Aspirin Resistance in Single-Ventricle Physiology: Aspirin Prophylaxis Is Not Adequate to Inhibit Platelets in the Immediate Postoperative Period

The Effects of Aspirin dose in Children with Congenital and Acquired Heart Disease. Results from the Paediatric Study of Aspirin Efficacy using Diagnostic and Monitoring Tools (PAED-M)

The optimal dose of aspirin required in children with congenital and acquired heart disease is not known. The primary aim of this prospective observational study was to evaluate the effects of aspirin dose on platelet inhibition. The secondary aim was to determine the prevalence and clinical predictors of aspirin non-responsiveness. Measurements were by Thromboelastography with Platelet Mapping (TEGPM) only in children less than 2 years (y) of age with particular emphasis on the parameter known as maximum amplitude with arachidonic acid (MAAA) and using both TEGPM, and light transmission aggregometry (LTA) in children greater than 2 y. We prospectively studied 101 patients with congenital and acquired cardiac disease who were receiving empirical doses of aspirin for a minimum of 4 weeks but no other antiplatelet agents. Patients were stratified according to dose concentration and age. There was a trend toward lower age in patients with no response or semi-response to aspirin. All patients were considered responsive to aspirin in the higher-dose quartile (Q4) with a median dose of 4.72 (4.18-6.05) mg/kg/day suggesting that patients in this age group may require 5 mg/kg/day as an empirical dose. In children > 2 y, there was no significant difference in inhibition found in patients dosed at higher doses in Q3 versus Q4 suggesting that patients in this cohort are responsive with 3 mg/kg/day dose. The current practices may lead to reduced platelet inhibition in some children due to under-dosing or overdosing in others. In conclusion, younger children require higher doses of aspirin. Laboratory assessment is warranted in this population to mitigate against under and overdosing.

Aspirin Responsiveness in a Cohort of Pediatric Patients with Right Ventricle to Pulmonary Artery Conduits and Transcatheter Valve Replacement Systems

The aim of this study was to determine the rate of aspirin responsiveness in a cohort of pediatric patients with in situ xenograft valved right ventricle to pulmonary artery (RV-PA) conduits and/or transcatheter valve replacements (TVR). Aspirin is routinely prescribed to these patients. Optimizing anti-platelet therapy could promote valve longevity and reduce the risk of infective endocarditis in this at-risk group. This was a prospective, observational study. Patients were recruited from both ward and outpatient settings. Patients were eligible if under 18 years and taking aspirin. Non-response to aspirin was defined as > 20% platelet aggregation using light transmission platelet aggregometry (LTA) and < 50% platelet inhibition by thromboelastography with platelet mapping (TEGPM). Participants were invited to provide a confirmatory sample in cases of aspirin resistance and dose adjustments were made. Thirty patients participated. Median age was 9 years (2 months to 18 years). The majority (93%) had complex right ventricular outflow tract pathology. 13 (43%) had an RV-PA conduit and 24 (80%) had a TVR, with valve situated in conduit in 7 (23%) cases. Rate of aspirin non-response on initial testing was 23% (n = 7/30) with median LTA 74.55% (60-76%) and TEG 13.25% (0-44%) in non-responders. Non-responders were more likely to be under 1 year. Two patients required dose increases and one patient non-adherence to dose was identified. Four patients on repeat testing were responsive to aspirin by laboratory tests. The rate of aspirin non-response on laboratory testing in this cohort of patients was 23% and resulted in therapeutic intervention in 10%.

Towards a greater understanding of reduced response to aspirin in children with congenital heart disease post-cardiac surgery using immature platelet fraction

OBJECTIVE

A high platelet turnover rate may produce a population of platelets that confers an inadequate response to aspirin. We aimed to investigate the relationship between residual platelet aggregation and platelet turnover in paediatric cardiology patients on aspirin monotherapy by evaluating the fraction of immature platelets as a marker for turnover and secondly to test the predictive value of the immature platelet fraction (IPF) to classify patients as responsive or non-responsive to aspirin.

METHODS

Sixty patients divided into two age categories (≤90 days, >90 days of age) were included in this prospective observational study. Patients were then stratified into tertiles using their IPF level. Platelet studies included thromboelastography with platelet mapping (TEGPM).

RESULTS

The overall incidence of 'inadequate response to aspirin' was 38 % in our patient cohort recently post-cardiac surgery a consequence that warrants further study. The frequency of inadequate response to aspirin was higher in the upper tertile of IPF when compared to the lower tertile, (88 %) versus (4 %) respectively (p < 0.05). The 'cut off' for IPF was determined to be 3.9 % with a sensitivity of 95.7 %, and a specificity of 92.9 % (area under the curve of 0.955 [CI 0.896-1.014, p < 0.05]).

