P2Y12 inhibitor use predicts hematoma expansion in patients with intracerebral hemorrhage

Abstract

Objective

Hematoma expansion (HE) predicts disability and death after acute intracerebral hemorrhage (ICH). Aspirin and anticoagulants have been associated with HE. We tested the hypothesis that P2Y12 inhibitors predict subsequent HE in patients. We explored laboratory measures of P2Y12 inhibition and dual antiplatelet therapy with aspirin (DAPT).

Methods

We prospectively identified patients with ICH. Platelet activity was measured with the VerifyNow-P2Y12 assay. Hematoma volumes for initial and follow-up CTs were calculated using a validated semi-automated technique. HE was defined as the difference between hematoma volumes on the initial and follow-up CT scans. Nonparametric statistics were performed with Kruskal–Wallis H, and correction for multiple comparisons performed with Dunn's test.

Results

In 194 patients, 15 (7.7%) were known to take a P2Y12 inhibitor (clopidogrel in all but one). Patients taking a P2Y12 inhibitor had more HE compared to patients not taking a P2Y12 inhibitor (3.5 [1.2–11.9] vs. 0.1 [−0.8–1.4] mL, p = 0.004). Patients taking DAPT experienced the most HE (7.2 [2.6–13.8] vs. 0.0 [−1.0–1.1] mL, p = 0.04). The use of P2Y12 inhibitors was associated with less P2Y12 activity (178 [149–203] vs. 288 [246–319] P2Y12 reaction units, p = 0.005).

Interpretation

Patients taking a P2Y12 inhibitor had more HE and less P2Y12 activity. The effect was most pronounced in patients on DAPT, suggesting a synergistic effect of P2Y12 inhibitors and aspirin with respect to HE. Acute reversal of P2Y12 inhibitors in acute ICH requires further study.

Introduction

Intracerebral hemorrhage (ICH) is a deadly form of stroke and affects nearly 100,000 people in the United States yearly.¹ Hematoma expansion (HE), growth of the hematoma after the diagnostic computed tomography scan, is a modifiable risk factor for disability and death.^2,3 Treatments for ICH have focused on minimizing HE through aggressive blood pressure control^4,5 and promoting hemostasis.^6,7 However, the results of these interventions have been mixed.^4–7 There is an urgent need to better understand the mechanisms of HE to precisely identify patients and interventions.

Pre-ICH medications are associated with later HE. Anticoagulation is predictive of HE, and rapid reversal of anticoagulation reduces the likelihood of HE.^8,9 Antiplatelet medication use (e.g., aspirin) and reduced platelet activity prior to ICH are associated with HE and worse functional outcomes at follow-up, albeit less in magnitude compared to anticoagulation.^10–12 However, the effect of P2Y12 inhibitors and the impact of taking multiple antiplatelet medications on HE are not known.

We tested the hypothesis that P2Y12 inhibitors are associated with later HE in patients with ICH, and explored if the effect was modified by combined antiplatelet therapy (P2Y12 inhibitor and aspirin, DAPT). We further explored laboratory measures of P2Y12 activity and subsequent HE.

Methods Study population

We prospectively identified consecutive patients with ICH with a diagnostic CT scan. Baseline demographic data, past medical history data, and date and time of symptom onset were prospectively recorded. All patients were diagnosed by a board-certified neurologist. All diagnoses were confirmed by computed tomography (CT). ICH treatment followed AHA guidelines.¹³ Patients with ICH attributable to trauma, ruptured aneurysms, arteriovenous malformation rupture, vasculitis, other structural lesions, anticoagulant use, or those who presented more than 12 h after a clear time of symptom onset were excluded.¹⁴ Patients without a follow-up CT (e.g., technical inability or death) or who had surgery for hematoma evacuation were excluded.

Written informed consent to collect data and clinical outcomes was obtained from the patient or a legally authorized representative (LAR) in all cases, except when the patient died in hospital, or no LAR could be located for an incapacitated patient, in which case the IRB approved collection of data in a registry without consent.

Medication reconciliation

A pharmacist reviewed the medication history with the patient (if they were able), an LAR, and the electronic health record as part of mandated medication reconciliation.¹⁵

Assessment of platelet activity

Platelet activity was measured with the VerifyNow-P2Y12 assay (Accumetrics, CA). The VerifyNow-P2Y12 contains human fibrinogen coated beads and platelet agonist and uses an optical detection system that measures platelet-induced aggregation as an increase in light transmittance. The test was designed to measure the ADP mediated impact on the P2Y12 receptor.¹⁶ The results are reported in P2Y12 reaction units (PRU), with ≤180 units indicating therapeutic P2Y12 inhibition.

ICH volume measurement

Patient's diagnostic CT scans and follow-up CT scans were uploaded to a dedicated workstation to calculate hematoma volume (Analyze v14, AnalyzeDirect). Follow-up CT scans were identified as the first brain CT scans after the diagnostic scan. Intraventricular hemorrhage (IVH) was excluded from measurement as IVH volume is difficult to reliably calculate due to its mixture with CSF. The date and time of CTs were prospectively recorded.

