Development of a Multivariable Model to Predict the Need for Bone Marrow Sampling in Persons With Monoclonal Gammopathy of Undetermined Significance : A Cohort Study Nested in a Clinical Trial

BACKGROUND

Monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) are asymptomatic precursor conditions to multiple myeloma and related disorders. Smoldering multiple myeloma is distinguished from MGUS by 10% or greater bone marrow plasma cells (BMPC) on sampling, has a higher risk for progression, and requires specialist management.

OBJECTIVE

To develop a multivariable prediction model that predicts the probability that a person with presumed MGUS has 10% or greater BMPC (SMM or worse by bone marrow criteria) to inform the decision to obtain a bone marrow sample and compare its performance to the Mayo Clinic risk stratification model.

DESIGN

iStopMM (Iceland Screens, Treats or Prevents Multiple Myeloma), a prospective population-based screening study of MGUS. (ClinicalTrials.gov: NCT03327597).

SETTING

Icelandic population of adults aged 40 years or older.

PATIENTS

1043 persons with IgG, IgA, light-chain, and biclonal MGUS detected by screening and an interpretable bone marrow sample.

MEASUREMENTS

Monoclonal gammopathy of undetermined significance isotype; monoclonal protein concentration; free light-chain ratio; and total IgG, IgM, and IgA concentrations were used as predictors. Bone marrow plasma cells were categorized as 0% to 4%, 5% to 9%, 10% to 14%, or 15% or greater.

RESULTS

The c-statistic for SMM or worse was 0.85 (95% CI, 0.82 to 0.88), and calibration was excellent (intercept, -0.07; slope, 0.95). At a threshold of 10% predicted risk for SMM or worse, sensitivity was 86%, specificity was 67%, positive predictive value was 32%, and negative predictive value was 96%. Compared with the Mayo Clinic model, the net benefit for the decision to refer for sampling was between 0.13 and 0.30 higher over a range of plausible low-risk thresholds.

LIMITATION

The prediction model will require external validation.

CONCLUSION

This accurate prediction model for SMM or worse was developed in a population-based cohort of persons with presumed MGUS and may be used to defer bone marrow sampling and referral to hematology.

PRIMARY FUNDING SOURCE

International Myeloma Foundation and the European Research Council.

Prior cancer and risk of monoclonal gammopathy of undetermined significance: a population-based study in Iceland and Sweden

There is some evidence that a prior cancer is a risk factor for the development of multiple myeloma (MM). If this is true, prior cancer should be associated with higher prevalence or increased progression rate of monoclonal gammopathy of undetermined significance (MGUS), the precursor of MM and related disorders. Those with a history of cancer might therefore present a target population for MGUS screening. This two-part study is the first study to evaluate the relationship of MGUS and prior cancers. First, we evaluated whether prior cancers were associated with having MGUS at the time of screening in the Iceland Screens Treats or Prevents Multiple Myeloma (iStopMM) study that includes 75,422 individuals screened for MGUS. Next, we evaluated the association of prior cancer and the progression of MGUS to MM and related disorders in a population-based cohort of 13,790 Swedish individuals with MGUS. A history of prior cancer was associated with a modest increase in the risk of MGUS (odds ratio (OR)= 1.10; 95% confidence interval (CI): 1.00-1.20). This excess risk was limited to prior cancers in the year preceding MGUS screening. A history of prior cancer associated with the progression of MGUS, except for myeloid malignancies which were associated with lower risk of progression (hazard ratio (HR)=0.37; 95%CI: 0.16-0.89; p=0.028). Our findings indicate that a prior cancer are not a significant aetiological factor in plasma cell disorders. The findings do not warrant MGUS screening or different management of MGUS in those with a prior cancer.

A rare IL33 loss-of-function mutation reduces blood eosinophil counts and protects from asthma

