Home Treatment of Patients with Pulmonary Embolism: A Single Center 10-Year Experience from Ljubljana Registry

Current guidelines suggest careful risk stratification using a structured clinical approach when selecting patients with pulmonary embolism (PE) for home treatment. The aim of our study was to assess whether PE patients referred to home treatment are appropriately risk-stratified according to guidelines prior to referral and what the real-life course of the disease in these patients is. We included patients with confirmed PE referred to outpatient management and treated with anticoagulants between 2010 and 2019, whose data were collected in a prospective management registry. Using simplified PE severity index and/or signs of right ventricular strain, we classified patients to either appropriate or inappropriate low-risk classes for outpatient management. We compared 30-day mortality, overall mortality, and rates of recurrent thromboembolism or major bleeding between both classes. Among 278 patients, 188 (67.6%) and 90 (32.4%) were classified as appropriate or inappropriate class, respectively. In total, 30-day mortality was low in both groups: 0% in appropriate class and 1.1% in inappropriate class. The overall mortality rate was higher in the inappropriate than in the appropriate class (12.1 vs 0.9/100 patient-years, respectively, P < .001). Rates of recurrent thromboembolism and major bleeding were similar for both classes. We conclude that in real-life, a significant proportion of inappropriate low-risk class PE patients are referred to outpatient management. However, with careful follow-up, early mortality is low, even in home-treated patients inappropriately classified as low-risk.

Position Paper on the Management of Pregnancy-Associated Superficial Venous Thrombosis. Balkan Working Group for Prevention and Treatment of Venous Thromboembolism

Venous thromboembolism (VTE) is a multifactorial disease that can possibly affect any part of venous circulation. The risk of VTE increases by about 2 fold in pregnant women and VTE is one of the major causes of maternal morbidity and mortality. For decades superficial vein thrombosis (SVT) has been considered as benign, self-limiting condition, primarily local event consequently being out of scope of well conducted epidemiological and clinical studies. Recently, the approach on SVT has significantly changed considering that prevalence of lower limb SVT is twice higher than both deep vein thrombosis (DVT) and pulmonary embolism (PE). The clinical severity of SVT largely depends on the localization of thrombosis, when it concerns the major superficial vein vessels of the lower limb and particularly the great saphenous vein. If untreated or inadequately treated, SVT can potentially cause DVT or PE. The purpose of this review is to discuss the complex interconnection between SVT and risk factors in pregnancy and to provide evidence-based considerations, suggestions, and recommendations for the diagnosis and treatment of this precarious and delicate clinical entity.

Upper extremities deep vein thrombosis treated with oral direct anticoagulants: A prospective cohort study

BACKGROUND

Limited data are available on the role of direct oral anticoagulants (DOACs) for the treatment of upper extremities deep vein thrombosis (UEDVT).

OBJECTIVES

The aim of this study was to assess the effectiveness and safety of DOACs in the treatment of UEDVT.

METHODS

Patients with an objectively confirmed acute UEDVT treated with DOACs were merged from prospective cohorts to a collaborative database. Primary study outcomes were recurrent venous thromboembolism (VTE) and major bleeding occurring during DOAC treatment.

RESULTS

Overall, 188 patients were included in the study: mean age 52.4 ± 20.4 years, males 43.6%, patients with active cancer 29.2%. Twenty-nine percent of patients had 2 or more risk factors for VTE, 33.0% had catheter-related or pacemaker-related UEDVT. In 13.8% of patients, DOACs were started one month after UEDVT diagnosis or later. Active cancer was an independent predictor for delayed initiation of DOACs (OR 8.1, 95% CI 3.0-22.2). Mean duration of treatment with DOACs was 5.1 ± 2.8 months. During treatment with DOACs, recurrent VTE occurred in 0.9 per 100 patient-year, major bleeding in 1.7 and all-cause deaths in 6.0 per 100 patient-year. No fatal bleeding or fatal VTE recurrence were observed. During 232.1 patient-years of follow-up after DOAC withdrawal, recurrent VTE occurred in 3.0 per 100 patient-year. The 2019 ESC categories for risk of VTE recurrences were able to discriminate patient groups at different risk of events in the on and off-treatment periods.

CONCLUSIONS

Our data support the feasibility as well as the effectiveness and safety of DOACs for the treatment of acute UEDVT.

