Aspirin treatment failure: is this a real phenomenon? A review of the aetiology and how to treat it

Contemporary Antiplatelet and Anticoagulant Therapies for Secondary Stroke Prevention: A Narrative Review of Current Literature and Guidelines

PURPOSE OF REVIEW

Stroke is a leading cause of death and disability worldwide. The annual incidence of new or recurrent stroke is approximately 795,000 cases per year in the United States, of which 87% are ischemic in nature. In addition to the management of modifiable high-risk factors to reduce the risk of recurrent stroke, antithrombotic agents (antiplatelets and anticoagulants) play an important role in secondary stroke prevention. This review will discuss the published literature on the use of antiplatelets and anticoagulants in secondary prevention of acute ischemic stroke and transient ischemic attack (TIA), including their pharmacology, efficacy, and adverse effects. We will also highlight the role of dual antiplatelet therapy (DAPT) in secondary stroke prevention, along with supporting literature.

RECENT FINDINGS

Single antiplatelet therapy (SAPT) with aspirin or clopidogrel reduces the risk of recurrent ischemic stroke in patients with non-cardioembolic ischemic stroke or TIA. However, as shown in recent trials, short-term DAPT with aspirin and clopidogrel or ticagrelor for 21-30 days is more effective than SAPT in patients with minor acute non-cardioembolic stroke or high-risk TIA. Although short-term DAPT is highly effective in preventing recurrent stroke, a more prolonged course can increase bleeding risks without additional benefit. DAPT for 90 days, followed by aspirin monotherapy for patients with large vessel intracranial atherosclerotic disease, is suitable for secondary stroke prevention. However, patients need to be monitored for both minor (e.g., bruising) and major (e.g., intracranial) bleeding complications. Conversely, oral warfarin and newer direct oral anticoagulant (DOACs) such as dabigatran, rivaroxaban, apixaban, and edoxaban are the agents of choice for secondary stroke prevention in patients with non-valvular cardioembolic strokes. DOACs may be preferred over warfarin due to decreased bleeding risks, including ICH, lack of need for international normalized ratio monitoring, no dietary restrictions, and limited drug-drug interactions. The choice between different antiplatelets and anticoagulants for prevention of ischemic stroke depends on the underlying stroke mechanism, cytochrome P450 2C19 polymorphisms, bleeding risk profile, compliance, drug tolerance, and drug resistance. Physicians must carefully weigh each patient's relative benefits and bleeding risks before initiating an antiplatelet/anticoagulant treatment regimen. Further studies are warranted to study the optimal duration of DAPT in symptomatic intracranial atherosclerosis since the benefit is most pronounced in the short term while the bleeding risk remains high during the extended duration of therapy.

Antiplatelet Use in Ischemic Stroke

Objective:

A literature review of antiplatelet agents for primary and secondary stroke prevention, including mechanism of action, cost, and reasons for lack of benefit.

Data sources:

Articles were gathered from MEDLINE, Cochrane Reviews, and PubMed databases (1980-2021). Abstracts from scientific meetings were considered. Search terms included ischemic stroke, aspirin, clopidogrel, dipyridamole, ticagrelor, cilostazol, prasugrel, glycoprotein IIb/IIIa inhibitors.

Study selection and data extraction:

English-language original and review articles were evaluated. Guidelines from multiple countries were reviewed. Articles were evaluated independently by 2 authors.

Data synthesis:

An abundance of evidence supports aspirin and clopidogrel use for secondary stroke prevention. In the acute phase (first 21 days postinitial stroke), these medications have higher efficacy for preventing further stroke when combined, but long-term combination therapy is associated with higher hemorrhage rates. Antiplatelet treatment failure is influenced by poor adherence and genetic polymorphisms. Antiplatelet agents such as cilostazol may provide extra benefit over clopidogrel and aspirin, in certain racial groups, but further research in more diverse ethnic populations is needed.

Relevance to patient care and clinical practice:

This review presents the data available on the use of different antiplatelet agents poststroke. Dual therapy, recurrence after initiation of secondary preventative therapy, and areas for future research are discussed.

Conclusions:

Although good evidence exists for the use of certain antiplatelet agents postischemic stroke, there are considerable opportunities for future research to investigate personalized therapies. These include screening patients for platelet polymorphisms that confer antiplatelet resistance and for randomized trials including more racially diverse populations.

Electrical impedance vs. light transmission aggregometry: Testing platelet reactivity to antiplatelet drugs using the MICELI POC impedance aggregometer as compared to a commercial predecessor

BACKGROUND

Patients' responses to antiplatelet therapy significantly vary, with individuals showing high residual platelet reactivity associated with thrombosis. To personalize thrombosis management, platelet function testing has been suggested as a promising tool able to monitor the antithrombotic effect of antiplatelet agents in real-time. We have prototyped the MICELI, a miniature and easy-to-use electrical impedance aggregometer (EIA), measuring platelet aggregation in whole blood. Here, we tested the capability of the MICELI aggregometer to quantify platelet reactivity on antiplatelet agents, as compared with conventional light-transmission aggregometry (LTA).