IL-33 is a tissue-derived cytokine that induces and amplifies eosinophilic inflammation and has emerged as a promising new drug target for asthma and allergic disease. Common variants at IL33 and IL1RL1, encoding the IL-33 receptor ST2, associate with eosinophil counts and asthma. Through whole-genome sequencing and imputation into the Icelandic population, we found a rare variant in IL33 (NM_001199640:exon7:c.487-1G>C (rs146597587-C), allele frequency = 0.65%) that disrupts a canonical splice acceptor site before the last coding exon. It is also found at low frequency in European populations. rs146597587-C associates with lower eosinophil counts (β = -0.21 SD, P = 2.5×10^–16, N = 103,104), and reduced risk of asthma in Europeans (OR = 0.47; 95%CI: 0.32, 0.70, P = 1.8×10^–4, N cases = 6,465, N controls = 302,977). Heterozygotes have about 40% lower total IL33 mRNA expression than non-carriers and allele-specific analysis based on RNA sequencing and phased genotypes shows that only 20% of the total expression is from the mutated chromosome. In half of those transcripts the mutation causes retention of the last intron, predicted to result in a premature stop codon that leads to truncation of 66 amino acids. The truncated IL-33 has normal intracellular localization but neither binds IL-33R/ST2 nor activates ST2-expressing cells. Together these data demonstrate that rs146597587-C is a loss of function mutation and support the hypothesis that IL-33 haploinsufficiency protects against asthma.

Only a few genes have been found to play a role in asthma. These include the genes IL33 and IL1RL1, and sequence variants in the human genome close to these genes were initially found to affect the number of eosinophils, cells that play a role in inflammation of the airways in asthma. Based on this knowledge, we decided to use high resolution sequencing technology to search for variants in these genes that cause changes in structure and function of the proteins they encode. We found a rare (0.65%) sequence variant in the IL33 gene, that causes less production of the IL33 protein and some of the protein formed lacks the capacity to bind to its receptor on cells and promote inflammation. This rare mutation causes reduced number of eosinophils in blood and protects against asthma. These results suggest that drugs that could interfere with the inflammatory activity of the IL33 protein may be beneficial for treatment of asthma.

Fiix-prothrombin time monitoring improves warfarin anticoagulation outcome in atrial fibrillation: a systematic review of randomized trials comparing Fiix-warfarin or direct oral anticoagulants to standard PT-warfarin

BACKGROUND

Monitoring warfarin with Fiix-prothrombin time (Fiix-PT), which is only affected by coagulation factors II and X, stabilizes anticoagulation and reduces thromboembolism compared to PT/INR monitoring. We compared outcome in nonvalvular atrial fibrillation (NVAF) patients treated with Fiix-warfarin, direct oral anticoagulants (DOACs), or PT-warfarin.

METHODS

A systematic efficacy and safety assessment by retrieving data from the Fiix trial and the four major phase III DOAC trials in NVAF. Prespecified outcomes included stroke and systemic embolism (SSE), SSE and myocardial infarction (MI), major bleeding (MB), composite major vascular events (SSEMI and MB; CMVE), and deaths. We calculated relative risk, 95% CI, and 95% confidence limits (CL) for each outcome and performed meta-analysis using fixed- and random-effects modeling.

RESULTS

There were 613 and 628 observation years with Fiix-warfarin and PT-warfarin in the Fiix trial, and 70 628 and 57 962 with DOACs and PT-warfarin in DOAC trials. Populations were comparable although death rates were lower in the Fiix trial. Compared to pooled PT-warfarin, Fiix-warfarin reduced SSE (RR 0.54;95% CI 0.26-1.10/95% CL <1.00), SSEMI (0.51;0.26-0.99/<0.90), MB (RR 0.63;0.37-1.07/<0.99), and CMVE (RR 0.66;0.43-1.00/<0.94). Vascular death was lower (RR 0.13;0.04-0.47/<0.42). Compared to pooled DOACs, Fiix-warfarin consistently had lower point estimates for the RR for efficacy and safety, but only significant for lower death rates (vascular death RR 0.14;0.04-0.49/<0.43). Meta-analysis comparing Fiix-warfarin and DOACs with PT-warfarin consistently found Fiix-warfarin to have the lowest point estimates for efficacy.

CONCLUSION

Monitoring warfarin with Fiix-PT reduces risk of vascular events in NVAF patients as much as DOACs. Warfarin monitored with Fiix-PT is an improved anticoagulant.

During warfarin induction, the Fiix-prothrombin time reflects the anticoagulation level better than the standard prothrombin time

Essentials Fiix-prothrombin time (PT) monitoring of warfarin measuring factor (F) II and X, is effective. Plasma obtained during warfarin induction and stable phase in Fiix-trial was assayed. Fiix-PT stabilized anticoagulation earlier than monitoring with traditional PT-INR. FVII had little effect on thrombin generation that was mainly determined by FII and FX.