Upper extremities deep vein thrombosis and DOAC treatment: a prospective cohort study

Background

Data on the use of direct oral anticoagulants (DOACs) in patients with upper extremities deep vein thrombosis (UEDVT) are limited.

Purpose

To assess the effectiveness and safety of DOACs in the treatment of UEDVT.

Methods

Data on patients with an objective diagnosis of acute UEDVT treated with DOACs were merged from prospective cohorts of patients with venous thromboembolism (VTE). Study outcomes were recurrent VTE and major bleeding (MB) occurring during DOAC treatment.

Results

Overall, 132 patients were included: mean age was 47.7±18.0 years (range 18 to 97), males were 42.4%. Twenty-seven percent of patients had 2 or more risk factors for VTE, 29.5% had UEDVT complicating a central venous line or after pacemaker implantation (Table). Ninety-two patients (70%) were managed as outpatients. Increased age (OR 1.03, 95% CI 1.0–1.05) and anemia (OR 1.35, 95% CI 1.07–1.70) were associated with in-patient management. Among patients treated with apixaban (40) or rivaroxaban (85) loading dose was used in 72%; in patients treated with dabigatran (5) or edoxaban (2) mean heparin pre-treatment was 8 days. DOACs were started after 1 month from UEDVT diagnosis in 12.9% of patients; active cancer was a main predictor for delayed initiation (OR 22.2, 95% CI 5.8–84.4). Mean treatment duration in patients with a scheduled stop was 4.9 months, while mean followup in those who continued DOACs was 9.3 months. No recurrence of VTE nor MBs occurred during DOAC treatment; one patient had acute limb ischemia (1.38% patient-year), 7 clinically relevant non-MBs (3 genital, 2 epistaxis, 1 gingival, 1 genital bleeding plus epistaxis; 10.51% patient-year), 5 deaths (4 cancer, 1 advanced age; 9.69% patient-year).

Conclusions

Our data support the effectiveness and safety of DOACs for the treatment of acute UEDVT. Further studies are required to confirm these findings.

Funding Acknowledgement

Type of funding source: None

Turbulent axially directed flow of plasma containing rt-PA promotes thrombolysis of non-occlusive whole blood clots in vitro

The rate of thrombolysis markedly decreases after a thrombosed vessel is partly recanalized and the remaining clot poses serious risk for rethrombosis. We studied in vitro how thrombolysis depends on penetration of plasma containing thrombolytic agents – 0.2 μg/ml rt-PA or 250 IU/ml streptokinase (SK) nd the magnetic resonance contrast agent Gd-DTPA (at 1 mmol/l) into non-occlusive clots under conditions of fast (turbulent) or slow (laminar) axially directed flow. Cylindrical non-retracted (fresh) or retracted (aged) whole blood clots were pierced lengthways and connected to a perfusion system. Dynamical spin-echo MRI was used for measuring the penetration of labeled plasma into clots and for assessing the remaining clot size. In both types of clots fast flow enhanced the penetration of Gd-DTPA-labeled plasma into clots in comparison to slow flow. In non-retracted clots, lysis with rt-PA and to a lesser extent also lysis with SK followed the path of plasma penetration into clots. After 40 minutes of fast axially directed flow rt-PA resulted in almost complete lysis and SK left only about a third of the clot undissolved, whereas with slow flow lysis was much slower (undissolved clot: 86 ± 5 % with rt-PA and 95 ± 1 % with SK). In retracted clots, substantial lysis was possible only with rt-PA and rapid flow (53 ± 28% of the clot undissolved after 60 min), whereas the use of SK or slow flow precluded meaningful lysis. We conclude that rapid (turbulent) axially directed flow of plasma along non-occlusive blood clots causes forceful exchange of serum inside the clot with outer plasma which enhances both fibrin-specific and non-fibrin-specific lysis of fresh clots. Dissolution of non-occlusive retracted (aged) clots occurs only under fibrin-specific conditions combined with adequate transport of rt-PA into clots.

Risk of Thromboembolic Events in Patients with Non-Valvular Atrial Fibrillation After Dabigatran or Rivaroxaban Discontinuation - Data from the Ljubljana Registry

Background and Aim

Interruption of anticoagulant treatment with warfarin or non-vitamin K antagonist oral anticoagulants (NOAC) represents a vulnerable period with an increased risk of thromboembolic events. What is the incidence of thromboembolic events in real-life patients with non-valvular atrial fibrillation treated with NOAC who had a discontinuation or cessation of treatment in comparison to patients on continuous treatment?

