Safety of non-antiarrhythmic drugs that prolong the QT interval or induce torsade de pointes: an overview

Validation of smartwatch electrocardiogram intervals in children compared to standard 12 lead electrocardiograms

Lay people are now able to obtain one-lead electrocardiograms (ECG) using smartwatches, which facilitates documentation of arrhythmias. The accuracy of smartwatch derived ECG intervals has not been validated in children though. Home-based monitoring of ECG intervals using a smartwatch could improve monitoring of children, e.g. when taking QTc prolonging medications. The aim of this study was to validate the ECG intervals measured by smartwatch in comparison to standard 12-lead ECGs in children and adolescents. Prospective study of children (age 5-17 years) at the outpatient clinic of a national pediatric heart center. Patients underwent a smartwatch ECG (ScanWatch, Withings) and a simultaneous standard 12-lead ECG. ECG intervals were measured both automatically and manually from the smartwatch ECG and the 12-lead ECG. Intraclass correlation coefficients and Bland-Altman plots were performed. 100 patients (54% male, median age 12.9 (IQR 8.7-15.6) were enrolled. The ICC calculated from the automated smartwatch and automated 12-lead ECG were excellent for heart rate (ICC 0.97, p < 0.001), good for the PR and QT intervals (ICC 0.86 and 0.8, p < 0.001), and moderate for the QRS duration and QTc interval (ICC 0.7 and 0.53, p < 0.001). When using manual measurements for the smartwatch ECG, validity was improved for the PR interval (ICC 0.93, p < 0.001), QRS duration (ICC 0.92, p < 0.001), QT (ICC 0.95, p < 0.001) and QTc interval (ICC 0.84, p < 0.001).

CONCLUSION

Automated smartwatch intervals are most reliable measuring the heart rate. The automated smartwatch QTc intervals are less reliable, but this may be improved by manual measurements.

WHAT IS KNOWN

In adults, smartwatch derived ECG intervals measured manually have previously been shown to be accurate, though agreement for automated QTc may be fair.

WHAT IS NEW

In children, automated smartwatch QTc intervals are less reliable than RR, PR, QRS and uncorrected QT interval. Accuracy of the QTc can be improved by peroforming manual measurements.

A simple accurate method for concentration-QTc analysis in preclinical animal models

INTRODUCTION

In preclinical cardiovascular safety pharmacology studies, statistical analysis of the rate corrected QT interval (QTc) is the focus for predicting QTc interval changes in the clinic. Modeling of a concentration/QTc relationship, common clinically, is limited due to minimal pharmacokinetic (PK) data in nonclinical testing. It is possible, however, to relate the average drug plasma concentration from sparse PK samples over specific times to the mean corrected QTc. We hypothesize that averaging drug plasma concentration and the QTc-rate relationship over time provides a simple, accurate concentration-QTc relationship bridging statistical and concentration/QTc modeling.

METHODS

Cardiovascular telemetry studies were conducted in non-human primates (NHP; n = 48) and canines (n = 8). Pharmacokinetic samples were collected on separate study days in both species. Average plasma concentrations for specific intervals (CAverage0-X) were calculated for moxifloxacin in canines and NHP using times corresponding to super-intervals for the QTc data statistical analysis. The QTc effect was calculated for each super-interval using a linear regression correction incorporating QT and HR data from the whole super-interval. The concentration QTc effects were then modeled.

RESULTS

In NHP, a 10.9 ± 0.06 ms (mean ± 95% CI) change in QTc was detected at approximately 1.5× the moxifloxacin plasma concentration that causes a 10 ms QTc change in humans, based on a 0-24 h super-interval. When simulating a drug without QT effects, mock, no effect on QTc was detected at up to 3× the clinical concentration. Similarly, in canines, a 16.6 ± 0.1 ms change was detected at 1.7× critical clinical moxifloxacin concentration, and a 0.04 ± 0.1 ms change was seen for mock.

CONCLUSIONS

While simultaneous PK and QTc data points are preferred, practical constraints and the need for QTc averaging did not prevent concentration-QTc analyses. Utilizing a 0-24 h super-interval method illustrates a simple and effective method to address cardiovascular questions when preclinical drug exposures exceed clinical concentrations.

Prevalence, Attributes, and Risk Factors of QT-Interval-Prolonging Drugs and Potential Drug-Drug Interactions in Cancer Patients: A Prospective Study in a Tertiary Care Hospital

Introduction Cancer chemotherapy regimens include multiple classes of adjuvant drugs as supportive therapy. Because of the concurrent intake of other drugs (like antiemetics, antidepressants, analgesics, and antimicrobials), there is a heightened risk for possible QT interval prolongation. There is a dearth of evidence in the literature regarding the usage of QT-prolonging anticancer drugs and associated risk factors that have the propensity to prolong QT interval. The purpose was to explore the extent of the use of QT-interval-prolonging drugs and potential QT-prolonging drug-drug interactions (QT-DDIs) in cancer patients attending OPD in a tertiary-care hospital. Methods This was a hospital-based, cross-sectional, observational study. Risk stratification of QT-prolonging drugs for torsades de pointes (TdP) was done by the Arizona Center for Education and Research on Therapeutics (AzCERT)/CredibleMeds-lists, and potential QT-DDIs were determined with four online DDI-checker-software. Results In 1331 cancer patients, the overall prevalence of potential QT-prolonging drug utilization was 97.3%. Ondansetron, pantoprazole, domperidone, and olanzapine were the most frequent QT-prolonging drugs in cancer patients. The top six antineoplastics with potential QT-prolonging and torsadogenic actions were capecitabine, oxaliplatin, imatinib, bortezomib, 5-fluorouracil, and bendamustine. Evidence-based pragmatic QTc interval prolongation risk assessment tools are imperative for cancer patients. Conclusion This study revealed a high prevalence of QT-prolonging drugs and QT-DDIs among cancer patients who are treated with anticancer and non-anticancer drugs. As a result, it's critical to take precautions, stay vigilant, and avoid QT-prolonging in clinical situations. Evidence-based pragmatic QTc interval prolongation risk assessment tools are needed for cancer patients.

Importance of Spatial Arrangement of Cardiomyocyte Network for Precise and Stable On-Chip Predictive Cardiotoxicity Measurement

One of the advantages of human stem cell-derived cell-based preclinical screening is the reduction of the false negative/positive misjudgment of lead compounds for predicting their effectiveness and risks during the early stage of development. However, as the community effect of cells was neglected in the conventional single cell-based in vitro screening, the potential difference in results caused by the cell number and their spatial arrangement differences has not yet been sufficiently evaluated. Here, we have investigated the effect of the community size and spatial arrangement difference for cardiomyocyte network response against the proarrhythmic compounds from the viewpoint of in vitro cardiotoxicity. Using three different typical types of cell networks of cardiomyocytes, small cluster, large square sheet, and large closed-loop sheet were formed in shaped agarose microchambers fabricated on a multielectrode array chip simultaneously, and their responses were compared against the proarrhythmic compound, E-4031. The interspike intervals (ISIs) in large square sheets and closed-loop sheets were durable and maintained stable against E-4031 even at a high dose of 100 nM. In contrast, those in the small cluster, which fluctuated even without E-4031, acquired stable beating reflecting the antiarrhythmic efficacy of E-4031 from a 10 nM medium dose administration. The repolarization index, field potential duration (FPD), was prolonged in closed-loop sheets with 10 nM E-4031, even though small clusters and large sheets remained normal at this concentration. Moreover, FPDs of large sheets were the most durable against E-4031 among the three geometries of cardiomyocyte networks. The results showed the apparent spatial arrangement dependence on the stability of their interspike intervals, and FPD prolongation, indicating the importance of the geometry control of cell networks for representing the appropriate response of cardiomyocytes against the adequate amount of compounds for in vitro ion channel measurement.

