Pulmonary Embolism Model Research Articles

Detection of Pulmonary Embolism with Gallium-68 Macroaggregated Albumin Perfusion PET/CT: An Experimental Study in Rabbits.

This study was designed to evaluate the accuracy of detecting pulmonary embolism (PE) using the Technegas SPECT/CT combined with 68Ga PET/CT in a rabbit model. One hour after artificial PE (n = 6) and sham (n = 6) models were created, Technegas SPECT/CT ventilation and 68Ga-MAA PET/CT perfusion scan (V/Q scan) were performed. Ventilation imaging was performed first on all cases. Technegas SPECT/CT and 68Ga-MAA PET/CT images were evaluated by a nuclear medicine physician who recorded the presence, number, and location of PE on a per-lobe basis. The sensitivity, specificity, and accuracy of Technegas SPECT/CT and 68Ga-MAA PET/CT for detecting PE were calculated using a histopathological evaluation as a reference standard. A total of 60 lung lobes were evaluated in 12 rabbits, and PE was detected in 20 lobes in V/Q scans and histopathological analysis. The overall sensitivity, specificity, and accuracy were 100%, 100%, and 100%, respectively, for both the Technegas SPECT/CT and 68Ga-MAA PET/CT V/Q scans. Technegas/68Ga-MAA V/Q scans have good sensitivity, specificity, and accuracy in the detection of PE in this animal model study.

Right ventricular adaptation in the critical phase after acute intermediate-risk pulmonary embolism.

The haemodynamic response following acute, intermediate-risk pulmonary embolism is not well described. We aimed to describe the cardiovascular changes in the initial, critical phase 0-12 hours after acute pulmonary embolism in an in-vivo porcine model. Pigs were randomly allocated to pulmonary embolism (n = 6) or sham (n = 6). Pulmonary embolism was administered as autologous blood clots (20 × 1 cm) until doubling of mean pulmonary arterial pressure or mean pulmonary arterial pressure was greater than 34 mmHg. Sham animals received saline. Cardiopulmonary changes were evaluated for 12 hours after intervention by biventricular pressure-volume loop recordings, invasive pressure measurements, arterial and central venous blood gas analyses. Mean pulmonary arterial pressure increased (P < 0.0001) and stayed elevated for 12 hours in the pulmonary embolism group compared to sham. Pulmonary vascular resistance and right ventricular arterial elastance (right ventricular afterload) were increased in the first 11 and 6 hours, respectively, after pulmonary embolism (P < 0.01 for both) compared to sham. Right ventricular ejection fraction was reduced (P < 0.01) for 8 hours, whereas a near-significant reduction in right ventricular stroke volume was observed (P = 0.06) for 4 hours in the pulmonary embolism group compared to sham. Right ventricular ventriculo-arterial coupling was reduced (P < 0.05) for 6 hours following acute pulmonary embolism despite increased right ventricular mechanical work in the pulmonary embolism group (P < 0.01) suggesting right ventricular failure. In a porcine model of intermediate-risk pulmonary embolism, the increased right ventricular afterload caused initial right ventricular ventriculo-arterial uncoupling and dysfunction. After approximately 6 hours, the right ventricular afterload returned to pre-pulmonary embolism values and right ventricular function improved despite a sustained high pulmonary arterial pressure. These results suggest an initial critical and vulnerable phase of acute pulmonary embolism before haemodynamic adaptation.

Terlipressin Increases Systemic and Lowers Pulmonary Arterial Pressure in Experimental Acute Pulmonary Embolism.