SUMMARY

Background The prothrombin time (PT) is equally prolonged by reduction of each of the vitamin K-dependent (VKD) factors (F) II, VII and X. The Fiix-PT is only affected by FII and FX, the main contributors to thrombin generation (TG). Objective To test the hypothesis that variability in warfarin anticoagulation is reduced early during monitoring with the normalized PT-ratio calculated from Fiix-PT (Fiix-International Normalized Ratio [INR]) compared with traditional PT-INR monitoring. Also, that because of its insensitivity to FVII, Fiix-PT more accurately reflects TG when Fiix-INR and PT-INR are discrepant. Methods Samples from Fiix-trial participants monitored with either Fiix-PT or PT were used. VKD coagulation factors and TG were measured in samples from 40 patients during stable anticoagulation and in serial samples obtained from 26 patients during warfarin induction. TG was assessed in relation to selective reduction in single VKD factors. Results During Fiix-warfarin induction full anticoagulation measured as FII or FX activity was achieved at a similar rate to that with PT-warfarin but subsequently stabilized better. Fiix-INR but not PT-INR mirrored total TG during initiation. During induction, FII (R2 = 0.66) and FX (R2 = 0.52) correlated better with TG and with a steeper slope than did FIX (R2 = 0.37) and in particular FVII (R2 = 0.21). In vitro, FII and FX were the main determinants of TG at concentrations observed during VKA anticoagulation, whereas FVII and FIX had little influence. Conclusions Fiix-PT monitoring reduces anticoagulation variability, suggesting that monitoring FVII has a limited role during VKA management. TG is better reflected by Fiix-PT.

A single test to assay warfarin, dabigatran, rivaroxaban, apixaban, unfractionated heparin, and enoxaparin in plasma

Essentials Simple and fast assaying of different anticoagulants (ACs) is useful in emergent situations. We used highly diluted prothrombin time (dPT) or highly diluted Fiix-PT (dFiix-PT) to assay ACs. Both tests could quantify target specific anticoagulants and warfarin anticoagulation. Improved results were consistently observed with the dFiix-PT compared with the dPT.

SUMMARY

Background Assaying anticoagulants is useful in emergency situations or before surgery. Different specific assays are currently needed depending on the anticoagulant. Objectives We hypothesized that levels of warfarin, dabigatran, rivaroxaban, apixaban, and heparins could be measured with use of the diluted prothrombin time (dPT) and diluted Fiix-PT (dFiix-PT), using highly diluted thromboplastin (TP). The latter test is affected only by reduced levels of active factors II and X but corrects test plasma for other deficiencies Methods Increasing TP dilutions were used to identify suitable dilutions to measure dabigatran, rivaroxaban, apixaban, unfractionated heparin (UFH), and enoxaparin. Calibrators containing known amounts of direct oral anticoagulants (DOACs) were used to make standard curves. Citrated plasma samples were obtained from patients taking warfarin or DOACs with known drug concentrations as determined by specific assays. Results The dFiix-PT at a TP dilution of 1:1156 could be used to measure all of the drugs tested at therapeutic concentrations except for fondaparinux. The dPT achieved the same but required two TP dilutions (1:750 and 1:300). The warfarin effect could be assessed by using dFiix-PT at 1:1156 with a PT ratio identical to the international normalized ratio. Six different TPs yielded similar results, but two were less sensitive. Dabigatran, rivaroxaban, and apixaban could be accurately measured in patient samples using both dilute PT assays, but a better correlation was consistently observed between the dFiix-PT and specific assays than with the dPT. Conclusion The dFiix-PT using a single dilution of TP may be suitable to assess the anticoagulant effects of warfarin, dabigatran, rivaroxaban, apixaban, heparin, and enoxaparin.

Effects of fibrinogen concentrate administration during severe hemorrhage

BACKGROUND

Fibrinogen concentrate has been shown to improve coagulation in dilutional coagulopathy in experimental studies, but clinical experience is still scarce. The aim of this study was to evaluate laboratory data and the clinical outcome of fibrinogen administration in patients suffering from severe hemorrhage.

MATERIALS AND METHODS

A retrospective study over a 3-year observation period of consecutive patients who received a single dose of fibrinogen concentrate but not recombinant factor VIIa as part of their treatment of severe hemorrhage, defined as >6 U of packed red blood cells (PRBCs).