Pharmacovigilance of triazole antifungal agents: Analysis of the FDA adverse event reporting system (FAERS) database

Triazole antifungal drugs (TAD) are widely used to treat invasive fungal infections due to their broad antifungal spectrum and low toxicity. Despite their preference in the clinic, multiple Adverse Events (AE) are still reported each year.

OBJECTIVE

We aimed to characterize the distribution of Adverse Events associated with Triazole antifungal drugs in different systems and to identify Important Medical Events (IME) signals for Triazole antifungal drugs.

METHODS

The U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) was queried for Adverse Events related to Triazole antifungal drugs from 2012 to 2022. The Adverse Events caused by all other drugs and non-TAD antifungal drugs were analyzed as references. Reporting odds ratio and Bayesian confidence propagation neural network of information components were used to evaluate the association between Triazole antifungal drugs and Important Medical Events. Visual signal spectrum is mapped to identify potential adverse reaction signals.

RESULTS

Overall, 10,262 Adverse Events were reported to be associated with Triazole antifungal drugs, of which 5,563 cases were defined as Important Medical Events. Common adverse drug reactions (ADR) mentioned in the instructions such as delirium and hypokalemia were detected, as well as unlabeled ADRs such as rhabdomyolysis and hepatitis fulminant. Cholestasis, drug-induced liver injury, QT interval prolongation and renal impairment have notable signals in all Triazole antifungal drugs, with 50 percent of patients developing a severe clinical outcome. Isavuconazole had the lowest signal intensity and demonstrated a superior safety profile.

CONCLUSION

Most results are generally consistent with previous studies and are documented in the prescribing instructions, but some IMEs are not included, such as hepatitis fulminant. Additional pharmaco-epidemiological or experimental studies are required to validate the small number of unlabeled ADRs. TAD-related Important Medical Eventshave a considerable potential to cause clinically serious outcomes. Clinical use of Triazole antifungal drugs requires more attention.

Structure-Based Optimization of Coumestan Derivatives as Polyketide Synthase 13-Thioesterase(Pks13-TE) Inhibitors with Improved hERG Profiles for Mycobacterium tuberculosis Treatment

Pks13 was identified as a key enzyme involved in the final step of mycolic acid biosynthesis. We previously identified antitubercular coumestans that targeted Pks13-TE, and these compounds exhibited high potency both in vitro and in vivo. However, lead compound 8 presented potential safety concerns because it inhibits the hERG potassium channel in electrophysiology patch-clamp assays (IC₅₀ = 0.52 μM). By comparing the Pks13-TE-compound 8 complex and the ligand-binding pocket of the hERG ion channel, fluoro-substituted and oxazine-containing coumestans were designed and synthesized. Fluoro-substituted compound 23 and oxazine-containing coumestan 32 showed excellent antitubercular activity against both drug-susceptible and drug-resistant Mtb strains (MIC = 0.0039-0.0078 μg/mL) and exhibited limited hERG inhibition (IC₅₀ ≥ 25 μM). Moreover, 32 exhibited improved metabolic stability relative to parent compound 8 while showing favorable bioavailability in mouse models via serum inhibition titration assays.

Prevalence of Pharmacologic Treatments for Chronic Obstructive Pulmonary Disease in Relation of Diagnosis of Dementia Among Nursing Homes Residents

OBJECTIVE

Chronic obstructive pulmonary disease (COPD) is a chronic disease affecting millions of older adults. We investigated the prevalence of nursing home (NH) residents with COPD and their pharmacologic treatment in relation to the diagnosis of dementia and the prevalence of potentially severe drug-drug interactions (DDIs) of COPD medications with drugs prescribed to treat comorbidities.

DESIGN

Retrospective cross-sectional multicentre study.

SETTING AND PARTICIPANTS

Individuals living in long-term care NHs.

METHODS

This cross-sectional cohort study was conducted in a sample of Italian long-term care NHs located throughout the country. Information on drug prescriptions, diseases, and sociodemographic characteristics was collected using medical records between 2018 and 2020. Potentially severe DDIs were analyzed using INTERCheck, developed by the Istituto di Ricerche Farmacologiche Mario Negri IRCCS.

RESULTS

Among the 2604 residents living in 27 NHs (mean age 86.4 ± 8.5 years; women 1995, 76.6%; number of drugs 7.3 ± 3.6), 306 had a diagnosis of COPD (11.8%) and 84 (27.5%) of them were treated with at least 1 medication for COPD (27.5%). Those without dementia had a higher prevalence of drugs for COPD than those with dementia (48% vs 20%, P < .0001). The most used classes for COPD were adrenergics in combination with corticosteroids (16.7%) and inhalant anticholinergics (14.7%). Among those receiving medications for COPD, 45 had at least 1 potentially severe DDI with medications for comorbidities (53.6%) and most of them were associated with an increased risk of QTc prolongation, as beta2 agonists with diuretics, antipsychotics or antidepressants.

CONCLUSIONS AND IMPLICATIONS

Most NH residents with COPD did not receive any medication for this disease despite the potential benefits. Residents with dementia received fewer COPD medications probably because of their compromised physical and cognitive status. One-half of the NH residents taking medication for COPD were exposed to an increased risk of QTc prolongation and torsades de pointe because of pharmacodynamic DDIs with medication for comorbidities. Close monitoring of electrocardiograms for NH residents with COPD is recommended.

Molecular dynamics simulations suggest possible activation and deactivation pathways in the hERG channel

The elusive activation/deactivation mechanism of hERG is investigated, a voltage-gated potassium channel involved in severe inherited and drug-induced cardiac channelopathies, including the Long QT Syndrome. Firstly, the available structural data are integrated by providing a homology model for the closed state of the channel. Secondly, molecular dynamics combined with a network analysis revealed two distinct pathways coupling the voltage sensor domain with the pore domain. Interestingly, some LQTS-related mutations known to impair the activation/deactivation mechanism are distributed along the identified pathways, which thus suggests a microscopic interpretation of their role. Split channels simulations clarify a surprising feature of this channel, which is still able to gate when a cut is introduced between the voltage sensor domain and the neighboring helix S5. In summary, the presented results suggest possible activation/deactivation mechanisms of non-domain-swapped potassium channels that may aid in biomedical applications.

Costa et al. present the electro-mechanical coupling between the voltage sensor and pore domain of the hERG channel using a combination of molecular dynamics simulations and theoretical network analyses.

Cardiovascular Safety Assessment in Cancer Drug Development

The development of cardiovascular toxicity attributable to anticancer drugs is a pivotal event that is associated with cardiovascular morbidity as well as with worse cancer-specific and overall outcomes. Although broad consensus exists regarding the importance of cardiovascular safety assessment in cancer drug development, real-world data suggest that cardiovascular events are significantly underestimated in oncology trials. This drug safety discrepancy has profound implications on drug development decisions, risk-benefit evaluation, formulation of surveillance and prevention protocols, and survivorship. In this article, we review the contemporary cardiovascular safety evaluation of new pharmaceuticals in hematology and oncology, spanning from in vitro pharmacodynamic testing to randomized clinical trials. We argue that cardiovascular safety assessment of anticancer drugs should be reformed and propose practical strategies, including development and validation of preclinical assays, expansion of oncology trial eligibility, incorporation of cardiovascular end points in early-phase studies, and design of longitudinal multi-institutional cardiotoxicity registries.