CONCLUSION

This study demonstrates that inadequate response to aspirin occurs in approximately 38 % of patients undergoing specific high-risk congenital cardiac procedures using the dosing practice of a national centre. This study supports the hypothesis that an elevated platelet turnover may result in aspirin being less effective in patients who are recently post cardiac surgery. These data are of direct translational relevance.

Novel Dosing and Monitoring of Aspirin in Infants With Systemic-to-Pulmonary Artery Shunt Physiology: the SOPRANO Study

OBJECTIVES

Provision of pulmonary blood flow with a systemic-to-pulmonary artery shunt is essential in some patients with cyanotic congenital heart disease. Traditionally, aspirin (ASA) has been used to prevent thrombosis. We evaluated ASA dosing with 2 separate antiplatelet monitoring tests for accuracy and reliability.

METHODS

This is a retrospective, pre-post intervention single center study. Two cohorts were evaluated; the pre-intervention group used thromboelastography platelet mapping (TPM) and post-intervention used VerifyNow aspirin reactivity unit (ARU) monitoring. The primary endpoint was to compare therapeutic effect of TPM and ARU with regard to platelet inhibition. Inadequate platelet inhibition was defined as TPM <50% inhibition and ARU >550.

RESULTS

Data from 49 patients were analyzed: 25 in the TPM group and 24 in the ARU group. Baseline characteristics were similar amongst the cohorts. The TPM group had significantly more patients with inadequate platelet inhibition (14 [56%] vs 2 [8%]; p = 0.0006) and required escalation with additional thromboprophylaxis (15 [60%] vs 5 [21%]). There was no difference in shunt thrombosis (1 [2%] vs 0 [0%]; p = 0.32), cyanosis requiring early re-intervention (9 [36%] vs 14 [58%]; p = 0.11), or bleeding (15 [60%] vs 14 [58%]; p = 0.66).

CONCLUSION

With similar cohorts and the same ASA-dosing nomogram, ARU monitoring resulted in a reduced need for escalation of care and concomitant thromboprophylaxis with no difference in adverse outcomes. Our study suggests ARU monitoring compared with TPM may be a more reliable therapeutic platelet inhibition test for determining ASA sensitivity in children with congenital heart disease requiring systemic-to-pulmonary artery shunt.

Efficacy and Safety of NSAIDs in Infants: A Comprehensive Review of the Literature of the Past 20 Years

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used in infants, children, and adolescents worldwide; however, despite sufficient evidence of the beneficial effects of NSAIDs in children and adolescents, there is a lack of comprehensive data in infants. The present review summarizes the current knowledge on the safety and efficacy of various NSAIDs used in infants for which data are available, and includes ibuprofen, dexibuprofen, ketoprofen, flurbiprofen, naproxen, diclofenac, ketorolac, indomethacin, niflumic acid, meloxicam, celecoxib, parecoxib, rofecoxib, acetylsalicylic acid, and nimesulide. The efficacy of NSAIDs has been documented for a variety of conditions, such as fever and pain. NSAIDs are also the main pillars of anti-inflammatory treatment, such as in pediatric inflammatory rheumatic diseases. Limited data are available on the safety of most NSAIDs in infants. Adverse drug reactions may be renal, gastrointestinal, hematological, or immunologic. Since NSAIDs are among the most frequently used drugs in the pediatric population, safety and efficacy studies can be performed as part of normal clinical routine, even in young infants. Available data sources, such as (electronic) medical records, should be used for safety and efficacy analyses. On a larger scale, existing data sources, e.g. adverse drug reaction programs/networks, spontaneous national reporting systems, and electronic medical records should be assessed with child-specific methods in order to detect safety signals pertinent to certain pediatric age groups or disease entities. To improve the safety of NSAIDs in infants, treatment needs to be initiated with the lowest age-appropriate or weight-based dose. Duration of treatment and amount of drug used should be regularly evaluated and maximum dose limits and other recommendations by the manufacturer or expert committees should be followed. Treatment for non-chronic conditions such as fever and acute (postoperative) pain should be kept as short as possible. Patients with chronic conditions should be regularly monitored for possible adverse effects of NSAIDs.

Current evidence for pharmacologic therapy following stage 1 palliation for single ventricle congenital heart disease

INTRODUCTION

Infants with single ventricle congenital heart disease are vulnerable to complications between stage 1 and stage 2 of palliation. Pharmaceutical treatment during this period is varied and often dependent on institutional practices as there is little evidence supporting a particular treatment path.

AREAS COVERED

This review focuses on medical management of patients following stage I palliation. We performed a scoping review of the current literature regarding angiotensin converting enzyme inhibitors and digoxin treatment in the interstage period. In addition, we discuss other medication classes frequently used in these patients.

