Platelet Function Testing in Neurovascular Procedures: Tool or Gimmick?

BACKGROUND: Platelet inhibitors are used to prevent thromboembolic complications related to neurovascular stenting (NVS) procedures. Despite substantial inter-individual variability of functional platelet inhibition, the value of platelet function tests (PFT) to assess inhibition remains controversial. OBJECTIVE: This study was conducted to compare differences in thromboembolic complication rates associated with NVS in platelet-inhibited patients with and without PFT. Clinical neurological outcomes were assessed by differences in the modified Rankin Scale (mRS). MATERIALS AND METHODS: One hundred seventeen consecutive patients underwent elective NVS procedures within a 7-year period. All patients received aspirin and clopidogrel 8 days before the procedure. Fifty-two patients were treated without assessment of platelet inhibition, and 65 patients were tested for clopidogrel resistance. When clopidogrel resistance was revealed, corresponding patients were converted to ticagrelor. Changes in mRS and thromboembolic event rates were compared between the 2 cohorts. RESULTS: Thirty-five percent of patients from the cohort subjected to PFT tests showed inadequate platelet inhi-bition under clopidogrel and were converted to ticagrelor. Compared to the non-PFT test -cohort, neurological deficits were significantly reduced (12 vs. 0%; p = 0.009) and a lower number of thromboembolic events was found (12 vs. 3%; p > 0.05) within the test cohort. CONCLUSION: PFT appears to identify patients with clopidogrel resistance prior to NVS procedures. When non-responders are converted to alternative platelet inhibitors, neurological outcomes and thromboembolic complication rates may improve. Consequently, this study provides preliminary evidence that PFT may be a useful clinical tool to enhance procedural safety and improve clinical outcomes in NVS procedures.

Insulin resistance in prostate cancer patients and predisposing them to acute ischemic heart disease.

Lack of insulin or insulin resistance (IR) plays a central role in diabetes mellitus and makes diabetics prone to acute ischemic heart disease (AIHD). It has likewise been found that many cancer patients, including prostate cancer patients die of AIHD. Previously it has been delineated from our laboratory that dermcidin could induce anomalous platelet aggregation in AIHD and also impaired nitric oxide and insulin activity and furthermore dermcidin was also found in a few types of cancer patients. To determine the role of this protein in prostatic malignancy, a retrospective case-control study was conducted and blood was collected from prostate cancer patients and healthy normal volunteers. So, we measured the level of dermcidin protein and analyzed the IR by Homeostasis Model Assessment (HOMA) score calculation. Nitric oxide was measured by methemoglobin method. HDL, glycated hemoglobin (HbA1c), BMI, hs-cTroponin-T were measured for the validation of the patients' status in the presence of Dermcidin isoform-2 (DCN-2). Multiple logistic regression model adjusted for age and BMI identified that the HOMA score was significantly elevated in prostate cancer patients (OR = 7.19, P<0.001). Prostate cancer patients are associated with lower level of NO and higher level of both proteins dermcidin (OR = 1.12, P<0.001) and hs-TroponinT (OR = 1.76, P<0.001). From the results, it can be interpreted that IR plays a key role in the pathophysiology of prostate cancer where dermcidin was the cause of IR through NO inhibition leading to AIHD was also explained by high-sensitive fifth generation cTroponin-T (hs-cTroponinT) and HbA1c level which are associated with endothelial dysfunction.

Kidney Function as a Determinant of HDL and Triglyceride Concentrations in the Australian Population.

BACKGROUND: Chronic kidney disease (CKD) is a potent risk factor for cardiovascular disease (CVD). CVD risk increases in a stepwise manner with increasing kidney impairment and is significantly reduced by kidney transplantation, suggesting a causal relationship. Dyslipidemia, a well recognised CVD risk factor, is highly prevalent in CKD. While dyslipidemia is a risk factor for CKD, kidney impairment can also induce a dyslipidemic state that may contribute to the excess burden of CVD in CKD. We utilised a multipronged approach to determine whether a causal relationship exists. MATERIALS AND METHODS: Retrospective case-control analysis of 816 patients admitted to the Royal Hobart Hospital in 2008-2009 with different degrees of kidney impairment and retrospective before-after cohort analysis of 60 patients who received a transplanted kidney between 1999 and 2009. RESULTS: Decreased estimated GFR (eGFR) was independently associated with decreased high density lipoprotein (HDL, p < 0.0001) and increased triglyceride concentrations (p < 0.01) in multivariate analysis. There was no significant relationship between eGFR and low density lipoprotein (LDL) or total cholesterol in multivariate analysis. Kidney transplantation increased HDL (p < 0.0001) and decreased triglyceride (p = 0.007) concentration, whereas there was no significant change in LDL and total cholesterol. These effects were dependent on maintenance of graft function, statin therapy (those who were on) if graft failure occurred then HDL again decreased and triglycerides increased. CONCLUSIONS: Kidney transplantation ameliorated alterations in plasma lipoprotein profile associated with kidney impairment, an effect that was dependent on the maintenance of graft function. These data suggest that kidney function is a determinant of HDL and triglyceride concentrations in patients with CKD.

