Factors Affecting the Discrepancy Between Coagulation Times on Extracorporeal Circulation Using Unfractionated Heparin in Children and Young Adults.

In unfractionated heparin (UFH) monitoring during extracorporeal circulation, the traditional measures of activated clotting time (ACT) or activated partial thromboplastin time (APTT) may diverge, confounding anticoagulant adjustments. We aimed to explore the factors explaining this discrepancy in children and young adults. This retrospective observational study, conducted at an urban regional tertiary hospital, included consecutive pediatric patients who received UFH during extracorporeal circulation (continuous kidney replacement therapy or extracorporeal membrane oxygenation) between April 2017 and March 2021. After patients whose ACT and APTT were not measured simultaneously or who were also taking other anticoagulants were excluded, we analyzed 94 samples from 23 patients. To explain the discrepancy between ACT and APTT, regression equations were created using a generalized linear model (family = gamma, link = logarithmic) with ACT as the response variable. Other explanatory variables included age, platelet count, and antithrombin. Compared to APTT alone as an explanatory variable, the Akaike information criterion and pseudo-coefficient of determination improved from 855 to 625 and from 0.01 to 0.42, respectively, when these explanatory variables were used. In conclusion, we identified several factors that may explain some of the discrepancy between ACT and APTT in the routinely measured tests. Evaluation of these factors may aid in appropriate adjustments in anticoagulation therapy.

Anticoagulation Strategies in Pediatric Cardiopulmonary Bypass, Weight-Based vs. Concentration-Based Approaches.

Pediatric patients undergoing cardiopulmonary bypass (CPB) require adequate anticoagulation to combat hemostatic activation. Heparin is used to bind and catalyze antithrombin III (ATIII) that works to inhibit clot formation. To dose heparin, a weight-based (WB) or patient-specific concentration-based (PSCB) method can be used. The WB protocol calculates the dose based on the patients' weight and uses an activated clotting time (ACT) test to ensure anticoagulation. The ACT has limitations during CPB especially for pediatric patients who have immature hemostatic systems. The PSCB method predicts the patients' response to heparin by projecting a heparin dose-response (HDR) curve. Some investigators have found benefit to using the PSCB method but further investigation into how well the HDR predicts the heparin response is needed. A literature review was conducted for studies that looked at heparin management strategies in pediatric CPB patients between 1992 and 2020. Articles that focused on pediatric physiology, heparin management strategies, and anticoagulation were included. Articles older than 1990 were excluded. The literature review highlights that utilizing the PSCB approach more adequately anticoagulated patients. The WB protocol was found to have several flaws due to its reliance on the ACT, especially in infants. The results show that further investigation is needed to understand why there is benefit to using the PSCB approach. Observing the association between the HDR curve and subsequent heparin concentrations could determine how accurately it predicts the patients' response to heparin and why there is benefit to using this method.

Activated Clotting Time as a Marker of Inflammation in Hospitalized Patients.

Inflammation and coagulation pathways are implicated in circulatory disease, but their interaction has not been completely deciphered yet. In this study, we investigated the association of coagulation and inflammation indices (activated clotting time [ACT], C-reactive protein, neutrophils) in hospitalized patients. Blood samples were drawn from consecutive patients at admission and at 48 hours for the assessment of the aforementioned parameters (n = 63). Healthy controls matched for sex and age were also examined (n = 39). Activated clotting time positively correlated with CRP on admission (r = 0.354, P = .005), while the correlation was more robust on the second day (r = 0.775, P < .001). Activated clotting time was significantly more prolonged in patients with abnormal CRP or abnormal absolute neutrophil count compared to patients with normal inflammatory markers (U = 55.0, P < .001 and U = 310.5, P = .035, respectively). At 48 hours, a positive relationship was observed between ACT and relative percentage of neutrophils (r = 0.358, P = .004). These findings suggest a link between ACT and inflammation indices for the first time in humans. Further research is needed to determine whether these interrelations can be used to improve patient management.

