A case with a trend of QT interval prolongation due to the introduction of methadone to a pancreatic cancer patient on levofloxacin

BACKGROUND

As methadone can prevent the development of opioid resistance, it has application in alleviating cancer-related pain that proves challenging to manage with other opioids. QT interval prolongation is a serious side effect of methadone treatment, with some reported deaths. In particular, owing to the increased risk of QT interval prolongation, caution should be exercised when using it in combination with drugs that also prolong the QT interval.

CASE PRESENTATION

This study presents a case in which methadone was introduced to a patient (a man in his 60s) already using levofloxacin, which could prolong the QT interval-a serious side effect of methadone treatment-and whose QTc value tended to increase. Given that levofloxacin can increase the risk of QT interval prolongation, we considered switching to other antibacterial agents before introducing methadone. However, because the neurosurgeon judged that controlling a brain abscess was a priority, low-dose methadone was introduced with continuing levofloxacin. Owing to the risks, we performed frequent electrocardiograms. Consequently, we responded before the QTc increased enough to meet the diagnostic criteria for QT interval prolongation. Consequently, we prevented the occurrence of drug-induced long QT syndrome.

CONCLUSIONS

When considering the use of methadone for intractable cancer pain, it is important to eliminate possible risk factors for QT interval prolongation. However, as it may be difficult to discontinue concomitant drugs owing to comorbidities, there could be cases in which the risk of QT interval prolongation could increase, even with the introduction of low-dose methadone. In such cases, frequent monitoring, even with simple measurements such as those used in this case, is likely to prevent progression to more serious conditions.

Relacorilant, a Selective Glucocorticoid Receptor Modulator in Development for the Treatment of Patients With Cushing Syndrome, Does Not Cause Prolongation of the Cardiac QT Interval

OBJECTIVE

To assess the effect of relacorilant, a selective glucocorticoid receptor modulator under investigation for the treatment of patients with endogenous hypercortisolism (Cushing syndrome [CS]), on the heart rate-corrected QT interval (QTc).

METHODS

Three clinical studies of relacorilant were included: (1) a first-in-human, randomized, placebo-controlled, ascending-dose (up to 500 mg of relacorilant) study in healthy volunteers; (2) a phase 1 placebo- and positive-controlled thorough QTc (TQT) study of 400 and 800 mg of relacorilant in healthy volunteers; and (3) a phase 2, open-label study of up to 400 mg of relacorilant administered daily for up to 16 weeks in patients with CS. Electrocardiogram recordings were taken, and QTc change from baseline (ΔQTc) was calculated. The association of plasma relacorilant concentration with the effect on QTc in healthy volunteers was assessed using linear mixed-effects modeling.

RESULTS

Across all studies, no notable changes in the electrocardiogram parameters were observed. At all time points and with all doses of relacorilant, including supratherapeutic doses, ΔQTc was small, generally negative, and, in the placebo-controlled studies, similar to placebo. In the TQT study, placebo-corrected ΔQTc with relacorilant was small and negative, whereas placebo-corrected ΔQTc with moxifloxacin positive control showed rapid QTc prolongation. These results constituted a negative TQT study. The model-estimated slopes of the concentration-QTc relationship were slightly negative, excluding an association of relacorilant with prolonged QTc.

CONCLUSION

At all doses studied, relacorilant consistently demonstrated a lack of QTc prolongation in healthy volunteers and patients with CS, including in the TQT study. Ongoing phase 3 studies will help further establish the overall benefit-risk profile of relacorilant.

Serial electrocardiogram recordings revealed a high prevalence of QT interval prolongation in patients with tuberculosis receiving fluoroquinolones

BACKGROUND

Fluoroquinolones, crucial components of treatment regimens for drug-resistant tuberculosis (TB), are associated with QT interval prolongation and risks of fatal cardiac arrhythmias. However, few studies have explored dynamic changes in the QT interval in patients receiving QT-prolonging agents.

METHODS

This prospective cohort study recruited hospitalized patients with TB who received fluoroquinolones. The study investigated the variability of the QT interval by using serial electrocardiograms (ECGs) recorded four times daily. This study analyzed the accuracy of intermittent and single-lead ECG monitoring in detecting QT interval prolongation.

RESULTS

This study included 32 patients. The mean age was 68.6 ± 13.2 years. The results revealed mild-to-moderate and severe QT interval prolongation in 13 (41%) and 5 (16%) patients, respectively. The incremental yields in sensitivity of one to four daily ECG recordings were 61.0%, 26.1%, 5.6%, and 7.3% in detecting mild-to-moderate QT interval prolongation, and 66.7%, 20.0%, 6.7%, and 6.7% in detecting severe QT interval prolongation. The sensitivity levels of lead II and V5 ECGs in detecting mild-to-moderate and severe QT interval prolongation exceeded 80%, and their specificity levels exceeded 95%.

CONCLUSION

This study revealed a high prevalence of QT interval prolongation in older patients with TB who receive fluoroquinolones, particularly those with multiple cardiovascular risk factors. Sparsely intermittent ECG monitoring, the prevailing strategy in active drug safety monitoring programs, is inadequate owing to multifactorial and circadian QT interval variability. Additional studies performing serial ECG monitoring are warranted to enhance the understanding of dynamic QT interval changes in patients receiving QT-prolonging anti-TB agents.

Linezolid and the risk of QT interval prolongation: A pharmacovigilance study of the Food and Drug Administration Adverse Event Reporting System

AIMS

Few studies have investigated linezolid (LZD)-associated cardiotoxicity. This study explored the potential association between LZD and QT interval prolongation.

METHODS

Adverse event reports of QT interval prolongation associated with LZD from the Food and Drug Administration Adverse Event Reporting System from January 2013 to December 2021 were analysed and the reporting odds ratio (ROR) with 95% confidence intervals were calculated.

RESULTS

A total of 6738 adverse event reports of LZD as the primary and secondary suspected drug were obtained from the database, including 192 reports with electrocardiogram QT prolonged (QTp), and the ROR value was 26.1 (95% CI = 22.6-30.2). There were 8 reports of long QT syndrome, ROR 14.2 (95% CI = 7.1-28.5); 5 reports of torsade de pointes, ROR 3.2 (95% CI = 1.3-7.6); and 5 reports of ventricular tachycardia, ROR 1.9 (95% CI = 0.8-4.5). Subgroup analysis revealed that patients with tuberculosis treated with LZD had a higher reporting rate among all QTp reports, exhibiting an odds ratio of 330.0 (95% CI = 223.1-488.1). The odds ratios of QTp associated with LZD treatments in patients with and without tuberculosis were 4.2 (95% CI = 3.4-5.3) and 1.2 (95% CI = 0.8-1.6), respectively.

CONCLUSION

The study showed an association between LZD and QT interval prolongation. In the report on patients with tuberculosis, the incidence of QTp was higher when treated with LZD.

