Effect of supervised high-intensity interval training on haemostasis in patients with coronary artery disease: a randomised controlled trial

Background

Regular exercise training is recommended for patients with stable coronary artery disease (CAD), because it improves quality of life and reduces cardiovascular mortality and hospital admissions. CAD patients benefit from anti-thrombotic therapy and may have a pro-coagulant condition compared to healthy individuals. Long-term exercise training may reduce platelet aggregation and coagulation and increase fibrinolysis.

Purpose

We aimed to investigate if supervised high-intensity interval training affects haemostasis in patients with stable CAD.

Methods

We randomised stable CAD patients to supervised high-intensity interval training or standard care. High-intensity exercise training was performed on rowing ergometers three times weekly for 12 weeks. Blood samples were obtained in all patients prior to randomisation (baseline) and after 6 and 12 weeks. We evaluated platelet aggregation with the Multiplate® Analyzer, thrombin generation using the Calibrated Automated Thrombogram and fibrinolysis employing an in-house clot lysis assay. Between group differences were evaluated with mixed model analysis using SPSS. According to our sample size calculation, we have a statistical power of 88% to detect a difference of 25% in clot lysis time.

Results

A total of 142 patients with stable CAD (mean age 67±9 years, 83% males) completed the study; 64 in the exercise group and 78 in the control group. The weekly average active training duration was 54 min, and adherence to training was 97%. When comparing the two groups (exercise vs. standard care) from baseline to post intervention, we found no significant changes in ADP-induced platelet aggregation (difference between baseline and 12 weeks (Δ) 11 AU·min, 95% confidence interval (CI): −46–68 in the exercise group and Δ24 AU·min, 95% CI: −28–77 in the standard care group, p=0.52), thrombin generation (endogenous thrombin potential Δ45 nM·min, 95% CI: −77–166 in the exercise group and Δ103 nM·min, 95% CI: −7–212 in the standard care group, p=0.18) or fibrinolysis (50% clot lysis time Δ62 sec, 95% CI: −136–261 in the exercise group and Δ215 sec, 95% CI: 38–391 in the standard care group, p=0.39).

Conclusion

High-intensity interval training did not have major effects on platelet aggregation, thrombin generation nor fibrinolysis in patients with stable CAD.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Aarhus UniversityThe Faroese Health Research Foundation (Sjúkrakassagrunnurin)

P–706 Impaired fibrinolysis during estrogen substitution in relation to frozen-thawed embryo transfer

Study question

Is the clot lysis time prolonged in women undergoing estrogen substitution in artificial cycle during frozen-thawed embryo transfer (AC-FET)?

Summary answer

Women receiving AC-FET have a prolonged clot lysis time that could result in increased venous thromboembolic risk during estrogen substitution.

What is known already

High doses of estrogen are used for women treated with AC-FET; this in contrast to women treated with natural cycle frozen-thawed embryo transfer (NC-FET). Based on previous research on hormone replacement therapy in other settings, estrogen substitution is probably associated with an increased risk of thromboembolism. Moreover, it has formerly been shown that pregnant women followed assisted reproductive technology (ART) treatment as compared to natural fertilization, has an increased risk of thrombosis. However, changes in fibrinolysis has never been examined in women undergoing estrogen substitution during treatment with AC-FET.

Study design, size, duration

Prospective cohort study of women receiving AC-FET with oestrogen/progesterone substitution or NC-FET. Blood samples were obtained four times: 1) prior to hormone substitution (baseline), 2) confirmation of biochemical pregnancy, 3) gestational week 8 and 4) gestational week 13 (5 weeks after cessation of hormone substitution). Inclusion criteria: women aged > 18 years assigned for FET. Exclusion criteria: egg donor recipients, known bleeding disorders, indication for thromboprophylaxis and treatment with anti-platelet medication or non-steroid-anti-inflammatory drugs.

Participants/materials, setting, methods

We included women at the Department of Obstetrics and Gynaecology, Horsens Fertility Clinic, Denmark, from August 2019 – November 2020. In total, 34 participants were included: 19 women treated with AC-FET and 15 women receiving NC-FET. We examined fibrinolysis measured by a dynamic fibrin clot lysis assay that can assess the capacity for fibrin formation and fibrinolysis. This detailed information of the fibrinolytic activity are used as a surrogat marker of thromboembolic risk.

Main results and the role of chance

Our results showed a significantly longer lysis time (908 ± 234 vs 1157 ± 218) (p < 0.001) within the AC-FET group after hormone substitution compared to baseline. Moreover, we found a higher area under the curve (AUC) (919 ± 305 vs 1167 ± 391) (p = 0.006) within the AC-FET group. However, we observed no changes in mean lag phase or maximum absorbency after estrogen substitution within the AC-FET group. Since we observed a significantly higher AUC within the AC-FET group after estrogen substitution, this is probably due to the prolonged lysis time, indicating hypofibrinolysis. No significant changes was found comparing the NC-FET group with the AC-FET group.

Limitations, reasons for caution

Our data are based on a small study population. Additionally, we cannot exclude that the coagulation parameters could be affected by estrogen prior to study enrollment as we had no wash out period.

Wider implications of the findings: Our findings indicate prothrombotic changes in the AC-FET group. It is relevant to individually consider the indication for AC-FET and restrict the use of unnecessary hormone exposure. These data should be followed by a populations-based study to clarify how this potentially increased venous thromboembolic risk will manifest itself clinically.

