Use of a novel mesh-covered stent reduces the risks of thrombotic complications and compromised reperfusion in STEMI patients with a large thrombus burden, according to an analysis of the MASTER trial published online October 29, 2014, ahead of print in the American Journal of Cardiology.

For the main trial, 433 STEMI patients undergoing primary PCI were randomized to implantation with the MGuard stent (InspireMD; Tel Aviv, Israel; n = 217)—a BMS with a micronet mesh covering designed to trap and exclude friable thrombotic and atheromatous material—or commercially available DES or BMS (n = 216). All patients underwent predilatation. Use of MGuard resulted in superior rates of complete ST-segment resolution (primary endpoint) and TIMI 3 flow, with no differences in adverse events at 30 days.

For the current analysis, investigators led by Ricardo A. Costa, MD, PhD, of the Institute Dante Pazzanese of Cardiology (São Paulo, Brazil), looked at the 383 patients (88.5%) with angiographically evident thrombus, categorizing the burden as large (47 ± 18 mm²) or small (22 ± 6 mm²) depending on whether it was above or below the median of 30.5 mm².  

Thrombus Burden Linked to Procedural Outcome

There were no clinical differences between the large and small thrombus groups, except for more prior MI in the former. However, patients with a large thrombus burden had longer and more complex lesions and a larger reference vessel diameter. Manual aspiration was more often performed in the large thrombus group, which was treated with longer and larger diameter stents. 

Intraprocedural thrombotic complications, such as new thrombus, abrupt vessel closure, no reflow, and distal embolization, occurred more frequently in the large compared with the small thrombus group (30.6% vs 15.9%; P = .0007). In addition, the stenting of lesions with a large vs small thrombus burden was associated with lower rates of final TIMI flow grade 3 (81% vs 91%; P = .004) and reduced angiographic success (80% vs 91%; P = .003).

However, at 30 days there were no differences in rates of MACE (cardiac death, reinfarction, or ischemia-driven TLR), cardiac death, or definite or probable stent thrombosis between patients with a large vs small thrombus burden. 

For Large Thrombus, MGuard Improves Reperfusion

Baseline clinical and angiographic characteristics were similar between the MGuard and control stent groups. In the large thrombus group, patients treated with MGuard tended to develop less slow flow or no reflow, were more likely to have TIMI 3 flow, and had better corrected TIMI frame counts and more angiographic success than those implanted with a conventional stent (table 1). 

In the small thrombus group, MGuard was associated with a trend toward less distal embolization compared with control stents despite greater use of multiple MGuard devices (1% vs 7%; P = .06) but no differences in other angiographic parameters.

At 30 days, MACE rates were similar between the MGuard and control groups regardless of whether they had a large (3.3% and 2.9%; P = .89) or small (1.0% and 1.1%; P = .97) thrombus burden.

The authors say that compared with standard stents, use of a mesh-covered device “improved reperfusion success, with the most profound improvements in angiographic outcomes among patients with large thrombus burden.”  

Best Way to Treat Thrombus-Bearing Lesions Uncertain  

“The optimal approach for thrombus-containing lesions is still evolving,” the researchers point out, noting that recent studies have favored use of potent pharmacological agents during PCI. In addition, several mechanical devices designed to prevent distal embolization have been tested, and although manual aspiration is often used in STEMI, recent research has shown no reduction in infarct size or mortality with the strategy. In the current trial, the MGuard stent improved angiographic outcomes despite use of manual thrombectomy before stenting in about two-thirds of cases.

Dr. Costa and colleagues note that they used a QCA-based method of measuring thrombus size that is “more objective and as a continuous variable, may provide better statistical power than the categorical TIMI thrombus scale.” 

Nonetheless, they admit, both methods share the same limitation: that recanalization of the infarct artery may result in some degree of distal embolization or local thrombus dispersion or removal prior to assessment, thereby reducing the thrombus burden at the lesion site.

In a recent press release, InspireMD reported that development of a DES with micronet technology is under way and is expected to be submitted for CE mark approval in the second half of 2015.  

Note: Several coauthors are faculty members of the Cardiovascular Research Foundation, which owns and operates TCTMD.
 

Source:

Costa RA, Abizaid A, Lotan C, et al. Impact of thrombus burden on outcomes after standard versus mesh-covered stents in acute myocardial infarction (from the MASTER trial). Am J Cardiol. 2014;Epub ahead of print.

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