Use of Antithrombotics Instead of Stents Appears Safe, Reduces Thrombus Burden in Subset of ACS Patients: EROSION

A small proof-of-concept study suggests that ACS patients with plaque erosion identified on intravascular optical coherence tomography (OCT) can be treated with antithrombotic therapy rather than undergoing PCI.

For patients with identified plaque erosion, instead of the more common plaque rupture, dual antiplatelet therapy with ticagrelor (Brilinta, AstraZeneca) and aspirin, among other antithrombotic therapies, significantly reduced thrombus burden and improved the minimal flow area in the affected vessel without an increased risk of recurrent ischemic events at 1 month.

Still, despite the positive findings, which were presented today at the European Society of Cardiology Congress 2016 in Rome, Italy, and published simultaneously in the European Heart Journal, lead researcher Ik-Kyung Jang, MD, PhD (Massachusetts General Hospital, Boston, MA), said the field is still in the early stages and future studies will be needed to determine the long-term outcomes of antithrombotic therapy in ACS patients with plaque erosion.

In this pilot study of ACS patients treated with antithrombotic therapy, one subject died at 30 days as the result of gastrointestinal bleeding, while another patient did not show any improvement in coronary stenosis and underwent PCI at the discretion of the consulting cardiologist.

Speaking with the media, Jang said there are multiple pathologies underlying thrombotic coronary occlusions responsible for STEMI. The more common pathology is the rupture of a fibrous cap overlying a lipid-rich atherosclerotic plaque, with the obstruction caused in part by the plaque entering into the arterial lumen. However, plaque erosion is another cause of luminal thrombosis in which there is an abundance of surface smooth muscle cells and inflammation, but no evident disruption of the fibrous cap. Compared with plaque rupture, patients with plaque erosion have preserved vascular integrity, a larger lumen, and a platelet-rich thrombus.

Plaque erosion is not nearly as well characterized in ACS patients but with the introduction of OCT, investigators have used the imaging modality to identify nonobstructive lesions that might be amenable to antiplatelet therapy rather than PCI, thereby avoiding the potential early and late complications related to the stent.

“The distinct morphological differences made us think that, maybe, the approach to patients with plaque erosion should be different in this era of individualized, personalized therapy,” said Jang.

To TCTMD, Andreas Baumbach, MD (Spire Bristol Hospital, Bristol, England), who chaired the ESC press conference, said the concept behind EROSION and the use of OCT is excellent, pointing out that it confirms what interventional cardiologists already know: that there is no need to stent every ACS patient. EROSION also goes beyond the TROFI study, an imaging trial investigating the effect of thrombus aspiration in STEMI patients, as well as what is currently done in clinical practice.

“Let’s say we do thrombus aspiration in some patients, or we put the wire through and we realize that the majority of the problem is thrombus and not plaque—not a reduction in the lumen,” said Baumbach. “There are cases in young patients, in young women in particular, where we have left them alone. We have done that it in clinical practice with good success. What this study adds is another tool beyond the angiogram, which is not as precise and sophisticated as doing it with OCT, to help us identify the real plaque erosion patients.”

Slow Erosion vs Massive Fissure: Different Treatment?

For EROSION, investigators screened 492 patients undergoing emergent coronary catheterization for ACS and performed OCT in 458 individuals. Among them, there were 405 evaluable culprit lesions, with identifiable plaque erosion present in 103 patients. In total, 60 patients were enrolled into the pilot study, and complete 1-month follow-up was available in 55 patients.

Regarding treatment for ACS caused by plaque erosion, patients received aspirin, ticagrelor, and unfractionated heparin prior to coronary catheterization and more than 80% underwent thrombectomy, which was allowed at the discretion of the treating cardiologist. Approximately two-thirds of patients were also treated with glycoprotein IIb/IIIa inhibitors. Following OCT, unfractionated heparin or low-molecular-weight heparin was prescribed for 72 hours and dual antiplatelet therapy with aspirin and ticagrelor was continued.

Median thrombus volume declined from 3.7 mm³ at baseline to 0.2 mm³ at 30 days (P < 0.001). Similarly, there were improvements in other measures of the luminal thrombus, including thrombus burden, mean thrombus area, and thrombus score. The minimal flow area in the culprit vessel improved from a median of 1.7 mm² to 2.1 mm² at 30 days (P = 0.002). Of the 60 patients included in the study, 47 patients met the study’s primary endpoint—defined as a more than 50% change in thrombus volume—and 22 patients had no residual thrombus at 30 days.

To TCTMD, Baumbach noted the study hasn’t yet shown that identifying these patients, and subsequently treating them with antithrombotic therapy over PCI, results into better clinical outcomes, although he acknowledged small, proof-of-concept studies such as this are not designed to provide such answers. Regarding the one patient death from gastrointestinal bleeding, Baumbach said medical therapy, although not as invasive as PCI, also carries a degree of risk that must be balanced when considering treatment options.

Patrick Serruys, MD, PhD (Erasmus Medical Center, Rotterdam, the Netherlands), who was not involved in the study, said the high resolution of OCT makes thrombus not associated with rupture or fissure potentially detectable, and he added that treatment with a purely antithrombotic approach is possible. However, there are a number of limitations with the study, not the least of which is that this is still very early days with OCT and using it to differentially treat ACS patients based on plaque characterization may be a step to far.

Commenting on the study during the hotline session, Serruys said it will be important to show how to reduce the risk of recurrent ACS with antithrombotic therapy beyond 30 days. He noted that the residual minimal lumen diameter of 1.54 mm at 30 days could “theoretically be flow limiting, at least in a noninfarcted areas.”

For his part, Jang said the researchers are continuing to follow patients and currently have 1-year clinical and OCT data on 33 patients. Although the numbers are small, none of these patients have experienced a recurrent ACS in follow-up, he reported.