Clinical controversies in anticoagulation monitoring and antithrombin supplementation for ECMO.

During extracorporeal membrane oxygenation (ECMO), a delicate balance is required to titrate systemic anticoagulation to prevent thrombotic complications within the circuit and prevent bleeding in the patient. Despite focused efforts to achieve this balance, the frequency of both thrombotic and bleeding events remains high. Anticoagulation is complicated to manage in this population due to the complexities of the hemostatic system that are compounded by age-related developmental hemostatic changes, variable effects of the etiology of critical illness on hemostasis, and blood-circuit interaction. Lack of high-quality data to guide anticoagulation management in ECMO patients results in marked practice variability among centers. One aspect of anticoagulation therapy that is particularly challenging is the use of antithrombin (AT) supplementation for heparin resistance. This is especially controversial in the neonatal and pediatric population due to the baseline higher risk of bleeding in this cohort. The indication for AT supplementation is further compounded by the potential inaccuracy of the diagnosis of heparin resistance based on the standard laboratory parameters used to assess heparin effect. With concerns regarding the adverse impact of bleeding and thrombosis, clinicians and institutions are faced with making difficult, real-time decisions aimed at optimizing anticoagulation in this setting. In this clinically focused review, the authors discuss the complexities of anticoagulation monitoring and therapeutic intervention for patients on ECMO and examine the challenges surrounding AT supplementation given both the historical and current perspectives summarized in the literature on these topics.

Whole-blood hypocoagulable profile correlates with a greater risk of death within 28 days in patients with severe sepsis.

BACKGROUND: Hypocoagulability and impaired platelet function have been associated with a high risk of death in sepsis. The aim of this cohort study was to determine whether sepsis-induced hypocoagulability and platelet dysfunction (assessed by ROTEM® and MULTIPLATE®, respectively) are increased in sepsis patients who died within 28 days after diagnosis compared with patients who died between 29 and 90 days after diagnosis. METHODS: Consecutive patients admitted to the intensive care unit of Padova University Hospital from March 2015 to March 2018 for severe sepsis were considered. We collected blood samples from all patients to determine ROTEM® and MULTIPLATE® parameters. Each enrolled patient underwent a 90-day follow-up and the mortality rate was recorded. RESULTS: Of 120 patients, 36 (30%) died within 28 days post-diagnosis (Group A), 23 (19%) died between days 29 and 90 post-diagnosis (Group B), and 61 (51%) were alive after 90 days (survivors). The clotting time in the ROTEM® test and clot formation time in the EXTEM test were significantly more prolonged in Group A than in B. Both groups showed a significantly higher hypocoagulability than survivors in the EXTEM test. MULTIPLATE® platelet function analysis showed that platelet function was significantly lower in Group A than in Group B. CONCLUSIONS: The present study showed that the combination of thromboelastometry and impedance aggregometry may help identifying sepsis patients at high risk of short-term death. Larger studies are warranted to corroborate our results.

Whole Blood Point-of-Care Testing for Incomplete Reversal With Idarucizumab in Supratherapeutic Dabigatran.

