Low-grade exercise enhances platelet aggregability in patients with obstructive coronary disease independently of myocardial ischemia

Acute and subacute effects of strenuous exercise on platelet aggregation, coagulation and fibrinolysis in patients with stable coronary artery disease

INTRODUCTION

Strenuous exercise may occasionally cause coronary thrombosis with myocardial infarction and sudden cardiac death.

MATERIALS AND METHODS

Patients with stable coronary artery disease (CAD) (n = 164) and healthy individuals (n = 25) performed strenuous exercise on a bicycle ergometer. Blood was drawn at baseline, immediately after exercise and 2 h later. Platelet aggregation was measured with Multiplate® Analyzer. Thrombin generation was determined using a thrombogram and by measuring prothrombin fragment 1 + 2 (F1 + 2). A clot lysis assay was used to investigate fibrinolysis.

RESULTS

From baseline to immediately after exercise, thrombin receptor activating peptide (TRAP)-induced platelet aggregation increased in CAD patients (Δ77 AU × min, 95 % confidence interval (CI): 46;107) and in healthy individuals (Δ153 AU × min, 95%CI: 75;232). Endogenous thrombin potential (ETP) was unaffected by exercise, whilst F1 + 2 increased (Δ17%, 95%CI: 11;24) in CAD patients. Fibrin clot lysis time increased by 9 % (95%CI: 1-17) in CAD patients and by 26 % (95%CI: 8;45) in healthy individuals. When comparing baseline to 2 h post-exercise, TRAP-induced platelet aggregation remained slightly elevated in both CAD patients (Δ53 AU × min, 95%CI: 22;84) and healthy individuals (Δ140 AU × min, 95%CI: 62;219). In contrast, ETP and F1 + 2 decreased in CAD patients (Δ-6 %, 95%CI: -10;-1 and Δ-8 %, 95%CI: -14;-2). Moreover, clot lysis time decreased (Δ-19 %, 95%CI: -27;-11) in patients with CAD and returned to baseline in healthy individuals. All p-values were <0.05.

CONCLUSIONS

Platelet aggregation and F1 + 2 were substantially elevated immediately after exercise in CAD patients, indicating a pro-thrombotic state. After 2 h of recovery, they exhibited a markedly increase in fibrinolysis. Similar results were observed in healthy individuals.

Effects of exercise on platelet reactivity after myocardial infarction: a randomized clinical trial

Exercise training (ET) can lower platelet reactivity in patients with cardiovascular risk factors. However, the effects of ET on platelet reactivity in higher-risk patients is unknown. The aim of this study was to evaluate the effects of ET on platelet reactivity in patients with recent myocardial infarction (MI). Ninety patients were randomly assigned 1 month post-MI to the intervention (patients submitted to a supervised ET program) or control group. All patients were on dual antiplatelet therapy (DAPT). Platelet reactivity by VerifyNow-P2Y12 (measured by P2Y12 reaction units - PRUs) test was determined at baseline and at the end of 14 ± 2 weeks of follow-up at rest (primary endpoint), and multiplate electrode aggregometry (MEA) adenosine diphosphate (ADP) and aspirin (ASPI) tests were performed immediately before and after the maximal cardiopulmonary exercise test (CPET) at the same time points (secondary endpoints). Sixty-five patients (mean age 58.9 ± 10 years; 73.8% men; 60% ST elevation MI) completed follow-up (control group, n = 31; intervention group, n = 34). At the end of the follow-up, the mean platelet reactivity was 172.8 ± 68.9 PRUs and 166.9 ± 65.1 PRUs for the control and intervention groups, respectively (p = .72). Platelet reactivity was significantly increased after the CPET compared to rest at the beginning and at the end of the 14-week follow-up (among the intervention groups) by the MEA-ADP and MEA-ASPI tests (p < .01 for all analyses). In post-MI patients on DAPT, 14 weeks of supervised ET did not reduce platelet reactivity. Moreover, platelet reactivity was increased after high-intensity exercise (ClinicalTrials.gov: NCT02958657; https://clinicaltrials.gov/ct2/show/NCT02958657).

Impact of Physical Exercise on Platelets: Focus on Its Effects in Metabolic Chronic Diseases

Chronic disorders are strongly linked to cardiovascular (CV) diseases, and it is unanimously accepted that regular exercise training is a key tool to improving CV risk factors, including diabetes, dyslipidemia, and obesity. Increased oxidative stress due to an imbalance between reactive oxygen species production and their scavenging by endogenous antioxidant capacity is the common ground among these metabolic disorders, and each of them affects platelet function. However, the correction of hyperglycemia in diabetes and lipid profile in dyslipidemia as well as the lowering of body weight in obesity all correlate with amelioration of platelet function. Habitual physical exercise triggers important mechanisms related to the exercise benefits for health improvement and protects against CV events. Platelets play an important role in many physiological and pathophysiological processes, including the development of arterial thrombosis, and physical (in)activity has been shown to interfere with platelet function. Although data reported by studies carried out on this topic show discrepancies, the current knowledge on platelet function affected by exercise mainly depends on the type of applied exercise intensity and whether acute or habitual, strenuous or moderate, thus suggesting that physical activity and exercise intensity may interfere with platelet function differently. Thus, this review is designed to cover the aspects of the relationship between physical exercise and vascular benefits, with an emphasis on the modulation of platelet function, especially in some metabolic diseases.

Platelet indices and function response to two types of high intensity interval exercise and comparison with moderate intensity continuous exercise among men after coronary artery bypass graft: A randomized trial

BACKGROUND

It has been indicated that the acute exercise increases the thrombotic events that stem from platelet hyper-reactivity. The present randomized controlled trial study was carried out with the aim to compare high-intensity interval exercise (HIIE) with moderate intensity continuous exercise (MICE) in terms of platelet indices and function in patients who had undergone post coronary artery bypass graft (CABG).