Fluconazole-associated QT interval prolongation and Torsades de Pointes in a paediatric patient

"Torsades de pointes", a life-threatening rhythm disorder, is a polymorphic ventricular tachycardia that usually develops in association with a prolonged QT interval. Fluconazole, an anti-fungal drug, may also induce QT prolongation, in some cases subsequent torsades de pointes. Herein, we report a 16-year-old female presenting "torsades de pointes" after administration of fluconazole and rapidly improved upon cessation of the drug.

Improving corrected QT; Why individual correction is not enough

The use of QT-prolongation as a biomarker for arrhythmia risk requires that researchers correct the QT-interval (QT) to control for the influence of heart rate (HR). QT correction methods can vary but most used are the universal correction methods, such as Bazett's or Van de Water's, which use a single correction formula to correct QT-intervals in all the subjects of a study. Such methods fail to account for differences in the QT/HR relationship between subjects or over time, instead relying on the assumption that this relationship is consistent. To address these changes in rate relationships, we test the effectiveness of linear and non-linear individual correction methods. We hypothesize that individual correction methods that account for additional influences on the rate relationship will result in more effective and consistent correction. To increase the scope of this study we use bootstrap sampling on ECG recordings from non-human primates and beagle canines dosed with vehicle control. We then compare linear and non-linear individual correction methods through their ability to reduce HR correlation and standard deviation of corrected QT values. From these results, we conclude that individual correction methods based on post-treatment data are most effective with the linear methods being the best option for most cases in both primates and canines. We also conclude that the non-linear methods are more effective in canines than primates and that accounting for light status can improve correction while examining the data from the light periods separately. Individual correction requires careful consideration of inter-subject and intra-subject variabilities.

Development and validation of a tool to assess the risk of QT drug-drug interactions in clinical practice

BACKGROUND

The exact risk of developing QTc-prolongation when using a combination of QTc-prolonging drugs is still unknown, making it difficult to interpret these QT drug-drug interactions (QT-DDIs). A tool to identify high-risk patients is needed to support healthcare providers in handling automatically generated alerts in clinical practice. The main aim of this study was to develop and validate a tool to assess the risk of QT-DDIs in clinical practice.

METHODS

A model was developed based on risk factors associated with QTc-prolongation determined in a prospective study on QT-DDIs in a university medical center inthe Netherlands. The main outcome measure was QTc-prolongation defined as a QTc interval > 450 ms for males and > 470 ms for females. Risk points were assigned to risk factors based on their odds ratios. Additional risk factors were added based on a literature review. The ability of the model to predict QTc-prolongation was validated in an independent dataset obtained from a general teaching hospital against QTc-prolongation as measured by an ECG as the gold standard. Sensitivities, specificities, false omission rates, accuracy and Youden's index were calculated.

RESULTS

The model included age, gender, cardiac comorbidities, hypertension, diabetes mellitus, renal function, potassium levels, loop diuretics, and QTc-prolonging drugs as risk factors. Application of the model to the independent dataset resulted in an area under the ROC-curve of 0.54 (95% CI 0.51-0.56) when QTc-prolongation was defined as > 450/470 ms, and 0.59 (0.54-0.63) when QTc-prolongation was defined as > 500 ms. A cut-off value of 6 led to a sensitivity of 76.6 and 83.9% and a specificity of 28.5 and 27.5% respectively.

CONCLUSIONS

A clinical decision support tool with fair performance characteristics was developed. Optimization of this tool may aid in assessing the risk associated with QT-DDIs.

TRIAL REGISTRATION

No trial registration, MEC-2015-368.

Dominant rule of community effect in synchronized beating behavior of cardiomyocyte networks

Exploiting the combination of latest microfabrication technologies and single cell measurement technologies, we can measure the interactions of single cells, and cell networks from "algebraic" and "geometric" perspectives under the full control of their environments and interactions. However, the experimental constructive single cell-based approach still remains the limitations regarding the quality and condition control of those cells. To overcome these limitations, mathematical modeling is one of the most powerful complementary approaches. In this review, we first explain our on-chip experimental methods for constructive approach, and we introduce the results of the "community effect" of beating cardiomyocyte networks as an example of this approach. On-chip analysis revealed that (1) synchronized interbeat intervals (IBIs) of cell networks were followed to the more stable beating cells even their IBIs were slower than the other cells, which is against the conventional faster firing regulation or "overdrive suppression," and (2) fluctuation of IBIs of cardiomyocyte networks decreased according to the increase of the number of connected cells regardless of their geometry. The mathematical simulation of this synchronous behavior of cardiomyocyte networks also fitted well with the experimental results after incorporating the fluctuation-dissipation theorem into the oscillating stochastic phase model, in which the concept of spatially arranged cardiomyocyte networks was involved. The constructive experiments and mathematical modeling indicated the dominant rule of synchronization behavior of beating cardiomyocyte networks is a kind of stability-oriented synchronization phenomenon as the "community effect" or a fluctuation-dissipation phenomenon. Finally, as a practical application of this approach, the predictive cardiotoxicity is introduced.

Influence of estrous stages on electrocardiography, clinical pathology and ovarian weight of experimental beagle dogs: a retrospective analysis

Estrous cycle is a repetitive phenomenon occurring during the reproductive life of a female dog. The duration of the canine estrous cycle is considerably longer than one in the most of the other animals and is broadly grouped into follicular phase (proestrus and estrus), luteal phase (diestrus) and non-seasonal anestrus. Dogs in the same stage of cycle can be inadvertently assigned to same group during routine safety and metabolic studies leading to possible erroneous interpretation of test-item related effects. This retrospective analysis was conducted by analyzing data of 86 female beagle dogs from control/placebo treated groups to correlate any possible effect of estrous stages with electrocardiography, clinical pathology and ovarian weight. Different estrous cycle stages of beagles were confirmed histologically by evaluating ovary, uterus, vagina and mammary glands. The incidence of beagles in diestrus was the highest, followed by anestrus, proestrus and estrus. No significant effect was noticed on heart rate, P–A, P–D, RR, QRS and QT intervals across different stages of estrous cycle. However, significantly higher PQ (PR) interval in dogs in proestrus stage was observed compared to dogs in anestrus and estrus. Marginally higher WBCs, neutrophils, lymphocytes, RBCs, hemoglobin, AST and lower hematocrit, lipid profile (total cholesterol, HDL, LDL, triglycerides), ALP level was evident in estrous period. Relative ovary weight was significantly higher in dogs in diestrus stage. Considering these results, one may need to exercise caution while interpreting experimental data from female beagle dogs.

Three-Dimensional Heart Model-Based Screening of Proarrhythmic Potential by in silico Simulation of Action Potential and Electrocardiograms

The proarrhythmic risk is a major concern in drug development. The Comprehensive in vitro Proarrhythmia Assay (CiPA) initiative has proposed the JTpeak interval on electrocardiograms (ECGs) and qNet, an in silico metric, as new biomarkers that may overcome the limitations of the hERG assay and QT interval. In this study, we simulated body-surface ECGs from patch-clamp data using realistic models of the ventricles and torso to explore their suitability as new in silico biomarkers for cardiac safety. We tested seven drugs in this study: dofetilide (high proarrhythmic risk), ranolazine, verapamil (QT increasing, but safe), bepridil, cisapride, mexiletine, and diltiazem. Human ventricular geometry was reconstructed from computed tomography (CT) images, and a Purkinje fiber network was mapped onto the endocardial surface. The electrical wave propagation in the ventricles was obtained by solving a reaction-diffusion equation using finite-element methods. The body-surface ECG data were calculated using a torso model that included the ventricles. The effects of the drugs were incorporated in the model by partly blocking the appropriate ion channels. The effects of the drugs on single-cell action potential (AP) were examined first, and three-dimensional (3D) body-surface ECG simulations were performed at free Cmax values of 1×, 5×, and 10×. In the single-cell and ECG simulations at 5× Cmax, dofetilide, but not verapamil or ranolazine, caused arrhythmia. However, the non-increasing JTpeak caused by verapamil and ranolazine that has been observed in humans was not reproduced in our simulation. Our results demonstrate the potential of 3D body-surface ECG simulation as a biomarker for evaluation of the proarrhythmic risk of candidate drugs.

