Effect of cold pressor test and awareness of hypertension on platelet function in normotensive and hypertensive women

Irregularities of Coagulation in Hypertension

PURPOSE OF REVIEW

This review article summarizes the role of coagulation in the pathogenesis of hypertension. It specifically focuses on significant factors and markers associated with coagulation, including D-dimer, fibrinogen and fibrin, prothrombin, P-selectin, soluble urokinase plasminogen activator receptor, thrombomodulin, tissue factor, tissue plasminogen activator, von Willebrand factor, β-thromboglobulin, and Stuart-Prower factor.

RECENT FINDINGS

D-dimer levels were elevated in hypertensive individuals compared to healthy controls, and the levels increased with the severity of hypertension. These findings indicate that increased coagulation activity of fibrin plays a role in the development of thromboembolic complications in hypertensive patients. Additionally, both fibrinogen levels and D-dimer levels displayed a positive correlation with the duration of hypertension, suggesting that these biomarkers were positively associated with the length of time an individual had been hypertensive. Increased systolic and diastolic blood pressures have been linked to higher levels of prothrombin time and activated partial thromboplastin time in individuals with hypertension as well as those with normal blood pressure. Also, the presence of P-selectin, produced by activated platelets and endothelial cells during angiotensin II stimulation, played a role in the development of cardiac inflammation and fibrosis associated with hypertension. Moreover, the change in systolic blood pressure was associated with baseline soluble urokinase plasminogen activator receptor (suPAR) in hypertensive participants, and the change in suPAR levels was associated with the development of hypertension. Moreover, it was observed a decrease in thrombomodulin expression in the placenta of preeclamptic patients, suggesting its potential involvement in placental dysfunction, possibly driven by an imbalance in angiogenic factors. Tissue factors and autophagy might have significant implications in the pathogenesis of chronic thromboembolic pulmonary hypertension, particularly in the context of vascular remodelling. Likewise, ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) might be a promising biomarker for the early detection of pulmonary arterial hypertension and the von Willebrand factor is a candidate prognostic biomarker. The arterial β-thromboglobulin levels were significantly lower than venous levels. This article concludes that D-dimer, fibrinogen and fibrin, prothrombin, P-selectin, soluble urokinase plasminogen activator receptor, thrombomodulin, tissue factor, tissue plasminogen activator, von Willebrand factor, and β-thromboglobulin are important factors involved in the pathogenesis of hypertension.

Arterial and venous blood sampling is equally applicable for coagulation and fibrinolysis analyses

OBJECTIVES

No consensus exists upon whether arterial and venous blood samples are equivalent when it comes to coagulation analyses. We therefore conducted a comparative cohort study to clarify if arteriovenous differences affect analyses of primary and secondary hemostasis as well as fibrinolysis.

METHODS

Simultaneous paired blood samplings were obtained from a cannula in the radial artery and an antecubital venipuncture in 100 patients immediately before or one day after thoracic surgery. Analyses of platelet count and aggregation, International Normalized Ratio (INR), activated partial thromboplastin time (APTT), antithrombin, thrombin time, fibrinogen, D-dimer, rotational thromboelastometry (ROTEM), thrombin generation, prothrombin fragment 1 + 2, and an in-house dynamic fibrin clot formation and lysis assay were performed.

RESULTS

No differences were found between arterial and venous samples for the far majority of parameters. The only differences were found in INR, median (IQR): venous, 1.1 (0.2) vs. arterial, 1.1 (0.2) (p<0.002) and in prothrombin fragment 1 + 2: venous, 289 (209) pmol/L vs. arterial, 279 (191) pmol/L (p<0.002).

CONCLUSIONS

The sampling site does not affect the majority of coagulation analyses. Small differences were found for two parameters. Due to numerically very discrete differences, they are of no clinical relevance. In conclusion, the present data suggest that both samples obtained from arterial and venous blood may be applied for analyses of coagulation and fibrinolysis.

Reduced parasympathetic tone in newly diagnosed essential hypertension

AIM

The aim of the study was to compare heart rate variability (HRV) of newly diagnosed essential hypertensive subjects with controls.

METHODS

The study was conducted on 120 hypertensive subjects and 120 controls.

RESULTS

The time-domain measures, standard deviation of all RR intervals (SDNN), the square root of the mean of the sum of the squares of differences between adjacent RR intervals (RMSSD), and percentage of consecutive RR intervals that differ by more than 50ms (pNN50) which reflect parasympathetic activity were significantly less in hypertensive subjects. In frequency-domain measures, high frequency [HF (ms(2))] and [HF (nu)], which reflects parasympathetic activity, was significantly less in hypertensive subjects while LF (nu) and LF/HF (%), which reflect sympathetic activity, were comparable between the groups.

CONCLUSION

These findings suggest that HRV is reduced in subjects with newly diagnosed essential hypertension and the parasympathetic dysregulation is present in the early stage of essential hypertension.

