Platelet aggregability in cerebral thrombosis--analyzed for vessel stenosis

Red Cell Distribution Width-to-Platelet Count Ratio: A Promising Predictor of In-Hospital All-Cause Mortality in Critically Ill Patients with Acute Ischemic Stroke

INTRODUCTION

The red blood cell distribution width-to-platelet ratio (RPR), a novel inflammatory index, has already been proven as a prognostic factor in some other diseases, but its prognostic effect on critically ill patients with acute ischemic stroke (AIS) has been rarely investigated. This study aimed to investigate the association between RPR and in-hospital mortality in these patients.

METHODS

We extracted clinical data from the Medical Information Mart for Intensive Care IV 1.0 database. The primary outcome was in-hospital all-cause mortality of patients with critical AIS. The main independent variable was RPR. To investigate the association between RPR and in-hospital all-cause mortality in patients with critical AIS, multivariable logistic analyses, smooth curve fitting, and stratified analyses were conducted.

RESULTS

In total, 2,673 patients with AIS who were admitted to the intensive care unit were included in the study. In the multivariable analysis, in-hospital mortality was positively related to RPR (odds ratio [OR] 1.28, 95% confidence interval [CI] 1.02-1.59). According to the two-piecewise logistic regression model, we found that the inflection point of RPR was 1.89%. To the left of the inflection point (RPR ≤1.89%), we did not detect any relationship between RPR and in-hospital all-cause mortality (OR [95% CI]: 0.73 [0.41, 1.31], p = 0.2884). In contrast, to the right of the inflection point (RPR >1.89%), RPR was positively related to in-hospital all-cause mortality (OR [95% CI]: 1.61 [1.18, 2.19], p = 0.0027).

CONCLUSIONS

RPR showed a nonlinear relationship with in-hospital all-cause mortality in patients with critical AIS.

Plasma 11-dehydrothromboxane B2: a reliable indicator of platelet hyperfunction in patients with ischemic stroke

The plasma level of 11-dehydrothromboxane B2 (11-dehydroTXB2) is free from artifactual increase during blood sampling, and it can be reliable indicator of TXA2 production in vivo. We have estimated plasma 11-dehydroTXB2 in patients with ischemic stroke. Subjects studied were 29 patients with cerebral thrombosis (62 +/- 9 years old) and 41 healthy controls (61 +/- 7 years old). Plasma 11-dehydroTXB2 and TXB2 were determined by radioimmunoassay. Plasma 11-dehydroTXB2 levels in patients and controls were 5.4 +/- 2.5 and 1.8 +/- 0.9 pg ml, respectively, and the difference was significant (p less than 0.001). Plasma TXB2 also was higher in patients than in controls: 401 +/- 61 vs 311 +/- 51 pg/ml (p less than 0.05). However, the 11-dehydroTXB2 was found to be a more effective parameter to distinguish between stroke patients and controls. Estimation of plasma 11-dehydroTXB2 levels is a reliable method to detect platelet hyperfunction in stroke patients.

Platelet count, mean platelet volume and their relation to prognosis in cerebral infarction

The study was performed on patients with ischaemic cerebral infarction in order to obtain information on serial changes of some platelet parameters and to test their prognostic significance. Platelet count, obtained within 48 h after cerebral infarction, was significantly lower than in the control group (213,611 +/- 65,652 mm-3 vs. 299,525 +/- 60,611 mm-3, P less than 0.001), reaching the normal level on the ninth day and thereafter. The mean platelet volume was significantly greater than in the controls (11.26 +/- 1.29 fl vs. 8.93 +/- 0.93 fl, P less than 0.001), and normalization generally occurred on the forty-fifth day. The mean platelet count was significantly lower in the patients who died than in those who survived (P less than 0.025 and P less than 0.05 respectively on the first to second and fourth day after infarction). The reduction of platelet count and the increase of mean volume appear to be related to an increased platelet consumption in the infarction area, associated with an in vivo platelet activation, as larger platelets are more responsive to platelet activity and aggregability tests. The lower mean platelet count observed in the patients who died suggests that the platelet value might be considered as a prognostic index of cerebral infarction.

Platelet aggregability and in vivo platelet deposition in patients with ischemic cerebrovascular disease--evaluation by indium-111-platelet scintigraphy

In ischemic cerebrovascular disease, it is not clear whether platelet function in vitro actually reflects the situation in vivo. Using indium-111 platelet scintigraphy as a method for detecting platelet activation in vivo, we tried to elucidate this problem. Twenty eight patients with chronic stage of ischemic cerebrovascular disease (CVD) and 17 control subjects were examined. Platelet scintigrams were positive in 9 of 28 patients in CVD, while all were negative in control. A comparison of the results obtained from qualitative platelet imaging and platelet aggregability was performed to evaluate whether threshold aggregation concentration (TAC) grade differed across the three groups (control, CVD patients without platelet deposition and CVD patients with platelet deposition). CVD patients with platelet deposition showed a higher TAC than those patients who did not show platelet deposition (P less than 0.05) or control subjects without platelet deposition (P less than 0.05). These results suggest that some patients in chronic stages of CVD may have active platelet deposition on carotid atheromatous lesions, and presence of platelet deposition in vivo could contribute to reduce platelet reactivity in peripheral blood.

