Fibrinolytic responses to acute physical activity in older hypertensive men

Acute exercise-induced inflammatory and thrombotic response in hypertensive patients

PURPOSE

Vigorous physical activity may acutely trigger the onset of an acute coronary syndrome especially in sedentary persons with established cardiovascular risk factors such as arterial hypertension. The rupture of an inflamed coronary plaque and the activation of the coagulation cascade are the main underlying mechanisms. The present study aimed to determine the effect of acute exercise on the inflammatory and thrombotic response in patients with arterial hypertension as compared to normotensive peers.

METHODS

After excluding patients with any inflammatory or/and coronary artery disease, a total of 60 non-treated hypertensive patients and 65 normotensive individuals underwent a maximal treadmill exercise testing. Βlood samples were drawn at rest and immediately after peak exercise. High-sensitivity C-reactive protein (hsCRP), serum amyloid A (SAA), white blood cell (WBC), interleukin-6 (IL-6), and total fibrinogen (TF) levels, as well as plasminogen activator inhibitor-1 (PAI-1) activity, were measured.

RESULTS

All biomarkers increased with exercise, except PAI-1, which decreased (P < 0.05 for the change between resting and peak exercise for all biomarkers). Αfter adjusting for relevant confounders (duration of exercise, metabolic equivalents, systolic BP, and rate-pressure product achieved at peak exercise), the normotensive group had less marked (P < 0.05) exercise-induced changes than the hypertensive group in hsCRP (7.7 vs. 8.6%), SAA (5.6 vs. 11.9%), WBC (45.0 vs. 51.7%), and PAI-1 (-17.3 vs. -20.1%) and a similar (P = NS) change in IL-6 (23.8 vs. 23.0%) and TF (8.5 vs. 8.5%).

CONCLUSION

In conclusion, the acute exercise-induced inflammatory and thrombotic response seems to be more pronounced in non-treated hypertensive patients than in normotensive controls. Possible clinical implications of this finding merit further examination.

Coronavirus (COVID-19), Coagulation, and Exercise: Interactions That May Influence Health Outcomes

The proinflammatory cytokine storm associated with coronavirus disease 2019 (COVID-19) negatively affects the hematological system, leading to coagulation activation and endothelial dysfunction and thereby increasing the risk of venous and arterial thrombosis. Coagulopathy has been reported as associated with mortality in people with COVID-19 and is partially reflected by enhanced D-dimer levels. Poor vascular health, which is associated with the cardiometabolic health conditions frequently reported in people with severer forms of COVID-19, might exacerbate the risk of coagulopathy and mortality. Sedentary lifestyles might also contribute to the development of coagulopathy, and physical activity participation has been inherently lowered due to at-home regulations established to slow the spread of this highly infectious disease. It is possible that COVID-19, coagulation, and reduced physical activity may contribute to generate a “perfect storm,” where each fuels the other and potentially increases mortality risk. Several pharmaceutical agents are being explored to treat COVID-19, but potential negative consequences are associated with their use. Exercise is known to mitigate many of the identified side effects from the pharmaceutical agents being trialled but has not yet been considered as part of management for COVID-19. From the limited available evidence in people with cardiometabolic health conditions, low- to moderate-intensity exercise might have the potential to positively influence biochemical markers of coagulopathy, whereas high-intensity exercise is likely to increase thrombotic risk. Therefore, low- to moderate-intensity exercise could be an adjuvant therapy for people with mild-to-moderate COVID-19 and reduce the risk of developing severe symptoms of illness that are associated with enhanced mortality.

The exercise paradox may be solved by measuring the overall thrombotic state using native blood

While exercise is widely believed to prevent atherothrombotic diseases, it occasionally causes sudden death. This exercise paradox may be due to the inadequate testing of the thrombotic and thrombolytic status. A recently developed shear-induced thrombosis/endogenous fibrinolysis test performed with non-anticoagulated blood samples allows the assessment of the thrombotic state of an individual both at rest and after exercise. This sensitive and physiologically relevant test may help to solve the aforementioned exercise paradox.