Enzastaurin cardiotoxicity: QT interval prolongation, negative inotropic responses and negative chronotropic action

Several clinical trials observed that enzastaurin prolonged QT interval in cancer patients. However, the mechanism of enzastaurin-induced QT interval prolongation is unclear. Therefore, this study aimed to assess the effect and mechanism of enzastaurin on QT interval and cardiac function. The Langendorff and Ion-Optix MyoCam systems were used to assess the effects of enzastaurin on QT interval, cardiac systolic function and intracellular Ca²⁺ transient in guinea pig hearts and ventricular myocytes. The effects of enzastaurin on the rapid delayed rectifier (I_Kr), the slow delayed rectifier K⁺ current (I_Ks), transient outward potassium current (I_to), action potentials, Ryanodine Receptor 2 (RyR2) and the sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2a (SERCA2a) expression and activity in HEK 293 cell system and primary cardiomyocytes were investigated using whole-cell recording technique and western blotting. We found that enzastaurin significantly prolonged QT interval in guinea pig hearts and increased the action potential duration (APD) in guinea pig cardiomyocytes in a dose-dependent manner. Enzastaurin potently inhibited I_Kr by binding to the human Ether-à-go-go-Related gene (hERG) channel in both open and closed states, and hERG mutant channels, including S636A, S631A, and F656V attenuated the inhibitory effect of enzastaurin. Enzastaurin also moderately decreased I_Ks. Additionally, enzastaurin also induced negative chronotropic action. Moreover, enzastaurin impaired cardiac systolic function and reduced intracellular Ca²⁺ transient via inhibition of RyR2 phosphorylation. Taken together, we found that enzastaurin prolongs QT, reduces heart rate and impairs cardiac systolic function. Therefore, we recommend that electrocardiogram (ECG) and cardiac function should be continuously monitored when enzastaurin is administered to cancer patients.

Electrocardiogram of a patient with mushroom poisoning-induced myocarditis

A patient presented to our hospital with myocarditis caused by mushroom poisoning. The early ECG changes in this patient were very similar to the ECG of hyperacute ST-segment elevation myocardial infarction or hyperkalemia, but further tests eliminated these options. The patient was fully treated by timely hemodialysis treatment, confirming the diagnosis of mushroom poisoning-induced myocarditis. Although not specific to mushroom poisoning myocarditis, our experience shows that the observed ECG changes. Our findings have the potential to help diagnose and manage this potentially fatal disease in the future.

The Association of Proton Pump Inhibitors and QT Interval Prolongation in Critically Ill Patients

INTRODUCTION

Drug-induced QT interval prolongation has been reported to be related to life-threatening polymorphic ventricular tachycardia (torsade de pointes). Proton pump inhibitors (PPIs) are prescribed widely for hospitalized patients; the QT interval prolongation and torsade de pointes caused by PPIs were reported. We conducted a study to determine the association between PPI treatment and QT interval prolongation in critically ill patients.

METHODS

This study included patients with electrocardiography (ECG) reports from the Medical Information Mart for Intensive Care III database (MIMIC-III). Patients younger than 18 years, missing baseline laboratories and with QT interval prolongation before intensive care unit (ICU) admission were excluded. The end point was the diagnosis of QT interval prolongation reported by ECG.

RESULTS

This study included 24,512 ICU patients. Of them, 11,327 patients were treated with PPIs, 4181 with histamine 2 receptor antagonists (H2RAs) and 6351 without acid suppression therapy (non-AST); the incidence of QT interval prolongation were 8.5%, 3.3% and 3.4% respectively. After adjustment for demographics, electrolytes, comorbidities and medications, PPIs were associated a higher risk of QT interval prolongation compared with H2RAs (OR 1.66, 95% CI 1.36 - 2.03) and non-AST (OR 1.54, 95% CI 1.31 - 1.82), while there was not significant difference between H2RAs and non-AST (OR 0.93, 95% CI 0.73 - 1.17). In the propensity score matching population, the results were consistent. Pantoprazole (OR 2.14, 95% CI 1.52 - 3.03) and lansoprazole (OR 1.80, 95% CI: 1.18 - 2.76) showed a higher QT prolongation risk than omeprazole. Several drugs caused higher QT prolongation risk when used in combination with PPIs.

CONCLUSION

In ICU patients, the association between PPI prescription and increased risk of QT interval prolongation was independent of known QT-prolonging factors; pantoprazole and lansoprazole had a higher risk compared with omeprazole. The combination of PPIs and other QT-prolonging drugs should be avoided.

Possible convulsion and electroencephalographic abnormality in a patient taking long-term oral clarithromycin: A case report

BACKGROUND

Clarithromycin is a macrolide antibiotic commonly prescribed to patients with upper respiratory and otolaryngological infections. Neuropsychiatric adverse effects of clarithromycin include agitation, insomnia, delirium, psychosis, and seizure.

CASE SUMMARY

A 52-year-old man was admitted to our hospital with a convulsion. He had > 10-year history of clarithromycin intake for chronic sinusitis. One week before admission, he started to take diltiazem for angina pectoris. On admission, his convulsion subsided. His electroencephalography showed frontal intermittent rhythmic delta activity. One week after he ceased clarithromycin, his electroencephalographic abnormalities disappeared. We suggested that the patient developed convulsions due to increased blood levels of clarithromycin caused by oral administration of diltiazem, which is involved in CYP3A metabolism.

CONCLUSION

Clarithromycin has a relatively high safety profile and is a frequently prescribed drug. However, there are a few previous reports of clarithromycin-related convulsive disorders. Clinicians should be aware of the drug interaction and rare side effects of seizures.

Development and Validation of a Nomogram for Prediction of QT Interval Prolongation in Patients Administered Bedaquiline-Containing Regimens in China: a Modeling Study

Corrected QT duration (QTc) interval prolongation is the most frequent adverse event associated with bedaquiline (BDQ) use. It may affect the safety of antituberculosis therapy, which leads to the consequent demands of needing to monitor during therapy. Our objective was to establish and validate a prediction model for estimating the risk of QTc prolongation after initiation of BDQ-containing regimens to multidrug-resistant tuberculosis (MDR-TB) patients. We constructed an individualized nomogram model based on baseline demographic and clinical characteristics of each patient within a Chinese cohort during BDQ treatment. The generalizability of this model was further validated through use of externally acquired data obtained from Beijing Chest Hospital from 2019 to 2020. Overall, 1,215 and 165 patients were included in training and external validation cohorts, respectively, whereby during anti-TB drug treatment, QTc prolongation was observed in 273 (22.5%) and 29 (17.6%) patients within these respective cohorts, for whom QTc values were >500 ms in 86 (31.5%) and 10 (34.7%) patients, respectively. Next, a total of four Cox proportional hazards models were created and assessed; then, nomograms derived from the models were plotted based on independent predictors of clofazimine, baseline QTc interval, creatinine, extensive drug-resistance (XDR), moxifloxacin, levofloxacin, and sex. Nomogram analysis revealed concordance index values of 0.723 (95% confidence interval [CI], 0.695 to 0.750) for the training cohort and 0.710 (95% CI, 0.627 to 0.821) for the external validation cohort, thus indicating relatively fair agreement between predicted and observed probabilities of QTc prolongation occurrence based on data obtained during 8-week, 16-week, and 24-week anti-TB treatment of both cohorts. Taken together, results obtained using these models demonstrated that coadministration of clofazimine and abnormal baseline QTc interval significantly contributed to QTc prolongation development during MDR-TB patient treatment with a BDQ-containing anti-TB treatment regimen.

Bedaquiline Effect on QT Interval of Drugs-Resistant Tuberculosis Patients: Real World Data

BACKGROUND

Bedaquiline (BDQ) is effective as part of treatment regimen for drug-resistant tuberculosis (DR-TB), but the cardiac safety profile of BDQ is not fully elucidated. This study aimed to analyse the cardiac safety of BDQ by examining its effect on the QT interval of DR-TB patients.

METHODS

This is a retrospective study cohort conducted in two DR-TB referral hospitals in Indonesia. The QT interval before and after therapy using BDQ was measured manually and corrected using the Fridericia formula (QTcF). The QT interval profile was analysed over time during BDQ treatment.