Trial registration number

NCT04359576

256Heart transplant recipients with cardiac allograft vasculopathy have increased platelet aggregation before and after low-dose aspirin therapy

Background

Following heart transplantation (HTx), long-term survival is reduced mainly due to development of a specific form of coronary artery disease, coronary allograft vasculopathy (CAV). Using optical coherence tomography to visualize the coronary artery wall, we have recently shown that layered fibrotic plaques resembling organized clots are the dominant plaque component in CAV. Thus, thrombosis is suggested as a possible mechanism contributing to development and progression of CAV. Aspirin is widely used after HTx despite limited evidence and lack of specific guidelines. The antiplatelet effect of aspirin has not been thoroughly examined in HTx-patients.

Purpose

To investigate baseline platelet aggregation and the antiplatelet effect of aspirin in HTx-patients with and without CAV.

Methods

We included 68 HTx-patients (median 8.6 years from HTx). In 66 patients taking 75 mg aspirin for a minimum of 7 days, platelet aggregation was measured in whole blood using impedance aggregometry with the following agonists: Adenosine diphosphate (ADP) stimulating ADP-receptors and arachidonic acid (AA) for monitoring of aspirin treatment. Aspirin compliance was confirmed by measuring serum-thromboxane B2. Platelet aggregation prior to aspirin therapy was measured in 59 patients as it was not considered clinically safe to interrupt ongoing aspirin treatment for one week prior to blood sampling in 9 patients mainly due to previous coronary stenting. CAV burden was determined by coronary angiography and echocardiography based on international classification. Patients were divided into two groups; no CAV (n=37) and CAV (n=29).

Results

In HTx-patients not treated with aspirin, we found significantly increased ADP-induced platelet aggregation in patients with CAV vs. patients without CAV (904 (95% CI 813–995) vs. 786 (95% CI 728–843) AU*min, P=0.02). Baseline AA-induced aggregation was also higher in patients with CAV vs. patients without CAV, though non-significant (994 (95% CI 907–1081) vs. 905 (95% CI 839–972) AU*min, P=0.10). Even though aspirin reduced AA-induced platelet aggregation in both groups, patients with CAV had significantly increased AA-induced platelet aggregation compared with patients without CAV on aspirin treatment (380 (95% CI 295–465) vs. 286 (95% CI 239–334) AU*min, P=0.04) (Fig. 1).

Conclusions

HTx-patients with CAV have increased platelet aggregation before and after aspirin treatment compared with HTx-patients without CAV. Aspirin monotherapy may not provide sufficient platelet inhibition in HTx-patients with CAV.

Acknowledgement/Funding

Aarhus University (PhD-salary)

Differential vascular effects of aspirin in people with Type 2 diabetes without cardiovascular disease and matched controls without diabetes

AIM

We investigated whether the effect of low-dose aspirin on endothelium-dependent vasodilation and arterial stiffness in people with Type 2 diabetes is different from a matched control group. We examined acute and chronic effects, and effects over the 24h dosing interval.

METHODS

In an open-label parallel group intervention study, we included 21 participants with Type 2 diabetes and 21 age- and sex-matched controls. Endothelium-dependent vasodilation was assessed as the reactive hyperaemia index (lnRHI) measured by peripheral arterial tonometry (EndoPAT^® ). Arterial stiffness was assessed as pulse wave velocity (PWV) measured by applanation tonometry (SphygmoCor^® ). Measurements were performed prior to aspirin intake and 1h after aspirin administration (75 mg). Participants were then treated for 6 days, and measurements were repeated at 24 h and 1 h after aspirin intake.

RESULTS

Baseline lnRHI did not differ between groups. The controls had an immediate increase in lnRHI after the first aspirin tablet. This was not observed in participants with diabetes (difference between groups; P < 0.05). After 1 week, both groups demonstrated increased lnRHI compared with baseline (P < 0.01). In participants with diabetes, lnRHI was significantly lower 24 h after aspirin administration compared with 1 h after administration (P < 0.05). This difference was not observed in controls (P = 0.84, difference between groups; P = 0.12). The effect on PWV did not differ between groups.

CONCLUSION

Aspirin had a reduced immediate effect on endothelium-dependent vasodilation in participants with diabetes. Both groups had improved endothelial function after 1 week of treatment. Further, the effect of aspirin on endothelial function may be declining during a 24 h dosing interval in people with Type 2 diabetes. (Clinical Trial Registry No: 2016-000515-32).

The complement lectin pathway after cardiac arrest

The lectin pathway (LP) of the complement system may initiate inflammatory reactions when body tissue is altered. We aimed to investigate the levels of the LP proteins in out-of-hospital cardiac arrest patients, and to compare these with healthy individuals. Furthermore, we aimed to clarify whether the duration of targeted temperature management influenced LP protein levels, and we further examined whether LP proteins were associated with 30-day mortality. We included 82 patients resuscitated from out-of-hospital cardiac arrest. The patients were randomly assigned to 24 or 48 hours of targeted temperature management at 33 ± 1°C. Blood samples were obtained 22, 46 and 70 hours after target temperature was reached. Levels of the LP proteins (mannan-binding lectin [MBL], M-ficolin, H-ficolin, collectin liver 1 [CL-L1], MBL-associated serine protease 1 [MASP-1], MASP-2, MASP-3 and MBL-associated protein of 44 kDa [MAp44]) were measured using time-resolved immunofluorometric assays. Data from 82 gender matched healthy individuals were used for comparison. Levels of CL-L1, MASP-1, MASP-2 and MAp44 were significantly higher, whereas M-ficolin levels were significantly lower in cardiac arrest patients compared with healthy individuals. MASP-2, MASP-3 and M-ficolin levels changed significantly when comparing 24 and 48 hours of targeted temperature management. The LP protein levels were not different between 30-day survivors and non-survivors after cardiac arrest. The differences in LP protein levels between patients and healthy individuals may indicate that cardiac arrest patients have an activated LP. Overall, the LP protein levels were not influenced by the duration of targeted temperature management, and the levels were not associated with 30-day mortality.

