A randomised trial on modulating endogenous fibrinolysis in patients with acute coronary syndrome VaLiDate-R

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): This study is funded by Bayer PLC, 400 South Oak Way, Green Park, Reading, Berkshire, RG2 6AD.

Background

Impaired endogenous fibrinolysis is novel biomarker that can identify patients with ACS at increased cardiovascular risk. The addition of very low dose rivaroxaban (VLDR) to dual antiplatelet therapy has been shown to reduce cardiovascular events but at a cost of increased bleeding and is therefore not suitable for all-comers. Targeted additional pharmacotherapy with VLDR to improve endogenous fibrinolysis may improve outcomes in high-risk patients, whilst avoiding unnecessary bleeding in low-risk individuals.

Methods and Results

The VaLiDate-R study is an investigator-initiated, randomised, open-label, single centre trial comparing the effect of 3 antithrombotic regimens on endogenous fibrinolysis in 150 patients with ACS. Subjects whose screening blood test shows impaired fibrinolytic status (lysis time >2000s), will be randomised to one of 3 treatment arms in a 1:1:1 ratio: clopidogrel 75 mg daily (Group 1); clopidogrel 75 mg daily plus rivaroxaban 2.5 mg twice daily (Group 2); ticagrelor 90 mg twice daily (Group 3), in addition to aspirin 75 mg daily. Rivaroxaban will be given for 30 days. Fibrinolytic status will be assessed during admission and at 2, 4 and 8 weeks. The primary outcome measure is the change in fibrinolysis time from admission to 4 weeks follow-up, using the Global Thrombosis Test.

Conclusion

If VLDR can improve endogenous fibrinolysis in ACS, future large-scale studies would be required to assess whether targeted use of VLDR in patients with ACS and impaired fibrinolysis can translate into improved clinical outcomes, with reduction in major adverse cardiovascular events in this high-risk cohort.

Relationship between coronary stenosis severity and high shear thrombosis assessment in vitro

Funding Acknowledgements

Type of funding sources: None.

Among stable outpatients presenting with suspected coronary artery disease, the presence and extent of coronary artery calcification (CAC) and the severity of disease on CT coronary angiography (CTCA) has been shown to be predictive of future major adverse cardiovascular events (MACE) including myocardial infarction (MI). In stable patients, high on-treatment platelet reactivity has also been shown to relate to an increased risk of MACE including MI. The relationship between thrombotic markers in peripheral blood and the extent of CAC and coronary disease severity, is unknown.

It was the aim of this pilot study to assess the relationship between thrombotic status and the extent of CAC and severity of coronary stenosis on CT.

Subjects with suspected coronary disease undergoing CTCA and CAC were invited to participate in this observational study. Venous blood was obtained to assess platelet reactivity to high shear (occlusion time, OT) and endogenous fibrinolysis (lysis time, LT) using the Global Thrombosis Test, and related to CAC and to maximum stenosis in any main coronary artery on CTCA.

Eighty patients were recruited, specifically 20 patients from each CAC quartile (adjusted for age, gender and ethnicity), 58% were male, aged 61±10 y. Groups were matched for age, sex, diabetes, and hs-CRP. The median Agatson CAC score was 27 [interquartile range (IQR) 0.5-125.5] and in each quartile (Q) as follows: Q1 0[0-0]; Q2 17[6-51.5]; Q3 70.25[26-111.5] and Q4 192.6[70.5-413.5].

Patients were divided into 4 groups according to maximal severity of coronary stenosis on CTCA (0%, 1-49%, 50-69%, >70%). With increasing stenosis severity, we found patients exhibited less efficient endogenous fibrinolysis (longer LT) (LT 1728s[1512-2102] vs. 2028s[1687-2288] vs. 1728s[1634-1927] vs. 2524s[2425-2623] respectively, p=0.040) whilst platelet reactivity appeared unrelated to severity of coronary stenosis (438s[341-479] vs. 415s[357-484] vs. 444s[384-504] vs. 391s[357-425], p=0.907).