METHODS

30 men with a history of CABG were recruited and divided into 3 groups (MICE, HIIE-1, and HIIE-2). The MICE protocol consisted of running for 40 minutes with 65% of maximal heart rate (HRmax). Subjects in HIIE-1 group performed an interval exercise with work to rest ratio of 1:1 in which 10 rounds of running (95% HRmax) were followed by active recovery (35% HRmax). HIIE-2 subjects performed an interval exercise with work to rest ratio of 2:1 in which 7 rounds of running (85% HRmax) were followed by active recovery (45% HRmax). Before and immediately after the exercise protocols, blood samples were taken from subjects and analyzed to measure the variables.

RESULTS

Although platelet count (PLT) and hematocrit (HCT) were increased significantly after HIIE-1 and HIIE-2 in comparison to MICE (P < 0.050), the other platelet indices [mean platelet volume (MPV), platelet distribution width (PDW), plateletcrit (PCT)] were not significantly changed among groups (P > 0.050). The platelet aggregation and fibrinogen were further increased after HIIE-1 and HIIE-2 as compared with MICE; however, such increment were significant between HIIE-2 and MICE (P < 0.050).

CONCLUSION

It seems that HIIE, regardless of the type, has higher thrombotic potentials compared with MICE. Accordingly, MICE is safer than HIIE for rehabilitation in patients undergoing CABG.

Dobutamine stress echocardiogram-related in-stent thrombosis with acute myocardial infarction

Dobutamine stress echocardiogram (DSE) is considered a safe and reliable method for screening for underlying myocardial ischaemia. We report a case of a 60-year-old man who developed inferior ST-segment elevation myocardial infarction within 30 minutes of a normal DSE. The patient was found to have a 99% in-stent restenosis in the mid-right coronary artery with significant thrombosis for which successful percutaneous coronary intervention (PCI) was performed. Acute coronary syndrome after a normal DSE has been rarely reported in the literature. The reported cases were found to have obstructive or non-obstructive coronary plaques with overlying thrombus, which suggests plaque destabilisation and rupture as the possible underlying mechanism behind coronary occlusion.

Evaluation of serum sST2 and sCD40L values in patients with microvascular angina

OBJECTIVES

Coronary microvascular dysfunction plays a major role in the pathogenesis of microvascular angina (MVA). Along with endothelial dysfunction, microvascular atherosclerosis and inflammation seem to contribute to the development of coronary microvascular dysfunction. Serum soluble ST2 (sST2) and serum soluble CD40 ligand (sCD40L) are two biomarkers associated with inflammation and atherosclerosis. The aim of this study was to investigate the role of these biomarkers in the pathogenesis of MVA and determine their possible association with coronary microvascular dysfunction.

METHODS

A total of 152 patients were included in the study. Ninety-one patients with MVA {median age 56 years (40-79), of which 55 are women} and sixty-one controls {median age 52 (38-76), of which 29 are women} were included in the study. Serum concentration of sST2 and sCD40L were measured with a commercially available ELISA kit.

RESULTS

Serum sST2 (median 13.6 ng/ml; interquartile range (IQR), 3.5-63.8 ng/ml vs median 10.6 ng/ml; IQR, 2.9-34.2 ng/ml, p < 0.0005) and sCD40L (median 5.3 ng/ml; IQR, 0.5-20.6 ng/ml vs median 2.2 ng/ml; IQR, 0.7-10.8 ng/ml, p < 0.0005) were significantly higher in patients with MVA compared to controls. Analysis of the associations between these biomarkers and potential contributors of MVA revealed that serum sST2 showed a positive correlation with LDL-cholesterol (r = 0.19, p = 0.016) and serum sCD40L concentrations correlated positively with hs-CRP (r = 0.22, p = 0.005). In logistic regression analysis, sCD40L and hs-CRP but not sST2 were found to be significantly associated with MVA.

CONCLUSION

Higher serum concentrations of sST2 and sCD40L in MVA patients may be associated with inflammatory activation and coronary microvascular dysfunction. Larger studies are required for understanding their role in the pathogenesis of inflammatory and possibly fibrotic process in MVA patients.

Incidence and predictors of acute coronary syndrome within a year following a negative stress test-a false sense of security: is routine screening any useful?

One of the major issues in management of the acute coronary syndrome (ACS) is classification of patients with atypical presentation who have low risk of having a coronary episode at presentation. There have been multiple studies on the stratification of high risk patients and medical management of such cases, however, there is a sub-class of patients who do not fit any category. In this paper, we have looked at the current literature on stratification of patients based on the study tools available and the risk of having a coronary episode during the following year. In our overview, we have found that the current methods in place namely, cardiac stress test and stress echocardiogram have a good prognostic factor in terms of mortality in the next one year and can safely stratify the patients at low risk when correlated with clinical presentation and laboratory studies. However, such data are limited for computerized tomography or magnetic resonant imaging and their application might be limited due to accessibility and cost of studies. Current guidelines for classification of high risk patient do an excellent job and we believe that proper application of stress tests together with other imaging modalities together with laboratory, clinical judgment, and proper use of medical management can help with safe discharge of patients from the emergency department (ED) and reduction of burden from healthcare.

Platelets and Cardiovascular Disease

Platelets play an important, but often under-recognized role in cardiovascular disease. For example, the normal response of the platelet can be altered, either by increased pro-aggregatory stimuli or by diminished anti-aggregatory substances to produce conditions of increased platelet activation/aggregation and occur in active cardiovascular disease states both on a chronic (e.g. stable angina pectoris) and acute basis (e.g. acute myocardial infarction). In addition, platelet hyperaggregability is also associated with the risk factors for coronary artery disease (e.g. smoking, hypertension, and hypercholesterolaemia). Finally, the utility of an increasing range of anti-platelet therapies in the management of the above disease states further emphasizes the pivotal role platelets play in the pathogenesis of cardiovascular disease. This paper provides a comprehensive overview of the normal physiologic role of platelets in maintain homeostasis, the pathophysiologic processes that contribute to platelet dysfunction in cardiovascular disease and the associated role and benefits of anti-platelet therapies.

