Human cardiac and neuronal stem cell-derived spheroids and organoids are emerging models for drug discovery and drug safety studies. Their electrical properties are frequently investigated by means of multielectrode arrays (MEAs). However, it is difficult to establish adequate electrode contacts between planar MEAs and these round, 3D cell models. Contractions of cardiac 3D models and movement artefacts during the application of test solutions can also disrupt the recordings. As a solution, we present a microfluidics device (hereinafter referred to as SphereChip) that enables quick and stable attachment of free-floating spherical cell models such as cardiospheres, cardioids and neurospheres to conventional planar MEAs. The device reduces motion artifacts and enables complete solution exchange. It was successfully used with two different MEA designs for field potential measurements and simultaneous imaging using fluorescent probes on small cardio- and neurospheres (diameter 300 to 500 μm) and larger cardioids (800 to 900 μm). We observed concentration-dependent prolongation of action and field potentials of cardiospheres by the potassium channel (Kv1.11) inhibitors E4031 and dofetilide. In neurospheres, application of a potassium channel (Kv7.2/7.3) activator ML213 reduced spiking and bursting. We present these results as proof of concept for the microfluidics device as a means to enable organ-on-a-chip studies combining field potential measurements with simultaneous imaging on spherical cell models using planar MEAs. The method is applicable to different MEA formats and holds promise as a workable platform for drug testing and toxicity studies.

Amsacrine is an antineoplastic agent for acute lymphoblastic leukemia. It contains methanesulfonamide group -similar to hERG/IKr inhibitors like E-4031 and dofetilide-therefore may exert cardiac arrhythmias. Although amsacrine inhibits expressed hERG channels, its effects on native cardiac electrophysiology remain unclear. We investigated the effects of 1 and 10 µM amsacrine on action potentials (APs) and underlying ionic currents in isolated canine ventricular cardiomyocytes. Amsacrine reduced phase 0 parameters: maximal upstroke velocity (∼50-60%), action potential amplitude (∼15%), and peak potential (∼55%), suggesting inhibition of sodium current. Moreover, the maximal rates of phase 1 and 3 repolarizations, and plateau potentials were reduced, suggesting effects on multiple ionic currents. Despite these, AP duration (APD20-APD90) remained unaffected. AP voltage-clamp analysis revealed a complex amsacrine-sensitive current consisting of an early inward component consistent with sodium current inhibition, a second early outward component suggesting transient outward current suppression, a mid-plateau inward component likely reflecting inhibition of inward plateau currents, and a late outward component compatible with IKr inhibition. 10 µM amsacrine reduced L-type calcium, transient outward potassium and expressed NaV1.5 channel currents by 22, 38, and 10%, respectively. Native IKr was also reduced in a concentration-dependent manner (152 nM IC50 and 1.21 Hill coefficient). These findings demonstrate that amsacrine modulates multiple cardiac ion currents. The lack of AP prolongation despite IKr inhibition can be due to concomitant suppression of inward currents. As the tested concentrations overlap with therapeutic plasma levels (3-18 µM), amsacrine may carry a non-negligible risk of cardiac electrophysiological effects, particularly in susceptible patients.

Transparent conductive interfaces can enable optical pre-assessment of cardiac cell layers while remaining compatible with label-free electrophysiological recording. Here, we evaluated the integration of a monolayer graphene electrode into a capacitive recording platform for the analysis of human-induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) monolayers. hiPSC-CMs cultured on graphene sensors formed confluent, synchronously beating monolayers that could be assessed by light microscopy prior to recording. Capacitive current transients could be recorded from spontaneously beating hiPSC-CM monolayers, supporting the compatibility of transparent graphene interfaces with capacitive recordings from electrically active cardiac cell layers. Signal amplitude and waveform morphology varied across sensors, indicating that recording performance depended strongly on the cell-sensor interface, including cell attachment, monolayer integrity, and capacitive coupling at the sensing surface. A descriptive perturbation sequence using the hERG blocker dofetilide revealed changes in waveform morphology and beat timing across sequential recordings. However, the data do not allow firm attribution to a compound-specific effect and are not intended for quantitative pharmacological characterization. Overall, the results support graphene as a transparent conductive cell-sensor interface, which should be interpreted in the context of cell-substrate interactions at the sensing surface. Combining optical pre-assessment with functional capacitive readout may support integrated workflows. Further studies will be needed to differentiate material-, interface-, and recording-related contributions and to establish reliable conditions for reproducible and scalable recordings.

Arterial hypertension is a well-known risk factor for cardiac arrhythmias, while certain antihypertensive agents may also create conditions for arrhythmia occurrence. The aim of this study was to evaluate the effects of selected class III antiarrhythmic drugs on cardiac function and structure, as well as on oxidative stress status, in spontaneously hypertensive rats (SHRs). Male SHRs were treated for 4 weeks with dronedarone, amiodarone, or dofetilide. Cardiac function was assessed in vivo by echocardiography and ex vivo using the Langendorff model. Oxidative stress markers, myocardial morphology, and HSP70 and SERCA2 expression were analyzed. All drugs partially improved cardiac function in vivo, with dronedarone exerting the strongest antihypertensive effect. Ex vivo, dofetilide enhanced contractility and dronedarone reduced cardiac performance, whereas amiodarone showed intermediate effects. Oxidative stress was differentially modulated, with dofetilide and amiodarone improving antioxidant defenses, while dronedarone showed heterogeneous effects. Histologically, dofetilide preserved myocardial architecture most effectively, while amiodarone and dronedarone partially attenuated hypertensive remodeling. Treatments decreased HSP70 expression, while increasing SERCA2 expression, particularly in the dofetilide group. Class III antiarrhythmic drugs differentially affect cardiac function, redox balance, calcium handling, and myocardial remodeling in hypertension, which may contribute to their distinct antiarrhythmic and cardioprotective properties.

Our review focuses on methanesulfonamide-containing compounds, a well-characterized class of high-affinity blockers of the hERG potassium channel, which plays a critical role in cardiac repolarization by mediating the cardiac IKr. These compounds, which include notable class III antiarrhythmic drugs such as dofetilide and d-sotalol, block the hERG channel in its open state by binding within the inner vestibule. This interaction is particularly strong with some residues and the compounds form hydrogen bonds with others. This binding results in high-affinity inhibition with slow dissociation kinetics, frequently leading to drug trapping and prolonged action potential duration (APD). This can predispose patients to arrhythmias, including Torsades de Pointes. Beyond cardiac drugs, there are several non-cardiac methanesulfonamide drugs that also block the hERG channel. This causes pro-arrhythmic side effects despite their primary indications. The clinical significance of these effects, especially in patients with impaired drug elimination, is that accumulation increases the risk of arrhythmia. The objective of forthcoming research endeavors is to mitigate hERG affinity, with the aim of reducing pro-arrhythmic risks while maintaining therapeutic efficacy. This means structural modifications that seek to remove or modify the methanesulfonamide group. Machine learning also emerged as promising tool for exploring drug-protein interactions. It is evident that the methanesulfonamide moiety plays a pivotal role in the structural basis of hERG blockade. However, it should be noted that this moiety does not necessarily represent a universal pharmacophore. This observation underscores the necessity for a nuanced approach in drug development, aimed at achieving a balance between efficacy and safety.