Measurement of platelet aggregation, independently of patient platelet count: a flow-cytometric approach

Essentials Platelet function may influence bleeding risk in thrombocytopenia, but useful tests are needed. A flow cytometric platelet aggregation test independent of the patient platelet count was made. Platelet aggregation was reduced in thrombocytopenic patients with hematological cancer. High platelet aggregation ruled out bleeding tendency in thrombocytopenic patients.

SUMMARY

Background Methods for testing platelet aggregation in thrombocytopenia are lacking. Objective To establish a flow-cytometric test of in vitro platelet aggregation independently of the patient's platelet count, and examine the association of aggregation with a bleeding history in thrombocytopenic patients. Patients/methods We established a flow-cytometric assay of platelet aggregation, and measured samples from healthy individuals preincubated with antiplatelet drugs, and samples from two patients with inherited platelet disorders. Then, we included 19 healthy individuals and 20 patients with platelet counts of ≤ 50 × 109 L-1 , diagnosed with acute myeloid leukemia or myelodysplastic syndrome. We measured platelet aggregation and platelet activation by platelet surface expression of activated glycoprotein IIb-IIIa, P-selectin and CD63 after addition of agonists: collagen-related peptide, thrombin receptor-activating peptide (TRAP), and ADP. Results The platelet aggregation assay showed a low intraserial coefficient of variation of ≤ 3%. Similar results were obtained for platelet-rich plasma and isolated platelets at platelet counts of > 10 × 109 L-1 ; otherwise, platelet isolation was required. The platelet aggregation percentage decreased with increasing antiplatelet drug concentration. Platelet aggregation in patients was reduced as compared with healthy individuals: 42% (interquartile range [IQR] 27-58) versus 66% (IQR 60-67) for TRAP; 41% (IQR 25-48) versus 70% (IQR 69-72) for collagen-related peptide; and 44% (IQR 30-53) versus 65% (IQR 46-72) for ADP. Platelet activation after stimulation was reduced in patients and correlated with platelet aggregation (e.g. r = 0.78-0.81 when stimulated with collagen-related peptide). Platelet aggregation had a negative predictive value of 100% for a bleeding tendency among patients. Conclusion The established platelet aggregation assay was applicable for thrombocytopenic patients, and improved the identification of bleeding risk.

PO-20 - Crosstalk between the lectin pathway and haemostasis in patients with pulmonary cancer

INTRODUCTION

Recent research has focused on the complement system in cancer, including the lectin pathway of complement activation. Mannose-binding lectin (MBL), a key activator of the lectin pathway, can bind to tumor cell surfaces in vitro, and lectin pathway activation is increased in several types of cancer. The exact role of the complement system in cancer is currently discussed. However, one possible consequence of the increased complement activation could be contribution to the increased thrombosis risk which cancer patients experience. Proteins of the lectin pathway can activate coagulation and impair fibrinolysis in vitro, but the significance of this in a clinical setting is not well understood.

AIM

We aim to investigate associations between lectin pathway and haemostatic activation in patients with lung cancer undergoing thoracoscopic surgery.

MATERIALS AND METHODS

Patients with lung cancer (n=60) eligible for thoracoscopic tumor resection were included as part of a randomized controlled trial, the COPPVATS project (EudraCT no: 2012-002409-23), conducted at the Department of Thoracic Surgery, Aarhus University Hospital. Exclusion criteria were arterial or venous thrombosis within the last three months, other systemic disease than cancer, and anticoagulant treatment prior to inclusion. Blood samples were obtained the day before surgery, perioperatively, and on the 1st and 2nd postoperative days. Laboratory analyses on the complement system include MBL, MBL-associated protease (MASP)-1 and -2, MBL-MASP complex, ficolin-1, -2, and -3 and complement factor C3b. Haemostasis was evaluated with routine coagulation parameters (INR, APTT, fibrinogen, fibrin d-dimer), platelet function, and tissue factor-induced thrombin generation.

RESULTS

Recruitment of the study subjects is concluded, and laboratory work is in progress. The complement analyses and data processing will be performed during early spring 2016, so that results will be ready for presentation on the conference.

CONCLUSIONS

The present project will provide new knowledge on lectin pathway activation and the pathogenesis of thrombosis in cancer patients. In the long term, this will help improve the individual risk assessment and lead to new studies on thromboprophylaxis and treatment in conditions with increased complement activation.