Prevalence of Torsades de Pointes inducing drugs usage among elderly outpatients in North Jordan Hospitals

•

Demonstrating the urgent need for increasing awareness of TdP's risk induced by chronically used medications.

•

The importance of establishing an extensive pharmaceutical care for geriatric population with the aim of improving health outcomes and quality of life in elderly patients.

•

To identify the major risk factors associated with increasing the incidence of TdP’s among geriatric patients in Jordan.

Background

Torsade de Pointes (TdP) is an abnormal cardiac rhythm associated with a prolongation of QT interval. Although in most cases it spontaneously returns to the normal rhythm, TdP can lead to sudden cardiac death. Medications are the main cause of QT-prolongation and subsequent TdP flare, even though the exact mechanism of why some people evoke TdP but others do not is still unknown. It is evident that elderly patients are more susceptible to experience drug's side effects especially with chronically used medications.

Objectives

To describe the pattern of prescribing drugs with risk of Torsade’s de Pointes among elderly patients who were visiting different outpatient clinics in North Jordan Hospitals.

Methods

All patients who were aged ≥65 years old and were visiting outpatient clinics in King Abdullah University Hospital (KAUH) and Princess Basma Hospital (PBH) through December 2016 were included in the study. A total of 5319 patients’ dispending records were collected and analyzed for the prevalence of drug-induced TdP using both Microsoft Excel and the SPSS statistical software.

Results

A total of 5319 patients were included in the study, more than half (58.5%, n = 3114) of patients were consuming drugs with risk of TdP. Almost half (49.4%, n = 1539) of these patients were women. The majority of patients (62.3%, n = 1939) were using only one drug with TdP risk. However, other patients were found to take five or six different TdP-inducing drugs. Excluding age and gender, 94.3% (n = 2937) of patients who were using TdP-inducing drugs had at least one additional risk factor of inducing TdP.

Conclusion

High usage of TdP-inducing drugs among geriatric patients in North Jordan demonstrated the urgent need for increasing awareness of TdP’s risk induced by commonly prescribed medications.

On-chip spatiotemporal electrophysiological analysis of human stem cell derived cardiomyocytes enables quantitative assessment of proarrhythmia in drug development

We examined a simultaneous combined spatiotemporal field potential duration (FPD) and cell-to-cell conduction time (CT) in lined-up shaped human embryonic stem cell-derived cardiomyocytes (hESC-CMs) using an on-chip multielectrode array (MEA) system to evaluate two origins of lethal arrhythmia, repolarization and depolarization. The repolarization index, FPD, was prolonged by E-4031 and astemizole, and shortened by verapamil, flecainide and terfenadine at 10 times higher than therapeutic plasma concentrations of each drug, but it did not change after lidocaine treatment up to 100 μM. CT was increased by astemizol, flecainide, terfenadine, and lidocaine at equivalent concentrations of Nav1.5 IC50, suggesting that CT may be an index of cardiac depolarization because the increase in CT (i.e., decrease in cell-to-cell conduction speed) was relevant to Nav1.5 inhibition. Fluctuations (short-term variability; STV) of FPD and CT, STVFPD and STVCT also discriminated between torsadogenic and non-torsadogenic compounds with significant increases in their fluctuation values, enabling precise prediction of arrhythmogenic risk as potential new indices.

Experimentally Validated Pharmacoinformatics Approach to Predict hERG Inhibition Potential of New Chemical Entities

The hERG (human ether-a-go-go-related gene) encoded potassium ion (K⁺) channel plays a major role in cardiac repolarization. Drug-induced blockade of hERG has been a major cause of potentially lethal ventricular tachycardia termed Torsades de Pointes (TdPs). Therefore, we presented a pharmacoinformatics strategy using combined ligand and structure based models for the prediction of hERG inhibition potential (IC₅₀) of new chemical entities (NCEs) during early stages of drug design and development. Integrated GRid-INdependent Descriptor (GRIND) models, and lipophilic efficiency (LipE), ligand efficiency (LE) guided template selection for the structure based pharmacophore models have been used for virtual screening and subsequent hERG activity (pIC₅₀) prediction of identified hits. Finally selected two hits were experimentally evaluated for hERG inhibition potential (pIC₅₀) using whole cell patch clamp assay. Overall, our results demonstrate a difference of less than ±1.6 log unit between experimentally determined and predicted hERG inhibition potential (IC₅₀) of the selected hits. This revealed predictive ability and robustness of our models and could help in correctly rank the potency order (lower μM to higher nM range) against hERG.

Molecular determinants of Kv7.1/KCNE1 channel inhibition by amitriptyline

Amitriptyline (AMIT) is a compound widely prescribed for psychiatric and non-psychiatric conditions including depression, migraine, chronic pain, and anorexia. However, AMIT has been associated with risks of cardiac arrhythmia and sudden death since it can induce prolongation of the QT interval on the surface electrocardiogram and torsade de pointes ventricular arrhythmia. These complications have been attributed to the inhibition of the rapid delayed rectifier potassium current (I_Kr). The slow delayed rectifier potassium current (I_Ks) is the main repolarizing cardiac current when I_Kr is compromised and it has an important role in cardiac repolarization at fast heart rates induced by an elevated sympathetic tone. Therefore, we sought to characterize the effects of AMIT on Kv7.1/KCNE1 and homomeric Kv7.1 channels expressed in HEK-293H cells. Homomeric Kv7.1 and Kv7.1/KCNE1 channels were inhibited by AMIT in a concentration-dependent manner with IC50 values of 8.8 ± 2.1 μM and 2.5 ± 0.8 μM, respectively. This effect was voltage-independent for both homomeric Kv7.1 and Kv7.1/KCNE1 channels. Moreover, mutation of residues located on the P-loop and S6 domain along with molecular docking, suggest that T312, I337 and F340 are the most important molecular determinants for AMIT-Kv7.1 channel interaction. Our experimental findings and modeling suggest that AMIT preferentially blocks the open state of Kv7.1/KCNE1 channels by interacting with specific residues that were previously reported to be important for binding of other compounds, such as chromanol 293B and the benzodiazepine L7.

QTc prolongation during ciprofloxacin and fluconazole combination therapy: prevalence and associated risk factors

AIM(S)

Ciprofloxacin and fluconazole combination therapy is frequently used as prophylaxis for, and treatment of, infections in patients with haematological malignancies. However, both drugs are known to prolong the heart rate-corrected QT (QTc) interval, which is a serious risk factor for torsade de pointes (TdP). Therefore, the aim of the current study was to assess the prevalence of QTc prolongation during ciprofloxacin and fluconazole use. The secondary objective was to determine associated risk factors of QTc prolongation in these patients.

METHODS

A prospective observational study was performed in patients admitted to the Erasmus University Medical Centre and treated with ciprofloxacin and fluconazole. A 12-lead electrocardiogram (ECG) was recorded at the estimated time to peak concentration (T_max ) for the last added drug. The main outcome was the proportion of patients with QTc prolongation during treatment. Data on the following potential risk factors were collected: patient characteristics, serum electrolyte levels, dosage of ciprofloxacin and fluconazole, renal and liver function and concomitant use of other QTc-prolonging drugs and cytochrome P450 3A4 inhibitors.

RESULTS

A total of 170 patients were included, of whom 149 (87.6%) were treated for haematological malignancies. The prevalence of QTc prolongation was 4.7%. No risk factors were found to be associated with QTc prolongation. The QTc interval increased by 10.7 ms [95% confidence interval (CI) 7.2, 14.1 ms] during ciprofloxacin and fluconazole combination therapy.

CONCLUSION

The prevalence of QTc prolongation in patients using ciprofloxacin and fluconazole is low compared with the prevalence in the general population, which varies from 5% to 11%. In addition, no risk factors were found. Given the low prevalence, routine ECG monitoring in patients on this therapy should be reconsidered.

Frequency-Dependent Multi-Well Cardiotoxicity Screening Enabled by Optogenetic Stimulation

Side effects on cardiac ion channels causing lethal arrhythmias are one major reason for drug withdrawals from the market. Field potential (FP) recording from cardiomyocytes, is a well-suited tool to assess such cardiotoxic effects of drug candidates in preclinical drug development, but it is currently limited to the spontaneous beating of the cardiomyocytes and manual analysis. Herein, we present a novel optogenetic cardiotoxicity screening system suited for the parallel automated frequency-dependent analysis of drug effects on FP recorded from human-induced pluripotent stem cell-derived cardiomyocytes. For the expression of the light-sensitive cation channel Channelrhodopsin-2, we optimised protocols using virus transduction or transient mRNA transfection. Optical stimulation was performed with a new light-emitting diode lid for a 96-well FP recording system. This enabled reliable pacing at physiologically relevant heart rates and robust recording of FP. Thereby we detected rate-dependent effects of drugs on Na⁺, Ca2+ and K⁺ channel function indicated by FP prolongation, FP shortening and the slowing of the FP downstroke component, as well as generation of afterdepolarisations. Taken together, we present a scalable approach for preclinical frequency-dependent screening of drug effects on cardiac electrophysiology. Importantly, we show that the recording and analysis can be fully automated and the technology is readily available using commercial products.

Drug Safety Analysis in a Real-Life Cohort of Parkinson's Disease Patients with Polypharmacy

BACKGROUND

Polypharmacy is common in geriatric Parkinson's disease (PD) patients in advanced disease stages with multiple comorbidities, bearing multiple risks for drug safety in theory.

OBJECTIVE

The aim of this study was to empirically identify the most frequent and relevant contraindications and drug interactions actually occurring and compromising drug safety in PD in real life.

METHODS

We conducted a prospective observational study in a multimorbid cohort of PD patients with polypharmacy admitted to a specialized hospital. Inclusion criteria were the presence of at least one comorbidity requiring pharmacotherapy and at least five different drugs in the discharge prescription. Hoehn and Yahr stage during the 'on' state, therapeutic problems related to motor and non-motor PD symptoms, comorbidities, and drug regimens on admission and discharge were analyzed for contraindications and interactions.

RESULTS

Overall, 127 patients were included (medium Hoehn and Yahr stage = IV, range II-V). Interactions with the anti-PD medication were mainly caused by other central nervous system (CNS)-active substances, cytochrome P450-metabolized substances, and QT-time prolonging substances. Contraindications against the anti-PD medication mainly occurred from internal, haematopoietic, neurologic and psychiatric diseases, and QT-time prolonging drugs. The highest frequency of interactions and contraindications were identified with levodopa (n = 119 at admission/n = 126 at discharge), entacapone (n = 46/42), pramipexole (n = 44/24), and amantadine (n = 32/30).

CONCLUSIONS

Several medically relevant risk factors (interactions and contraindications) frequently occurred in advanced PD patients. These findings provide a basis for developing programmes for awareness, education, monitoring, and preventive interventions to avoid adverse incidents. Future studies will need to evaluate preventive efficacy of structured drug safety programmes.

hiPSC-CM Monolayer Maturation State Determines Drug Responsiveness in High Throughput Pro-Arrhythmia Screen

Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) offer a novel in vitro platform for pre-clinical cardiotoxicity and pro-arrhythmia screening of drugs in development. To date hiPSC-CMs used for cardiotoxicity testing display an immature, fetal-like cardiomyocyte structural and electrophysiological phenotype which has called into question the applicability of hiPSC-CM findings to the adult heart. The aim of the current work was to determine the effect of cardiomyocyte maturation state on hiPSC-CM drug responsiveness. To this end, here we developed a high content pro-arrhythmia screening platform consisting of either fetal-like or mature hiPSC-CM monolayers. Compounds tested in the screen were selected based on the pro-arrhythmia risk classification (Low risk, Intermediate risk, or High risk) established recently by the FDA and major stakeholders in the Drug Discovery field for the validation of the Comprehensive In vitro Pro-Arrhythmia Assay (CiPA). Here we show that maturation state of hiPSC-CMs determines the absolute pro-arrhythmia risk score calculated for these compounds. Thus, the maturation state of hiPSC-CMs should be considered prior to pro-arrhythmia and cardiotoxicity screening in drug discovery programs.

Antidepressants and the risk of arrhythmia in elderly affected by a previous cardiovascular disease: a real-life investigation from Italy

PURPOSE

The study aimed to fill existing knowledge gaps on the safety of antidepressant drugs (ADs) by estimating the risk of hospitalization for arrhythmia associated with use of selective serotonin reuptake inhibitors (SSRIs) and newer atypical ADs (NAAs) among elderly with previous cardiovascular (CV) events.

METHODS

The cohort was composed by 199,569 individuals aged ≥ 65 years from five Italian healthcare territorial units who were discharged for cardiovascular outcomes in the years 2008-2010. The 17,277 patients who experienced hospital admission for arrhythmia during follow-up were included as cases. Odds of current ADs use among cases (i.e., 14 days before hospital admission) was compared with (i) odds of current use of 1:5 matched controls (between-patients case-control) and with (ii) odds of previous use during 1:5 matched control periods (within-patient case-crossover). The risk of arrhythmia associated with ADs current use was modelled fitting a conditional logistic regression. A set of sensitivity analyses was performed to account for sources of systematic uncertainty.

RESULTS

Current users of SSRIs and NAAs were at increased risk of arrhythmia with case-control odds ratios (OR) of 1.37 (95% confidence interval, CI 1.18 to 1.58) and 1.41 (1.16 to 1.71) and case-crossover OR of 1.48 (1.20 to 1.81) and 1.72 (1.31 to 2.27). An increased risk of arrhythmia was associated with current use of trazodone (NAA) consistently in case-control and case-crossover designs.

CONCLUSIONS

Evidence that current use of SSRIs and NAAs is associated to an increased risk of arrhythmia among elderly with CV disease was consistently supplied by two observational approaches.

Drugs and life-threatening ventricular arrhythmia risk: results from the DARE study cohort

OBJECTIVES

To establish a unique sample of proarrhythmia cases, determine the characteristics of cases and estimate the contribution of individual drugs to the incidence of proarrhythmia within these cases.

SETTING

Suspected proarrhythmia cases were referred by cardiologists across England between 2003 and 2011. Information on demography, symptoms, prior medical and drug histories and data from hospital notes were collected.

PARTICIPANTS

Two expert cardiologists reviewed data for 293 referred cases: 130 were included. Inclusion criteria were new onset or exacerbation of pre-existing ventricular arrhythmias, QTc >500 ms, QTc >450 ms (men) or >470 ms (women) with cardiac syncope, all secondary to drug administration. Exclusion criteria were acute ischaemia and ischaemic polymorphic ventricular tachycardia at presentation, structural heart disease, consent withdrawn or deceased prior to study. Descriptive analysis of Caucasian cases (95% of included cases, n=124) and culpable drug exposures was performed.

RESULTS

Of the 124 Caucasian cases, 95 (77%) were QTc interval prolongation-related; mean age was 62 years (SD 15), and 63% were female. Cardiovascular comorbidities included hypertension (53%) and patient-reported 'heart rhythm problems' (73%). Family history of sudden death (36%) and hypokalaemia at presentation (27%) were common. 165 culpable drug exposures were reported, including antiarrhythmics (42%), of which amiodarone and flecainide were the most common. Sotalol, a beta-blocking agent with antiarrhythmic activity, was also common (15%). 26% reported multiple drugs, of which 84% reported at least one cytochrome (CYP) P450 inhibitor. Potential pharmacodynamics interactions identified were mainly QT prolongation (59%).

CONCLUSIONS

Antiarrhythmics, non-cardiac drugs and drug combinations were found to be culpable in a large cohort of 124 clinically validated proarrhythmia cases. Potential clinical factors that may warn the prescriber of potential proarrhythmia include older women, underlying cardiovascular comorbidity, family history of sudden death and hypokalaemia.

Drug–drug interaction related to the use of pipamperon and ondansetron in a child treated for leukemia

Pipamperon is a potent neuroleptic drug with many side effects, including prolongation of the QT interval. We report a case of a child treated for leukemia in which prolongation of the QT interval was observed. Physicians and pharmacists should be cautious for drug–drug interactions when pipamperon is prescribed, especially in combination with other QT-prolongating agents. Alternative strategies should be used whenever possible.

Prediction of hERG Liability - Using SVM Classification, Bootstrapping and Jackknifing

Drug-induced QT prolongation leads to life-threatening cardiotoxicity, mostly through blockage of the human ether-à-go-go-related gene (hERG) encoded potassium ion (K+ ) channels. The hERG channel is one of the most important antitargets to be addressed in the early stage of drug discovery process, in order to avoid more costly failures in the development phase. Using a thallium flux assay, 4,323 molecules were screened for hERG channel inhibition in a quantitative high throughput screening (qHTS) format. Here, we present support vector classification (SVC) models of hERG channel inhibition with the averaged area under the receiver operator characteristics curve (AUC-ROC) of 0.93 for the tested compounds. Both Jackknifing and bootstrapping have been employed to rebalance the heavily biased training datasets, and the impact of these two under-sampling rebalance methods on the performance of the predictive models is discussed. Our results indicated that the rebalancing techniques did not enhance the predictive power of the resulting models; instead, adoption of optimal cutoffs could restore the desirable balance of sensitivity and specificity of the binary classifiers. In an external validation set of 66 drug molecules, the SVC model exhibited an AUC-ROC of 0.86, further demonstrating the utility of this modeling approach to predict hERG liabilities.

Drug-Induced QTc Prolongation

QTc prolongation has a high prevalence of and is associated with increased all-cause mortality. Nonetheless, QTc prolonging medications are often used during patient hospitalizations despite baseline prolongation and QTc changes. Data regarding the real-world relative risk of QTc prolongation in the hospital setting are lacking. In this study, we sought to quantify the degree and relative risk of QTc prolongation in patients receiving Arizona Center for Education and Research on Therapeutics (AzCERT) "known risk" medications. Electronic medical records of patients receiving an electrocardiogram at the University of Chicago, admitted in 2011 were analyzed. The longest QTc interval and medications administered within the preceding 24 hours were evaluated. Medications were classified into 4 categories according to the AzCERT classification. Of a total of 14,804 patients, mean QTc intervals were 485 versus 454 ms for men and 469 versus 453 ms for women receiving known risk medications compared with those receiving no risk medications (p <0.001). The rate of QTc prolongation was 71% versus 48% for men and 50% versus 34% for women, respectively. There was no significant increase in QTc prolongation for patients administered multiple QT-relevant medications or for those administered only conditional or possible risk medications. In conclusion, the prevalence of significant QTc prolongation in patients receiving AzCERT known risk medications is high. This may be a reflection of inadequate awareness or overall quality inadequacies.

A Micropatterned Human Pluripotent Stem Cell-Based Ventricular Cardiac Anisotropic Sheet for Visualizing Drug-Induced Arrhythmogenicity

A novel cardiomimetic biohybrid material, termed as the human ventricular cardiac anisotropic sheet (hvCAS) is reported. Well-characterized human pluripotent stem-cell-derived ventricular cardiomyocytes are strategically aligned to reproduce key electrophysiological features of native human ventricle, which, along with specific selection criteria, allows for a direct visualization of arrhythmic spiral re-entry and represents a revolutionary tool to assess preclinical drug-induced arrhythmogenicity.

The Use of Ratiometric Fluorescence Measurements of the Voltage Sensitive Dye Di-4-ANEPPS to Examine Action Potential Characteristics and Drug Effects on Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) and higher throughput platforms have emerged as potential tools to advance cardiac drug safety screening. This study evaluated the use of high bandwidth photometry applied to voltage-sensitive fluorescent dyes (VSDs) to assess drug-induced changes in action potential characteristics of spontaneously active hiPSC-CM. Human iPSC-CM from 2 commercial sources (Cor.4U and iCell Cardiomyocytes) were stained with the VSD di-4-ANEPPS and placed in a specialized photometry system that simultaneously monitors 2 wavebands of emitted fluorescence, allowing ratiometric measurement of membrane voltage. Signals were acquired at 10 kHz and analyzed using custom software. Action potential duration (APD) values were normally distributed in cardiomyocytes (CMC) from both sources though the mean and variance differed significantly (APD90: 229 ± 15 ms vs 427 ± 49 ms [mean ± SD, P < 0.01]; average spontaneous cycle length: 0.99 ± 0.02 s vs 1.47 ± 0.35 s [mean ± SD, P < 0.01], Cor.4U vs iCell CMC, respectively). The 10-90% rise time of the AP (Trise) was ∼6 ms and was normally distributed when expressed as 1/[Formula: see text] in both cell preparations. Both cell types showed a rate dependence analogous to that of adult human cardiac cells. Furthermore, nifedipine, ranolazine, and E4031 had similar effects on cardiomyocyte electrophysiology in both cell types. However, ranolazine and E4031 induced early after depolarization-like events and high intrinsic firing rates at lower concentrations in iCell CMC. These data show that VSDs provide a minimally invasive, quantitative, and accurate method to assess hiPSC-CM electrophysiology and detect subtle drug-induced effects for drug safety screening while highlighting a need to standardize experimental protocols across preparations.

Provider Response to QTc Prolongation on Standard 12-Lead EKG: Do We Notice or Do We Care?

BACKGROUND

Drugs and electrolyte imbalances are widely recognized as common triggers of a prolonged QT interval. We conducted a chart review to assess provider response to prolonged QT reported on a standard 12-lead electrocardiogram (EKG).

METHODS

We identified all Veterans Affairs Pittsburgh Healthcare System patients in a 6-month period with an EKG reporting a corrected QT (QTc) >500 ms. We excluded confounding or uninterpretable EKGs. Charts were reviewed to assess medications and electrolytes at the time of the EKG as well as the setting (inpatient vs outpatient) in which the EKG was obtained. Provider documentation of QTc and any corrective measures were sought.