RESULTS

A total of 105 subjects participated in the study. The maximum mean difference (standard deviation) of QTcF after treatment with the baseline (∆QTcF) is 34,06 (52,92) ms after three months of therapy. During BDQ treatment, clinically significant QTcF prolongations was observed in 37.1% subjects with neither arrhythmia nor any other adverse cardiac event occurred. The interval QT prolongation led to BDQ discontinuation in 15.2% subjects temporarily and in 6.7% subjects permanently. There were seven deaths (6.7%) during the treatment.

CONCLUSION

During BDQ treatment, maximum QT prolongation was observed after three months of BDQ therapy. Therefore, more intensive cardiac monitoring is recommended during this period and afterwards.

QT Interval Prolongation in People Treated With Bedaquiline for Drug-Resistant Tuberculosis Under Programmatic Conditions: A Retrospective Cohort Study

BACKGROUND

Bedaquiline has a black-box warning of the risk of arrhythmias and sudden death. This study aimed to determine the incidence of QTc prolongation and cardiac events in patients receiving bedaquiline for drug-resistant tuberculosis (DR-TB) under programmatic conditions.

METHODS

Retrospective cohort study of patients receiving bedaquiline at a DR-TB hospital in KwaZulu Natal, South Africa from September 2017 to February 2019. The primary outcome, a prolonged QT interval corrected using the Fridericia formula (QTcF), was defined as QTcF >500 ms, QTcF change >60 ms from baseline, or both.

RESULTS

Among 420 patients (66.2% male, median age 36 years), the median QTcF was 406.4 (interquartile range [IQR], 389.1-421.3) ms at baseline, increasing to 430.5 (IQR, 414.4-445.1) ms by 3 months and 434.0 (IQR, 419.0-447.9) ms at 6 months. Eighteen of 420 patients (4.3%) had a QTcF >500 ms and 110 of 420 patients (26.2%) had a QTcF change >60 ms. There were no recorded arrhythmias or cardiac deaths. Odds of prolonged QTcF were increased with concomitant azoles (adjusted odds ratio [aOR], 5.61 [95% confidence interval (CI), 2.26-13.91]; P < .001) and an inverse association with HIV-positive status (aOR, 0.34 [95% CI, .15-.75]; P = .008) and hypertension (aOR, 0.13 [95% CI, .02-.86]; P = .02). After prolongation, the QTcF declined to <500 ms, whether drugs were interrupted or not.

CONCLUSIONS

We observed a modest prolongation of QTcF, maximal at week 15; there were no recorded arrhythmias or related deaths.

QT interval prolongation and the risk of malignant ventricular dysrhythmia and/or cardiac arrest: Systematic search and narrative review of risk related to the magnitude of QT interval length

Prolongation of the QTc interval is associated with an increased risk of malignant ventricular dysrhythmias, such as ventricular tachycardia (VT), and sudden cardiac death. The quantifiable risk rates of adverse dysrhythmic outcome in relation to specific QTc interval length are not known. We conducted a literature review on the topic of QT interval prolongation in adult patients and the associated risk of malignant dysrhythmic event. We specifically formulated our literature search and subsequent literature review to address the following question: Can the clinician identify specific QTc intervals at which a specific quantifiable risk of malignant dysrhythmic event (malignant ventricular dysrhythmia and/or cardiac arrest) occurs in an undifferentiated adult patient population? In the literature search, we identified 701 studies; upon review using specific, pre-determined inclusion criteria, we identified 16 articles for inclusion in the review. From this literature, we were unable to answer the question in a quantifiable manner and only noted that the risk of malignant dysrhythmic event increases with progressively longer QTc interval. The current literature on this topic is inadequate to answer this important question due to heterogenous study methodology, patient populations, endpoints, and periods of observation. Additional prospective research is required on this topic, aimed at addressing the important issue of specific, quantifiable risk and its relation to degree of prolongation of the QTc interval.

Predicting QT interval prolongation in patients diagnosed with the 2019 novel coronavirus infection

INTRODUCTION

2019 novel coronavirus (COVID-19) patients frequently develop QT interval prolongation that predisposes them to Torsades de Pointes and sudden cardiac death. Continuous cardiac monitoring has been recommended for any COVID-19 patient with a Tisdale Score of seven or more. This recommendation, however, has not been validated.

METHODS

We included 178 COVID-19 patients admitted to a non-intensive care unit setting of a tertiary academic medical center. A receiver operating characteristics curve was plotted to determine the accuracy of the Tisdale Score to predict QT interval prolongation. Multivariable analysis was performed to identify additional predictors.

RESULTS

The area under the curve of the Tisdale Score was 0.60 (CI 95%, 0.46-0.75). Using the cutoff of seven to stratify COVID-19, patients had a sensitivity of 85.7% and a specificity of 7.6%. Risk factors independently associated with QT interval prolongation included a history of end-stage renal disease (ESRD) (OR, 6.42; CI 95%, 1.28-32.13), QTc ≥450 ms on admission (OR, 5.90; CI 95%, 1.62-21.50), and serum potassium ≤3.5 mmol/L during hospitalization (OR, 4.97; CI 95%, 1.51-16.36).

CONCLUSION

The Tisdale Score is not a useful tool to stratify hospitalized non-critical COVID-19 patients based on their risks of developing QT interval prolongation. Clinicians should initiate continuous cardiac monitoring for patients who present with a history of ESRD, QTc ≥450 ms on admission or serum potassium ≤3.5 mmol/L.

Accuracy of a single-lead mobile smartphone electrocardiogram for QT interval measurement in patients undergoing maintenance methadone therapy

STUDY OBJECTIVE

Methadone is associated with QT interval prolongation and torsades de pointes. Expert panel recommendations advocate a pre-methadone electrocardiogram (ECG) and another ECG at 30 days of therapy in patients with risk factors. Some guidelines recommend a pre-methadone ECG and routine ECG monitoring in all methadone patients, but this is controversial due to the resources required. Availability of a convenient, less resource-intensive method of ECG monitoring for patients taking methadone is desirable. The objective of this study was to assess the accuracy of a handheld smartphone ECG (iECG) for QT measurement in patients on maintenance methadone therapy in an urban opioid treatment program.

DESIGN

Prospective study.

SETTING

Urban opioid treatment program.

PATIENTS

n = 115 patients in normal sinus rhythm who were on steady-state maintenance methadone therapy INTERVENTION: Patients (n = 115) underwent a simultaneous 12-lead ECG and a single-lead iECG.

MEASUREMENTS AND MAIN RESULTS

The first three QT and RR intervals from lead II of the 12-lead ECG and simulated lead I from the iECG were compared using the Bland-Altman analysis of measurement agreement. Mean [± standard deviation) age was 34 ± 11 years; 71% were female, 75% were white. Compared to the 12-lead ECG, the iECG was associated with a QTc bias of - 0.14 ms (SD = 12 ms, 95% CI = -2.4 to 2.1 ms). The absolute mean difference in QTc between the two methods was 9.5 ± 7.1 ms. For identification of patients with methadone-associated QTc prolongation, the iECG performed moderately well [c-statistic 0.97 (95% CI 0.91-0.99); sensitivity and specificity 75% (95% CI 43-95%) and 99% (95% CI 94-99%), respectively]. The positive and negative likelihood ratios of the iECG for identifying patients with methadone-associated QTc prolongation were 77.25 (95% CI 10.69 to 558.18) and 0.25 (95% CI 0.09 to 0.67), respectively, while the positive and negative predictive values were 90% (95% CI 56-99%) and 97% (95% CI 92-99%), respectively. The accuracy of the iECG for identifying patients with QTc prolongation was 97% (95% CI 91-99%).