PO-62 - Remote ischemic preconditioning in head and neck cancer reconstruction - a randomized controlled trial

INTRODUCTION

In reconstructive head and neck cancer surgery, tissue flaps are transferred to the surgical defect and revascularized by anastomosis of small vessels. Cancer patients are in a hypercoagulable state with high risk of peri- and postoperative thrombotic events. Thrombosis to the tissue flap anastomoses or microcirculation is the main reason for total flap necrosis with potential fatal consequences for the patient. Remote ischemic preconditioning (RIPC), where brief cycles of upper extremity ischemia are induced with an inflatable tourniquet, triggers a global protection of tissues subjected to ischemia-reperfusion injury. RIPC has also been shown to impact the coagulation system.

AIM

The aim of the trial is to investigate, if RIPC attenuates platelet aggregation during reconstructive head and neck cancer surgery.

MATERIALS AND METHODS

Sixty patients with head and neck cancer will be included in the trial. The subjects will be randomized to RIPC or sham during surgery. RIPC is administered by four 5-minute cycles of upper extremity ischemia, each separated by five minutes of reperfusion. Blood samples will be drawn preoperatively, before RIPC/sham, 3 hours after RIPC/ sham, 6 hours after RIPC/sham, and on the first postoperative day. Platelet aggregation will be measured with the Multiplate® analyzer using collagen, ADP and TRAP as agonists. Furthermore, platelet count, mean platelet volume, immature platelet fraction, and von Willebrand factor antigen are determined.

RESULTS

The trial is ongoing. Preliminary results will be presented at ICTHIC 2016.

CONCLUSIONS

If RIPC proves to attenuate platelet aggregation, it could become a novel antithrombotic treatment in oncologic reconstructive surgery. Hence, morbidity and mortality related to surgery is reduced, and adjuvant oncologic therapy can be initiated in timely fashion.

Preconception venous thromboembolism and placenta-mediated pregnancy complications

BACKGROUND

Placenta-mediated complications are leading causes of maternal and fetal morbidity and mortality. We hypothesized that a preconception history of venous thromboembolism (VTE) is associated with increased risk of placenta-mediated pregnancy complications.

METHODS

A nationwide population-based cohort study of all singleton pregnancies leading to delivery from 1997 to 2012 (n = 964 967). We obtained data on placenta-mediated pregnancy complications from the Danish Medical Birth Registry and data on VTE before pregnancy from the Danish National Patient Registry. We computed absolute risks, crude and adjusted risk differences (RDs) using a binomial regression model, and crude and adjusted risk ratios (RRs) from a modified Poisson regression model.

RESULTS

Overall, 1419 women had a preconception history of VTE, while 578 112 did not. Preeclampsia occurred in 4.2% of pregnancies in the VTE group and in 2.7% of pregnancies in a comparison cohort (adjusted RD = 1.3%, 95% confidence interval (CI) 0.6-2.0%; adjusted RR = 1.5, 95% CI 1.3-1.8). Stillbirth occurred in 0.7% of pregnancies in the VTE group and in 0.4% of pregnancies in the comparison cohort (adjusted RD = 0.3%, 95% CI 0.02-0.6%; adjusted RR = 1.8, 95% CI 1.1-3.0). Placental abruption occurred in 0.8% of pregnancies in the VTE group and in 0.5% of pregnancies in the comparison cohort (adjusted RD = 0.3%, 95% CI - 0.05-0.6%; adjusted RR = 1.6, 95% CI 1.1-2.4). Small-for-gestational-age infants accounted for 10.9% of live births in the VTE group and 9.8% of live births in the comparison cohort (adjusted RD = 0.6%, 95% CI - 0.5-1.7%; adjusted RR = 1.1, 95% CI 0.9-1.3).

CONCLUSION

Women with a history of VTE were at increased risk of placenta-mediated complications.

The influence of type 2 diabetes on fibrin clot properties in patients with coronary artery disease

Type 2 diabetes mellitus (T2DM) increases the risk of coronary thrombosis and both conditions are associated with altered fibrin clot properties. However, the influence of T2DM on fibrin clot properties in patients with coronary artery disease (CAD) remains unclear. We aimed to investigate the influence of T2DM on fibrin clot properties in patients with CAD. Fibrin clot structure and fibrinolysis were investigated in 581 CAD patients (148 with T2DM) using turbidimetric assays, confocal and scanning electron microscopy. Clots made from plasma and plasma-purified fibrinogen were studied, and plasma levels of inflammatory markers were analysed. T2DM patients had increased clot maximum absorbance compared with non-diabetic patients (0.36 ± 0.1 vs 0.33 ± 0.1 au; p=0.01), displayed longer lysis time (804 [618;1002] vs 750 [624;906] seconds; p=0.03) and showed more compact fibrin structure assessed by confocal and electron microscopy. Fibrinogen levels were elevated in T2DM (p< 0.001), but clots made from purified fibrinogen showed no differences in fibrin properties in the two populations. Adjusting for fibrinogen levels, T2DM was associated with C-reactive protein and complement C3 plasma levels, with the former correlating with clot maximum absorbance (r=0.24, p< 0.0001) and the latter with lysis time (r=0.30, p< 0.0001). Independent of fibrinogen levels, females had more compact clots with prolonged lysis time compared with males (all p-values< 0.001). In conclusion, T2DM is associated with prothrombotic changes in fibrin clot properties in patients with CAD. This is related to quantitative rather than qualitative changes in fibrinogen with a possible role for inflammatory proteins.

