Why is this study important?

It is likely that every interventional cardiologist has encountered STEMI patients in whom symptoms have resolved and TIMI grade 3 flow is present in the infarct-related artery (IRA) at the time of angiography. If the STEMI was caused by plaque rupture or erosion but the IRA isn’t obstructed, the benefit of stent placement is unknown. Optical coherence tomography (OCT) can help define when lesions are non-obstructive or threatening obstruction. EROSION III tested the value of OCT in determining when stents should be placed, using defined OCT characteristics to guide that decision, in non-obstructive STEMI lesions.

Should I change my practice because of these findings?  

No. The data are thought-provoking and give some reassurance that foregoing stents in some acute MI patients with non-obstructive disease may be possible, but this study was designed to test whether the designated OCT findings could be found often enough to have an impact on use of stents. The study was not designed to test the impact of this treatment plan on clinical outcomes. The clinical value of this approach remains unknown.

What question was this study supposed to answer?

The EROSION III investigators set out to test the primary outcome of rate of stent implantation during primary PCI in 246 patients randomized to angiography-guided vs. angiography plus OCT-guided treatment: stents were not used if OCT showed erosion, spontaneous coronary artery dissection, or plaque rupture without associated dissection. They hypothesized that OCT guidance compared to angiographic guidance only would be associated with a lower stent rate in STEMI patients with non-obstructive stenosis (defined as diameter stenosis ≤ 70% with TIMI grade 3 flow). The secondary outcome was major adverse cardiac events (MACE) at 1 month and 1 year; this would allow insight into signals of harm or clinical benefit from performing the OCT or from withholding stents.

What did the study show?

The primary endpoint (patient-level rate of stent implantation) was higher in the angiography-guided group vs. OCT-guided group (58.8% vs. 43.8%, p=0.024), representing a 15% reduction in stent implantation in the OCT-guided group. Stent post-dilation was more common in the OCT-guided group (89.8% vs. 74.6%, p=0.04), although this did not produce any clear benefits at 12 months. The investigators found no difference in the secondary outcome of MACE between the two groups at 30 days or at 1 year (less than 3% MACE in both arms).

How good was the approach/methodology?

This study was limited by small sample size and was underpowered for assessment of clinical outcomes (i.e., MACE). The patients in the study were relatively young (average age of 55 years) and 90% were male. Importantly, previous trials have shown potential harm is associated with routine coronary thrombectomy, so most patients with STEMI do not receive thrombectomy prior to stenting today. More than 90% of patients in EROSION III were treated with routine thrombectomy. Thus, adoption of this approach would require demonstration of sufficient clinical benefit to offset any thrombectomy-related harm. With a relatively modest (though statistically significant) 15% reduction in stents and no signal of clinical benefit, a cost-benefit analysis of this approach, which requires additional time and relatively expensive equipment, will be of interest.

All editors: Allison Dupont, MD, FSCAI; Kirk Garratt, MD, MSc, MSCAI; and David A. Cox, MD, MSCAI