CONCLUSION

A handheld smartphone ECG is accurate for QT interval measurement in patients taking maintenance methadone therapy, and its performance is moderately good for identifying patients with methadone-associated QTc prolongation.

Congenital long QT syndrome: Should citric fruits be avoided? A case report of a cLQTS type 1 with unusual QTc prolongation with citric juices

Congenital long QT syndromes (cLQTS) are relatively rare diseases in which QT interval is prolonged due to several mutations on ion channels involved in cardiac cell repolarization. This condition confers higher risk of malignant arrhythmias and sudden cardiac death, and it is widely accepted that substances that prolong QT interval should be avoided by these patients. Most of these substances are antibiotics and non-antibiotics drugs, but almost nothing is known about frequently consumed fruits and juices. We report the case of a patient with a previously asymptomatic cLQTS type 1 (cLQTS1) with unusual QT prolongation of 167 milliseconds (ms) related to the consumption of large amounts of citric juices (oranges and lemons). A literature review was done for better understanding of its influence on QT interval duration and to know the concentration of flavonoids on citric fruits. <Learning objective: The objective is to emphasize the relatively new concept of "proarrhythmic food". A short number of clinical trials have demonstrated a modest QT interval prolongation with grapefruit juice, but nothing has been previously described of other citric fruits. We present a case of a patient with cLQTS1 that suffered severe QT interval prolongation related to orange and lemon juice consumption. Substances on these fruits involved in QT prolongation and pathophysiological mechanism are discussed.>.

Relationship between antofloxacin concentration and QT prolongation and estimation of the possible false-positive rate

PURPOSE

To elucidate the relationship between antofloxacin (AT) plasma concentration and QT interval prolongation, compare the effects of different correction and analytical methods on conclusions, and estimate the possible false-positive rate in thorough QT (TQT) studies.

METHODS

Twenty-four healthy Chinese volunteers from a four-period crossover TQT study orally received 200 mg/d AT, 400 mg/d AT, 400 mg/d moxifloxacin, and a placebo in a random order for 5 d for each. QT interval samples were collected on d 1 and d 5. Population models were established describing the relationship between QT and AT concentration. The yardstick from ICH E14 guidelines was used to measure the effect of drugs on QT prolongation both in biostatistical and modeling analyses. A possible false-positive rate was estimated by constructing a 1000-time bootstrap to obtain the rate-of-difference values between d 1 and d 5 over 5 ms in the placebo period.

RESULTS

In the modeling analysis, the QT prolongation estimate at the mean maximal concentration of AT (4.51 μg/mL) was 3.84 ms, and its upper bound of the one-sided 95 % CI was 7.04 ms, which showed a negative effect on QT interval prolongation. The estimation for the false-positive rate was 31 % in this study.

CONCLUSION

The effect of AT on QT interval prolongation may not have been significant at the dosage of 400 mg. Baseline and placebo adjustments were necessary in TQT studies. Population modeling has demonstrated clear superiority in making full use of data to accurately analyze the relationship between drugs and QT intervals.

Prevalence of QTc interval prolongation and its associated risk factors among psychiatric patients: a prospective observational study

BACKGROUND

QT interval prolongation is a growing concern worldwide, posing psychiatric patients to life-threatening fatal arrhythmias i.e., torsade de pointes. This study aimed to identify the prevalence of QT interval prolongation, its associated risk factors and prescribing patterns of QT prolonging drugs among psychiatric patients.

METHOD

A prospective observational study was conducted that included psychiatric patients from a tertiary care hospital and a psychiatry clinic in Peshawar, Khyber Pakhtunkhwa, Pakistan. Electrocardiogram was recorded of those patients who were using psychotropic medications for ≥7 days, aged 18 years or more, and of either gender, male or female. The Fredericia correction formula was used for measuring QTc values (corrected QT). Chi-square test was applied to estimate differences between patients with or without prolonged QTc interval whereas, logistic regression analysis was performed to identify various predictors of QT interval prolongation.

RESULTS

Out of 405 patients, the QTc interval was prolonged in 23 (5.7%) patients including 1 (0.2%) patient with highly abnormal prolonged QTc interval (> 500 ms). QT drugs (91.6%), female sex (38.7%) and hypertension (10.6%) were the most common QT prolonging risk factors. Prolonged QTc interval was significantly higher among male patients (p = 0.007).

CONCLUSION

In the present study, QT interval prolongation was observed in a considerable number of psychiatric patients. While, the high prevalence of QT prolonging risk factors among these patients warrants the increased risk of fatal arrhythmias. Therefore, risk assessment and electrocardiographic monitoring, and prescription of safer alternatives are highly recommended.

The relationship between atypical antipsychotics drugs, QT interval prolongation, and torsades de pointes: implications for clinical use

Introduction: Increased mortality has been observed in patients with mental health disorders. Specifically, exposure to antipsychotic medications conveys a greater than 2 fold risk of sudden death, thought to be mediated through effects on QT prolongation and risk of torsades de pointes.Areas covered: We review the association between antipsychotic drugs and sudden cardiac death, the physiologic basis for these associations, assessment of patients at risk, and strategies to minimize risk of sudden cardiac death.Expert opinion: Despite the prevalence of antipsychotic medication use for many decades, there remain considerable challenges in reducing the associated risk of sudden cardiac death. A structured algorithm that incorporates patient clinical factors and antipsychotic drug factors may improve risk assessment and reduce the risk of adverse cardiac events. Future advancements in genetics and artificial intelligence may allow for enhanced risk stratification and predicting response (efficacy and adverse effects) to therapy.

A Thorough QT Study to Evaluate the Effects of a Supratherapeutic Dose of Sertraline on Cardiac Repolarization in Healthy Subjects

The effect of steady-state supratherapeutic sertraline (Zoloft) on QT interval was assessed in a single-center, randomized, 3-way crossover, double-blind, placebo- and moxifloxacin-controlled thorough QT study. Healthy adults received sertraline 400 mg/day, moxifloxacin 400 mg, and placebo, with a washout period (≥14 days) between treatments. A 12-lead electrocardiogram was recorded in triplicate before dosing and at selected time points up to 72 hours after dosing. Analysis of covariance using a mixed-effect model with sequence, period, treatment, time, and treatment-by-time interaction as fixed effects; subject within sequence as a random effect; and baseline QT corrected for heart rate using Fridericia formula (QTcF) as a covariate was conducted. A 90% confidence interval for the least squares (LS) mean difference in QTcF between active treatment and placebo was computed for each postdose time point. Exposure-response was assessed using linear mixed-effect modeling. Fifty-four subjects were enrolled. Over 24 hours after dosing, the LS mean difference in QTcF for sertraline versus placebo ranged from 5.597 milliseconds to 9.651 milliseconds. The upper bound of the 90% confidence interval for the LS mean difference exceeded a predefined 10-millisecond significance threshold at the 4-hour postdose time point only (LS mean, 9.651 milliseconds [90% confidence interval, 7.635-11.666]). In the exposure-response analysis, QTcF values increased significantly with increasing sertraline concentration (slope = 0.036 milliseconds/ng/mL; P < .0001). Predicted change from baseline in QTcF at therapeutic maximum plasma sertraline concentration was 3.57 milliseconds. This thorough QTc study demonstrated a positive signal for QTc prolongation for sertraline at the steady-state 400-mg/day dose.

Identification of Risk of QT Prolongation by Pharmacists When Conducting Medication Reviews in Residential Aged Care Settings: A Missed Opportunity?

