Blood pressure variations, hemorheological determinants, and platelet aggregation in hypertensive patients with unstable angina

The prognostic value of long-term visit-to-visit blood pressure variability on stroke in real-world practice: a dynamic cohort study in a large representative sample of Chinese hypertensive population

BACKGROUND

The prognostic significance of long-term visit-to-visit blood pressure variability (BPV) has not yet been validated in "real world" hypertensive patients. The aim of the current study is to explore the prognostic value of BPV on stroke in hypertensive patients.

METHODS

This was a dynamic prospective cohort study based on electronic medical records in Shanghai, China. Hypertensive patients (N=122,636) without history of stroke at baseline, were followed up from 2005 to 2011. The cohort comprised of 4522 stroke patients and 118,114 non-stroke patients during a mean follow-up duration of 48 months. BPV was measured by standard deviation (SD) and the coefficient of variation (CV) of blood pressure.

RESULTS

The visit-to-visit variability of both systolic blood pressure (SBP) and diastolic blood pressure (DBP) was independently associated with the occurrence of stroke [SD: the hazard ratios (95% confidence intervals) of SBP and DBP were 1.042 (1.021 to 1.064) and 1.052 (1.040 to 1.065); CV: the hazard ratios (95% confidence intervals) of SBP and DBP were 1.183 (1.010 to 1.356) and 1.151 (1.005 to 1.317), respectively]. The hazard ratio values increased along with an increase of the BPV levels of SBP and DBP. The increment effect remained significant after controlling the blood pressure control status of subjects.

CONCLUSIONS

Increased BPV of both SBP and DBP, independent of the average blood pressure, is a predictor of stroke among community hypertensive patients in real-world clinical practice. The risk of stroke increased along with increased BPV. Stabilizing BPV might be a therapeutic target in hypertension.

Androgens and erythropoiesis: past and present

Association between androgens and erythropoiesis has been known for more than seven decades. Androgens stimulate hematopoietic system by various mechanisms. These include stimulation of erythropoietin release, increasing bone marrow activity and iron incorporation into the red cells. Before the discovery of recombinant erythropoietin (rhEpo), androgens were used in the treatment of anemia associated with renal disease, bone marrow suppression, and hypopituitarism. Anabolism is an additional advantage of androgen therapy. Furthermore, in light of recent reports regarding adverse effects of rhEpo, the role of androgen therapy in various types of anemias should be readdressed. Polycythemia remains a known side effect of androgen therapy. In this review, we will briefly discuss the initial animal and human studies which demonstrated the role of androgens in the treatment of anemia, their mechanism of action, a detailed account of the efficacy of androgens in the treatment of various anemias, the erythropoietic side effects of androgens and finally, the relationship between hematocrit levels and cardiovascular disease.

A reliable index for the prognostic significance of blood pressure variability

OBJECTIVES

This study presents a reliable index inspired by the total variability concept of real analysis in mathematics, called average real variability (ARV), for the prognostic significance of blood pressure variability (BPV) overcoming the pitfalls of the commonly used standard deviation (SD).

BACKGROUND

Recent studies have suggested that an increase in BPV is associated with an increase in subsequent cardiovascular events/complications. However, there are other studies where the cited association was not found or was lost in the presence of other well-known risk factors. An explanation for these apparently contradictory results may be the selection of the variability index used (SD).

METHODS

Ambulatory blood pressure monitoring in 312 subjects aged > or = 55 years. Logistic regression models and survival methods were used to establish the prognostic significance of awake systolic BPV: in particular, (i) the performance of ARV versus SD, and (ii) the value of BPV relative to other well-known risk factors.

RESULTS

The analyses using the ARV index show a statistically significant relative risk equal to 4.548 (P = 0.006) for the group with high BPV with respect to the low BPV group (reference level); in contrast, the corresponding relative risk associated to the SD index was not statistically significant. Furthermore, ARV exhibited a similar predictive value to systolic blood pressure.

CONCLUSIONS

The proposed ARV index is a more reliable representation of time series variability than SD and may be less sensitive to the relative low sampling frequency of the ambulatory blood pressure monitoring devices. The results suggest that ARV adds prognostic value to the ABPM and could prompt the use of therapeutic measures to control BPV.