Patients and Methods

Registry data from 866 patients with non-valvular atrial fibrillation, aged 74.3 (SD 9.8) years, with an average CHADS₂ score of 2.1 (SD 1.2), who were started on dabigatran or rivaroxaban, were analysed for thromboembolic events and survival. Patients who had temporary or permanent discontinuation of NOAC were compared to patients on continuous NOAC treatment.

Results

Among 866 patients started on NOAC, 705 were treated without interruption, 84 patients had temporary interruption (69 because of planned invasive procedures, 10 due to bleeding, 5 for other causes) and 77 had permanent cessation of NOAC treatment. In patients without interruptions, the incidence of thromboembolic events was 1.0 (95% CI 0.4–2.1) per 100 patient-years, while in patients with interruption/cessation the rate of thromboembolic events was 21.6 (95% CI 10.3–45.2) per 100 patient-years, p < 0.001. There was a distinct clustering of thromboembolic events in the first weeks of NOAC discontinuation with the median occurring on day 14 (range 1–37 days) after discontinuation.

Conclusion

Dabigatran and rivaroxaban offered good protection against thromboembolic events during treatment, but interruption of NOAC treatment increased the short-term thromboembolic risk more than 20-fold.

Comparison of plasmin with recombinant tissue-type plasminogen activator in lysis of cerebral thromboemboli retrieved from patients with acute ischemic stroke

BACKGROUND AND PURPOSE

Plasmin is a direct-acting thrombolytic with a better safety profile than recombinant tissue-type plasminogen activator (rtPA) in animal models. With the application of retrieval devices for managing acute ischemic stroke, extracted thromboemboli are available for ex vivo examination. We ask whether such thrombi are amenable to plasmin thrombolysis and whether such activity is different with rtPA.

METHODS

Thromboembolic fragments (total 29) were retrieved from the intracranial carotid artery system of 15 patients with acute ischemic stroke and randomly assigned to ex vivo thrombolysis with plasmin or rtPA. After an initial 2-hour exposure, residual material was exposed to the other agent for an additional 2 hours. Thrombolysis was quantified by change in thrombus area and released d-dimer.

RESULTS

Plasmin induced significant ex vivo thrombolysis of cerebral arterial thromboemboli, decreasing area by 45.9% ± 29.4% and 69.2% ± 52.5% and inducing median D-dimer release of 108,180 μg/L (range, 16,780 to 668,050 μg/L) and 16,905 μg/L (range, 240 to 403 085 μg/L) during the first and second 2-hour incubation periods, respectively. These changes were not different from those obtained with rtPA, which decreased area by 34.7% ± 57.8% (P=0.63) and by 68.4% ± 26.9% (P=0.97) and induced median D-dimer release of 151,990 μg/L (range, 9870 to 338,350 μg/L; P=0.51) and 34,520 μg/L (range 3794 to 325,400 μg/L; P=0.19) during the first and second 2-hour incubations.

CONCLUSIONS

Retrieved human cerebral thromboemboli were amenable to ex vivo lysis by plasmin, the rate and degree of which was not different than that achieved with rtPA.

Discrimination between red blood cell and platelet components of blood clots by MR microscopy

Magnetic resonance imaging (MRI) of pulmonary emboli obtained ex vivo, verified by immunohistochemistry, showed that platelet layers display brighter signal intensity than areas containing predominantly red blood cells (RBC) in T1-weighted MRI. These results were surprising since platelets do not contain paramagnetic haemoglobin that would enhance magnetic relaxation. Our assumption was that the fibrin meshwork areas with entrapped RBC retain abundant extracellular space filled with serum, whereas platelets regroup into tight aggregates lacking serum, essentially mimicking solid tissue structure, rich with cellular proteins that enhance T1-relaxation. Our hypothesis was examined by MRI and NMR relaxometry of in vitro RBC suspensions and sedimented platelets, as well as by MRI of model clots and pulmonary emboli obtained ex vivo. Pure sedimented platelets exhibited shorter proton spin lattice relaxation times (T1 = 874 +/- 310 ms) than those of venous blood of a healthy male with 40% haematocrit (T1 = 1277 +/- 66 ms). T1-values of RBC samples containing high haematocrit (> or = 80%) resembled T1 of platelet samples. In T1-weighted spin-echo MRI echo time and repetition time (TE/TR = 10/120 ms) the ratio of signal intensities between a non-retracted whole blood clot (with a haematocrit of 35%) and a pure platelet clot was 3.0, and the ratio between a retracted whole blood clot with an estimated haematocrit of about 58% and a pure platelet clot was 2.6. We conclude that T1-weighted MRI can discriminate between platelet layers of thrombi and RBC-rich areas of thrombi that are not compacted to a haematocrit level of > or = 80%.