BACKGROUND: Incomplete reversal with a recommended 5-g dose of idarucizumab has been reported in patients with excessively high dabigatran concentrations. A timely detection of reversal failure after idarucizumab using whole blood (WB) coagulation testing is clinically useful. The aims of this study were to determine residual dabigatran activity after idarucizumab on thrombin generation (TG) using in vitro supratherapeutic dabigatran models and to compare 4 WB point-of-care tests (activated partial thromboplastin time [aPTT], prothrombin time [PT], and 2 thromboelastometry tests) with the TG results. METHODS: Blood samples from 12 healthy volunteers were spiked in vitro with 0-5000 ng/mL of dabigatran. Dabigatran reversal was evaluated by adding 1000 µg/mL of idarucizumab (Praxbind) to dabigatran-spiked samples, which reflect the administration of 5-g idarucizumab to a 70-kg patient. Residual dabigatran activity was assessed using the calibrated automated TG (Thrombinoscope) in platelet-poor plasma samples. The TG results were compared with WB aPTT (DRIHEMATO APTT-S) and PT (DRIHEMATO PT-S) using CG02N analyzer, thromboelastometry (ROTEM) triggered by ellagic acid (INTEM) and tissue factor (EXTEM). RESULTS: At a therapeutic concentration of dabigatran (200 ng/mL), the lag time was prolonged, and peak TG was decreased. The effects of dabigatran on TG were increased up to 1000 ng/mL, and TG was obliterated at higher supratherapeutic dabigatran levels (P < .001 versus control, respectively). TG was fully restored with idarucizumab when dabigatran was ≤2000 ng/mL, but residual anticoagulant activity was observed at higher dabigatran levels. Dabigatran prolonged WB aPTT and PT concentration dependently, and residual prolongations were observed when idarucizumab was added to 3000 or 5000 ng/mL of dabigatran (P < .001 versus control, respectively). In contrast, both INTEM and EXTEM clotting times were reversed toward reference ranges at all dabigatran concentrations when idarucizumab was added. CONCLUSIONS: Our data indicate that the recommended dose of idarucizumab may not restore TG completely with excessively elevated concentrations of dabigatran. All WB measurements with aPTT, PT, and thromboelastometry predicted supratherapeutic dabigatran concentrations, whereas those tests varied in sensitivity to residual anticoagulant activity after reversal. WB aPTT corresponded well with plasma TG changes among those measurements, but the use of thromboelastometry may overestimate the effect of idarucizumab. Caution should be exercised before extrapolating in vitro point-of-care data to the clinical monitoring of dabigatran reversal.

DTI/DXI interferences with global coagulation tests in emergency hospital admissions - Results of the prospective Dresden NOAC Registry (NCT01588119).

BACKGROUND: Depending on test assays and the time of last DOAC intake, direct thrombin inhibitors (DTI) and direct FXa inhibitors (DXI) may or may not affect prothrombin time (PT), international normalized ratio (INR) or activated thromboplastin time (aPTT) but the clinical impact is unknown. METHODS: Using data from the Dresden NOAC Registry, we evaluated the impact of DOAC on first PT, INR or aPTT tests during emergency hospitalizations of DTI/DXI patients and the assay performance across 50 coagulation laboratories. RESULTS: In 724 emergency admissions (77 DTI; 647 DXI), 490 cases (67.7%) had a reported last DOAC intake within 12 h before blood sampling. INR and PT were elevated above the upper limit of normal (ULN) in >65% of all cases and aPTT was elevated in 45%. On the other hand, >30% of all cases had normal values of INR, PR and aPTT despite a DOAC intake within the last 12 h. Assay performance for detecting or ruling out therapeutic DOAC levels was highly variable and, overall, insufficient to guide clinical decisions. DOAC specific testing was performed in <10% of all cases. CONCLUSION: Many DOAC recipients present with elevated PT, INR or aPTT during emergency admissions but false negative values within 12 h of last intake as well as elevated values beyond 24 h after last DOAC intake are common. Both scenarios may result in clinical misinterpretation and, potentially, in patient harm, also because DOAC specific testing is rarely performed in emergency settings.

Case report of patient blood managment guided by rotational thromboelastometry in Mexico and literature review.

INTRODUCTION: Thromboelastometry evaluates viscoelastic changes in the coagulation process. It offers a graphic representation of the formation of the coagulum, its stability and the presence of lysis. OBJECTIVE: This first case of transfusion management guided by thromboelastography in Mexico and we conducted a review of the literature. METHOD: A metasearch search was performed (PubMed, Scielo, Medigraphic) with the words thromboelastometry, coagulopathy, transfusion medicine and the most influential works were included. CONCLUSIONS: The rotational thromboelastometry is a diagnostic tool that graphs the functionality of the clot, for a directed and individualized management of the coagulopathy associated with bleeding.