EXPERT OPINION

Due to significant heterogeneity of anatomy, rarity of disease, and other confounding factors, there is limited evidence to support most commonly used medications within the interstage period. Digoxin is associated with improved mortality within the interstage period and should be considered; however, no large randomized controlled trial exists supporting its use. Prevention of thrombotic complication with aspirin is also associated with improved outcomes and should be considered unless a contraindication exists. The addition of other prescriptions in this patient population should be considered only after an evaluation of the risks and benefits of each medication, recognizing the burden and risk of polypharmacy in this fragile patient population.

Platelet Aggregation Before Aspirin Initiation in Pediatric Patients With Congenital Heart Disease at High Risk of Thrombosis

Background

Aspirin following unfractionated heparin is the most common anticoagulation strategy for pediatric patients who experienced cardiac surgery at high risk of thrombosis. The platelet aggregation test is the golden method to evaluate the aspirin effect on platelet function. However, the platelet aggregation basal status before postoperative aspirin initiation and the related clinical influencing factors hasn't been investigated systemically in this population.

Methods

In a prospective cohort of 247 children, arachidonic acid-induced platelet aggregation (PAG-AA) was measured by means of light transmission aggregometry (LTA) before the first dose of aspirin after cardiac surgical procedure and the perioperative variables were also collected. Distribution of this population's PAG-AA basal status was described. Univariate and multivariate logistic regression analysis were performed to identify the main influencing factors of PAG-AA.

Results

The median time of aspirin administration was 2 (1–27) days after surgery and the corresponding median value of basal PAG-AA was 20.70% (1.28–86.49%), with 67.6% population under 55% and 47.8% population under 20%. Patients undergoing cardiopulmonary bypass (CPB) had a significantly lower basal PAG-AA than those without (30.63 ± 27.35 vs. 57.91 ± 27.58, p = 0.013). While patients whose test done within 3 days after CPB had a significantly lower PAG-AA than those out of 3 days (25.61 ± 25.59 vs. 48.59 ± 26.45, p = 0.001). Univariate analysis implied that the influencing factors of the basal PAG-AA including CPB use, test time point, cyanosis, and platelet count. Multivariate regression analysis indicated that only CPB use, test time point, and platelet count were the main independent influencing factors for the basal PAG-AA.

Conclusion

The majority of children have impaired basal platelet aggregometry responses before postoperative aspirin initiation. The main influencing factors are CPB use, test time point, and platelet count. To establish the platelet aggregometry baseline prior to commencement of aspirin therapy, testing should be performed 3 days later following the procedure when effect of CPB is basically over.

Application of a TEG-Platelet Mapping Algorithm to Guide Reversal of Antiplatelet Agents in Adults with Mild-to-Moderate Traumatic Brain Injury: An Observational Pilot Study

BACKGROUND

Traumatic intracranial hemorrhages expand in one third of cases, and antiplatelet medications may exacerbate hematoma expansion. However, the reversal of an antiplatelet effect with platelet transfusion has been associated with harm. We sought to determine whether a thromboelastography platelet mapping (TEG-PM)-guided algorithm could limit platelet transfusion in patients with hemorrhagic traumatic brain injury (TBI) prescribed antiplatelet medications without a resultant clinically significant increase in hemorrhage volume, late hemostatic treatments, or delayed operative intervention.

METHODS

A total of 175 consecutive patients with TBI were admitted to our university-affiliated, level I trauma center between March 2016 and December 2019: 54 preintervention patients (control) and 121 patients with TEG-PM (study). After exclusion for anticoagulant administration, availability of neuroimaging and emergent neurosurgery, 62 study patients and 37 control patients remained. Intervention consisted of administration of desmopressin (DDAVP) for nonsurgical patients with significant inhibition at the arachidonic acid or adenosine diphosphate receptor sites. For surgical patients with significant inhibition, dual therapy with DDAVP and platelet transfusion was employed. Study patients were compared with a group of historical controls, which were identified from a prospectively maintained registry and typically treated with empiric platelet transfusion.

RESULTS

Median age was 75 years (interquartile range 85-67) and 77 years (interquartile range 81-65) in the TEG-PM and control patient groups, respectively. Admission hemorrhage volumes were similar (10.7 cm³ [20.1] in patients with TEG-PM vs. 14.1 cm³ [19.7] in controls; p = 0.41). There were no significant differences in admission Glasgow Coma Scale, mechanism of trauma, or baseline comorbidities. A total of 57% of controls versus 10% of patients with TEG-PM (p < 0.001) were transfused platelets; 52% of intervention patients and 0% controls were treated with DDAVP. Expansion hemorrhage volumes were not significantly different (14.0 cm³ [20.2] patients with TEG-PM versus 13.6 cm³ [23.7] controls; p = 0.93). There was no significant difference in rates of clinical deterioration, delayed neurosurgical intervention, or late platelet transfusion between groups.

CONCLUSIONS

Among patients with hemorrhagic TBI prescribed preinjury antiplatelet therapy, our study suggests that the use of a TEG-PM algorithm may reduce platelet transfusions without a concurrent increase in clinically significant hematoma expansion. Further study is required to prove a causative relationship.