We investigated whether the vasopressin-analog, terlipressin induces systemic vasoconstriction and pulmonary vasodilation in a porcine model of acute pulmonary embolism. Controlled, animal study. Tertiary medical center research laboratory. Female pigs (n = 12, Cross of Land Race, Duroc, and Yorkshire ~ 60 kg). Acute pulmonary embolism was induced by administration of three large autologous emboli. Animals then received four increasing doses of either terlipressin (n = 6) or vehicle (n = 6). Effects were evaluated in vivo at baseline, after pulmonary embolism and after each dose by invasive hemodynamic measures, transesophageal echocardiography, and blood analysis. Isolated pulmonary arteries were evaluated ex vivo in a myograph. Pulmonary embolism caused a four-fold increase in pulmonary vascular resistance (p < 0.0001) and a two-fold increase in mean pulmonary arterial pressure (p < 0.0001) compared with baseline. Terlipressin increased mean systemic blood pressure (28 ± 5 mm Hg; p < 0.0001) and systemic vascular resistance (1,320 ± 143 dynes; p < 0.0001) compared with vehicle. In the pulmonary circulation, terlipressin decreased mean pulmonary arterial pressure (-6.5 ± 1.8 mm Hg; p = 0.005) and tended to decrease pulmonary vascular resistance (-83 ± 33 dynes; p = 0.07). Terlipressin decreased cardiac output (-2.5 ± 0.5 L/min; p < 0.0001) and increased plasma lactate (2.7 ± 0.2 mmol/L; p < 0.0001), possibly indicating systemic hypoperfusion. A biomarker of cerebral ischemia, S100b, remained unchanged, suggesting preserved cerebral perfusion (0.17 ± 0.11 µg/L; p = 0.51). Ex vivo, terlipressin relaxed pulmonary and constricted mesenteric arteries. Terlipressin caused systemic vasoconstriction and pulmonary vasodilation in a porcine in vivo model of acute pulmonary embolism and vasorelaxation in isolated pulmonary arteries. Despite positive vascular effects, cardiac output declined and plasma lactate increased probably due to a predominantly systemic vasoconstrictor effect of terlipressin. These findings should warrant careful translation to the clinical setting and does not suggest routine use in acute pulmonary embolism.

Reteplase Encapsulated in Minocycline‐Containing Nanoparticles Retains Thrombolytic Activity

Thrombolytic therapy is a critical potion of the treatment regimen for a number of life‐threatening conditions, including cardiovascular disease and stroke. Although thrombolytic drugs have shown profound effect on dissolving clots, short half‐life (t1/2 of minutes) and hemorrhagic complications are significant challenges associated with their use. Nanotechnology has shown to prolong the blood circulation time of drugs and to improve their efficacy and safety. However, leakage of thrombolytic drug‐loaded nanocarriers (NC) from intravascular compartment into brain parenchyma due to compromised blood‐brain barrier integrity following ischemia can still lead to adverse effects. Therefore, it is necessary to combine neuroprotection with thrombolysis therapy in ischemic stroke treatment. Here we have developed NC that contains reteplase, an engineered tissue‐type plasminogen activator, and minocycline, a neuroprotective agent. The formation of the NC is based on metal ion‐assisted self‐assembly of complexes using negatively charged heparin and minocycline. The reteplase is incorporated into the NC through a protein binding site on minocycline. The entrapment efficiency of reteplase and minocycline were 91.8% and 78.3%, respectively. By tracing radiolabeled reteplase, our results showed that the NC significantly increased the blood circulation time of reteplase compared to free reteplase (Panel A). In the in vitro clot lysis assay, the free reteplase or reteplase‐loaded NC (NC(ret)) were incubated with pre‐formed plasma clots and the results indicated that the NC formation did not compromise the thrombolytic function of reteplase (Panel B). In the pulmonary embolism model, free reteplase or NC(ret) was injected 10 min after 125I‐labeled microemboli. Blood and organs were collected 1 hr‐post injection of microemboli to study the retention of clot in the lung after the treatment. Our results showed that the reteplase‐loaded NC significantly reduced the clot retention in the lung (Panel C). All together, we have developed NC containing neuroprotective agent that maintain the function of thrombolytic drug. Future studies will be focused on evaluating the neuroprotective properties of the NC, relative to free drug.Support or Funding InformationNIH (RO1 HL128398‐02 and RO1 HL 143806‐01), Cardiovascular Institute of Philadelphia (400‐4119‐2)Characteristics of Reteplase‐Containing Nanocarriers. A: Blood pharmacokinetics of free reteplase (ret) and NC‐encapsulated reteplase (NC(ret)). Comparisons by students t‐test. B: In vitro fibrinolytic activity of ret and NC(ret). C: Lysis of pulmonary emboli following injection of ret and NC(ret). Comparisons by 1‐way ANOVA with Dunnett's test. * denotes p&lt;0.05, ** p&lt;0.01, *** p&lt;0.001.Figure 1