RESULTS

Thirty-seven patients were included, most of them suffering from severe hemorrhage following open heart surgery (68%). After a median fibrinogen dose of 2 g (range 1-6 g), an absolute increase in the plasma fibrinogen concentration of 0.6 g/l was observed (P<0.001). The activated partial thromboplastin time (APTT) decreased significantly (P<0.001), from 52 to 43 s and the prothrombin time (PT) decreased from 20 to 17 s, respectively. The transfusion requirement for PRBCs decreased from 6 to 3 U (P<0.01) in the 24 h after fibrinogen administration, but fresh-frozen plasma and platelet concentrate transfusions did not change significantly. Eight patients (22%) died in intensive care unit and the pre-operative fibrinogen concentration was not significantly different in these patients.

CONCLUSION

Administration of fibrinogen for severe hemorrhage was associated with an increased fibrinogen concentration and a significant decrease in APTT, PT and the requirement for PRBCs.

Risk of excessive bleeding associated with marginally low von Willebrand factor and mild platelet dysfunction

BACKGROUND

Bleeding symptoms are so commonly reported that it is not known whether they associate causally or coincidentally with mild but measurable primary hemostatic defects. OBJECTIVES/PATIENTS/METHODS: In order to evaluate if the mild primary hemostatic defects are truly causative of increased bleeding symptoms, we surveyed a population of healthy teenagers for bleeding symptoms. Using a case-control approach, we then estimated the risk of excessive bleeding associated with low von Willebrand factor (defined as VWF below the 5th percentile of a normal reference population), and with mild platelet dysfunction [PD, defined as concurrent reduced platelet aggregation responses to two agonists (adenosine diphosphate and epinephrine)].

RESULTS

Excessive bleeding was present in 63 out of 809 teenagers (7.8%). Among the 49 cases who were tested for VWF, low values by three measures were more commonly present than in 166 controls, specifically, ristocetin cofactor (RCo) activity [20.4% vs. 5.4%, odds ratio (OR) 4.5], collagen binding (14.3% vs. 4.2%, OR 3.8), and antigen level (20.4% vs. 6.0%, OR 4.0). The low RCo values ranged from 35 to 45 U dL(-1) except for a single case with 26 U dL(-1). Of the 47 teenagers with excessive bleeding who underwent platelet aggregation studies, reduced responses were more common than in controls (12.8% vs. 4.4%, OR 3.2). Twenty-nine per cent of cases with excessive bleeding had either low RCo or PD.

CONCLUSION

Almost one in three teenagers who report excessive bleeding is likely to have a measurable hemostatic disturbance manifested either by marginally low VWF (by three measures) or by mild PD.

The contraceptive vaginal ring (NuvaRing®) and hemostasis: a comparative study

This open-label, nonrandomized study compared changes in hemostatic variables during NuvaRing and oral levonorgestrel 150 microg/ethinylestradiol 30 microg (LNG/EE) use for six cycles. Eighty-seven women started the study, 44 with NuvaRing and 43 with the LNG/EE oral contraceptive. For most procoagulation variables, there was no difference between NuvaRing and oral LNG/EE; only Factor VII levels increased in the NuvaRing group and decreased in the LNG/EE group. The majority of assessed variables show that anticoagulation and fibrinolytic activity was comparable between the NuvaRing and oral LNG/EE groups. Antithrombin activity and protein C activity both tended to be higher with NuvaRing. Levels of tissue plasminogen activator decreased in both groups but the reduction was smaller with NuvaRing. There were no significant differences in fibrin turnover between the treatment groups. The data show that both NuvaRing and oral LNG/EE are associated with a minimal effect on hemostatic variables.

Activated and total coagulation factor VII, and fibrinogen in coronary artery disease