Predisposing factors to post-operative adhesion development

BACKGROUND

Adhesion development is the most common sequelae of intra-abdominal and pelvic surgery and represents a significant, yet poorly understood, cause of morbidity among post-operative patients. It remains unclear, for example, exactly why adhesions form more frequently in certain tissues and/or patients, or at specific locations within them, as opposed to others. This review contributes to the growing knowledge pool by elucidating factors that potentially predispose to the development of adhesions. Given the strong correlation between a hypofibrinolytic state and adhesion formation, this review article will examine not only those factors that have been shown to directly predispose to adhesion development, but also those that are likely do so indirectly by means of altering the coagulation/fibrinolytic profile.

METHODS

A literature search was performed using the PubMed database for all relevant English language articles up to February 2014. All of the identified articles were reviewed with particular attention to predisposing factors to post-operative adhesion development. In addition, the reference lists of each article were reviewed to identify additional relevant articles.

RESULTS

Various factors have been shown to directly increase the risk of post-operative adhesion development; namely, certain genetic polymorphisms in the interleukin-1 receptor antagonist, increased estrogen exposure, and endometriosis. In addition, numerous factors are known to increase the risk of fibrosis, therefore likely increasing the risk of adhesion development indirectly. These factors include genetic polymorphisms in plasminogen activator inhibitor-1 and thrombin-activatable fibrinolysis inhibitor, diabetes mellitus, metabolic syndrome, hyperglycemia, obesity, depression, binge alcohol consumption, anti-Parkinsonian medications, oral hormone therapy, pregnancy, and cancer.

CONCLUSIONS

The literature reviewed in this paper will help to direct future research aimed at understanding the mechanisms that underlie the association of certain factors with adhesion development. This information will be crucial in the creation of adequate preventative and treatment strategies.

Effects of acute and chronic exercise in patients with essential hypertension: benefits and risks

The importance of regular physical activity in essential hypertension has been extensively investigated over the last decades and has emerged as a major modifiable factor contributing to optimal blood pressure control. Aerobic exercise exerts its beneficial effects on the cardiovascular system by promoting traditional cardiovascular risk factor regulation, as well as by favorably regulating sympathetic nervous system (SNS) activity, molecular effects, cardiac, and vascular function. Benefits of resistance exercise need further validation. On the other hand, acute exercise is now an established trigger of acute cardiac events. A number of possible pathophysiological links have been proposed, including SNS, vascular function, coagulation, fibrinolysis, and platelet function. In order to fully interpret this knowledge into clinical practice, we need to better understand the role of exercise intensity and duration in this pathophysiological cascade and in special populations. Further studies in hypertensive patients are also warranted in order to clarify the possibly favorable effect of antihypertensive treatment on exercise-induced effects.

Moderate Exercise and Fibrinolytic Potential in Obese Sedentary Men with Metabolic Syndrome

OBJECTIVE

To investigate the impact of 30-minute walking exercise at 70% VO2max on tissue plasminogen activator (t-PA) Ag and plasminogen activator inhibitor type 1 (PAI-1) Ag in obese sedentary males.

RESEARCH METHODS AND PROCEDURES

A controlled observational study of the effect of a 30-minute acute exercise bout at 70% VO2max on plasma t-PA antigen and PAI-1 antigen in 10 obese sedentary males matched for age, ethnic origin, and smoking status with 10 nonobese sedentary male controls.

RESULTS

The obese group remained hypofibrinolytic compared with the nonobese group at all time-points before, during, and after exercise. t-PA increased in both groups with exercise before returning to baseline values 30 minutes after exercise. PAI-1 did not significantly change in either group with exercise but rose significantly 30 minutes after exercise in the obese group.

DISCUSSION

The reduction in fibrinolytic potential in the obese group represents an increase in acute thrombotic risk and could account for the increased incidence of exercise-associated myocardial infarction observed in sedentary obese groups.