Usefulness of predictive models of pulmonary embolism

BackgroundFaced with the suspicion of pulmonary embolism (PE), the guidelines recommend the use of clinical probability scales, measurement of D-dimer and, in certain cases, confirmation by pulmonary angiography by computed tomography (CTPA) or scintigraphy. Recently, it has been proposed to adjust the D-dimer according to age or use simpler scales (YEARS algorithm) for a better selection of patients. ObjectiveTo define the degree of application of the guidelines in our population and compare sensitivity, specificity and positive and negative predictive values of the different diagnostic models: standard model (Wells 2 categories+D-dimer), model adjusted for age (Wells 2 categories+D-dimer adjusted for age), YEARS algorithm. Material and methodsA retrospective study of all patients who underwent APTC at our centre for the diagnosis of PE over one year. ResultsOf 618 cases (85.4% of initial APTC), 544 patients were included. A total of 113 EPs were diagnosed (20.8%). The degree of application of the standard model was very high (90.1%) and proved to have the best sensitivity and negative predictive value ratio (sensitivity=1.0, negative predictive value=1.0). The new models could reduce the number of scans (17, 3.2% model adjusted for age and 48, 8.8% model YEARS) with a risk of false negatives (2 PE [1.8%] undiagnosed respectively). ConclusionsThe current diagnostic models for PE lead to a large number of unnecessary explorations. The new models could reduce the number of APTC although with a minimum risk of false negatives.

Right ventricular speckle tracking strain echocardiography in patients with acute pulmonary embolism.

Right atrial (RA) and right ventricular (RV) parameters assessed by traditional echocardiography lack sensitivity to identify pulmonary embolism (PE). We sought to determine if alterations in RV free wall longitudinal strain (FWS) would be present in PE patients and improve evaluation. This retrospective study comprised of 84 consecutive PE patients from 2 centres, with adequate transthoracic echocardiography (TTE) images for RV FWS analysis. PE patients were compared to 66 healthy controls. Compared to controls, PE patients had increased RV parasternal long-axis diameter (RVPLAX) (33.4 ± 5.8 mm vs 39.9 ± 4.1 mm) and RA area (17.4 ± 5.6 cm2 vs 14.5 ± 3.1 cm2) (p < 0.001 for both). RV function was reduced in PE patients (RV fractional area change 31.1 ± 13.2% vs 41.7 ± 9.1%, TAPSE 17.0 ± 4.5 vs 21.3 ± 2.2 mm; p < 0.001 for both). RV FWS was reduced in PE patients (-14.4 ± 7.2% vs - 26.0 ± 4.4%, p < 0.001). RV FWS was the best discriminator for PE (AUC 0.912). In comparative multiple logistic regression models for PE, the model which included traditional measures of RV size and function and RV FWS, produced a powerful classifier (AUC 0.966, SE 0.013) with significantly better performance (p < 0.022) than the model without RV FWS (AUC 0.921, SE 0.024). RV FWS is a discriminator of PE patients; addition of RV FWS to existing parameters of RV size and function, significantly improves sensitivity and specificity for diagnosis of PE, and may play a role in diagnosis and guiding therapy. Validation in other PE groups is required to confirm these observations and its prognostic value needs evaluation.

Predictive Model for Pulmonary Embolism in Patients with Deep Vein Thrombosis

To develop and verify a risk predictive model/scoring system for pulmonary embolism (PE) among hospitalized patients with deep venous thrombosis of the lower extremities (LDVT). 776 patients with LDVT were enrolled in a case-control study between January 2016 and June 2017 from the Vascular Surgery Department of Shanxi Dayi Hospital, China. They were randomly divided into development (543 patients, 70%) and validation (233 patients, 30%) databases. Based on the results of pulmonary computed tomography arteriography, patients were divided into 2 categories; those with PE were designated as the case group, whereas those without comprised the controls. A logistic regression model and scoring system for PE in patients with LDVT was established in the development database and verified in the validation database. Scoring system (Shanxi Dayi Hospital score [SDH score]) was tabulated as follows: right lower extremity or bilateral lower extremities, 1; surgery or immobilization, 1; malignant tumor, 1; history of venous thromboembolism (VTE), 2; D-dimer >1,000ng/mL, 2; and unprovoked, 2. Calibration and discrimination of the model were assessed by the Hosmer-Lemeshow goodness of fit test and the area under the receiver operating characteristic curve (AUC). Wells score, the Revised Geneva score, and the SDH score for predictive value of PE by AUC in the validation database were compared. 776 patients with LDVT were divided into 2 risk categories based on the scores from the risk model as follows: PE unlikely (score <3) and PE likely (score ≥3). Sensitivity, specificity, and crude agreement of the SDH score in the development database were 76.39%, 55.89%, and 61.33%, respectively. In the validation database, the logistic regression model showed good calibration and discriminative power. The Hosmer-Lemeshow goodness of fit test P value was >0.05, and the AUC was 0.705 (95% CI: 0.634-0.776, P<0.001). The SDH score also showed good discriminative power, and the AUC was 0.702 (95% CI: 0.631-0.774, P<0.001). Sensitivity, specificity, and crude agreement of the SDH score in the validation database were 67.61%, 61.73%, and 63.52%, respectively. AUC for the Wells score and the Revised Geneva score was 0.611 (95% CI: 0.533-0.688, P=0.007) and 0.585 (95% CI: 0.503-0.666, P=0.040), respectively. Difference of the AUC was not statistically significant between the Wells score and the SDH score (0.611 vs. 0.702, P=0.059) but was so between the Revised Geneva score and the SDH score (0.585 vs. 0.702, P=0.016). Sensitivity of the Wells score, Revised Geneva score, and the SDH score (64.79%, 67.61% vs. 67.61%) was not statistically significant. However, the specificity of the Wells score and Revised Geneva score was significantly lower than that of the SDH score (48.77%, 39.51% vs. 61.73%). Our logistic regression model and the SDH score based on 7 risk factors as right lower extremity, bilateral lower extremities, unprovoked, surgery or immobilization, malignant tumor, history of VTE, and D-dimer>1,000ng/mL showed good calibration and discriminative power for the assessment of PE risk in patients with LDVT. The SDH score is more specific for PE prediction in the Chinese population, compared with the Wells score and the Revised Geneva score.