Fibrinogen (FBG) and total coagulation factor VII (FVIIc) concentrations are higher in those patients with coronary artery disease who are at increased future risk of acute ischemic events. The relationship between activated factor VII (FVIIa) and cardiovascular events, however, has not been intensively studied. Data were collected from 401 consecutive patients who underwent coronary angiography because of suspected coronary artery disease. Conventional risk factors FVIIc, FVIIa and FBG were assessed in relation to the severity of coronary artery disease, left ventricular ejection fraction, and previous clinical events. A strong positive correlation was found between FVIIa and FVIIc (p < 0.001), but neither FVIIa nor FVIIc correlated with FBG. No correlation was found between FVIIa, FVIIc or FBG levels and stenosis score for the severity of coronary artery disease, and all were similar in patients with stable or unstable angina pectoris. Multivariate regression analysis showed FVIIc to be higher in women (p = 0.004), and positively related to triglycerides (p = 0.001) and HDL cholesterol (p = 0.006), but not to a previous myocardial infarction or total cholesterol. FVIIa, on the other hand, was lower in patients with a previous myocardial infarction (p = 0.004), higher in women (p = 0.001) and those that previously had undergone percutaneous transluminal coronary angioplasty (p = 0.039), and positively related to total cholesterol (p = 0.011), duration of coronary artery disease (p = 0.032), and smoking (p = 0.008). FBG was positively associated with a previous myocardial infarction (p = 0.013), hypertension (p = 0.016), smoking (p = 0.005), and the thrombocyte count (p < 0.001). Finally, stepwise logistic regression analysis verified a previous myocardial infarction to be negatively associated with FVIIa (p = 0.03), and positively with FBG (p = 0.03), total cholesterol (p = 0.02), and the severity of coronary artery disease (p < 0.001). In conclusion, in patients suspected of coronary artery disease undergoing cardiac catheterization, FVIIa was decreased and FBG increased in those who had a previous myocardial infarction. FVIIa, FVIIc, or FBG levels were not, however, related to the severity of coronary artery disease, and they were similar in patients with stable or unstable angina pectoris.

[A prospective study of oral anticoagulation therapy monitored with the P&P-test.]

OBJECTIVE

To analyze the outcome of patients on oral anticoagulation therapy who are monitored with the prothrombin proconvertin time (P&P-test, PP).

MATERIAL AND METHODS

The prothrombin-proconvertin time was used to adjust anticoagulant intensity in a prospective study of 326 patients treated with oral anticoagulants for a study period of 121 patient years. The goal intensity INR was 2.0-3.0 for all patients. The main indications were: artificial heart valves 26%, venousthromboembolism 25%, atrial fibrillation 23%, atherosclerotic disease 14% and systemic arterial embolism of uncertain etiology 7%.

RESULTS

INR calculated directly from the PP correlated well with INR calculated from the PT. The mean time adjusted anticoagulant intensity was 2.3 and did not differ significantly according to indication. Six major bleedings, including one fatal, occurred in five patients during the study period. The INR was 1.8 in one patient who bled from a duodenal ulcer, but 6.8,7.9,8.6,11.6 (died) and 15.5 at five other events. The INR was <4.5 during 97% of the treatment time of the whole group and 1% of treat notment time were at an INR>6.0. The bleeders had a different pattern with 18% of the treatment time at INR>6.0. The risk of bleeding was one for every 73 days at that intensity or an almost 600 fold risk increase compared to an INR<4.5. One patient anticoagulated for systemic embolism had cerebral infarction with an event related INR of 2.0. Two patients with atrial fibrillation died from acute myocardial infarction but event related INR's were not available. One patient anticoagulated for venous thromboembolism died suddenly but was not autopsied. No embolic events occurred in patients with artificial heart valves in spite of the low intensity anticoagulation.

CONCLUSION

Despite a relatively low intensity in all patient groups in this study thromboembolic events were rare. The risk of bleeding increased markedly at INR>6.0. The mortality rate of the ariticoagulated population was comparable to the expected age adjusted Icelandic mortality rate.

[Factor VQ50f) and prothrombin 20210 A mutations in an Icelandic apparently healthy population and patients suffering from venous thrombosis.]

INTRODUCTION

Inherited and aquired factors are important in the pathogenesis of thrombosis. Recent studies have demonstrated that mutations in the genes encoding coagulation factor V (FVQ506 or FVLeiden) and prothrombin (PT 20210 A) predispose to a markedly increased risk of venous thrombosis. FVQ506 is considered to be the most frequent cause of inherited venous thrombosis in Europeans and the allele frequency has been shown to be high. The aim of this study was to determine the allele frequency of the two mutations in an apparently healthy Icelandic population and patients suffering from venous thrombosis.

MATERIAL AND METHODS

An apparently healthy Icelandic population and patients suffering from venous thrombosis were genotyped for the presence or absence of the FVQ506 and PT 20210 A mutations using PCR and restrictions fragment length polymorphisms.

RESULTS

The allele frequency of FVQ506 was 0.0315 in the healthy population (n=159; 10 heterozygotes found). Fifteen of 99 patients with venous thrombosis were found to be heterozygous for FVQ506 (15.2%; allele frequency 0.071), significantly more when compared to controls (p<0.01). One apparently healthy individual (0.9%; n=108) and one of the patients (0.95%; n=99) were found to be heterozygous for PT 20210 A.