Acute Anteroseptal Myocardial Infarction after a Negative Exercise Stress Test

A myocardial infarction is a rare complication which can occur after an exercise stress test. We report a 48-year-old male who was referred to the Mildura Cardiology Practice, Victoria, Australia, in August 2014 with left-sided chest pain. He underwent an exercise stress test which was negative for myocardial ischaemia. However, the patient presented to the Emergency Department of the Mildura Base Hospital 30 minutes after the test with severe retrosternal chest pain. An acute anteroseptal ST segment elevation myocardial infarction was observed on electrocardiography. After thrombolysis, he was transferred to a tertiary hospital where coronary angiography subsequently revealed significant left anterior descending coronary artery stenosis. Thrombus aspiration and a balloon angioplasty were performed. The patient was discharged three days after the surgical procedure in good health.

Effect of physical training on indices of platelet aggregation and fibrinogen concentration in patients with chronic heart failure

OBJECTIVE

The aim of this study was to determine the effect of long-term physical load on the changes in the fibrinogen concentration and platelet aggregation.

MATERIAL AND METHODS

Platelet aggregation was investigated in 144 patients while fibrinogen concentration in 138 patients with CHF. The patients were divided into the groups of the trained patients and the controls and were investigated as follows: on admission to the hospital (stage 1); after treatment in the hospital (stage 2); after 3 months (stage 3); after 6 months (stage 4); and after 1 year (stage 5). The indices were investigated before and after physical load.

RESULTS

It was determined that fibrinogen concentration significantly increased after physical load in all the treatment stages in both groups of the patients (P=0.045). In the course of the treatment, fibrinogen concentration gradually decreased in the group of the trained patients (P=0.02). Platelet aggregation investigated with ADP significantly increased after physical load in all the stages in both groups of the patients and decreased during the different investigation stages in the groups of the untrained (P=0.02) and trained patients. Platelet aggregation investigated with ADR consistently decreased before physical load during the different investigation stages in the groups of the trained (difference is not significant) and untrained patients (P=0.02).

CONCLUSIONS

Physical training reduces fibrinogen concentration in patients with CHF. It remains unclear whether physical training can have an effect on the decrease in platelet aggregation in patients who have long-term physical training applied.

Effects of Physical (In)activity on Platelet Function

As platelet activation is closely related to the liberation of growth factors and inflammatory mediators, platelets play a central role in the development of CVD. Virtually all cardiovascular risk factors favor platelet hyperreactivity and, accordingly, also physical (in)activity affects platelet function. Within this paper, we will summarize and discuss the current knowledge on the impact of acute and habitual exercise on platelet function. Although there are apparent discrepancies regarding the reported effects of acute, strenuous exercise on platelet activation, a deeper analysis of the available literature reveals that the applied exercise intensity and the subjects' cardiorespiratory fitness represent critical determinants for the observed effects. Consideration of these factors leads to the summary that (i) acute, strenuous exercise can lead to platelet activation, (ii) regular physical activity and/or physical fitness diminish or prevent platelet activation in response to acute exercise, and (iii) habitual physical activity and/or physical fitness also favorably modulate platelet function at physical rest. Notably, these effects of exercise on platelet function show obvious similarities to the well-recognized relation between exercise and the risk for cardiovascular events where vigorous exercise transiently increases the risk for myocardial infarction and a physically active lifestyle dramatically reduces cardiovascular mortality.

Exercise-induced changes in inflammatory processes: Implications for thrombogenesis in cardiovascular disease

Sedentary lifestyle is a risk factor and a strong predictor for chronic disease and premature death. Low-grade inflammation has been proved a key player in the pathogenesis of cardiovascular disease. Inflammatory processes have been also involved in maintaining the balance between coagulation and fibrinolysis. In addition, an inverse linear dose-response relation between physical activity and mortality risks has also been reported. However, the favorable effects of structured exercise programs and the independent contribution of physical activity to cardiovascular risk are still under investigation. In response to heavy exercise, interleukin-6 (IL-6) is secreted by contracting skeletal muscles, followed by an acute reactant release of C-reactive protein (CRP). Both CRP and IL-6 can stimulate monocyte tissue factor production, provoke platelet hyperreactivity, promote fibrinogen biosynthesis, and enhance microparticle formation and erythrocyte aggregability, thus triggering prothrombotic state. By contrast, regular exercise and physical activity are protective against all-cause mortality through suppressing pro-inflammatory cytokine production, enhancing anti-inflammatory mediators and antioxidant development, and promoting fibrinolytic activity. Low-load resistance exercise also plays an advantageous role in thrombogenesis by reducing inflammatory processes and potentiating fibrinolytic features. In the present review article, we provide an overview of the impact of different modes and intensities of physical activity on vascular inflammation and thrombogenesis.

The relationship between fractional flow reserve, platelet reactivity and platelet leukocyte complexes in stable coronary artery disease

BACKGROUND

The presence of stenoses that significantly impair blood flow and cause myocardial ischemia negatively affects prognosis of patients with stable coronary artery disease. Altered platelet reactivity has been associated with impaired prognosis of stable coronary artery disease. Platelets are activated and form complexes with leukocytes in response to microshear gradients caused by friction forces on the arterial wall or flow separation. We hypothesized that the presence of significantly flow-limiting stenoses is associated with altered platelet reactivity and formation of platelet-leukocyte complexes.

METHODS

One hundred patients with stable angina were studied. Hemodynamic significance of all coronary stenoses was assessed with Fractional Flow Reserve (FFR). Patients were classified FFR-positive (at least one lesion with FFR≤0.75) or FFR-negative (all lesions FFR>0.80). Whole blood samples were stimulated with increasing concentrations of ADP, TRAP, CRP and Iloprost with substimulatory ADP. Expression of P-selectin as platelet activation marker and platelet-leukocyte complexes were measured by flowcytometry. Patients were stratified on clopidogrel use. FFR positive and negative patient groups were compared on platelet reactivity and platelet-leukocyte complexes.