Pulmonary vasodilation in acute pulmonary embolism - a systematic review.

Acute pulmonary embolism is the third most common cause of cardiovascular death. Pulmonary embolism increases right ventricular afterload, which causes right ventricular failure, circulatory collapse and death. Most treatments focus on removal of the mechanical obstruction caused by the embolism, but pulmonary vasoconstriction is a significant contributor to the increased right ventricular afterload and is often left untreated. Pulmonary thromboembolism causes mechanical obstruction of the pulmonary vasculature coupled with a complex interaction between humoral factors from the activated platelets, endothelial effects, reflexes and hypoxia to cause pulmonary vasoconstriction that worsens right ventricular afterload. Vasoconstrictors include serotonin, thromboxane, prostaglandins and endothelins, counterbalanced by vasodilators such as nitric oxide and prostacyclins. Exogenous administration of pulmonary vasodilators in acute pulmonary embolism seems attractive but all come with a risk of systemic vasodilation or worsening of pulmonary ventilation-perfusion mismatch. In animal models of acute pulmonary embolism, modulators of the nitric oxide-cyclic guanosine monophosphate-protein kinase G pathway, endothelin pathway and prostaglandin pathway have been investigated. But only a small number of clinical case reports and prospective clinical trials exist. The aim of this review is to give an overview of the causes of pulmonary embolism-induced pulmonary vasoconstriction and of experimental and human investigations of pulmonary vasodilation in acute pulmonary embolism.

A comparative analysis of the diagnostic performances of four clinical probability models for acute pulmonary embolism in a sub-Saharan African population: a cross-sectional study

BackgroundThe diagnosis of acute pulmonary embolism (PE) is one of the most challenging in emergency settings where prompt and accurate decisions need to be taken for life-saving purposes. Here, the assessment of the clinical probability of PE is a paramount step in its diagnosis. Although clinical probability models (CPM) for PE are routinely used in emergency departments (EDs) of low-resource settings, few studies have cited their diagnostic performances in sub-Saharan Africa (SSA). We aimed to comparatively assess the accuracy of four CPM in the diagnosis of acute PE in sub-Saharan Africans.MethodsWe carried out a cross-sectional study to compare the sensitivity, specificity, positive and negative predictive values and accuracy of four CPM namely; the Wells, simplified Wells, revised Geneva and the simplified revised Geneva (SRG) Scores to computed tomography pulmonary angiography (CTPA) in all adults patients with suspected PE admitted to the EDs of the Gynaeco-obstetric and Paediatric Hospital of Yaoundé and the Yaoundé Central Hospital in Cameroon between January 1, 2017 and April 30, 2018.ResultsIn total, we enrolled 30 patients with clinical suspicion of acute PE. PE was confirmed on CTPA in 16 (53.3%) cases. Their mean age was 53.7 ± 15.5 years and 36.7% were males. All four scores had a diagnostic performance superior to 50% in all criteria assessed. The simplified Wells score had the highest sensitivity (62.5%) followed by the Wells score (56.3%). The SRG score had the highest specificity (71.4%). The score with highest PPV was the SRG score (66.7%) and that with the highest NPV was the Wells score (56.3%). Overall the models with the highest accuracies were the Wells and SRG scores (60% for each).ConclusionAll CPM had a suboptimal diagnostic performance, perhaps highlighting the need of a more optimal CPM for acute PE in SSA. However, the Wells and the SRG scores appeared to be most accurate than the other two scores in the ED. Hence, both or either of them may be used in first intention to predict PE and guide which ED patients should undergo further investigations in an emergency SSA setting.

