Over 45 years ago, Montreal Platelet Syndrome was first described as a rare inherited platelet disorder characterised by macrothrombocytopenia with spontaneous platelet clumping, abnormal platelet shape change upon stimulation and a defect in platelet calpain. This syndrome has now been reclassified as type 2B von Willebrand disease with the V1316M VWF mutation in the only kindred ever reported. We herein revisit the historical platelet characteristics originally described in Montreal Platelet Syndrome in light of the new diagnosis. This paper will review the 45-year saga of Montreal Platelet Syndrome, a story that highlights the value of revisiting a rare diagnosis to look for a more common explanation.
The proportion of identifiable causes of familial thrombophilia has increased from 5-10% to 60-70% since the identification of activated protein C resistance (aPCR) in February 1993 by Dahlbäck et al. A mutation in the factor V gene (G-->A, 1691) leads to the so called Leiden mutation (R 506 Q) that produces a mutated factor V resistant to the catalytic action of activated protein C (aPC), yet normal in its procoagulant properties. This recently identified aPCR is in Nordic populations the most prevalent and well defined genetic defect associated with disease so far described. Its prevalence in the general population ranges from 0% to up to 15% and suggests that a positive genetic selection pressure has been involved. The aPCR phenotype can be assessed in vitro by measurement of the prolongation of the activated partial thromboplastin time in the presence of aPC, whereas the aPCR genotype is studied using polymerase chain reaction searching for the Arg to Gln mutation in the coagulation factor V gene. Some acquired conditions such as the presence of lupus anticoagulants, antiphospholipid antibodies, pregnancy, liver disease and contraceptives may lead into the aPCR phenotype. The aPCR search must be the initial step in the study of a patient with thrombophilia, either inherited or acquired aPCR together with protein C, protein S and antithrombin III explain 60 to 70% of cases of familial thrombophilia.
Background Heparin dosage for anticoagulation during cardiopulmonary bypass (CPB) is commonly calculated based on the patient's body weight. The protamine-heparin ratio used for heparin reversal varies widely among institutions (0.7-1.3?mg protamine/100 IU heparin). Excess protamine may impair coagulation. With an empirically developed algorithm, the HeProCalc program, heparin, and protamine doses are calculated during the procedure. The primary aim was to investigate whether HeProCalc-based dosage of heparin could reduce protamine use compared with traditional dosages. The secondary aim was to investigate whether HeProCalc-based dosage of protamine affected postoperative bleeding. Patients and Methods We consecutively randomized 40 patients into two groups. In the control group, traditional heparin and protamine doses, based on body weight alone, were given. In the treatment group, the HeProCalc program was used, which calculated the initial heparin bolus dose from weight, height, and baseline activated clotting time and the protamine dose at termination of CPB. Results We analyzed the results from 37 patients, after exclusion of three patients. Equal doses of heparin were given in both groups, whereas significantly lower mean doses of protamine were given in the treatment group versus control group (211?±?56 vs. 330?±?61?mg, p?
Coumarin derivatives and anticonvulsants administered during pregnancy enter the fetal circulation, interfering with the action of vitamin K. Vitamin K plays a crucial part in the gamma-carboxylation of glutamic acid residues of the vitamin K-dependent coagulation factors prothrombin, FVII, FIX, and FX. Other vitamin K-dependent proteins in the coagulation cascade are protein C and protein S. Vitamin K-dependent bone proteins are osteocalcin and gamma-carboxyglutamate matrix protein. Administration of coumarol derivatives results in under carboxylation of the vitamin K-dependent proteins. Anticoagulation therapy with warfarin is followed by an increased risk of embryopathy, which has been shown to be greatest between gestational weeks 6 and 12. Administration of warfarin is also followed by an increased risk both of fetal intraventricular hemorrhage, and of cerebral microbleedings, which may result in microencephaly and mental retardation. Treatment with coumarol derivatives should therefore be avoided during pregnancy, even in pregnant women with artificial heart valves, and replaced by heparin. Hemorrhage in the newborn related to the use of anticonvulsant drugs during pregnancy occurs very early within the first 24 hours, probably due to increased degradation of vitamin K. Transplacental administration of vitamin K has been shown to prevent neonatal hemorrhage induced by maternal anticonvulsant therapy. Prophylactic administration of vitamin K, especially by intramuscular injection, has been reported to be associated with an increased risk of childhood cancer. However, subsequent extensive studies have yielded no evidence of any relationship between prophylactic vitamin K administration and the occurrence of childhood cancer.