Platelet reactivity (OT 430s[339-477] vs. 458s[391-499] vs. 409s[351-488] vs. 413s[354-496], p=0.76) and spontaneous fibrinolysis (LT 1754s[1548-2162] vs. 1809s[1635-2291] vs. 2111s[1838-2312] vs. 1846s[1666-2090], p=0.253) were similar between the quartiles. Furthermore, there was no difference in platelet reactivity (430s[339-477] vs. 413s[354-496], p=0.830) or spontaneous fibrinolysis (1754s[1548-2162] vs. 1846s[1666-2090], p=0.561) when comparing patients within the lowest and the highest quartiles of CAC.

The severity of maximal coronary stenosis, but not the extent of CAC, is related to the effectiveness of spontaneous fibrinolysis at high shear in vitro, with patients with more severe stenoses exhibiting less efficient fibrinolysis. Further studies are required to investigate whether the extent of in vivo coronary shear (related to plaque morphology) can be reflected by the assessment of thrombosis and fibrinolysis in response to high shear in vitro.

Diurnal variation in thrombotic and fibrinolytic status in healthy volunteers

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): East and North Hertfordshire NHS Trust

Background

Previous studies assessing markers of fibrinolysis in healthy volunteers and patients with coronary artery disease (CAD) indicate circadian variation, primarily attributable to changes in plasminogen activator inhibitor-1 (PAI-1) concentrations, the main inhibitor of fibrinolysis, peaking between midnight and 06:00 hrs, with a nadir at 01:00 hrs. Whether the elevated PAI-1 translates into a global impairment of fibrinolysis, is not known.

Purpose

It was our aim to assess diurnal variation in global fibrinolytic activity in healthy subjects.

Methods

A single centre, prospective, observational study was conducted in healthy volunteers. Blood samples were obtained at two different time points on the same day, with a minimum inter-sample interval of 8 hours and a maximum of 12 hours. Venous blood was assessed to determine global thrombotic and fibrinolytic status in native whole blood status using the automated, point-of-care Global Thrombosis Test (GTT). This utilises non-anticoagulated blood to assess the time taken to form an occlusive thrombus under high shear (occlusion time) and the time taken for spontaneous restart of flow as a measure of endogenous fibrinolysis (lysis time).

Results

A total of 25 healthy volunteers (36% male), aged 34±12 y were included. All were non-smokers with a BMI of 25 (22.3 – 27.5) kg/m². The median interval between samples was 8:05 [hh:mm] (IQR 8:30 – 9:10). Occlusion time was similar in the morning and evening samples (median 451s [389 – 590] vs. 524s [428 – 597], p=0.207). Lysis time was also similar between morning and evening (median 1792s [1622 -2097] vs. 1726s [IQR 1517 – 1891], p=0.265).

Conclusion

Compared to the known circadian variation of thrombotic and fibrinolytic activity attributable to PAI-1, global thrombotic and fibrinolytic status do not appear to exhibit diurnal variation. Further studies are needed to assess how this correlates to t-PA and PAI-1 levels and the status in patients with cardiovascular disease.

Diurnal Variation in thrombolytic status in patients presenting with STEMI

Funding Acknowledgements

Type of funding sources: None.

Background

Prior studies mainly in healthy volunteers and patients with stable coronary artery disease (CAD) indicate circadian variation in spontaneous fibrinolytic activity. This is predominantly attributable to changes plasminogen activator inhibitor-1 (PAI-1) levels peaking between midnight and 06:00 hr, with a nadir at 18:00 hr. Whether circadian variation in spontaneous fibrinolysis exists amongst patients with ST-elevation myocardial infarction (STEMI) is unknown.

Purpose

It was our aim to assess circadian variation in fibrinolytic status in the acute setting in patients presenting with STEMI.

Methods

A prospective, observational study was conducted in patients presenting with STEMI for primary percutaneous coronary intervention (PPCI). Blood was tested on arrival pre-PPCI, after aspirin and P2Y12 inhibitor administration, but before any anticoagulant or antithrombotic agent administration in the cardiac cath lab. Venous blood was assessed to determine endogenous fibrinolysis using the Global Thrombosis Test, which utilises non-anticoagulated blood to assess the formation of an occlusive thrombus under high shear and the time taken for spontaneous restart of flow as a measure of endogenous fibrinolysis (lysis time, LT).