Engineered Nanoplatelets for Targeted Delivery of Plasminogen Activators to Reverse Thrombus in Multiple Mouse Thrombosis Models.

Rapid cut-off of blood supply in diseases involving thrombosis is a major cause of morbidity and mortality worldwide. However, the current thrombolysis strategies offer limited results due to the therapeutics' short half-lives, low targeting ability, and unexpected bleeding complications. Inspired by the innate roles of platelets in hemostasis and pathological thrombus, platelet membrane-camouflaged polymeric nanoparticles (nanoplatelets) are developed for targeting delivery of the thrombolytic drug, recombinant tissue plasminogen activator (rt-PA), to local thrombus sites. The tailor-designed nanoplatelets efficiently accumulate at the thrombi in pulmonary embolism and mesenteric arterial thrombosis model mice, eliciting a significantly enhanced thrombolysis activity compared to free rt-PA. In addition, the nanoplatelets exhibit improved therapeutic efficacy over free rt-PA in an ischemic stroke model. Analysis of in vivo coagulation indicators suggests the nanoplatelets might possess a low risk of bleeding complications. The hybrid biomimetic nanoplatelets described offer a promising solution to improve the efficacy and reduce the bleeding risk of thrombolytic therapy in a broad spectrum of thrombosis diseases.

Utilidad de los modelos predictivos de embolia pulmonar

BackgroundFaced with the suspicion of pulmonary embolism (PE), the guidelines recommend the use of clinical probability scales, measurement of D-dimer and, in certain cases, confirmation by pulmonary angiography by computed tomography (CTPA) or scintigraphy. Recently, it has been proposed to adjust the D-dimer according to age or use simpler scales (YEARS algorithm) for a better selection of patients. ObjectiveTo define the degree of application of the guidelines in our population and compare sensitivity, specificity and positive and negative predictive values of the different diagnostic models: Standard model (Wells 2 categories+D-dimer), Model adjusted for age (Wells 2 categories+D-dimer adjusted for age), YEARS algorithm. Material and methodsA retrospective study of all patients who underwent APTC at our centre for the diagnosis of PE over one year. ResultsOf 618 cases (85.4% of initial APTC), 544 patients were included. A total of 113 EPs were diagnosed (20.8%). The degree of application of the standard model was very high (90.1%) and proved to have the best sensitivity and negative predictive value ratio (sensitivity=1.0, negative predictive value=1.0). The new models could reduce the number of scans (17, 3.2% model adjusted for age and 48, 8.8% model YEARS) with a risk of false negatives (2 PE [1.8%] undiagnosed respectively). ConclusionsThe current diagnostic models for PE lead to a large number of unnecessary explorations. The new models could reduce the number of APTC although with a minimum risk of false negatives.

Catestatin prevents endothelial inflammation and promotes thrombus resolution in acute pulmonary embolism in mice.

Catestatin (CTS), a catecholamine-release inhibitory peptide, exerts pleiotropic cardiac protective effects. Pulmonary embolism caused by deep vein thrombosis involving vascular dysfunction. The present study aims to investigate the effects of CTS on thrombus formation that may inhibit the development of pulmonary embolism and its potential pathway. Acute pulmonary embolism (APE) model was developed as an in vivo model. The effects of CTS on mice with APE were examined. Human pulmonary artery endothelial cells (HPAECs) were pretreated with CTS before thrombin stimulation, and endothelial inflammation and underlying mechanisms were evaluated in vitro. That plasma CTS level was decreased in APE mice, while the number of platelets was significantly increased. The decreased circulating CTS level negatively associated with the number of platelets. CTS administration increased the survival rate of APE mice and protected against microvascular thrombosis in lung. APE-induced the increase in platelets number and plasma von Willebrand factor (VWF) were inhibited by CTS. Platelets from CTS-treated APE mice showed impaired agonist-induced platelets aggregation and spreading. CTS also ameliorated APE-induced the systemic inflammatory response. In in vivo study, thrombin-induced the increase in inflammation, TLR-4 expression and p38 phosphorylation were abrogated by CTS in HPAECs. Furthermore, TLR-4 overexpression inhibited the effect of CTS on VWF release and inflammation in HPAECs. Collectively, CTS increases thrombus resolution by attenuating endothelial inflammation at partially via inhibiting TLR-4-p38 pathway. The present study may provide a novel approach for anti-thrombosis.

