Aspirin nonresponders in patients with ischaemic stroke:

The Role of Thromboxane in the Course and Treatment of Ischemic Stroke: Review

Cardiovascular diseases are currently among the leading causes of morbidity and mortality in many developed countries. They are distinguished by chronic and latent development, a course with stages of worsening of symptoms and a period of improvement, and a constant potential threat to life. One of the most important disorders in cardiovascular disease is ischemic stroke. The causes of ischemic stroke can be divided into non-modifiable and modifiable causes. One treatment modality from a neurological point of view is acetylsalicylic acid (ASA), which blocks cyclooxygenase and, thus, thromboxane synthesis. The legitimacy of its administration does not raise any doubts in the case of the acute phase of stroke in patients in whom thrombolytic treatment cannot be initiated. The measurement of thromboxane B2 (TxB2) in serum (a stable metabolic product of TxA2) is the only test that measures the effect of aspirin on the activity of COX-1 in platelets. Measurement of thromboxane B2 may be a potential biomarker of vascular disease risk in patients treated with aspirin. The aim of this study is to present the role of thromboxane B2 in ischemic stroke and to present effective therapies for the treatment of ischemic stroke. Scientific articles from the PubMed database were used for the work, which were selected on the basis of a search for “thromboxane and stroke”. Subsequently, a restriction was introduced for works older than 10 years, those concerning animals, and those without full text access. Ultimately, 58 articles were selected. It was shown that a high concentration of TXB2 may be a risk factor for ischemic stroke or ischemic heart disease. However, there is insufficient evidence to suggest that thromboxane could be used in clinical practice as a marker of ischemic stroke. The inclusion of ASA in the prevention of stroke has a beneficial effect that is associated with the effect on thromboxane. However, its insufficient power in 25% or even 50% of the population should be taken into account. An alternative and/or additional therapy could be a selective antagonist of the thromboxane receptor. Thromboxane A2 production is inhibited by estrogen; therefore, the risk of CVD after the menopause and among men is higher. More research is needed in this area.

Significance of urinary 11-dehydro-thromboxane B2 in age-related diseases: Focus on atherothrombosis

Platelet activation plays a key role in atherogenesis and atherothrombosis. Biochemical evidence of increased platelet activation in vivo can be reliably obtained through non-invasive measurement of thromboxane metabolite (TXM) excretion. Persistent biosynthesis of TXA₂ has been associated with several ageing-related diseases, including acute and chronic cardio-cerebrovascular diseases and cardiovascular risk factors, such as cigarette smoking, type 1 and type 2 diabetes mellitus, obesity, hypercholesterolemia, hyperhomocysteinemia, hypertension, chronic kidney disease, chronic inflammatory diseases. Given the systemic nature of TX excretion, involving predominantly platelet but also extraplatelet sources, urinary TXM may reflect either platelet cyclooxygenase-1 (COX-1)-dependent TX generation or COX-2-dependent biosynthesis by inflammatory cells and/or platelets, or a combination of the two, especially in clinical settings characterized by low-grade inflammation or enhanced platelet turnover. Although urinary 11-dehydro-TXB₂ levels are largely suppressed with low-dose aspirin, incomplete TXM suppression by aspirin predicts the future risk of vascular events and death in high-risk patients and may identify individuals who might benefit from treatments that more effectively block in vivo TX production or activity. Several disease-modifying agents, including lifestyle intervention, antidiabetic drugs and antiplatelet agents besides aspirin have been shown to reduce TX biosynthesis. Taken together, these aspects may contribute to the development of promising mechanism-based therapeutic strategies to reduce the progression of atherothrombosis. We intended to critically review current knowledge on both the pathophysiological significance of urinary TXM excretion in clinical settings related to ageing and atherothrombosis, as well as its prognostic value as a biomarker of vascular events.

High On-Treatment Platelet Reactivity to Adenosine Diphosphate Predicts Ischemic Events of Minor Stroke and Transient Ischemic Attack

BACKGROUND

This study aimed to evaluate the relationship between thromboelastography adenosine diphosphate maximum amplitude (TEG-ADP_MA) and recurrent ischemic events in patients with minor ischemic stroke or high-risk transient ischemic attack (TIA).

METHODS

A total of 265 patients received dual antiplatelet therapy were consecutively enrolled. High on-treatment platelet reactivity (HTPR) to ADP was assessed by TEG-ADP_MA and detected the CYP2C19 genotype; recurrent ischemic events were followed up for 90 days after onset. The difference of recurrent ischemic events was analyzed with or without HTPR to ADP by the Kaplan-Meier, and further to determine the difference of recurrent ischemic events in each group according to TEG-ADP_MA-based tertile distribution.

RESULTS

A total of 23 (8.6%) patients had recurrent ischemic events. TEG-ADP_MA greater than or equal to 48 mm had good predictive value. Whether these patients were divided into 2 groups or 3 groups, the HTPR to ADP group had higher risk of recurrent ischemic events than the normal on-treatment platelet reactivity to ADP group by the Kaplan-Meier (all, P < .05). The tertile distribution map showed that the results of recurrent ischemic events were statistically significant in the third tertile group compared with the other two groups (all, P < .03); also, the third tertile group had a higher rate of carriers of at least 1 CYP2C19 reduced-function allele than the other two groups (P < .05).

CONCLUSIONS

In patients with minor ischemic stroke and high-risk TIA, the TEG-ADP_MA could predict recurrent ischemic events and has auxiliary effect on clinical decision-making.