ent-Verticilide B1 Inhibits Type 2 Ryanodine Receptor Channels and is Antiarrhythmic in Casq2 -/- Mice.

Intracellular Ca2+ leak from cardiac ryanodine receptor (RyR2) is an established mechanism of sudden cardiac death (SCD), whereby dysregulated Ca2+ handling causes ventricular arrhythmias. We previously discovered the RyR2-selective inhibitor ent-(+)-verticilide (ent-1), a 24-membered cyclooligomeric depsipeptide that is the enantiomeric form of a natural product (nat-(-)-verticilide). Here, we examined its 18-membered ring-size oligomer (ent-verticilide B1; "ent-B1") in RyR2 single channel and [3H]ryanodine binding assays, and in Casq2 -/- cardiomyocytes and mice, a gene-targeted model of SCD. ent-B1 inhibited RyR2 single channels and RyR2-mediated spontaneous Ca2+ release in Casq2 -/- cardiomyocytes with sub-micromolar potency. ent-B1 was a partial RyR2 inhibitor, with maximal inhibitory efficacy of less than 50%. ent-B1 was stable in plasma, with a peak plasma concentration of 1460 ng/ml at 10 minutes and half-life of 45 minutes after intraperitoneal administration of 3 mg/kg in mice. In vivo, ent-B1 significantly reduced catecholamine-induced ventricular arrhythmias in Casq2 -/- mice in a dose-dependent manner. Hence, we have identified a novel chemical entity - ent-B1 - that preserves the mechanism of action of a hit compound and shows therapeutic efficacy. These findings strengthen RyR2 as an antiarrhythmic drug target and highlight the potential of investigating the mirror-image isomers of natural products to discover new therapeutics. SIGNIFICANCE STATEMENT: The cardiac ryanodine receptor (RyR2) is an untapped target in the stagnant field of antiarrhythmic drug development. We have confirmed RyR2 as an antiarrhythmic target in a mouse model of sudden cardiac death and shown the therapeutic efficacy of a second enantiomeric natural product.

ent -Verticilide B1 inhibits type 2 ryanodine receptor channels and is antiarrhythmic in Casq2-/- mice.

Ca 2+ leak from cardiac ryanodine receptor (RyR2) is an established mechanism of sudden cardiac death (SCD), whereby dysregulated Ca 2+ handling causes ventricular arrhythmias. We previously discovered the RyR2-selective inhibitor ent- (+)-verticilide ( ent -1), a 24-membered cyclooligomeric depsipeptide that is the enantiomeric form of a natural product ( nat -(-)-verticilide). Here, we examined its 18-membered ring-size oligomer ( ent -verticilide B1; " ent -B1") in single RyR2 channel assays, [ 3 H]ryanodine binding assays, and in Casq2 -/- cardiomyocytes and mice, a gene-targeted model of SCD. ent -B1 inhibited RyR2 single-channels and [ 3 H]ryanodine binding with low micromolar potency, and RyR2-mediated spontaneous Ca 2+ release in Casq2-/- cardiomyocytes with sub-micromolar potency. ent -B1 was a partial RyR2 inhibitor, with maximal inhibitory efficacy of less than 50%. ent -B1 was stable in plasma, with a peak plasma concentration of 1460 ng/ml at 10 min and half-life of 45 min after intraperitoneal administration of 3 mg/kg in mice. Both 3 mg/kg and 30 mg/kg ent -B1 significantly reduced catecholamine-induced ventricular arrhythmia in Casq2-/- mice. Hence, we have identified a novel chemical entity - ent -B1 - that preserves the mechanism of action of a hit compound and shows therapeutic efficacy. These findings strengthen RyR2 as an antiarrhythmic drug target and highlight the potential of investigating the mirror-image isomers of natural products to discover new therapeutics. Significance statement: The cardiac ryanodine receptor (RyR2) is an untapped target in the stagnant field of antiarrhythmic drug development. We have confirmed RyR2 as an antiarrhythmic target in a mouse model of sudden cardiac death and shown the therapeutic efficacy of a second enantiomeric natural product.