RESULTS

After exclusions, 106 patients were included in this analysis (87 [82%] inpatient and 19 [18%] outpatient). Most were male (101, 95%) with a mean age of 63.5 ± 10.6 years. At the time of index EKG, most patients were receiving at least one (72, 68%), and frequently two or more (35, 33%), QTc prolonging medications. Providers documented QTc prolongation in 20 inpatients (19%). Drugs were adjusted or discontinued in only two inpatients (2%). There were 14 patients (14%) with potassium level <3.6 mmol/L and 10 of 69 (14%) patients had a magnesium level <1.7 mg/dL.

CONCLUSION

Patients with prolonged QTc on EKG were more likely to be inpatients than outpatients. Inpatients were more likely to be receiving multiple types and classes of QTc prolonging medications. In the vast majority of cases, providers did not address the prolonged QTc and only rarely initiated remedial actions.

An antiarrhythmic agent as a promising lead compound for targeting the hEAG1 ion channel in cancer therapy: insights from molecular dynamics simulations

Experimental evidence suggests that hERG and hEAG potassium channels may serve as important cancer therapy targets because either of the channel blockade or inactivation by different methods leads to inhibition of cancer cells growth and proliferation. However, there is no known hEAG specific blocker, and hERG blockade leads to adverse cardiac side effects, although it is currently used in treating certain types of arrhythmias. There have been some attempts to explain the channels blockade by clofilium, an antiarrhythmic agent, and the results lead to different possible binding modes. This study investigates for the first time the potential of using clofilium as a lead compound for finding a novel cancer therapy agent which may target ion channels. The implied findings from a comparative assessment of literature studies were verified using molecular dynamics simulations. The results indicate a particular structural difference between the two channels that could provide a novel and realistic way of using clofilium analogs which may target the hEAG1 ion channel in cancer therapy.

Differential Inhibition of Inducible T Cell Cytokine Secretion by Potent Iron Chelators

Effector functions and proliferation of T helper (Th) cells are influenced by cytokines in the environment. Th1 cells respond to a synergistic effect of interleukin-12 (IL-12) and interleukin-18 (IL-18) to secrete interferon-gamma (IFN-γ). In contrast, Th2 cells respond to interleukin-4 (IL-4) to secrete IL-4, interleukin-13 (IL-13), interleukin-5 (IL-5), and interleukin-10 (IL-10). The authors were interested in identifying nonpeptide inhibitors of the Th1 response selective for the IL-12/IL-18-mediated secretion of IFN-γ while leaving the IL-4-mediated Th2 cytokine secretion relatively intact. The authors established a screening protocol using human peripheral blood mononuclear cells (PBMCs) and identified the hydrazino anthranilate compound 1 as a potent inhibitor of IL-12/IL-18-mediated IFN-γ secretion from CD3+ cells with an IC50 around 200 nM. The inhibitor was specific because it had virtually no effect on IL-4-mediated IL-13 release from the same population of cells. Further work established that compound 1 was a potent intracellular iron chelator that inhibited both IL-12/IL-18- and IL-4-mediated T cell proliferation. Iron chelation affects multiple cellular pathways in T cells. Thus, the IL-12/IL-18-mediated proliferation and IFN-γ secretion are very sensitive to intracellular iron concentration. However, the IL-4-mediated IL-13 secretion does not correlate with proliferation and is partially resistant to potent iron chelation

High prevalence of risk factors in elderly patients using drugs associated with acquired torsades de pointes chronically in Colombia

AIMS

Medication is one of the main causes of long QT syndrome (LQTS) and torsades de pointes (TdP), and the older adult population is at particularly high risk. The aim of the present study was to describe the prescription patterns of drugs with a risk of TdP in the Colombian older adult population.

METHODS

Patients older than 65 years who received medication with a risk of TdP during three consecutive months were selected. The medication was obtained and classified according to the QT Drug List from Crediblemeds.org. The data were analysed using SPSS-22.

RESULTS

A total of 55 932 patients were chronically receiving QT-prolonging drugs; 61.9% (n = 34 ,632) were women and the mean age of the sample was 75.6 years. Drugs with a conditional risk were consumed by 95.2% of patients, 5.3% received drugs with a known risk and 2.9% received drugs with a possible risk. Two or more QT-prolonging drugs were consumed by 10.3% of the patients (n = 5786). Most of the sample (96.8%, n = 54 170) had at least one additional risk factor for LQTS, with a mean of 3.1 ± 0.9 risk factors. Patients receiving QT-prolonging drugs for psychiatric and neurological disease were at a higher risk of major polypharmacy [odds ratio (OR) 3.0; 95% confidence interval (CI) 2.80, 3.22) and of receiving high doses of QT-prolonging drugs (OR 3.8; 95% CI 3.52, 4.05).

CONCLUSIONS

The widespread use of medication that causes TdP and the high prevalence of additional risks in the older adult population raise the need for accurate prediction of risk and constant patient monitoring. Patients taking psychiatric drugs are at a higher risk of TdP.

Long QT Syndrome Leading to Multiple Cardiac Arrests After Posaconazole Administration in an Immune-Compromised Patient with Sepsis: An Unusual Case Report

BACKGROUND

We present the case of a septic patient with severe immunodeficiency, who developed QT interval prolongation followed by episodes of lethal cardiac arrhythmia. Cardiac events occurred after posaconazole administration, incriminating posaconazole use, alone or in combination with voriconazole, as the culpable agent.

CASE REPORT

A 26-year-old female patient underwent orthopedic surgery to remove ectopic calcifications in her left hip joint. On the first post-operative day she became septic due to a surgical wound infection. Despite being treated according to the therapeutic protocols for sepsis, no clinical improvement was noticed and further assessment revealed an underlying immunodeficiency. Considering the underlying immunodeficiency and to that point poor clinical response, an antifungal agent was added to the antibiotic regiment. Following discontinuation of multiple antifungal agents due to adverse effects, posaconazole was administered. Posaconazole oral intake was followed by episodes of bradycardia and QT interval prolongation. The patient suffered continuous incidents of cardiac arrest due to polymorphic ventricular tachycardia (torsades des pointes) that degenerated to lethal ventricular fibrillation. Posaconazole was immediately discontinued and a temporary pacemaker was installed. The patient finally recovered without any neurological deficit, and was discharged in a good clinical status.

CONCLUSIONS

Close cardiac monitoring is recommended in cases where posaconazole administration is combined with coexisting risk factors, as they may lead to severe ECG abnormalities and cardiac arrhythmias such as long QT interval syndrome and torsades de pointes. Posaconazole interactions with medications metabolized via the CYP3A4 pathway should be considered an additional risk factor for lethal cardiac incidents.

Pharmacological, Pharmacokinetic, and Pharmacogenomic Aspects of Functional Gastrointestinal Disorders

This article reviews medications commonly used for the treatment of patients with functional gastrointestinal disorders. Specifically, we review the animal models that have been validated for the study of drug effects on sensation and motility; the preclinical pharmacology, pharmacokinetics, and toxicology usually required for introduction of new drugs; the biomarkers that are validated for studies of sensation and motility endpoints with experimental medications in humans; the pharmacogenomics applied to these medications and their relevance to the FGIDs; and the pharmacology of agents that are applied or have potential for the treatment of FGIDs, including psychopharmacologic drugs.

Electrocardiogram pattern of some exotic breeds of trained dogs: A variation study

Aim:

The present study has been conducted to evaluate the variation in electrocardiogram (ECG) parameters among different trained breeds of dogs (viz. Labrador, German Shepherd, and Golden Retriever) used for security reasons.

Materials and Methods:

The ECG was recorded by single channel ECG at a paper speed of 25 mm/s and calibration of 10 mm=1 mV. The recordings were taken from all the standard bipolar limb leads (Lead-I, II, and III) and unipolar augmented limb leads (Lead-aVR, aVL, and aVF).