QT interval prolongation is associated with torsade de pointes and sudden cardiac death. QT prolongation can be caused by many drugs that are commonly prescribed in elderly residential aged care populations. The aim of this study was to investigate the prevalence of use of QT-prolonging drugs and to identify interventions made by pharmacists to reduce the risk of QT prolongation when conducting medication reviews in aged care. A retrospective analysis of 400 medication reviews undertaken by Australian pharmacists in aged care settings was conducted. The assessment included the risk of QT prolongation due to prescribed medications and other risk factors and the recommendations made by pharmacists to reduce the risk of QT prolongation. There was a high prevalence of the use of QT-prolonging medication, with 23% of residents (92 out of 400) taking at least one medication with a known risk of QT prolongation. Amongst the 945 prescribed drugs with any risk of QT prolongation, antipsychotics were the most common (n = 246, 26%), followed by antidepressants (19%) and proton pump inhibitors (13%). There appeared to be low awareness amongst the pharmacists regarding the risk of QT prolongation with drugs. Out of 400 reviews, 66 residents were categorised as high risk and were taking at least one medication associated with QT prolongation; yet pharmacists intervened in only six instances (9%), mostly when two QT-prolonging medications were prescribed. There is a need to increase awareness amongst pharmacists conducting medication reviews regarding the risk factors associated with QT prolongation, and further education is generally needed in this area.

Exposure-response analysis of drug-induced QT interval prolongation in telemetered monkeys for translational prediction to human

INTRODUCTION

The preclinical in vivo assay for QT prolongation is critical for predicting torsadogenic risk, but still difficult to extrapolate to humans. This study ran preclinical tests in cynomolgus monkeys on seven QT reference drugs containing the drugs used in the IQ-CSRC clinical trial and applied exposure-response (ER) analysis to the data to investigate the potential for translational information on the QT effect.

METHODS

In each of six participating facilities in the J-ICET project, telemetered monkeys were monitored for 24 h following administration of vehicle or 3 doses of test drugs, and pharmacokinetic profiles at the same doses were evaluated separately. An individual rate-corrected QT interval (QTca) was derived and the vehicle-adjusted change in QTca from baseline (∆∆QTca) was calculated. Then the relationship of concentration to QT effect was evaluated by ER analysis.

RESULTS

For QT-positive drugs in the IQ-CSRC study (dofetilide, dolasetron, moxifloxacin, ondansetron, and quinine) and levofloxacin, the slope of the total concentration-QTca effect was significantly positive, and the QT-prolonging effect, taken as the upper bound of the confidence interval for predicted ∆∆QTca, was confirmed to exceed 10 ms. The ER slope of the negative drug levocetirizine was not significantly positive and the QTca effect was below 10 ms at observed peak exposure.

DISCUSSION

Preclinical QT assessment in cynomolgus monkeys combined with ER analysis could identify the small QT effect induced by several QT drugs consistently with the outcomes in humans. Thus, the ER method should be regarded as useful for translational prediction of QT effects in humans.

Repolarization abnormalities in carbon monoxide poisoning - a case report

Each year a notable number of fatal intoxications with carbon monoxide (CO) is reported worldwide. Carbon monoxide binds with hemoglobin, decreases oxygen supply and leads to hypoxia and lactic acidosis. Myocardium, being particularly vulnerable to hypoxia, is one of the most damaged organs in course of CO intoxication.

A CASE REPORT

We present a case report of severe CO poisoning in a 66-year old man, that led to significant repolarization abnormalities. Diffuse ST segment depression associated with significant QT interval prolongation up to QTcB 595ms was observed in the electrocardiogram at admission. Other potential causes of QT prolongation as hypothermia, dyselectrolitemia or QT prolonging drugs use were excluded. No regional neither global contractility dysfunction was observed on echocardiography. ECG recorded 6 hours after admission showed normalization of ST segment but only slight shortening of QTc to 550 ms.

Identification of Patients At-Risk of QT Interval Prolongation during Medication Reviews: A Missed Opportunity?

The prolongation of the QT interval is a relatively rare but serious adverse drug reaction. It can lead to torsade de pointes, which is potentially life-threatening. The study’s objectives were: determine the use of QT interval-prolonging drugs in an elderly community-dwelling population at risk of medication misadventure and identify recommendations regarding the risk of QT interval prolongation made by pharmacists when performing medication reviews. In a retrospective evaluation, 500 medication review reports from Australian pharmacists were analysed. In patients taking at least one QT interval-prolonging drug, the individual risk of drug-induced QT interval prolongation was assessed. Recommendations of pharmacists to avoid the occurrence of this drug-related problem were examined. There was a high prevalence of use of potentially QT interval-prolonging drugs (71% patients), with 11% of patients taking at least one drug with a known risk. Pharmacists provided specific recommendations in only eight out of 35 patients (23%) with a high-risk score and taking drugs with known risk of QT interval prolongation. Pharmacists’ recommendations, when present, were focused on drugs with known risk of QT interval prolongation, rather than patients’ additional risk factors. There is a need to improve knowledge and awareness of this topic among pharmacists performing medication reviews.

Persistent QT Prolongation in a Child with Gitelman Syndrome and SCN5A H558R Polymorphism

Gitelman syndrome (GS) is an inherited renal tubular disorder characterized by hypokalemic metabolic alkalosis, hypomagnesemia, and low urinary calcium excretion. While it is considered a benign disease, severe ventricular arrhythmia and sudden cardiac death related to the prolongation of the QT interval have been reported in rare cases. Herein we report a 13-year-old girl with GS who presented with persistent prolongation of the QT interval, even after being treated for hypokalemia and hypomagnesemia. Genetic analysis identified SCN5A H558R polymorphism, which modulates the function of myocardial sodium channel, and SLC12A3 A588V mutation, which causes GS. The SCN5A polymorphism and GS-related electrolyte disturbance might have contributed to the persistent QT prolongation in this patient. Although no ventricular arrhythmias were recorded in this case, careful cardiac surveillance should be applied for avoiding life-threatening cardiac events.

Moxifloxacin-induced QT interval prolongation and torsades de pointes: a narrative review

INTRODUCTION

Moxifloxacin is widely used for the treatment of a number of infectious diseases because of its favorable pharmacological profile and high clinical success rate. However, it is often criticized for its higher risk of QTc interval prolongation (QTIP) and torsades de pointes (TdP).

AREAS COVERED

A review of published literature on moxifloxacin-related QTIP and TdP. Readers will be provided with a comprehensive overview of the prevalence, cellular mechanism, risk factors, and magnitude of QTIP of moxifloxacin.

EXPERT OPINION

In healthy subjects, moxifloxacin prolongs the QTc interval by 11.5-19.5 ms, it binds at the Tyr652 residue in the S6 pore domain of the human ether a-go-go gene related potassium channel. Considerable QTIP (30-60 ms) have also been reported in some patients, for instance the incidence of QTIP (30-60 ms) in elderly pneumonia patients was 15.5%. Moxifloxacin-induced QTIP may be of little clinical importance in healthy individuals. However, marked QTIP (>60 ms) and TdP have been reported in high-risk patients (patients who have multiple QT prolonging risk factors). Patients must be thoroughly assessed prior to the use of moxifloxacin and high-risk patients must be identified using risk assessment tools to ensure safe use of moxifloxacin and to safeguard patients' health.

