P2Y12, a new platelet ADP receptor, target of clopidogrel

Clopidogrel is a potent antithrombotic drug that inhibits ADP-induced platelet aggregation. The results of large clinical trials have demonstrated an overall benefit of clopidogrel over aspirin in the prevention of vascular ischemic events (myocardial infarction, stroke, vascular death) in patients with a history of symptomatic atherosclerotic disease. The antiaggregating effect of clopidogrel is attributed to an irreversible inhibition of ADP binding to a purinergic receptor present at the platelet surface. Clopidogrel is not active in vitro and can be considered a precursor of an active metabolite formed in the liver. The chemical structure of this active metabolite and its biological activity have been described recently. Several purinergic receptors have been described on platelets; P2X (1), a calcium channel, and P2Y1 a Gq-coupled seven-transmembrane domain receptor, have been found not to be antagonized by clopidogrel. Another Gi (2)-coupled receptor (named P2Y12) has been recently cloned and stably expressed in CHO cells. These cells displayed a strong affinity for (33)P-2MeS-ADP, a stable analogue of ADP, the binding characteristics of which corresponded in all points to those observed on platelets. The binding of (33)P-2MeS-ADP to these cells was strongly inhibited by the active metabolite of clopidogrel with a potency that was consistent with that observed for this compound on platelets. In these transfected CHO cells, as in platelets, ADP and 2MeS-ADP induced adenylyl cyclase downregulation, an effect that was inhibited by the active metabolite of clopidogrel. These results demonstrate that this receptor corresponds to the previously called "P2t" platelet receptor and show that the active metabolite of clopidogrel binds in a covalent manner to this receptor, thus explaining how it blocks the aggregating effect of ADP on platelets.     

Immunological consequence of renal transplantation and immunosuppression. I. Alterations in human natural killer-cell activity

The role and activity of natural killer (NK) cells following renal transplantation remain unknown. To monitor NK activity, a⁵¹Cr release of K-562 targets in prednisone-and azathioprine-treated patients receiving renal allografts was utilized. In 18 patients in whom NK activity was measured prior to and after transplantation, a significant diminution in NK activity within 3 weeks following transplantation was demonstrated compared to pretransplant values (34.71 vs 12.20%, respectively;P<0.001). In 11 subjects who had NK activity assayed at various intervals after transplantation but not prior to allografting, mean NK values were markedly lower (mean, 14.2%) than those of normal volunteers or patients maintained on hemodialysis (P<0.001). The latter two control groups demonstrated no difference (P = NS) in mean NK activity (39.46 vs 35.82%, respectively). In 5 of the 29 patients evaluated with good long-term graft function (mean, 2.7 years), restitution of normal NK activity was demonstrated. In two patients with bacterial infections, NK activity increased from 39.29 to 51.7% and from 13.54 to 20.00%. After infection, these values were 35.3% in the former and 3.39% in the latter. Viral infection did not appear to affect NK activity significantly. NK activity was increased in only one of seven patients with documented rejection episodes. In three of such patients, NK activity declined significantly following pulse methylprednisolone therapy. These results indicate that (1) NK-cell activity significantly decreases immediately after transplantation, probably as a result of immunosuppressive therapy; (2) NK activity does not appear to be stimulated by the alloreactive rejection process; (3) NK activity may be augmented in the course of bacterial but not viral infections; and (4) long-term allograft survival may be associated with a restoration of NK-cell levels in certain recipients.     

Post–traumatic headache from moderate head injury

The onset of post-traumatic headache occurs frequently in children, where it is often caused by severe head injuries, therefore, it is part of a post–traumatic syndrome, rather than of an independent headache and in this case no cause is clearly evident. The problem, conversely, arises in post–traumatic headache after a light trauma, since it is difficult to establish the cause–effect link. We have studied PTH incidence for one year in the patients of the emergency ward of the Saint Charles of Nancy Hospital, compared to the activity of 4 Italian headache centres. At the Saint Charles of Nancy Hospital of 98 patients with PTH after a moderate head trauma, 18 had acute and 26 chronic PTH, the majority ceased after six months. In the Italian headache centres 1,656 patients were examined, of these 3.2% suffered from PTH: 25 acute, 29 chronic. These data confirm the poor evidence of PTH after a light trauma and lead to doubt of the existence of this nosological entity.     