Effects of altered plasminogen activator inhibitor-1 expression on cardiovascular disease

Plasminogen Activator Inhibitor-1 (PAI-1) is a multifunctional protein with the ability to not only regulate fibrinolysis through inhibition of plasminogen activation, but also cell signaling events which have direct downstream effects on cell function. Elevated plasma levels of this protein have been shown to have profound effects on the development and progression of cardiovascular diseases. However, results from a number of studies, especially those using PAI-1 deficient mouse models, have demonstrated that its function is ambiguous, with evidence of both preventing and enhancing various disease states. A number of lifestyle changes and pharmacological reagents have been identified that can regulate PAI-1 levels or function. Those reagents that target function are focused on its ability to regulate plasmin formation, and have been studied in in vivo models of thrombosis. Further investigations involving regulation of cell function could potentially resolve paradoxical issues associated with the function of this protein in regulating cardiovascular disease.

Plasminogen activator inhibitor-1 (PAI-1): a key factor linking fibrinolysis and age-related subclinical and clinical conditions

INTRODUCTION

The close relationship existing between aging and thrombosis has growingly been studied in this last decade. The age-related development of a prothrombotic imbalance in the fibrinolysis homeostasis has been hypothesized as the basis of this increased cardiovascular and cerebrovascular risk. Fibrinolysis is the result of the interactions among multiple plasminogen activators and inhibitors constituting the enzymatic cascade, and ultimately leading to the degradation of fibrin. The plasminogen activator system plays a key role in a wide range of physiological and pathological processes.

METHODS

Narrative review.

RESULTS

Plasminogen activator inhibitor-1 (PAI-1) is a member of the superfamily of serine-protease inhibitors (or serpins), and the principal inhibitor of both the tissue-type and the urokinase-type plasminogen activator, the two plasminogen activators able to activate plasminogen. Current evidence describing the central role played by PAI-1 in a number of age-related subclinical (i.e., inflammation, atherosclerosis, insulin resistance) and clinical (i.e., obesity, comorbidities, Werner syndrome) conditions is presented.

CONCLUSIONS

Despite some controversial and unclear issues, PAI-1 represents an extremely promising marker that may become a biological parameter to be progressively considered in the prognostic evaluation, in the disease monitoring, and as treatment target of age-related conditions in the future.

Transcutaneous electrical nerve stimulation induces vasodilation in healthy controls but not in refractory angina patients

CONTEXT

Transcutaneous electrical nerve stimulation (TENS) is an effective treatment option to relieve ischemic pain in refractory angina pectoris (RAP). In healthy persons, TENS enhances local blood flow, but the mechanism responsible for the anti-ischemic effect in RAP seems to be different.

OBJECTIVE

The aim of the present investigation was to compare the difference in blood flow and vasodilatory response to TENS between angina patients and healthy controls and evaluate how vascular response in these groups is affected by amperage dosage above and below motor threshold levels.

METHODS

Our study evaluated upper limb vascular responses to low- and high-dose TENS (below and above motor threshold) in RAP patients compared with healthy controls. TENS was applied on the nondominating forearm. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. Forearm vascular resistance (FVR) was determined (mean arterial pressure [MAP]/FBF). Measurements were done during baseline, low-dose TENS, high-dose TENS, and during recovery.

RESULTS

A significant dose-dependent increase in FBF in response to TENS stimulation was seen in controls (n=18) but not in RAP (n=23) (P=0.008). There was no significant difference in FVR ratio (FVR(stim)/FVR(ctrl)) between control (n=7) and RAP (n=23) groups at low dose (controls, 5.7+/-21%; RAP, 9.7+/-20%) or recovery (controls, -4.6+19%; RAP, 5.9+25%). High-dose TENS resulted in a significantly reduced FVR ratio (-16.8+/-11%) in controls (n=7) compared with RAP (1.6+/-32%, n=23) (P=0.02).

