trial. J Am Coll Cardiol Intv. 2012;5:1223-1230.

 

 

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• Thrombectomy Results Underwhelming in AMI Patients