Therapeutic Approach in Patients with a Floating Thrombus in the Right Heart

Background

The occurrence of a floating thrombus in the right heart, although rare, is a life-threatening condition requiring a specific approach. In most cases, these thrombi are a result of embolization from deep venous thrombosis, and have lodged temporarily in the right heart. The management of this condition is variable, depending on whether or not there is a thrombus entrapped within a foramen ovale (FO).

Objectives

To present the management of 2 patients with a free-floating thrombus in the right heart, and a third patient with an entrapped thrombus in the FO.

Case Reports

Two patients with a free-floating thrombus in the right atrium who were treated with thrombolytic therapy had an immediate excellent outcome. The patient with a thrombus entrapped within the FO was scheduled for surgical removal of the thrombus due to an unacceptable risk of systemic embolization if treated with thrombolytic and anticoagulant therapy. Unfortunately, he developed an ischemic stroke on the fifth day of presentation, just a few hours before the scheduled surgery, despite meticulous monitoring of continuous heparin infusion with activated partial thromboplastin time.

Conclusion

Thrombolytic therapy is recommended in patients with a free-floating thrombus in the right heart. However, in patients with a thrombus entrapped within an FO, delaying surgical removal of the thrombus may be deleterious due to unpredictable systemic embolization.     

International Headache Society classification: interobserver reliability in the diagnosis of primary headaches

We assessed interobserver reliability of the International Headache Society (IBIS) classification for diagnosis of primary headaches. The study was performed on 103 patients consecutively seen at two Headache Centres. Each patient was given a structured interview recorded on videotape. Four experienced clinicians then reviewed the interviews separately and made a diagnosis of headache according to IHS criteria at the one- and two-digit levels. At both the one- and the two-digit level the agreement was substantial (Kappa = 0.74 and 0.65, respectively). The analysis of reliability for each of nine items necessary for diagnosis showed an agreement ranging from substantial (Kappa = 0.69) to almost perfect (Kappa = 0.89). Our results indicate that the IHS classification has a good reliability for the diagnosis of primary headaches at the one- and two-digit levels.     

Efficacy of frovatriptan in the acute treatment of menstrually related migraine: analysis of a double-blind,randomized, cross-over,multicenter, Italian,comparative study versus rizatriptan

The objectives of this study are to assess the efficacy and safety of frovatriptan, and rizatriptan in the subgroup of women with menstrually related migraine of a multicenter, randomized, double blind, cross-over study. Each patient received frovatriptan 2.5 mg or rizatriptan 10 mg in a randomized sequence: after treating 3 episodes of migraine in not more than 3 months with the first treatment, the patient had to switch to the other treatment. Menstrually related migraine was defined according to the criteria listed in the Appendix of the last IHS Classification of Headache disorders. 99 out of the 125 patients included in the intention-to-treat analysis of the main study were of a female gender: 93 had regular menstrual cycles and were, thus, included in this analysis. A total of 49 attacks classified as menstrually related migraine were treated with frovatriptan and 59 with rizatriptan. Rate of pain relief at 2 h was 58% for frovatriptan and 64% for rizatriptan (p = NS), while rate of pain free at 2 h was 31 and 34% (p = NS), respectively. At 24 h, 67 and 81% of frovatriptan-treated, and 61 and 74% of rizatriptan-treated patients were pain free and had pain relief, respectively (p = NS). Recurrence at 24 h was significantly (p < 0.01) lower with frovatriptan (10 vs. 32% rizatriptan). Frovatriptan was as effective as rizatriptan in the immediate treatment of menstrually related migraine attacks while showing a favorable sustained effect with a lower rate of migraine recurrence. These results need to be confirmed by randomized, double-blind, prospective, large clinical trials.     