In Vivo Pharmacokinetic and Pharmacodynamic Properties of the Antiarrhythmic Molecule ent-Verticilide.

The unnatural verticilide enantiomer (ent-verticilide) is a selective and potent inhibitor of cardiac ryanodine receptor (RyR2) calcium release channels and exhibits antiarrhythmic activity in a murine model of catecholaminergic polymorphic ventricular tachycardia (CPVT). To determine verticilide's pharmacokinetic and pharmacodynamic properties in vivo, we developed a bioassay to measure nat- and ent-verticilide in murine plasma and correlated plasma concentrations with antiarrhythmic efficacy in a mouse model of CPVT. nat-Verticilide rapidly degraded in plasma in vitro, showing >95% degradation within 5 minutes, whereas ent-verticilide showed <1% degradation over 6 hours. Plasma was collected from mice following intraperitoneal administration of ent-verticilide at two doses (3 mg/kg, 30 mg/kg). Peak C max and area under the plasma-concentration time curve (AUC) scaled proportionally to dose, and the half-life was 6.9 hours for the 3-mg/kg dose and 6.4 hours for the 30-mg/kg dose. Antiarrhythmic efficacy was examined using a catecholamine challenge protocol at time points ranging from 5 to 1440 minutes after intraperitoneal dosing. ent-Verticilide inhibited ventricular arrhythmias as early as 7 minutes after administration in a concentration-dependent manner, with an estimated potency (IC50) of 266 ng/ml (312 nM) and an estimated maximum inhibitory effect of 93.5%. Unlike the US Food and Drug Administration-approved pan-RyR blocker dantrolene, the RyR2-selective blocker ent-verticilide (30 mg/kg) did not reduce skeletal muscle strength in vivo. We conclude that ent-verticilide has favorable pharmacokinetic properties and reduces ventricular arrhythmias with an estimated potency in the nanomolar range, warranting further drug development. SIGNIFICANCE STATEMENT: ent-Verticilide has therapeutic potential to treat cardiac arrhythmias, but little is known about its pharmacological profile in vivo. The primary purpose of this study is to determine the systemic exposure and pharmacokinetics of ent-verticilide in mice and estimate its efficacy and potency in vivo. The current work suggests ent-verticilide has favorable pharmacokinetic properties and reduces ventricular arrhythmias with an estimated potency in the nanomolar range, warranting further drug development.

A Mechanistic Clinical Trial Using (R)- Versus (S)-Propafenone to Test RyR2 (Ryanodine Receptor) Inhibition for the Prevention of Atrial Fibrillation Induction.

BACKGROUND: Experimental data suggest ryanodine receptor-mediated intracellular calcium leak is a mechanism for atrial fibrillation (AF), but evidence in humans is still needed. Propafenone is composed of two enantiomers that are equally potent sodium-channel blockers; however, (R)-propafenone is an ryanodine receptor inhibitor whereas (S)-propafenone is not. This study tested the hypothesis that ryanodine receptor inhibition with (R)-propafenone prevents induction of AF compared to (S)-propafenone or placebo in patients referred for AF ablation. METHODS: Participants were randomized 4:4:1 to a one-time intravenous dose of (R)-propafenone, (S)-propafenone, or placebo. The study drug was given at the start of the procedure and an AF induction protocol using rapid atrial pacing was performed before ablation. The primary endpoint was 30 s of AF or atrial flutter. RESULTS: A total of 193 participants were enrolled and 165 (85%) completed the study protocol (median age: 63 years, 58% male, 95% paroxysmal AF). Sustained AF and/or atrial flutter was induced in 60 participants (84.5%) receiving (R)-propafenone, 60 (80.0%) receiving (S)-propafenone group, and 12 (63.2%) receiving placebo. Atrial flutter occurred significantly more often in the (R)-propafenone (N=23, 32.4%) and (S)-propafenone (N=26, 34.7%) groups compared to placebo (N=1, 5.3%, P=0.029). There was no significant difference between (R)-propafenone and (S)-propafenone for the primary outcome of AF and/or atrial flutter induction in univariable (P=0.522) or multivariable analysis (P=0.199, adjusted for age and serum drug level). CONCLUSIONS: There is no difference in AF inducibility between (R)-propafenone and (S)-propafenone at clinically relevant concentrations. These results are confounded by a high rate of inducible atrial flutter due to sodium-channel blockade. REGISTRATION: https://clinicaltrials.gov; Unique Identifier: NCT02710669.