A Narrative Review of Postoperative Anticoagulation Therapy for Congenital Cardiac Disease

Congenital heart disease encompasses a range of cardiac birth defects. Some defects require early and complex surgical intervention and post-operative thromboprophylaxis primarily for valve, conduit, and shunt patency. Antiplatelet and anticoagulant management strategies vary considerably and may or may not align with recognized consensus practice guidelines. In addition, newer anticoagulant agents are being increasingly used in children, but these medications are not addressed in most consensus statements.

This narrative review evaluated the literature from 2011 through 2021 on the topic of postoperative thromboprophylaxis after congenital heart disease operations. The search was focused on the descriptions and results of pediatric studies for replacement and/or repair of heart valves, shunts, conduits, and other congenital heart disease operations. Wide variability in practice exists and, as was true a decade ago, few randomized controlled trials have been conducted. Aspirin, warfarin, and perioperative heparin remain the most commonly used agents with varying dosing, duration, and monitoring strategies, making comparisons difficult. Only recently have data on direct oral anticoagulants been published in children, suggesting evolving paradigms of care. Our findings highlight the need for more research to strengthen the evidence for standardized thromboprophylaxis strategies.

Aspirin resistance in infants with shunt-dependent congenital heart disease

INTRODUCTION

Patients with cyanotic heart disease are at an increased risk of developing thrombosis. Aspirin has been the mainstay of prophylactic anticoagulation for shunt-dependent patients with several reports of prevalent aspirin resistance, especially in neonates. We investigate the incidence of aspirin resistance and its relationship to thrombotic events and mortality in a cohort of infants with shunt-dependent physiology.

METHODS

Aspirin resistance was assessed using the VerifyNow™ test on infants with single-ventricle physiology following shunt-dependent palliation operations. In-hospital thrombotic events and mortality data were collected. Statistical analysis was performed to evaluate the effect of aspirin resistance on in-hospital thrombotic events and mortality risk.

RESULTS

Forty-nine patients were included with 41 of these patients being neonates. Six patients (12%) were aspirin resistant. A birth weight < 2500 grams was a significant factor associated with aspirin resistance (p = 0.04). Following a dose increase or additional dose administration, all patients with initial aspirin resistance had a normal aspirin response. There was no statistically significant difference between aspirin resistance and non-resistance groups with respect to thrombotic events. However, a statistically significant incidence of in-hospital mortality in the presence of thrombotic events was observed amongst aspirin-resistant patients (p = 0.04) in this study.

CONCLUSION

Low birth weight was associated with a higher incidence of aspirin resistance. Inadequate initial dosing appears to be the primary reason for aspirin resistance. The presence of both thrombotic events and aspirin resistance was associated with significantly higher in-hospital mortality indicating that these patients warrant closer monitoring.

A systematic review of the evidence supporting post-operative antithrombotic use following cardiopulmonary bypass in children with CHD

OBJECTIVES

To determine the optimal antithrombotic agent choice, timing of initiation, dosing and duration of therapy for paediatric patients undergoing cardiac surgery with cardiopulmonary bypass.

METHODS

We used PubMed and EMBASE to systematically review the existing literature of clinical trials involving antithrombotics following cardiac surgery from 2000 to 2020 in children 0-18 years. Studies were assessed by two reviewers to ensure they met eligibility criteria.

RESULTS

We identified 10 studies in 1929 children across three medications classes: vitamin K antagonists, cyclooxygenase inhibitors and indirect thrombin inhibitors. Four studies were retrospective, five were prospective observational cohorts (one of which used historical controls) and one was a prospective, randomised, placebo-controlled, double-blind trial. All included were single-centre studies. Eight studies used surrogate biomarkers and two used clinical endpoints as the primary endpoint. There was substantive variability in response to antithrombotics in the immediate post-operative period. Studies of warfarin and aspirin showed that laboratory monitoring levels were frequently out of therapeutic range (variably defined), and findings were mixed on the association of these derangements with bleeding or thrombotic events. Heparin was found to be safe at low doses, but breakthrough thromboembolic events were common.

CONCLUSION

There are few paediatric prospective randomised clinical trials evaluating antithrombotic therapeutics post-cardiac surgery; most studies have been observational and seldom employed clinical endpoints. Standardised, validated endpoints and pragmatic trial designs may allow investigators to determine the optimal drug, timing of initiation, dosing and duration to improve outcomes by limiting post-operative morbidity and mortality related to bleeding or thrombotic events.

Risk Factors of Thrombotic Complications and Antithrombotic Therapy in Paediatric Cardiosurgical Patients

The development of cardiosurgical care for paediatric and neonatal patients is undergoing the rapid growth. Complex, multi-stage reconstructive operations and the use of invasive monitoring are associated with high risk of venous and arterial thrombosis.

