Covariate analysis of QTc and T-wave morphology: new possibilities in the evaluation of drugs that affect cardiac repolarization

Action potential morphology affects T-wave symmetry (simulation study)

BACKGROUND

Assessing T-wave symmetry in addition to QT subintervals measurements can provide novel independent data about ventricular repolarization abnormalities linked with arrhythmogenesis. However, the causes of the changes of T-wave symmetry are not completely understood. In silico studies showed that the more symmetrical T-waves were associated with shorter action potential duration (APD) and larger dispersion of ventricular repolarization (DOR). The aim of present simulation was to study the association between T-wave symmetry and action potential (AP) shape.

METHODS

ECGs were simulated using a cellular automata model shaped as a ventricular wall segment, and two biophysically-detailed models of ventricular AP - the rabbit and the human. The symmetry ratio (SR) was calculated as a T-wave onset-peak to peak-end area ratio. The individual and combined effects of APD, DOR and AP shape on SR were simulated. To study the effect of AP shape, different APs from triangulated to rectangular were simulated.

RESULTS

The simulations showed that AP shape along with APD and DOR contributes much to T-wave symmetry. APs with a flat phase 3 (triangulated) produced asymmetrical T-waves (SR ≥ 1.5) in all simulations, except the shortest APD range. APs with a rapid phase 3 (rectangular) were associated with more symmetrical T-waves (SR ≤ =1) both at the short and the long APDs.

CONCLUSION

SR marker in combination with the standard ECG parameters (QT interval, Tpeak-Tend interval) may be useful to identify the proarrhythmic triangulated AP shape.

The diagnostic role of T wave morphology biomarkers in congenital and acquired long QT syndrome: A systematic review

INTRODUCTION

QTc prolongation is key in diagnosing long QT syndrome (LQTS), however 25%-50% with congenital LQTS (cLQTS) demonstrate a normal resting QTc. T wave morphology (TWM) can distinguish cLQTS subtypes but its role in acquired LQTS (aLQTS) is unclear.

METHODS

Electronic databases were searched using the terms "LQTS," "long QT syndrome," "QTc prolongation," "prolonged QT," and "T wave," "T wave morphology," "T wave pattern," "T wave biomarkers." Whole text articles assessing TWM, independent of QTc, were included.

RESULTS

Seventeen studies met criteria. TWM measurements included T-wave amplitude, duration, magnitude, Tpeak-Tend, QTpeak, left and right slope, center of gravity (COG), sigmoidal and polynomial classifiers, repolarizing integral, morphology combination score (MCS) and principal component analysis (PCA); and vectorcardiographic biomarkers. cLQTS were distinguished from controls by sigmoidal and polynomial classifiers, MCS, QTpeak, Tpeak-Tend, left slope; and COG x axis. MCS detected aLQTS more significantly than QTc. Flatness, asymmetry and notching, J-Tpeak; and Tpeak-Tend correlated with QTc in aLQTS. Multichannel block in aLQTS was identified by early repolarization (ERD30% ) and late repolarization (LRD30% ), with ERD reflecting hERG-specific blockade. Cardiac events were predicted in cLQTS by T wave flatness, notching, and inversion in leads II and V5 , left slope in lead V6 ; and COG last 25% in lead I. T wave right slope in lead I and T-roundness achieved this in aLQTS.

CONCLUSION

Numerous TWM biomarkers which supplement QTc assessment were identified. Their diagnostic capabilities include differentiation of genotypes, identification of concealed LQTS, differentiating aLQTS from cLQTS; and determining multichannel versus hERG channel blockade.

Effect of hydroxychloroquine on the cardiac ventricular repolarization: A randomized clinical trial

AIMS

Hydroxychloroquine has been suggested as possible treatment for severe acute respiratory syndrome-coronavirus-2. Studies reported an increased risk of QTcF-prolongation after treatment with hydroxychloroquine. The aim of this study was to analyse the concentration-dependent effects of hydroxychloroquine on the ventricular repolarization, including QTcF-duration and T-wave morphology.

