The role of point-of-care assessment of platelet function in predicting postoperative bleeding and transfusion requirements after coronary artery bypass grafting

Platelet dysfunction persists after trauma despite balanced blood product resuscitation

BACKGROUND

Platelet activation and aggregation are critical to the initiation of hemostasis after trauma with hemorrhage. Platelet dysfunction is a well-recognized phenomenon contributing to trauma-induced coagulopathy. The goal of this study was to evaluate the timing and severity of platelet dysfunction in massively transfused, traumatically injured patients during the first 72 hours after injury and its association with 30-day survival.

METHODS

A retrospective secondary cohort study of platelet count and function was performed using samples from the Pragmatic Randomized Optimal Platelet and Plasma Ratios trial. Platelet characteristics were measured at 8 timepoints during the first 72 hours of hospitalization and compared between 30-day survivors and nonsurvivors. Platelet counts were assessed via flow cytometry. Platelet function was analyzed with the use of serial thrombelastography and impedance aggregometry with agonists arachidonic acid, adenosine diphosphate, collagen, thrombin receptor activating peptide, and ristocetin.

RESULTS

In total, 680 patients were included for analysis. Platelet counts were significantly lower from baseline to 72 hours after hospital admission with further 1.3 to 2-fold reductions noted in nonsurvivors compared to survivor patients. Platelet aggregation via adenosine diphosphate, arachidonic acid, collagen, thrombin receptor activating peptide, and ristocetin was significantly lower in nonsurvivors at all time points. The nadir of platelet aggregation was 2 to 6 hours after admission with significant improvements in viscoelastic maximum clot formation and agonist-induced aggregation by 12 hours without concomitant improvement in platelet count.

CONCLUSION

Platelet aggregability recovers 12 hours after injury independent of worsening thrombocytopenia. Failure of platelet function to recover portends a poor prognosis.

Perioperative Management of Antiplatelet Therapy: A Systematic Review and Meta-analysis

OBJECTIVE

To summarize the available evidence about the perioperative management of patients who are receiving long-term antiplatelet therapy and require elective surgery/procedures.

METHODS

This systematic review supports the development of the American College of Chest Physicians guideline on the perioperative management of antiplatelet therapy. A literature search of MEDLINE, EMBASE, Scopus and Cochrane databases was conducted from each database's inception to July 16, 2020. Meta-analyses were conducted when possible.

RESULTS

In patients receiving long-term antiplatelet therapy and undergoing elective noncardiac surgery, the available evidence did not show a significant difference in major bleeding between a shorter vs longer antiplatelet interruption, with low certainty of evidence (COE). Compared with patients who received placebo perioperatively, aspirin continuation was associated with increased risk of major bleeding (relative risk [RR], 1.31; 95% CI, 1.15-1.50; high COE) and lower risk of major thromboembolism (RR, 0.74; 95% CI, 0.58-0.94; moderate COE). During antiplatelet interruption, bridging with low-molecular-weight heparin was associated with increased risk of major bleeding compared with no bridging (RR, 1.86; 95% CI, 1.24-2.79; very low COE). Continuation of antiplatelets during minor dental and ophthalmologic procedures was not associated with a statistically significant difference in the risk of major bleeding (very low COE).

CONCLUSION

This systematic review summarizes the current evidence about the perioperative management of antiplatelet therapy and highlights the urgent need for further research, particularly with the increasing prevalence of patients taking 1 or more antiplatelet agents.