CONCLUSION

The results demonstrate high prevalence of FVQ506 in the Icelandic population compared with many other European populations and that FVQ506 is commonly associated with venous thrombosis.

Performance of prothrombin-proconvertin time as a monitoring test of oral anticoagulation therapy

Outcome and anticoagulation intensity was evaluated during 121 patient years of oral anticoagulant therapy monitored with the prothrombin-proconvertin clotting time (PP, also known as P&P). The PP-based international normalized ratio (INR; PP-INR) correlated well with the INR calculated from the prothrombin clotting time (PT; r = 0.92), and results were almost identical over a wide range after linear conversion (1/INR). When the PP-INR was 4.5 or less, the risk of major bleeding was 1 for every 118 treatment years, but it was 1 for every 73 days when the INR was 6 or more. The 1/PP-INR correlated better with factor II coagulant activity (r = 0.85) than did the 1/PT-INR (r = 0.78). The 1/PP-INR also correlated better with the native prothrombin antigen (r = 0.76) than did the 1/PT-INR (r = 0.68). The PP and PT results correlated better with factor II coagulant activity than with native prothrombin antigen. Thus, the PP clotting time results can be accurately converted to INR. The results also suggest that the PP may have advantages over the PT as an indicator of anticoagulation intensity during oral anticoagulation.

[Quality management by physicians in Iceland.]

The Icelandic Medical Association appointed a committee in 1993 with the task of recommending how to introduce the concept of Total Quality Management into the Icelandic healthcare system. The first task was to conduct a mail survey of the current status of quality assurance. Heads of departments at the five major hospitals in Iceland were contacted as well as the chairmen of all the specialist societies. The response rate was only 37%, but compensated by two ameliorating facts; responses were obtained from most of the major departments, and there was a considerable overlap between hospital departments and specialty societies as well as between subspecialty societies. The results indicate that quality assurance is an ingrained part of Icelandic hospitals, mostly in the form of standards and retrospective audits, not prospective actions. Methods used are further detailed. Outside hospitals, the Icelandic Society of Family Physicians stands out amongst the specialty societies represented, by having organized and carried out several projects in quality assurance. It is recommended that more emphasis shall be put on prospective methods, the setting of practice guidelines, outcome studies and research in quality assurance. The lack of quality assurance in specialty practice outside hospitals needs to be addressed with vigour.

[New developments in anticoagulation with heparin; a short review.]

Low molecular-weight heparins (LMWH) are derivatives of standard unfractionated heparin (UFH) and both types of heparins are used for anticoagulation. UFH is heterogeneous with respect to molecular size and exerts its effect through enhancement of antithrombin III inhibition of serine proteases. Full dose UFH has a narrow therapeutic window as well as a short half-life and this mandates constant monitoring of its anticoagulatory effect. Weight-based dosing guidelines for unfractionated heparin have been shown to be safe and improve results. New modified heparins have lower molecular weight (LMWH) than UFH. The LMWH are dosed according to body weight without a need for monitoring tests and subcutaneous administration no more than twice daily is adequate. In studies comparing LMWH to UFH, the LMWH seem to be at least as effective as unfractionated heparin in preventing or treating venous thromboembolism. To date the comparison in these studies has been between LMWH and UFH dosed in the traditional way but a comparison of LMWH with UFH dosed by weight-based guidelines has not been studied yet.

[Surgical thromboprophylaxis]

Deep vein thrombosis (DVT) and pulmonary embolism (PE) are common and serious post-operative complications. The risk depends on age, general condition, length of operation and type of surgery. Properly used prophylactic therapy with unfractionated heparin, low molecular weight heparin or two-step warfarin can reduce post-operative deaths from PE by 70% and reduce DVT by 50-80% without increasing the risk of serious postoperative bleeding. This review article summarizes the outcome of multiple controlled trials of surgical thromboprophylaxis with various medications.

