Search

This article is part one in a two-part series addressing risk factors for and management of drug-induced torsade de pointes, a potentially fatal arrhythmia that can result from severe QT-interval prolongation. [ABSTRACT FROM AUTHOR]

The number of peptide-like scaffolds found in late-stage drug development is increasing, but a critical unanswered question in the field is whether substituents (side chains) or the backbone drive passive permeability. The backbone is scrutinized in this study. Five series of macrocyclic peptidic compounds were prepared, and their passive permeability was determined (PAMPA, Caco-2), to delineate structure-permeability relationships. Each series was based on the cell-permeable antiarrhythmic compound ent -verticilide, a cyclic oligomeric depsipeptide (COD) containing repeating ester/ N -Me amide didepsipeptide monomers. One key finding is that native lipophilic ester functionality can impart a favorable level of permeability, but ester content alone is not the final determinant - the analog with highest P app was discovered by a single ester-to- N -H amide replacement. Furthermore, the relative composition of esters and N -Me amides in a series had more nuanced permeability behavior. Overall, a systematic approach to structure-permeability correlations suggests that a combinatorial-like investigation of functionality in peptidic or peptide-like compounds could better identify leads with optimal passive permeability, perhaps prior to modification of side chains., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

Intracellular 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 RyR2 single channel and [ 3 H]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 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 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., (Copyright © 2024 by The American Society for Pharmacology and Experimental Therapeutics.)

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 (IC 50 ) 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., (Copyright © 2023 by The American Society for Pharmacology and Experimental Therapeutics.)

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.

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 (β-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., (Copyright © 2021 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

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 (3CL pro ). X-ray structures of SARS-CoV-1 and SARS-CoV-2 3CL pro 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 3CL pro 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.

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., (© 2021. The Author(s).)

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 (C max ), 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 C max (t max ) was 3.0 hours. Six participants (40%) achieved C max of 1700 ng/mL or higher. However, there was high interindividual variability in peak plasma concentration (median C max 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., (© 2020, The American College of Clinical Pharmacology.)

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).

Background: 2-Hydroxybenzylamine (2-HOBA) is a selective scavenger of dicarbonyl electrophiles that protects proteins and lipids from being modified by these electrophiles. It is currently being developed for use as a nutritional supplement to help maintain good health and protect against the development of conditions associated with dicarbonyl electrophile formation, such as the cognitive decline associated with Mild Cognitive Impairment and Alzheimer's disease., Methods: In this first-in-human study, the safety, tolerability, and pharmacokinetics of six ascending single oral doses of 2-HOBA acetate were tested in eighteen healthy human volunteers., Results: Reported adverse events were mild and considered unlikely to be related to 2-HOBA. There were no clinically significant changes in vital signs, ECG recordings, or clinical laboratory parameters. 2-HOBA was fairly rapidly absorbed, with a t max of 1-2 h, and eliminated, with a t 1/2 of approximately 2 h. Both t max and t 1/2 were independent of dose level, while C max and AUC increased proportionally with dose level., Conclusions: 2-HOBA acetate was safe and well-tolerated at doses up to 825 mg in healthy human volunteers, positioning it as a good candidate for continued development as a nutritional supplement., Trial Registration: This study is registered at ClinicalTrials.gov (NCT03176940).

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.

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.

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., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

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.

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.

Objective: To determine whether obesity-induced hypertension was associated with alterations in vascular contractility and/or cardiac function., Design: Male Sprague-Dawley rats were fed either a low fat (LF; 11% kcal as fat) or a moderately high fat (MHF; 32% kcal as fat) diet for 11 weeks., Measurements: Body weight; mean arterial pressure; angiotensin peptides; mesenteric contractile response to phenylephrine (PE), potassium chloride (KCl), serotonin, angiotensin II (AngII), calcium chloride; baseline and isoproterenol-induced cardiac contractility; baseline and isoproterenol-induced coronary artery blood flow., Results: Rats fed the MHF diet segregated into obesity-prone (OP) and obesity-resistant (OR) groups. OP rats exhibited elevations in mean arterial pressure (MAP) and elevations in systemic concentrations of angiotensin peptides. Mesenteric arteries from OP rats exhibited a greater contractile response to PE, KCl and serotonin (5-HT). Heightened responses to PE persisted in arteries from OP rats even after normalization of the response to KCl. In contrast, the response of permeabilized mesenteric arteries to a maximal concentration of calcium was similar in rats from each group. Isolated perfused hearts exhibited similar baseline and isoproterenol-induced contractility in rats from each group. However, isoproterenol was unable to increase coronary artery blood flow in hearts from OP rats., Conclusion: Enhanced vascular reactivity may contribute to obesity-induced hypertension, while reductions in coronary artery relaxation would impair the ability of the heart to respond to increased myocardial demand.