Structure-Based Optimization of ML300-Derived, Noncovalent Inhibitors Targeting the Severe Acute Respiratory Syndrome Coronavirus 3CL Protease (SARS-CoV-2 3CLpro).

Starting from the MLPCN probe compound ML300, a structure-based optimization campaign was initiated against the recent severe acute respiratory syndrome coronavirus (SARS-CoV-2) main protease (3CLpro). X-ray structures of SARS-CoV-1 and SARS-CoV-2 3CLpro enzymes in complex with multiple ML300-based inhibitors, including the original probe ML300, were obtained and proved instrumental in guiding chemistry toward probe compound 41 (CCF0058981). The disclosed inhibitors utilize a noncovalent mode of action and complex in a noncanonical binding mode not observed by peptidic 3CLpro inhibitors. In vitro DMPK profiling highlights key areas where further optimization in the series is required to obtain useful in vivo probes. Antiviral activity was established using a SARS-CoV-2-infected Vero E6 cell viability assay and a plaque formation assay. Compound 41 demonstrates nanomolar activity in these respective assays, comparable in potency to remdesivir. These findings have implications for antiviral development to combat current and future SARS-like zoonotic coronavirus outbreaks.

Prospective Observational Study of Clinical Outcomes After Intravenous Magnesium for Moderate and Severe Acute Asthma Exacerbations in Children.

BACKGROUND: There is limited knowledge regarding whether intravenous magnesium (IV-Mg) improves outcomes in children with acute asthma exacerbations. OBJECTIVE: To examine whether IV-Mg improves outcomes in children with moderate and severe exacerbations. METHODS: We performed a secondary analysis using data from a prospective observational cohort of children aged 5 to 17 years with moderate and severe exacerbations. Standardized treatment included systemic corticosteroid and inhaled albuterol, with consideration of IV-Mg (75 mg/kg) for patients with insufficient response after 20 minutes. Propensity score (PS) models were used to examine associations of IV-Mg treatment with change in the validated Acute Asthma Intensity Research Score, hospitalization rate, and time to spacing of inhaled albuterol of 4 hours or more among hospitalized participants. RESULTS: Among 301 children, median (interquartile range) age was 8.1 (6.4-10.2) years, 170 were Black (57%), 201 were male (67%), and 84 received IV-Mg (28%). In a PS covariate-adjusted multivariable linear regression model, IV-Mg treatment was associated with a 2-hour increase in the Acute Asthma Intensity Research Score (ß-coefficient = 0.98; 95% confidence interval [CI], 0.20-1.77), indicating increased exacerbation severity. Three additional PS-based models yielded similar results. Participants receiving IV-Mg had 5.8-fold (95% CI, 2.8-11.9) and 6.8-fold (95% CI, 3.6-12.9) greater odds of hospitalization in PS-based multivariable regression models. Among hospitalized participants, there was no difference in time to albuterol of every 4 hours or more in a PS covariate-adjusted Cox proportional hazards model (hazard ratio = 1.2; 95% CI, 0.8-1.8). CONCLUSIONS: Among children with moderate and severe exacerbations, IV-Mg is associated with increased exacerbation severity, increased risk for hospitalization, and no acceleration in exacerbation resolution among hospitalized participants.