The cardiac surgery patient is inherently unique, since it requires controlled anticoagulation during cardiopulmonary bypass. Moreover, the most cardiovascular pediatric patients require antithrombotic measures over the perioperative period. In addition to medication support with the use of various groups of antithrombotic agents, vascular access management is justified in order to minimize the risk of thromboembolic complications, which can affect both the functional status, and common and inter-stage mortality.

The purpose of this review was to systematize the available data on risk factors contributing to the development of thrombotic complications in patients with congenital heart disease.

An information search was carried out using Internet resources (PubMed, Web of Science, eLibrary.ru); literature sources for period 2015–2020 were analysed. As a result of the analysis of the literature data age-dependent features of the haemostatic system, and associated with the defect pathophysiology, and undergone reconstructive interventions were described. The issues of pathophysiology of univentricular heart defects and risk factors associated with thrombosis were also covered.

Moreover, aspects of intraoperative anti-thrombotic support are discussed, as well as measures to prevent thromboembolic complications in this population.

Coordinated actions of haematologists, cardiologists, anaesthesiologists, intensivists, and cardiac surgeons will allow achieving a fine balance between risks of bleeding and thrombosis in the population of paediatric patients undergoing cardiovascular surgery. 

A systematic review of the evidence supporting post-operative medication use in congenital heart disease

BACKGROUND

Targeted drug development efforts in patients with CHD are needed to standardise care, improve outcomes, and limit adverse events in the post-operative period. To identify major gaps in knowledge that can be addressed by drug development efforts and provide a rationale for current clinical practice, this review evaluates the evidence behind the most common medication classes used in the post-operative care of children with CHD undergoing cardiac surgery with cardiopulmonary bypass.

METHODS

We systematically searched PubMed and EMBASE from 2000 to 2019 using a controlled vocabulary and keywords related to diuretics, vasoactives, sedatives, analgesics, pulmonary vasodilators, coagulation system medications, antiarrhythmics, steroids, and other endocrine drugs. We included studies of drugs given post-operatively to children with CHD undergoing repair or palliation with cardiopulmonary bypass.

RESULTS

We identified a total of 127 studies with 51,573 total children across medication classes. Most studies were retrospective cohorts at single centres. There is significant age- and disease-related variability in drug disposition, efficacy, and safety.

CONCLUSION

In this study, we discovered major gaps in knowledge for each medication class and identified areas for future research. Advances in data collection through electronic health records, novel trial methods, and collaboration can aid drug development efforts in standardising care, improving outcomes, and limiting adverse events in the post-operative period.

Viscoelastic Hemostatic Assays and Platelet Function Testing in Patients with Atherosclerotic Vascular Diseases

Platelets play crucial role in acute vascular atherosclerotic diseases, including myocardial infarction and stroke. Additionally, platelet aggregation is a key target of antiplatelet agents, forming the keystone of pharmacotherapy of various atherosclerotic cardiovascular diseases. Thromboelastography and thromboelastometry, representing currently available viscoelastic hemostatic assays (VHA), are designed as whole blood, real-time analyzers of clot formation and clot resolution. These assays could, in theory, overcome some limitations of currently available platelet function testing assays. This article reviews the current experience with the use of VHA for platelet function testing and for monitoring of the response to antiplatelet therapy.

Cangrelor PK/PD analysis in post-operative neonatal cardiac patients at risk for thrombosis

Essentials An optimal therapeutic strategy has yet to be established to prevent early shunt thrombosis. A phase 1 study of cangrelor was performed in neonates after palliation of congenital heart disease. PD endpoint of >90% platelet inhibition in 60% of patients was achieved at 0.5 µg/kg/min dosing. No serious adverse events related to drug administration were observed, including bleeding. ABSTRACT: Background Systemic-to-pulmonary artery shunt thrombosis is a significant cause of early postoperative mortality in neonates after palliation of congenital heart disease. In the context of thromboprophylaxis, an optimal therapeutic strategy has yet to be established before aspirin administration. Cangrelor, a fast-acting, reversible P2Y12 inhibitor, may fill this unmet need. Objectives To evaluate the pharmacokinetics (PK), pharmacodynamics (PD), and safety of cangrelor in neonates undergoing stage 1 palliation. Methods This prospective, open-label, single-arm study evaluated two cangrelor dosing cohorts following placement of a systemic-to-pulmonary artery shunt, right ventricle-to-pulmonary artery shunt, or ductal stent. Drug concentrations and platelet reactivity, assessed by light transmission aggregometry and in microfluidic assays (MF), were measured. Results Twenty-two patients were consented and 15 received a 1-hour infusion of cangrelor at either 0.5 µg/kg/min (cohort 1) or 0.25 µg/kg/min (cohort 2). Whereas the primary PD endpoint was achieved at the higher dose (ie, reduction in maximal platelet aggregation by ≥90% in 60% of participants), only 29% of those in cohort 2 attained this goal. Comparable and statistically significant results were obtained in MF assays (P < .0001 vs. baseline). Drug levels during infusion were 3-fold higher in cohort 1 vs. cohort 2 (P < .001). Most participants (70%) had undetectable drug levels by 10 minutes postinfusion with full recovery in platelet function at 1 hour. No drug-related bleeding events occurred. Conclusions Favorable PK/PD properties of cangrelor 0.5 µg/kg/min dosing and safety profile warrant further evaluation in neonates following palliative cardiac procedures.