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.

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.

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.

Purpose: Pegylated and nonpegylated cetyl alcohol/polysorbate nanoparticles (E78 NPs) are being tested as drug carriers for specific tumor and brain targeting. Because these nanoparticle formulations are designed for systemic administration, it is important to test the compatibility of these lipid-based NPs with blood and blood cells., Methods: The hemocompatibility of E78 NPs was evaluated with a particular focus on hemolytic activity, platelet function, and blood coagulation. Human red blood cell lysis was determined by measuring hemoglobin release. Activation and aggregation of human platelets were determined using flow cytometry and aggregometry, respectively. Finally, the whole blood clotting time was measured using human blood., Results: E78 NPs did not cause in vitro red blood cell lysis at concentrations up to 1 mg/mL. In addition, under conditions tested, E78 and polyethylene glycol (PEG)-coated E78 NPs (PEG-E78 NPs) did not activate platelets. In fact, both NP formulations very rapidly inhibited agonist-induced platelet activation and aggregation in a dose-dependent manner. Additionally, E78 NPs significantly prolonged in vitro whole blood clotting time at a concentration of 500 microg/mL or greater., Conclusions: It was concluded that PEG-coated and nonpegylated E78 NPs have potential blood compatibility at clinically relevant doses. Based on the calculated nanoparticle-to-platelet ratio, the concentration at which E78 NPs could potentially affect platelet function in vivo was approximately 1 mg/mL.

Objective: To report a case of successful use of recombinant factor VIIa (rFVIIa) for the treatment of refractory bleeding in a patient undergoing orthotopic heart transplantation., Case Summary: A 57-year-old white male with idiopathic cardiomyopathy was taken to the operating room for explantation of his left-ventricular assist device and orthotopic heart transplantation. He experienced excessive generalized oozing that required transfusions of multiple units of blood products and significant amounts of Cellsaver (washed red blood cells via autotransfusion) without achieving adequate hemostasis. After ruling out any obvious surgical sources of bleeding and attempting to correct all coagulation deficiencies, the clinicians administered rFVIIa 90 microg/kg. The oozing rapidly declined to a negligible level, chest tubes and sternal wires were placed, and the chest was closed. The patient was on minimal inotropic support and was transferred to the intensive care unit in stable condition., Discussion: Cardiac surgery is often associated with significant disruption of the coagulation system, particularly in high-risk patients, such as those undergoing removal of a ventricular assist device and subsequent orthotopic heart transplantation. This can lead to life-threatening bleeding that can require multiple hemostatic agents and significant transfusions to restore hemostasis. Recently, rFVIIa has been utilized as an alternative to massive transfusion for treatment of refractory bleeding in several patient populations, including some cardiac surgery patients., Conclusions: rFVIIa appears to be a viable option as rescue therapy for treatment of refractory bleeding following orthotopic heart transplantation. Despite the anecdotal success of rFVIIa in this setting, further clinical research is needed.