2-Hydroxybenzylamine (2-HOBA) to prevent early recurrence of atrial fibrillation after catheter ablation: protocol for a randomized controlled trial including detection of AF using a wearable device.

BACKGROUND: Although catheter ablation is an effective therapy for atrial fibrillation (AF), the most common cardiac arrhythmia encountered in clinical practice, AF ablation generates inflammation and oxidative stress in the early postoperative period predisposing to recurrence of AF. Isolevuglandins (IsoLGs) are reactive lipid mediators of oxidative stress injury that rapidly react with endogenous biomolecules to compromise their function. 2-Hydroxybenzylamine (2-HOBA), a potent small molecule scavenger of IsoLGs, sequesters the reactive species as inert adducts. This mechanism, coupled with reported safety in humans, supports the investigation of 2-HOBA as a novel therapeutic to reduce AF caused by oxidative stress, such as that which occurs after catheter ablation. Accordingly, we seek to test the hypothesis that treatment with 2-HOBA will decrease early recurrence of AF and other atrial arrhythmias following AF ablation by decreasing IsoLG adducts with native biomolecules. METHODS: The proposed trial will randomly assign 162 participants undergoing cryo- or radiofrequency catheter ablation for AF to 2-HOBA (N = 81) or placebo (N = 81). Individuals will begin the study drug 3 days prior to ablation and continue for 28 days. Participants will be given a wearable smartwatch capable of detecting and recording atrial arrhythmias. They will be instructed to record ECGs daily with additional ECGs if they experience symptoms of AF or when alerted by the smartwatch AF detection alarm. The primary clinical endpoint will be an episode of AF, atrial tachycardia, or atrial flutter lasting 30 s or more within 28 days post-AF ablation. Secondary measures will be the change in IsoLG adduct levels from blood samples collected immediately pre-ablation and post-ablation and reduction in AF burden as calculated from the smartwatch. DISCUSSION: The proposed trial will test the hypothesis that 2-HOBA reduces post-ablation atrial arrhythmias through sequestration of reactive IsoLG species. The results of this study may improve the understanding of the role of IsoLGs and oxidative stress in AF pathogenesis and provide evidence to advance 2-HOBA and related compounds as a new therapeutic strategy to treat AF. TRIAL REGISTRATION: ClinicalTrials.gov NCT04433091 . Registered on June 3, 2020.

Pilot Study of Peak Plasma Concentration After High-Dose Oral Montelukast in Children With Acute Asthma Exacerbations.

Acute asthma exacerbations are primarily due to airway inflammation and remain one of the most frequent reasons for childhood hospitalizations. Although systemic corticosteroids remain the mainstay of therapy because of their anti-inflammatory properties, not all inflammatory pathways are responsive to systemic corticosteroids, necessitating hospital admission for further management. Cysteinyl leukotrienes (LTs) are proinflammatory mediators that play an important role in systemic corticosteroids non-responsiveness. Montelukast is a potent LT-receptor antagonist, and an intravenous preparation caused rapid, sustained improvement of acute asthma exacerbations in adults. We hypothesized that a 30-mg dose of oral montelukast achieves peak plasma concentrations (Cmax ), comparable to the intravenous preparation (1700 ng/mL) and would be well tolerated in 15 children aged 5 to 12 years with acute asthma exacerbations. After administration of montelukast chewable tablets, blood samples were collected at 0, 15, 30, 45, 60, 120, 180, and 240 minutes. Plasma was separated and frozen at -80°C until analysis for montelukast concentration using liquid chromatography- tandem mass spectrometry. Median time to Cmax (tmax ) was 3.0 hours. Six participants (40%) achieved Cmax of 1700 ng/mL or higher. However, there was high interindividual variability in peak plasma concentration (median Cmax of 1378 ng/mL; range, 16-4895 ng/mL). No participant had side effects or adverse events. Plasma concentrations from this pilot study support the design of a weight-based dose-finding study aimed at selecting an optimal dose for future clinical trials to assess the efficacy of high-dose oral montelukast in children with moderate to severe asthma exacerbations.