Evaluation of hemolysis in microcatheter directed blood infusion at different flow rates for transarterial salvage reperfusion: In-vitro study.

BACKGROUND: Microcatheter directed blood reperfusion is an endovascular salvage option for acute cerebral artery occlusions. It has not been investigated whether this technique may be associated with hemolysis. OBJECTIVE: Analysis of hemolysis during blood infusion through different microcatheters and infusion rates to assess related risks. METHODS: Four microcatheters with different inner diameters were perfused with blood samples at three infusion rates. Hemolytic markers including lactate-dehydrogenase (LDH) and haptoglobin were analyzed. Samples before and after blood infusion were compared using Student's t-test. Flow-related degree of hemolysis was analyzed with regression analysis. Resulting shear stress was calculated and correlated with LDH and haptoglobin. RESULTS: Significant increase of LDH and decrease of haptoglobin was found after blood reperfusion through small microcatheters at progressive flow rates (p<0.05). No hemolysis was found with larger diameter microcatheters at all flow rates (p>0.05). Correlation between shear stress, LDH and haptoglobin was r=0.86 and r=0.75, respectively. CONCLUSIONS: Progressive hemolysis occurs during blood perfusion of small lumen microcatheters at increasing flow rates. This phenomenon may be related to turbulent flow, exposure time and increased shear stress. Larger microcatheters did not induce hemolysis and may be the preferred choice for stroke reperfusion.

Reduction of death rate due to acute myocardial infarction in subjects with cancers through systemic restoration of impaired nitric oxide.

INTRODUCTION: Excessive aggregation of platelets at the site of plaque rupture on the coronary artery led to the formation of thrombus which is reported to precipitate acute myocardial infarction (AMI). Nitric oxide (NO) has been reported to inhibit platelet aggregation and induce thrombolysis through the in situ formation of plasmin. As the plasma NO level in AMI patients from two different ethnic groups was reduced to 0 µM (median) compared to 4.0 µM (median) in normal controls, the effect of restoration of the NO level to normal ranges on the rate of death due to AMI was determined. METHODS AND RESULTS: The restoration of plasma NO level was achieved by a sticking small cotton pad (10×25 mm) containing 0.28 mmol sodium nitroprusside (SNP) in 0.9% NaCl to the abdominal skin of the participants using non-toxic adhesive tape which was reported to normalize the plasma NO level. The participants (8,283) were volunteers in an independent study who had different kinds of cancers and did not wish to use any conventional therapy for their condition but opted to receive SNP "pad" for their condition for 3 years. The use of SNP "pad" which normalized (≈4.0 µM) the plasma NO level that in consequence reduced the death rate due to AMI, among the participants, was found to be significantly reduced compared to the death due to AMI in normal population. CONCLUSION: Our data suggested that the use of SNP "pad" significantly reduced the death due to AMI. TRIAL REGISTRATION: www.ctri.nic.in CTRI/2013/12/004236.

Isolation and study of insulin activated nitric oxide synthase inhibitory protein in acute myocardial infarction subjects.

Insulin inhibits platelet aggregation through nitric oxide synthesis by stimulating platelet insulin activated nitric oxide synthase. Impaired platelet insulin activated nitric oxide synthase in acute myocardial infarction (AMI) patients had been reported and thus our aim was to identify and isolate the factors impairing insulin activated nitric oxide in acute myocardial infarction patients' plasma and study its effect on platelets aggregation in vitro. The insulin activated nitric oxide synthase inhibitor was identified as a protein and was purified from the plasma of AMI subjects using DEAE cellulose and Sephadex G-50 column, molecular weight determined by SDS-PAGE, nitric oxide quantified by methaemoglobin method, inhibitor protein quantified in plasma by immunoblot and ELISA, platelet aggregation studies done using an aggregometer, thromboxane-A2 in the platelets determined by radioimmunoassay, (125)I-insulin radioligand binding studies done using normal subject platelets. The purified nitric oxide synthase inhibitor protein was ~66 kDa, concentration in AMI subjects' plasma varied from 114 to 9,090 µM and was undetected in normal subjects' plasma. The inhibitor protein competes with insulin for insulin receptor binding sites. The Incubation of the normal subject PRP with 5.0 µM inhibitor for 30 min followed by 0.4 µM ADP addition caused platelet aggregation in vitro, 130 µM aspirin or 400 µU insulin/ml addition was able to abrogate 0.4 µM ADP induced platelet aggregation even in the presence of 5.0 µM inhibitor. A potent inhibitory protein against insulin activated nitric oxide synthase in platelets appears in circulation of AMI subjects impairing nitric oxide production, potentiating ADP induced platelet aggregation and increasing the thromboxane-A2 level in platelets.

