Direct stenting for STEMI: Does it really make a difference?

ST-elevation myocardial infarctions (MIs) are characterized by thrombotic occlusions precipitated by plaque rupture. The composition of aspirated thrombi includes a metabolically toxic brew of activated platelets, necrotic cells, lipid, and fibrin. Distal embolization of such material during percutaneous coronary intervention (PCI) is a major contributor to microvascular injury, resulting in persistent ST-segment changes, larger infarct size, hemodynamic instability, and death. Direct stenting (DS) without balloon predilatation may reduce vessel wall damage and distal embolization, potentially reducing the incidence of no-reflow, MI, and death. However, there are significant downsides to DS including: underestimation of true vessel size, failure to cross, nondilatable lesions, inadequate stent expansion, geographic miss, late stent malapposition, and restenosis. As a result, in practice DS has been reserved for simple lesions without angulation, calcification, or tortuosity. Studies of DS for both stable angina and STelevation MI have had mixed results. A meta-analysis of 24 randomized controlled trials of DS versus conventional stenting (CS) in PCI found that DS was associated with reduction in MI [odds ratio (OR) of 0.77; 95% CI 0.55–0.99, P1⁄4 0.04], driven by a reduction in periprocedural MI [1]. However, only three small randomized trials of DS in ST-segment elevation MI have been conducted, with conflicting results. Ozdemir et al. [2] found a benefit to DS in corrected TIMI frame count (cTFC) and TIMI 3 flow rates in a small trial of 50 patients. Loubeyre et al. [3] in 206 patients found no difference in cTFC or TIMI flow, but a benefit in ST-segment resolution (no ST-segment resolution in 20.2% versus 38.1% in DS versus CS, P1⁄4 0.01) and a composite endpoint of noor slow-reflow, electrocardiographic changes, and clinical outcome (11.7% vs. 26.9%, P1⁄4 0.01). In contrast, Gasior et al. [4] found in 217 patients no difference in TIMI flow, perfusion score, ST-segment resolution, or 5 year clinical outcome, but a higher risk of restenosis (30% vs. 16%, P1⁄4 0.024) with DS. It is with this background that Dziewierz et al. [5] examine the impact of DS on the outcome of STsegment MI patients from their EUROTRANSFER registry. From a population of 1,419 patients, DS was used in 276 (19.5%) of patients and was associated with greater rates of TIMI 3 flow (94.9% vs. 91.5%), lower rates of no-reflow (1.4% vs. 3.4%), higher rates of ST-segment resolution (86.2% vs. 76.3%), and a reduction in 1-year mortality (adjusted OR 0.45 (0.21– 0.99), P1⁄4 0.047). Their retrospective, nonrandomized analysis suggests that DS in primary PCI was associated with improved angiographic results and long-term survival. While a positive result, determining causation from an association is difficult from a retrospective study, particularly of an operator-selected technique. In this study, patients who received DS were significantly younger, more likely to have TIMI 2 or 3 flow at baseline (44% vs. 26%), and more likely to have received aspiration thrombectomy (26% vs. 8%) and preloaded clopidogrel (42% vs. 31%). They were less likely to have an left anterior descending infarct or multivessel disease. Any of these factors might have had a greater impact on outcome than accounted for in the authors’ statistical model. Propensity score adjustment typically does not sufficiently account for the impact of measured factors, compared with the more robust propensity matching approach. Propensity matching would have excluded much of the cohort because of the significant baseline differences between the two groups. Finally, unmeasured confounders in the form of operator, patient, and lesion characteristics almost certainly influenced the operators’ choice to use DS rather than CS.