Safety, tolerability, and pharmacokinetics of repeated oral doses of 2-hydroxybenzylamine acetate in healthy volunteers: a double-blind, randomized, placebo-controlled clinical trial.

BACKGROUND: 2-Hydroxybenzylamine (2-HOBA) is a selective dicarbonyl electrophile scavenger being developed as a nutritional supplement to help protect against the development of conditions associated with dicarbonyl electrophile formation, such as the cognitive decline observed with Mild Cognitive Impairment or Alzheimer's disease. METHODS: This study evaluated the safety, tolerability, and pharmacokinetics of repeated oral doses of 2-HOBA acetate (500 or 750 mg) administered to healthy volunteers every eight hours for two weeks. The effects of 2-HOBA on cyclooxygenase function and cerebrospinal fluid penetrance of 2-HOBA were also investigated. RESULTS: Repeated oral administration of 2-HOBA was found to be safe and well-tolerated up to 750 mg TID for 15 days. 2-HOBA was absorbed within 2 h of administration, had a half-life of 2.10-3.27 h, and an accumulation ratio of 1.38-1.52. 2-HOBA did not interfere with cyclooxygenase function and was found to be present in cerebrospinal fluid 90 min after dosing. CONCLUSIONS: Repeated oral administration of 2-HOBA was found to be safe and well-tolerated. These results support continued development of 2-HOBA as a nutritional supplement. TRIAL REGISTRATION: Studies are registered at ClinicalTrials.gov (NCT03555682 Registered 13 June 2018, NCT03554096 Registered 12 June 18).

Effect of genetic variation in P2Y12 on TRAP-stimulated platelet response in healthy subjects.

In platelets, thrombin receptor signaling depends upon the release of adenosine diphosphate and subsequent activation at purinergic subtype Y (P2Y) receptors. The purpose of this study is to evaluate the influence of specific P2Y12 polymorphisms on platelet reactivity in healthy subjects mediated by thrombin receptor activating peptide (TRAP). We recruited a total of 29 healthy volunteers who had been previously genotyped for two polymorphisms of the P2Y12 receptor: the H2 haplotype (rs2046934) and 34C>T (rs6785930). Flow cytometry and the VerifyNow assay were used to assess platelet activation and aggregation stimulated by TRAP in the presence and absence of specific receptor antagonists for the P2Y1, P2Y12, and thromboxane A2 receptors. We identified a significant recessive effect of the P2Y12-receptor H2 haplotype on TRAP-induced flow cytometry. Specifically, H2/H2 carriers (n = 5) demonstrated a significant reduction in both glycoprotein IIb/IIIa receptor activation (p < 0.001) and CD62P expression (p = 0.035). While the VerifyNow assay did not reveal any effect of haplotype on TRAP-mediated platelet aggregation (p = 0.72), the H2/H2 subjects demonstrated greater platelet inhibition in the presence of cangrelor, a specific receptor antagonist for the P2Y12 receptor (p = 0.023). No consistent effects of the separate 34C>T genotype (rs6785930) were demonstrated under the conditions evaluated. The findings of this study suggest a potential association between P2Y12-receptor H2/H2 carriers and reduced platelet function mediated by TRAP in healthy volunteers.

Elevation of plasma milrinone concentrations in stage D heart failure associated with renal dysfunction.