Reduced antiplatelet effect of aspirin is associated with low-grade inflammation in patients with coronary artery disease

Inflammation has been proposed to modify platelet function. This may lead to increased platelet reactivity and reduced antiplatelet drug efficacy in patients with coronary artery disease (CAD). However, this hypothesis has not been investigated in stable CAD patients receiving aspirin as mono antiplatelet therapy. It was the objective of this study to investigate the association between platelet reactivity, the inflammatory markers high-sensitive C-reactive protein (hs-CRP) and interleukin-6 (IL-6), and platelet activation. We performed a cross-sectional study on 524 stable high-risk CAD patients. Among these, 91% had a history of myocardial infarction, 23% had type 2 diabetes, and 13% had both. All patients received 75 mg aspirin daily as mono antiplatelet therapy. Platelet reactivity was assessed by multiple electrode aggregometry (Multiplate®, MEA) and VerifyNow®. Inflammation was evaluated by hs-CRP and IL-6. Platelet activation was assessed by soluble P-selectin (sP-selectin), and cyclooxygenase-1 inhibition was evaluated by measurement of serum thromboxane B2. Hs-CRP levels were significantly higher in upper platelet reactivity tertile patients than in lower platelet reactivity tertile patients (p≤0.02). Similar results were obtained with IL-6, though not statististically significant (p≥0.15). Platelet activation evaluated by sP-selectin was significantly higher in patients with MEA reactivity levels in the upper tertile than in the lower tertile (p=0.0001). Optimal compliance was confirmed by low serum thromboxane B2 levels in all patients. In conclusion, increased levels of hs-CRP were associated with augmented platelet reactivity in stable high-risk CAD patients receiving aspirin as mono antiplatelet therapy. These findings may suggest that chronic low-grade inflammation reduce the antiplatelet effect of aspirin.

No evidence that assisted reproduction increases the risk of thrombosis: a Danish national cohort study

BACKGROUND

Case reports have reported venous and arterial thromboses in women undergoing assisted reproduction. No large systematic studies on the risk of thrombosis have been published. The objective of our study was to investigate whether the risk of thrombosis is increased in women undergoing assisted reproduction.

METHODS

A national register-based cohort study was conducted on all women undergoing IVF or ICSI treatment in Denmark from 1994 to 2005. Data were obtained from the National Patient Registry and the IVF Registry. Women with prior malignant or cardiovascular disease were excluded. Thrombosis occurring within the first 6 and 12 months after assisted reproduction was considered potentially related to the treatment. Thromboses during pregnancy as well as the pregnancy-related diagnoses were excluded from the statistical analysis. The incidence rates of venous and arterial thromboses were compared with previously published estimates of the risk of thrombosis among young Danish women.

RESULTS

We analyzed 30 884 Danish women undergoing 75 141 treatments from 1994 to 2005. The mean age of the women at first treatment was 32.3 years. The delivery rate per cycle was 22%. The incidence rate ratio, with 95% confidence interval (CI), of venous thrombosis within 6 months was 0.95 (CI: 0.38-1.95). The incidence rate ratio of arterial thrombosis within 6 months was 0.36 (CI: 0.04-1.30).

CONCLUSIONS

Our study showed no evidence that assisted reproduction increases the risk of thrombosis.

Urgent reversal of vitamin K antagonist therapy

In the developed world, an increasing number of patients receive therapy with vitamin K antagonists (VKA). This group of patients poses an additional challenge in the perioperative management of emergency surgery and trauma. The present review offers a detailed description of some treatment options for reversal of VKA therapy. Optimal treatment of the anticoagulated patient requires a well-balanced intervention securing a reduced risk of haemorrhagic surgical complications as well as optimal anticoagulation post-operatively without exposing the patient to an increased risk of thromboembolic complications. The following factors must be considered in VKA-treated patients scheduled for emergency surgery: (1) the indication for VKA therapy, including the risk of thromboembolic events when the International normalized ratio (INR) is reduced, (2) type of surgery, including the risk of haemorrhagic complications and (3) the pharmacodynamic/-kinetic profile of the therapy used to revert the VKA therapy. Therapeutic options for acute reversal of VKA therapy include: vitamin K, fresh frozen plasma (FFP), prothrombin complex concentrate (PCC) and perhaps activated recombinant factor VII. PCC is a relatively new drug in some European countries and clinical experience is limited compared with the use of FFP. Reversal of VKA anticoagulation with PCC is faster and more efficient compared with FFP, but there are currently no randomized studies demonstrating an improved clinical outcome.

Effect of platelet turnover on whole blood platelet aggregation in patients with coronary artery disease

BACKGROUND

Previous studies have demonstrated considerable variation in the antiplatelet effect of aspirin.

OBJECTIVES

To investigate the impact of platelet turnover on the antiplatelet effect of aspirin in patients with stable coronary artery disease (CAD) and to identify determinants of platelet turnover.

METHODS

Platelet turnover was evaluated by measurements of immature platelets and thrombopoietin in 177 stable CAD patients on aspirin monotherapy, including 85 type 2 diabetics and 92 non-diabetics. Whole blood platelet aggregation was determined using the VerifyNow(®) Aspirin test and multiple electrode aggregometry (MEA, Multiplate(®) ) induced by arachidonic acid (AA) (1.0 mm), adenosine diphosphate (ADP) (10 μm) and collagen (1.0 μg mL(-1) ).