CONCLUSION

High-dose TENS induces forearm vasodilation in healthy subjects but not in patients with RAP. These findings suggest that TENS has different vascular effects in patients with severe coronary artery disease compared with healthy controls.

Coagulation and fibrinolysis are in balance after moderate exercise in middle-aged participants

Increased age is associated with a higher risk of thrombotic events. The aim of this study was to investigate the age-related changes in hemostasis before and after moderate exercise controlled by individual anaerobic threshold as recommended for rehabilitation training. In this study, 24 young (25 +/- 1 years) and 24 middle-aged healthy nonsmokers (48 +/- 1 years) underwent an individualized exercise test with 80% of individual anaerobic threshold (young individuals: 127 +/- 6 W; middle-aged individuals: 128 +/- 5 W; values are expressed as mean +/- standard error of mean) for 60 minutes. The blood samples were collected before and after the exercise. The age-related higher (P < or = .05) levels could be detected in factors II, VII, VIII, IX, XI, XII, prothrombin fragment 1+2, in tissue plasminogen activator antigen and activity, as well as in plasminogen. The relative exercise-induced increases in these parameters were similar in both groups, although beginning at a higher level for those in the middle-aged group.A statistically enhanced increase after exercise in the middle-aged group could be shown in prothrombin fragment 1+2 (young individuals: 98 +/- 6 to 102 +/- 6 pmol/L; middle-aged individuals: 138 +/- 7 to 156 +/- 8 pmol/L) and in thrombin-antithrombin complex (young individuals: 2.2 +/- 0.1 to 3.1 +/- 0.2 microg/L; middle-aged individuals: 2.4 +/- 0.3 to 3.9 +/- 0.6 microg/L); the latter only showing a tendency. The data show the age-related changes with a rise in blood coagulation and fibrinolysis in a healthy middle-aged group compared with younger participants. Moderate exercise leads to comparably relative increases in hemostatic parameters but starting at higher levels. However, the exercise-induced thrombin generation (prothrombin fragment 1+2) is enhanced in the middle-aged participants in comparison with younger participants, but may be compensated by a sufficient fibrinolysis, and therefore the hemostatic system remains in balance.

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.

A systematic review of the effects of acute psychological stress and physical activity on haemorheology, coagulation, fibrinolysis and platelet reactivity: Implications for the pathogenesis of acute coronary syndromes

Physical activity and psychological stress are two potential triggers for the onset of acute coronary syndromes (ACS). To examine the mechanisms underlying this association, we systematically reviewed the literature to determine the effects of acute psychological stress and physical activity on haemorheology and haemostasis. Studies examining the haemorheological and haemostatic response to an acute bout of physical activity (i.e. <60 min) or laboratory psychological stress task were eligible for inclusion. The experimental evidence, although compromised by various methodological weaknesses, suggests that low and moderate intensity physical activity may be cardio-protective through beneficial effects on fibrinolytic system. High levels of physical activity, and psychological to a lesser extent, have been consistently associated with robust changes in haemorheology and haemostasis. Such findings imply that such activities may have the potential to trigger the onset of ACS, although in reality this may be limited sedentary individual and/or those with pre-existing vascular disease. In addition, the data also suggest that individuals may be at a greatest risk of stress-induced thrombogenesis in the period immediately following physical activity or psychological stress, rather than during the activity per se. In conclusion, psychological stress and physical activity may act as potential triggers for the onset of ACS via effects on haemostasis and haemorheology.