Warm retrograde perfusion can remove more fat from lung grafts with fat embolism in a porcine model.

In lung transplantation, unexpected pulmonary emboli, including thrombi and fat, have been observed with high probability and are associated with potential primary graft dysfunction. We evaluated a new perfusion method using warm retrograde flushing that removes more fat than conventional cold retrograde flushing. We developed a novel porcine donor model for pulmonary fat embolism by administering autologous fat in the left pulmonary artery. The left pulmonary artery and the left superior and inferior pulmonary veins were cannulated for flushing and collecting these solutions. After flushing, the left lung was reperfused under observation for 3h. Two groups underwent warm and cold additional retrograde flush (WS; warm solution group, CS; cold solution group). The fat removal rate in the antegrade flush was equal in both groups (3.0 ± 0.6% vs 3.0 ± 0.4%, p = 0.46); however, the rate was significantly greater in the WS group in retrograde flush (25.2 ± 3.2% vs 8.0 ± 1.4%, p = 0.01). Histology with Oil Red O staining and its software analysis showed more residual fat in the CS group (0.12 ± 0.01% vs 0.38 ± 0.07%, p = 0.01). There was no significant difference in the pulmonary function and hemodynamics during the 3-h period after reperfusion. Warm retrograde perfusion can remove more fat from lung grafts with fat embolism in a porcine donor model.

A PROPOSED NEW ECG-DERIVED SCORING INDEX TO DIAGNOSE MASSIVE OR SUBMASSIVE PULMONARY EMBOLISM

SESSION TITLE: Monday Abstract Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: 10/21/2019 02:30 PM - 03:15 PM PURPOSE: To test the hypothesis that a new ECG score based on age-predicted heart rate, axis and T wave inversion in V3 has a predictive model for massive or submassive pulmonary embolism (PE) than the other well-established ECG based Daniel’s scoring scale. METHODS: Two readers blindly interpreted the ECGs from 33 consecutive patients with suspected PE who underwent chest CT Angiogram (CTA). Out of which 16 patients were found to have PE on CTA. Data were compared between patients with and without PE. The ECG parameters analyzed included variables based on heart rate, frontal plane axis, McGinn White morphology, QRS duration, the presence of bundle branch block (BBB), R wave progression and T wave changes. The Daniel score, a 21-point ECG derived score shown to correlate with the pulmonary artery pressures in angiographically confirmed PE, was assessed for comparison. RESULTS: Examination of the data using a newly proposed index showed that the age-predicted heart rate of > 50% was the most frequently observed ECG abnormality in patients with PE. An ECG score > 3 was associated with a 100% specificity and 66% sensitivity in the diagnosis of PE. It is important to note that our ECG derived scoring system successfully predicts pulmonary hypertension in the setting of massive or submassive PE more so that well established Daniel’s score (4 more patients that would have been the case with Daniel’s score which picks up only 3, 7 vs. 3). A detailed comparison of our score vs. Daniel’s score is given in figure 1. As per Daniel’s Index, the score increases with severity of pulmonary hypertension from PE, and a score > or = 10 is highly suggestive of severe pulmonary hypertension from PE. Our scoring system suggests that a score of > or = 3 is highly suggestive of severe pulmonary hypertension from PE. CONCLUSIONS: A new ECG based scoring index may be a useful diagnostic tool in the evaluation for PE with better predictability than the well-established Daniel’s score. A prospective study may be indicated to validate these findings further. CLINICAL IMPLICATIONS: A new ECG based score with better co-relation would help to make accurate and timely clinical decisions DISCLOSURES: no disclosure on file for AHMED ABDULBAKI; No relevant relationships by MUHAMMAD ADEEL, source=Web Response No relevant relationships by Craig McPherson, source=Web Response no disclosure on file for EROL NARGILECI

Impaired Glycoprotein VI-Mediated Signaling and Platelet Functional Responses in CD45 Knockout Mice.