Results

A total of 527 patients were included, aged 64±13 years and 78% were male. 304 (58%) patients presented within working hours (08:00-17:00) with peak presentation between 11:00-12:00 and trough between 03:00 to 05:00 hrs.

Lysis time was not related to time of presentation. Time of presentation was divided into 4 groups (A 00:00-05:59, B 06:00-11:59, C 12:00-17:59, D 18:00-23:59 hrs). There was no significant difference in LT between patients presenting at the 4 timepoints (median 1362s [interquartile range IQR 1077-1808] vs 1503s [1182-2056] vs 1440s [1164-1998] vs. 1420s [1125-1820], respectively, p=0.340). When comparing Group A to C, the LT was not significantly different (1362s [1077-1808] vs. 1440 [1164-1998], p=0.413). The presentation time of patients with impaired endogenous fibrinolysis (LT>3000 sec) did not differ significantly from patients with normal endogenous fibrinolysis. The hourly variation was similar in diabetics and non-diabetics, but the variation in lysis time appeared blunted in patients taking long term aspirin prior to presentation compared to non-aspirin takers.

Conclusion

In contrast to the known circadian variation in fibrinolysis in normal volunteers, and stable CAD, in our large cohort of STEMI patients, there appears to be no relationship between time of presentation/onset of STEMI and the effectiveness spontaneous fibrinolysis. This is reflected in our observation, supported by most contemporary studies, that peak time of STEMI presentation is during the late morning, and this does not relate to known circadian variation in fibrinolysis markers in CAD.

Does targeted temperature management increase the risk of stent thrombosis in survivors of out-of-hospital cardiac arrest? A single centre experience

Funding Acknowledgements

Type of funding sources: None.

Introduction

Acute Myocardial Infarction (AMI) complicated by out-of-hospital cardiac arrest (OCHA) carries a poor prognosis. Emergent angiography and primary percutaneous coronary intervention (PPCI) has been shown to improve survival, however some patients are left with significant neurological sequelae. Targeted Temperature Management (TTM) in randomised controlled trials has improved neurological status in survivors, however concerns have arisen from case series demonstrating a higher incidence of stent thrombosis. Reduced absorption of orally-administered P2Y12 inhibitor medication has been demonstrated in this cohort on the intensive care unit (ICU) and has been proposed to account for an observed increase in stent thrombosis.

Purpose

Our aim was to assess the relationship between stent thrombosis and TTM in patients with OHCA due to AMI and undergoing primary percutaneous coronary intervention (PPCI).

Methods

We conducted a single centre, retrospective analysis of consecutive patients admitted to the East and North Hertfordshire NHS Trust with an OHCA secondary to ST-elevation myocardial infarction and treated with PPCI.  All patients received aspirin loading and either enteral P2Y12 inhibitor loading (ticagrelor or clopidogrel) or intravenous (cangrelor) prior to or immediately after PPCI, according to clinician preference. Glycoprotein IIb/IIIa administration was determined by physician choice and documented. All patients were transferred to the ICU straight after PPCI, where some received TTM. Notes were reviewed to allow recording of demographic and procedural data, including post resuscitation care up to hospital discharge.

Results

A total of 92 patients were identified, 80% male and aged 62 +/-12.5 years. In addition to aspirin, patients were treated with P2Y12 inhibitors with 72.5% loaded with ticagrelor, 2.5% with clopidogrel and the remaining 25% with intravenous cangrelor. In addition, 49% of patients received periprocedural glycoprotein IIb/IIIa inhibitor.

TTM was initiated in 38 patients (41%) using surface pads. The average duration of TTM was 24 hours. No cases of stent thrombosis occurred. In-hospital all-cause mortality was 24%. The death rate was higher amongst those patients who were cooled, but this difference was not statistically significant (35% vs 17%, p = 0.08). Cangrelor use was significantly higher in the cooled cohort (43% vs. 8%, p < 0.001), but glycoprotein IIb/IIIa inhibitor use was similar between those receiving and not receiving TTM (38% vs. 57%, p = 0.088).

Conclusion

No definite stent thromboses were recorded in the 92 patients reviewed, suggesting that TTM does not increase the risk of stent thrombosis. Our conclusion is limited by the small sample size, and the heterogeneity in P2Y12 inhibitor use, particularly the higher use of cangrelor in the cooled cohort.

The Atrial Fibrillation Better Care (ABC) pathway in atrial fibrillation: a systematic review and meta-analysis of 285,000 patients

Funding Acknowledgements

Type of funding sources: None.

Background

The ‘Atrial Fibrillation Better Care’ (ABC) pathway has been recently proposed as a holistic approach for the comprehensive management of patients with Atrial Fibrillation (AF), standing on three main pillars: ‘A’ Avoid stroke (with Anticoagulants); ‘B’ Better symptom management; ‘C’ Cardiovascular and Comorbidity management. The ABC pathway is now recommended in several clinical guidelines, including the recent European Society of Cardiology (ESC) AF management guidelines. We performed a systematic review of the current evidence for use of the ABC pathway on clinical outcomes.

Methods

We performed a systematic review and meta-analysis according to PRISMA Guidelines. Pubmed and EMBASE were searched for studies reporting the prevalence of ABC pathway adherent management in AF patients, and its impact on clinical outcomes (all-cause death, cardiovascular death, stroke, and major bleeding). Metanalysis of odds ratio (OR) was performed with random-effect models; subgroup analysis and meta-regression were performed to account for heterogeneity; a CHA2DS2-VASc-stratified sensitivity analysis was also performed.

Results

Among 2862 records retrieved from the literature search, 8 studies were included. The pooled prevalence of ABC adherent management was 21% (95% confidence intervals (CI), 13-34%), with a high grade of heterogeneity; in a multivariable meta-regression model, adherence to each criteria of the ABC pathway explained most part of the heterogeneity (R2 = 98.9%). Patients treated according to the ABC pathway showed a lower risk of all-cause death (OR:0.42, 95%CI 0.31-0.56), cardiovascular death (OR:0.37, 95%CI 0.23-0.58), stroke (OR:0.55, 95%CI 0.37-0.82) and major bleeding (OR:0.69, 95%CI 0.51-0.94), with moderate heterogeneity. Meta-regressions showed that the increasing prevalence of diabetes mellitus, coronary artery disease, chronic heart failure and history of stroke were associated with a reduced effectiveness of the ABC pathway for all-cause and cardiovascular death; each comorbidity was able to explain a significant proportion of heterogeneity at univariate meta-regression. Conversely, longer follow-up time was associated with more effectiveness of the ABC pathway for all outcomes. Adherence to ABC pathway was associated with a progressively greater reduction of the all-cause death risk amongst patients with higher CHA2DS2-VASc scores; no difference in ABC pathway effectiveness was found across CHA2DS2-VASc strata for CV death and stroke occurrence.

Conclusions

Adherence to the ABC pathway was suboptimal, being adopted in 1 in every 5 patients. Adherence to the ABC pathway was associated with a reduction in the risk of major adverse outcomes. Our data supports extensive application of the ABC pathway for the management of AF. Abstract Figure.

Correlation between plasma clot properties, thrombin generation and whole blood fibrinolytic assays in patients presenting with STEMI

Background

Impaired endogenous fibrinolysis is a novel risk factor for recurrent adverse cardiovascular events in acute coronary syndrome (ACS) patients. This is independent of conventional cardiovascular risk factors and unaffected by dual antiplatelet therapy (DAPT). The mechanism underlying impaired endogenous fibrinolysis in ACS patients is currently unclear.

Aim

To identify the relationship between whole blood fibrinolysis, plasma fibrinolysis and thrombin generation in samples from STEMI patients.

Methods

In a large, prospective, observational study of 500 patients presenting with ST-segment elevation myocardial infarction (STEMI), blood samples were taken on arrival, after DAPT loading, and before administration of heparin or PPCI. Non-anticoagulated venous whole blood was analysed using the point-of-care Global Thrombosis Test, which assesses the time taken for occlusive thrombus formation under high shear (occlusion time, OT) and time required for spontaneous restart of flow as a measure of endogenous fibrinolysis (lysis time, LT). Patients were divided into 4 groups based on quartiles (Q) of whole blood LT (Q1: LT<1500s, Q2:1501–3000s, Q3:3001–4500s, Q4:>4500s). Plasma samples (20 per quartile) were examined in a thrombin generation assay using 1pM tissue factor to initiate and using a turbidity assay to determine the plasma clot lysis time (CLT).

Results

Clinical characteristics of patients were similar in the four groups. The whole blood LT in the 4 groups were Q1: 1194 (1125–1329) s, Q2: 1859 (1634–2157) s, Q3: 3638 (3252–3962) s, Q4: 6000 (5523–6000) s. As LT increased, there was a trend towards longer plasma CLT (50% CLT Q2: 88.5 [73.5–102] vs. Q4: 100 [85–128.5] min, p=0.088). As a continuous variable, there was no significant relationship between whole blood LT and plasma CLT, or between endogenous thrombin potential (ETP) and either whole blood LT or plasma CLT. There was a significant negative correlation between OT and velocity index (r=−0.425, p=0.0138), ETP (r=−0.519, p=0.002), peak thrombin generation (r=−0.390, p=0.0247) and a positive correlation with lag-time (r=0.427, p=0.013). There was positive correlation between CLT and white cell count (WCC, r=0.388, p=0.026), C-reactive protein (CRP, r=0.477, p=0.005) and maximum absorbance (MA, r=0.530, p=0.002). MA correlated with WCC (r=0.436, p=0.011) and platelet count (r=0.357, p=0.042). There was a negative correlation between OT and WCC (r=−0.537, p=0.001) and CRP (r=−0.381, p=0.029).

Conclusion

In patients with STEMI, increased platelet reactivity (shorter OT) correlated with increased thrombin generation (higher ETP, peak thrombin generation, velocity index and reduced lag time), demonstrating the key role of thrombin in occlusive thrombus formation. Fibrinolysis in whole blood was poorly related to plasma CLT or thrombin generation, suggesting that cellular components such as platelets, erythrocytes and neutrophil extracellular traps may significantly influence endogenous fibrinolysis.

Funding Acknowledgement

Type of funding source: None

P4744Patients with atrial fibrillation exhibit a systemic prothrombotic state attributable to impaired endogenous fibrinolysis

Background

The association of atrial fibrillation (AF) with thromboembolic stroke due to stasis in the left atrium and left atrial appendage is well described. Whether AF is associated with a systemic prothrombotic state, detectable in peripheral blood, unclear. Previous studies have been inconsistent, with some very small previous studies (<30 patients each) variably indicating that patients with AF may have raised platelet reactivity and levels of antithrombin III, d-dimer, PAI-1 and t-PA-PAI complexes. These cumbersome laboratory tests of coagulation and fibrinolysis are not readily available in the clinical setting.

Purpose

It was our aim to compare, in peripheral venous blood, thrombotic and endogenous fibrinolytic profile of healthy volunteers and patients with newly diagnosed nonvalvular atrial fibrillation (NVAF), using a point-of-care technique.

Methods

In a prospective observational study, venous blood samples were taken from 98 healthy volunteers and 100 patients with newly diagnosed NVAF in the out-patient setting. Patients with newly diagnosed NVAF had venous blood tested before any treatment was initiated with aspirin or oral anticoagulation. Thrombotic status was assessed using the Global Thrombosis Test (GTT), a point-of-care test using native non-coagulated blood, assessed within 15 sec of blood withdrawal. The time to form an occlusive venous thrombus in native (non-citrated) blood, a measure of platelet reactivity (occlusion time, OT) and the time taken to spontaneous endogenous fibrinolysis to restore flow (lysis time, LT) were assessed.

Results

Basic blood tests (full blood count, renal and liver function, inflammatory markers) were normal in all subjects. The groups were matched for sex and race. Mean age of the healthy cohort was 34±8 years and patients 65±10 years.