Results:

Heart rate was found to be highest in Labrador and lowest in German Shepherd. P-wave duration was maximum in Golden Retriever breed and lowest in Labrador. Maximum amplitude of P-wave was found in Labrador followed by German Shepherd and Golden Retriever. There was significantly (p<0.05) higher values of PR interval in German Shepherd compared to other breeds. The variation in QRS duration, ST segment duration, T-wave duration, and T-wave amplitude was found to be non-significant among breeds. Inverted T-waves were most common in Golden Retriever and German Shepherd, whereas positive T-waves were found in Labrador. There was significant (p<0.05) variation in mean electrical axis of QRS complex among different breeds and it ranges from +60° to +80°.

Conclusion:

The present study provides the reference values for different ECG parameters to monitor the cardiac health status among Labrador, German Shepherd, and Golden Retriever breeds.

Managing arrhythmias in the intensive care unit

Patients admitted to the intensive care unit (ICU) are at increased risk for cardiac arrhythmias, the most common of which can be subdivided into tachyarrhythmias and bradyarrhythmias. These arrhythmias may be the primary reason for ICU admission or may occur in the critically ill patient. This article addresses the occurrence of arrhythmias in the critically ill patient, and discusses their pathophysiology, implications, recognition, and management.

Learning from the past and looking to the future: Emerging perspectives for improving the treatment of psychiatric disorders

Modern neuropsychopharmacology commenced in the 1950s with the serendipitous discovery of first-generation antipsychotics and antidepressants which were therapeutically effective yet had marked adverse effects. Today, a broader palette of safer and better-tolerated agents is available for helping people that suffer from schizophrenia, depression and other psychiatric disorders, while complementary approaches like psychotherapy also have important roles to play in their treatment, both alone and in association with medication. Nonetheless, despite considerable efforts, current management is still only partially effective, and highly-prevalent psychiatric disorders of the brain continue to represent a huge personal and socio-economic burden. The lack of success in discovering more effective pharmacotherapy has contributed, together with many other factors, to a relative disengagement by pharmaceutical firms from neuropsychiatry. Nonetheless, interest remains high, and partnerships are proliferating with academic centres which are increasingly integrating drug discovery and translational research into their traditional activities. This is, then, a time of transition and an opportune moment to thoroughly survey the field. Accordingly, the present paper, first, chronicles the discovery and development of psychotropic agents, focusing in particular on their mechanisms of action and therapeutic utility, and how problems faced were eventually overcome. Second, it discusses the lessons learned from past successes and failures, and how they are being applied to promote future progress. Third, it comprehensively surveys emerging strategies that are (1), improving our understanding of the diagnosis and classification of psychiatric disorders; (2), deepening knowledge of their underlying risk factors and pathophysiological substrates; (3), refining cellular and animal models for discovery and validation of novel therapeutic agents; (4), improving the design and outcome of clinical trials; (5), moving towards reliable biomarkers of patient subpopulations and medication efficacy and (6), promoting collaborative approaches to innovation by uniting key partners from the regulators, industry and academia to patients. Notwithstanding the challenges ahead, the many changes and ideas articulated herein provide new hope and something of a framework for progress towards the improved prevention and relief of psychiatric and other CNS disorders, an urgent mission for our Century.

Short-term variability in QT interval and ventricular arrhythmias induced by dofetilide are dependent on high-frequency autonomic oscillations

Background and Purpose

The present study was undertaken to investigate an effect of dofetilide, a potent arrhythmic blocker of the voltage-gated K⁺ channel, hERG, on cardiac autonomic control. Combined with effects on ardiomyocytes, these properties could influence its arrhythmic potency.

Experimental Approach

The short-term variability of beat-to-beat QT interval (STV_QT), induced by dofetilide is a strong surrogate of Torsades de pointes liability. Involvement of autonomic modulation in STV_QT was investigated in healthy cynomolgus monkeys and beagle dogs by power spectral analysis under conditions of autonomic blockade with hexamethonium.

Key Results

Increase in STV_QT induced by dofetilide in monkeys and dogs was closely associated with an enhancement of endogenous heart rate and QT interval high-frequency (HF) oscillations. These effects were fully suppressed under conditions of autonomic blockade with hexamethonium. Ventricular arrhythmias, including Torsades de pointes in monkeys, were prevented in both species when HF oscillations were suppressed by autonomic blockade. Similar enhancements of heart rate HF oscillations were found in dogs with other hERG blockers described as causing Torsades de pointes in humans.

Conclusions and Implications

These results demonstrate for the first time that beat-to-beat ventricular repolarization variability and ventricular arrhythmias induced by dofetilide are dependent on endogenous HF autonomic oscillations in heart rate. When combined with evidence of hERG-blocking properties, enhancement of endogenous HF oscillations in heart rate could constitute an earlier and more sensitive biomarker than STV_QT for Torsades de pointes liability, applicable to preclinical regulatory studies conducted in healthy animals.

[Drug-induced QT interval prolongation: do we know the risks?]

Sudden cardiac death is an important cause of mortality in developed countries, most of them being consequence of acute ventricular arrhythmias. These arrhythmias, in some cases, owe to QT interval prolongation. A major risk factor for this condition is the use of drugs that prolong the QT interval. In fact, in recent years, one of the most common reasons for drug withdrawal or usage restrictions has been drug induced QT interval prolongation that involves both cardiovascular and non-cardiovascular drugs. Taking into account the severity that the occurrence of such an event may have, it is important for clinicians to know the risks of these drugs in certain patients. In this review we analyze the drugs that prolong the QT interval, the risk factors that can enhance QT prolongation and the drug interactions that can increase these risks.

Ventricular dysrhythmias associated with poisoning and drug overdose: a 10-year review of statewide poison control center data from California

BACKGROUND

Ventricular dysrhythmias are a serious consequence associated with drug overdose and chemical poisoning. The risk factors for the type of ventricular dysrhythmia and the outcomes by drug class are not well documented.

OBJECTIVE

The aim of this study was to determine the most common drugs and chemicals associated with ventricular dysrhythmias and their outcomes.

METHODS

We reviewed all human exposures reported to a statewide poison control system between 2002 and 2011 that had a documented ventricular dysrhythmia. Cases were differentiated into two groups by type of arrhythmia: (1) ventricular fibrillation and/or tachycardia (VT/VF); and (2) torsade de pointes (TdP).

RESULTS

Among the 300 potential cases identified, 148 cases met the inclusion criteria. Of these, 132 cases (89%) experienced an episode of VT or VF, while the remaining 16 cases (11%) had an episode of TdP. The most commonly involved therapeutic classes of drugs associated with VT/VF were antidepressants (33/132, 25%), stimulants (33/132, 25%), and diphenhydramine (16/132, 12.1%). Those associated with TdP were antidepressants (4/16, 25%), methadone (4/16, 25%), and antiarrhythmics (3/16, 18.75%). Drug exposures with the greatest risk of death in association with VT/VF were antidepressant exposure [odds ratio (OR) 1.71; 95% confidence interval (CI) 0.705-4.181] and antiarrhythmic exposure (OR 1.75; 95% CI 0.304-10.05), but neither association was statistically significant. Drug exposures with a statistically significant risk for TdP included methadone and antiarrhythmic drugs.

CONCLUSIONS

Antidepressants and stimulants were the most common drugs associated with ventricular dysrhythmias. Patients with suspected poisonings by medications with a high risk of ventricular dysrhythmia warrant prompt ECG monitoring.