RESULTS

Immature platelet levels significantly correlated with MEA (r = 0.31-0.36, P-values < 0.0001) and the platelet activation marker sP-selectin (r = 0.19, P = 0.014). Contrary to the VerifyNow(®) test, MEA significantly correlated with variations in platelet count (r = 0.45-0.68, P-values < 0.0001). Among patients with residual platelet reactivity according to AA, there were significantly more diabetics (61% vs. 41%, P = 0.027) and higher levels of sP-selectin (77.7 ± 29 vs. 70.2 ± 25 ng mL(-1) , P = 0.070) and serum thromboxane B(2) (0.81 [0.46; 1.70] vs. 0.56 [0.31; 1.12] ng mL(-1) , P = 0.034). In a multivariate regression analysis, immature platelet levels were determined by thrombopoietin levels (P < 0.001), smoking (P = 0.020) and type 2 diabetes (P = 0.042).

CONCLUSIONS

The antiplatelet effect of aspirin was reduced in CAD patients with an increased platelet turnover. Once-daily dosing of aspirin might not suffice to adequately inhibit platelet aggregation in patients with an increased platelet turnover.

Reduced platelet response to aspirin in patients with coronary artery disease and type 2 diabetes mellitus

INTRODUCTION

Diabetes mellitus is complicated by accelerated atherosclerosis, resulting in an increased risk of coronary artery disease (CAD) and thrombosis. Despite the proven benefits of aspirin, previous studies indicate a reduced cardiovascular protection from aspirin in diabetic patients. We aimed to investigate whether diabetes mellitus influenced the platelet response to aspirin in patients with CAD.

MATERIALS AND METHODS

Platelet aggregation and activation were evaluated during aspirin treatment in 85 diabetic and 92 non-diabetic patients with CAD. Adherence to aspirin was carefully controlled. All patients had CAD verified by coronary angiography and were taking 75 mg non-enteric coated aspirin daily.

RESULTS

Diabetic patients showed significantly higher levels of platelet aggregation compared to non-diabetic patients evaluated by VerifyNow® Aspirin (p=0.03) and Multiplate® aggregometry using arachidonic acid (AA) 0.5 mM (p=0.005) and 1.0 mM (p=0.009). In addition, platelet activation determined by soluble P-selectin was significantly higher in diabetics compared to non-diabetics (p=0.005). The higher AA-induced aggregation was associated with higher levels of HbA(1c). Compliance was confirmed by low levels of serum thromboxane B(2) (below 7.2 ng/mL). Diabetics had significantly higher levels of serum thromboxane B(2) (p<0.0001).

CONCLUSIONS

Diabetic patients with CAD had significantly higher levels of both platelet aggregation and activation compared to non-diabetic patients with CAD despite treatment with the same dosage of aspirin. These findings may partly explain the reduced cardiovascular protection from aspirin in diabetic patients.

Health technology assessment in clinical biochemistry. Methylmalonic acid: a Danish showcase

In 1992 plasma methylmalonic acid (MMA) was introduced in Denmark for diagnosing vitamin B-12 deficiency. Now, 10 years later, we report on a health technology assessment (HTA) suggesting that the clinical usefulness of MMA is uncertain. MMA is an obvious component for measurement in the diagnosis of vitamin B-12 deficiency because MMA accumulates when there is a lack of vitamin B-12, and technologically the analysis is of high quality. The diagnostic sensitivity of MMA is high, whereas the diagnostic specificity is debatable, and our results suggest it to be relatively low. The organizational aspect implies that both MMA and P-cobalamins have been increasingly employed, though no consensus on the use of the analyses has emerged. The benefit to the patient is not obvious. An increased level of MMA does not predict further increases over time, and vitamin B-12 treatment shows limited clinical benefit in individuals with a moderately increased MMA. The economic consequences of introducing MMA were an increase in the costs of MMA and P-cobalamins of 12% per year during 1992-2000 and an increase in the turnover of vitamin B-12 preparations of 9% per year. In conclusion, MMA was introduced on sound grounds for both pathophysiological considerations and analytical quality. Our HTA shows that the resources employed to diagnose and to treat vitamin B-12 deficiency have increased considerably, but yet we have no evidence to suggest the clinical benefit.

Tranexamic acid combined with recombinant factor VIII increases clot resistance to accelerated fibrinolysis in severe hemophilia A

BACKGROUND

Most patients with severe hemophilia A suffer from a profoundly compromised hemostatic response. In addition to both the delayed and slow development of a clot, previous studies have documented that severe hemophilia A is also associated with reduced clot stability.

OBJECTIVES

We examined whether the clot stability in hemophiliacs could be improved by treatment with tranexamic acid (TXA) in combination with recombinant factor VIII (rFVIII).

PATIENTS/METHODS

Baseline blood samples were obtained from eight males with severe hemophilia A. Thereafter, a bolus injection of rFVIII was administered to increase the functional level of FVIII to approximately 50%. After 10 min, blood was collected followed by an intravenous injection of TXA. A third blood sample was obtained after a further 10 min. Whole blood clotting profiles were determined by thrombelastography using minimal tissue factor activation. Clot formation was assessed by both clot initiation and clot propagation. At clot termination, the maximum clot firmness and area under the elasticity curve were used to illustrate clot stability. Tissue-plasminogen activator was included in those experiments designed to assess clot stability.

RESULTS

As expected, rFVIII increased clot formation, whereas TXA had no effect upon this parameter. Assays including tissue-plasminogen activator revealed that rFVIII increased the maximum clot firmness 3-fold; whereas the presence of TXA induced an additional 4-fold increase. The area under the elasticity curve increased 5-fold after rFVIII and 24-fold after addition of TXA.