Cardiac surgery often is associated with a significant disruption of the coagulation system, particularly in high risk patients such as those undergoing placement of ventricular assist devices. This type of severe coagulopathy can lead to life threatening bleeding that can require massive transfusions to restore hemostasis. Recently, recombinant activated factor VII (rFVlla) has been +used as an alternative to massive transfusion for the treatment of refractory bleeding in several patient populations, including cardiac surgery patients. In the case reported here, the patient's risk was compounded by multiple operations in a short period of time and circulatory collapse that was initially managed with a shortterm left ventricular assist device. After multiple failed attempts at weaning the patient from circulatory assistance, he was taken back to the operating room for conversion to a chronic, implantable device. This procedure was complicated by a severe coagulopathy secondary to a myriad of factors commonly encountered after the use of cardiopulmonary bypass. The administration of rFVlla resulted in a rapid cessation of bleeding without thrombotic complications. This is the first case reported involving an acute to chronic bridge patient. Despite the anecdotal success of rFVlla, further clinical research is needed to establish both the safety and economic feasibility of this agent.

A 61-year-old woman who underwent lung transplantation developed severe respiratory syncytial virus (RSV) pneumonia and experienced respiratory failure requiring mechanical ventilation. She was treated initially with aerosolized ribavirin monotherapy; RSV hyperimmune globulin was later added to her regimen. Lung transplant recipients are acutely susceptible to respiratory infections, including community-acquired respiratory viruses. Respiratory syncytial virus is particularly difficult to treat in immunocompromised patients because of the lack of proved pharmaceutical agents and solid scientific evidence by which to guide therapy. The most important factor appears to be the early start of therapy; immunocompromised patients who develop RSV pneumonia and subsequent respiratory failure requiring mechanical ventilation have a mortality rate approaching 100%. This case report demonstrates the successful treatment of RSV pneumonia with the combination of aerosolized ribavirin and RSV hyperimmune globulin in a severely ill lung transplant recipient who required mechanical ventilation.

Activation of the sympathetic nervous system is well documented in heart failure. Our previous studies demonstrated an increase in evoked norepinephrine (NE) release from left ventricle (LV) slices at 10 days of pressure overload. The purpose of this study was to test the hypothesis that presynaptic modulation of NE release contributes to sympathetic activation after pressure overload. We examined the functional status of the presynaptic alpha(2)- and beta(2)-receptors and ANG II subtype 1 (AT(1)) receptors in LV slices from 10-day aortic constricted (AC) and sham-operated (SO) rats. Evoked (3)H overflow from LV slices preloaded with [(3)H]NE was increased in AC rats. The alpha(2)-agonist UK-14,304 decreased evoked (3)H overflow with no differences between groups. The beta(2)-agonist salbutamol increased evoked (3)H overflow with greater sensitivity in slices from AC rats. The beta-antagonist propranolol decreased evoked (3)H overflow from LV slices of AC rats but not controls. ANG II increased evoked (3)H overflow with greater sensitivity in slices from AC rats. These data support the hypothesis that aberrant presynaptic modulation of catecholamine release contributes to sympathetic activation after pressure overload.

The purpose of this study is to determine the effect of clonidine on cardiac norepinephrine spillover utilizing an isolated rat heart preparation with attached cardiac sympathetic nerves. Following a 20-minute stabilization period, the sympathetic ganglion for each heart preparation was electrically stimulated with 10V and 2 Hz for 30 seconds (S1: 60 pulses). Heart rate, left ventricular developed pressure, and coronary perfusion pressure was allowed to return to baseline and the perfusate was randomly switched to Krebs buffer containing one of two treatments: placebo or clonidine (1 microM). After 10 minutes of treatment, the sympathetic ganglion was again electrically stimulated with 10V and 2 Hz for 30 seconds (S2: 60 pulses). The perfusate exiting the heart before, during, and after each electrical stimulation was collected for the determination of cardiac norepinephrine spillover. Clonidine administration significantly reduced cardiac norepinephrine spillover by approximately 50% (P < 0.05) and was associated with a 36% reduction in heart rate (P < 0.05). These findings provide evidence that clonidine can directly suppress NE spillover from cardiac sympathetic nerve terminals. Thus, suppression of cardiac NE by clonidine may be due to stimulation of presynaptic alpha2-adrenergic receptors or imidazoline subtype I receptors located on cardiac sympathetic nerve terminals. Results from our study demonstrate a reduction in cardiac NE spillover by clonidine and provide additional evidence that it can directly suppress peripheral sympathetic activity in that our results were obtained utilizing an isolated perfused heart preparation with attached cardiac sympathetic nerves devoid of any CNS input.