Platelet Inhibition With IV Glycoprotein IIb/IIIa Inhibitor to Prevent Thrombosis in Pediatric Patients Undergoing Aortopulmonary Shunting

OBJECTIVES

Shunt thrombosis, a potential complication of aortopulmonary shunting, is associated with high mortality. Commonly used oral antiplatelet drugs such as aspirin demonstrate variable absorption and inconsistent antiplatelet effect in critically ill patients early after surgery. IV glycoprotein IIb/IIIa inhibitors are antiplatelet agents with rapid and reproducible effect that may be beneficial as a bridge to oral therapy.

DESIGN

Retrospective review of pediatric patients undergoing treatment with IV tirofiban. Discarded blood samples were used to determine pharmacokinetic parameters.

SETTING

Pediatric cardiac ICU at a single institution.

PATIENTS

Fifty-two pediatric patients (< 18 yr) undergoing surgical aortopulmonary shunt procedure who received tirofiban infusion as a bridge to oral aspirin.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Primary outcome measures were shunt thrombosis and bleeding events, whereas secondary outcomes included measurement of platelet inhibition by thromboelastography with platelet mapping and pharmacokinetic analysis (performed in a subset of 15 patients). Shunt thrombosis occurred in two of 52 patients (3.9%) after prophylaxis treatment with tirofiban; both thrombosis events occurred after discontinuation of the drug. One patient (1.9%) experienced bleeding complication during the infusion. A tirofiban bolus of 10 µg/kg and infusion of 0.15 µg/kg/min resulted in significantly increased platelet inhibition via adenosine diphosphate pathway (median 66% [43-96] pre-tirofiban compared with 97% [92-99%] at 2 hr; p < 0.05). Half-life of tirofiban in plasma was 142 ± 1.5 minutes, and the average steady-state concentration was 112 ± 62 ng/mL. Age and serum creatinine were significant covariates associated with systemic clearance. Dosing simulations were generated based upon one compartment model.

CONCLUSIONS

IV glycoprotein IIb/IIIa inhibitor as a bridge to oral antiplatelet therapy is safe in pediatric patients after aortopulmonary shunting. Dosing considerations should include both age and renal function. Randomized trials are warranted to establish efficacy compared with current anticoagulation practices.

Arterial Ischemic Stroke Secondary to Cardiac Disease in Neonates and Children

OBJECTIVE

We describe the risk factors for peri-procedural and spontaneous arterial ischemic stroke (AIS) in children with cardiac disease.

METHODS

We identified children with cardiac causes of AIS enrolled in the International Pediatric Stroke Study registry from January 2003 to July 2014. Isolated patent foramen ovale was excluded. Peri-procedural AIS (those occurring during or within 72 hours of cardiac surgery, cardiac catheterization, or mechanical circulatory support) and spontaneous AIS that occurred outside of these time periods were compared.

RESULTS

We identified 672 patients with congenital or acquired cardiac disease as the primary risk factor for AIS. Among these, 177 patients (26%) had peri-procedural AIS and 495 patients (74%) had spontaneous AIS. Among non-neonates, spontaneous AIS occurred at older ages (median 4.2 years, interquartile range 0.97 to 12.4) compared with peri-procedural AIS (median 2.4 years, interquartile range 0.35 to 6.1, P < 0.001). About a third of patients in both groups had a systemic illness at the time of AIS. Patients who had spontaneous AIS were more likely to have a preceding thrombotic event (16 % versus 9 %, P = 0.02) and to have a moderate or severe neurological deficit at discharge (67% versus 33%, P = 0.01) compared to those with peri-procedural AIS.

CONCLUSIONS

Children with cardiac disease are at risk for AIS at the time of cardiac procedures but also outside of the immediate 72 hours after procedures. Many have acute systemic illness or thrombotic event preceding AIS, suggesting that inflammatory or prothrombotic conditions could act as a stroke trigger in this susceptible population.