CD45 is a receptor protein tyrosine phosphatase present on the surface of all hematopoietic cells except for erythrocytes and platelets. Proteomics studies, however, have demonstrated the presence of a CD45 c-terminal catalytic peptide in platelets. Therefore, we investigated the functional role of this truncated isoform of CD45 in platelets, which contains the c-terminal catalytic domain but lacks the extracellular region. We used an antibody specific to the c-terminus of CD45 to confirm the presence of a truncated CD45 isoform in platelets. We also examined ex vivo and in vivo platelet function using CD45 knockout (KO) mice. Aggregation and secretion mediated by the glycoprotein VI (GPVI) receptor was impaired in CD45 KO platelets. Consequently, CD45 KO mice had impaired hemostasis indicated by increased tail bleeding times. Also, using a model of pulmonary embolism we showed that CD45 KO mice had defective in vivo thrombus formation. Next, we investigated whether or not the truncated isoform of CD45 had a role in GPVI signaling. The full-length isoform of CD45 is known to regulate Src family kinase (SFK) activation in lymphocytes. We find a similar role for the truncated isoform of CD45 in platelets. SFK activation was impaired downstream of the GPVI receptor in the CD45 KO murine platelets. Consequently, Syk, PLCγ2, and pleckstrin phosphorylations were also impaired in CD45 KO murine platelets. We conclude that the truncated CD45 isoform regulates GPVI-mediated signaling and platelet functional responses by regulating SFK activation.

Potential role of sympathetic activity on the pathogenesis of massive pulmonary embolism with circulatory shock in rabbits

BackgroundWe recently showed that intravenous sodium nitroprusside treatment (SNP) could relieve the pulmonary vasospasm of pulmonary embolism (PE) and non-pulmonary embolism (non-PE) regions in a rabbit massive pulmonary embolism (MPE) model associated with shock. The present study explored the potential role of cardiopulmonary sympathetic activity on the pathogenesis and the impact of vasodilators on cardiopulmonary sympathetic activity in this model.MethodsRabbits were randomly divided into sham operation group (S group, n = 8), model group (M, equal volume of saline intravenously, n = 11), SNP group (3.5 μg/kg/min intravenously, n = 10) and diltiazem group (DLZ, 6.0 μg/kg/min intravenously, n = 10).ResultsMPE resulted in reduced mean arterial pressure and increased mean pulmonary arterial pressure as well as reduced PaO2 in the M, SNP and DLZ groups. Tyrosine hydroxylase (TH), neuropeptide Y (NPY) and endothelin-1 (ET-1) expression levels were significantly increased, while nitric oxide (NO) levels were reduced in both PE and non-PE regions in the M group. Both SNP and DLZ decreased mean pulmonary arterial pressure, reversed shock status, downregulated the expression of TH, NPY and ET-1, and increased NO levels in PE and non-PE regions.ConclusionPresent results indicate that upregulation of the sympathetic medium transmitters TH and NPY in whole lung tissues serves one of the pathological features of MPE. The vasodilators SNP and DLZ could relieve pulmonary vasospasm in both embolization and non-embolization regions and reverse circulatory shock, thereby indirectly downregulating the sympathetic activation of the whole lung tissues and breaking a vicious cycle related to sympathetic activation in this model.

Riociguat, sildenafil and inhaled nitric oxide reduces pulmonary vascular resistance and improves right ventricular function in a porcine model of acute pulmonary embolism.

Pulmonary vasodilators as add-on to current treatment strategies in acute pulmonary embolism may improve right ventricular unloading and hence improve patient outcome. We aimed to investigate whether stimulation of the nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) pathway with riociguat, sildenafil or inhaled NO causes pulmonary vasodilation and improves right ventricular function in a porcine model of acute intermediate risk pulmonary embolism. Two large autologous blood clots were administered to the pulmonary circulation of 28 pigs (60 kg). Animals were randomized to four increasing, clinically equivalent doses of riociguat (n=6), sildenafil (n=6), inhaled NO (n=6) or vehicle (n=6). Sham animals (n=4) did not receive pulmonary embolism or treatment. Haemodynamic responses were evaluated at baseline, after pulmonary embolism and after each dose using invasive pressure measurements, transoesophageal echocardiography, respiratory parameters and blood analysis. Pulmonary embolism caused a three-fold increase in pulmonary vascular resistance compared with baseline (pulmonary embolism: 352±29 vs. baseline: 107±6 dynes, p<0.0001). All treatments lowered pulmonary vascular resistance compared with vehicle (riociguat: -158±35, sildenafil: -224±35, inhaled NO: -156±35 dynes, p<0.0001). Sildenafil, but neither inhaled NO nor riociguat, caused a decrease in systemic vascular resistance (sildenafil 678±41 vs. vehicle 1081±93 dynes, p=0.02) and increased cardiac output (sildenafil 8.8±0.8 vs. vehicle: 5.9±0.2 L/min, p<0.001). Systemic blood pressure was unaltered in all treatment groups. Stimulation of the NO-sGC-cGMP pathway by riociguat, sildenafil and inhaled NO reduces pulmonary vascular resistance in a porcine model of acute pulmonary embolism without lowering systemic blood pressure.

Glucose Metabolism Is Required for Platelet Hyperactivation in a Murine Model of Type 1 Diabetes.