A 42-year-old woman who underwent single lung transplantation who received tacrolimus and a 58-year-old woman with pneumonia and multiple comorbidities who received haloperidol both experienced drug-induced prolongation of cardiac repolarization. The second woman also developed torsade de pointes. Critically ill patients are particularly susceptible to developing torsade de pointes due to various comorbidities, electrolyte disturbances, and receipt of numerous drugs. These two case reports illustrate the increased risk for drug-induced cardiotoxicity in the critically ill patient. They also indicate the need for current knowledge derived from basic research and retrospective case reports on drug-induced torsade de pointes to be integrated into the existing body of knowledge. Guidelines can then be developed to help prospectively reduce the frequency of adverse effects in intensive care patients. Research is necessary regarding identification of high-risk patients before drugs are administered, and clarification of the proper role of therapeutic QT monitoring in clinical practice.

Study Objective: To investigate the effects of the angiotensin II subtype 1 receptor (AT1R) antagonist losartan on functional recovery of isolated rat hearts undergoing global myocardial ischemia-reperfusion compared with myocardial protective effects of ischemic preconditioning., Design: Ex vivo experiment using isolated perfused rat heart., Setting: Academic laboratory., Intervention: Hearts from Sprague-Dawley rats were perfused with oxygenated Krebs-Henseleit buffer and randomized to one of four groups: time control, vehicle, ischemic preconditioning, or losartan., Measurements and Main Results: After randomization, hearts underwent 30 minutes of global ischemia followed by 30 minutes of reperfusion. Changes in end-diastolic pressure (EDP), left ventricular developed pressure (LVDP), and infarct size were examined between treatment groups by two-way analysis of variance with repeated measures. Cardiac angiotensin II receptor (ATR) density and infarct size were measured in control hearts and in a subgroup of hearts exposed to ischemia-reperfusion injury. Total ATR density and percentage of myocardial AT1R were increased in hearts exposed to ischemia-reperfusion. Myocardial ischemia-reperfusion injury resulted in a 56% reduction in LVDP from baseline in hearts randomized to vehicle. However, it declined by only 22% and 28% in hearts randomized to ischemic preconditioning and losartan, respectively. Compared with vehicle, both ischemic preconditioning and losartan decreased EDP (ischemic preconditioning 39 +/- 3 mm Hg, losartan 54 +/- 5 mm Hg, vs vehicle 78 +/- 8 mm Hg), and reduced infarct size (ischemic preconditioning 9%, losartan 12%, vs vehicle 36%)., Conclusion: Treatment of isolated rat hearts with losartan before ischemia-reperfusion injury resulted in significant cardioprotection similar to that observed with ischemic preconditioning.

The use of nesiritide in the improvement of patient hemodynamics, decreased length of stay (LOS), and rehospitalization is discussed. Nesiritide is a useful agent for the treatment of the acutely decompensated heart failure patient. Previous trials suggest that the use of nesiritide results in improved outcomes as compared with other agents. To date, there are no data comparing nesiritide to milrinone in the treatment of the acutely decompensated heart failure patient. Fifty-five patients admitted to the heart failure service were identified retrospectively; 29 received nesiritide and 26 received milrinone. Baseline characteristics, hemodynamic data, and LOS data were collected. Primary outcomes were the overall LOS, intensive care LOS, and readmission within 30 days of discharge. Other outcomes included duration of vasoactive agents used, overall diuresis, and total cost of therapy. Baseline hemodynamic data were similar between groups. Patients in the milrinone group had an overall LOS of 8.2 days compared to 7 days in the nesiritide group (p = NS). LOS in the intensive care unit was 5.9 days in the milrinone group compared with 3.9 days in the nesiritide group (p = 0.007). Readmission at 30 days was 28% in the milrinone group compared with 16% in the nesiritide group (p = NS). Infusion time was shorter in the nesiritide group, 50 versus 117 hours (p = 0.001). Cost of therapy (cost of bed, supplies, and drug) was $398 less per patient receiving nesiritide. The use of nesiritide led to improvement in patient hemodynamics and resulted in a trend toward decreases in LOS and rehospitalization. Total cost of therapy was lower in the nesiritide group as compared to those patients treated with milrinone.