METHODS

Twenty young (≤30 y) and 20 elderly (65-75 y) healthy male subjects were included. Subjects were randomized to receive either a total dose of 2400 mg hydroxychloroquine over 5 days, or placebo (ratio 1:1). Follow-up duration was 28 days. Electrocardiograms (ECGs) were recorded as triplicate at baseline and 4 postdose single recordings, followed by hydroxychloroquine concentration measurements. ECG intervals (RR, QRS, PR, QTcF, J-Tpc, Tp-Te) and T-wave morphology, measured with the morphology combination score, were analysed with a prespecified linear mixed effects concentration-effect model.

RESULTS

There were no significant associations between hydroxychloroquine concentrations and ECG characteristics, including RR-, QRS- and QTcF-interval (P = .09, .34, .25). Mean ΔΔQTcF-interval prolongation did not exceed 5 ms and the upper limit of the 90% confidence interval did not exceed 10 ms at the highest measured concentrations (200 ng/mL). There were no associations between hydroxychloroquine concentration and the T-wave morphology (P = .34 for morphology combination score). There was no significant effect of age group on ECG characteristics.

CONCLUSION

In this study, hydroxychloroquine did not affect ventricular repolarization, including the QTcF-interval and T-wave morphology, at plasma concentrations up to 200 ng/mL. Based on this analysis, hydroxychloroquine does not appear to increase the risk of QTcF-induced arrhythmias.

Clinical characterization of men with long QT syndrome and torsades de pointes associated with hypogonadism: A review and pharmacovigilance study

BACKGROUND

Long QT syndrome (LQTS) can cause the potentially fatal ventricular tachycardia torsades de pointes (TdP). QT interval corrected for heart rate (QTc) is shorter in men than in women, with testosterone contributing to shorten QTc. We recently described male hypogonadism as a reversible risk factor for acquired LQTS and TdP, but the clinical characteristics of such patients have not been characterized.

AIMS

To describe the clinical characteristics of men with acquired LQTS or TdP associated with hypogonadism caused by endocrine conditions or androgen deprivation therapy (ADT), and to evaluate the relationship between testosterone concentrations and electrocardiographic changes.

METHODS

We searched MEDLINE (to 04 January 2019) and the French pharmacovigilance database (to 09 August 2018) to identify male cases of acquired LQTS and TdP associated with endocrine hypogonadism or ADT; their narratives were gathered from reporting collaborators.

RESULTS

We identified seven cases of TdP (one fatal) with endocrine hypogonadism, abnormally long QTc and morphologically abnormal T-wave notches. After reversion of low testosterone concentrations in the surviving patients (N=6), QTc shortened, T-wave morphology normalized and there was no TdP recurrence. Among these cases, none had mutation in the LQTS genes, three men required testosterone and three had reversible hypogonadism after resolution of a concurrent acute severe illness. We found an additional 27 reports of men with LQTS (N=6), TdP (N=9; 2/9 fatal) or sudden death (N=12; 10/12 fatal) suspected to be induced or favoured by ADT (24/27 for prostate cancer). Generally, after ADT withdrawal, QTc shortened and no TdP recurred.

CONCLUSION

We propose seeking for hypogonadism caused by endocrine conditions or ADT in men presenting with TdP. Caution is warranted when ADT is used in situations at risk of TdP. Testosterone may be useful to treat or prevent TdP.

Androgenic Effects on Ventricular Repolarization: A Translational Study From the International Pharmacovigilance Database to iPSC-Cardiomyocytes

BACKGROUND

Male hypogonadism, arising from a range of etiologies including androgen-deprivation therapies (ADTs), has been reported as a risk factor for acquired long-QT syndrome (aLQTS) and torsades de pointes (TdP). A full description of the clinical features of aLQTS associated with ADT and of underlying mechanisms is lacking.