PURPOSE: To determine steady state milrinone concentrations in patients with stage D heart failure (HF) with and without renal dysfunction METHODS: We retrospectively identified patients with stage D HF at a single medical center on continuous milrinonein fusion at the time of plasma collection for entry into a research registry database. Milrinone was prescribed and titrated to improve hemodynamic and clinical status by a cardiologist. Plasma samples were obtained at steady state milrinone concentrations. Patients were stratified by creatinine clearance (CrCl) into 4 groups: group 1 (CrCl >60 mL/min), group 2 (CrCl 60-30 mL/min), group 3 (CrCl <30 mL/min), and group 4 (intermittent hemodialysis). Retrospective chart review was performed to quantify the post milrinone hemodynamic changes by cardiac catheterization and electrophysiologic changes by implantable cardiac defibrillator (ICD) interrogation. RESULTS: A total of 29 patients were identified: group 1 (n=14), group 2 (n=10), group 3(n=3), and group 4 (n = 2). The mean infusion rate (0.391+0.08 mg/kg/min) did not differ between groups (P=0.14). The mean milrinone concentration was 451+243 ng/mL in group 1, 591+293 ng/mL in group 2, 1575+962 ng/mL in group 3, and 6252+4409 ng/mL in group 4 (P<0.05 compared to groups 1). There was no difference in post milrinone hemodynamic improvements between the groups (P=0.41). The ICD interrogation revealed limited comparisons, but 6 of the 8 post milrinone ventricular tachycardia episodes requiring defibrillation occurred in group 4 patients. CONCLUSION: Patients with stage D HF having severe renal dysfunction have elevated milrinone concentrations. Future studies of milrinone concentrations are warranted to investigate the potential risk of life-threatening arrhythmias and potential dosing regimens in renal dysfunction.

Pharmacodynamic interplay of the P2Y(1), P2Y(12), and TxA(2) pathways in platelets: the potential of triple antiplatelet therapy with P2Y(1) receptor antagonism.

INTRODUCTION: Previous work suggests that the extent of platelet inhibition by P2Y(1) receptor antagonism may be underappreciated, particularly in the context of dual antiplatelet therapy with aspirin and clopidogrel. MATERIALS AND METHODS: Using P2Y(1), P2Y(12), and TxA(2) receptor antagonists individually and in combination, we assessed the incremental changes from baseline platelet reactivity in blood collected from healthy volunteers. RESULTS: The P2Y(1) receptor antagonist further inhibited platelet activation and aggregation in several assay conditions ex vivo when combined with P2Y(12) and/or TxA(2) receptor blockers. Collagen and TRAP-induced platelet aggregation measured by light transmittance aggregometry was inhibited to a greater extent with the triple combination relative to each of the antagonists alone. The triple combination of P2Y(1), P2Y(12), and TxA(2) receptor antagonists also significantly shifted adenosine diphosphate (ADP)-stimulated platelet glycoprotein IIb/IIIa receptor and P-selectin expression compared to individual or dual antagonists. CONCLUSIONS: These results substantiate that additional platelet inhibition occurs with the triple combination of P2Y(1), P2Y(12), and TxA(2) receptor antagonists and support further testing of P2Y(1) receptor antagonists as an option for alternative, synergistic, or triple antiplatelet therapy.

Pharmacokinetics and pharmacodynamics of a bolus and infusion of cangrelor: a direct, parenteral P2Y12 receptor antagonist.

The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of cangrelor administered as an intravenous bolus plus a continuous infusion in healthy volunteers. Twenty-two healthy volunteers are randomized to receive 1 of 2 intravenous cangrelor dosing regimens: a 15-microg/kg bolus followed by a 2-microg/kg/min infusion or a 30-microg/kg bolus followed by a 4-microg/kg/min infusion. The infusion is continued for 60 minutes, and serial blood samples are obtained for evaluation of pharmacokinetic and pharmacodynamic parameters. Administration of an intravenous bolus followed by a continuous infusion rapidly achieves maximum concentrations of cangrelor that are associated with extensive platelet inhibition within 2 minutes. Moreover, extensive platelet inhibition is maintained throughout the infusion period with near-full recovery of platelet function within 60 to 90 minutes of terminating the infusion. The effect of high-dose cangrelor is more consistent and demonstrates a greater level of inhibition on adenosine diphosphate-induced P-selectin expression; how ever, no significant differences are observed between the 2 dosing regimens with regard to platelet aggregation or time to recovery of platelet function. Cangrelor administered as an intravenous bolus followed by a continuous infusion in healthy volunteers offers rapid and reversible inhibition of platelet function.