Hemodynamic, hemostatic, and endothelial reactions to psychological and physical stress in coronary artery disease patients

Episodes of psychological and physical stress may elicit thrombotic cardiac events, such as myocardial infarction. These events are triggered when there are concurrent hemodynamic, hemostatic, and endothelial abnormalities. Hemodynamic, hemostatic, and endothelial reactions of 72 (15 women, 57 men) coronary artery disease patients to psychological and physical stress were examined. Blood pressure, electrocardiography, and impedance cardiography were recorded during rest, mental arithmetic, and exercise. Blood was collected, via catheter, at rest and after each task. Mental arithmetic elicited increases in blood pressure, heart rate, cardiac output, and cardiac contractility, but no consistent changes in hemostatic and endothelial markers. In contrast, exercise, in addition to increasing blood pressure, heart rate, cardiac output, cardiac contractility, and lowering peripheral resistance, elicited increases in plasma viscosity, hematocrit, platelets, and tissue plasminogen activator together with a decrease in plasminogen activator inhibitor. This pattern of hemodynamic, hemostatic, and endothelial reactions suggests that acute psychological and physical stress influence the thrombotic system differently in these high risk patients. Future research is needed to investigate how these stress responses are prospectively related to acute cardiac events.

Enhanced tissue plasminogen activator synthesis by the sympathetic neurons that innervate aging vessels

We investigated the source of the increased release of tissue plasminogen activator (t-PA) into the circulation that occurs during natural aging. Both the basal release and the acute stress-associated release induced by sympathetic stimulations are greater in older subjects. It is widely assumed that the source of these increases is vascular endothelium. However, the sympathetic neurons that densely innervate resistance vessel walls were recently shown to synthesize and transport active t-PA to axon terminals in vascular smooth muscle, suggesting an alternative source. These fine t-PA-bearing axons lie in the seldom-studied deep adventitia of vessel walls, where they are less visible than endothelium in tissue sections. Using Northern blot analysis, we observed that t-PAmRNA synthesis is increased 54% in the ganglion parent neuron cell bodies that innervate aged vessels. The t-PA release from isolated, aged ganglia in cultures was twofold greater than that from younger controls. In addition, aged whole-artery explants showed a 20% greater basal and a 50% greater acute release of stored t-PA in vitro. In vivo levels of active t-PA were 33% greater in the blood and 40% greater in the aqueous humor. These results are consistent with an increased infusion of the active t-PA protease from sympathetic axon terminals into the vessel wall extracellular matrix and the blood during natural aging, in addition to the basal endothelial release. We suggest that the cumulative impact of an accelerated plasmin production and matrix degradation within vessel walls, especially during repetitive stress, may play an unrecognized role in the pathogenesis of vascular aging. The possibility that increased sympathetic nervous system plasminogenesis influences the aging process in nonvascular tissues also deserves further investigation.

A single bout of walking exercise enhances endogenous fibrinolysis in stroke patients

PURPOSE

Impaired endogenous fibrinolysis is an important predictor for increased risk of stroke and myocardial infarction. Acute exercise can enhance fibrinolysis, primarily by stimulating short-term increases in plasma tissue plasminogen activator (tPA), which is postulated to protect against atherothrombotic events. No prior studies have examined the fibrinolytic response to exercise in stroke survivors despite their high risk for recurrent stroke and myocardial infarction. The purpose of this study was to assess the fibrinolytic response to acute submaximal exercise in chronic hemiparetic stroke patients.

METHODS

Eighteen (16 men, 2 women) untrained stroke patients with chronic hemiparetic gait deficits volunteered for participation in this single session exercise study. Fasting blood samples for determination of tPA and plasminogen activator inhibitor (PAI-1) enzyme activities were obtained before, immediately after, and 60 min after submaximal treadmill walking. Patients walked at 60% maximal heart rate reserve (low-moderate intensity) for a cumulative total of 20 min.

RESULTS

The exercise bout increased tPA activity by 79% (P < 0.01) and decreased PAI-1 activity by 18% (P < 0.01). At 1 h after completing the walking exercise, plasma tPA activity levels were still significantly elevated (43%,P < 0.01), and PAI-1 activity levels were 25% lower (P < 0.01) than baseline.

CONCLUSIONS

These findings demonstrate that a single bout of aerobic walking exercise can improve fibrinolysis profiles in chronic stroke patients. Significant increases in endogenous tPA and reductions in PAI-1 activity persist for at least 1 h after exercise cessation. The implications are that alterations in physical activity during the day may modify clot lysing potential, thereby affecting atherothrombotic risk.