METHODS

We searched the international pharmacovigilance database VigiBase for men (n=6 560 565 individual case safety reports) presenting with aLQTS, TdP, or sudden death associated with ADT. In cardiomyocytes derived from induced pluripotent stem cells from men, we studied electrophysiological effects of ADT and dihydrotestosterone.

RESULTS

Among subjects receiving ADT in VigiBase, we identified 184 cases of aLQTS (n=168) and/or TdP (n=68; 11% fatal), and 99 with sudden death. Of the 10 ADT drugs examined, 7 had a disproportional association (reporting odds ratio=1.4-4.7; P<0.05) with aLQTS, TdP, or sudden death. The minimum and median times to sudden death were 0.25 and 92 days, respectively. The androgen receptor antagonist enzalutamide was associated with more deaths (5430/31 896 [17%]; P<0.0001) than other ADT used for prostate cancer (4208/52 089 [8.1%]). In induced pluripotent stem cells, acute and chronic enzalutamide (25 µM) significantly prolonged action potential durations (action potential duration at 90% when paced at 0.5 Hz; 429.7±27.1 (control) versus 982.4±33.2 (acute, P<0.001) and 1062.3±28.9 ms (chronic; P<0.001), and generated afterdepolarizations and/or triggered activity in drug-treated cells (11/20 acutely and 8/15 chronically). Enzalutamide acutely and chronically inhibited delayed rectifier potassium current, and chronically enhanced late sodium current. Dihydrotestosterone (30 nM) reversed enzalutamide electrophysiological effects on induced pluripotent stem cells.

CONCLUSIONS

QT prolongation and TdP are a risk in men receiving enzalutamide and other ADTs.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT03193138.

Assessment of trazodone-induced cardiotoxicity after repeated doses in rats

Trazodone (TRZ) is an antidepressant drug commonly used in the treatment of depression, anxiety, and insomnia. Although some studies demonstrated the adverse effects of TRZ related to cardiovascular system, the conflicting results were observed in these studies. Therefore, we aimed to investigate the cardiac adverse effects of TRZ in rats at repeated doses in our study. In accordance with this purpose, TRZ was administered orally to rats at 5, 10, and 20 mg/kg doses for 28 days. Electrocardiogram records, serum aspartate aminotransferase (AST), lactate dehydrogenase, creatine kinase-myoglobin band, cardiac troponin-T (cTn-T) levels, DNA damage in cardiomyocytes, and histologic view of heart tissues were evaluated. In addition, glutathione (GSH) and malondialdehyde (MDA) levels were measured to determine the oxidative status of cardiac tissue after TRZ administration. Heart rate was decreased, PR interval was prolonged, and QRS and T amplitudes were decreased in 20 mg/kg TRZ-administered group compared to the control group. Serum AST and cTn-T levels were significantly increased in 10 and 20 mg/kg TRZ-administered rats with respect to control rats. DNA damage was significantly increased in these groups. Additionally, degenerative histopathologic findings were observed in TRZ-administered groups. Although there was no difference in MDA levels between groups, GSH levels were significantly decreased in 10 and 20 mg/kg TRZ-administered groups compared to the control group. Our results have shown that TRZ induced cardiotoxicity in rats dose-dependently. It is assumed that oxidative stress related to GSH depletion may be accompanied by these adverse effects.

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.

Major rapid weight loss induces changes in cardiac repolarization

INTRODUCTION

Obesity is associated with increased all-cause mortality, but weight loss may not decrease cardiovascular events. In fact, very low calorie diets have been linked to arrhythmias and sudden death. The QT interval is the standard marker for cardiac repolarization, but T-wave morphology analysis has been suggested as a more sensitive method to identify changes in cardiac repolarization. We examined the effect of a major and rapid weight loss on T-wave morphology.