Plasminogen depletion during streptokinase treatment or two-chain urokinase incubation correlates with decreased clot lysability ex vivo and in vitro

The relationship between lytic state variables and ex vivo clot lysability was investigated in blood drawn from patients during streptokinase administration for acute myocardial infarction. A lytic state was already evident after 5 min of treatment and after 20 min the plasminogen concentration had decreased to 24%, antiplasmin to 7% and fibrinogen 0.2 g/l. Lysis of radiolabeled retracted clots in the patient plasmas decreased from 37 +/- 8% after 5 min to 21 +/- 8% at 10 min and was significantly lower (8 +/- 9%, p < 0.005) in samples drawn at 20, 40 and 80 min. Clot lysability correlated positively with the plasminogen concentration (r = 0.78, p = 0.003), but not with plasmin activity. Suspension of radiolabeled clots in normal plasma pre-exposed to 250 U/ml two-chain urokinase for varying time to induce an in vitro lytic state was also associated with decreasing clot lysability in direct proportion with the duration of prior plasma exposure to urokinase. The decreased lysability correlated with the time-dependent reduction in plasminogen concentration (r = 0.88, p < 0.0005). Thus, clot lysability decreases in conjunction with the development of the lytic state and the associated plasminogen depletion. The lytic state may therefore limit reperfusion during thrombolytic treatment.

Prolonged total extracorporeal lung assistance without systemic heparinization

A 16-year-old female developed severe ARDS in her single remaining lung following pneumonectomy for blunt trauma. Total extracorporeal lung assist (ECLA) for 40 days using a covalently heparin-coated circuit proved lifesaving. Systemic heparinization was not applied, as the heparinized surface by itself prevented clotting of the extracorporeal circuit. Systemic primary fibrinolysis developed but was not associated with major bleeding. A veno-right ventricular cannulation technique was used and maximum venous drainage for the extracorporeal circulation was achieved by elevating the bed 50 cm from the floor. This allowed extracorporeal blood flow (ECBF) approaching cardiac output (CO) and complete extracorporeal replacement of lung function. After 40 days, lung recovery allowed discontinuation of ECLA. Five days later the patient suffered serious lung collapse and was operated for a bronchopleural fistula. The patient was extubated 4 weeks after terminating ECLA and discharged in good condition 5 weeks later.

Enhancement of fibrinolysis in vitro by ultrasound

The effect of ultrasound on the rate of fibrinolysis has been investigated using an in vitro system. Plasma or blood clots containing a trace label of 125I fibrin were suspended in plasma containing plasminogen activator and intermittently exposed to continuous wave 1-MHz ultrasound at intensities up to 8 W/cm2. Plasma clot lysis at 1 h with 1 microgram/ml recombinant tissue plasminogen activator (rt-PA) was 12.8 +/- 1.2% without ultrasound and was significantly (P = 0.0001) increased by exposure to ultrasound with greater lysis at 1 W/cm2 (18.0 +/- 1.4%), 2 W/cm2 (19.3 +/- 0.7%), 4 W/cm2 (22.8 +/- 1.8%), and 8 W/cm2 (58.7 +/- 7.1%). Significant increases in lysis were also seen with urokinase at ultrasound intensities of 2 W/cm2 and above. Exposure of clots to ultrasound in the absence of plasminogen activator did not increase lysis. Ultrasound exposure resulted in a marked reduction in the rt-PA concentration required to achieve an equivalent degree of lysis to that seen without ultrasound. For example, 15% lysis occurred in 1 h at 1 microgram/ml rt-PA without ultrasound or with 0.2 microgram/ml with ultrasound, a five-fold reduction in concentration. Ultrasound at 1 W/cm2 and above also potentiated lysis of retracted whole blood clots mediated by rt-PA or urokinase. The maximum temperature increase of plasma clots exposed to 4 W/cm2 ultrasound was only 1.7 degrees C, which could not explain the enhancement of fibrinolysis. Ultrasound exposure did not cause mechanical fragmentation of the clot into sedimentable fragments, nor did it alter the sizes of plasmic derivatives as demonstrated by SDS polyacrylamide gel electrophoresis. We conclude that ultrasound at 1 MHz potentiates enzymatic fibrinolysis by a nonthermal mechanism at energies that can potentially be applied and tolerated in vivo to accelerate therapeutic fibrinolysis.

Depletion of plasminogen in vitro or during thrombolytic therapy limits fibrinolytic potential

