Antiplatelet Therapy in Ischemic Stroke with Hemorrhagic Transformation

Classification of Hemorrhagic Transformation (HT)

When to Start (or Restart) Antiplatelet Therapy

1. Hemorrhagic Infarction (HI-1, HI-2 - "petechial" HT)

• Antiplatelet therapy can be started within 24-48 hours in most cases
• The underlying stroke still requires secondary prevention
• A July 2026 multicenter study (JAHA, Hejazian et al.) found no statistically significant difference in HT exacerbation between same-day, early (<1 day), or late (>1 day) antiplatelet initiation after hemorrhagic infarction
• This study (n=748 patients) found median antiplatelet initiation after HI was 1 day [IQR 0-2]

2. Parenchymal Hematoma (PH-1, PH-2)

• Significantly greater caution required
• Median clinical practice: 3 days [IQR 1-5] after PH in the above study
• A 2023 dual-center study (Reale et al., J Clin Med) found major HT delayed antithrombotic start to a median 39 hours vs. 24 hours for no-HT patients; 22% of major HT patients received no antithrombotic therapy at 3 months
• AHA/ASA and most guidelines recommend imaging confirmation of stability and deferring initiation by 1-4 weeks for PH-2
• Importantly, prolonged delay after PH was associated with higher composite thromboembolic outcomes (20.7% vs. 3%, p=0.044 for late vs. early OAC in PH) - reinforcing that indefinite withholding is also harmful

Choice of Antiplatelet Agent

• Aspirin monotherapy (75-325 mg/day) is the standard first choice
• Dual antiplatelet therapy (DAPT, e.g., aspirin + clopidogrel) should generally be avoided in the setting of HT - the incremental hemorrhagic risk outweighs benefit unless there is a specific indication (e.g., minor stroke/TIA with high-risk features where DAPT was already established and HT is only petechial)
• If the patient was on DAPT prior to stroke, consider switching to monotherapy when restarting

Special Situations

Key Principles

1. Imaging is mandatory before restarting - repeat CT/MRI to confirm the type and stability of HT
2. The risk of NOT treating is real - withholding antiplatelet increases recurrent ischemic stroke risk; HT itself is often asymptomatic and does not negate stroke secondary prevention
3. HI ≠ PH - conflating them leads to either over-caution (undertreating HI) or under-caution (prematurely treating PH)
4. Individualize based on infarct size, etiology (cardioembolic > lacunar risk for HT), BP control, and reason antiplatelet was needed in the first place

Recent Evidence Summary

• Hejazian et al. 2026 (PMID 42396814): No significant difference in 30-day HT exacerbation with early vs. late antiplatelet after HI or PH; late OAC initiation after PH trended toward more thromboembolic events - supports not over-delaying treatment
• Reale et al. 2023 (PMID 37109108): Minor HT did not significantly delay antithrombotic start; major HT remains a clinical challenge with high untreated rates and modestly higher hemorrhagic recurrence
• Harrison's 2025: In stroke complicated by IE, antithrombotic therapy "requires careful consideration" given risk of converting hemorrhagic transformation to catastrophic bleeding

Bottom line: For petechial HT (HI-1/HI-2), restart aspirin within 24-48 hours. For parenchymal hematoma (PH-1), aim for 3-5 days with imaging confirmation. For PH-2, delay 1-4 weeks but do not indefinitely withhold - the thromboembolic risk of prolonged delay is real. Avoid DAPT in the acute HT period.