A review of aspirin resistance; definition, possible mechanisms, detection with platelet function tests, and its clinical outcomes

Aspirin (acetylsalicylic acid) is one of the main therapeutics in prevention of thrombo-embolic vascular events. Its efficiency is proved in the prevention of cardiovascular events. However, antiplatelet effect of aspirin is not absolute in all patients and some patients experience thrombo-embolic events despite aspirin. These patients are clinically called as aspirin resistant or aspirin non-responders. Globally, a lot of people are affected by aspirin resistance according to the high prevalence of athero-thrombotic vascular diseases. A prevalence of 5.5-45% in patients with various cardiovascular disease by different laboratory methods has been reported for aspirin resistance. Clinical outcome of aspirin resistance has been demonstrated in patients with different vascular diseases. Detection of platelet function in patients treated with aspirin may be necessary in the prediction of clinical outcome. Point of care methods, which have correlated results with the standard light transmittance aggregometry may be appropriate choices in the detection of platelets' response to antiplatelet therapy. Adequate additional therapies may reduce atherothrombotic risks and major cardiovascular events rate in aspirin resistant subjects. None of the current researches advised the cessation of aspirin therapy. There is need to investigate the efficacy of additional adenosine diphosphate receptor antagonists or newer antiplatelet agents in aspirin resistant subjects. The intent of this paper is to review the literature discussing possible mechanisms, determination techniques, and clinical effects of aspirin resistance

A current problem in atherothrombotic diseases aspirin resistance: Definition, mechanisms, determination with laboratory tests and clinical implications

Aspirin (acetylsalicylic acid) is a powerful antiplatelet agent used in prevention of atherothrombotic vascular events. However, antiplatelet effect of aspirin is not uniform and some patients could not benefit from aspirin. These patients are clinically called as aspirin resistant or aspirin non-responders. Aspirin resistance could be determined by: bleeding time, optical aggregometry, PFA-100 (Platelet Function Analyzer), Ultegra-RPFA (Rapid Platelet Function Assay), activated aggregation time, whole blood aggregometry, platelet aggregate ratio, flow cytometry, measurements of platelet surface proteins and blood or urine thromboxane 132 levels. Mechanisms of aspirin resistance have not been elucidated yet. There is evidence that aspirin resistance increases clinical cardiovascular events. Adequate additional therapies may reduce atherothrombotic risks and major cardiovascular events rate in aspirin resistant subjects. However, we need further studies to decrease major cardiovascular events risk in aspirin resistant subjects and to optimize antiplatelet therapy

Metastatic Ewing's sarcoma involving the right ventricle

Cardiac metastasis of Ewing's sarcoma is rare. A 22-year-old woman was admitted with complaints of palpitation and fatigue on exertion. She had a seven-year history of radical right tibial resection for Ewing's sarcoma and was also receiving chemotherapy for lung metastasis of Ewing's sarcoma. Both transthoracic and transesophageal echocardiography demonstrated a single, large (3x3.5 cm) inhomogeneous mass located in the free wall of the right ventricle. To differentiate the mass from a massive thrombus, contrast-enhanced magnetic resonance imaging was performed. The mass showed partial contrast enhancement, suggesting a malignant metastatic mass. Surgical resection was not considered due to accompanying lung metastasis and potentially poor outcome of the operation

Effect of Cigarette Smoking on Platelet Aggregation

Background: Cigarette smoking may increase platelet aggregation and cause atherothrombotic cardiovascular events. We aimed to investigate the impact of cigarette smoking on platelet function in patients with ischemic coronary heart disease (CHD). Methods: Twenty patients with ischemic stable CHD under aspirin therapy (300 mg/d), who continue to smoking despite all warnings, and 20 nonsmokers with CHD are enrolled in the study. Platelet function is studied at the morning, before and 15 minutes after the first cigarette, by the Platelet Function Analyzer (PFA)-100, with collagen and epinephrine and collagen and adenosine diphosphate cartridges. Post aspirin platelet hyperactivity is defined as having a closure time (CT) shorter than 186 seconds despite regular aspirin intake. Serial CT measurements are analyzed by paired samples t test. Results: Persistent platelet activity was present in 4 smoker (20%) and 3 nonsmoker (15%) patients at the beginning. Platelet activity measured by the PFA-100 is been increased significantly after cigarette smoking (P = .004). Shorter CTs were determined after smoking in all patients with and without baseline persistent platelet activity, and 4 more participants became aspirin nonresponder (P = .004). No significant differences in demographic, hematological, and biochemical parameters were determined between aspirin responders and nonresponders. Conclusions: We determined that cigarette smoking may increase platelet aggregation in patients with ischemic CHD in an aspirin nonresponsive manner. Our results emphasize the importance of quitting cigarette smoking in patients with CHD

Impact of genetic polymorphisms on platelet function and aspirin resistance

Genetic polymorphisms may affect platelets' responses to the antiplatelet therapy. Our aim was to determine the role of genetic polymorphisms on aspirin resistance in patients with coronary heart disease (CHD). A total of 126 consecutive patients (35-85 years old, 32% women) with chronic stable CHD was enrolled in the study. Platelet function assays were realized by the platelet function analyzer (PFA)-100 with Collagen and epinephrine (Col/Epi) and collagen and adenosine diphospate (Col/ADP) cartridges. Aspirin resistance was defined as having a closure time of less than 186 s with Col/Epi cartridges despite regular aspirin therapy. Factor V, prothrombin, factor XIII, beta-fibrinogen, plasminogen activator inhibitor I (PAI-1), glycoprotein Ilia, methylene tetrahydrofolate reductase, ACE and ApoB gene polymophisms were determined by three consecutive steps: isolation and amplification of DNA and reverse hybridization. We determined that 30 patients (23.8%) had aspirin resistance by the PFA-100. Mean closure time measured with the Col/ADP cartridges was 74 +/- 12 s (51-104s). Ten of the 30 patients with aspirin resistance were women (33.3%). Genetic polymorphisms were determined in 30 aspirin-resistant and 17 aspirin-sensitive patients. No statistically significant relationship was determined between aspirin resistance and the genetic panel. In our study we did not determine a significant relationship between the aspirin resistance and factor V, prothrombin, factor XIII, beta-fibrinogen, PAI-1, glycoprotein Ilia, methylene tetrahydrofolate reductase, ACE and ApoB gene polymophisms. Blood Coagul Fibrinolysis 21:53-56 (C) 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins