Drug-induced QT interval prolongation in patients with heart failure with preserved ejection fraction.

Heart failure (HF) with reduced ejection fraction (HFrEF) is a risk factor for drug-induced QT interval prolongation. It is unknown if HF with preserved ejection fraction (HFpEF) is also associated with an increased risk. Dofetilide and sotalol are potent QT interval-prolonging agents that are frequently used in patients with HFpEF, in whom atrial fibrillation is a common comorbidity. We tested the hypothesis that the risk of QT interval prolongation associated with dofetilide and sotalol is increased in patients with HFpEF. We conducted a retrospective cohort study conducted using electronic health records from the Indiana Network for Patient Care (January 31, 2010 -May 3, 2021). After removing patients with overlapping diagnoses of HFpEF and HFrEF, no diagnosis code, and absence of QT interval records, we identified patients taking dofetilide or sotalol among three groups: HFrEF (n = 138), HFpEF (n = 109), and no HF (n = 729). QT prolongation was defined as heart rate-corrected QT (QTc) > 500 ms during dofetilide/sotalol therapy. Unadjusted odds ratios (OR) for QT prolongation were determined by univariate analysis. Adjusted ORs were determined by generalized estimating equations (GEE) with logit link to account for an individual cluster with different times of hospitalization and covariates. QTc prolongation associated with dofetilide or sotalol occurred in 53.2%, 71.7% and 30.0% of patients with HFpEF, HFrEF, and patients with no HF, respectively. After adjusting for age, sex, race, serum potassium and magnesium concentrations, kidney function, concomitant drug therapy, and comorbid conditions, the adjusted odds of QTc prolongation were significantly higher in patients with HFpEF [OR = 1.98 (95% CI 1.17-3.33)], and in those with HFrEF [OR = 5.23, (3.15-8.67)], compared to those with no evidence of HF. The odds of QT prolongation among inpatients receiving dofetilide or sotalol were increased in patients with HFpEF and HFrEF compared to those who did not have HF.

Prolonged Exposure to Remdesivir Inhibits the Human Ether-A-Go-Go-Related Gene Potassium Current.

ABSTRACT: Remdesivir, approved for the treatment of COVID-19, has been associated with heart-rate corrected QT interval (QTc) prolongation and torsade de pointes in case reports. However, data are conflicting regarding the ability of remdesivir to inhibit the human ether-a-go-go-related gene (hERG) -related current. The objective of this study was to investigate the effects remdesivir and its primary metabolite, GS-441524, on hERG-related currents. Human embryonic kidney 293 cells stably expressing hERG were treated with various concentrations of remdesivir and GS-441524. The effects of acute and prolonged exposure on hERG-related current were assessed using whole-cell configuration of voltage-clamp protocols. Acute exposure to remdesivir and GS-441524 had no effect on hERG currents and the half-activation voltage (V 1/2 ). Prolonged treatment with 100 nM and 1 µM remdesivir significantly reduced peak tail currents and hERG current density. The propensity for remdesivir to prolong QTc intervals and induce torsade de pointes in predisposed patients warrants further investigation.

Effects of oxycodone pharmacogenetics on postoperative analgesia and related clinical outcomes in children: a pilot prospective study.

Background: Variability in the pharmacokinetics and pharmacodynamics of oxycodone in children undergoing surgery could be due to genetic polymorphisms. Materials & methods: The authors studied the association between clinical outcomes and pharmacogenes in children undergoing major surgery. A total of 89 children (35 undergoing pectus excavatum repair and 54 undergoing spinal fusion) were recruited. Results: OPRM1 SNP rs6902403 showed an association with maximum pain score and total morphine equivalent dose (p < 0.05). Other polymorphisms in OPRM1 SNP, PXR, COMT and ABCB1 were also shown to be associated with average morphine equivalent dose, length of hospital stay and maximum surgical pain (p < 0.05). Conclusion: This study demonstrates novel associations between the above pharmacogenes and oxycodone's pharmacokinetics as well as postoperative outcomes in children. Clinical trial registration: NCT03495388 (ClinicalTrials.gov).

Association of QT interval-prolonging drugs with clinical trial eligibility in patients with advanced cancer.

Introduction: Drug-induced prolongation of the heart rate-corrected QT interval (QTc) is associated with increased risk for the potentially fatal arrhythmia torsades de pointes. Due to arrhythmia risk, clinical trials with cancer therapeutics often exclude patients based on thresholds for QTc prolongation. Our objective was to assess associations between prescriptions for QT-prolonging drugs and the odds of meeting cancer trial exclusionary QTc thresholds in a cohort of adults with advanced cancer. Methods: Electronic health records were retrospectively reviewed for 271 patients seen at our institutional molecular solid tumor clinic. Collected data included demographics, QTc measurements, ventricular arrhythmia-related diagnoses, and all inpatient and outpatient prescriptions. Potential associations were assessed between demographic and clinical variables, including prescriptions for QT-prolonging drugs, and QTc measurements. Results: Women had longer median QTc measurements than men (p = 0.030) and were prescribed more QT-prolonging drugs during the study (p = 0.010). In all patients, prescriptions for QT-prolonging drugs were associated with longer median and maximum QTc measurements at multiple assessed time points (i.e., for QT-prolonging drugs prescribed within 10, 30, 60, and 90 days of QTc measurements). Similarly, the number of QT-prolonging drugs prescribed was correlated with longer median and maximum QTc measurements at multiple time points. Common QTc-related exclusionary criteria were collected from a review of ClinicalTrials.gov for recent cancer clinical trials. Based on common exclusion criteria, prescriptions for QT-prolonging drugs increased the odds of trial exclusion. Conclusion: This study demonstrates that prescriptions for QT-prolonging drugs were associated with longer QTc measurements and increased odds of being excluded from cancer clinical trials.

Pharmacokinetic modeling of R and S-Methadone and their metabolites to study the effects of various covariates in post-operative children.

Methadone is a synthetic opioid used as an analgesic and for the treatment of opioid abuse disorder. The analgesic dose in the pediatric population is not well-defined. The pharmacokinetics (PKs) of methadone is highly variable due to the variability in alpha-1 acid glycoprotein (AAG) and genotypic differences in drug-metabolizing enzymes. Additionally, the R and S enantiomers of methadone have unique PK and pharmacodynamic properties. This study aims to describe the PKs of R and S methadone and its metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in pediatric surgical patients and to identify sources of inter- and intra-individual variability. Children aged 8-17.9 years undergoing orthopedic surgeries received intravenous methadone 0.1 mg/kg intra-operatively followed by oral methadone 0.1 mg/kg postoperatively every 12 h. Pharmacokinetics of R and S methadone and EDDP were determined using liquid chromatography tandem mass spectrometry assays and the data were modeled using nonlinear mixed-effects modeling in NONMEM. R and S methadone PKs were well-described by two-compartment disposition models with first-order absorption and elimination. EDDP metabolites were described by one compartment disposition models with first order elimination. Clearance of both R and S methadone were allometrically scaled by bodyweight. CYP2B6 phenotype was a determinant of the clearance of both the enantiomers in an additive gene model. The intronic CYP3A4 single-nucleotide polymorphism (SNP) rs2246709 was associated with decreased clearance of R and S methadone. Concentrations of AAG and the SNP of AAG rs17650 independently increased the volume of distribution of both the enantiomers. The knowledge of these important covariates will aid in the optimal dosing of methadone in children.

Novel associations between CYP2B6 polymorphisms, perioperative methadone metabolism and clinical outcomes in children.

Aim: Methadone exhibits significant variability in clinical response. This study explores the genetic influence of variable methadone pharmacokinetics. Methods: This is a prospective study of methadone in children undergoing major surgery. CYP2B6 genotyping, plasma methadone and metabolite levels were obtained. Clinical outcomes include pain scores and postoperative nausea and vomiting (PONV). Results:CYP2B6 poor metabolizers (*6/*6) had >twofold lower methadone metabolism compared with normal/rapid metabolizers. The incidence of PONV was 4.7× greater with CYP2B6 rs1038376 variant. AG/GG variants of rs2279343 SNP had 2.86-fold higher incidence of PONV compared with the wild variant (AA). Nominal associations between rs10500282, rs11882424, rs4803419 and pain scores were observed. Conclusion: We have described novel associations between CYP2B6 genetic variants and perioperative methadone metabolism, and associations with pain scores and PONV.

A Novel Perioperative Multidose Methadone-Based Multimodal Analgesic Strategy in Children Achieved Safe and Low Analgesic Blood Methadone Levels Enabling Opioid-Sparing Sustained Analgesia With Minimal Adverse Effects.

BACKGROUND: Intraoperative methadone, a long-acting opioid, is increasingly used for postoperative analgesia, although the optimal methadone dosing strategy in children is still unknown. The use of a single large dose of intraoperative methadone is controversial due to inconsistent reductions in total opioid use in children and adverse effects. We recently demonstrated that small, repeated doses of methadone intraoperatively and postoperatively provided sustained analgesia and reduced opioid use without respiratory depression. The aim of this study was to characterize pharmacokinetics, efficacy, and safety of a multiple small-dose methadone strategy. METHODS: Adolescents undergoing posterior spinal fusion (PSF) for idiopathic scoliosis or pectus excavatum (PE) repair received methadone intraoperatively (0.1 mg/kg, maximum 5 mg) and postoperatively every 12 hours for 3-5 doses in a multimodal analgesic protocol. Blood samples were collected up to 72 hours postoperatively and analyzed for R-methadone and S-methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidene (EDDP) metabolites, and alpha-1 acid glycoprotein (AAG), the primary methadone-binding protein. Peak and trough concentrations of enantiomers, total methadone, and AAG levels were correlated with clinical outcomes including pain scores, postoperative nausea and vomiting (PONV), respiratory depression, and QT interval prolongation. RESULTS: The study population included 38 children (10.8-17.9 years): 25 PSF and 13 PE patients. Median total methadone peak plasma concentration was 24.7 (interquartile range [IQR], 19.2-40.8) ng/mL and the median trough was 4.09 (IQR, 2.74-6.4) ng/mL. AAG concentration almost doubled at 48 hours after surgery (median = 193.9, IQR = 86.3-279.5 µg/mL) from intraoperative levels (median = 87.4, IQR = 70.6-115.8 µg/mL; P < .001), and change of AAG from intraoperative period to 48 hours postoperatively correlated with R-EDDP (P < .001) levels, S-EDDP (P < .001) levels, and pain scores (P = .008). Median opioid usage was minimal, 0.66 (IQR, 0.59-0.75) mg/kg morphine equivalents/d. No respiratory depression (95% Wilson binomial confidence, 0-0.09) or clinically significant QT prolongation (median = 9, IQR = -10 to 28 milliseconds) occurred. PONV occurred in 12 patients and was correlated with morphine equivalent dose (P = .005). CONCLUSIONS: Novel multiple small perioperative methadone doses resulted in safe and lower blood methadone levels, <100 ng/mL, a threshold previously associated with respiratory depression. This methadone dosing in a multimodal regimen resulted in lower blood methadone analgesia concentrations than the historically described minimum analgesic concentrations of methadone from an era before multimodal postoperative analgesia without postoperative respiratory depression and prolonged corrected QT (QTc). Larger studies are needed to further study the safety and efficacy of this methadone dosing strategy.

Letrozole targets the human ether-a-go-go-related gene potassium current in glioblastoma.

Aberrant expression of human ether-a-go-go-related gene (hERG) potassium channels has been implicated in the pathophysiology of glioblastoma (GBM). Letrozole has demonstrated efficacy in pre-clinical GBM models. The objective of this research was to assess the potential for hERG inhibition by letrozole to mediate efficacy in GBM. hERG currents were assessed using patch-clamp electrophysiology in an overexpression system during treatment with letrozole, exemestane or vehicle (dimethyl sulphoxide). Relative to vehicle, peak hERG tail current density was reduced when treated with 300 nmol/L and 1 µmol/L letrozole but not when treated with exemestane (up to 1 µmol/L). Cell proliferation was assessed in cultured glioblastoma cell lines (U87 and U373) treated with letrozole, exemestane, doxazosin (hERG blocker) or vehicle. Letrozole, but not exemestane, reduced cell proliferation relative to vehicle in U87 and U373 cells. The associations between expression of hERG (KCNH2), aromatase (CYP19A1) and the oestrogen receptors (ESR1 and ESR2) and time to all-cause mortality were assessed in GBM patients within The Cancer Genome Atlas (TCGA) database. hERG expression was associated with reduced overall survival in the TCGA GBM cohort. Future work is warranted to investigate hERG expression as a potential biomarker to predict the therapeutic potential of hERG inhibitors in GBM.

Transdermal Testosterone Attenuates Drug-Induced Lengthening of Both Early and Late Ventricular Repolarization in Older Men.

We have previously reported that transdermal testosterone attenuates drug-induced QT interval lengthening in older men. However, it is unknown whether this is due to modulation of early ventricular repolarization, late repolarization, or both. In a secondary analysis of a prospective, randomized, double-blind, placebo-controlled three-way crossover study, we determined if transdermal testosterone and oral progesterone attenuate drug-induced lengthening of early and late ventricular repolarization, represented by the electrocardiographic measurements J-Tpeak c and Tpeak -Tend , respectively, as well as Tpeak -Tend /QT, a measure of transmural dispersion of repolarization. Male volunteers ≥ 65 years of age (n = 14) were randomized to receive transdermal testosterone 100 mg, oral progesterone 400 mg, or matching transdermal/oral placebo daily for 7 days. On the morning following the seventh day, subjects received intravenous ibutilide 0.003 mg/kg, after which electrocardiograms were performed serially. One subject was excluded due to difficulty in T-wave interpretation. Pre-ibutilide J-Tpeak c was lower during the testosterone phase than during progesterone and placebo (216 ± 23 vs. 227 ± 28 vs. 227 ± 21 ms, P = 0.002). Maximum post-ibutilide J-Tpeak c was also lower during the testosterone phase (233 ± 22 vs. 246 ± 29 vs. 248 ± 23 ms, P < 0.0001). Pre-ibutilide Tpeak -Tend was not significantly different during the three phases, but maximum post-ibutilide Tpeak -Tend was lower during the testosterone phase (80 ± 12 vs. 89 ± 18 vs. 86 ± 15 ms, P = 0.002). Maximum Tpeak -Tend /QT was also lower during the testosterone phase (0.199 ± 0.023 vs. 0.216 ± 0.035 vs. 0.209 ± 0.031, P = 0.005). Progesterone exerted minimal effect on drug-induced lengthening of J-Tpeak c, and no effect on Tpeak -Tend or Tpeak -Tend /QT. Transdermal testosterone attenuates drug-induced lengthening of both early and late ventricular repolarization in older men.

Neurohormonal Regulation of IKs in Heart Failure: Implications for Ventricular Arrhythmogenesis and Sudden Cardiac Death.

Heart failure (HF) results in sustained alterations in neurohormonal signaling, including enhanced signaling through the sympathetic nervous system and renin-angiotensin-aldosterone system pathways. While enhanced sympathetic nervous system and renin-angiotensin-aldosterone system activity initially help compensate for the failing myocardium, sustained signaling through these pathways ultimately contributes to HF pathophysiology. HF remains a leading cause of mortality, with arrhythmogenic sudden cardiac death comprising a common mechanism of HF-related death. The propensity for arrhythmia development in HF occurs secondary to cardiac electrical remodeling that involves pathological regulation of ventricular ion channels, including the slow component of the delayed rectifier potassium current, that contribute to action potential duration prolongation. To elucidate a mechanistic explanation for how HF-mediated electrical remodeling predisposes to arrhythmia development, a multitude of investigations have investigated the specific regulatory effects of HF-associated stimuli, including enhanced sympathetic nervous system and renin-angiotensin-aldosterone system signaling, on the slow component of the delayed rectifier potassium current. The objective of this review is to summarize the current knowledge related to the regulation of the slow component of the delayed rectifier potassium current in response to HF-associated stimuli, including the intracellular pathways involved and the specific regulatory mechanisms.

Pharmacogenomics of methadone: a narrative review of the literature.

Background: Methadone, a synthetic opioid with longer duration of action and lower abuse potential compared with morphine, is used to prevent opioid withdrawal, as well as to manage chronic and acute surgical pain. The variability in response to methadone has been widely recognized. The purpose of this article is to review the literature on the pharmacogenetic factors underlying this variability. Materials & methods: This is a narrative overview of the literature on the genetic variants affecting pharmacodynamics and pharmacokinetics of methadone, retrieved from searches of databases such as PubMed and google scholar. Discussion: Clinical responses to methadone may be affected by genetic variants in the opioidergic, dopaminergic and neurotrophic pathways. Polymorphisms in genes related to disposition and elimination of methadone alter the pharmacokinetics, and possibly pharmacodynamics of methadone. Cytochrome P450 enzymes and P-glycoprotein variants contribute to the interindividual variability in methadone pharmacokinetics. Evidence for single gene variants affecting methadone response remains weak. Multiple genetic variants must be considered in conjunction to improve predictive ability. Conclusion: Evidence remains scarce at this time, to recommend pharmacogenetic testing before methadone administration. Well-powered clinical studies are needed with population pharmacokinetic-pharmacodynamic modeling and multigenetic signature-based predictions to enable tailored use of methadone in clinical practice.

Inhibition of Human Ether-A-Go-Go-Related Gene (hERG) Potassium Current by the Novel Sotalol Analogue, Soestalol.

The clinical utility of intravenous sotalol is limited due to an extended half-life combined with the potential to generate life-threatening arrhythmias. The authors developed a novel sotalol analogue, soestalol, with an ester linkage introduced to the molecule to shorten half-life. Their hypothesis was that soestalol, but not the acid metabolite, would inhibit the hERG potassium current. Whole-cell, voltage-clamp experiments were performed on cells expressing hERG. Soestalol inhibited outward IhERG tail current density in a manner similar to conventional sotalol. Additionally, soestalol right shifted the voltage dependence of activation. These results warrant further assessment of soestalol as a short-acting, Class III antiarrhythmic drug.

Enhanced Response to Drug-Induced QT Interval Lengthening in Patients with Heart Failure with Preserved Ejection Fraction.

BACKGROUND: Patients with heart failure (HF) with reduced ejection fraction demonstrate enhanced response to drug-induced QT interval lengthening and are at increased risk for torsades de pointes. The influence of HF with preserved ejection fraction (HFpEF) on response to drug-induced QT lengthening is unknown. METHODS AND RESULTS: We administered intravenous ibutilide 0.003 mg/kg to 10 patients with HFpEF and 10 age- and sex-matched control subjects without HF. Serial 12-lead electrocardiograms were obtained for determination of QT intervals. Demographics, maximum serum ibutilide concentrations, area under the serum ibutilide concentration vs time curves, and baseline Fridericia-corrected QT (QTF) (417 ± 14 vs 413 ± 15 ms, P = .54) were similar in the HFpEF and control groups. Area under the effect (QTFvs time) curve (AUEC) from 0 to 1.17 hours during and following the ibutilide infusion was greater in the HFpEF group (519 ± 19 vs 497 ± 18 ms·h, P= .04), as was AUEC from 0 to 8.17 hours (3576 ± 125 vs 3428 ± 161 ms·h, P = .03) indicating greater QTF interval exposure. Maximum QTF (454 ± 15 vs 443 ± 22 ms, P = .18) and maximum percent increase in QTF from baseline (8.2 ± 2.1 vs 6.7 ± 1.9%, P = .10) in the 2 groups were not significantly different. CONCLUSIONS: HFpEF is associated with enhanced response to drug-induced QT interval lengthening.

Progesterone Metabolites Inhibit the Human Ether-a-go-go-Related Gene and Predict QT Interval Length.

A decrease in the human ether-a-go-go-related gene (hERG/KCNH2)-related channel has been linked to intrauterine fetal death. The formation of cytochrome P450 (CYP) 3A-mediated progesterone metabolites, 6-beta-hydroxy-progesterone (6ß-OHP) and 16α-hydroxy-progesterone (16α-OHP), is variable among adults and differs from fetal metabolism. The primary objective of this study was to assess the potential for progesterone metabolites to inhibit hERG-related current and predict QTc intervals. Whole-cell voltage-clamp electrophysiology was performed on human embryonic kidney 293 cells stably expressing hERG exposed to progesterone or metabolites. Both 6ß-OHP and 16α-OHP positively shifted the voltage dependence of activation relative to vehicle from -4.0 ± 0.8 to -0.3 ± 0.8 mV, P < .01; and 1.0 ± 0.6 mV, P < .01, respectively. In addition, 6ß-OHP decreased maximal outward tail currents from 49.4 ± 4.9 to 32.5 ± 4.1 pA/pF, P < 0.01, and reduced the expression of fully glycosylated hERG by 42%. Healthy female subjects were administered progesterone 400 mg orally for 7 days, ibutilide 0.003 mg/kg was infused, and serial electrocardiograms and blood samples collected. Relationships between rate-corrected QT intervals (QTcI) with circulating hormones and metabolites were assessed. The 6ß-OHP and 16α-OHP metabolites were independent predictors of QTcI intervals prior to and following ibutilide administration. In conclusion, the progesterone metabolites formed via CYP3A cause inhibitory effects on hERG channels and predict QTcI intervals in healthy women pretreated with progesterone. Further study into maternal and fetal exposure to these metabolites and potential to prolong cardiac repolarization is warranted.

MicroRNA 362-3p Reduces hERG-related Current and Inhibits Breast Cancer Cells Proliferation.

BACKGROUND/AIM: hERG potassium channels enhance tumor invasiveness and breast cancer proliferation. MicroRNA (miRNA) dysregulation during cancer controls gene regulation. The objective of this study was to identify miRNAs that regulate hERG expression in breast cancer. MATERIALS AND METHODS: Putative miRNAs targeting hERG were identified by bioinformatic approaches and screened using a 3'UTR luciferase assay. Functional assessments of endogenous hERG regulation were made using whole-cell electrophysiology, proliferation assays, and cell-cycle analyses following miRNA, hERG siRNA, or control transfection. RESULTS: miR-362-3p targeted hERG 3'UTR and was associated with higher survival rates in patients with breast cancer (HR=0.39, 95%CI=0.18-0.82). Enhanced miR-362-3p expression reduced hERG expression, peak current, and cell proliferation in cultured breast cancer cells (p<0.05). CONCLUSION: miR-362-3p mediates the transcriptional regulation of hERG and is associated with survival in breast cancer. The potential for miR-362-3p to serve as a biomarker and inform therapeutic strategies warrants further investigation.

Progesterone pretreatment reduces the incidence of drug-induced torsades de pointes in atrioventricular node-ablated isolated perfused rabbit hearts.

INTRODUCTION: Higher progesterone concentrations are protective against drug-induced prolongation of ventricular repolarization. We tested the hypothesis that pretreatment with progesterone reduces the incidence of drug-induced torsades de pointes (TdP). METHODS AND RESULTS: Female New Zealand white rabbits (2.5-3.2 kg) underwent ovariectomy and were randomized to undergo implantation with subcutaneous 21-day sustained release pellets containing progesterone 50 mg (n = 22) or placebo (n = 23). After 20 days, hearts were excised, mounted, and perfused with modified Krebs-Henseleit solution. The atrioventricular (AV) node was destroyed manually. Following a 15-minute equilibration period, hearts were perfused with dofetilide 100 nM for 30 minutes, during which the electrocardiogram was recorded continuously. Incidences of spontaneous TdP, other ventricular arrhythmias and mean QTc intervals were compared. Median serum progesterone concentrations were higher in progesterone vs placebo-treated rabbits (3.8 [range, 2.8-5.1] vs 0.7 [0.4-1.7] ng/mL, P < 0.0001). Median serum estradiol concentrations were similar (58 [22-72] vs 53 [34-62] pg/mL), P = 0.79). The incidence of TdP was lower in hearts from progesterone-treated rabbits (27% vs 61%, P = 0.049). The incidences of bigeminy (36% vs 74%, P = 0.03) and trigeminy (18% vs 57%, P = 0.01) were also lower in hearts from progesterone-treated rabbits. There was no significant difference between groups in incidence of couplets (59% vs 74%, P = 0.54) or monomorphic ventricular tachycardia (14% vs 30%, P = 0.28). Maximum QT c interval and short-term beat-to-beat QT interval variability during dofetilide perfusion were significantly shorter in hearts from progesterone-treated rabbits. CONCLUSIONS: Pretreatment with progesterone reduces the incidence of drug-induced TdP, bigeminy, and trigeminy in isolated perfused AV node-ablated rabbit hearts.