METHODS AND RESULTS

Twenty-six individuals had electrocardiograms (ECG) taken before and after eight weeks of weight loss intervention along with plasma measurements of fasting glucose, HbA1c, and potassium. For assessment of cardiac repolarization changes, T-wave Morphology Combination Score (MCS) and ECG intervals: RR, PR, QT, QTcF (Fridericia-corrected QT-interval), and QRS duration were derived. The participants lost on average 13.4% of their bodyweight. MCS, QRS, and RR intervals increased at week 8 (p<0.01), while QTcF and PR intervals were unaffected. Fasting plasma glucose (p<0.001) and HbA1c both decreased at week 8 (p<10(-5)), while plasma potassium was unchanged. MCS but not QTcF was negatively correlated with HbA1c (p<0.001) and fasting plasma glucose (p<0.01).

CONCLUSION

Rapid weight loss induces changes in cardiac repolarization. Monitoring of MCS during calorie restriction makes it possible to detect repolarization changes with higher discriminative power than the QT-interval during major rapid weight loss interventions. MCS was correlated with decreased HbA1c. Thus, sustained low blood glucose levels may contribute to repolarization changes.

Cardiac effects of sertindole and quetiapine: analysis of ECGs from a randomized double-blind study in patients with schizophrenia

The QT interval is the most widely used surrogate marker for predicting TdP; however, several alternative surrogate markers, such as Tpeak-Tend (TpTe) and a quantitative T-wave morphology combination score (MCS) have emerged. This study investigated the cardiac effects of sertindole and quetiapine using the QTc interval and newer surrogate markers. Data were derived from a 12 week randomized double-blind study comparing flexible dosage of sertindole 12-20mg and quetiapine 400-600mg in patients with schizophrenia. ECGs were recorded digitally at baseline and after 3, 6 and 12 weeks. Between group effects were compared by using a mixed effect model, whereas assessment within group was compared by using a paired t-test. Treatment with sertindole was associated with QTcF and QTcB interval prolongation and an increase in MCS, T-wave asymmetry, T-wave flatness and TpTe. The mean increase in QTcF from baseline to last observation was 12.1ms for sertindole (p<0.001) and -0.5ms for quetiapine (p=0.8). Quetiapine caused no increase in MCS, T-wave asymmetry, T-wave flatness or TpTe compared to baseline. In the categorical analysis, there were 11 patients (9.6%) receiving quetiapine who experienced more than 20ms QTcF prolongation compared with 36 patients (33.3%) in the sertindole group. Sertindole (12-20mg) was associated with moderate QTc prolongation and worsening of T-wave morphology in a study population of patients with schizophrenia. Although, quetiapine (400-600mg) did not show worsening of repolarization measures some individual patients did experience significant worsening of repolarization. Clinical Trials NCT00654706.

Electrocardiographic markers of repolarization heterogeneity during dofetilide or sotalol initiation for paroxysmal atrial fibrillation

Serial electrocardiographic monitoring of ΔQTc as an assumed harbinger of proarrhythmia is currently recommended for dofetilide and sotalol initiation. Markers of repolarization heterogeneity such as increased peak to end of T-wave (TpTe) duration and abnormal T-wave morphology may also predict proarrhythmia. We investigated whether such T-wave measurements on baseline electrocardiogram will correlate with ΔQTc after drug initiation. An analysis of 140 consecutive patients with paroxysmal atrial fibrillation hospitalized in sinus rhythm for sotalol or dofetilide initiation was performed. Baseline and serial electrocardiograms were analyzed using QT Guard Plus software (GE Healthcare), which measured QTc and TpTe and scored T-wave morphology for asymmetry, notching, and flatness using T-wave vector magnitude and principal component analysis algorithms. Sotalol and dofetilide were administered in 71% and 29% of patients, respectively. Mean age was 61 ± 14 years, and 34% were women. After a single dose of either drug, there was a statistically significant increase in QTc and TpTe (p <0.01), as well as composite and individual T-wave markers of repolarization heterogeneity (p <0.01). QTc increased by a mean of 19 ± 30 ms after initial antiarrhythmic dose. ΔQTc was inversely related to baseline QTc and TpTe (p <0.01). After controlling for baseline QTc, there was no independent association between T-wave markers of repolarization heterogeneity and ΔQTc. In conclusion, for patients with paroxysmal atrial fibrillation admitted for dofetilide or sotalol loading, T-wave markers of increased repolarization heterogeneity are measurable within hours after initiation. A shorter baseline QTc is associated with an increased ΔQTc; however, there is no independent relation between baseline T-wave markers of repolarization heterogeneity and ΔQTc.