The saga of antiarrhythmic drug (AAD) therapy reflects a field shaped by empiricism and burdened by challenges related to safety. The Singh-Vaughan-Williams classification was a timely necessity that eventually slowed pharmacological innovation by prioritizing electrophysiologic properties over arrhythmogenic mechanisms. The present, limited pharmacological armamentarium demands efforts to reassess legacy antiarrhythmics, repurpose non-antiarrhythmic agents as upstream or downstream therapy, and develop novel compounds. Flecainide, propafenone, and dronedarone have demonstrated their reliable efficacy and safety, even in patients with structural heart disease, which should allow clinicians to reduce their reliance on amiodarone. Previous concerns regarding the proarrhythmic risk of dofetilide and ibutilide are currently managed through careful patient selection and adequate QT interval monitoring. Novel targeted AADs are advancing through the development pipeline, of which etripamil and landiolol have already been approved. Other emerging drugs, such as SK channel blockers (AP30663 and AP31969), RyR2 blockers, CaMKII inhibitors, and TASK-1 blockers (doxapram), are aligned with the new paradigm of atrial fibrillation that focuses on triggers and re-entry. Once triggered, arrhythmias are perpetuated by the underlying substrate, which could be directly targeted by antifibrotic therapy. Developing concepts such as atrial cardiomyopathy allows clinicians to characterize substrate objectively, in order to assess disease severity and individualize antiarrhythmic treatment. The future of antiarrhythmic therapy will be reshaped by artificial intelligence and digital twinning, which allow precise phenotyping and a tailored approach based on individual patient profiles, complemented by rhythm monitoring through wearables.

The analysis of drug-induced alterations in the electrocardiogram (ECG) is essential in measuring cardiac safety, but manual analysis is not always accurate enough to identify subtle but important effects. This paper examines how machine learning (ML) models can be used to categorize various pharmacological treatments according to their distinct ECG patterns to establish a platform of individualized therapeutic evaluation. Using the public ECG Effects of Dofetilide, Moxifloxacin, Dofetilide+Mexiletine, Dofetilide+Lidocaine and Moxifloxacin+Diltiazem (ECGDMMLD) database, key electrophysiological features were extracted-including heart rate variability (HRV) and standard cardiac intervals (RR, PR, QT, QRS) to train and compare three different classifiers: XGBoost, Random Forest, and a Support Vector Machine (SVM). The analysis showed that tree-based ensemble techniques were very useful in this task. The XGBoost model had a better classification accuracy of 98.1%, which was closely followed by the random forest at 97.3%. Conversely, the SVM had much lower accuracy, implying that it was not as well adapted to the complexity of the high-dimensional ECG data. These results establish that ML models, particularly XGBoost, can accurately decode complex drug-induced cardiac signatures from ECG data. This work is a powerful demonstration of the proof-of-concept of automated and data-driven analytics integration into clinical processes to enhance drug safety and promote personalized medicine.

Ibutilide is a class III antiarrhythmic drug used intravenously for the chemical cardioversion of atrial fibrillation (AF) and atrial flutter (AFL). It mainly acts by blocking the rapid component (Ikr) of delayed rectifier K[+] channels, resulting in prolongation of action potential duration in the atrium. Ibutilide fumarate is a methanesulfonamide derivative that is structurally similar to sotalol without the β-adrenoreceptor blocking activity. The success rate of cardioversion of atrial flutter with ibutilide is in the range of 50-70%, whereas its efficacy for the conversion of atrial fibrillation is 30-50%. As compared to ibutilide monotherapy, coadministration with propafenone has a significantly higher success rate of AF termination. Ibutilide is also effective in pre-excited AF by reducing the risk of AF related ventricular tachycardia and thereby reducing the risk of sudden cardiac death. It is a safe drug to use for cardioversion in patients on chronic amiodarone therapy. The main side effect of dofetilide is torsade de pointes (tdp), which occurs in 4% patients, and monomorphic ventricular tachycardia, which occurs in 4.9% patients. Proadministration of magnesium reduces the risk of torsade de pointes. Patients should be monitored for at least 4 h for tdp. Targeting complex fractionated electrograms with the assistance of an ibutilide infusion during catheter ablation of persistent AF has shown mixed results. Conversion rate with an ibutilide infusion is only 30% in the presence of an enlarged left atrium (>5 cm) and 37.7% in the presence of mitral valve disease (MVD), whereas the conversion rate was 82.5% in the absence of MVD and 85% in the absence of both an enlarged left atrium and mitral valve disease (p = <0.001). Ibutilide can be used effectively in patients who are not a candidate for direct current cardioversion or who chose not to undergo electric cardioversion.