Follow-up

The modified Rankin Scale (mRS) was recorded at 14 days or discharge, whichever came first, and at 3 months with a standardized questionnaire.¹⁷

Statistical analysis

HE was defined as the difference between hematoma volumes on the initial and follow-up CT scans. Normally distributed data are presented as mean ± SD and non-normally distributed data as median [Q1 – Q3]. Grouped data were compared with Mann–Whitney U (2 groups) or Kruskal–Wallis H for (>2 groups) and Dunn's test for multiple comparisons.

Results

In total, 762 patients were initially screened, and 318 had multiple CT volumes recorded. Of the patients with multiple CT volumes recorded, 194 presented within 12 h of symptom onset and were included in the cohort. Demographics are shown in Table 1. Most patients (72.0%) had a history of hypertension. Of note, 59 (30.4%) patients took aspirin and 15 (7.7%) took a P2Y12 inhibitor (one took prasugrel, the rest clopidogrel) prior to ICH. Eight patients (4.1%) were on both aspirin and a P2Y12 inhibitor (i.e., DAPT). Ninety-two patients experienced IVH. The median times of the initial and follow-up CT scans from symptom onset were 1.6 [0.9–4.0] and 28.2 [12.7–39.0] hours, respectively.

Table 1 Demographics.

Variable (n)	N (%), mean ± SD, or Median [IQR]
Age, y	62.0 ± 14.3
Race
White	98 (50.5)
Black or African American	86 (44.3)
Native Pacific Islander	5 (2.6)
Asian	3 (1.5)
American Indian/Native Alaskan	1 (0.5)
Unknown/declined	1 (0.5)
Ethnicity
Hispanic	13 (6.7)
Women	96 (49.5)
Aspirin dose before ICH
0	135 (69.6)
81 mg/day	37 (19.1)
>81 mg/day	22 (11.3)
P2Y12 inhibitor use before ICH	15 (7.7)
INR on admission	1.0 [1.0–1.1]
Systolic BP on admit, mm Hg	192 ± 43
ICH location
Lobar	62 (32.0)
Thalamus	55 (28.4)
Lentiform Nucleus	44 (22.7)
Brainstem	14 (7.2)
Cerebellar	9 (4.6)
Caudate	7 (3.6)
Other	3 (1.5)

HE varied with pre-ICH medications. Overall, most patients had minimal changes in hematoma volumes, and HE was 0.1 [−0.8 to 2.1] mL. Pre-ICH P2Y12 inhibitor use was associated with more HE. Patients taking P2Y12 inhibitors prior to ICH had more HE (3.5 [1.2–11.9] vs. 0.1 [−0.8–1.4] mL, p = 0.004, Fig. 1). Pre-ICH P2Y12 inhibitor use was also associated with a greater first ICH volume measurement (40.6 [10.8–48.1] vs. 8.5 [3.4–19.9] mL, p = 0.01).

Figure 1. Boxplot of the absolute change in hematoma volume between first and follow-up CTs by P2Y12 inhibitor use. Significance was calculated with Mann–Whitney U. * indicates p-value [less than] 0.05.

P2Y12 inhibitors may be combined in clinical practice with aspirin as DAPT, so we tested the hypothesis that combinations of aspirin and P2Y12 inhibitors are associated with HE (p = 0.007, Fig. 2). After correction for multiple comparisons, patients on DAPT had significantly greater HE compared to patients who took no antiplatelet medications prior to ICH (7.2 [2.6–13.8] vs. 0.0 [−1.0–1.1] mL, p = 0.04). There was so significant difference between the time of symptom onset and the time of the initial scan between the combined groups (p > 0.1).

Figure 2. Boxplot of the absolute change in hematoma volume between first and follow-up CTs by overall antiplatelet combination. DAPT, dual antiplatelet therapy. Significance was calculated with a Kruskal–Wallis H-test followed by a post hoc Dunn's test with multiple corrections. * indicates p-value [less than] 0.05.

Measured P2Y12 inhibition might provide additional information to medication history alone, so we repeated the analysis in patients who had P2Y12 inhibition measured. P2Y12 activity was measured in 94 patients (40%), 15 of whom had pre-ICH P2Y12 inhibitor use. P2Y12 inhibition was not related to ethnicity, gender, age, admission blood pressure, or time to the diagnostic CT (p > 0.1 for all). P2Y12 inhibition was associated with antiplatelet medication combinations (none, aspirin, P2Y12 inhibition, or DAPT, p = 0.002, Fig. 3). Patients with known P2Y12 inhibitor use had less P2Y12 activity, 178 [149–203] compared to patients taking no P2Y12 inhibitors (288 [246–319] PRU, p = 0.005) or patients who took aspirin (304 [264–323] PRU, p = 0.002).