Effects of bilastine on T-wave morphology and the QTc interval: a randomized, double-blind, placebo-controlled, thorough QTc study

BACKGROUND AND OBJECTIVES

The International Conference of Harmonisation (ICH) E14 guideline for thorough QT studies requires assessing the propensity of new non-antiarrhythmic drugs to affect cardiac repolarization. The present study investigates whether a composite ECG measure of T-wave morphology (Morphology Combination Score [MCS]) can be used together with the heart rate corrected QT interval (QTc) in a fully ICH E14-compliant thorough QT study to exclude clinically relevant repolarization effects of bilastine, a novel antihistamine.

METHODS

Thirty participants in this crossover study were randomly assigned to receive placebo, moxifloxacin 400 mg, bilastine at therapeutic and supratherapeutic doses (20 and 100 mg) and bilastine 20 mg co-administered with ketoconazole 400 mg. Resting ECGs recorded at 12 nominal time points before and after treatments were used to determine Fridericia corrected QTc (QTcF) and MCS from the T-wave characteristics: asymmetry, flatness and notching.

RESULTS

There were no effects of bilastine monotherapy (20 and 100 mg) on MCS or QTcF at those study times where the bilastine plasma concentrations were highest. MCS changes for bilastine monotherapy did not exceed the normal intrasubject variance of T-wave shapes for triplicate ECG recordings. Maximum QTcF prolongation for bilastine monotherapy was 5 ms or less: 3.8 ms (90% CI 0.3, 7.3 ms) for bilastine 20 mg and 5.0 ms (90% CI 2.0, 8.0 ms) for bilastine 100 mg. There were no indications of bilastine inducing larger repolarization effects on T-wave morphology as compared with the QTcF interval, as evidenced by the similarity of z-score equivalents for placebo-corrected changes in MCS and QTcF values.

CONCLUSION

This study shows that bilastine, at therapeutic and supratherapeutic dosages, does not induce any effects on T-wave morphology or QTcF. These results confirm the absence of an effect for bilastine on cardiac repolarization.

Ziprasidone and the corrected QT interval: a comprehensive summary of clinical data

BACKGROUND

Prolongation of the corrected QT interval (QTc) is understood to be a predictor of risk for ventricular arrhythmia; consequently, data on QTc effects of drugs are used by regulatory bodies to evaluate potential safety risks. Clinical pharmacology studies in adults receiving oral ziprasidone demonstrated a dose-dependent mean increase (4.5-19.5 milliseconds [ms]) in QTc over the range of 40-160 mg/d with a small incremental increase (22.5 ms) at 320 mg/d. In a comparative study of ziprasidone versus five antipsychotics, the mean QTc increase at steady state maximum concentration (C(max)) for ziprasidone was 15.9 ms. Accordingly, the effects of ziprasidone on QTc were studied in phase II-IV randomized controlled trials (RCTs).

OBJECTIVE

The objective of this study was to provide clinicians and clinical researchers with a comprehensive analysis of QTc changes associated with ziprasidone based on data from Pfizer-sponsored phase II-IV RCTs in schizophrenia or bipolar disorder patients, safety reports and post-marketing surveillance.