CONCLUSIONS

The study demonstrates that simultaneous treatment with TXA and rFVIII significantly improves the clot stability in patients with hemophilia A.

Vitamin B12 and vitamin B6 supplementation is needed among adults with phenylketonuria (PKU)

Phenylketonuria (PKU) is caused by an autosomal recessive deficiency of the enzyme phelnylalanine hydroxylase leading to a failure to convert phenylalanine to tyrosine. To avoid irreversible neurological damage because of increased phenylalanine, treatment is instituted rapidly after birth. We examined 31 adult PKU patients living on a less protein-restricted diet. Theoretically, these PKU patients had an increased risk of developing vitamin B(12) and B(6) deficiency because of a limited intake of animal products. Besides laboratory tests (n = 31) we obtained clinical information (n = 30) and detailed information on food consumption (n = 28). Three-quarters of the patients had early biochemical signs of vitamin B(12) deficiency. In spite of a normal folate status, 9 (29%) had a plasma homocysteine above 12 micromol/L. In accord with these findings, the food questionnaires indicated that 11 (39%) patients received less than the recommended daily vitamin B(12), and 20 (71%) received less vitamin B(6) than recommended. A significant association was found between reduced vitamin B(12) intake and both reduced serum cobalamins (p = 0.04) and reduced serum transcobalamin saturation (p = 0.03). Eleven patients took a vitamin pill daily, and these patients had a significantly lower plasma homocysteine compared to the rest. The present study suggests that adult PKU patients were at increased risk of developing vitamin B(12) deficiency, and their intake of vitamin B(6) was below the recommended daily intake. In conclusion PKU patients need continuing dietary guidance throughout adult life, and considering the risks, costs and potential benefits, daily vitamin supplementation seems justified in these patients.

Holotranscobalamin--a first choice assay for diagnosing early vitamin B deficiency?

OBJECTIVES

The performance of holotranscobalamin (holoTC) was compared with the other markers of vitamin B12 deficiency, and the influence of age, renal function, and thyroid status was examined.

DESIGN AND INTERVENTIONS

We examined 937 individuals not treated with vitamin B12 but in whom vitamin B12 deficiency was suspected because of a plasma methylmalonic acid (MMA) above 0.28 micromol L(-1) within the past 4 years. Besides laboratory tests, a structured interview and a neurological examination were performed amongst 534 individuals. Amongst these, 140 individuals qualified for a randomized trial (MMA 0.40-2.00 micromol L(-1)). They were randomized to injections with vitamin B12 or placebo and re-examined after 3 months.

SETTING

One university hospital in Aarhus, Denmark.

RESULTS

The ROC curves indicate that holoTC (AUC: 0.90) compared favourable with plasma vitamin B12 (AUC: 0.85) for identifying individuals likely to have vitamin B12 deficiency (MMA > or =0.75 micromol L(-1) and plasma total homocysteine (tHcy) > or =15 micromol L(-1)), and further that holoTC (AUC: 0.91) might replace combined testing with plasma vitamin B12 and the metabolites. No association was observed between the biochemical markers and symptoms and signs possibly related to vitamin B12 deficiency. HoloTC, TC saturation, plasma vitamin B12, MMA, and tHcy were significantly associated with plasma creatinine (all with P <0.001). Only tHcy was significantly associated with thyroid stimulating hormone (P=0.02).

CONCLUSIONS

HoloTC shows promise as first-line tests for diagnosing early vitamin B12 deficiency.

Vitamin B-12 treatment has limited effect on health-related quality of life among individuals with elevated plasma methylmalonic acid: a randomized placebo-controlled study

OBJECTIVE

To examine the hypothesis that treatment with vitamin B-12 improves health-related quality of life (HRQOL) in individuals with biochemical signs of vitamin B-12 deficiency.

DESIGN

A randomized placebo-controlled study.

SETTING

Municipality of Aarhus, Denmark.

SUBJECTS

Nonhospitalized individuals (n = 140) with a modest increase in plasma methylmalonic acid (0.40-2.00 micromol L-1) not previously treated with vitamin B-12.

INTERVENTION

The participants were randomized to vitamin B-12 injection treatment or placebo weekly for 4 weeks and re-examined 3 months later. The investigator and the participants were blinded to the intervention.

MAIN OUTCOME MEASURE

Change in HRQOL assessed by the SF-36 questionnaire from baseline to follow-up examination 3 months later.

RESULTS

The participants reported a significantly worser HRQOL than the age- and sex-matched Danish general population (P < 0.001). However, no change was observed after treatment with vitamin B-12 for seven of eight health dimensions. A significant improvement was found only in general health when compared with the placebo group (P = 0.03).

CONCLUSIONS

Vitamin B-12 treatment influenced only one of eight dimensions of HRQOL amongst participants with biochemical signs of vitamin B-12 deficiency. We therefore question the benefit of vitamin B-12 treatment amongst elderly with a modestly increased plasma methylmalonic acid as the only sign of vitamin B-12 deficiency.

Vitamin B12 treatment normalizes metabolic markers but has limited clinical effect: a randomized placebo-controlled study

BACKGROUND

The clinical significance of increased plasma methylmalonic acid (P-MMA) is unclear. We assessed the efficacy of vitamin B12 treatment in reducing P-MMA and plasma total homocysteine compared with the clinical benefits of treatment.

