Aspirin and stroke prevention

Stroke care in Africa: A systematic review of the literature

Background

Appropriate systems of stroke care are important to manage the increasing death and disability associated with stroke in Africa. Information on existing stroke services in African countries is limited.

Aim

To describe the status of stroke care in Africa.

Summary of review

We undertook a systematic search of the published literature to identify recent (1 January 2006–20 June 2017) publications that described stroke care in any African country. Our initial search yielded 838 potential papers, of which 38 publications were eligible representing 14/54 African countries. Across the publications included for our review, the proportion of stroke patients reported to arrive at hospital within 3 h from stroke onset varied between 10% and 43%. The median time interval between stroke onset and hospital admission was 31 h. Poor awareness of stroke signs and symptoms, shortages of medical transportation, health care personnel, and stroke units, and the high cost of brain imaging, thrombolysis, and outpatient physiotherapy rehabilitation services were reported as major barriers to providing best-practice stroke care in Africa.

Conclusions

This review provides an overview of stroke care in Africa, and highlights the paucity of available data. Stroke care in Africa usually fell below the recommended standards with variations across countries and settings. Combined efforts from policy makers and health care professionals in Africa are needed to improve, and ensure access, to organized stroke care in as many settings as possible. Mechanisms to routinely monitor usual care (i.e., registries or audits) are also needed to inform policy and practice.

The dogma of aspirin: a critical review of evidence on the best monotherapy after dual antiplatelet therapy

Dual antiplatelet therapy based on the combination of an adenosine diphosphate (ADP)-receptor antagonist plus aspirin has demonstrated to be more effective in reducing the rate of major ischemic vascular events compared to aspirin monotherapy in some clinical settings. The current controversy on the duration of dual antiplatelet therapy should not conceal another major issue: the choice of the more appropriate antiplatelet monotherapy after the dual treatment phase. The aim of this article is to critically analyze the available evidence in this topic.

Data from studies like CAPRIE, MATCH, PROFESS, CHANCE, DAPT and others, raise questions as why antiplatelet monotherapy after the dual phase should only be based on aspirin, in spite of a lack of evidence surprisingly not highlighted by key opinion leaders and experts.

We conclude that, whether ADP-receptor antagonist rather than aspirin may be proposed as monotherapy seems not only have no answer but also not place in the current specialists’ analysis, as if a dogmatic approach were prevalent. Perhaps the time for an open debate on these topics is ripe.

Aspirin is a substrate for paraoxonase-like activity: implications in atherosclerosis

Paraoxonase 1 (PON 1) is an enzyme that is promiscuous in its ability to hydrolyze various types of substrates. It hydrolyzes aryl esters, phosphate esters, lactones, and reduces lipid peroxides to hydroxides. Aspirin is an aryl ester with a short plasma half life. We hypothesized that aspirin would be effectively hydrolyzed by PON 1 and many of its anti-atherogenic effects, at least in part, could be accounted for by its antioxidant product, salicylic acid. In this study, we determined the ability of human plasma and PON 1-rich HDL to hydrolyze acetyl ester of salicylic acid (aspirin). The ability of aspirin to compete for the hydrolysis of paraoxon and p-nitrophenylacetate was determined. In addition, nitrated aspirin was synthesized and tested directly for hydrolysis. Aspirin competed for the hydrolysis of paraoxon and p-nitrophenylacetate by HDL in a dose-dependent manner. Human plasma and HDL were also able to hydrolyze nitroaspirin and aspirin and release nitrosalicylic acid and salicylic acid, respectively. These findings suggest that salicylic acid might be generated in the plasma from aspirin. The ability of long-term treatment with aspirin to retard atherosclerosis might be dependent on the generation of free salicylic acid, a scavenger of free radicals.

Prostaglandin A1 inhibits increases in intracellular calcium concentration, TXA(2) production and platelet activation

AIM

In our previous studies we found that cyclopentenane prostaglandin A1 (PGA1) had neuroprotective effects in a rodent ischemic model. In the present study we aimed to investigate the inhibitory effect of PGA1 on platelet function.

METHOD

The rate of aggregation of human platelets was measured by using turbidimetry. The rate of adhesion of platelets to cultured endothelial cells was determined by using [(3)H]-adenine labeled platelets. 5-Hydroxytryptamine release from platelets was measured with O-phthaldialdehyde fluorospectrophotometry. The levels of TXB(2), a stable metabolite of TXA(2), were determined by radioimmuno-assay. Alternations in platelet morphology were observed using an electron microscope, and the intraplatelet free calcium concentrations were measured with Fluo-3/AM FCM assay.

RESULTS

PGA1 significantly inhibited thrombin-, collagen- and ADP-induced aggregation and adhesion of platelets. The morphological changes of platelets induced by thrombin were blocked by PGA1. PGA1 inhibited the release of 5-hydroxytyptamine from dense granules and the synthesis of TXA(2).

CONCLUSION

PGA1 inhibits the activation of platelets probably through blocking increases in intracellular calcium concentration and TXA(2) synthesis.

Stroke prevention, treatment, and rehabilitation in sub-saharan Africa

Stroke is emerging as a leading cause of preventable death and disability in adults in many developing nations. In Sub-Saharan Africa (SSA), stroke mortality and case fatality in some countries exceed those in the developed world. Stroke also occurs at much earlier ages in SSA, resulting in a greater number of years of potential life lost. The high social and economic burden of stroke calls for effective strategies for prevention, treatment, and rehabilitation in SSA. High blood pressure is the most powerful predictor of stroke, and its treatment can reduce the risk of stroke by > or = 40%. Effective stroke prevention calls for comprehensive risk reduction including blood pressure control. Population-based health education programs and appropriate public health policy coupled with high-risk strategies targeting hypertensive persons and stroke patients must be developed. A broad partnership of key players, innovative funding mechanisms, and increased national and international commitment for the prevention and control of stroke in sub-Saharan Africa and other developing countries is needed.