Patients with type 1 diabetes mellitus (T1DM) have increased thrombosis and platelet activation. The mechanisms for platelet hyperactivation in diabetes are incompletely understood. T1DM is accompanied by hyperglycemia, dyslipidemia, and increased inflammation in addition to an altered hormonal milieu. In vitro analysis of platelets revealed that normal glucose reduces platelet activation whereas hyperglycemic conditions increase platelet activation. We therefore hypothesized that hyperglycemia increases platelet glucose utilization, which increases platelet activation to promote thrombosis. Glucose uptake and glycolysis were increased in platelets isolated from mice given streptozotocin (STZ) to induce T1DM in concert with induction of GLUT3. Platelets from STZ-induced diabetic mice exhibited increased activation after administration of protease-activated receptor 4 peptide and convulxin. In contrast, platelets isolated from GLUT1 and GLUT3 double-knockout (DKO) mice, which lack the ability to use glucose, failed to increase activation in hyperglycemic mice. Diabetic mice displayed decreased survival in a collagen/epinephrine-induced pulmonary embolism model of in vivo platelet activation relative to nondiabetic controls. Survival after pulmonary embolism was increased in diabetic DKO mice relative to nondiabetic controls. These data reveal that increased platelet glucose metabolism in vivo contributes to increased platelet activation and thrombosis in a model of T1DM.

Detection of Pulmonary Embolism Based on Reduced Changes in Radiographic Lung Density During Cardiac Beating Using Dynamic Flat-panel Detector: An Animal-based Study

To assess the capacity of dynamic flat-panel detector imaging without the use of contrast media to detect pulmonary embolism (PE) based on temporal changes in radiographic lung density during cardiac beating. Sequential chest radiographs of six pigs were acquired using a dynamic flat-panel detector system. A porcine model of PE was developed, and temporal changes in pixel values in the imaged lungs were analyzed during a whole cardiac cycle. Mean differences in temporal changes in pixel values between affected and unaffected lobes were assessed using the paired t test. To facilitate visual evaluation, temporal changes in pixel values were depicted using a colorimetric scale and were compared to the findings of contrast-enhanced images. Affected lobes exhibited a mean reduction of 49.6% in temporal changes in pixel values compared to unaffected lobes within the same animals, and a mean reduction of 41.3% compared to that before vessel blockage in the same lobe. All unaffected lobes exhibited significantly-increased changes in pixel values after vessel blockage (p < 0.01). In all PE models, there were color-deficient areas with shapes and locations that matched well with the perfusion defects confirmed in the corresponding contrast-enhanced images. Dynamic chest radiography enables the detection of perfusion defects in the lobe unit based on temporal changes in image density, even without the use of contrast media. Quantification and visualization techniques provide a better understanding of the circulation-induced changes depicted in dynamic chest radiographs.

Treatment with new organic nitrites in pulmonary hypertension of acute experimental pulmonary embolism.

Acute pulmonary embolism may cause right heart failure due to increased pulmonary vascular resistance and arterial hypoxemia. Effective vasodilator therapy of the pulmonary hypertension is highly needed. Therefore, we investigated the effects of a newly developed effective pulmonary vasodilator, the organic mononitrites of 1,2‐propanediol (PDNO), in a rabbit model of acute pulmonary embolism. In anesthetized and ventilated rabbits, systemic and pulmonary hemodynamics, exhaled nitric oxide (NO), plasma nitrite concentration, and blood gases were monitored. First, dose–response experiments with intravenous and left heart ventricle infusions of PDNO and inorganic nitrite were done in naive animals and in pulmonary hypertension induced by a thromboxane A2 analogue. Second, acute pulmonary embolism was induced and either PDNO or placebo were administered intravenously within 20 minutes and evaluated within 1 hour after pulmonary embolization. PDNO intravenously, in contrast to inorganic nitrite intravenously, increased exhaled NO and counteracted pulmonary hypertension and vasodilated the systemic circulation, dose‐dependently, thereby showing efficient NO donation. Pulmonary embolization induced pulmonary hypertension and gas exchange disturbances. PDNO significantly decreased and normalized pulmonary vascular resistance and the right ventricle rate‐pressure product, without causing tolerance, with no significant side effects on the systemic circulation, nor on blood‐gas values or on methemoglobin formation. In conclusion, PDNO is a NO donor and an efficient vasodilator in the pulmonary circulation. Treatment with this or similar organic nitrites intravenously may be a future option to avoid right heart failure in life‐threatening acute pulmonary embolism.