Hematocrit and the risk of coronary heart disease mortality

BACKGROUND

An association between hematocrit (Hct) and coronary heart disease (CHD) mortality has been previously observed. However, the relationship of Hct and CHD independent of other cardiovascular disease (CVD) risk factors and differences between men and women remain unclear.

METHODS

We examined the association between Hct and CHD mortality with Cox regression analyses of data from 8896 adults, aged 30-75 years, in the Second National Health and Nutrition Examination Survey (NHANES II) Mortality Study (1976-1992). Covariates included age, sex, race, education, smoking status, hypertensive status, total serum cholesterol, body mass index, white blood cell count, and history of CVD and diabetes. Hct was categorized by use of sex-specific tertiles, and all analyses were stratified by sex.

RESULTS

During 16.8 years of follow-up, there were 545 (men 343, women 202) deaths from CHD (International Classification of Diseases, 9th revision [ICD-9] 410-414), 778 (men 426, women 279) deaths from diseases of the heart (ICD-9 390-398, 402, 404, 410-414, 415-417, 420-429), and 2046 (men 1216, women 830) all-cause deaths. Among men, the crude CHD mortality rate per 10,000 population was 42.6, 31.9, and 46.3 among those with Hct in the lower, middle, and upper tertiles, respectively. The corresponding crude CHD mortality rates among women were 12.6, 18.6, and 27.7. After adjustment for age and other CVD risk factors, there was no association between Hct in the upper tertile compared with the lower tertile and mortality from either CHD, diseases of the heart, or all causes among men. Women with Hct in the upper tertile were 1.3 times (95% CI 0.9-1.9) more likely to die from CHD than were women with Hct in the lowest tertile, after multivariate adjustment. The effect of high Hct on CHD mortality among women younger than 65 years of age was slightly stronger (relative risk 2.2, 95% CI 1.0-4.6).

CONCLUSIONS

These results suggest that the association between Hct and mortality from CHD and all causes is complex, differing both by sex and age. Further research is needed to gain a better understanding of these age and sex differences.

Platelet activation with unfractionated heparin at therapeutic concentrations and comparisons with a low-molecular-weight heparin and with a direct thrombin inhibitor

BACKGROUND

The growing use of heparin in acute thrombotic disorders, coupled with the availability of many new antithrombotic agents, emphasizes the need for adequate characterization of the platelet effects of the various anticoagulants. Controversial platelet effects have been reported with heparin (eg, enhanced platelet activation in vitro with high doses and no such effect in vivo at therapeutic doses). This study examined platelet receptor activation and platelet aggregation at therapeutic concentrations of unfractionated heparin (UFH), of enoxaparin, a low-molecular-weight heparin, and of argatroban, a direct thrombin inhibitor.

METHODS AND RESULTS

Platelet P-selectin (CD62) and activated GP IIb/IIIa (PAC-1) expression on platelet membrane was quantified in whole blood as well as platelet aggregation in platelet-rich plasma in 43 patients with unstable angina before and during treatment with UFH or enoxaparin. Studies were also carried out in blood of seven normal volunteers after addition ex vivo of UFH (0.25 U/mL), enoxaparin (0.25 U/mL), argatroban (1 ng/mL), and normal saline. UFH in patients with unstable angina increased the percentage of circulating platelets positive to PAC-1 from 2.7+/-1.7% to 4.4+/-3.4% (P<.05) and to CD62 from 1.6+/-0.9% to 2.7+/-1.5% (P<.01). Platelets were also hyperresponsive to stimulation with ADP and with the thrombin-receptor agonist peptide. Aggregation to ADP increased from 6.8+/-4.6% to 11.2+/-7.0% and to TRAP from 5.2+/-3.5% to 11.1+/-6.0% (P<.001). The addition of UFH to blood of normal volunteers resulted also in activation of GP IIb/IIIa receptors, expression of P-selectin, and enhanced platelet aggregation. Enoxaparin had only minor effects on platelet activation in vivo and ex vivo, and argatroban, evaluated ex vivo, had no detectable effects.

CONCLUSIONS

Therapeutic concentrations of UFH are associated with platelet activation.