Dexmedetomidine exhibits antiarrhythmic effects on human-induced pluripotent stem cell-derived cardiomyocytes through a Na/Ca channel-mediated mechanism

Electrical storm induced by premature ventricular beat with extremely short coupling interval in a patient with long QT syndrome type 3

Here we report the case of a 10-year-old boy with long QT syndrome type 3 (LQT3) who developed refractory torsade de pointes (TdP) associated with ventricular arrhythmia with a short coupling time (VASCT). After implantable cardioverter-defibrillator replacement, an electrical storm occurred, which was irresponsive to the ventricular pacing as high as 120 bpm. Close inspection of the intracardiac potential revealed TdP associated with VASCT. Dexmedetomidine and verapamil were effective in controlling TdP, which allowed management with slower ventricular pace. Our case highlights the importance of focusing on ventricular arrhythmias particularly those with short coupling interval, in LQT3 with refractory TdP. (99 words).

Effects and mechanisms of dexmedetomidine preconditioning on isoproterenol-induced ventricular arrhythmias

Dexmedetomidine (DEX) is commonly used in clinical practice because of its sedative, analgesic, antisympathetic, hemodynamic stabilization and antianxiety effects. Previous clinical studies have demonstrated that DEX plays a role in both the prevention and treatment of perioperative arrhythmias. However, the precise mechanisms underlying the effects of DEX remain unclear. Furthermore, few studies have examined the effect of DEX on cardiac electrophysiology. ECG recording was performed in vivo and ex vivo on C57 mice. Simultaneous recording of membrane voltage (Vm) and [Ca2+]i changes was achieved with dual-dye optical mapping, in which voltage- and Ca2+-sensitive dyes are employed. Simultaneous programmed electrical stimulation was used to pacing and induce arrhythmias. Simulating catecholamine-induced arrhythmias with isoprotereno (ISO) and preconditioning with DEX to investigate the antiarrhythmic effects of DEX. Our findings demonstrated that ISO increased the incidence of ventricular tachycardia or ventricular fibrillation in mice during rapid pacing stimulation. DEX preconditioning reduced the incidence of ISO-induced ventricular arrhythmias. Optical mapping with simultaneous recordings of dual dyes (Vm dye and intracellular Ca2+ dye) revealed that DEX pretreatment attenuated the ISO-induced shortening of action potential duration (APD), calcium transient duration (CaTD), and time-to-peak (TTP) of calcium transients, as well as the ISO-induced increase in repolarization heterogeneity. DEX also slowed the conduction velocity. More importantly, DEX preconditioning significantly reduced the calcium transient alternans ratio at 80-ms, 70-ms, and 60-ms pacing cycles. These findings suggest that DEX preconditioning can reduce the incidence of ventricular arrhythmias induced by acute stress simulated by ISO. Prolongation of action potential duration and calcium transient duration and the maintenance of intracellular calcium homeostasis may be the electrophysiological mechanisms involved.

Selected 2023 Highlights in Congenital Cardiac Anesthesia

This article reviews the highlights of pertinent literature of interest to the congenital cardiac anesthesiologist published in 2023. After a search of the US National Library of Medicine PubMed database, several topics emerged where significant contributions were made in 2023. The authors of this article considered the following topics noteworthy to be included in this review: (1) advancements in percutaneous mechanical support in children with congenital heart disease, (2) children with pulmonary hypertension undergoing surgery for congenital heart disease, (3) dexmedetomidine in pediatric cardiac surgery, and (4) recommendations for pediatric heart surgery in the United States: Implications for pediatric cardiac anesthesia.

Dexmedetomidine and Perioperative Arrhythmias

The highly selective α2-adrenoceptor agonist dexmedetomidine is a commonly used sedative drug for patients undergoing anesthesia and intensive care treatment. Several studies have indicated that dexmedetomidine may have a potential role in preventing and treating perioperative tachyarrhythmias. However, the specific effect and mechanism of action of dexmedetomidine in this context remain unclear. Dexmedetomidine is known to regulate the electrophysiologic function of the myocardium by inhibiting the function of the sinus node and atrioventricular node, as well as affecting myocardial repolarization. This paper aims to provide a theoretical basis for the prevention and treatment of perioperative arrhythmias by summarizing the effects of dexmedetomidine on myocardial electrophysiologic function and its impact on different types of arrhythmias.

Recent advances in pluripotent stem cell-derived cardiac organoids and heart-on-chip applications for studying anti-cancer drug-induced cardiotoxicity

Cardiovascular disease (CVD) caused by anti-cancer drug-induced cardiotoxicity is now the second leading cause of mortality among cancer survivors. It is necessary to establish efficient in vitro models for early predicting the potential cardiotoxicity of anti-cancer drugs, as well as for screening drugs that would alleviate cardiotoxicity during and post treatment. Human induced pluripotent stem cells (hiPSCs) have opened up new avenues in cardio-oncology. With the breakthrough of tissue engineering technology, a variety of hiPSC-derived cardiac microtissues or organoids have been recently reported, which have shown enormous potential in studying cardiotoxicity. Moreover, using hiPSC-derived heart-on-chip for studying cardiotoxicity has provided novel insights into the underlying mechanisms. Herein, we summarize different types of anti-cancer drug-induced cardiotoxicities and present an extensive overview on the applications of hiPSC-derived cardiac microtissues, cardiac organoids, and heart-on-chips in cardiotoxicity. Finally, we highlight clinical and translational challenges around hiPSC-derived cardiac microtissues/organoids/heart-on chips and their applications in anti-cancer drug-induced cardiotoxicity. • Anti-cancer drug-induced cardiotoxicities represent pressing challenges for cancer treatments, and cardiovascular disease is the second leading cause of mortality among cancer survivors. • Newly reported in vitro models such as hiPSC-derived cardiac microtissues/organoids/chips show enormous potential for studying cardio-oncology. • Emerging evidence supports that hiPSC-derived cardiac organoids and heart-on-chip are promising in vitro platforms for predicting and minimizing anti-cancer drug-induced cardiotoxicity.