Considerable variability in platelet activity among patients with coronary artery disease in response to an increased maintenance dose of clopidogrel.

BACKGROUND: Variable platelet response to clopidogrel has been widely observed. Studies have shown that the mean aggregation response to clopidogrel can be changed by a higher maintenance dose. However, these studies have not focused on individual changes. OBJECTIVES: This study examined the platelet function effects of increasing the maintenance clopidogrel dose from 75 to 150 mg/day with a focus on inter-individual response. PATIENTS/METHODS: Twenty patients with known coronary artery disease receiving 75 mg/day clopidogrel were recruited and given 150 mg/day clopidogrel for 30 days, then returned to 75 mg/day for an additional 30 days. Platelet function was assessed through light-transmittance aggregometry (LTA) and the VerifyNow P2Y12 assay at baseline, 30 days, and 60 days. RESULTS: Mean platelet inhibition was significantly improved with the increased maintenance dose when measured by the VerifyNow P2Y12 assay (P2Y12 reaction units: 191+/-15 vs. 158+/-17, P=0.013), but not when measured by LTA (LTA-adenosine diphosphate 5: 40+/-3 vs. 36+/-3, P = 0.11; LTA-adenosine diphosphate 20: 50+/-3 vs. 47+/-3, P = 0.23). However, only 50% of individual patients experienced improved platelet inhibition, as measured by the VerifyNow P2Y12 assay, when treated with the increased maintenance dose. Furthermore, poor baseline platelet response did not predict improved responsiveness at the increased dose. CONCLUSION: Despite changing the population's mean antiplatelet response, an increased maintenance dose of clopidogrel did not improve antiplatelet response in a substantial number of patients; nor did baseline platelet function predict response to a higher maintenance dose.

Transitioning patients from cangrelor to clopidogrel: pharmacodynamic evidence of a competitive effect.

BACKGROUND: Cangrelor is a direct, parenteral, and reversible inhibitor of the platelet P2Y12 receptor currently undergoing Phase III testing. As many individuals treated acutely with cangrelor will often be treated long-term with a thienopyridine, it is important to determine the effects of concurrent cangrelor and clopidogrel administration. METHODS AND RESULTS: Ten healthy volunteers received a 600 mg oral loading dose of clopidogrel and then underwent serial platelet function monitoring for 6 h. Two weeks later these same individuals received a 600 mg clopidogrel loading dose simultaneously with a cangrelor IV bolus (30 microg/kg) and a 2-hour infusion (4 microg/kg/min). A separate group of ten volunteers received a 600 mg clopidogrel loading dose after administration of a cangrelor bolus and a 1-hour infusion. The effects on ADP-induced platelet activation and aggregation were evaluated by flow cytometry, whole-blood electrical impedance, and light-transmittance aggregometry. Cangrelor and clopidogrel alone achieved the expected levels of platelet inhibition. However, the sustained platelet inhibition anticipated for clopidogrel treatment did not occur when cangrelor was initiated simultaneously. No such effect was found when clopidogrel was started upon completion of the cangrelor infusion. CONCLUSION: To achieve sustained platelet P2Y12 inhibition in patients treated with cangrelor, clopidogrel administration should be started when the cangrelor infusion is terminated.

Management of antiplatelet therapy for minimization of bleeding risk before cardiac surgery.

Antiplatelet therapy is commonly administered for primary and secondary prevention of stroke, recurrent angina, myocardial infarction, and death in patients with cardiovascular disorders. It also is associated with an increased risk of bleeding. We describe the management of antiplatelet therapy in patients undergoing coronary artery bypass graft surgery. In addition, we provide basic information about the mechanisms of action by which the most common antiplatelet agents inhibit platelet function. This information is integrated with results from pharmacologic studies and clinical trials. Determining the net effect in patients undergoing coronary artery bypass graft surgery requires knowledge about the pharmacokinetics, pharmacodynamics, and clinical efficacy of each drug, and an estimation of the absolute thrombotic versus hemorrhagic risk for each patient.