RESULTS

Platelet reactivity between FFR-positive patients and FFR-negative patients did not differ. A significantly lower percentage of circulating platelet-neutrophil complexes in FFR-positive patients and a similar non-significant decrease in percentage of circulating platelet-monocyte complexes in FFR-positive patients was observed.

CONCLUSION

The presence of hemodynamically significant coronary stenoses does not alter platelet reactivity but is associated with reduced platelet-neutrophil complexes in peripheral blood of patients with stable coronary artery disease.

Effect of live-fire training drills on firefighters' platelet number and function

BACKGROUND

The leading cause of line-of-duty death among firefighters is sudden cardiac events. Platelets play a critical role in the formation of an occlusive thrombus during an ischemic event.

OBJECTIVE

The purpose of this study was to examine the acute effect of firefighting on platelet number and aggregability.

METHODS

Apparently healthy male firefighters (N = 114; age 29.4 ± 7.8 years) participated in 18 minutes of simulated firefighting activity in a training structure that contained live fires. Blood samples were obtained before and after simulated firefighting activity and analyzed for complete blood cell count (CBC), chemistry, and platelet number and function. Platelet function was measured using a PFA-100 analyzer to assess platelet aggregability.

RESULTS

As expected, performing firefighting activity resulted in significant increases in heart rate (75 b·min(-1)) and core temperature (0.7 °C), and significant changes in blood chemistry values. The most important finding in this study is that 18 minutes of simulated firefighting caused a 24% increase in platelet number and a significant increase in platelet aggregability.

CONCLUSIONS

Firefighting resulted in a significant increase in platelet number and aggregability, indicating that even short bouts of firefighting can increase thrombotic potential in apparently healthy firefighters.

Elevated circulating soluble form of CD40 ligand in patients with cardiac syndrome X

BACKGROUND

The presence of effort induced angina, positive exercise stress test responses and angiographically normal coronary arteries defines cardiac syndrome X (CSX). Its pathogenesis, although mostly attributed to endothelial dysfunction and coronary microcirculation abnormalities, is incompletely understood. The soluble CD40 ligand (sCD40L) has multiple autocrine, paracrine and endocrine actions that may lead to endothelial dysfunction and atherothrombosis. We sought to investigate the relationship among sCD40L levels and ischemic burden in patients with CSX and whether sCD40L levels are increased in patients with CSX compared to control subjects.

METHODS

We assessed 30 prospectively enrolled patients with CSX and 28 apparently healthy subjects matched for coronary risk factors. All CSX patients and control subjects underwent myocardial perfusion scintigraphy. The summed difference score is taken to be an index of ischemic burden. This was classified as mildly, moderately and severely abnormal. White blood cells, sCD40L and C-reactive protein (CRP) concentrations were measured at peak exercise.

RESULTS

At peak exercise, sCD40L levels were significantly greater in CSX patients than in the control group (P=0.008). Similarly, white blood cell count and CRP levels were higher in patients with CSX than in normal controls (P=0.02). After multivariable adjustment, sCD40L (P=0.03) was the only independent predictor of severe ischemic burden in CSX patients.

CONCLUSIONS

The present study showed for the first time that sCD40L is associated with ischemic burden in patients with CSX. The potential role of this inflammatory molecule in the pathogenesis of CSX deserves investigation in future studies.

Predictors of exercise-induced platelet reactivity in patients with chronic stable angina

OBJECTIVE

Previous studies have shown that exercise increases platelet reactivity in patients with coronary artery disease (CAD). However, the response of platelet reactivity to exercise is considerably variable and its predictors are poorly known.

METHODS

We studied 214 consecutive patients (age 61.9 +/- 9 years, 167 men) with stable angina and obstructive coronary artery disease. All patients underwent a symptom-limited treadmill exercise stress test. Venous blood samples were collected before and at peak exercise. Platelet reactivity was assessed by the platelet function analyzer system as the time for flowing whole blood to occlude a collagen-adenosine diphosphate ring (closure time: shorter times = higher reactivity). Both closure time at peak exercise and the exercise-induced change in closure time from rest were assessed as an expression of exercise-related platelet reactivity.

RESULTS

Closure time decreased significantly with exercise in the whole population (from 95.9 +/- 22 to 81.2 +/- 18 s, P < 0.001). The only variable significantly associated with closure time at peak exercise was hematocrit (P = 0.003). Basal systolic blood pressure (P = 0.023) and lack of nitrate use (P = 0.03), on the contrary, were the only variables significantly associated with increased exercise-induced closure time change. Peak hematocrit maintained an independent association with peak closure time in multivariable analysis, although the correlation was mild. No variable, on the contrary, was associated with exercise-induced platelet reactivity after correction for basal closure time values at multivariable analyses.

CONCLUSION

Among stable coronary artery disease patients, platelet reactivity after exercise cannot be reliably predicted by several common clinical and laboratory variables.

Treadmill exercise in claudicants on aspirin results in improved antioxidant status but only minimal platelet activation

The consequence of exercise on platelets remains controversial and adverse effects may result from repeated ischaemia reperfusion injury. We investigated platelet activation (platelet P-selectin (PS), and activated glycoprotein (Gp) IIb/IIIa), platelet-monocyte aggregates (PMA) and total plasma antioxidant status (TPAS) in claudicants after exercise. Twenty claudicants, taking 75 mg of aspirin daily, were subjected to repeated treadmill testing (3 km/h, 10% inclination). Blood was sampled before and after exercise. Activated GpIIb/IIIa, PS and PMA were quantified with flow cytometry. TPAS was quantified using a decolourisation assay. Percent positive cells for PS (pre-exercise 3.76% vs. 40 min post-exercise 4.10%; P < 0.05) and platelet-monocyte aggregates (pre-exercise: 25.31% vs. 40 min post-exercise 26.99%; P < 0.05) were significantly higher after exercise. Relative median fluorescence (RMF) for activated GpIIb/IIIa was significantly higher 40 min after exercise (pre-exercise: 3.04 vs. 40 min post-exercise: 4.01; P < 0.05). TPAS was significantly higher post-exercise (pre-exercise: 1.31 mmol/l vs. 1 min post-exercise: 1.40 mmol/l and 40 min post-exercise: 1.38 mmol/l; P < 0.01). Following moderate exercise, 'aspirin treated claudicants' show marginal platelet activation, PMA formation and a favourable improvement in antioxidant status. Further studies are required to assess the effect of additional antiplatelet agents and the significance of platelet-monocyte interactions. The possibility that aspirin contributes to the TPAS changes following exercise needs to be investigated.