METHODS

The following analyses of data were conducted to obtain a comprehensive summary of QTc data on ziprasidone: (i) post hoc analyses (using primarily descriptive statistics) of pooled QTc data (Fridericia correction) from more than 40 phase II-IV adult ziprasidone RCTs organized according to the following subgroups: all monotherapy studies in schizophrenia and bipolar disorder, all intramuscular (IM) studies, adjunctive studies in bipolar disorder and fixed-dose oral studies; (ii) post hoc analyses from 36 phase II-IV adult ziprasidone RCTs exploring the relationship between QTc change from baseline and baseline QTc in adults; (iii) post hoc analyses from phase II-IV adult ziprasidone RCTs modelling QTc change as a function of ziprasidone concentration in both adult (17 studies) and paediatric (5 studies) subjects; (iv) cardiac adverse event (AE) reports from all phase II-IV adult ziprasidone RCTs in schizophrenia; (v) a large simple trial entitled Ziprasidone Observational Study of Cardiac Outcomes (ZODIAC) in 18 154 subjects with schizophrenia (the only previously reported results included here); and (vi) cardiac-related AEs presented in a ziprasidone post-marketing surveillance report created in 2007.

RESULTS

A total of 4306 adults received ziprasidone in placebo- and active-comparator phase II-IV RCTs and had evaluable QTc data. One subject reached a QTc ≥480 ms; 33 (0.8%) had a QTc ≥450 ms. QTc prolongation ≥30 ms was observed in 389 subjects (9.0%); ≥60 ms in 30 (0.7%); and ≥75 ms in 12 (0.3%). In the placebo-controlled studies, mean change in QTc from baseline to end of study was 3.6 (± 20.8) ms in the ziprasidone group; the corresponding QTc change in the pooled placebo group was -0.3 (± 20.6) ms. Data from IM studies, and bipolar studies in which ziprasidone was used adjunctively with lithium, valproate or lamotrigine, demonstrated similar QTc effects. A scatter-plot of QTc prolongation against baseline QTc showed QTc prolongation ≥60 ms exclusively in adult subjects with a baseline QTc ≤400 ms. The final concentration-response analysis model, comprising 2966 data points from 1040 subjects, estimates an increase in QTc of 6 ms for each 100 ng/mL increase in ziprasidone concentration. The large simple trial (ZODIAC) failed to show that ziprasidone is associated with an elevated risk of non-suicidal mortality relative to olanzapine in real-world use. Post-marketing data over a 5-year period did not show a signal of increased cardiac AEs.

CONCLUSIONS

These analyses provide the first comprehensive summary of QTc changes associated with ziprasidone based on Pfizer-sponsored phase II-IV RCTs, safety reports and post-marketing surveillance. The results of the analyses of pooled data from phase II-IV RCTs in adults demonstrate a modest mean increase in QTc, infrequent QTc prolongation ≥60 ms (<1.0%) and rare observation of QTc ≥480 ms. These data are consistent with results from ziprasidone clinical pharmacology studies, safety reports and post-marketing surveillance. Taken together, they provide the most comprehensive evidence published to date that ziprasidone appears to be safe when used as indicated in patients with schizophrenia or bipolar disorder.

Effect of nalmefene 20 and 80 mg on the corrected QT interval and T-wave morphology: a randomized, double-blind, parallel-group, placebo- and moxifloxacin-controlled, single-centre study

BACKGROUND

Nalmefene is an orally administered competitive opioid receptor antagonist targeted at reducing alcohol consumption in alcohol-dependent patients. As part of the regulatory requirements for drug approval, the potential of novel compounds for causing unwanted proarrhythmia should be studied in a thoroughly designed clinical QT/corrected QT (QTc) study (International Conference on Harmonisation [ICH] E14 guideline).

OBJECTIVE

This study was designed to evaluate whether nalmefene 20 and 80 mg/day induced changes in cardiac repolarization biomarkers indicative of proarrhythmia (the QTc interval and T-wave morphology).