Hypertension in women: latest findings and clinical implications

Cardiovascular disease claims more women's lives than any other disease. Hypertension is an important risk factor for cardiovascular disease in women but is often underestimated and undiagnosed and there is an ongoing misperception that women are at a lower risk of cardiovascular disease than men. The attainment of clinical blood pressure goals can markedly reduce cardiovascular morbidity and mortality, yet approximately two-thirds of treated hypertensive women have uncontrolled blood pressure. Furthermore, there are special risk factors that are unique for women that needs acknowledgement in order to help prevent the great number of hypertension-related events in women. Guidelines for treatment of hypertension are similar for men and women. More studies on the interaction between gender and response to antihypertensive drugs would be of interest.

Comparison of venous and arterial blood sampling for the assessment of platelet aggregation with whole blood impedance aggregometry

Platelet monitoring is presently under evaluation in the clinic as a tool to improve antiplatelet treatment in patients with coronary artery disease (CAD). Measuring platelet function has, however, many inherent problems. It is important not only to evaluate the method used, but also to evaluate and standardize sampling and sample handling. As platelet monitoring is often performed in connection to coronary angiography and percutaneous coronary interventions, arterial sampling may be more convenient. However, in the outpatient follow-up setting venous sampling is, for obvious reasons, more practical and convenient. In the present study we compared platelet aggregation in blood collected from the arterial sheath to blood collected from the antecubital vein using multiple electrode aggregometry in whole blood in 28 patients with CAD. We found that sampling from artery and vein give similar data and that an identical number of patients with insufficient antiplatelet responses ('low responders' to aspirin and clopidogrel, respectively, according to predefined criteria) were detected with respect to adenosine diphosphate induced and arachidonic-acid induced aggregation. Thus both arterial and venous blood samples can be used in the monitoring of platelet function when multiple electrode aggregometry is applied to detect 'low responders'.

Sympathetic reactivity in agoraphobic patients with and without personality disorders

OBJECTIVE

To compare sympathetic activity in agoraphobic patients with and without personality disorders before and after 11 weeks inpatient treatment.

METHODS

Agoraphobic patients (n=38), 84% with panic disorder and 47% with personality disorders underwent cold pressure test (CPT), mental stress test (MST), and a specific anxiety test (SAT). Psychological assessments were done by the Bodily Sensations Questionnaire (BSQ), the Agoraphobic Cognitions Questionnaire (ACQ), Spielberger STAI-1 and -2, and a Stress Test Anxiety (STA) questionnaire. Sympathetic activity was measured by blood pressure, heart rate, epinephrine, and norepinephrine.

RESULTS

The sympathetic activity did not differ significantly between patient groups, and the reactivity to stress was very low. The sympathetic reactivity remained unchanged after treatment, whereas psychiatric symptoms decreased. Correlations between sympathetic activity and psychological distress were not significant.

CONCLUSION

Interpretation of bodily signals seems to be more important than the actual sympathetic activity in agoraphobic patients.

Autonomic function in hypertensive and normotensive subjects: the importance of gender

Baroreceptor reflex sensitivity (BRS) has been found lower and heart rate variability (HRV) parasympathetic markers have been found higher in healthy women than in healthy men. Thus, in the present study we hypothesized gender differences in the autonomic function among hypertensive subjects. Forty-one hypertensive patients and 34 normotensive subjects, age 53+/-1 years, were examined. Four weeks after cessation of antihypertensive therapy, HRV was assessed in 24-hour Holter ECGs, and BRS was calculated with the transfer technique. A t test was performed after log transformation of spectral values. Resting blood pressure and heart rate in the hypertensive and the normotensive groups were 150+/-2/100+/-1 (mean+/-SEM) and 121+/-2/81+/-1 mm Hg, respectively, and 68+/-1 and 60+/-1 bpm, respectively (P<0.0005). Compared with normotensive controls, hypertensive patients had lower total power (1224+/-116 versus 1797+/-241 ms(2); P=0.03), lower low frequency power (550+/-57 versus 813+/-115 ms(2); P=0.04), lower high frequency power (141+/-23 versus 215+/-38 ms(2); P=0.06), lower root mean square successive difference (28.7+/-2.7 versus 35.7+/-3.0 ms; P=0.03), and PNN50 (4.9+/-0.6% versus 9.8+/-1.5%; P=0.003). BRS was also lower in the hypertensive subjects (7.6+/-0.6 versus 10.4+/-0.8 ms/mm Hg; P=0.005). When comparing the same parameters between normotensive subjects and hypertensive subjects within the same gender group, we found significant reduction (P<0.05) only within the female group. The difference in BRS within the female group was twice that within the male group. Stepwise multiple regression analysis revealed gender, age, HDL cholesterol, and blood pressure as independent explanatory variables of BRS and HRV. Our results suggest that gender is an important determinant of BRS and HRV. Autonomic function parameters were especially impaired in hypertensive women compared with hypertensive men.

Influence of gender and age on preventing cardiovascular disease by antihypertensive treatment and acetylsalicylic acid. The HOT study. Hypertension Optimal Treatment

OBJECTIVE

We have assessed the influence of gender and age on the main outcome results of the Hypertension Optimal Treatment (HOT) study.