Ozonized autohaemotransfusion and fibrinolytic balance in peripheral arterial occlusive disease

The acute effects of a major ozonized autohaemotransfusion on blood fibrinolytic capacity were evaluated in 20 subjects affected by peripheral arterial occlusive disease (PAOD). The parameters examined were tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type-1 (PAI-1). In subjects not previously submitted to autohaemotransfusion ('unaccustomed' subjects), whether they were PAOD patients or healthy volunteers, the PAI-1/t-PA ratio in the blood samples taken 15 min before the autohaemotransfusion was higher (P < or = 0.05) than at baseline. These changes were independent of the presence of ozone in the autohaemotransfusion blood. Values in both healthy and PAOD-affected individuals were again at baseline 120 min after the end of autohaemotransfusion. In PAOD patients and in healthy subjects previously submitted to several autohaemotransfusions ('accustomed' subjects), the PAI-1/t-PA ratio did not significantly change before, during and after an additional autohaemotransfusion. The results (the increased heart rate and epinephrine and norepinephrine urinary excretion only in non-accustomed subjects) suggest that the acute fibrinolytic imbalance is caused by the apprehensive state produced by the procedure in unaccustomed subjects. Autohaemotransfusion with ozonized blood per se does not significantly influence the fibrinolytic balance.

Retained fibrinolytic response and no coagulation activation after acute physical exercise in middle-aged women with previous myocardial infarction

Sudden physical exertion is associated with an increased risk of acute myocardial infarction (MI) and sudden cardiac death. In addition, activation of the coagulation cascade and/or reduced fibrinolytic capacity after physical exercise has been reported in patients with cardiovascular disease. We investigated the haemostatic responses to an acute submaximal physical exercise in middle-aged women with a history of MI compared with healthy, age-matched controls. Resting plasma von Willebrand factor antigen (vWF Ag) and tissue plasminogen activator (tPA) antigen concentrations and plasminogen activator inhibitor-1 (PAI-1) activity were higher in the patients compared with control subjects. After 30 min of submaximal exercise on a bicycle ergometer, small, but still significant, increases in fibrinogen and vWF Ag concentrations were found in both groups. However, exercise did not induce thrombin generation and fibrin formation, as assessed by thrombin-antithrombin complex and fibrin D-dimer, in either group. Both tPA antigen concentration and activity increased and PAI-1 activity decreased significantly with exercise in both groups. Interestingly, the magnitude of changes in these latter variables did not differ between the groups (P=.99, P=.88 and P=.24, respectively). The present study demonstrates that some middle-aged women with previous MI have no signs of coagulation activation and retained fibrinolytic response after submaximal exercise. The clinical implication of these results might be that women with stable coronary heart disease can participate in rehabilitative exercise training without exhibiting a procoagulative state.

Dose-response and coagulation and hemostatic factors

PURPOSE

The purpose of this study was to evaluate the dose-response relations of regular physical activity on platelet function, blood coagulation factors, and fibrinolytic factors, on the basis of studies with appropriate experimental design.

METHODS

MEDLINE-based literature search supplemented with relevant review articles and other individual articles was used. The review concentrates on controlled randomized clinical trials on the impact of regular physical exercise on platelet function, and on blood coagulation and fibrinolytic factors.

RESULTS

Physical exercise acutely activates platelets and the fibrinolytic system, and some factors of the blood coagulation cascade. These findings, the earliest of which were published already in the 1960s, are mainly derived from uncontrolled observations. These studies have led to the conclusion that unbalanced activation of the hemostatic system during acute exercise may be part of the mechanisms for sudden cardiac events during or shortly after heavy physical exercise. The effects of regular physical exercise on various aspects of platelet function, blood coagulation, and fibrinolysis have been the object in only a few controlled randomized trials. With the exception of data on platelet function, the results remain contradictory.