An Analysis of the Relationship Between Preclinical and Clinical QT Interval-Related Data

There has been significant focus on drug-induced QT interval prolongation caused by block of the human ether-a-go-go-related gene (hERG)-encoded potassium channel. Regulatory guidance has been implemented to assess QT interval prolongation risk: preclinical guidance requires a candidate drug's potency as a hERG channel blocker to be defined and also its effect on QT interval in a non-rodent species; clinical guidance requires a "Thorough QT Study" during development, although some QT prolonging compounds are identified earlier via a Phase I study. Clinical, heart rate-corrected QT interval (QTc) data on 24 compounds (13 positives; 11 negatives) were compared with their effect on dog QTc and the concentration of compound causing 50% inhibition (IC50) of hERG current. Concordance was assessed by calculating sensitivity and specificity across a range of decision thresholds, thus yielding receiver operating characteristic curves of sensitivity versus (1-specificity). The area under the curve of ROC curves (for which 0.5 and 1 indicate chance and perfect concordance, respectively) was used to summarize concordance. Three aspects of preclinical data were compared with the clinical outcome (receiver operating characteristic area under the curve values shown in brackets): absolute hERG IC50 (0.78); safety margin between hERG IC50 and clinical peak free plasma exposure (0.80); safety margin between QTc effects in dogs and clinical peak free plasma exposure (0.81). Positive and negative predictive values of absolute hERG IC50 indicated that from an early drug discovery perspective, low potency compounds can be progressed on the basis of a low risk of causing a QTc increase.

Anticancer drugs-related QTc prolongation, torsade de pointes and sudden death: current evidence and future research perspectives

Anticancer drugs may have proarrhythmic effects including drug-induced QT interval prolongation, which is of particular importance because it can lead to a fatal polymorphic ventricular tachycardia termed torsade de pointes (TdP). QT interval prolongation and TdP are rare life-threatening untoward effects of anticancer therapy, particularly with arsenic trioxides and anthracyclines, and even some novel molecular targeted drugs touted as 'tumor specific'. Several factors that affect myocardial repolarization can further increase the risk of TdP. This article reviews the mechanism of QT interval prolongation, risk factors for TdP and the QT toxicity of anticancer drugs as well as its management. Specific attention should be paid to high-risk populations such as patients with underlying heart diseases, electrolyte imbalance and bradycardia. To minimize the occurrence of QT interval prolongation and TdP, it is advisable to conduct a careful risk factor assessment before antitumor therapy. To this end, several new biomarkers have been introduced to predict TdP triggering and recent studies have pointed out the potential clinical relevance of genetic testing.

Gastroparesis: pharmacotherapy and cardiac risk

BACKGROUND

Gastroparesis is characterized by abnormal gastric motility and delayed emptying with symptoms of early satiety, postprandial fullness, bloating, nausea, vomiting and abdominal pain. Pharmacological discovery has been lagging because potential drugs often are associated with abnormalities of electrical conduction of the myocardium due to interaction with cardiac ion channels leading to limited pharmaceutical options for development of new drugs.

OBJECTIVE

Addresses the safety of drugs for gastroparesis in terms of cardiotoxicity related to the clinical use of prokinetics and antiemetics.

METHODS

Survey of QT drugs List and review of current literature.

RESULTS

Many prokinetic drugs are associated with cardiac adverse events and manifest as prolongation of ventricular repolarization, i.e., QT-interval prolongation of the electrocardiogram. This disturbance may develop into a potentially fatal polymorphic ventricular tachyarrhythmia; Torsade de Pointes. Co-administration of prokinetics with other drugs affecting the repolarization process, pharmacokinetic interactions leading to increased blood levels, or the presence of clinical risk factors could further increase the risk for cardiac arrhythmias.

CONCLUSIONS

It is important that clinicians managing gastroparesis are aware of the arrhythmogenic potential of drugs used clinically and risk factors that contribute to QT prolongation to safeguard patients at risk for drug-induced cardiac arrhythmia.

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.

Ventricular repolarization alterations in women with angina pectoris and suspected coronary microvascular dysfunction

OBJECTIVES

CMD could be the explanation of angina pectoris with no obstructive CAD and may cause ventricular repolarization changes. We compared T-wave morphology and QTc interval in women with angina pectoris with a control group as well as the associations with CMD.

METHODS

Women with angina pectoris and no obstructive coronary artery disease (n=138) and age-matched controls were compared in regard to QTc interval and morphology combination score (MCS) based on T-wave asymmetry, flatness and presence of T-wave notch. CMD was assessed as a coronary flow velocity reserve (CFVR) by transthoracic echocardiography.

RESULTS

Women with angina pectoris had significantly longer QTc intervals (429±20ms) and increased MCS (IQR) (0.73 [0.64-0.80]) compared with the controls (419±20ms) and (0.63 [(0.53-0.73]), respectively (both p<0.001). CFVR was associated with longer QTc interval (p=0.02), but the association was attenuated after multivariable adjustment (p=0.08).

CONCLUSION

This study suggests that women with angina pectoris have alterations in T-wave morphology as well as longer QTc interval compared with a reference population. CMD might be an explanation.

Characterizing QT interval prolongation in early clinical development: a case study with methadone

Recently, we have shown how pharmacokinetic–pharmacodynamic (PKPD) modeling can be used to assess the probability of QT interval prolongation both in dogs and humans. A correlation between species has been identified for a drug‐specific parameter, making it possible to prospectively evaluate nonclinical signals. Here, we illustrate how nonclinical data on methadone can be used to support the evaluation of dromotropic drug effects in humans. ECG and drug concentration data from a safety pharmacology study in dogs were analyzed using nonlinear mixed effects modeling. The slope of the PKPD model describing the probability of QT interval prolongation was extrapolated from dogs to humans and subsequently combined with methadone pharmacokinetic data as input for clinical trial simulations. Concentration versus time profiles were simulated for doses between 5 and 500 mg. Predicted peak concentrations in humans were then used as reference value to assess the probability of an increase in QT interval of ≥5 and ≥10 ms. Point estimates for the slope in dogs suggested low probability of ≥10 ms prolongation in humans, whereas an effect of approximately 5 ms increase is predicted when accounting for the 90% credible intervals of the drug‐specific parameter in dogs. Interspecies differences in drug disposition appear to explain the discrepancies between predicted and observed QT prolonging effects in humans. Extrapolation of the effects of racemic compound may not be sufficient to describe the increase in QT interval observed after administration of methadone to patients. Assessment of the contribution of enantioselective metabolism and active metabolites is critical.

Translating QT interval prolongation from conscious dogs to humans

AIM

In spite of screening procedures in early drug development, uncertainty remains about the propensity of new chemical entities (NCEs) to prolong the QT/QTc interval. The evaluation of proarrhythmic activity using a comprehensive in vitro proarrhythmia assay does not fully account for pharmacokinetic-pharmacodynamic (PKPD) differences in vivo. In the present study, we evaluated the correlation between drug-specific parameters describing QT interval prolongation in dogs and in humans.

METHODS

Using estimates of the drug-specific parameter, data on the slopes of the PKPD relationships of nine compounds with varying QT-prolonging effects (cisapride, sotalol, moxifloxacin, carabersat, GSK945237, SB237376 and GSK618334, and two anonymized NCEs) were analysed. Mean slope estimates varied between -0.98 ms μM-1 and 6.1 ms μM-1 in dogs and -10 ms μM-1 and 90 ms μM-1 in humans, indicating a wide range of effects on the QT interval. Linear regression techniques were then applied to characterize the correlation between the parameter estimates across species.

RESULTS

For compounds without a mixed ion channel block, a correlation was observed between the drug-specific parameter in dogs and humans (y = -1.709 + 11.6x; R2  = 0.989). These results show that per unit concentration, the drug effect on the QT interval in humans is 11.6-fold larger than in dogs.

CONCLUSIONS

Together with information about the expected therapeutic exposure, the evidence of a correlation between the compound-specific parameter in dogs and in humans represents an opportunity for translating preclinical safety data before progression into the clinic. Whereas further investigation is required to establish the generalizability of our findings, this approach can be used with clinical trial simulations to predict the probability of QT prolongation in humans.