Patient Blood Management in Pediatric Cardiac Surgery: A Review

Efforts to reduce blood product transfusions and adopt blood conservation strategies for infants and children undergoing cardiac surgical procedures are ongoing. Children typically receive red blood cell and coagulant blood products perioperatively for many reasons, including developmental alterations of their hemostatic system, and hemodilution and hypothermia with cardiopulmonary bypass that incites inflammation and coagulopathy and requires systemic anticoagulation. The complexity of their surgical procedures, complex cardiopulmonary interactions, and risk for inadequate oxygen delivery and postoperative bleeding further contribute to blood product utilization in this vulnerable population. Despite these challenges, safe conservative blood management practices spanning the pre-, intra-, and postoperative periods are being developed and are associated with reduced blood product transfusions. This review summarizes the available evidence regarding anemia management and blood transfusion practices in the perioperative care of these critically ill children. The evidence suggests that adoption of a comprehensive blood management approach decreases blood transfusions, but the impact on clinical outcomes is less well studied and represents an area that deserves further investigation.

High acetylsalicylic acid dosing in infants after modified Blalock-Taussig shunt

OBJECTIVE

Shunt-related adverse events are frequent in infants after modified Blalock-Taussig despite use of acetylsalicylic acid prophylaxis. A higher incidence of acetylsalicylic acid-resistance and sub-therapeutic acetylsalicylic acid levels has been reported in infants. We evaluated whether using high-dose acetylsalicylic acid can decrease shunt-related adverse events in infants after modified Blalock-Taussig.

METHODS

In this single-centre retrospective cohort study, we included infants ⩽1-year-old who underwent modified Blalock-Taussig placement and received acetylsalicylic acid in the ICU. We defined acetylsalicylic acid treatment groups as standard dose (⩽7 mg/kg/day) and high dose (⩾8 mg/kg/day) based on the initiating dose.

RESULTS

There were 34 infants in each group. Both groups were similar in age, gender, cardiac defect type, ICU length of stay, and time interval to second stage or definitive repair. Shunt interventions (18 versus 32%, p=0.16), shunt thrombosis (14 versus 17%, p=0.74), and mortality (9 versus 12%, p=0.65) were not significantly different between groups. On multiple logistic regression analysis, single-ventricle morphology (odds ratio 5.2, 95% confidence interval of 1.2-23, p=0.03) and post-operative red blood cells transfusion ⩾24 hours [odds ratio 15, confidence interval of (3-71), p&lt;0.01] were associated with shunt-related adverse events. High-dose acetylsalicylic acid treatment [odds ratio 2.6, confidence interval of (0.7-10), p=0.16] was not associated with decrease in these events.

CONCLUSIONS

High-dose acetylsalicylic acid may not be sufficient in reducing shunt-related adverse events in infants after modified Blalock-Taussig. Post-operative red blood cells transfusion may be a modifiable risk factor for these events. A randomised trial is needed to determine appropriate acetylsalicylic acid dosing in infants with modified Blalock-Taussig.

Prevalence of aspirin resistance by thromboelastography plus platelet mapping in children with CHD: a single-centre experience

RationaleAspirin resistance has been reported in up to 80% of children with cardiovascular defects undergoing surgery. Because of a patient who had embolic stroke while on therapeutic aspirin dose but in whom aspirin resistance was present on his thromboelastography platelet mapping, we chose to obtain thromboelastography platelet mapping on cardiac patients on aspirin to assess their risk. OBJECTIVES: This study evaluates aspirin resistance noted in these patients and their characteristics.Methods and resultsThis is a retrospective study of 25 patients taking aspirin for a month at therapeutic dose. In total, 11 female patients were enrolled. Ages in all subjects were 5 months to 27 years. A total of 19 patients had a Fontan surgery. Three had a cavopulomanary anastomosis, one had a hybrid procedure, and two had coronary anomalies. Compliance was assessed at the time of the clinic visit. Aspirin resistance was defined as platelet inhibition below 50%. Variables evaluated were level of platelet inhibition, age, body mass index, and gender.

P2Y12 Receptor Function and Response to Cangrelor in Neonates With Cyanotic Congenital Heart Disease

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Platelets from neonatal patients with cyanotic congenital heart disease have a nearly identical response to adenosine diphosphate activation and P2Y₁₂ receptor blockade with cangrelor as their adult counterparts.

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Integrating high-throughput technologies with unique biological platforms can provide considerable insight into the potential clinical use of antiplatelet agents for neonatal and pediatric patients at risk for thrombosis.

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Cangrelor may prove to be an effective antithrombotic drug with pharmacological properties well suited for use in the immediate post-operative period for neonates palliated with systemic-to-pulmonary artery shunts.

Shunt thrombosis remains a major cause of morbidity and mortality, especially during the initial palliation for single-ventricle physiology. The authors present evidence that the P2Y₁₂ inhibitor cangrelor may fill a therapeutic void in thromboprophylaxis. They base this theory on results showing that platelets from neonatal patients with cyanotic congenital heart disease have a robust response to adenosine diphosphate and are amenable to P2Y₁₂ inhibition with cangrelor. Unique to this study was their ability to establish drug efficacy in an avatar mouse model that permits the in vivo evaluation of human platelet–mediated thrombus formation illustrating that this P2Y₁₂ inhibitor yields the intended biological response.