CONCLUSION

Controlled randomized clinical trials with adequate statistical power and experimental study designs with subjects of different ages and health status are warranted for the evaluation of the dose-response issues to clearly delineate the preventive and therapeutic potential of regular physical exercise.

Effect of acute exercise on the raised plasma fibrinogen, soluble P-selectin and von Willebrand factor levels in chronic atrial fibrillation

BACKGROUND

There is increasing evidence that chronic atrial fibrillation (AF) is associated with a prothrombotic or hypercoagulable state.

HYPOTHESIS

This study was undertaken to determine whether short-term exercise in patients with chronic AF would shift the overall hemostatic balance toward a more prothrombotic state with a reduction in fibrinolytic potential.

METHODS

We recruited 20 patients (13 men; mean age 65 years +/- 11 standard deviation [SD]) with chronic AF who were not treated with antithrombotic therapy and exercised them to exhaustion using a multistage treadmill exercise (standard Bruce) protocol. Blood samples were taken pre exercise, immediately after cessation of exercise, and at 20 min post exercise. The prothrombotic state was quantified by fibrinogen (an index of hemorheology and a coagulation factor), soluble P-selectin (sP-sel, marking platelet activation), von Willebrand factor (vWF, an index of endothelial dysfunction), and plasminogen activator inhibitor-1 (PAI-1, a regulator of fibrinolytic activity) levels. There were two groups of age- and gender-matched controls in sinus rhythm: (1) healthy controls, and (2) "hospital controls" who were patients with vascular disease.

RESULTS

Baseline levels of vWf (p = 0.034) and fibrinogen (p < 0.0001), but not sP-sel (p = 0.075) were significantly elevated in patients with AF compared with both control groups in sinus rhythm. The PAI-1 levels were highest in the hospital control patients, but not in chronic AF (p = 0.041). Following treadmill exercise, achieving a mean metabolic equivalent of 4.9 METS (+/- 1.75 SD) and total exercise duration of 4.9 min (+/- 2 SD), there was a significant rise in plasma fibrinogen (repeated measures analysis of variance [ANOVA] p = 0.047) and a reduction in PAI-1 levels (p = 0.025) in patients with AF. There were no significant changes seen in vWf (p = 0.308) or sP-sel (p = 0.071) levels. No significant changes in these indices were seen in hospital controls (all p = not significant), despite a much longer duration of exercise with greater workload.

CONCLUSION

Patients with chronic AF have increased vWf and fibrinogen levels compared with sinus rhythm. Exercise to exhaustion influences the hypercoagulable state in chronic AF, with a rise in plasma fibrinogen and possible increase in fibrinolytic activity. Nevertheless, acute exercise does not appear to have a significant influence on endothelial dysfunction or platelet activation in patients with AF.

Seasonal variation in household, occupational, and leisure time physical activity: longitudinal analyses from the seasonal variation of blood cholesterol study

The authors examined seasonal variation in physical activity in longitudinal analyses of 580 healthy adults from Worcester, Massachusetts (the Seasonal Variation of Blood Cholesterol Study, 1994-1998). Three 24-hour physical activity recalls administered five times during 12 months of follow-up were used to estimate household, occupational, leisure time, and total physical activity levels in metabolic equivalent (MET)-hours/day. Trigonometric models were used to estimate the peak-to-trough amplitude and phase of the peaks in activity during the year. Total activity increased by 1.4 MET-hours/day (121 kcal/day) in men and 1.0 MET-hours/day (70 kcal/day) in women during the summer in comparison with winter. Moderate intensity nonoccupational activity increased by 2.0-2.4 MET-hours/day in the summer. During the summer, objectively measured mean physical activity increased by 51 minutes/day (95% confidence interval: 20, 82) in men and by 16 minutes/day (95% confidence interval: -12, 45) in women. The authors observed complex patterns of seasonal change that varied in amplitude and phase by type and intensity of activity and by subject characteristics (i.e., age, obesity, and exercise). These findings have important implications for clinical research studies examining the health effects of physical activity and for health promotion efforts designed to increase population levels of physical activity.