Dual antiplatelet therapy analysis inconclusive in DISCO registry for spontaneous coronary artery dissection

This commentary refers to ‘Antiplatelet therapy in patients with conservatively managed spontaneous coronary artery dissection from the multicentre DISCO registry’, by E. Cerrato et al., https://doi.org/10.1093/eurheartj/ehab372 and the discussion piece ‘DISCO study suggests that less is more regarding antiplatelet therapy in spontaneous coronary artery dissection’, by F. Giacobbe et al., https://doi.org/10.1093/eurheartj/ehac215. We read with interest the results of the DISCO study comparing dual antiplatelet therapy (DAPT) to single antiplatelet therapy (SAPT) in conservatively managed patients with spontaneous coronary artery dissection (SCAD).1 There is a lack of randomized data on antithrombotic therapy leading to variability in clinical practice for acute management of SCAD patients. Thus, we applaud the efforts of the authors in their observational registry; however, there are critical study design limitations that undermine their conclusion. This study was a retrospective analysis of 199 SCAD patients who were initially managed conservatively. In-hospital and 12-month outcomes of patients were compared between those who received DAPT or SAPT at the time of hospital discharge. There were no data regarding antiplatelet regimen prior to SCAD diagnosis or during the hospital stay. Over one of three DAPT patients received ticagrelor or prasugrel, and almost all patients received DAPT for 12 months. The choice of antiplatelet therapy was at the discretion of the physicians, which is a major confounder as it is likely higher-risk patients would be discharged on DAPT, especially those who suffered adverse in-hospital events or worse anatomic features (e.g. poor TIMI flow, extensive dissections). They found a significantly higher rate of major adverse cardiac events (MACE) defined as the composite of death, non-fatal myocardial infarct, or unplanned revascularization in patients discharged on DAPT. However, 14 of 15 in-hospital MACE were due to unplanned revascularization with percutaneous coronary intervention (PCI), which unquestionably would have led to DAPT use on discharge. This would clearly lead to substantial systematic bias against the DAPT group. We believe that these patients should be excluded from the analysis. If that were the case, MACE rates for DAPT and SAPT groups would have been similar. It is impossible to tease out the confounding factors that drove treating physicians to prescribe DAPT vs. SAPT in a retrospective study. In the much larger Canadian SCAD Cohort Study that prospectively enrolled 750 patients, 67.4% were on DAPT at discharge and 28.2% at 1 year.2 The use of P2Y12 (predominantly clopidogrel) was not a predictor of worse in-hospital or follow-up outcomes when patients who underwent PCI were excluded. In our contemporary practice, clopidogrel is the preferred P2Y12 inhibitor for SCAD patients and the duration of DAPT is limited to 1–3 months for conservatively managed patients.3 The rationale is to minimize the potency of antithrombotic therapy that may exacerbate intramural haematoma, while offering inhibition of thrombus formation at ruptured intima and within the false lumen. Spontaneous healing of dissected arteries occurred in 95% of cases and within 30 days post-SCAD,4 thus, a longer duration of DAPT may not be required. Therefore, the DAPT strategy in the DISCO registry appeared too potent and prolonged. In summary, the non-randomized allocation and inclusion of patients who underwent in-hospital PCI resulted in major bias against the DAPT group for conservatively managed SCAD patients, rendering the findings inconclusive. We eagerly await the results of the BA-SCAD trial5 (NCT04850417) that includes randomized comparison of DAPT vs. SAPT, which will hopefully provide more definitive guidance on this important issue. Conflict of interest: None declared.

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