Systematic Review and Meta-Analysis of Diagnostic Test Accuracy Studies Evaluating Point-of-Care Tests of Coagulopathy in Cardiac Surgery

Treatment guidelines recommend the routine use of point-of-care diagnostic tests for coagulopathy in the management of cardiac surgery patients at risk of severe bleeding despite uncertainty as to their diagnostic accuracy. We performed a systematic review and meta-analysis of studies that evaluated the diagnostic accuracy of viscoelastometry, platelet function tests, and modified thromboelastography (TEG) tests, for coagulopathy in cardiac surgery patients. The reference standard included resternotomy for bleeding, transfusion of non-red cell components, or massive transfusion. We searched MEDLINE, EMBASE, CINAHL, and Clinical Trials.gov, from inception to June 2019. Study quality was assessed using QUADAS-2. Bivariate models were used to estimate summary sensitivity and specificity with (95% confidence intervals). All 29 studies (7440 participants) included in the data synthesis evaluated the tests as predictors of bleeding. No study evaluated their role in the management of bleeding. None was at low risk of bias. Four were judged as low concern regarding applicability. Pooled estimates of diagnostic accuracy were; Viscoelastic tests, 12 studies, sensitivity 0.61 (0.44, 0.76), specificity 0.83 (0.70, 0.91) with significant heterogeneity. Platelet function tests, 12 studies, sensitivity 0.63 (0.53, 0.72), specificity 0.75 (0.64, 0.84) with significant heterogeneity. TEG modification tests, 3 studies, sensitivity 0.80 (0.67, 0.89), specificity 0.76 (0.69, 0.82) with no evidence of heterogeneity. Studies reporting the highest values for sensitivity and specificity had important methodological limitations. In conclusion, we did not demonstrate predictive accuracy for commonly used point-of-care devices for coagulopathic bleeding in cardiac surgery. However, the certainty of the evidence was low.

Implementation of Perioperative Point-of-Care Platelet Function Analyses Reduces Transfusion Requirements in Cardiac Surgery: A Retrospective Cohort Study

Background Platelet dysfunction is a common cause of bleeding, perioperative blood transfusion, and surgical re-exploration in cardiac surgical patients. We evaluated the effect of incorporating a platelet function analyzer utilizing impedance aggregometry (Multiplate, Roche, Munich, Germany) into our local transfusion algorithm on the rate of platelet transfusion and postoperative blood loss in patients undergoing coronary artery bypass grafting (CABG) surgery.

Methods Data were collected on patients undergoing CABG surgery from January 2015 to April 2017. Patients who underwent surgery before and after introduction of this algorithm were classified into prealgorithm and postalgorithm groups, respectively. The primary outcome was the rate of platelet transfusion before and after implementation of the Multiplate-based transfusion algorithm. Secondary outcomes included transfusion rate of packed red blood cells, postoperative blood loss at 12 and 24 hours, length of stay in the intensive care unit, and the hospital and mortality.

Results A total of 726 patients were included in this analysis with 360 and 366 patients in the pre- and postalgorithm groups, respectively. Transfusion rates of platelets (p = 0.01) and packed red blood cells (p = 0.0004) were significantly lower following introduction of the algorithm in patients (n = 257) who had insufficient time to withhold antiplatelet agents. Receiver operating characteristic curves defined optimal cutoff points of arachidonic acid and adenosine diphosphate assays on the Multiplate to predict future platelet transfusion were 23AU and 43AU, respectively.

Conclusions The introduction of a Multiplate-based platelet transfusion algorithm showed a statistically significant reduction in the administration of platelets to patients undergoing urgent CABG surgery.

Multiple electrode aggregometry and thromboelastography in thrombocytopenic patients with haematological malignancies

BACKGROUND

In thrombocytopenic patients better assessment of bleeding risk than that provided by platelet count alone is required. Multiplate® aggregometry and thromboelastography (TEG) could be used, but information on their role in such patients is limited. The primary aim of this study was to investigate the feasibility of Multiplate® analyses in patients with haematological malignancies. A secondary aim was to explore whether a multiple logistic regression model combining Multiplate®, TEG, clinical and laboratory variables was associated with risk of bleeding.

MATERIALS AND METHODS

This was an exploratory, prospective observational study of thrombocytopenic patients with haematological malignancies. Total platelet count (TPC), white blood cell count, C-reactive protein (CRP) level, temperature and bleeding status were recorded daily. TEG and Multiplate® analyses with four agonists were performed on weekdays.