Modelling the effect of laminar axially directed blood flow on the dissolution of non-occlusive blood clots

Axially directed blood plasma flow can significantly accelerate thrombolysis of non-occlusive blood clots. Viscous forces caused by shearing of blood play an essential role in this process, in addition to biochemical fibrinolytic reactions. An analytical mathematical model based on the hypothesis that clot dissolution dynamics is proportional to the power of the flowing blood plasma dissipated along the clot is presented. The model assumes cylindrical non-occlusive blood clots with the flow channel in the centre, in which the flow is assumed to be laminar and flow rate constant at all times during dissolution. Effects of sudden constriction on the flow and its impact on the dissolution rate are also considered. The model was verified experimentally by dynamic magnetic resonance (MR) microscopy of artificial blood clots dissolving in an in vitro circulation system, containing plasma with a magnetic resonance imaging contrast agent and recombinant tissue-type plasminogen activator (rt-PA). Sequences of dynamically acquired 3D low resolution MR images of entire clots and 2D high resolution MR images of clots in the axial cross-section were used to evaluate the dissolution model by fitting it to the experimental data. The experimental data fitted well to the model and confirmed our hypothesis.

Characterization of pulmonary emboli ex vivo by magnetic resonance imaging and ultrasound

INTRODUCTION

Magnetic resonance imaging (MRI) and transesophageal ultrasound (US) are promising methods for detection and characterization of central pulmonary emboli. Both methods employ different physical principles. We tested how US and MRI characterized pulmonary emboli ex vivo.

METHODS

Thirty six ex vivo pulmonary emboli, obtained during routine autopsies of patients who died of massive pulmonary embolism, were subjected to US imaging (linear vascular probe, 5.7-10 MHz) and to high resolution three-dimensional T1-weighted spin-echo MRI. In another 3 pulmonary thromboemboli and 2 tumor emboli, we compared MRI with immunohistochemistry to platelets, red blood cells and renal carcinoma cells. We also studied model clots in vitro (retracted and non-retracted red whole-blood clots, platelet aggregates and compacted and non compacted fibrin-rich plasma clots) with MRI and US.

RESULTS

T1-weighted MR images of pulmonary thromboemboli consistently showed dark regions that corresponded to red cell-rich regions and bright layers that corresponded to platelet aggregates, but bright signal was obtained also from viable carcinoma cells and necrotic regions in tumor emboli. US images provided less structural detail than MRI, but clot retraction or compaction increased image brightness. The correlation between US and MRI characteristics of pulmonary emboli was poor.

CONCLUSIONS

T1-weighted MRI of pulmonary emboli is capable of non-invasive assessment of the red cell-rich and platelet-rich components of pulmonary thromboemboli. US imaging shows increased brightness with clot retraction or compaction. Thus, both methods detect clot characteristics that influence susceptibility to thrombolytic treatment.

Evidence of hypercoagulability and inflammation in young patients long after acute cerebral ischaemia

INTRODUCTION

Young subjects with acute cerebral ischaemia - stroke or transient ischaemic attack - form an etiologically heterogeneous and often not clearly explained group of patients. The aim was to investigate possible disturbances in haemostasis and inflammation long after an acute cerebral ischaemic event.

MATERIALS AND METHODS

Forty-four consecutive patients referred after having suffered from acute cerebral ischaemia before the age of 45 participated 1 to 9 years (median value 5 years) after the event. At the time of blood sampling 33 (75%) patients were receiving antithrombotic treatment. Forty-six apparently healthy subjects of the same age group served as controls. In all subjects global haemostasis parameters (overall haemostasis, coagulation and fibrinolytic potential), thrombophilia, several markers of haemostasis activation and inflammation were determined.