In vitro and in vivo experiments showed that anticoagulant activity of sulfated polysaccharide from Fucus evanescens (brown algae of the Okhotsk Sea) was similar to that of heparin. Anticoagulant properties of fucoidan are determined by thrombin inhibition mediated via plasma antithrombin III.
Upper Gastrointestinal Surgery Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden; Unit of Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
Anticoagulant treatment might enhance the natural defense against tumor cell dissemination caused by diagnostic needle biopsy by counteracting thrombocyte coating of such cells. To clarify whether women using anticoagulant treatment at the time of biopsy have a lower occurrence of lymph node metastasis, we conducted a nationwide Swedish cohort study of 26,528 female incident breast cancer patients in 2006-2011. Point risk ratio (RR) of risk of lymph node metastasis among users of anticoagulant treatment adjusted for age, T-stage, socioeconomic factors, and concomitant medication was RR?=?0.94, (95% CI: 0.87-1.03), and lower in younger women (RR?=?0.80, 95% CI 0.50-1.29). Although nonsignificant, these associations may underestimate a true negative association since women using anticoagulant treatment are likely to have more concomitant diseases, lead an unhealthier lifestyle, and have lower participation in mammography screening. These findings provide some support for the hypothesis that anticoagulant medications might counteract breast cancer spread caused by needle biopsy.
To examine anticoagulation management at the Bella Coola Medical Clinic in British Columbia.
Charts of all patients in the Bella Coola Valley receiving warfarin were assessed. Data were analyzed using Microsoft Excel.
Bella Coola Medical Clinic on the remote central coast of British Columbia.
Twenty-one patients at the Bella Coola Medical Clinic who were receiving warfarin.
All international normalized ratio (INR) tests over the preceding 12 months were examined for results, time elapsed since previous test, and interval until next scheduled test.
An in-range INR rate of 60% is considered acceptable for anticoagulation services. The clinic had performed 406 INR tests on these 21 patients over the last 12 months. We found that 53% of all INR results fell strictly within the recommended therapeutic range. The relative success of anticoagulation management in Bella Coola probably results from several factors. For instance, physicians usually responded to out-of-range INR results with close monitoring: in 71% of cases, follow-up tests were scheduled within 1 week. On average, patients attended 77% of these visits on schedule; 58% of all out-of-range INR results were followed up with retesting within 1 week.
Our results suggest that primary care physicians can manage anticoagulation adequately, even in remote settings.
Anticoagulation in patients undergoing atrial fibrillation (AF) ablation is crucial to minimize the risk of thromboembolic complications. There are broad ranges of approaches to anticoagulation management pre and post AF ablation procedures. The purpose of this study was to determine the anticoagulation strategies currently in use in patients peri- and post AF ablation in Canada.
A Web-based national survey of electrophysiologists performing AF ablation in Canada collected data regarding anticoagulation practice prior to ablation, periprocedural bridging, and duration of postablation anticoagulation.
The survey was completed by 36 (97%) of the 37 electrophysiologists performing AF ablation across Canada. Prior to AF ablation, 58% of electrophysiologists started anticoagulation for patients with paroxysmal AF CHADS(2) scores of 0 to 1, 92% for paroxysmal AF CHADS(2) scores = 2, 83% for persistent AF CHADS(2) scores of 0 to 1, and 97% for persistent AF CHADS(2) scores = 2. For patients with CHADS(2) 0 to 1, warfarin was continued for at least 3 months by most physicians (89% for paroxysmal and 94% for persistent AF). For patients with CHADS(2) = 2 and with no recurrence of AF at 1 year post ablation, 89% of physicians continued warfarin.
Although guidelines recommend long-term anticoagulation in patients with CHADS(2) = 2, 11% of physicians would discontinue warfarin in patients with no evidence of recurrent AF 1 year post successful ablation. Significant heterogeneity exists regarding periprocedural anticoagulation management in clinical practice. Clinical trial evidence is required to guide optimal periprocedural anticoagulation and therapeutic decisions regarding long-term anticoagulation after an apparently successful catheter ablation for AF.
Notes
Comment In: Can J Cardiol. 2013 Feb;29(2):139-4122819445