METHODS

We studied 140 individuals with mildly to modestly increased P-MMA (0.40-2.00 micromol/L), not previously treated with vitamin B12, in a randomized, placebo-controlled study. A detailed medical history was obtained, and laboratory tests as well as an objective neurologic disability score were performed at baseline and 3 months after the start of intervention.

RESULTS

P-MMA (P <0.001) or plasma total homocysteine (P <0.001) decreased in the treatment group vs the placebo group, but no significant difference was found in the change of blood hemoglobin (P = 0.18) and mean cell volume (P = 0.71). Changes in symptom scores did not differ between the groups for symptoms of anemia (P = 0.63), neurologic symptoms (P = 0.21), gastroenterologic symptoms (P = 0.32), or the Neurological Disability Score (P = 0.85).

CONCLUSIONS

Treatment with vitamin B12 reduces P-MMA and plasma total homocysteine, but individuals with a mild to modest increase in P-MMA may have only limited clinical benefit from vitamin B12 treatment, at least in the short term.

Increased plasma methylmalonic acid level does not predict clinical manifestations of vitamin B12 deficiency

BACKGROUND

The prevalence of vitamin B(12) deficiency, defined as an elevated concentration of plasma methylmalonic acid (P-MMA), has been estimated to be 15% to 44% in the elderly. However, we do not know whether an increased P-MMA level actually indicates or predicts a clinical condition in need of treatment.

PARTICIPANTS AND METHODS

In a follow-up study, 432 individuals not treated with vitamin B(12) were examined 1.0 to 3.9 years after initial observation of an increased P-MMA concentration (>0.28 micromol/L). The examination included laboratory tests, a structured interview to disclose symptoms, a food frequency questionnaire, and a clinical examination including a Neurological Disability Score.

RESULTS

Variation in P-MMA levels over time was high (coefficient of variation, 34%). In only 16% of participants, P-MMA levels increased substantially, whereas 44% showed a decrease. Level of P-MMA was significantly but not strongly associated with levels of plasma cobalamins (r = -0.22, P<.001) and plasma total homocysteine (r = 0.37, P<.001). After adjustment for age and sex, we found no associations between P-MMA concentration and the total symptom score (P =.61), the total Neurological Disability Score (P =.64), or other clinical manifestations related to vitamin B(12) deficiency.

CONCLUSIONS

An increased level of P-MMA did not predict a further increase with time and clinical manifestations related to vitamin B(12) deficiency. We therefore challenge the use of an increased P-MMA concentration as the only marker for diagnosis of vitamin B(12) deficiency.

The marker of cobalamin deficiency, plasma methylmalonic acid, correlates to plasma creatinine

OBJECTIVE

To examine the relationship between the two diagnostic tests, plasma methylmalonic acid and plasma cobalamins, and their association with plasma creatinine, age and sex.

DESIGN

Cross-sectional study of simultaneous laboratory measurements.

SETTING

County of Aarhus, Denmark.

SUBJECTS

Records on 1689 patients who had their first plasma methylmalonic acid measurement during 1995 and 1996, and who had a simultaneous measurement of plasma cobalamins. Plasma creatinine values measured within a week of measurements of plasma methylmalonic acid and plasma cobalamins were available for 1255 of the patients.

MAIN OUTCOME MEASURES

Predictors of variation in plasma methylmalonic acid; plasma cobalamins, plasma creatinine, age and sex.

RESULTS

Plasma methylmalonic acid was positively correlated with plasma creatinine, even for plasma creatinine within the normal range. These associations remained in a multiple regression analysis. For plasma cobalamins below 200 pmol L-1, there was a strong negative correlation between plasma methylmalonic acid and plasma cobalamins, whilst the association was weak for higher plasma cobalamin levels. Plasma methylmalonic acid increased and plasma cobalamins decreased with age.

CONCLUSIONS

The strong correlation between plasma methylmalonic acid and plasma creatinine suggests that plasma creatinine - also within the normal range - must be taken into consideration when interpreting plasma methylmalonic acid.

Physicians' use of plasma methylmalonic acid as a diagnostic tool

OBJECTIVES

To investigate physicians' reasons for requesting plasma methylmalonic acid and their reactions to an increased concentration of plasma methylmalonic acid.

DESIGN

Study of medical records.

SETTING

Three somatic district hospitals in Denmark.

SUBJECTS

Medical records of 198 patients with a plasma methylmalonic acid measurement above the reference interval. Information on diagnostic decisions was available for 177 patients.

MAIN OUTCOME MEASURES

Reasons for requesting plasma methylmalonic acid and the reactions to the finding of elevated plasma methylmalonic acid.

RESULTS

An explicit reason for requesting plasma methylmalonic acid was stated in 57% of 198 examined medical records, known or suspected anaemia being the most frequent reason. No further action was taken in 109 (62%) of the 177 cases available for follow-up. Amongst the remaining 68 patients, the finding of an increased plasma methylmalonic acid led to diagnosis of cobalamin deficiency in 46 patients. Six patients with a markedly increased plasma methylmalonic acid (above 0.99 micromol L-1) and clearly decreased plasma cobalamins (below 200 pmol L-1) were not recognized as having cobalamin deficiency.

CONCLUSIONS

This lack of response to an increased plasma methylmalonic acid raises an important question. Is the clinical response inadequate, or is the connection between an increased level of plasma methylmalonic acid and signs of clinical significant cobalamin deficiency less clear?