Angiotensin II and norepinephrine (NE) have been implicated in the neurohumoral response to pressure overload and the development of left ventricular hypertrophy. The purpose of this study was to determine the temporal sequence for activation of the renin-angiotensin and sympathetic nervous systems in the rat after 3-60 days of pressure overload induced by aortic constriction. Initially on pressure overload, there was transient activation of the systemic renin-angiotensin system coinciding with the appearance of left ventricular hypertrophy (day 3). At day 10, there was a marked increase in AT(1) receptor density in the left ventricle, increased plasma NE concentration, and elevated cardiac epinephrine content. Moreover, the inotropic response to isoproterenol was reduced in the isolated, perfused heart at 10 days of pressure overload. The affinity of the beta(2)-adrenergic receptor in the left ventricle was decreased at 60 days. Despite these alterations, there was no decline in resting left ventricular function, beta-adrenergic receptor density, or the relative distribution of beta(1)- and beta(2)-receptor sites in the left ventricle over 60 days of pressure overload. Thus activation of the renin-angiotensin system is an early response to pressure overload and may contribute to the initial development of cardiac hypertrophy and sympathetic activation in the compensated heart.

Study Objective: To evaluate the impact of gender on labetalol kinetics., Design: Part of a randomized, crossover study., Setting: Academic medical center., Patients: Nineteen hypertensive patients (14 men, 5 women; 6 blacks, 13 whites)., Interventions: Participants had labetalol dosages titrated to a specific antihypertensive response, then underwent ambulatory blood pressure monitoring (ABPM) and a pharmacokinetic study. Labetalol plasma concentrations were measured by high-performance liquid chromatography (HPLC) and labetalol stereoisomer ratios were determined in a single plasma sample by chiral HPLC, both with fluorescence detection., Measurements and Main Results: Labetalol concentrations were 80% higher in women (area under the concentration-time curve [AUC]/dose x 1000: 6.79 +/- 2.11 in women vs 3.82 +/- 1.37 hr/L in men, p<0.05), yet both genders had a similar antihypertensive response by 24-hour ABPM. Dose-corrected AUC (AUC/dose x 1000) for labetalol's stereoisomers in women and men, respectively, were S,R-labetalol 7.55 +/- 1.47 and 4.83 +/- 1.54 hr/L (p<0.05), S,S-labetalol 8.23 +/- 2.93 and 4.65 +/- 1.78 hr/L (p<0.05), R,S-labetalol 6.99 +/- 3.30 and 4.25 +/- 2.35 hr/L (p=0.11), and R,R-labetalol 3.91 +/- 2.57 and 3.55 +/- 3.08 hr/L (NS)., Conclusion: The higher labetalol concentration in women than in men was explained largely by differences in inactive and alpha1-blocking stereoisomers. However, concentrations were similar between genders for the beta-blocking stereoisomer (R,R-labetalol), possibly explaining the similarity in antihypertensive response to the drug. This study highlights the importance of determining stereoisomer kinetics for agents administered as racemates, particularly when relating concentrations to pharmacologic response.