INTRODUCCIÓN: La tromboelastometría evalúa los cambios viscoelásticos en el proceso de coagulación. Ofrece una representación gráfica de la formación del coágulo, su estabilidad y la presencia de lisis. OBJETIVO: Se notifica el primer caso de manejo transfusional guiado por tromboelastografía en México con revisión de la bibliografía. MÉTODO: Se realizó una búsqueda en metabuscadores (PubMed, Scielo, Medigraphic) con las palabras tromboelastometría, coagulopatía y medicina transfusional y se incluyeron los trabajos más influyentes. CONCLUSIONES: La tromboelastometría rotacional es una herramienta diagnóstica que grafica la funcionalidad del coágulo para un manejo dirigido e individualizado de la coagulopatía relacionada con ­hemorragia.

An in vitro study of coagulation properties in refrigerated whole blood and reconstituted whole blood.

OBJECTIVE: Fresh whole blood (WB) has been used in military applications and cardiac surgery. We undertook a study of the coagulation properties of refrigerated WB stored for 21 days and compared them with the properties of reconstituted WB. STUDY DESIGN AND METHODS: Ten WB units were obtained from healthy volunteer donors and stored at 4 ± 2°C. Samples were obtained on Days 1, 2, 4, 6, 8, 10, 14 and 21 from the WB units. Ten units of reconstituted WB were prepared with a ratio of red cells, platelets and plasma of 1:1:1. Tests included complete blood count, electrolyte, routine coagulation, blood coagulation factor and thromboelastography. RESULTS: There was a progressive decline in Hb, WBC, PLT, sodium and coagulation factors but a progressive increase in APTT, PT and potassium in WB. The concentrations of factor (F)V and FVIII as well as FII and FX of WB were higher before Days 4, 2, 8 and 14, respectively, compared with the concentrations of reconstituted WB. The concentrations of FVII, FIX, FXI and FXII in WB were found to be equal to or higher than those in reconstituted WB throughout the course of 21 days. TEG variables in all WB units were normal throughout the course of 10 days. The mean PT and APTT of WB were lower than those of reconstituted WB before Days 14 and 10, respectively. CONCLUSION: This study suggests that the coagulation properties of refrigerated WB were equal to or superior to those of reconstituted WB for a minimum of 10 days.

Assessment of Heparin Anticoagulation Measured Using i-STAT and Hemochron Activated Clotting Time.

OBJECTIVE: Adequate anticoagulation, measured using activated clotting time (ACT), is important during vascular and cardiac surgeries. Unfractionated heparin is the most common anticoagulant used. The purpose of this analysis was to compare the i-STAT ACT (iACT) to the Hemochron ACT (hACT), both of which were then compared to anti-factor Xa (anti-Xa) assay, a representation of heparin level and activity. DESIGN: Prospective study. SETTING: Tertiary care cardiovascular center. PARTICIPANTS: Eleven consecutive elective adult cardiac surgical patients. INTERVENTIONS: Prior to cardiopulmonary bypass, ACTs were measured using i-STAT and Hemochron technologies and compared to each other and to anti-Xa assay prior to and during a cumulative administration of heparin. Data were compared using bias analyses. MEASUREMENTS AND MAIN RESULTS: Heparin (300 U/kg) was administered in quarterly doses. Coagulation labs were collected prior to and 3 minutes after each quarterly dose of heparin. The baseline ACTs for i-STAT and Hemochron were 147 and 142 seconds, respectively. A significant association was found between iACT and hACT (p = 0.002). The iACT measurements underestimated hACT at ACT levels >180 seconds or anti-Xa levels >0.75 U/mL. No significant difference was found between ACT data at anti-Xa levels <0.5 U/mL. CONCLUSION: There was a good association between the iACT and hACT; however, the 2 tests are not equivalent. Overall, the iACT underestimated the hACT. Agreement between the ACT technologies was good at lower ACTs and anti-Xa levels, but declined with an anti-Xa >0.75 U/mL.