The aetiology of severe anaemia among antenatal patients of the Port Moresby General Hospital.

Between October 1998 and September 2000, 111 consecutive pregnant patients admitted to the Port Moresby General Hospital antenatal ward with a haemoglobin level of 6 g/dl or less were studied. The main causes of the severe anaemia were as follows: iron deficiency on its own or in combination with another factor 66%--iron deficiency on its own 43% and combined folate and iron deficiency 23%--and folate deficiency 18%. Malaria was a contributory factor in 13 patients (12%). A combination of blood film, bone marrow study, serum assays of ferritin, folate and vitamin B12, and mean corpuscular volume (MCV) was used to determine the cause of the anaemia. Ferritin levels on their own poorly correlated with the presence of iron in the bone marrow. A low MCV correlated well with iron deficiency anaemia while a high MCV was associated with folic acid deficiency. It would seem therefore that while a bone marrow study is mandatory to reach a definitive diagnosis of severe anaemia, MCV, in conjunction with the red cell morphology on blood film, would be a good marker for iron and folic acid deficiency anaemia, especially as we do not have serum assays readily available for folate, ferritin and vitamin B12 in Papua New Guinea.

Inhibition of human blood platelet aggregation and the stimulation of nitric oxide synthesis by aspirin.

Incubation of platelet-rich plasma with 80 microM aspirin that resulted in the inhibition of both the secondary phase of ADP induced platelet aggregation and prostaglandin synthesis simultaneously stimulated the production of NO in platelets. Furthermore it was found that the treatment of platelet-rich plasma either with 80 microM ibuprofen or salicylic acid, like aspirin, which inhibited the secondary phase of platelet aggregation by ADP and prostaglandin synthesis, also stimulated the production of NO in the absence of added ADP. However the inhibition of prostaglandin synthesis by ibuprofen or salicylic acid, unlike aspirin, was transient in nature. Incubation of washed platelets with any of these three compounds also stimulated NO synthesis indicating that the effect of these compounds was not mediated through plasma proteins. The in vitro effect of aspirin on the increase of NO in platelets could also be demonstrated by in vivo exposure of platelets to the compound. It was concluded that either a temporary or a lasting inhibition of prostaglandin synthesis by these inhibitors resulted in the synthesis of NO in resting platelets. Since NO is a potent inhibitor of platelet aggregation the inhibition of platelet aggregation, by these compounds may not be the consequence of the inhibition of prostaglandin synthesis alone, but could also be related, at least partly, to the stimulated synthesis of NO by these inhibitors.

Neutralization by "antineoplastin" of insulin-activated nitric oxide synthase antibody and its effects in cancers.

PURPOSE: The plasma level of nitric oxide (NO), that has been reported to possess various antineoplastic properties, was found to be diminished due to the impairment of insulin-activated nitric oxide synthase (IANOS) as a result of the appearance of a novel antibody (free light chain of IgG, M(r) 44 kD) against the enzyme in the circulation in various cancers compared to normal control. METHODS: We report here two NO-generating agents, antineoplastin I (a protein, M(r) 5000) and antineoplastin II (an inorganic compound), which when applied to the skin of cancer patients were capable of neutralizing the antibody in vivo through the production of NO in the skin cells due to the stimulation of membrane IANOS of these cells and, subsequently, in erythrocytes in the circulation. RESULTS: Neither antineoplastin I nor antineoplastin II itself enters into the circulation but due to the application of these agents on the skin, the NO synthesis in erythrocytes was normalized in these patients through "feedback" activation and amplification of IANOS activity by NO itself. CONCLUSION: It was found that the resumption of NO synthesis through the neutralization of antibody resulted in favorable modifications of various cancer-associated pathophysiologic consequences.