DESIGN AND INTERVENTIONS

The aims of the HOT study were to study the relationship between three levels of target office diastolic blood pressure (BP) (< or = 90, < or = 85 or < or = 80 mmHg) and cardiovascular (CV) events in hypertensive patients, and to examine the effects of 75 mg acetylsalicylic acid (ASA) daily versus placebo.

SETTING

Outpatient clinical trial in 26 countries.

PATIENTS

A total of 18790 patients (mean age 61.5 years, range 50-80) were randomized and followed for an average of 3.8 years until 71051 patient-years and 683 events had occurred.

MAIN OUTCOME MEASURES

CV death, myocardial infarction (MI) and stroke.

RESULTS

There were significantly fewer MIs in those in the lower diastolic BP target groups (3.0 versus 1.2 and 1.7 MIs/1000 patient-years, P for trend = 0.034) in women (n = 8883), whereas the similar but smaller trend (4.1 versus 4.1 and 3.4 MIs/1000 patient-years) was not statistically significant in men nor in the subgroup analysis of younger and older subjects. The effect of ASA on preventing MI was not influenced by age < 65 years (P= 0.02) or age > or = 65 years (P = 0.04) but was influenced by gender (P = 0.38 in women and P = 0.001 in men, lowered by 42% corresponding to a reduction from 5.0 to 2.9 MIs/1000 patient-years).

CONCLUSIONS

The data of this HOT study sub-analysis suggest somewhat differentiated optimal gender- and age-dependent effects of anti-hypertensive and anti-platelet therapies; lowering of diastolic BP to about 80 mmHg in hypertensive women and, in addition, the administration of 75 mg of ASA to well-treated hypertensive men appear to effectively reduce the most common cardiovascular complication, i.e. myocardial infarction, in patients with essential hypertension.

Systemic adenosine increase during cold pressor test is dependent on sympathetic activation

1. Following local vasoconstriction-inducing stimuli, such as the cold pressor test (CPT), significant changes occur in haemodynamics, with a rise in arterial blood pressure and heart rate (HR) due to the activation of the sympathetic nervous system. Among the compensatory mechanisms to local ischaemia, the endogenous nucleoside adenosine (ADO) has been suggested to play a relevant role by contributing to sympathetic stimulation. The possibility was investigated that CPT-induced increases in plasma ADO levels were not only an expression of the increased production of ADO in the ischaemic area, but also a consequence of systemic sympathoexcitatory mechanisms, thus showing a bidirectional involvement of the mechanisms of ADO formation. 2. The CPT was performed in 15 volunteers and mean arterial blood pressure (MABP) and HR were evaluated, together with plasma levels of noradrenaline (NA) and ADO in the tested and contralateral arm. The 15 subjects were then divided into three groups of five that were treated with either 5 mg transdermal clonidine weekly, 100 mg atenolol daily or 600 mg aminophylline twice daily. After 1 week treatment, the same test was repeated in the respective groups. 3. The CPT induced a rise in MABP and HR and an increase in plasma levels of NA and ADO. Increases in ADO were more pronounced in the tested arm. Clonidine blunted the haemodynamic response and NA release, while increases in ADO increase were reduced to a greater extent in the contralateral arm rather than the tested arm. Atenolol only affected MABP and HR without any effect on NA and ADO levels. Theophylline did not show any effect on CPT-induced changes. 4. In conclusion, local vasoconstriction and ischaemia induced in one arm following CPT are associated with haemodynamic changes dependent on the activation of the sympathetic system. The observed increase in plasma levels of ADO seems to be, in part, a direct expression of local responses to ischaemia (pre-dominant in the tested arm), but also appears as the consequence of systemic sympathoexcitatory mechanisms. Such increases in ADO are not dependent on a beta 1-adrenoceptor-mediated mechanism. Finally, theophylline, at a therapeutic dose, has no effect on the response to CPT.

Beta-thromboglobulin in urine and plasma: influence of coronary risk factors

Blood platelet activation in vivo was evaluated by measuring beta-thromboglobulin in plasma and high molecular weight beta-thromboglobulin in urine in hypertensive smoking and nonsmoking middle-aged men (n=36) and in normotensive age-matched controls (n=40). We found no significant linear relationships between nocturnal or resting urinary high molecular weight beta-thromboglobulin and plasma beta-thromboglobulin in the combined hypertensive and normotensive groups. The excretion of high molecular weight beta-thromboglobulin correlated significantly with diastolic blood pressure when all subjects were pooled. After 60 minutes supine rest, nonsmokers had higher excretion of high molecular weight beta-thromboglobulin than smokers. Plasma beta-thromboglobulin levels tended to be higher in hypertensives. In multivariate analyses, resting high molecular weight beta-thromboglobulin excretion was positively related to diastolic blood pressure and negatively related to smoking, whereas plasma beta-thromboglobulin was positively related to diastolic blood pressure and inversely related to apolipoprotein A1 and B. We conclude that urinary high molecular weight beta-thromboglobulin and plasma beta-thromboglobulin are not closely related, but are complementary analyses, as there are methodological confounders for both variables.