Clinical Evaluation of Measuring the ACT during Elective Cardiac Surgery with Two Different Devices.

Unfractionated heparin is the mainstay of anticoagulation during cardiac surgery on cardiopulmonary bypass (CPB) due to its low cost, quick onset, and ease of reversal. Since over 30 years, the activated clotting time (ACT) has been used to assess the level of heparin activity both before and after CPB. We compared two different methods of measuring the ACT: i-STAT, which uses amperometric detection of thrombin cleavage, and Hemochron Jr, which is based on detecting viscoelastic changes in blood. We included 402 patients from three institutions (Papworth Hospital, Cambridge, UK; Groote Schuur, Cape Town, South Africa; University Hospital Basel, Basel, Switzerland) undergoing elective cardiac surgery on CPB in our study. We analyzed duplicate samples on both devices at all standard measuring points during the procedure. The correlation coefficient between two Hemochron and two i-STAT devices was .9165 and .9857, respectively. The within-subject coefficient of variation (WSCV) ranged from 8.2 to 13.6% for the Hemochron and from 4.1 to 9.1% for the i-STAT. We found that the number of occasions where one of the duplicate readings was >1,000 seconds while the other was below or close to the clinically significant threshold of 400 seconds were higher for the Hemochron. We found the i-STAT to systematically return higher measurements. We conclude that the i-STAT provides a more reliable test for heparin activity and assesses safe anticoagulation during cardiac surgery on pump. The fact the that the i-STAT reads higher than the Hemochron leads to the recommendation to validate the methods against each other before changing devices.

Adjusted calculation model of heparin management during cardiopulmonary bypass in obese patients: A randomised controlled trial.

BACKGROUND: Anticoagulation during cardiopulmonary bypass (CPB) is usually adapted to total body weight (TBW). This may be inaccurate in obese patients and lead to heparin overdose with a risk of bleeding. OBJECTIVES: To validate the efficacy and safety of an adjusted calculation model of heparin dosing based on ideal body weight (IBW) rather than TBW in obese CPB patients, with an expected target mean plasma heparin concentration of 4.5 IU ml after onset of CPB in the experimental group. DESIGN: Randomised controlled study. SETTING: University hospital. PATIENTS: Sixty obese patients (BMI ≥ 30 kg m) scheduled for CPB were included from January to June 2016. INTERVENTIONS: Patients received a bolus dose of unfractionated heparin of either 300 IU kg of TBW or 340 IU kg of IBW before onset of CPB. Additional adjusted boluses were injected to maintain an activated clotting time (ACT) of at least 400 s. MAIN OUTCOME MEASURES: Plasma heparin concentration and ACT were measured at different time points. Total heparin doses and transfusion requirements were recorded. RESULTS: The target heparin concentration of 4.5 IU ml was reached in the IBW group at the onset of CPB and maintained at all time points during CPB. Heparin concentrations were significantly higher in the TBW group after the bolus (6.52 ±â€Š0.97 vs. 4.54 ±â€Š1.13 IU ml, P < 0.001) and after cardioplegia (5.10 ±â€Š1.03 vs. 4.31 ±â€Š1.00 IU ml, P = 0.02). Total heparin doses were significantly higher in the TBW group. Mean ACT was significantly lower in the IBW group but remained over 400 s during CPB. The correlation between heparin and ACT was poor. Peri-operative bleeding and transfusion requirements were comparable. No thrombotic event occurred in the CPB circuit. CONCLUSION: The current IBW-adjusted regimen of heparin administration may be used efficiently in obese CPB patients, thereby avoiding overdose which cannot be accurately assessed by ACT monitoring alone. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02675647.