RESULTS

Ten patients were enrolled into the study. The median number of days in a study period was 21. Bleeding was observed on 64 of 298 study days. TPC <20×109/L and <10×109/L occurred on 119 and 25 days, respectively. When TPC was <33×109/L, many samples showed no aggregation, regardless of bleeding status. Despite this, the odds of World Health Organization (WHO) grade 2 bleeding decreased significantly as aggregation increased and Multiplate® had a negative predictive value (NPV) of 96% and a positive predictive value (PPV) of 19% for significant bleeding. In the multiple logistic regression model collagen-activated Multiplate® aggregation, TEG angle, TEG reaction time and CRP significantly affected the odds of WHO grade 2 bleeding. The combined model had a NPV of 99% and a PPV of 19%.

DISCUSSION

Our findings suggest that the markers of platelet function and haemostasis provided by Multiplate® aggregometry and TEG may add information to support prediction of bleeding, although platelet count still remains the most accessible analysis for routine testing.

Intraoperative and postoperative effects of TEG-guided platelet transfusion on antiplatelet drug-related intracerebral hemorrhage patients

Intraoperative and postoperative effects of platelet transfusion on antiplatelet drug-related intracerebral hemorrhage (ICH) patients were investigated. A retrospective study on 82 ICH patients undergoing emergency surgical treatment caused by antiplatelet drugs was conducted. Among them, 51 patients treated with platelet transfusion served as the observation group and 31 patients without platelet transfusion as the control group. The intraoperative and postoperative bleeding volume, blood transfusion volume and the rate of secondary bleeding were compared between observation and control group under the guidance of thromboelastography (TEG). The coagulation routine examination results of the two groups before surgery were in the normal range, but TEG indicated an excessive inhibition of platelet function (platelet inhibition rate >89%). The platelet number after treatment increased significantly in the two groups of patients and it was significantly higher in observation group than that in control group (P<0.05). The intraoperative bleeding volume in observation group was significantly lower than that in control group. The total blood transfusion volume in observation group was significantly lower than that in control group (Z=2.681, P=0.036), the postoperative hematoma residual volume in observation group was significantly lower than that in control group (t=2.145, P=0.035), and the drainage volume in observation group was significantly lower than that in control group (t=2.401, P=0.019). Only 3.92% of the patients in observation group and 19.35% in control group had secondary surgery, and the difference of the recurrence rate of secondary bleeding between the two groups was statistically significant (χ²=3.610, P=0.048). TEG detection indicator can more comprehensively and accurately evaluate the preoperative coagulation function of patients. This study suggests that preoperative platelet transfusion can improve the intraoperative and postoperative bleeding of ICH patients after antiplatelet therapy to some extent, reducing the blood transfusion volume and the secondary bleeding rate.

Rotational Thromboelastometry for Assessing Bleeding Complications and Factor XIII Deficiency in Cardiac Surgery Patients

We aimed to detect alterations and deficits in hemostasis during cardiac surgery with cardiopulmonary bypass (CPB) using point-of-care-supported coagulation analysis (rotational thromboelastometry, impedance aggregometry), in addition to single factor assays for the measurement of fibrinogen (FI) and factor XIII (FXIII) levels. Forty-one patients scheduled for elective cardiac surgery with CPB were enrolled in this observational study. Perioperative measurement (pre-, postheparin, 30-minutes before the end of bypass, 1-hourpostoperatively) of standard laboratory variables, additional rotational thromboelastometry (ROTEM; International GmbH, Munich, Germany), Multiplate analysis (Roche, Switzerland), and an assay of FXIII activity were performed as well as the collection of epidemiological data and blood loss. The FI and FXIII levels as well as the measured ROTEM and Multiplate parameters correlated weakly with the blood loss. Clotting time and maximum clot firmness (MCF) of the intrinsically activated ROTEM showed a good correlation (r_CT-INTEM = 0.378; P < .05, r_MCF-INTEM = 0.305; P < .05) with postoperative drainage loss, suggesting a dependence of blood loss on the initial intrinsic activity. Additionally, perioperative FI or FIBTEM levels and the FXIII levels correlated with each other. Intrinsically activated ROTEM showed a good correlation with postoperative drainage loss, thus suggesting a dependence of blood loss on the initial intrinsic activity and therefore facilitating clinicians to assess postoperative bleeding complications. Based on the FI level or the MCF_FIBTEM measured by ROTEM, it may also be possible to assess the FXIII concentration. Especially in chronically ill and massive bleeding cardiac surgery patients with significantly decreased FXIII levels, the knowledge of FXIII deficiency may help clinicians to treat coagulation disorders more adequately.

Effects of preoperative plasma exchange therapy with albumin replacement fluid on blood coagulation in patients undergoing ABO-incompatible living-donor kidney transplantation using rotational thromboelastometry

BACKGROUND

ABO-incompatible living-donor kidney transplantation (LDKT) requires immunotherapy and plasma exchange therapy (PEX). PEX with albumin replacement fluid reportedly decreases fibrinogen levels. However, no reports have described the effects of PEX with albumin replacement fluid on blood coagulation parameters and blood loss during the perioperative period. Therefore, we investigated the effects of preoperative PEX on blood coagulation parameters and blood loss during the perioperative period in patients undergoing ABO-incompatible LDKT as measured by rotational thromboelastometry (ROTEM®).

METHODS

Twenty-eight patients undergoing LDKT were divided into the PEX group (ABO incompatible with PEX, n = 13) and non-PEX group (ABO compatible without PEX, n = 15). ROTEM® parameters, standard laboratory test parameters, bleeding volume, and transfusion volume were compared between PEX and non-PEX group. MCE_platelet, which represents platelet contribution to clot strength and where "MCE" stands for maximum clot elasticity, was calculated from the difference in MCE between EXTEM and FIBTEM.

RESULTS

The bleeding volume during surgery and the intensive care unit (ICU) stay was significantly higher in the PEX than non-PEX group (p < 0.01). Maximum clot firmness (MCF) of EXTEM (MCF_EXTEM), MCF_FIBTEM, and MCE_platelet was significantly lower in the PEX than non-PEX group (p < 0.01). In the PEX group, the bleeding volume during surgery was very strongly correlated with the baseline MCF_EXTEM and MCE_platelet, and the bleeding volume during the ICU stay was strongly correlated with the postoperative MCF_EXTEM and MCE_platelet.

CONCLUSIONS

These results suggest that the increased blood loss in the PEX group during surgery and the ICU stay was associated with decreased platelet contribution to clot strength as measured by ROTEM®.

TRIAL REGISTRATION

UMIN-Clinical Trial Registry UMIN000018355 . Registered 21 July 2015.

Perioperative changes in platelet count and function in patients undergoing cardiac surgery

Background: Patients undergoing cardiac surgery are at increased risk of bleeding due to multifactorial coagulopathies. In the present study, we aimed at investigating the changes in platelet count and function during and after surgery as well as determining the association of the platelet dysfunction with bleeding and transfusion requirements in these patients.

Methods: A total of 40 adult patients scheduled for elective valve coronary cardiac surgery were included in this prospective observational study. Changes in platelet count and function with ADP, acid arachidonic, and collagen (light transmission aggregometry) were analyzed at three time points: before CPB, after CPB, and 24 hours after end of surgery. Postoperative bleeding and intraoperative transfusion requirements were recorded.

Results: There were a significant reverse correlation between CPB time and ADP-induced aggregation, particularly after CPB and postoperative AA-induced aggregation. There was not any significant correlation between platelet count and function at all-time points. Both platelet count and platelet aggregation significantly reduced during CPB. While platelet aggregation increased on postoperative Day 1, platelet count reduced by about 40% after CPB, and remained at this level postoperatively. Patients with abnormal ADP-induced aggregation had significant increased postoperative bleeding and transfusion requirements.

Conclusion: The results of this study demonstrate that platelet count and platelet aggregation are reduced during CPB. Our results emphasized the effect of platelet dysfunction on increased postoperative bleeding and transfusion requirements. Perioperative monitoring of platelet function can be considered as a bleeding management strategy for implantation of PBM programs.

CRUSADE Score is Superior to Platelet Function Testing for Prediction of Bleeding in Patients Following Coronary Interventions

Hypothetically, diminished platelet reactivity (PR) during dual antiplatelet therapy (DAPT) should cause extra major bleeding events (MBE), although definite evidence is lacking. Multiple scores have been proposed to stratify bleeding risk, but their predictive value during DAPT is unclear. We compared the performance of the Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the ACC/AHA Guidelines (CRUSADE) with PR testing to predict MBE in Korean patients with acute coronary syndrome. We screened 1105, and included 903 consecutive patients who underwent coronary interventions. All patients received DAPT, while MBE were assessed by BARC scale. Admission platelet reactivity was assessed with VerifyNow Analyzer simultaneously with CRUSADE score, and MBE were collected at 1 month and at 1 year post stenting. There were a total of 113 (11%) MBE at 1 month, and extra 41(5%) MBE at 1 year. At 1 month MBE prediction was superior by CRUSADE score (AUC: 0.816, 95% CI: 0.79 0.84, p < 0.0001), compared to PR (AUC: 0.605, 95% CI: 0.572–0.637, p = 0.0007). Moreover, CRUSADE score remains the independent predictor of MBE by multivariate analyses (OR = 2.94, 95% CI: 2.18–3.96, p < 0.0001). At 1 year MBE also correlated, but were not significantly different between admission CRUSADE score (AUC: 0.62, 95% CI: 0.58 0.66, p = 0.0183) and PR (AUC: 0.674, 95% CI: 0.63–0.71, p = 0.002). We conclude that MBE are more common in real life than reported in clinical trials. CRUSADE score was superior to PR testing for predicting short-term, but not 1 year MBE in Korean patients undergoing percutaneous coronary intervention and treated with DAPT.

•

Dual antiplatelet therapy for 1 year is a golden standard following coronary stenting in patients with acute coronary syndromes.

•

Bleeding is a life-threatening major complication associated with chronic aggressive antiplatelet strategies.

•

Predicting bleeding based on clinical features or established biomarkers is upmost yet unsolved mystery affecting clinical outcomes in such high-risk patients

•

The CRUSADE clinical score predicts bleeding better than platelet reactivity indices

•

Short-term bleedings at 30 days, but not delayed 1-yearly hemorrhages were better predicted by CRUSAIDE in East Asians.

Dual antiplatelet therapy for 1 year is common following coronary stenting in patients with acute coronary syndromes. However, bleeding is a life-threatening major complication and shortcoming associated with chronic aggressive antiplatelet strategies. CRUSADE score was introduced for better prediction of in-hospital bleeding, while delayed bleeding risks remained unclear. Usually bleeding risk is assessed based on clinical features or by established biomarkers We tested the hypothesis on the superiority of CRUSADE score versus conventional platelet reactivity in a large Korean registry, and revealed the following: major bleeding events in real life are more frequent, and are heavily unreported in clinical trials; the CRUSADE clinical score predicts bleeding better than platelet reactivity indices. Unfortunately, short-term bleedings at 30 days, but not delayed 1-yearly hemorrhages were better predicted by CRUSADE in East Asians.

The use of viscoelastic haemostatic assays in goal-directing treatment with allogeneic blood products - A systematic review and meta-analysis

BACKGROUND

Management of the critically bleeding patient can be encountered in many medical and surgical settings. Common for these patients is a high risk of dying from exsanguination secondary to developing coagulopathy. The purpose of this meta-analysis was to systematically review and assess randomised controlled trials (RCTs) performed on patients in acute need for blood transfusions due to bleeding to evaluate the effect of viscoelastic haemostatic assay (VHA) guidance on bleeding, transfusion requirements and mortality.

METHODS

PubMed and EMBASE were searched for RCTs that 1) randomised patients into receiving transfusions based on either a VHA-guided (thromboelastography [TEG] or rotational thromboelastometry [ROTEM]) algorithm (intervention group) or at the clinician's discretion and/or based on conventional coagulation tests (control group) and 2) adequately reported on the outcomes bleeding and/or transfusions and/or mortality. Data on bleeding, transfusions and mortality were extracted from each trial and included in a meta-analysis.

RESULTS

Fifteen RCTs (n = 1238 patients) were included. Nine trials referred to cardiothoracic patients, one to liver transplantation, one to surgical excision of burn wounds and one to trauma. One trial was conducted with cirrhotic patients, one with patients undergoing scoliosis surgery while one trial randomised treatment in post-partum females presenting with bleeding. The amount of transfused red blood cells (RBCs), fresh frozen plasma (FFP) and bleeding volume was found to be significantly reduced in the VHA-guided groups, whereas no significant difference was found for platelet transfusion requirements or mortality.

Simulation in coagulation testing using rotational thromboelastometry: A fast emerging, reliable point of care technique

Computer simulations can come in handy to train medical personnel with necessary skills to face the clinical scenarios involving various coagulopathies. Now a days, point of care (POC) devices such as thromboelastography, Sonoclot analyzer and newly approved rotational thromboelastometry (ROTEM) with faster results to assess coagulopathies are available on bedside of patients. ROTEM is emerging as a quick, portable, and well-validated device to evaluate coagulopathy in critical care and perioperative setup. A novel platelet-aggregometry integrated module enables simultaneous analysis of platelets as well as coagulation tests on the same screen. The entire gamut of POC signature curves obtained with different coagulation defects can be learned with graphical simulations. These simulations can be a valuable strategy to elucidate latent conditions, for which simulation interventions can then be designed to mimic different clinical scenarios.

Perioperative management of patient with intracoronary stent presenting for noncardiac surgery

As the number of percutaneous coronary interventions increase annually, patients with intracoronary stents (ICS) who present for noncardiac surgery (NCS) are also on the rise. ICS is associated with stent thrombosis (STH) and requires mandatory antiplatelet therapy to prevent major adverse cardiac events. The risks of bleeding and ischemia remain significant and the management of these patients, especially in the initial year of ICS is challenging. The American College of Cardiologists guidelines on the management of patients with ICS recommend dual antiplatelet therapy (DAT) for minimal 14 days after balloon angioplasty, 30 days for bare metal stents, and 365 days for drug-eluting stents. Postponement of elective surgery is advocated during this period, but guidelines concerning emergency NCS are ambiguous. The risk of STH and surgical bleeding needs to be assessed carefully and many factors which are implicated in STH, apart from the type of stent and the duration of DAT, need to be considered when decision to discontinue DAT is made. DAT management should be a multidisciplinary exercise and bridging therapy with shorter acting intravenous antiplatelet drugs should be contemplated whenever possible. Well conducted clinical trials are needed to establish guidelines as regards to the appropriate tests for platelet function monitoring in patients undergoing NCS while on DAT.

Point-of-care platelet function testing to predict blood loss after coronary artery bypass grafting surgery: a prospective observational pilot study

Aim:

With an increase in the number of patients who are on antiplatelet medications until the day of surgery, we undertook a prospective observational study to assess the ability of thromboelastography, thromboelastography platelet mapping and aggregometry via multiplate to detect platelet dysfunction and predict blood loss following coronary artery bypass grafting (CABG) surgery.