Impact of QT interval prolongation following antiarrhythmic drug therapy on left ventricular function

AIM

We assessed whether antiarrhythmic drug-induced QT interval prolongation affects left ventricular function.

METHODS

Study population included 54 patients with symptomatic recent onset atrial fibrillation spontaneously cardioverted to sinus rhythm. Electrocardiographic and echocardiographic studies were done before initiating and after achieving drug's steady state.

RESULTS

Significantly prolonged corrected QT interval (QTc) was noticed following only sotalol and amiodarone. The corrected precontraction time increased after sotalol (p = 0.005) and amiodarone (p = 0.017), not propafenone (p = 0.139). Analysis results between ΔEF and ΔQTc, ΔEF and ΔQTc(p), ΔE/e' and ΔQTc, ΔE/e' and ΔQTc(p) for amiodarone group were (p = 0.66, p = 0.20, p = 0.66, p = 0.33), for sotalol (p = 0.36, p = 0.51, p = 0.44, p = 0.33) and for propafenone (p = 0.38, p = 0.12, p = 0.89, p = 0.61), respectively.

CONCLUSION

QT interval prolongation following antiarrhythmic therapy does not affect significantly left ventricular function.

Domperidone-Associated QT Interval Prolongation in Non-oncologic Pediatric Patients: A Review of the Literature

BACKGROUND

Domperidone is a prokinetic agent used to treat pediatric gastroesophageal reflux disease. Health Canada has issued warnings about an increased risk of domperidone-associated ventricular arrhythmias and sudden cardiac death. However, the supporting data referred only to adult patients; therefore, extrapolating the safety risks to pediatric patients is difficult.

OBJECTIVE

To summarize and evaluate the evidence for domperidone-associated QT interval prolongation, ventricular arrhythmias, and sudden cardiac death to determine the safety of this drug for pediatric patients.

DATA SOURCES

Two databases (MEDLINE [1946 to August 2015] and Embase [1980 to August 2015]) were searched with the following Medical Subject Headings and keywords: "domperidone", "arrhythmias, cardiac", "death, sudden, cardiac", "electrocardiography", "heart diseases", "long QT syndrome", "tachycardia, ventricular", "torsades de pointes", and "ventricular fibrillation". The search was limited to studies conducted in humans under 18 years of age and published in English.

STUDY SELECTION AND DATA EXTRACTION

Original research included in this review reported on the cardiac-related safety of domperidone in nononcologic patients under 18 years of age.

DATA SYNTHESIS

Of the 5 studies meeting the inclusion criteria (n = 137 patients), one reported a statistically significant change in the corrected QT (QTc) interval, but the clinical significance was unclear. Most of the studies reported rare occurrences of pathological QTc intervals in a limited number of patients. However, confounding factors (e.g., abnormal electrolyte level or concurrent medications) were not consistently considered. Potential bias might have been alleviated by blinding of electrocardiogram (ECG) assessors; however, this was not consistently implemented. The designs of the included studies did not allow assessment of causality. The results should be interpreted with caution.

CONCLUSIONS

Although the available evidence is limited, pathological QTc intervals were noted among a small number of infants, which supports the possibility of domperidone-associated risk of prolonged QTc interval. Because of the potential severity of QT interval prolongation, individual assessment and routine ECG monitoring should be implemented for patients receiving domperidone.

Electrocardiographic predictors of coronary microvascular dysfunction in patients with non-obstructive coronary artery disease: Utility of a novel T wave analysis program

BACKGROUND

Coronary microvascular dysfunction (CMD) is linked to adverse cardiovascular events. Definitive diagnosis of CMD requires invasive provocative testing during angiography. We developed and tested a novel computerized T wave analysis tool to identify electrocardiographic signatures of CMD.

METHODS

1552 patients underwent an invasive assessment of coronary microvascular function. Patients with interpretable pre-procedural ECGs were divided into 2 age and sex matched groups (n=261 in each group, 75% female): normal microvascular function, CFR>2.5 (CFR+), and abnormal microvascular function, CFR ≤ 2.5 (CFR-). ECGs were evaluated using a novel T wave program that quantified subtle changes in T wave morphology.

RESULTS

T wave repolarization parameters were significantly different between patients with normal and abnormal microvascular function. The top 3 features in males comprised of T wave area in V6 (CFR+: 10091.4 mV(2) vs. CFR-: 8152.3 mV(2), p<0.05); T1 Y-center of gravity in lead II (CFR+: 17.8 mV vs. CFR-: 22.4, p<0.005) and T Peak-T End in lead II (CFR+: 97.6 msec vs. CFR-: 91.1 msec, p<0.05). These could identify the presence of an abnormal CFR with 74 ± 0.2% accuracy. In females, the top 3 features were T wave right slope lead V6 (CFR+: -2489.1 mV/msec vs. CFR-: -2352.3 mV/msec, p<0.005); Amplitude in V6 (CFR+: 190.4 mV vs. 172.7 mV, p=0.05) and Y-center of gravity in lead V1 (CFR+: 33.3 vs. CFR-: 40.0, p=0.001). These features could identify the presence of an abnormal CFR with 67 ± 0.3% accuracy.

CONCLUSION

Our data demonstrates that a computer-based repolarization measurement tool may identify electrocardiographic signatures of CMD.

Model-based evaluation of drug-induced QTc prolongation for compounds in early development

AIMS

Significant differences between dogs and humans have been observed in the concentration-QTc effect relationship of compounds with known pro-arrhythmic properties. These findings suggest that interspecies differences must be considered when evaluating drug effects. The aim of this study was to evaluate the performance of a model-based approach to assess the risk of QTc prolongation for three investigational compounds (NCE01, NCE02 and NCE03).

METHODS

Pharmacokinetic and pharmacodynamic data from experiments in conscious dogs and healthy subjects were included in this analysis. Pharmacokinetic modelling and deconvolution methods were applied to derive drug concentrations at the time of each QT measurement. An integrated pharmacokinetic-pharmacodynamic (PKPD) model was then used to describe QT prolongation. A threshold of ≥10 ms was used to characterize the probability of QTc prolongation.

RESULTS

The PKPD relationships of all three compounds were successfully described in both species. A strong effect was observed after administration of NCE01 to dogs and humans, with a slope of 0.0061 and 0.0662 ms nm(-1), respectively, and maximal probability of QTc prolongation ≥10 ms at peak concentration. For NCE02 and NCE03, QTc-shortening and borderline QT effects were observed both in dogs and humans, as described by negative or very shallow slopes (NCE02, -0.00098 and -0.01 ms nm(-1); NCE03, 0.00064 and -0.0002 ms nm(-1)).

CONCLUSIONS

Whilst NEC01 shows clear pro-arrhythmic effects, the liability for QT/QTc prolongation for NCE02 and NCE03 can be deemed low at the expected therapeutic exposure. Moreover, our results show the advantages of an integrated PKPD approach as the basis for translating pro-arrhythmic effects from dogs to humans.

Assessment of Interspecies Differences in Drug-Induced QTc Interval Prolongation in Cynomolgus Monkeys, Dogs and Humans

Background and Purpose

The selection of the most suitable animal species and subsequent translation of the concentration-effect relationship to humans are critical steps for accurate assessment of the pro-arrhythmic risk of candidate molecules. The objective of this investigation was to assess quantitatively the differences in the QTc prolonging effects of moxifloxacin between cynomolgus monkeys, dogs and humans. The impact of interspecies differences is also illustrated for a new candidate molecule.