Delayed double reading of whole blood clotting test (WBCT) results at 20 and 30 minutes enhances diagnosis and treatment of viper evenomation

The whole blood clotting test (WBCT) is a simple test of coagulation that is often used in the assessment, diagnosis, and therapeutic monitoring of snakebite patients in sub-Saharan Africa. WBCT requires only a clean glass tube and several milliliters of venous blood and is ideal for use in poorly equipped health centers throughout the rural areas where 95% of snakebites occur. However, questions surrounding the accuracy and reliability of the test remain unanswered due to variations in testing conditions and a lack of comparative research with which to validate them. This is the first study to evaluate WBCT results at both 20-min (WBCT20) and 30-min (WBCT30) reading times in the same group of snakebite patients. Methods In order to define the best reading time, the authors compared the results of serial WBCT evaluation at both 20 and 30 min after collection in 23 patients treated for snake envenomation in Bembèrèkè, northern Benin. Results WBCT results were identical at both reading times in patients without coagulopathy or when coagulation was restored permanently following a single dose of antivenom. Out of 17 patients with coagulopathy, 14 showed discrepancies between WBCT20 and WBCT30 results in at least one pair of serial evaluations. These could be completely contradictory results (e.g. normal clot at WBCT20 and no clot at WBCT30) or a marked difference in the quality of the clot (e.g. no clotting activity at WBCT20 and an unstable partial clot at WBCT30)...

Changes in heparin dose response slope during cardiac surgery: possible result in inaccuracy in predicting heparin bolus dose requirement to achieve target ACT.

INTRODUCTION: The substantial interpatient variability in heparin requirement has led to the use of a heparin dose response (HDR) technique. The accuracy of Hepcon-based heparin administration in achieving a target activated clotting time (ACT) using an HDR slope remains controversial. METHODS: We prospectively studied 86 adult patients scheduled for cardiac surgery requiring cardiopulmonary bypass. The total dose of calculated heparin required for patient and pump priming was administered simultaneously to achieve a target ACT of 450 s for HDR on the Hepcon HMS system. Blood samples were obtained after the induction of anesthesia, at 3 min after heparin administration and after the initiation of CPB to measure kaolin ACT, HDR slope, whole-blood heparin concentration based on the HDR slope and anti-Xa heparin concentration, antithrombin and complete blood count. RESULTS: The target ACT of 450 s was not achieved in 68.6% of patients. Compared with patients who achieved the target ACT, those who failed to achieve their target ACT had a significantly higher platelet count at baseline. Correlation between the HDR slope and heparin sensitivity was poor. Projected heparin concentration and anti-Xa heparin concentration are not interchangeable based on the Bland-Altman analysis. CONCLUSION: It can be hypothesized that the wide discrepancy in HDR slope versus heparin sensitivity may be explained by an inaccurate prediction of the plasma heparin level and/or the change in HDR of individual patients, depending on in vivo factors such as extravascular sequestration of heparin, decreased intrinsic antithrombin activity level and platelet count and/or activity.

Whole blood coagulation assays ROTEM and T-TAS to monitor dabigatran treatment.