Methods:

Platelet function was evaluated pre- and post-cardiopulmonary bypass via thromboelastography, thromboelastography platelet mapping and aggregometry via multiplate in 52 patients undergoing coronary artery bypass grafting surgery. The median chest tube drainage of all patients in the study was ascertained to stratify patients into two groups: patients with and those without evidence of excessive blood loss after cardiac surgery.

Results:

Although all modalities could detect a decrease in platelet function following cardiopulmonary bypass, univariate and multivariate regression analysis identified preoperative arachidonic acid and adenosine diphosphate testing via multiplate as independent predictors of bleeding after cardiac surgery. Receiver operating curves on these multiplate parameters showed an area under the curve of 0.68 (p=0.03) and 0.66 (p=0.01) for arachidonic acid and adenosine diphosphate assays, respectively.

Conclusion:

This pilot study shows that preoperative multiplate testing may be a better predictor of platelet dysfunction and the resultant blood loss following cardiac surgery.

Decreased maximum clot firmness in rotational thromboelastometry (ROTEM®) is associated with bleeding during extracorporeal mechanical circulatory support

BACKGROUND:

We aimed to characterize the coagulation disturbances which may increase the risk of bleeding, thrombosis or death shortly after implantation of an extracorporeal membrane oxygenation (ECMO) or ventricular assist (VAD) device.

METHODS:

Antithrombotic treatment was started in 23 VAD and 24 ECMO patients according to the hospital protocol. Additionally, conventional laboratory testing, rotational thromboelastometry (ROTEM®) and platelet function analysis (Multiplate®) were performed at predetermined intervals.

RESULTS:

Four out of twenty-four (16.7%) of ECMO patients and 6/23 (26.1%) of VAD patients had severe bleeding after the procedure. When all the patients were analyzed together, low maximum clot firmness (MCF) in ExTEM and FibTEM analyses was associated with severe bleeding (p<0.05) and low MCF in FibTEM with 30-day mortality. Low platelet count and hematocrit levels were also associated with severe bleeding. When VAD and ECMO patients were separated into different groups, the association between ROTEM® parameters, bleeding and survival was found only in limited time points. Four patients with VAD had cerebral ischemia indicative of thromboembolism. However, this had no significant correlation with ROTEM® or Multiplate® parameters.

CONCLUSION:

Hypocoagulation shown by ROTEM® was associated with bleeding complications in patients with mechanical circulatory support. In contrast, hypercoagulation did not correlate with clinical thrombosis.

Validation of Three Platelet Function Tests for Bleeding Risk Stratification During Dual Antiplatelet Therapy Following Coronary Interventions

BACKGROUND

Although low platelet reactivity (LPR) is commonly detected during bleeding, a validated threshold for reliable DAPT bleeding risk stratification is lacking. We tested the diagnostic utility of 3 conventional platelet-activity assays to define the predictive value (if any) of LPR for bleeding.

HYPOTHESIS

We hypothesized whether one of these tests be better than any others for predicting bleeding events.

METHODS

Patients (n = 800) following drug-eluting stent implantation received DAPT. Bleeding was assessed by Bleeding Academic Research Consortium (BARC) classification and events were collected for 1 year after stenting. Platelet reactivity was measured by light transmittance aggregometry (LTA), VerifyNow, and multiple electrode aggregometry (MEA). The LPR values for bleeding event stratification were defined as ≤15% for LTA, ≤139 PRU for VerifyNow, and ≤25 U for MEA.

RESULTS

Bleeding events occurred in 18 patients (2.3%). All tests distinguished LPR as an independent predictor for bleeding by univariate analysis ([HR]: 5.00, 95% [CI]: 1.8-14.0, P = 0.002 for LTA; HR: 21.3, 95% CI: 6.2-73.0, P < 0.0001 for VerifyNow; and HR: 7.4, 95% CI: 2.2-25.5, P = 0.002 for MEA). Multivariate analysis revealed that only VerifyNow (HR: 11.5, 95% CI: 2.9-45.7, P < 0.0004) remained an independent predictor for bleeding. However, the specificity (81.5%, 60.2%, and 81.7%, respectively) and sensitivity (61.1%, 83.3%, and 83.2%, respectively) of all 3 tests were quite low.