Experimental Approach

Pharmacokinetic data and ECG recordings from pre-clinical protocols in monkeys and dogs and from a phase I trial in healthy subjects were identified for the purpose of this analysis. A previously established Bayesian model describing the combined effect of heart rate, circadian variation and drug effect on the QT interval was used to describe the pharmacokinetic-pharmacodynamic relationships. The probability of a ≥10 ms increase in QT was derived as measure of the pro-arrhythmic effect.

Key Results

For moxifloxacin, the concentrations associated with a 50% probability of QT prolongation ≥10 ms (Cp₅₀) varied from 20.3 to 6.4 and 2.6 μM in dogs, monkeys and humans, respectively. For NCE05, these values were 0.4 μM vs 2.0 μM for monkeys and humans, respectively.

Conclusions and Implications

Our findings reveal significant interspecies differences in the QT-prolonging effect of moxifloxacin. In addition to the dissimilarity in pharmacokinetics across species, it is likely that differences in pharmacodynamics also play an important role. It appears that, regardless of the animal model used, a translation function is needed to predict concentration-effect relationships in humans.

Coronary microvascular dysfunction is associated with baseline QTc prolongation amongst patients with chest pain and non-obstructive coronary artery disease

BACKGROUND

Coronary microvascular dysfunction (CMD) causes ischemia and is linked to adverse cardiovascular events. Acute transmural ischemia is associated with QT prolongation, but whether CMD affects repolarization is unknown. The aim of this study was to determine if CMD is associated with prolongation of resting heart rate corrected QT interval (QTc).

METHODS

In patients presenting to the catheterization laboratory with chest pain and non-obstructive coronary artery disease (CAD) at angiography, coronary flow reserve (CFR) in response to intracoronary adenosine was measured and compared to baseline to give a CFR ratio. The Bazett's-derived QTc was manually derived from patients' 12-lead ECG obtained prior to the procedure. QTc was compared between patients with normal and abnormal (CFR ratio≤2.5) coronary microvascular function.

RESULTS

Of the 926 patients included in this study, 281 patients (30%) had CMD (mean age 53.2 years [SD 12.7], 25% male). QTc was significantly longer in those with an abnormal CFR response to adenosine (median [Q1, Q3] ms: 420 [409, 438] vs. 416 [405, 432]; p value<0.001) and patients in the lowest quartile of CFR had a significantly longer QTc compared to those in the highest quartile (median [Q1, Q3] ms: 420 [409, 439] vs. 413 [402, 426]; p<0.001). In a linear regression model adjusting for age and sex, CMD was associated with an increase in QTc of 3.09 ms (p=0.055).

CONCLUSION

Our data suggest that CMD may be associated with an increase in baseline QTc, however the precise clinical relevance of this finding needs to be better investigated in larger clinical studies.

[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.

Hypoglycaemia and QT interval prolongation in type 1 diabetes--bridging the gap between clamp studies and spontaneous episodes

AIMS

We propose a study design with controlled hypoglycaemia induced by subcutaneous injection of insulin and matched control episodes to bridge the gap between clamp studies and studies of spontaneous hypoglycaemia. The observed prolongation of the heart rate corrected QT interval (QTc) during hypoglycaemia varies greatly between studies.

METHODS

We studied ten adults with type 1 diabetes (age 41±15years) without cardiovascular disease or neuropathy. Single-blinded hypoglycaemia was induced by a subcutaneous insulin bolus followed by a control episode on two occasions separated by 4weeks. QT intervals were measured using the semi-automatic tangent approach, and QTc was derived by Bazett's (QTcB) and Fridericia's (QTcF) formulas.

RESULTS

QTcB increased from baseline to hypoglycaemia (403±20 vs. 433±39ms, p<0.001). On the euglycaemia day, QTcB also increased (398±20 vs. 410±27ms, p<0.01), but the increase was less than during hypoglycaemia (p<0.001). The same pattern was seen for QTcF. Plasma adrenaline levels increased significantly during hypoglycaemia compared to euglycaemia (p<0.01). Serum potassium levels decreased similarly after insulin injection during both hypoglycaemia and euglycaemia.

CONCLUSIONS

Hypoglycaemia as experienced after a subcutaneous injection of insulin may cause QTc prolongation in type 1 diabetes. However, the magnitude of prolongation is less than typically reported during glucose clamp studies, possible because of the study design with focus on minimizing unwanted study effects.

Anti-addiction drug ibogaine inhibits hERG channels: a cardiac arrhythmia risk

Ibogaine, an alkaloid derived from the African shrub Tabernanthe iboga, has shown promising anti-addictive properties in animals. Anecdotal evidence suggests that ibogaine is also anti-addictive in humans. Thus, it alleviates drug craving and impedes relapse of drug use. Although not licensed as therapeutic drug, and despite evidence that ibogaine may disturb the rhythm of the heart, this alkaloid is currently used as an anti-addiction drug in alternative medicine. Here, we report that therapeutic concentrations of ibogaine reduce currents through human ether-a-go-go-related gene potassium channels. Thereby, we provide a mechanism by which ibogaine may generate life-threatening cardiac arrhythmias.

Anti-addiction drug ibogaine inhibits voltage-gated ionic currents: a study to assess the drug's cardiac ion channel profile

The plant alkaloid ibogaine has promising anti-addictive properties. Albeit not licensed as a therapeutic drug, and despite hints that ibogaine may perturb the heart rhythm, this alkaloid is used to treat drug addicts. We have recently reported that ibogaine inhibits human ERG (hERG) potassium channels at concentrations similar to the drugs affinity for several of its known brain targets. Thereby the drug may disturb the heart's electrophysiology. Here, to assess the drug's cardiac ion channel profile in more detail, we studied the effects of ibogaine and its congener 18-Methoxycoronaridine (18-MC) on various cardiac voltage-gated ion channels. We confirmed that heterologously expressed hERG currents are reduced by ibogaine in low micromolar concentrations. Moreover, at higher concentrations, the drug also reduced human Nav1.5 sodium and Cav1.2 calcium currents. Ion currents were as well reduced by 18-MC, yet with diminished potency. Unexpectedly, although blocking hERG channels, ibogaine did not prolong the action potential (AP) in guinea pig cardiomyocytes at low micromolar concentrations. Higher concentrations (≥ 10 μM) even shortened the AP. These findings can be explained by the drug's calcium channel inhibition, which counteracts the AP-prolonging effect generated by hERG blockade. Implementation of ibogaine's inhibitory effects on human ion channels in a computer model of a ventricular cardiomyocyte, on the other hand, suggested that ibogaine does prolong the AP in the human heart. We conclude that therapeutic concentrations of ibogaine have the propensity to prolong the QT interval of the electrocardiogram in humans. In some cases this may lead to cardiac arrhythmias.

Designing and interpreting the results of first-time-to-man studies

First human administration of a new chemical entity (NCE) constitutes a critical step in drug development. The primary objective of such a study is the assessment of the shortterm safety and tolerability of single and multiple doses of the NCE in healthy volunteers. Secondary objectives are to obtain preliminary data on the pharmacokinetics and pharmacodynamics using surrogate or biornarkers of the beneficial as well as the adverse effects of the drug. Interpretation of safety data should be cautious and mainly based on comparisons with placebo. A special focus should be made on the assessment of adverse events, liver enzymes, and cardiac repolarization. Well-designed, first-time-to-man studies should determine the safety of the NCE in humans and predict the dose range that may be used to safely and accurately conduct further clinical trials in the target patient population based on safety data (maximum tolerated dose), pharmacodynamics (minimum active dose, duration of action, and dosage regimen), and pharmacokinetics (dosage regimen).