RESULTS

Patients did not differ from controls in most of the conventional risk factors and the presence of most forms of thrombophilia, although in seven (17.5%) patients the weak presence of lupus anticoagulants was observed. Patients had significantly increased overall haemostasis and coagulation potential, increased soluble P-selectin and D-dimer, decreased overall fibrinolysis potential and increased fibrinogen and C-reactive protein compared to controls. The subgroups of patients receiving antiplatelet treatment, with thrombophilia and recurrent acute cerebral ischaemia, did not differ significantly from the other patients.

CONCLUSIONS

In young patients long after acute cerebral ischaemia an imbalance in the haemostatic system and a minor, but significant degree of inflammation was detected. The mechanisms behind haemostatic imbalance seem to be enhanced thrombin generation, platelet activation and depressed fibrinolysis.

A mathematical model for the dissolution of non-occlusive blood clots in fast tangential blood flow

Our aim was to study the effect of an axially directed blood plasma flow on the dissolution rate of cylindrical non-occlusive blood clots in an in vitro flow system and to derive a mathematical model for the process. The model was based on the hypothesis that clot dissolution dynamics is proportional not only to the biochemical proteolysis of fibrin but also to the power of the flowing blood plasma dissipated along the clot. The predicted rate of thrombolysis is then proportional to the square of the average blood plasma velocity for laminar flow and to the third power of the average velocity for turbulent flow. To verify the model, the time dependence of the clot cross-sectional area was measured by dynamic magnetic resonance microscopy during fast (turbulent) and slow (laminar) flow of plasma through an axially directed channel along the clot. The flowing plasma contained a magnetic resonance imaging contrast agent (Gd-DTPA) and a thrombolytic agent (recombinant tissue-type plasminogen activator). The experimental data fitted well to the model, and confirmed the predicted increase in the dissolution rate when blood flow changed from a laminar to a turbulent flow regime.

Blood Clot Dissolution Dynamics Simulation during Thrombolytic Therapy

Nonocclusive blood clots only partially fill blood vessels and together with the adjacent vessel wall form a channel through which blood flows at usually much higher velocities than in normal vessels. Our aim was to find a theoretical explanation for the experimentally observed fact that fast flowing blood through the channel has a large effect on the increase of the clot dissolution rate compared to the dissolution rate in the absence of flow. Blood flow through the channel increases transport of dissolution agents to the clot and also exerts large forces to the surface of the clot along the channel. Proposed is a model for clot dissolution which assumes that the clot dissolution rate is proportional to the forces of flowing blood to the surface of the clot multiplied by the average blood velocity. The model has been verified by fitting to experimental magnetic resonance imaging data obtained by dynamical magnetic resonance microscopy of clots dissolved by recombinant tissue plasminogen activator in an artificial blood flow system.

Markers of hemostatic system activation during treatment of deep vein thrombosis with subcutaneous unfractionated or low-molecular weight heparin

Prothrombin fragments (F1+2), thrombin-antithrombin complexes (TAT) and D-dimers, markers of hemostatic system activation, were measured in 59 consecutive patients with deep vein thrombosis (DVT). Patients were randomly treated either with subcutaneous unfractionated heparin (UH) administered in two to three subcutaneous doses adjusted to activated partial thromboplastin time (APTT) or with low-molecular weight heparin (LMWH) (dalteparin) administered in a fixed dose of 200 IU/kg body weight in one subcutaneous injection daily. Before treatment, F1+2, TAT and D-dimer were above the cut-off level in 27/59 (46%), 34/59 (58%) and all (100%) patients, respectively. Significant associations were observed between F1+2 and TAT (r=.66, P<.001), TAT and D-dimer (r=.36, P<.005) and F1+2 and D-dimer (r=.30, P<.050). On the third day of treatment, F1+2 and TAT significantly decreased to reference values in almost all patients (in 64/66 determinations of both F1+2 and TAT) and remained low on the seventh day of treatment. Compared to pretreatment values, a nonsignificant decrease of D-dimer was noted in both groups, but all values remained above the cut-off value. When markers of hemostatic system activation in the UH and LMWH groups were compared, no significant differences were observed. It was concluded that subcutaneous UH in an APTT-adjusted dose and subcutaneous LMWH in a once-daily weight-adjusted dose controlled these markers of hemostatic system activation in a similar manner.