Variability of antithrombotics use in patients with hypoplastic left heart syndrome and its variants following first- and second-stage palliation surgery: a national report using the National Pediatric Cardiology Quality Improvement Collaborative registry

Purpose Patients with hypoplastic left heart syndrome and its variants following palliation surgery are at risk for thrombosis. This study examines variability of antithrombotic practice, the incidence of interstage shunt thrombosis, and other adverse events following Stage I and Stage II palliation within the National Pediatric Cardiology Quality Improvement Collaborative registry.

METHODS

We carried out a multicentre, retrospective review using the National Pediatric Cardiology Quality Improvement Collaborative registry including patients from 2008 to 2013 across 52 surgical sites. Antithrombotic medications used at Stage I and Stage II discharge were evaluated. Variability of antithrombotics use at the individual patient level and intersite variability, incidence of shunt thrombosis, and other adverse events such as cardiac arrest, seizure, stroke, and need for cardiac catheterisation intervention in the interstage period were identified. Antithrombotic strategies for hybrid Stage I patients were evaluated but they were excluded from the variability and outcomes analysis.

RESULTS

A total of 932 Stage I and 923 Stage II patients were included in the study: 93.8% of Stage I patients were discharged on aspirin and 4% were discharged on no antithrombotics, and 77% of Stage II patients were discharged on aspirin and 17.5% were discharged on no antithrombotics. Only three patients (0.2%) presented with interstage shunt thrombosis. The majority of patients who died during interstage or required shunt dilation and/or stenting were discharged home on aspirin.

CONCLUSION

Aspirin is the most commonly used antithrombotic following Stage I and Stage II palliation. There is more variability in the choice of antithrombotics following Stage II compared with Stage I. The incidence of interstage shunt thrombosis and associated adverse events was rare.

Platelet Inhibition in Shunted Infants on Aspirin at Short and Midterm Follow-Up

There are few data to guide aspirin therapy to prevent shunt thrombosis in infants. We aimed to determine if aspirin administered at conventional dosing in shunted infants resulted in ≥50% arachidonic acid (AA) inhibition in short and midterm follow-up using thromboelastography with platelet mapping (TEG-PM) and to describe bleeding and thrombotic events during follow-up. We performed a prospective observational study of infants on aspirin following Norwood procedure, aortopulmonary shunt alone, or cavopulmonary shunt surgery. We obtained TEG-PM preoperatively, after the third dose of aspirin, at the first postoperative clinic visit, and 2-8 months after surgery. The primary outcome was the proportion of subjects with ≥50% AA inhibition on aspirin. All bleeding and thrombotic events were collected. Of 24 infants analyzed, 13% had ≥50% AA inhibition at all designated time points after aspirin initiation; 38% had ≥50% AA inhibition after the third aspirin dose of aspirin, 60% at the first postoperative clinic visit, and 26% 2-8 months after surgery. Bleeding events occurred in eight subjects, and two had a thrombotic event. Bleeding events were associated with greater AA inhibition just prior to starting aspirin (p = 0.02) and after the third dose of aspirin (p = 0.04), and greater ADP inhibition before surgery (p = 0.03). The majority of infants failed to consistently have ≥50% AA inhibition when checked longitudinally postoperatively. Preoperative TEG-PM may be useful in identifying infants at higher risk of bleeding events on aspirin in the early postoperative period. Further research is needed to guide antiplatelet therapy in this population.

Risk Factors, Prophylaxis, and Treatment of Venous Thromboembolism in Congenital Heart Disease Patients

Congenital heart disease (CHD) is a common condition in the pediatric population, affecting up to 1% of all live births (i.e., around 40,000 newborns/year in the United States). Although CHD does have a wide range of severity, by the age of 5 years approximately 80% of patients will require at least one surgical intervention to achieve a complete/palliative cardiac repair. Today, in light of their much-improved surgical survival, the care of these patients focuses on morbidity prevention and/or treatment. One such morbidity has been the increased frequency of thrombotic occlusions [e.g., cardioembolic arterial ischemic strokes; arterial, cardiac, and/or newly created shunt thrombosis; venous thromboembolism (VTE)]. Patients with CHD are at high risk of developing thrombosis due to the disruption of blood flow, CHD-related coagulopathy, inflammation, and/or platelet activation secondary to extracorporeal circulation support required during open-heart surgery or as a bridge to recovery, which can increase thrombus formation. In this article, we will discuss how the coagulation system is altered in patients with CHD in regard to the patient's anatomy, procedures they undergo to correct their congenital heart defect, and other risk factors that may increase their thrombotic risk, focusing on VTE. We will also discuss the most recently published reports pertaining to guidelines on prophylaxis and treatment of VTE in this population. Finally, we will briefly address the long-term VTE outcomes for patients with CHD.