Adenosine inhibition of adenosine diphosphate and thrombin-induced monocyte-platelet aggregates in cardiac syndrome X

INTRODUCTION

We previously showed that platelet reactivity at rest is increased in patients with cardiac syndrome X (CSX), but that exercise reduces platelet reactivity in these patients. Adenosine was suggested to be involved in this phenomenon. In this study we investigated the effect of adenosine on adenosine diphosphate (ADP) and thrombin-induced platelet reactivity in CSX patients.

MATERIALS AND METHODS

We studied 15 CSX patients and a control group of 15 healthy subjects. Formation of monocyte-platelet (MONO-PLT) aggregates in vitro was assessed by flow cytometry: 1) at baseline; 2) after ADP (10(-7) M) stimulation alone; 3) after ADP stimulation in presence of adenosine (10(-5) M); 4) after thrombin (10(-11) M) stimulation alone; 5) after thrombin stimulation in presence of adenosine.

RESULTS

In non stimulated samples there were no relevant differences between the two groups in cytometry variables. Compared to controls, ADP induced a higher increase in MONO-PLT aggregates in CSX patients (P < 0.01), which was significantly inhibited by adenosine (P < 0.01). Thrombin also induced a greater increase in MONO-PLT aggregates in CSX patients (P < 0.001), which was also significantly blunted by adenosine. Similar trends were observed for platelet CD41 (glycoprotein IIb-IIIa) receptor and for monocyte receptors CD142 ad CD162 in MONO-PLT aggregates.

CONCLUSIONS

In CSX patients platelet reactivity is increased at rest, compared to healthy controls. Pre-incubation with adenosine reduces the agonist-induced platelet hyper-reactivity in these patients, suggesting that adenosine may be involved in the reduction of platelet reactivity observed in CSX patients after exercise in our previous study.

The immediate effect of aerobic exercise on haemostatic parameters in patients with recently diagnosed mild to moderate essential hypertension

BACKGROUND

Exercise is frequently recommended for the treatment of patients with arterial hypertension. Previous studies have shown an enhanced coagulation state after exercise. Our study investigates the alterations observed after a single session of submaximal aerobic exercise concerning coagulation, fibrinolysis, platelet activation as well as endothelial function in patients with recently diagnosed essential hypertension.

METHODS

Twenty non-diabetic patients with recently diagnosed essential hypertension participated in a 45 min submaximal exercise test on a bicycle ergometer. Blood samples were drawn before and after exercise in order to determine parameters of coagulation activation (Prothrombin time [PT], activated Partial Thromboplastin time [aPTT], fibrinogen, D-Dimers, prothrombin fragments 1 + 2 [PF1+2], thrombin-antithrombin III complex [TAT] and factors VII, VIII and XII), platelet activation (Platelet count, Platelet factor 4 [PF4] and beta-thromboglobulin [beta-TG]), fibrinolysis activation (Plasmin-a(2) antiplasmin complex, PAP) and endothelial function (soluble Thrombomodulin [sTM] and von Willebrand factor [vWf]). Soluble P-selectin served as a marker for endothelial and platelet activation.

RESULTS

All patients completed the exercise test. aPTT (P < 0.001) and factor VII (P = 0.01) significantly decreased while PT (P = 0.04), fibrinogen (P = 0.008), factor VIII (P < 0.001), platelet count (P = 0.002) and beta-TG levels (P = 0.01) significantly increased as a result of exercise. Compared to baseline there was an 11% increase in TAT (P = 0.04) and a 28% increase in PAP (P < 0.001) at peak exercise. One hour post exercise, there was a 43% increase in PAP whereas TAT levels became similar to those at baseline. Additionally vWf (P = 0.01) and sP-selectin (P = 0.02) levels significantly increased throughout the exercise protocol.

CONCLUSIONS

Patients with recently diagnosed and never treated mild to moderate essential hypertension undergoing submaximal aerobic exercise present evidence of enhanced fibrinolysis compared with a mild increase of coagulation indices. However, whether there is a favourable effect of exercise on fibrinolysis over coagulation and/or endothelial involvement during exercise needs to be further investigated.

Relationship between changes in platelet reactivity and changes in platelet receptor expression induced by physical exercise

INTRODUCTION

In previous studies we have consistently shown a significant increase of platelet reactivity after exercise in patients with obstructive coronary artery disease (CAD). We also observed a significant individual variability in the response to exercise of platelet reactivity in these patients. Whether exercise-induced changes in platelet reactivity correlate with changes in platelet membrane receptors in patients with CAD is unknown.

METHODS

We studied 26 patients with stable CAD and 10 matched healthy controls who underwent a symptom-limited treadmill exercise stress test. Venous blood samples were collected at rest and within 5 min of peak exercise. Platelet reactivity was measured by the PFA-100 method as time to occlude (closure time, CT) a ring coated with collagen/adenosine diphosphate (C/ADP). Platelet expression of glycoprotein (GP) IIb/IIIa, in both global (CD41) and active form (PAC-1), and P-selectin (CD62P) and formation of leukocyte-platelet aggregates were assessed by flow cytometry.

RESULTS

After exercise CT did not change in controls (85.4+/-12 to 84.0+/-9 s, p=0.37), whereas it decreased in CAD patients (98.8+/-24 to 91.4+/-25 s, p<0.001). After exercise, CD41 and PAC-1 platelet expression increased significantly in CAD patients (p=0.04 for both), but not in controls (p=0.39 and p=0.98, respectively). To evaluate the relationship between the response to exercise of platelet reactivity and of platelet receptor expression, CAD patients were divided into two groups: CAD group 1 (16 patients, decrease in CT >5 s after exercise) and CAD group 2 (10 patients no increase in platelet reactivity after exercise). CD41 and PAC-1 expression increased in CAD group 1 (p=0.008 and p=0.026, respectively) but not in CAD group 2 (p=0.39 and p=0.50, respectively). No significant differences were observed between the 2 groups for changes in CD62P and leukocyte-platelet aggregates.