Figure 3. Boxplot of P2Y12 assay results by overall antiplatelet combination. DAPT, dual antiplatelet therapy. Significance was calculated with a Kruskal–Wallis H-test followed by a post hoc Dunn's test with multiple corrections. ** indicates p-value [less than] 0.01.

Overall functional outcomes were poor in this cohort. The median 14 days or discharge mRS score for patients was 5 [4–5], indicating severe disability, and the median 3-month mRS score was 4 [2–6], indicating dependence for daily activities. Between patients on P2Y12 inhibitors and those not, there was no difference in mRS scores at 14 days or discharge (5 [4–6] vs. 5 [4–5], p = 0.17) or at 3 months (6 [4–6] vs 4 [2–6], p = 0.06). There was similarly no difference in mRS scores between the antiplatelet categories at 14 days or discharge (p = 0.6) or at 3 months (p = 0.07).

Discussion

In a cohort of patients with spontaneous ICH, we found that the use of the P2Y12 inhibitor clopidogrel was associated with less P2Y12 activity and more HE. Patients on DAPT (combined P2Y12 inhibition and aspirin) experienced the most HE. The magnitude HE related to spontaneous ICH has been shown to be influenced by previous medications patients have, ranging from around 1 mL to almost 10 mL for aspirin and anticoagulants, respectively.^2,8,12 DAPT associated HE in this cohort was in between aspirin and anticoagulants. These data suggest that P2Y12 inhibitors are synergistic with aspirin with respect to HE, identifying a subpopulation of patients at particularly high risk for HE.

DAPT is commonly used to decrease the thrombotic complications secondary to atherosclerotic cardiovascular diseases such as coronary artery disease (CAD). As the US population ages, these numbers, and therefore patients on DAPT, will likely increase. This, in addition to the 100,000 people present with ICH in the US every year, highlights the importance identifying key risk factors and treatment strategies for HE.

Reversing P2Y12 inhibition seems attractive as a potential therapeutic approach to reduce HE, and, potentially, improve patient outcomes after ICH. However, an appropriate reversal agent for P2Y12 inhibitors is not clear. Desmopressin reliably reverses the effect of aspirin,¹⁸ but it is not known if desmopressin would be effective against P2Y12 inhibitors. Retrospective studies of the effect of desmopressin on antiplatelet associated ICH have been mixed,¹⁹ and a prospective trial enrolled few patients and without a clear therapeutic effect.²⁰ Platelet transfusion has been shown to be harmful to patients with ICH known to take aspirin and was ineffective in reducing HE,²¹ suggesting it would not benefit patients known to take P2Y12 inhibitors. Patients with known clopidogrel use are included in an ongoing trial of recombinant, activated Factor VII, a potent hemostatic drug,²² so a post hoc analysis could be of interest.

HE predicts disability or death at follow-up.³ We did not find associations between P2Y12 inhibitor use and the mRS, although the overall poor outcomes reduced the power to show any association. Additionally, the sample size of the combined antiplatelet categories meant that the comparisons between are unadjusted, which in addition to the small sample size may conflate or limit the identification of associations, respectively.

This work has other limitations. There is potential selection bias due to the exclusion of patients without a follow-up scan (e.g., due to surgery or death). While this is a single-center study without protocolized CT intervals, the methods and outcomes are standard. We did not include IVH in our measurement of ICH due to the challenges of quantifying blood density when mixed with CSF and its subsequent effects on hydrocephalus and ventricular drainage. We did not specifically measure the change in P2Y12 activity and potential interventions, which is an opportunity for further study. Strengths of this work include prospective collection of the initial stay, follow-up variables, platelet activity, and the computerized volumetric calculations.

Conclusion

We found that pre-ICH P2Y12 inhibitor use was associated with laboratory evidence of P2Y12 inhibition and more HE, particularly for patients taking combined P2Y12 inhibition and aspirin. Further study should focus on reversing the effect of P2Y12 inhibition as a potential strategy for minimizing HE.

Acknowledgments

All those who meaningfully contributed to the article are included as authors.

Author Contributions

Ethan J. Houskamp: Conceptualization, Writing – Original draft preparation Yuzhe Liu: Conceptualization, Writing – Reviewing and Editing Juliana Silva Pinheiro do Nascimento: Data curation, Investigation Babak S. Jahromi: Conceptualization, Writing – Reviewing and Editing Paul F. Lindholm: Conceptualization, Resources, Writing – Reviewing and Editing Hau C. Kwaan: Conceptualization, Writing – Reviewing and Editing Andrew M. Naidech: Conceptualization, Formal analysis, Supervision, Writing – Reviewing and Editing.

Conflict of Interest Statement

The authors have no disclosures related to the submitted work.

Data Availability Statement

The authors wishing to reproduce the analysis should contact the corresponding author. Data will be shared as per NIH regulations.