Thrombolytic therapy frequently induces a "lytic state" associated with a decrease in plasma plasminogen concentration that could limit therapeutic efficacy. We therefore investigated the influence of soluble plasminogen concentration on in vitro lysis of retracted whole-blood clots in plasma from normal subjects and from patients undergoing thrombolytic therapy. With recombinant tissue plasminogen activator (1000 ng/ml) or two-chain urokinase plasminogen activator (250 U/ml), minimal clot lysis occurred in normal plasma depleted of plasminogen by lysine Sepharose chromatography. Clot lysis induced by two-chain urokinase plasminogen activator increased progressively in normal plasma at initial plasminogen concentrations between 0.06 to 6 U/ml, whereas maximum lysis with recombinant tissue plasminogen activator occurred between 0.5 U/ml and 1 U/ml and was less at lower and higher concentrations of plasminogen. Incubation of whole-blood clots in normal plasma with recombinant tissue plasminogen activator resulted in little change in plasminogen concentration during 6 hours, with a constant rate of clot lysis. Incubation with two-chain urokinase plasminogen activator, however, caused a rapid decrease in plasminogen concentration and a corresponding decrease in lysis rate; lysis rate was restored after repletion with purified plasminogen. The effect of in vivo activator-induced plasminogen depletion on in vitro clot lysis rates was tested with plasma obtained from patients 90 to 120 minutes after they had received 30 mg of acylated plasminogen-streptokinase activator complex that showed depletion of plasminogen to 14% +/- 2%. These plasma samples produced only 4% +/- 1% in vitro clot lysis during 4 hours but lysis increased progressively after repletion with 1, 2, and 4 U/ml plasminogen.(ABSTRACT TRUNCATED AT 250 WORDS)

Response to plasma exchange and splenectomy in thrombotic thrombocytopenic purpura. A 10-year experience at a single institution

BACKGROUND

This study was designed to assess the response of patients with thrombotic thrombocytopenic purpura to plasma exchange and to evaluate the role of splenectomy after relapse.

METHODS

The records of all patients with thrombotic thrombocytopenic purpura who had plasma exchange as primary treatment at a single center during a 10-year period were retrospectively reviewed. Response to the initial course of plasma exchange was determined, and the clinical outcome was evaluated in patients whose conditions were either refractory to exchange, responded without relapse, or relapsed after initial response. The outcome of patients treated during relapse with splenectomy was evaluated. A literature review was conducted to determine the clinical outcome in patients treated similarly.

RESULTS

Twenty-seven patients for whom data could be evaluated had been treated in the 10-year period. Twenty-one (78%) responded to the plasma exchange, but the conditions of six (22%) were refractory and these patients died. Eight patients (30%) had one or multiple relapses after initial response but had prolonged remissions after additional plasma exchange alone (two patients) or splenectomy (six patients). A review of 19 reports, including 224 patients with thrombotic thrombocytopenic purpura initially treated with plasma exchange, revealed similar findings, with initial response in 81%, refractoriness in 19%, and relapse after initial response in 27% of patients.

CONCLUSION

Response to plasma exchange in thrombotic thrombocytopenic purpura is associated with an excellent prognosis, and most deaths occur in patients whose conditions are refractory. Relapses after initial response are frequent but can be managed successfully with additional plasma exchange or with splenectomy, which often induces long-term remissions.

Chronic atrial fibrillation--epidemiologic features and 14 year follow-up: a case control study

In a randomly selected population of 9067 individuals, 32-64 years of age in 1967-1970, 25 (0.28%) had chronic atrial fibrillation (CAF). Eight had lone atrial fibrillation. In 1984 the cases were compared with an age- and sex-matched control group of 50 and found to have more cerebrovascular accidents (6 versus 2; P less than 0.05), congestive heart failure (9 versus 1; P less than 0.001), and valvular rheumatic heart disease (3 versus 0) or history consistent with rheumatic fever (6 versus 0; P less than 0.01). The mortality in the CAF group was 60% higher due to an excess in cardiovascular (relative risk 6.1; P less than 0.05) and cerebrovascular (relative risk 12.2; P less than 0.05) causes. The prevalence or incidence of ischaemic or hypertensive heart disease or the presence of coronary risk factors did not significantly differ in the two groups. By M-mode echocardiography the left atrial size, left ventricular enddiastolic dimension and left ventricular mass were increased in the CAF patients, while the systolic left ventricular shortening was significantly less. Thus, the prevalence of CAF is low in a randomly selected population 32-64 years of age and CAF is not strongly associated with ischaemic heart disease or hypertension. The CAF patients have an increased risk of dying prematurely particularly from cerebrovascular causes, even in the absence of valve disease.

Acute thoracic inlet obstruction in achalasia with adenoid cystic and squamous cell carcinoma

Respiratory symptoms due to compression of the trachea by the dilated esophagus in achalasia are extremely rare. A patient is presented whose respiratory manifestations included engorged neck veins and a neck swelling that fluctuated with respiration. He also had two malignant tumors in his dilated esophagus, a squamous cell carcinoma and an adenoid cystic carcinoma.