CONCLUSIONS

Our data show that, in patients with stable CAD, an increased platelet reactivity to C/ADP stimulation after exercise, as assessed by the PFA-100 method, is specifically associated with an increased expression of platelet GP IIb/IIIa receptor.

The role of exercise on platelet aggregation in patients with stable coronary artery disease: exercise induces aspirin resistant platelet activation

OBJECTIVES

The aim of our study was to determine the relation between exercise stress test and aspirin resistance in patients with stable coronary artery disease.

BACKGROUND

Clinically aspirin resistance is defined as having thrombotic and embolic cardiovascular events despite regular aspirin therapy.

METHODS

We studied platelet functions of 62 patients with stable coronary artery disease and 20 subjects with normal coronary arteries by Platelet Function Analyzer (PFA-100, Dade Behring, Germany) at rest and after exertion with collagen and/or epinephrine (Col/Epi) and collagen and/or ADP cartridges. Closure time (CT)<186 seconds was defined as aspirin resistance with Col/Epi cartridges of PFA-100. Symptom limited treadmill stress test (protocol of Bruce) was performed with Oxford Streslink TD-1 system.

RESULTS

8 (12.9%) patients were aspirin resistant by PFA-100 (CT<186s despite regular aspirin therapy) at rest. At the first minute of the recovery period of exercise stress test 14 (22.5%) patients were aspirin resistant by PFA-100. CTs with Col/ADP were respectively 89+/-6 s (83--100s) and 89+/-5 s (82--104s) at rest and after exercise (p=0.107). 20.3% (11/54) of patients known as in vitro aspirin sensitives at rest had shorter CTs and 11.1% (6/54) had aspirin resistance after exercise (p=0.004). There was no statistically significiant difference in platelet functions in the control group after exertion.

CONCLUSION

We conclude that 11.1% of in vitro aspirin sensitive subjects at rest had aspirin resistance after exercise by PFA-100. In some individuals, exercise induced platelet activation is aspirin insensitive at usual antiplatelet doses. We need further clinical trials to optimize antiplatelet therapy in patients with coronary artery disease.

Aggregation and Activation of Blood Platelets in Exercise and Training

This article presents an overview of the progress that has been made in recent years in our understanding of the interaction between exercise and platelets in health and disease. Although platelets are important in normal haemostasis, recent evidence emphasises the pivotal role of abnormal platelet function in acute coronary artery diseases, myocardial infarction, unstable angina and stroke. In light of the positive health benefits of exercise, interest has been heightened on the association between exercise and platelet aggregation and function, not only in normal healthy subjects but also in patients. However, the study of exercise effects on blood platelets are highly contentious because of the fact that the analytical methods employed to study platelets are bedevilled by numerous methodological problems. While exercise effects on platelet aggregation and function in healthy individuals have been extensively examined, the evidence reported has been conflicting. Somewhat less contradictory are the results generated from studies in patients with coronary heart disease, as the preponderance of evidence available would strongly suggest that platelet aggregation and function are increased with exercise. Several drugs are known to influence platelet aggregation and function, the most examined among these medications is aspirin (acetylsalicylic acid). However, aspirin appears to be ineffective to attenuate exercise-induced increases in platelet aggregation and activation. Few studies are available on the effect of training on blood platelets and the exact effects of exercise training on platelet activation and function is not as yet known. This lack of information makes further studies particularly important, in order to clarify whether there are favourable effects of exercise training on platelet aggregation and function in health and disease.

Platelet reactivity in response to mental stress in syndrome X and in stable or unstable coronary artery disease

INTRODUCTION

Previous studies showed differences in platelet reactivity in response to exercise in patients with syndrome X (SX) and those with obstructive coronary artery disease (CAD). In this study, we investigated whether similar differences could be detectable in response to a mental stressful stimulus.

MATERIALS AND METHODS

We studied 30 SX patients (60+/-8 years, 8 men), 20 patients with stable angina and angiographically documented CAD (SA, 66+/-8 years, 14 men), and 11 patients with unstable angina (UA, 67+/-8 years, 6 men). A control group of 22 healthy controls (50+/-7 years, 5 men) was also studied. All subjects underwent a mathematical mental stress test (MST) consisting of rapid consecutive subtractions of number 7 for a period of 5 min. A venous blood sample was collected at baseline and immediately after MST. Platelet reactivity was measured on flowing blood as time necessary to occlude a ring coated with collagen-adenosine diphosphate (ADP; closure time, CT), using the platelet function analyzer (PFA-100) system.

RESULTS

At rest, CT was lower in UA patients (87+/-19 s) compared to controls (109+/-24 s, p=0.02) and SA patients (105+/-37 s, p=0.055), and also tended to be lower in SX patients (96+/-18 s) compared to controls (p=0.07). The CT response to MST differed significantly among groups (p=0.0009). At peak MST, CT did not change in controls (110+/-27 s, p=0.88), whereas it decreased in SA patients (96+/-29 s, p=0.003) and tended to decrease in UA patients (82+/-15 s, p=0.25). In contrast, a significant increase in CT with MST was shown in SX patients (103+/-21 s, p=0.007).

CONCLUSIONS

Platelet reactivity is increased by MST in patients with CAD, whereas it paradoxically decreases in SX patients, which may constitute a protective effect against stress-induced events in these patients.

Reduction of daily life ischaemia by aspirin in patients with angina: underlying link between thromboxane A2 and macrophage colony stimulating factor

OBJECTIVES

To evaluate whether aspirin reduces the incidence and frequency of daily life myocardial ischaemia in a cohort of patients with chronic stable coronary artery disease.

SETTING

Tertiary referral centre.

