Relationship between endothelial dysfunction, oxidant stress and aspirin resistance in patients with stable coronary heart disease

Endothelial dysfunction in young healthy men is associated with aspirin resistance

The aim of this study was to investigate the relation between endothelial dysfunction and aspirin response in a young healthy population (102 men aged 18-40). Initial concentrations of the NO pathway metabolites (ADMA, l-arginine, SDMA), cardiovascular risk markers, oxidative stress markers (MDA, thiol index), sICAM1, sVCAM1, PAI-1, sE-selectin, sP-selectin, VEGF, thromboxane B2, 6-keto-PGF1α and arachidonate-induced platelet aggregation (to separate aspirin resistant from sensitive group) were measured. Flow-mediated-vasodilation (FMD) was measured before and after intravenous infusion of 16.0 g of l-arginine. Measurements were repeated following aspirin administration (75 mg/24 h) for 4 days. Both groups were homogenous regarding demographic and biochemical characteristics reflecting cardiovascular risk. Aspirin resistant subjects were characterized by lower baseline FMD and higher FMD following aspirin and l-arginine treatment, as compared to aspirin sensitive control. MDA and nitrotyrosine were greater, whereas thiol index was lower in aspirin resistant men. The sICAM1, sVCAM1, PAI-1, sE-selectin, sP-selectin and VEGF levels were similar in the analyzed groups. Thromboxane in aspirin resistant subjects was greater both at baseline and following aspirin therapy. However, a significant decrease following aspirin treatment was present in both groups. Aspirin resistance in young men is associated with endothelial dysfunction, which could be due to oxidative stress resulting from lipid peroxidation.

Persistent high on-treatment platelet reactivity in acute coronary syndrome

Persistent high on-treatment platelet reactivity in acute coronary syndrome (ACS) patients managed with appropriate antiplatelet therapy has been correlated with increased risk of cardiovascular events; however, the evolution of this phenomenon overtime is not well known. We investigated platelet activity at a three month follow-up after initial presentation with an ACS. We enrolled a total of 124 patients in the study, 65 were diagnosed with ACS and 59 controls who presented with non-cardiac chest pain for baseline comparisons. Of the enrolled patients, we had 25 ACS patients return, in stable condition, three months after their initial presentation for repeat platelet functional testing. Epinephrine (EPI), adenosine diphosphate (ADP), and arachidonic acid induced platelet aggregation were monitored at baseline with repeat measurement of EPI- and ADP-stimulated aggregation at follow-up. In addition, P-selectin and PAC-1 expression were monitored at presentation and at a three month follow-up period. ACS patients were maintained on aspirin therapy during the intervening period. At the three month follow-up visit, ACS patients initiated on aspirin had no significant percentage change in aggregation to submaximal concentrations of EPI and ADP. They also had no significant percentage change in PAC-1 or P-selectin expression. This study demonstrates persistent high on-treatment platelet reactivity in ACS patients at a three month follow-up, which may place these patients at increased risk of recurrent cardiovascular events.

Relationship between endothelial functions and acetylsalicylic acid resistance in newly diagnosed hypertensive patients

BACKGROUND

We aimed to investigate the effects and dose dependency of aspirin on endothelial functions and prevalence of aspirin resistance in newly diagnosed hypertensive patients without previous drug therapy and development of cardiac complications.

HYPOTHESIS

Acetylsalicyclic acid improves endothelial function.

METHODS

Fifty-eight hypertensive patients and 61 healthy subjects in the control group were included in the study. Endothelial functions of the patient and control groups were evaluated with brachial artery examination. Patient and control groups were divided into 2 groups. A total of 100 mg and 300 mg of aspirin were given to the separate groups for 1 week. After 1 week, endothelial functions were reevaluated and aspirin resistance examined with a platelet function analyzer (PFA-100; Dade Behring, Marbourg, Germany).

RESULTS

Baseline flow-mediated dilatation (FMD) change percent in hypertensive patients was 9.8%, and it was significantly lower than in the control group (12%) (P < 0.001). Frequency of acetylsalicylic acid (ASA) resistance was 20% and 26% in control and hypertensive patient groups, respectively (P = not significant). ASA resistance was 28% and 24% in 100 mg and 300 mg in hypertensive patients, respectively (P = not significant). FMD change percent increased both in the control and hypertensive groups after ASA treatment from 12.4% to 13.3% and 9.8 % to 11.9 %, respectively. FMD percentage change was significantly increased in hypertensive patients irrespective of ASA resistance (P = 0.02, for ASA resistance [+]; P < 0.012, for ASA resistance [-]).

CONCLUSIONS

Endothelial functions were impaired more in hypertensive patients compared to the control group. Endothelial functions were improved with all ASA doses in hypertensive patients irrespective of ASA resistance.

Aspirin and antiplatelet agent resistance: implications for prevention of secondary stroke

Oral antiplatelet drugs, including aspirin, clopidogrel and extended-release dipyridamole, are widely prescribed for the secondary prevention of vascular events, including stroke. Despite the benefits of antiplatelet therapy, 10−20% of patients experience a recurrent vascular event while taking antiplatelet medication. This article discusses the concept of antiplatelet resistance in general, focusing on aspirin resistance in particular, as a poorly defined cause of recurrent vascular events. Factors such as the lack of a standardized method to diagnose aspirin resistance and a poor clinical correlation with laboratory assays make the treatment of aspirin nonresponders difficult. In addition, there are confounding conditions such as diabetes mellitus that can affect aspirin resistance and determine a different course of treatment for these patients. Other antiplatelet options may also have resistant subpopulations; thus, alternative strategies for the secondary stroke patient must be explored.