BACKGROUND: A rapid and reliable assessment of the dabigatran effect is desirable in dabigatran treated patients with uncontrolled bleeding or before acute surgery. OBJECTIVE: To evaluate how the viscoelastic point-of-care test Rotational thromboelastometry (ROTEM) and Total Thrombus-formation system (T-TAS), which studies thrombus formation under flowing conditions, correlate with dabigatran concentrations in patients with atrial fibrillation (AF). METHOD: ROTEM using the reagents In-tem, Ex-tem, Fib-tem or low tissue factor concentration (TF), and T-TAS with the AR-chip (shear rate 600s-1, representing flow in large arteries) were investigated in whole blood samples. Plasma concentrations were determined by mass spectrometry (LC-MS/MS) at trough and post-dose in 30 patients on dabigatran 150mg BID. RESULTS: Median plasma dabigatran concentrations at trough were 86ng/mL (29-150) and post-dose (2.8h after ingestion) 175ng/mL (67-490). The ROTEM clotting time (CT) correlated strongly with dabigatran concentrations when activated with the reagents Ex-tem (r=0.92, p<0.01) and Fib-tem (r=0.93, p<0.01), while with In-tem and low TF the correlation was weaker (r=0.72 and r=0.36, p<0.01). There were significant but weaker correlations also between dabigatran concentrations and T-TAS variables (r-values 0.39-0.41, p<0.01), aPTT (r=0.70, p<0.01) and PT-INR (r=0.43, p<0.01) respectively. CONCLUSIONS: ROTEM Ex-tem and Fib-tem CT shows a strong correlation with dabigatran concentrations in real-life AF-patients, and results are obtained within minutes. This could make ROTEM useful in acute situations. T-TAS detect differences in hemostasis caused by dabigatran, but the relationships to plasma concentrations of dabigatran are weaker than for ROTEM CT with the settings used in this study.

Point-of-care testing of activated clotting time in the ICU: is it relevant?

BACKGROUND: Over the past 50 years there have been significant advances in both the clinical techniques and equipment used in the intensive care environment. One traditionally used point-of-care test is activated clotting time (ACT), a coagulation test primarily used during cardiopulmonary bypass surgery to monitor the anticoagulation effects of heparin. The ACT test has since emerged into the intensive care environment to guide clinical assessment and management of haemostasis in postoperative cardiac patients. OBJECTIVES: The aim of this integrative systematic review was to critique the available research evaluating the effectiveness of ACT point-of-care testing in the intensive care unit for adult patients following cardiopulmonary bypass and cardiac surgery and any impacts this may have on nursing care. METHODS: A systematic search of Medline, CINAHL and PubMed was undertaken. RESULTS: The search identified five research papers reporting on the use of ACT point-of-care testing in the intensive care unit for adult cardiac surgical patients. Meta-analysis was not performed due to the lack of homogeneity between the papers included. CONCLUSIONS: There was a lack of clear evidence for the use of the ACT point-of-care test after cardiac surgery in the intensive care environment. This review has highlighted that conventional laboratory tests are generally more accurate and reliable than this point-of-care test in guiding nursing care management.

Relation of Activated Clotting Times During Percutaneous Coronary Intervention to Outcomes.

Monitoring anticoagulation using the activated clotting time (ACT) in patients treated with heparin and undergoing percutaneous coronary intervention (PCI) is one of the most frequently used tests in invasive cardiology. However, despite its widespread use and guideline endorsement, uncertainty remains regarding the association of ACT with outcomes in contemporary practice. We reviewed all PCI procedures performed at the Mayo Clinic (Rochester, Minnesota) from October 2001 to December 2012 and evaluated the association between the ACT before device activation and in-hospital and 1-year outcomes. ACT values were grouped into tertiles for descriptive purposes and analyzed as a continuous variable for assessment of outcomes. We used logistic and Cox proportional hazards regression models to estimate the association of ACT and outcomes. Of the 12,055 patients who underwent PCI with an ACT value before device activation, 3,977 (33.0%) had an ACT <227, 4,046 (33.6%) had an ACT 227 to 285, and 4,032 (33.4%) had an ACT >285. Baseline and procedural characteristics were similar across ACT tertiles. In unadjusted analysis, higher ACT values were associated with death (p <0.001), bleeding (p = 0.024), procedural complication (p <0.001), and higher 1-year events (cardiac death, p <0.001; cardiac death/myocardial infarction, p = 0.022). After multivariable adjustment for baseline and procedural characteristics, ACT was not independently associated with in-hospital or 1-year ischemic, thrombotic, or bleeding outcomes. In conclusion, ACT values before device activation are not independently associated with clinically important outcomes in contemporary PCI practice.