METHODS

60 patients with chronic stable coronary artery disease underwent 48 hour Holter monitoring to assess the incidence and frequency of daily life myocardial ischaemia. Those with myocardial ischaemia (40/60) entered a double blind, crossover trial of aspirin (300 mg/day for three weeks) versus placebo. After each treatment arm, 48 hour Holter monitoring was repeated and urinary thromboxane (Tx) B2, 11-dehydro-TxB2, plasma prothrombin fragment F1+2, macrophage colony stimulating factor (MCSF), and interleukin (IL)-6 were measured.

RESULTS

Aspirin reduced the total number and duration of ischaemic episodes from 339 to 251 and from 1765 to 1365 minutes, respectively (p < 0.01 for both). TxB2 was also reduced from 0.2 to 0.1 ng/mg creatinine, 11-dehydro-TxB2 from 3.3 to 1.3 ng/mg creatinine, F1+2 from 1.5 to 1.2 nmol/l, MCSF from 991 to 843 pg/ml, and IL-6 from 3.5 to 2.9 pg/ml (p < 0.05 for all). 11-dehydro-TxB2 excretion with and without aspirin was related to MCSF concentrations (p < 0.01), and the percentage reduction of MCSF by aspirin was related to the reduction of 11-dehydro-TxB2 (p < 0.05) and the reduction of the ischaemic burden compared with placebo (p < 0.05).

CONCLUSIONS

In patients with daily life ischaemia, aspirin reduces the incidence and frequency of ischaemic episodes as well as the systemic concentrations of haemostatic/inflammatory markers. Aspirin may prevent transient coronary flow reductions through platelet, thrombin, and cytokine inhibition.

In vitro aspirin resistance detected by PFA-100 closure time: pivotal role of plasma von Willebrand factor

The in vitro closure time (CT), determined by the Platelet Function Analyzer (PFA-100), is used to monitor patients treated with aspirin. A relatively high percentage of in vitro aspirin resistance was reported despite an adequate inhibition of platelet response to arachidonic acid and we investigated whether high plasma levels of von Willebrand factor ristocetin cofactor activity (vWF:RCo) may contribute to this profile. Platelet aggregation test, CT [collagen adrenaline (CEPI-CT) and collagen adenosine 5'-diphosphate (ADP) (CADP-CT)], and vWF:RCo levels were evaluated in 55 consecutive patients receiving aspirin (75-250 mg/d) versus 32 untreated control subjects. All the aspirin-treated patients showed platelet aggregation responses that reflected the aspirin intake. However, CT data analysis enabled aspirin good-responder (GR) and aspirin bad-responder (BR) patients to be identified. All GR group subjects (n = 27), had a CEPI-CT and a CADP-CT longer than 300 s and 96 s respectively. The BR group (n = 28) had CEPI-CT values below 200 s and all CADP-CT were in the normal range (77 +/- 19 s). Interestingly, the BR plasma vWF:RCo levels were significantly higher (159 +/- 43%) than those of the GR group (121 +/- 34%) (P < 0.01), which were similar to control values (114 +/- 31%). A negative correlation between vWF:RCo and CT values was established. We demonstrate that in vitro aspirin-resistance, revealed by PFA-100 CT prolongation failure, is correlated to increased plasmatic vWF:RCo levels, reinforcing its particular importance in PFA-100 cartridges performance.

Exercise and Training Effects on Blood Haemostasis in Health and Disease

In recent years, the dysfunction of the haemostatic system in relation to the clinical complications from arterioscleroses and cardiovascular diseases has become more recognised. Blood coagulation and fibrinolysis comprise two important physiological systems, which are regulated by a balance between activators and inhibitors. Activation of blood coagulation is associated with accelerated clot formation, whereas activation of blood fibrinolysis enhances the breakdown of the blood clot. Available evidence suggests that strenuous exercise induces activation of blood coagulation with simultaneous enhancement of blood fibrinolysis. Although the responses of blood coagulation and fibrinolysis appear to be related to the exercise intensity and its duration, recent reports suggest that moderate exercise intensity is followed by activation of blood fibrinolysis without concomitant hyper-coagulability, while very intense exercise is associated with concurrent activation of blood coagulation and fibrinolysis. Similar to blood coagulation and fibrinolysis, systemic platelet-related thrombogenic factors have been shown to be involved in the initiation and progression of atherogenesis and plaque growth. Although exercise effects on platelet aggregation and function in healthy individuals have been examined, the results reported have been conflicting. However, for patients with coronary heart disease, the balance of evidence available would strongly suggest that platelet aggregation and functions are increased with exercise. Few studies are available concerning the influence of training on blood coagulation and fibrinolysis and the exact effects of exercise training on the equilibrium between blood coagulation and fibrinolysis is not as yet known. Although the effects of physical training on platelets have been briefly investigated, available meagre evidence suggests that exercise training is associated with favourable effects on platelet aggregation and activation in both men and women.

Relation between platelet response to exercise and coronary angiographic findings in patients with effort angina

BACKGROUND

Platelet reactivity is increased by exercise in patients with obstructive coronary artery disease (CAD) but not in patients with syndrome X. In this study, we prospectively investigated whether the platelet response to exercise might help distinguish, among patients with angina, those with obstructive CAD from those with normal coronary arteries (NCAs).

METHODS AND RESULTS

Venous blood samples were collected before and 5 minutes after exercise from 194 consecutive patients with stable angina. Platelet reactivity was measured by the platelet function analyzer (PFA)-100 system as the time for flowing whole blood to occlude a collagen-adenosine diphosphate ring (closure time). Coronary angiography showed CAD in 163 patients (84%) and NCA in 31 patients (16%). Baseline closure time was shorter in NCA patients (78.0+/-16 versus 95.5+/-23 seconds, P<0.0001). With exercise, closure time decreased in CAD patients (-15.5 seconds; 95% confidence limits [CL], -13.0 to -18.0 seconds; P<0.0001), but increased in NCA patients (12.5 seconds; 95% CL, 7.4 to 17.7 seconds; P=0.0004). An increase in closure time with exercise > or =10 seconds had 100% specificity and positive predictive value for NCAs. Similarly, a decrease > or =10 seconds had 100% specificity and positive predictive value for CAD. A closure time change (increase or decrease) > or =10 seconds allowed a correct classification of 55% of all patients.