METHODS

This was a prospective, randomized, double-blind, parallel-group, placebo- and moxifloxacin-controlled, single-centre study carried out in a clinical pharmacology unit. The study included 270 healthy male and female subjects (age 18-45 years). The subjects were randomized to a 7-day treatment period of placebo, nalmefene 20 mg/day or nalmefene 80 mg/day, or placebo for 6 days followed by a single dose of moxifloxacin 400 mg on day 7. Serial triplicate ECGs were obtained over a 24-hour period at protocol-defined time-points. The primary protocol-defined endpoint was the largest time-matched baseline- and placebo-adjusted mean difference in the individually heart rate-corrected QT interval (QTcNi) recorded at any of the 12 ECG time-points distributed over a 24-hour period on day 7 of treatment. Secondary endpoints included a similar analysis using the Fridericia- (QTcF) and Bazett-corrected (QTcB) intervals. An explorative analysis included quantitative assessment of T-wave morphology using the T-wave morphology composite score (MCS) to assess for differences between treatment groups and placebo on day 7 of treatment. The frequency of outliers in the QTc intervals, the pharmacokinetics of nalmefene and the tolerability of nalmefene were also assessed.

RESULTS

Nalmefene was rapidly absorbed with a time to reach maximum plasma concentration of 2.2 hours and a dose-proportionate relationship between dose administered and exposure. The largest baseline- and placebo-adjusted mean changes from baseline in the individualized QTcNi (primary endpoint) were 5.45 ms (90% CI 1.52, 9.37) and 5.57 ms (90% CI 1.62, 9.52) for nalmefene 20 and 80 mg/day, respectively, with study sensitivity confirmed by the expected largest increase in mean QTcNi of 10.15 ms (90% CI 5.67, 14.63) for moxifloxacin. Quantitative assessment using the T-wave MCS demonstrated the largest baseline- and placebo-adjusted increase in MCS to be non-significantly different from the intra-subject variability of triplicate recordings in the placebo group. No deaths or serious adverse events occurred in the study.

CONCLUSION

This thorough QT/QTc study was a negative study in accordance with the ICH E14 guideline, meaning that nalmefene has no clinically relevant effect on the QTc interval and T-wave morphology. The study predicts no concern over proarrhythmia or need for intensive QTc monitoring with the use of nalmefene in clinical practice.

Assessing QT interval prolongation and its associated risks with antipsychotics

Several antipsychotics are associated with the ventricular tachycardia torsade de pointes (TdP), which may lead to sudden cardiac death (SCD), because of their inhibition of the cardiac delayed potassium rectifier channel. This inhibition extends the repolarization process of the ventricles of the heart, illustrated as a prolongation of the QT interval on a surface ECG. SCD in individuals receiving antipsychotics has an incidence of approximately 15 cases per 10,000 years of drug exposure but the exact association with TdP remains unknown because the diagnosis of TdP is uncertain. Most patients manifesting antipsychotic-associated TdP and subsequently SCD have well established risk factors for SCD, i.e. older age, female gender, hypokalaemia and cardiovascular disease. QT interval prolongation is the most widely used surrogate marker for assessing the risk of TdP but it is considered somewhat imprecise, partly because QT interval changes are subject to measurement error. In particular, drug-induced T-wave changes (e.g. flattening of the T-wave) may complicate the measurement of the QT interval. Furthermore, the QT interval depends on the heart rate and a corrected QT (QTc) interval is often used to compensate for this. Several correction formulas have been suggested, with Bazett's formula the most widely used. However, Bazett's formula overcorrects at a heart rate above 80 beats per minute and, therefore, Fridericia's formula is considered more appropriate to use in these cases. Several other surrogate markers for TdP have been developed but none of them is clinically implemented yet and QT interval prolongation is still considered the most valid surrogate marker. Although automated QT interval determination may offer some assistance, QT interval determination is best performed by a cardiologist skilled in its measurement. A QT interval >500 ms markedly increases the risk for TdP and SCD, and should lead to discontinuation of the offending drug and, if present, correction of underlying electrolyte disturbances, particularly serum potassium and magnesium derangements. Before prescribing antipsychotics that may increase the QTc interval, the clinician should ask about family and personal history of SCD, presyncope, syncope and cardiac arrhythmias, and recommend cardiology consultation if history is positive.