Platelet aggregability in sleep-related stroke

We examined platelet aggregability during nocturnal sleep and daytime wakefulness in patients with a history of sleep-related stroke onset (SOS) and compared it to that of matched awake-onset stroke (AOS) patients and controls without evidence of vascular disease. Aggregability was evaluated in-vitro at least seven weeks following stroke onset. Platelets were more aggregable to ADP, collagen and arachidonic acid (AA) during both sleep and wakefulness in patients with AOS (p less than 0.01). No significant difference in the mean aggregation thresholds during sleeping or waking periods were found between SOS and control groups. However, platelets were significantly more responsive to AA during sleep than during wakefulness in the SOS patients (p less than 0.01). This difference was confined to the subgroup of SOS patients who had experienced nocturnal as opposed to daytime sleep-related stroke onset, suggesting that the observed difference in platelet responsiveness to AA may be related to a circadian fluctuation in platelet aggregability rather than to a sleep-related fluctuation. Significant sleep-related changes in platelet aggregability were not identified in the other two groups.

Evaluation of platelet changes in completed ischemic stroke

In a retrospective study we evaluated the platelet count in 45 patients mean age 73 +/- 9 years, with cerebral infarction (C.I.) documented by CT, and 45 age and sex-matched controls randomly selected. In 12 patients changes in platelet count were examined prospectively, starting from the acute event for 30 days. In the retrospective study the mean platelet count in C.I. was significantly lower than that found in controls: 260, 220 +/- 86,076/mm3 and 302, 422 +/- 65,747/mm3 (p less than 0.05) respectively. In the prospective study the mean count was 213,330 +/- 79,930/mm3. A progressive increase up to the 9-12th day was observed, achieving a mean of 305,630 +/- 83,470/mm3 (p less than 0.01), not statistically different from controls. The 40-45% decrease of platelet count shows that about half of the circulating platelets had rapidly disappeared from the systemic circulation, presumably related to an increase in vivo platelet activation and aggregation.

Activity of platelet-activating factor (PAF) acetylhydrolase in plasma from patients with ischemic cerebrovascular disease

Platelet-activating factor (PAF) is metabolized by a specific enzyme, PAF acetylhydrolase, which may play an important role in the manifestation of the biological activities of PAF in vivo. The activity of PAF acetylhydrolase in plasma of patients with ischemic stroke was higher than that in healthy controls. The incidence of irreversible platelet aggregation in response to PAF, as well as to ADP, was found to be higher in patients than in controls. The patients whose platelets responded with irreversible aggregation to PAF displayed a higher activity of plasma PAF acetylhydrolase than those with only reversible aggregation. In controls, PAF acetylhydrolase activity correlated positively, although weakly, with LDL-cholesterol, which may reflect the major role of LDL in carrying this enzyme. However, since there was no significant difference in plasma levels of lipids and apoproteins between patients and controls (except for apo B) and there was no significant relationship between the enzyme activity and the levels of other lipids and apoproteins, it is unlikely that increased plasma level of PAF acetylhydrolase activity in stroke patients is accounted for by an abnormality of lipoprotein metabolism. Platelet hyperfunction may be associated with augmented generation of PAF, which, in turn, may bring about the induction of the inactivating enzyme, PAF acetylhydrolase.

[Predictor function of hemorheologic parameters with reference to the incidence of manifest circulatory disorders: Concept of the Aachen study]

The prevention of cardiovascular disease has up till now generally been limited to control of the classical risk factors. The primary problem of the risk factor model is, that although a statistically verified relationship exists between risk factors and vascular disease, an individual prognosis is presently impossible. Surveys that show a relation between risk factors and impaired blood fluidity support the conception that a change in blood fluidity could be considered an early detection screening of vascular diseases. Prospective studies have shown that the hematocrit is related to circulatory disturbances. The main aim of the present study was to determine the clinical relevance of rheological parameters (hematocrit, plasma viscosity, erythrocyte rigidity, thrombocyte aggregation, erythrocyte aggregation), and the importance of altered blood fluidity as a predictor of manifest cerebral, cardiac or peripheral vascular disturbance.

Effects of common carotid artery damage on anti-platelet-aggregability and PGI2 production in rats

The effects of vascular damage on platelet function were investigated in rats. Common carotid artery specimens 4 mm in length were dissected from male Wistar rats and exposed to ultrasonic treatment or rubbing of the intimal surface. In some cases, carotis was dissected after ligation for 4 hr. The specimens were fixed on a stirring bar and agitated in platelet-rich plasma added with ADP. After determining platelet aggregability, the plasma was subjected to radioimmunoassay for 6-keto-prostaglandin F1 alpha (6-K-PGF1 alpha). Anti-platelet-aggregability in the arterial specimens was significantly greater in the sonicated, rubbed or ligated specimens than in the intact group, probably due to the effect of prostacyclin (PGI2). The measurement of 6-K-PGF1 alpha levels yielded similar results. Endogenous arachidonic acid in the vessel wall seems to be utilized in the production of PGI2, which probably acts only on local platelets. The findings indicate the presence of a mechanism that inhibits the formation of platelet thrombi by the accelerated production of PGI2 under conditions favorable for the generation of thrombosis.