A Preliminary Study on the Effects of Exercising to Maximum Walking Distance on Platelet and Endothelial Function in Patients with Intermittent Claudication

Does Exercise Influence the Susceptibility to Arterial Thrombosis? An Integrative Perspective

Arterial thrombosis is the primary cause of death worldwide, with the most important risk factors being smoking, unhealthy diet, and physical inactivity. However, although there are clear indications in the literature of beneficial effects of physical activity in lowering the risk of cardiovascular events, exercise can be considered a double-edged sword in that physical exertion can induce an immediate pro-thrombotic environment. Epidemiological studies show an increased risk of cardiovascular events after acute exercise, a risk, which appear to be particularly apparent in individuals with lifestyle-related disease. Factors that cause the increased susceptibility to arterial thrombosis with exercise are both chemical and mechanical in nature and include circulating catecholamines and vascular shear stress. Exercise intensity plays a marked role on such parameters, and evidence in the literature accordingly points at a greater susceptibility to thrombus formation at high compared to light and moderate intensity exercise. Of importance is, however, that the susceptibility to arterial thrombosis appears to be lower in exercise-conditioned individuals compared to sedentary individuals. There is currently limited data on the role of acute and chronic exercise on the susceptibility to arterial thrombosis, and many studies include incomplete assessments of thrombogenic clotting profile. Thus, further studies on the role of exercise, involving valid biomarkers, are clearly warranted.

Thrombocyte aggregation, endothelial dysfunction and acute myocardial infarction

<zakljucak> Akutni infarkt miokarda u razvijenim i srednje razvijenim zemljama jedan je od najcescih uzroka mortaliteta i morbiditeta, pa poznavanje patofiziologije ateroskleroze i aterotromboze predstavlja najveci izazov savremenoj medicini. Najcesci uzrok AIM je ateroskleroza epikardnih koronarnih arterija sa posledicnom rupturom i/ili erozijom aterosklerotskog plaka, nastajanjem intrakoronarne tromboze i prekida cirkulacije arterijske krvi u predelu irigacije infarktne arterije. Sklonost ka aterosklerozi ne znaci po pravilu i sklonost ka trombozi, i obrnuto. Mnogobrojni faktori rizika od ishemijske bolesti srca modifikuju funkciju hemostaznog sistema, remete ravnotezu izmedju proagregatornih i antiagregatornih, prokoagulantnih i antikoagulantnih, profibrinolitickih i antifibrinolitickih mehanizama. Na taj nacin genetski uslovljena sklonost ka trombozi potencira se faktorima rizika, sto zajedno vodi ka aterotrombozi i akutnom koronarnom sindromu. Fizicko opterecenje je jedan od faktora rizika od ishemijske bolesti srca. Efekat zavisi od vrste opterecenja, duzine trajanja i stepena utreniranosti bolesnika. Umerena fizicka aktivnost kroz duzi vremenski period ima protektivni znacaj kod bolesnika sa ishemijskom bolescu srca, jer poboljsava funkciju endotela, smanjuje oksidativni stres na nivou endotela, smanjuje broj i aktivnost trombocita kao i aktivnost mnogih faktora koagulacije i na taj nacin smanjuje ucestalost ponovnih koronarnih dogadjaja. Nasuprot tome, akutna fizicka aktivnost dovodi do izrazenog prokoagulantnog stanja sto na terenu disfunkcije endotela i specificnosti hemostaznog sistema moze provocirati ponovnu koronarnu trombozu.

The effects of exercise stress testing on soluble E-selectin, von Willebrand factor, and circulating endothelial cells as indices of endothelial damage/dysfunction

BACKGROUND

The quantification of circulating endothelial cells (CECs) in whole blood is an increasingly recognized index of endothelial damage/dysfunction. Abnormal CECs have been linked to the severity of coronary artery disease (CAD).

OBJECTIVE

We assessed the relationship of CECs to other markers of endothelial dysfunction (von Willebrand factor (vWF) and soluble E-selectin (sEsel)) during exercise stress testing (EST) in a cohort of patients with suspected CAD.

METHODS

We studied a cohort of patients referred to our chest pain clinic with a history of exertional chest pain. Treadmill EST was performed, using a full Bruce exercise protocol. Blood for CECs (immunobead method), vWF and sEsel (both ELISA) were collected immediately before (pre-exercise), immediately following exercise, and at 30 minutes post-EST.

RESULTS

We studied 31 patients (84% male; mean (SD) age 58.4 (9.8) years). Of the entire cohort, 14 patients (45.2%) had a positive EST. Exercise led to significant increases in levels of CECs, sEsel, vWF, white blood cells (WBC), heart rate, mean and systolic blood pressure compared with base-line (all P < 0.05). There was a significant correlation between the change (delta (immediate post-pre-exercise)) in CECs and delta vWF (r = 0.45; 95% CI 0.11-0.69: P = 0.01) and delta sEsel (r = 0.41; 0.05-0.7: P = 0.02), as well as between delta vWF and delta sEsel (r = 0.55; 0.25-0.76: P = 0.001). Neither absolute nor delta CEC counts were predictive of exercise work-load/functional capacity, nor the presence of positive EST results.

CONCLUSION

EST led to a significant increase in endothelial markers (CECs, vWF, and sEsel) compared with base-line levels. The rise in CECs correlated with the increases in other endothelial markers, but was not related to the either exercise workload/capacity or to the presence of a positive EST.

Platelet activation increases with the severity of peripheral arterial disease: Implications for clinical management

INTRODUCTION

Patients with peripheral arterial disease (PAD) have increased mortality from cardiovascular events compared with age and sex matched controls Platelets play a major role in atherosclerosis and thrombotic vascular events. Platelet reactivity is increased in patients with PAD compared with healthy controls. We aimed to determine the relationship, if any, between platelet activation and severity of disease.

METHODS AND RESULTS

One hundred eighty-two patients with intermittent claudication (IC) or subcritical limb ischemia (SLI), defined as the presence of rest pain or ulceration, had the following investigations performed: platelet P-selectin expression and bound fibrinogen by flow cytometric analysis and platelet aggregation using the rapid platelet function assay with arachidonic acid (AA) and thrombin receptor activation peptide (TRAP) as agonists. Patients with SLI compared with IC had significantly enhanced ADP stimulated P-selectin expression (median 42.45% [inter-quartile range 33.32% to 58.5%] vs 35.2% [26.07% to 46.32%], P = .002) and bound fibrinogen (73.7% [54.3% to 83.2%] vs 63.7% [43.8% to 76.5%], P = .001). TRAP stimulated aggregation was higher (207 [153 to 238] PAU vs 183[155 to 199] PAU, P = .04) but AA mediated aggregation was not significantly different. An ankle-brachial pressure index (ABPI) of less than 0.6 was associated with increased ADP stimulated P-selectin and bound fibrinogen (P < .05). ABPI correlated inversely with ADP stimulated P-selectin expression (r = -0.228, P = .003), ADP stimulated fibrinogen binding (r = -0.156, P = .043) and TRAP stimulated aggregation (r = -0.179, P = .04).

CONCLUSION

We have demonstrated for the first time that progression of severity of PAD is not only reflected by symptoms, signs, and ABPI but also by increased platelet activity as assessed by both flow cytometry and aggregation. As patients with more severe PAD have increased cardiovascular mortality, our findings suggest that new strategies for platelet inhibitory therapy are indicated in these patients.