METHODS

Platelet aggregation in ACD-anticoagulated whole blood and platelet-rich plasma of healthy donors (n = 30) was evaluated. The effect of clopidogrel, ticagrelor, cangrelor, cilostazol, and tirofiban on ADP-induced aggregation was tested, while aspirin was evaluated with arachidonic acid and collagen. Platelet aggregation was recorded using the MICELI or BioData PAP-8E (Bio/Data Corp.) aggregometers.

RESULTS

The MICELI aggregometer detected an adequate and comparable dose-dependent decrease of platelet aggregation in response to increments of drugs' concentrations, as compared to LTA (the inter-device R² = 0.79-0.93). Platelet aggregation in platelet-rich plasma recorded by LTA showed higher sensitivity to antiplatelet agents, but it couldn't distinguish between different drug doses as indicated by saturation of the aggregatory response.

CONCLUSION

Platelet aggregation in whole blood as recorded by EIA represents a better model system for evaluation of platelet reactivity as compared with platelet aggregation in platelet-rich plasma as recorded by LTA, since EIA takes into consideration the modulatory effect of other blood cells on platelet hemostatic function and pharmacodynamics of antiplatelet drugs in vivo. As such, the MICELI impedance aggregometer could be potentially employed for the point-of-care monitoring of platelet function in patients on-treatment for personalized tailoring of their antiplatelet regimen.

Acute Stroke in Diabetes Mellitus: A Prospective Observational Study Evaluating the Course and Short-Term Outcome in Basrah, Southern Iraq

Introduction Stroke and diabetes mellitus (DM) are distinct conditions with many aspects in common. Both conditions are prevalent and associated with various vascular risk factors such as dyslipidemia and hypertension. This study was conducted to evaluate the association between stroke and DM regarding the course (i.e., type, recurrence, aspirin failure, and degree of disability) of stroke and short-term outcomes in patients with diabetes who suffer an acute stroke. Patients and methods We conducted a prospective observational study of 210 acute stroke patients admitted to the Neurology Unit of Al-Basrah Teaching Hospital in Basrah City in Southern Iraq from May 2014 to September 2015. Our study included 124 men (59%) and 86 (41%) women, and our study population had a mean age of 64 ± 11 years. The study participants were separated into two groups of 105 patients according to their diabetes status, and we evaluated each patient's type of stroke, recurrence, aspirin failure, and degree of neurological disability according to the National Institutes of Health stroke scale. We assessed short-term outcomes (i.e., four weeks' mortality) following acute stroke. Results Ischemic stroke was the primary stroke experienced by patients with diabetes (94.3%), which is highly significant and associated with an increased risk of previous recurrent ischemic stroke (55.2%; P=0.003, <0.001, respectively). We noted a higher rate of loss of antiplatelet activity from aspirin in patients with DM rather than those without DM (p<0.001), and we noted more severe disability in outcomes in patients with DM. In the group of stroke patients with diabetes, 46 patients (59%) died, while 32 patients (41%) without diabetes died (p=0.046). Conclusion DM is associated with a heavier burden for acute stroke along with poorer outcomes than patients without DM. Our findings suggest acute stroke in patients with diabetes may be considered a distinct entity separate from acute stroke in patients without diabetes. The treatment of acute stroke in patients with diabetes warrants further investigation.

Stroke occurrence while on antiplatelet therapy may predict atrial fibrillation detected after stroke

BACKGROUND AND AIMS

Stroke occurrence while on antiplatelet therapy, i.e., a breakthrough stroke, is often conveniently attributed to antiplatelet resistance. However, undetected paroxysmal atrial fibrillation (AF) may underlie breakthrough strokes. We hypothesized that a breakthrough stroke may be a clinical marker for patients at risk of having AF detected after stroke (AFDAS).

METHODS

Consecutive patients without known AF hospitalized for ischemic stroke between 2000 and 2013 were identified from nationwide claims data. The independent variable of interest was continued use of antiplatelet therapy within 30 days before stroke. The diagnosis of AF and comorbidities were ascertained using validated algorithms. Stroke severity (National Institutes of Health Stroke Scale [NIHSS]) was estimated using a validated claims-based method. Univariable and multivariable Cox regression analyses were used to determine the effect of breakthrough strokes on the occurrence of AFDAS separately in patients with mild and severe stroke (estimated NIHSS ≤10 versus >10).

RESULTS

Among 17,076 patients (40% female, mean age 69 years), 3314 (19%) were on antiplatelet therapy before stroke. In patients with mild stroke, prior antiplatelet use was significantly associated with the occurrence of AFDAS (adjusted hazards ratio, 1.26; 95% confidence interval, 1.08-1.48). In contrast, no association existed between prior antiplatelet use and the risk of AFDAS in those with severe stroke.

CONCLUSIONS

Patients with a breakthrough stroke of mild severity while on antiplatelet therapy carried an increased risk of AFDAS compared to those not on antiplatelet therapy. Our findings may help prioritize patients for advanced cardiac monitoring in daily practice.