The purpose of this study was to establish the rat left ventricle (LV) tissue slice system for examination of norepinephrine (NE) release from sympathetic nerve terminals. Moreover, initial experiments were performed to use the LV tissue slice system to examine differences in NE uptake and release following cardiac pressure overload induced by abdominal aortic constriction (AC). Kinetic parameters (Vmax, Km) for the specific uptake of [3H]-NE demonstrated high affinity (Km, 1.94 +/- 0.83 microM) and moderate capacity uptake (Vmax, 182 +/- 6 fmol/mg/weight/min). Following 10 days of pressure overload, the Vmax for [3H]-NE uptake was significantly reduced (by 46%) in LV slices from AC rats compared to sham-operated (SO) controls. In control rat LV slices preloaded with [3H]-NE, electrically evoked [3H]-overflow was calcium- and stimulus pulse number-dependent. The neuronal uptake inhibitor, desipramine (DMI), increased (by 60%) evoked [3H]-overflow from LV slices. The alpha2-agonist, UK14304, decreased evoked [3H]-overflow from LV slices in a concentration-dependent manner (maximal reduction of 75%). The beta2-agonist, salbutamol, increased evoked [3H]-overflow from LV slices in a concentration-dependent manner (maximal increase of 200%). In separate experiments, the LV tissue slice system was used to examine the effect of pressure overload on evoked [3H]-overflow. Following 10 days of pressure overload, evoked [3H]-overflow from LV slices of AC rats was increased (by 50%) compared to SO control. Increases in evoked [3H]-overflow from LV slices of AC rats compared to SO controls remained evident in the presence of DMI. These results demonstrate the relative importance of NE release and uptake using an in vitro LV tissue slice system. Sympathetic nerve terminals innervating rat LV were demonstrated to possess functional presynaptic alpha2- and beta2-adrenergic receptors. Finally, using this LV tissue slice system, reductions in the uptake velocity and increases in evoked NE release were demonstrated in response to acute cardiac pressure overload.

Study Objectives: To evaluate whether variability in S-metoprolol kinetics and lymphocyte beta 2-receptor-mediated cyclic adenosine monophosphate (cAMP) accumulation is related to the variability in antihypertensive response to metoprolol of black men., Design: Prospective, unblinded study., Setting: University-based preventive medicine clinic., Patients: Twelve hypertensive black men., Measurements and Main Results: Ambulatory blood pressure was measured over 24 hours before and after metoprolol administration. Ex vivo responsiveness of lymphocyte beta 2-receptors to isoproterenol was established for each subject before initiating metoprolol therapy. Plasma samples were collected over 12 hours at the conclusion of the study, from which metoprolol enantiomer concentrations were determined by chiral high-performance liquid chromatography, and kinetic values were calculated. The 24-hour ambulatory blood pressure responses to metoprolol were highly variable, with systolic blood pressure responses ranging from -13 to +33 mm Hg and diastolic blood pressure responses ranging from -15 to +15 mm Hg. There was a significant relationship between the metoprolol-induced change in systolic blood pressure and the maximum lymphocyte beta 2-receptor cAMP production (y = 0.47x-7.79; r2 = 0.49, p < 0.05) such that those with the highest maximum cAMP production had the greatest blood pressure increases during metoprolol therapy. There was no relationship between S-metoprolol concentration and blood pressure response. Mean oral clearance values for S- and R-metoprolol were 1320 and 2346 ml/minute, respectively., Conclusions: Lymphocyte beta 2-receptor data suggest that individuals most responsive to beta-receptor stimulation may be at greatest risk of blood pressure elevation during beta 2-receptor blockade. The metoprolol enantiomer kinetic data are markedly different from previously published data and may represent racial differences in pharmacokinetics.

Twelve hypertensive black males completed the study, which was conducted to evaluate the effect of metoprolol on 24-h ambulatory blood pressure (ABP). Study participants took 50 mg to 100 mg metoprolol twice daily for a minimum of 3 weeks. Metoprolol had no significant effect on blood pressure (147/90 +/- 11/8 mm Hg v 151/88 +/- 16/8 mm Hg, baseline v treated, respectively) in spite of causing significant reductions in heart rate (87 +/- 9 beats/min v 69 +/- 7 beats/min, P < .001). Only one subject had a > or = 10 mm Hg decrease in 24-h diastolic blood pressure. The nighttime fall in blood pressure was minimized by metoprolol and clinically significant increases in daytime or nighttime blood pressure were noted in 58% of patients. Metoprolol therapy failed to lower blood pressure and eliminated the normal nighttime decline in blood pressure. Since the nighttime decline in blood pressure is thought to protect against target organ damage, it may be important to identify antihypertensive agents which preserve or enhance the nighttime blood pressure dip.