HLA-DRB4 as a genetic risk factor for Churg-Strauss syndrome

OBJECTIVE: To explore the association between HLA alleles and Churg-Strauss syndrome (CSS), and to investigate the potential influence of HLA alleles on the clinical spectrum of the disease. METHODS: Low-resolution genotyping of HLA-A, HLA-B, and HLA-DR loci and genotyping of TNFA -238A/G and TNFA -308A/G single-nucleotide polymorphisms were performed in 48 consecutive CSS patients and 350 healthy controls. RESULTS: The frequency of the HLA-DRB1*07 allele was higher in the CSS patients than in controls (27.1% versus 13.3%; chi(2) = 12.64, P = 0.0003, corrected P [P(corr)] = 0.0042, odds ratio [OR] 2.42, 95% confidence interval [95% CI] 1.47-3.99). The HLA-DRB4 gene, present in subjects carrying either HLA-DRB1*04, HLA-DRB1*07, or HLA-DRB1*09 alleles, was also far more frequent in patients than in controls (38.5% versus 20.1%; chi(2) = 16.46, P = 0.000058, P(corr) = 0.000232, OR 2.49, 95% CI 1.58-3.09). Conversely, the frequency of the HLA-DRB3 gene was lower in patients than in controls (35.4% versus 50.4%; chi(2) = 7.62, P = 0.0057, P(corr) = 0.0228, OR 0.54, 95% CI 0.35-0.84). CSS has 2 major clinical subsets, antineutrophil cytoplasmic antibody (ANCA)-positive, with features of small-vessel vasculitis, and ANCA-negative, in which organ damage is mainly mediated by tissue eosinophilic infiltration; analysis of HLA-DRB4 in patients categorized by different numbers of vasculitic manifestations (purpura, alveolar hemorrhage, mononeuritis multiplex, rapidly progressive glomerulonephritis, and constitutional symptoms) showed that its frequency strongly correlated with the number of vasculitis symptoms (P for trend = 0.001). CONCLUSION: These findings indicate that HLA-DRB4 is a genetic risk factor for the development of CSS and increases the likelihood of development of vasculitic manifestations of the disease.     

No association between immunization and Guillain-Barré syndrome in the United Kingdom, 1992 to 2000

BACKGROUND: Our goal was to determine whether immunization is associated with the incidence of Guillain-Barré syndrome (GBS). METHODS: We analyzed data for all patients registered with 253 general practices in the United Kingdom General Practice Research Database from 1992 to 2000, with a mean of 1.8 million registered patients. We identified new occurrences of GBS and estimated age- and sex-specific and age-standardized incidence rates. We then determined whether the date of diagnosis was made within 42 days of any immunization and estimated the relative risk of diagnosis following immunization after adjusting for age and sex. RESULTS: There were 228 incident cases of GBS, including 107 women and 121 men. The age-standardized incidence rate per 100 000 person-years was 1.22 (95% confidence interval [CI], 0.98-1.46) in women and 1.45 (95% CI, 1.19-1.72) in men. Age-specific incidence rates per 100 000 person-years were highest in men aged 65 to 74 years (3.86; 95% CI, 2.50-5.70) and women aged 75 to 84 years (2.54; 95% CI, 1.39-4.27). There were 7 cases (3.1%) in which the onset occurred within 42 days of any immunization; 3 of the 7 cases occurred after influenza immunization. There were 221 cases (97.0%) that were not associated with immunization. The adjusted relative risk during the 42 days after immunization was 1.03 (95% CI, 0.48-2.18; P = .94). CONCLUSIONS: There is either minimal or no risk of GBS associated with routine immunization practice in the United Kingdom. Obtaining a precise estimate of any potential risk associated with an individual vaccine would require a study with more GBS cases.     

Cangrelor for patients undergoing percutaneous coronary intervention: evidence from a meta-analysis of randomized trials

Cangrelor is a new parenteral adenosine diphosphate P2Y12 receptor inhibitor with rapid, profound and reversible inhibition of platelet activity. The aim of this meta-analysis was to evaluate efficacy and safety of this new agent in patients undergoing percutaneous coronary intervention (PCI). We searched PubMed, Cochrane Library, EMBASE, Web of Science and CINAHL databases from the inception through April 2013. Randomized controlled trials (RCTs) comparing cangrelor with control (clopidogrel/placebo) were selected. We used the random-effects models to calculate the risk ratio. The primary efficacy outcome was risk of myocardial infarction, and the primary safety outcome was TIMI major bleeding at 48 h. Three RCTs included a total of 25,107 participants. Effects of Cangrelor were not different against comparators for myocardial infarction (MI) (Risk ratio [RR] 0.94, 95 % confidence interval [CI] 0.78–1.13) and all-cause mortality (RR 0.72, 95 % CI 0.36–1.43). However, cangrelor significantly reduced the risk of ischemia-driven revascularization (RR 0.72, 95 % CI 0.52–0.98), stent thrombosis (RR 0.60, 95 % CI 0.44–0.82) and Q wave MI (RR 0.53, 95 % CI 0.30–0.92) without causing extra major bleeding (Thrombolysis in Myocardial infarction criteria) and severe or life-threatening bleeding (Global utilization of streptokinase and tissue plasminogen activator for occluded coronary arteries criteria). Separate analysis against only clopidogrel also showed similar findings except Q wave MI outcome. Use of cangrelor during PCI might reduce the risk of ischemia-driven revascularization and stent thrombosis, without causing extra major bleeding.