Interventions to improve guideline compliance following coronary artery bypass grafting.

BACKGROUND: Lifestyle modification and appropriate medical therapy improve long-term outcomes following coronary artery bypass grafting (CABG). Our institutional experience suggested that evidence-based recommendations were not being followed postdischarge after CABG. We undertook this study to document our rate of compliance with evidence-based guidelines and to correct deficiencies in our discharge practices. METHODS: Seven evidence-based interventions were studied after CABG: (1) institution of beta-blocker therapy, (2) angiotensin-converting enzyme (ACE) inhibitor therapy, (3) aspirin, (4) lipid-lowering therapy, (5) smoking cessation intervention, (6) heart-healthy diet therapy, and (7) physical activity recommendations. The rate of compliance with guidelines in 50 control patients was measured at discharge. A multidisciplinary team including cardiac surgeons, nurses, dieticians, physical therapists, and clinical pharmacists evaluated the guideline compliance in the control group and developed interventions to assure guideline compliance at the time of discharge. A subsequent study group of 50 patients was then assessed prospectively to measure the guideline compliance after institution of intervention programs. The multidisciplinary team agreed on predefined acceptable compliance limits as follows: (1) >80% of patients receive ACE inhibitors at discharge, (2) 100% of patients receive beta-blockers, aspirin, and lipid-lowering agents at discharge, and (3) 100% of patients receive lifestyle modification counseling at discharge. Compliance with guidelines was defined as documentation in the medical record of provision of medications and lifestyle counseling at the time of discharge. RESULTS: In the control group, the rate of guideline compliance was surprisingly low. Rates of compliance with guidelines increased significantly after the multidisciplinary interventions were undertaken. CONCLUSIONS: We conclude that compliance with guidelines known to improve long-term outcome is suboptimal after CABG. A multidisciplinary intervention program can improve compliance with currently accepted guidelines and quality indicators in patients following CABG.

Recombinant factor VIIa for refractory bleeding after cardiac surgery secondary to anticoagulation with the direct thrombin inhibitor lepirudin.

A 56-year-old man with heparin-induced thrombocytopenia with thrombosis syndrome (HITTS) received anticoagulation with recombinant hirudin (lepirudin) for emergency coronary artery bypass graft (CABG) surgery and aortic valve replacement. The patient experienced life-threatening refractory bleeding that was successfully treated with recombinant factor VIIa. He had a history of infective endocarditis that resulted in severe aortic insufficiency, three-vessel coronary artery disease, and acute renal failure requiring hemodialysis. The patient was transferred from another hospital for the emergency surgery, but before his transfer, he developed HITTS secondary to therapeutic heparin for a deep vein thrombosis of the lower extremity. The presence of HITTS, the urgent nature of the case, and the availability of the direct thrombin inhibitor led the surgical team to select lepirudin for anticoagulation to facilitate cardiopulmonary bypass. After separation from cardiopulmonary bypass, the patient was in a coagulopathic state due to the inability to reverse the lepirudin and the slowed elimination of the drug secondary to inadequate renal function. As a result, the patient experienced excessive generalized oozing that was unresponsive to traditional therapies and blood product transfusions. Recombinant factor VIIa 35 microg/kg was given as rescue therapy. The bleeding slowed, which allowed placement of chest tubes and closing of the sternum. The patient was transferred to the intensive care unit in stable condition with no evidence of thrombosis in the freshly placed bypass grafts or on the bioprosthetic valve. Recombinant factor VIIa appears to be a suitable option as salvage therapy in patients with refractory bleeding secondary to anticoagulation with a direct thrombin inhibitor during cardiac surgery.