Calcium/calmodulin-dependent protein kinase II regulation of IKs during sustained ß-adrenergic receptor stimulation.

BACKGROUND: Sustained ß-adrenergic receptor (ß-AR) stimulation causes pathophysiological changes during heart failure (HF), including inhibition of the slow component of the delayed rectifier potassium current (IKs). Aberrant calcium handling, including increased activation of calcium/calmodulin-dependent protein kinase II (CaMKII), contributes to arrhythmia development during HF. OBJECTIVE: The purpose of this study was to investigate CaMKII regulation of KCNQ1 (pore-forming subunit of IKs) during sustained ß-AR stimulation and associated functional implications on IKs. METHODS: KCNQ1 phosphorylation was assessed using liquid chromatography-tandem mass spectrometry after sustained ß-AR stimulation with isoproterenol (ISO). Peptide fragments corresponding to KCNQ1 residues were synthesized to identify CaMKII phosphorylation at the identified sites. Dephosphorylated (alanine) and phosphorylated (aspartic acid) mimics were introduced at identified residues. Whole-cell, voltage-clamp experiments were performed in human endothelial kidney 293 cells coexpressing wild-type or mutant KCNQ1 and KCNE1 (auxiliary subunit) during ISO treatment or lentiviral δCaMKII overexpression. RESULTS: Novel KCNQ1 carboxy-terminal sites were identified with enhanced phosphorylation during sustained ß-AR stimulation at T482 and S484. S484 peptides demonstrated the strongest δCaMKII phosphorylation. Sustained ß-AR stimulation reduced IKs activation (P = .02 vs control) similar to the phosphorylated mimic (P = .62 vs sustained ß-AR). Individual phosphorylated mimics at S484 (P = .04) but not at T482 (P = .17) reduced IKs function. Treatment with CN21 (CaMKII inhibitor) reversed the reductions in IKs vs CN21-Alanine control (P < .01). δCaMKII overexpression reduced IKs similar to ISO treatment in wild type (P < .01) but not in the dephosphorylated S484 mimic (P = .99). CONCLUSION: CaMKII regulates KCNQ1 at S484 during sustained ß-AR stimulation to inhibit IKs. The ability of CaMKII to inhibit IKs may contribute to arrhythmogenicity during HF.

Iterative Development and Evaluation of a Pharmacogenomic-Guided Clinical Decision Support System for Warfarin Dosing.

OBJECTIVE: Pharmacogenomic-guided dosing has the potential to improve patient outcomes but its implementation has been met with clinical challenges. Our objective was to develop and evaluate a clinical decision support system (CDSS) for pharmacogenomic-guided warfarin dosing designed for physicians and pharmacists. METHODS: Twelve physicians and pharmacists completed 6 prescribing tasks using simulated patient scenarios in two iterations (development and validation phases) of a newly developed pharmacogenomic-driven CDSS prototype. For each scenario, usability was measured via efficiency, recorded as time to task completion, and participants' perceived satisfaction which were compared using Kruskal-Wallis and Mann Whitney U tests, respectively. Debrief interviews were conducted and qualitatively analyzed. Usability findings from the first (i.e. development) iteration were incorporated into the CDSS design for the second (i.e. validation) iteration. RESULTS: During the CDSS validation iteration, participants took more time to complete tasks with a median (IQR) of 183 (124-247) seconds versus 101 (73.5-197) seconds in the development iteration (p=0.01). This increase in time on task was due to the increase in time spent in the CDSS corresponding to several design changes. Efficiency differences that were observed between pharmacists and physicians in the development iteration were eliminated in the validation iteration. The increased use of the CDSS corresponded to a greater acceptance of CDSS recommended doses in the validation iteration (4% in the first iteration vs. 37.5% in the second iteration, p<0.001). Overall satisfaction did not change statistically between the iterations but the qualitative analysis revealed greater trust in the second prototype. CONCLUSIONS: A pharmacogenomic-guided CDSS has been developed using warfarin as the test drug. The final CDSS prototype was trusted by prescribers and significantly increased the time using the tool and acceptance of the recommended doses. This study is an important step toward incorporating pharmacogenomics into CDSS design for clinical testing.