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Objective: The aim of this study was to determine how many pre-operative ischaemic events occurring within a specific timeframe before carotid endarterectomy (CEA) are needed to increase the peri-operative 30 day risk of stroke or death.

Methods: This was a secondary exploratory analysis based on pooled data from three observational studies sourced from a single centre. Patients with recently symptomatic conventional ≥ 50% carotid stenosis were included. The principal analysis was limited to patients presenting with stroke or transient ischaemic attack (TIA). The primary outcome was 30 day risk of peri-operative stroke or death. Whether one, two, three, or four or more ipsilateral pre-operative ischaemic events within three, seven, 14, or 30 days before CEA were associated with the primary outcome was assessed.

Results: The study included 382 patients who underwent CEA with symptomatic conventional ≥ 50% carotid stenosis with stroke or TIA as the presenting event. Mean patient age ± standard deviation was 72 ± 7 years, 117 (30.6%) were female, and 5% were treated with dual antiplatelet therapy. The primary outcome occurred in 21 patients (5.5%). Two or more events within 7 days before CEA was the most discriminative definition of repeated events, with a 14.3% (8/56) risk of the primary outcome. Those who fell outside this definition of two or more events within seven days before CEA had a 4.0% (13/326; p = .006) risk of experiencing the primary outcome (adjusted odds ratio 4.1, 95% confidence interval 1.6 – 10.5). Several alternative definitions were assessed, but patients with two or more events within seven days before CEA and negative for these alternatives still had a > 10% risk of the primary outcome.

Conclusion: Two or more ipsilateral ischaemic events within seven days before CEA is associated with an increased risk of peri-operative stroke or death in cases with symptomatic conventional ≥ 50% carotid stenosis and TIA or stroke as the presenting event. Studies assessing whether delayed or immediate CEA is preferable for this patient group are warranted.