Endogenous fibrinolysis was markedly impaired in patients with NVAF compared to healthy individuals as shown by markedly prolonged LT (median 2015s [interquartile range IQR 1555–2507] vs. 1124s [IQR 919–1554], p<0.ehz745.11201). There was no difference in platelet reactivity between patients and normal volunteers (369s [IQR 308–445]vs 368s [IQR 309–441], p=0.704). Sensitivity analysis was performed on a subgroup matched for age, sex and race. LT remained significantly longer in patients with NVAF compared to controls (1569s [IQR 1499–2244] vs. 1219s [IQR 943–1560], p=0.03), with no difference in platelet reactivity (p=NS).

Conclusion

In the largest study to date and using a clinically-friendly automated point-of-care technique, we show that patients with NVAF exhibit a systemic prothrombotic state, attributable to significantly impaired endogenous fibrinolysis compared with healthy volunteers. Further studies are needed to see if this could become a screening test for the prothrombotic state in patients with NVAF.

Acknowledgement/Funding

None

P327Predictive value of platelet reactivity, neutrophil to lymphocyte ratio, and hs-CRP at presentation in patients with ST-elevation myocardial infarction treated with percutaneous coronary intervention

Background

Patients with ST-elevation myocardial infarction (STEMI) exhibit enhanced platelet reactivity and a rise in inflammatory biomarkers such as neutrophil to lymphocyte ratio (NLR) and high-sensitivity C-reactive protein (hs-CRP). The extent of the prothrombotic and inflammatory state are predictive of adverse outcomes in patients with acute coronary syndromes. The relationship of these markers of inflammation and thrombosis in the hyperacute phase of STEMI and, whether together, they improve cardiovascular outcome prediction, is not known.

Purpose

The aim of this study was to assess the individual and combined predictive values of NLR, hs-CRP, and platelet reactivity for clinical outcomes in patients with STEMI.

Method

In a prospective study of 541 patients presenting with STEMI, acute admission bloods taken prior to emergency percutaneous coronary intervention, were analysed for NLR and hs-CRP. Platelet reactivity was measured using the point-of-care Global Thrombosis Test, which assesses platelet reactivity in native whole blood under high shear, and measures the occlusion time (OT, sec). Shorter occlusion time represents higher platelet reactivity. The study endpoint was occurrence of major adverse cardiovascular events (MACE, defined as composite of cardiovascular death [CVD], myocardial infarction [MI] or stroke [CVA]) at 30 days and 12 months.

Results

There was a weak, but significant, correlation between hs-CRP and NLR (r=0.25, p<0.001), and hs-CRP and platelet reactivity (r=0.14, p=0.003) on admission. There was no correlation between platelet reactivity and NLR. Amongst 541 patients, 42 patients experienced a MACE within the first 30 days, and 50 within 12 months. Cut-values associated with the highest specificity and sensitivity for 12-month MACE were NLR 5.6, hs-CRP 8 mg/L and OT 302 sec. Platelet reactivity and hs-CRP were each only weakly predictive of MACE at 30 days (platelet reactivity: hazard ratio [HR] 1.004 [95% confidence interval (CI) 1.002–1.006,] p<0.001; hs-CRP: HR 1.005 [95% CI 1.0009–1.009], p=0.016) and 12 months (platelet reactivity HR 1.004 (95% CI 1.002–1.006), p<0.001; hs-CRP HR 1.005 (95% CI 1.001–1.01), p=0.014). NLR was not predictive of MACE at either 30 days or 12 months (p=NS). When patients were divided into quartiles based on hs-CRP and platelet reactivity, patients in the highest quartile for both hs-CRP and platelet reactivity had an HR 3.46 (95% CI 1.81–6.63), p<0.001 compared to those in the lowest quartile for both (HR 0.04 (95% CI 0.005–0.27), p=0.001). The combination of enhanced platelet reactivity and raised hs-CRP was the strongest predictor of MACE at 30 days (HR 2.32 [95% CI 1.71–3.13], p<0.001) and 12 months (HR 2.31 [95% CI 1.71–3.11], p<0.001).

Conclusion

Both hs-CRP and platelet reactivity are very weakly predictive of MACE, but in combination provide a strong predictor of adverse outcome in STEMI.