CONCLUSIONS

Among patients with stable angina, the response of platelet reactivity to exercise was predictive of normal or stenosed coronary arteries at angiography. Specifically, an increase in closure time with exercise > or =10 seconds was invariably associated with the presence of NCA.

The effect of submaximal exercise on platelet aggregation during late follicular and midluteal phases in women

INTRODUCTION

The key role of platelets in the pathogenesis of atherosclerosis prompted considerable interest on the effect of physical exercise on platelets. Due to probable menstrual cycle variations, only a limited number of investigations have studied the effect of exercise on platelets in women. The study was undertaken to determine the effect of acute submaximal exercise on platelet aggregation and thromboxane A(2) (TxA(2)) formation in females during their late follicular and midluteal phases.

MATERIALS AND METHODS

Twelve healthy, sedentary, female volunteers performed 15 min of cycling exercise at a workload that increased their heart rate to 75% of maximal in two phases of the menstrual cycle. The maximal rate of ADP and collagen-induced platelet aggregation was evaluated on citrated whole blood using the impedance technique. Thrombin-induced thromboxane A(2) formation was evaluated by the measurement of thromboxane B(2) (TxB(2)) level by enzyme-linked immunoassay.

RESULTS AND CONCLUSION

No significant difference was found between maximal rates of platelet aggregation measured in the different phases of menstrual cycle. Collagen-induced platelet aggregation and platelet count increased significantly after the exercise in both late follicular and midluteal phases (p<0.05). ADP-induced platelet aggregation did not change due to the exercise during the two phases of menstrual cycle. The thromboxane B(2) level measured in the midluteal phase was significantly higher than that measured in late follicular phase at rest. It was significantly increased after the exercise in late follicular phase while no significant difference was found between pre-exercise and postexercise levels in the midluteal phase. The differences in thromboxane A(2) formation were pointed out in the changes in platelet reactivity status. The inhibitory systems for platelets need further investigations. Our findings support the idea that menstrual variations do not have pronounced and acute effects on both platelet aggregation and response of platelets to acute exercise.

Resistance to aspirin in vitro at rest and during exercise in patients with angiographically proven coronary artery disease

BACKGROUND

Acetylsalicylic acid, or aspirin, is widely used in secondary prevention of coronary artery diseases, but the inhibition of platelet aggregation is not uniform in all individuals.

OBJECTIVE

To investigate the prevalence of aspirin resistance at rest and during exercise in coronary artery disease patients.

MATERIALS AND METHODS

Fifty patients with stable coronary artery disease were prospectively studied. All patients received aspirin (75-300 mg/day for >1 month) and no other antiplatelet therapy. Aspirin resistance was studied, at rest and immediately after a stress test, using the standardized platelet function analyzer (PFA-100(R), Dade-Behring). Aspirin resistance was defined as a normal collagen/epinephrine closure time (<186 s).

RESULTS

Ten patients (20%) were aspirin-resistant at rest. Out of the 40 patients who were aspirin-sensitive at rest, 9 (22%) were aspirin-resistant immediately after the exercise stress test. There were no differences in aspirin sensitivity regarding gender, age, diabetes, hypertension, dyslipidemia, platelet count, medical treatment or number of the coronary arteries involved.

CONCLUSIONS

Aspirin resistance is detected, at rest, in 20% of our patients with stable coronary artery disease. Aspirin treatment does not seem to protect against exercise-induced platelet activation in 22% of such patients, despite aspirin sensitivity at rest.

To anticoagulate or not to anticoagulate patients with cardiomyopathy

The current published literature does not indicate whether the long-term effect of anticoagulant or antiplatelet therapy contributes to mortality reduction in patients with LV dysfunction. Evaluating patients for personal risk for emboli or for ischemic coronary artery events may influence the choice of therapies. As more is learned about the mechanisms of drug effects in different populations, physicians may be better able to direct appropriate therapies. Until that time, one must weigh the risks and benefits of each drug alone and in combination. In NYHA class IV patients, the risk for thrombosis owing to spontaneous clotting increases as does the adverse potential of warfarin and the adverse effects of inhibiting prostaglandin mediated vasodilation by aspirin. In NYHA class I and II patients, the quality of life and convenience of multidrug therapy is weighed against the devastating effect of a major stroke. In less symptomatic patients, the long-term risk for acute coronary events may be higher than previously identified. This would suggest that all patients with depressed LV function should be on some type of antiplatelet or anticoagulant therapy. The current WATCH study will provide much needed information about the outcome differences between these agents. Conclusions based on available data include the following: Heart failure is increasing in incidence and prevalence. Atherosclerotic disease is an important causative factor for the development of heart failure or may be a comorbid condition in these patients. There is a measurable rate of stroke in patients with heart failure, although the cause of death in large studies is more often owing to sudden death or progressive heart failure. Sudden death may be from new ischemic events, asystole, or from ventricular tachyarrhythmias. In patients with heart failure, not all strokes are cardioembolic in origin. The benefits and risks of warfarin may be increased as the EF worsens or heart failure functional class declines. The interactions of aspirin and ACE inhibitors have been best evaluated for the hemodynamic effects. There may be additional factors hitherto not studied. The hemodynamic effect of ACE inhibitors may be more important in NYHA classes III and IV than in less symptomatic patients. Warfarin use has clear indications for patients in atrial fibrillation with mechanical prosthetic valves, in hypercoagulable states, and with a previous history of embolization. Aspirin is inexpensive and commonly available, but its use must be evaluated and articulated by the prescribing physician. The current multicenter prospective trials will provide much needed guidance on this subject. The ongoing trials do not have a placebo arm, however, indicating a consensus among clinicians that patients with cardiomyopathy should be on an antiplatelet or anticoagulant drug until further data emerge.