CONCLUSIONS

Among 3 conventional platelet-activity assays, VerifyNow was better than LTA or MEA for triaging future bleeding risks. However, all 3 tests failed to reliably predict future bleeding.

Anti-platelet Therapy Resistance - Concept, Mechanisms and Platelet Function Tests in Intensive Care Facilities

It is well known that critically ill patients require special attention and additional consideration during their treatment and management. The multiple systems and organ dysfunctions, typical of the critical patient, often results in different patterns of enteral absorption in these patients. Anti-platelet drugs are the cornerstone in treating patients with coronary and cerebrovascular disease. Dual anti-platelet therapy with aspirin and clopidogrel is the treatment of choice in patients undergoing elective percutaneous coronary interventions and is still widely used in patients with acute coronary syndromes. However, despite the use of dual anti-platelet therapy, some patients continue to experience cardiovascular ischemic events. Recurrence of ischemic events is partly attributed to the fact that some patients have poor inhibition of platelet reactivity despite treatment. These patients are considered low- or non-responders to therapy. The underlying mechanisms leading to resistance are not yet fully elucidated and are probably multifactorial, cellular, genetic and clinical factors being implicated. Several methods have been developed to asses platelet function and can be used to identify patients with persistent platelet reactivity, which have an increased risk of thrombosis. In this paper, the concept of anti-platelet therapy resistance, the underlying mechanisms and the methods used to identify patients with low responsiveness to anti-platelet therapy will be highlighted with a focus on aspirin and clopidogrel therapy and addressing especially critically ill patients.

Low multiple electrode aggregometry platelet responses are not associated with non-synonymous variants in G-protein coupled receptor genes

INTRODUCTION

Multiple electrode aggregometry (MEA) improves prediction of thrombosis and bleeding in cardiac patients. However, the causes of inter-individual variation in MEA results are incompletely understood. We explore whether low MEA results are associated with platelet G-protein coupled receptor (GPCR) gene variants.

METHODS

The effects of P2Y12 receptor (P2Y12), thromboxane A2 receptor (TPα) and protease-activated receptor 1 (PAR1) dysfunction on the MEA ADP-test, ASPI-test and TRAP-test were determined using receptor antagonists. Cardiac surgery patients with pre-operative MEA results suggesting GPCR dysfunction were selected for P2Y12 (P2RY12), TPα (TBXA2R) and PAR1 (F2R) sequencing.

RESULTS

In control blood samples, P2Y12, TPα or PAR1 antagonists markedly reduced ADP-test, ASPI-test and TRAP-test results respectively. In the 636 patients from a cohort of 2388 cardiac surgery patients who were not receiving aspirin or a P2Y12 blocker, the median ADP-test result was 75.1 U (range 4.8-153.2), ASPI-test 83.7 U (1.4-157.3) and TRAP-test 117.7 U (2.4-194.1), indicating a broad range of results unexplained by anti-platelet drugs. In 238 consenting patients with unexplained low MEA results, three P2RY12 variants occurred in 70/107 (65%) with suspected P2Y12 dysfunction and four TBXA2R variants occurred in 19/22 (86%) with suspected TPα dysfunction although the later group was too small to draw meaningful conclusions about variant frequency. All the variants were synonymous and unlikely to cause GPCR dysfunction. There were no F2R variants in the 109 cases with suspected PAR1 dysfunction.

CONCLUSION

MEA results suggesting isolated platelet GPCR dysfunction were common in cardiac surgery patients, but were not associated with non-synonymous variants in P2RY12 or F2R.