Effects of dexmedetomidine on cardiac electrophysiology in patients undergoing general anesthesia during perioperative period: a randomized controlled trial

Background

Dexmedetomidine has controversial influence on cardiac electrophysiology. The aim of this study was to explore the effects of dexmedetomidine on perioperative cardiac electrophysiology in patients undergoing general anesthesia.

Methods

Eighty-one patients were randomly divided into four groups: groups D₁, D₂, D₃ receiving dexmedetomidine 1, 1, 0.5 μg/kg over 10 min and 1, 0.5, 0.5 μg/kg/h continuous infusion respectively, and control group (group C) receiving normal saline. Twelve-lead electrocardiograms were recorded at the time before dexmedetomidine/normal saline infusion (T₁), loading dose finish (T₂), surgery ending (T₆), 1 h (T₇) after entering PACU, 24 h (T₈), 48 h (T₉), 72 h (T₁₀) and 1 month (T₁₁) postoperatively. Cardiac circulation efficiency (CCE) were also recorded.

Results

Compared with group C, QTc were significantly increased at T₂ in groups D₁ and D₂ while decreased at T₇ and T₈ in group D₃ (P < 0.05), iCEB were decreased at T₈ (P < 0.05). Compared with group D₁, QTc at T₂, T₆, T₇, T₉ and T₁₀ and iCEB at T₈ were decreased, and CCE at T₂-T₄ were increased in group D₃ significantly (P < 0.05). Compared with group D₂, QTc at T₂ and iCEB at T₈ were decreased and CCE at T₂ and T₃ were increased in group D₃ significantly (P < 0.05).

Conclusions

Dexmedetomidine at a loading dose of 0.5 μg/kg and a maintenance dose of 0.5 μg/kg/h can maintain stability of cardiac electrophysiology during perioperative period and has no significant adverse effects on CCE.

Trial registration

ClinicalTrials.gov NCT04577430 (Date of registration: 06/10/2020).

Dexmedetomidine Reduces Incidences of Ventricular Arrhythmias in Adult Patients: A Meta-Analysis

Purpose

To assess the antiarrhythmic properties of dexmedetomidine in patients in the intensive care unit.

Methods

A literature review was conducted with Ovid MEDLINE (R), Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Embase, and Scopus. Study Selection. Randomized controlled trials were included, examining the incidence of ventricular arrhythmias, ventricular tachycardia, or ventricular fibrillation with dexmedetomidine compared to placebo or an alternative sedative agent. For each publication that met the selection criteria, the patient demographics, incidence of arrhythmias, mortality, and adverse events were collected. Data extraction was carried out by two authors independently.

Results

We identified 6 out of 126 studies that met the selection criteria for our meta-analysis, all of which focused on the perioperative cardiac surgery period. Patients receiving dexmedetomidine demonstrated a significant reduction of the overall incidence of ventricular arrhythmias (RR 0.35, 95% CI 0.16, 0.76). In particular, dexmedetomidine significantly decreased the risk of ventricular tachycardia compared with control (RR 0.25, 95% CI 0.08, 0.80, I² 0%). Regarding adverse events, dexmedetomidine significantly increased the frequency of bradycardia (RR 2.78 95% CI 2.00, 3.87). However, there was no significant difference in mortality (RR 0.59 95% CI 0.12, 3.02).

Conclusion

From this meta-analysis, we report a decreased incidence of ventricular tachycardia with dexmedetomidine in critically ill patients. This result favors the use of dexmedetomidine for its antiarrhythmic properties.

Safe electrophysiologic profile of dexmedetomidine in different experimental arrhythmia models

Previous studies suggest an impact of dexmedetomidine on cardiac electrophysiology. However, experimental data is sparse. Therefore, purpose of this study was to investigate the influence of dexmedetomidine on different experimental models of proarrhythmia. 50 rabbit hearts were explanted and retrogradely perfused. The first group (n = 12) was treated with dexmedetomidine in ascending concentrations (3, 5 and 10 µM). Dexmedetomidine did not substantially alter action potential duration (APD) but reduced spatial dispersion of repolarization (SDR) and rendered the action potentials rectangular, resulting in no proarrhythmia. In further 12 hearts, erythromycin (300 µM) was administered to simulate long-QT-syndrome-2 (LQT2). Additional treatment with dexmedetomidine reduced SDR, thereby suppressing torsade de pointes. In the third group (n = 14), 0.5 µM veratridine was added to reduce the repolarization reserve. Further administration of dexmedetomidine did not influence APD, SDR or the occurrence of arrhythmias. In the last group (n = 12), a combination of acetylcholine (1 µM) and isoproterenol (1 µM) was used to facilitate atrial fibrillation. Additional treatment with dexmedetomidine prolonged the atrial APD but did not reduce AF episodes. In this study, dexmedetomidine did not significantly alter cardiac repolarization duration and was not proarrhythmic in different models of ventricular and atrial arrhythmias. Of note, dexmedetomidine might be antiarrhythmic in acquired LQT2 by reducing SDR.

Yohimbine Directly Induces Cardiotoxicity on Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Yohimbine is a highly selective and potent α₂-adrenoceptor antagonist, which is usually treated as an adjunction for impotence, as well for weight loss and natural bodybuilding aids. However, it was recently reported that Yohimbine causes myocardial injury and controversial results were reported in the setting of cardiac diseases. Here, we used human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) as a model system to explore electrophysiologic characterization after exposure to Yohimbine. HiPSC-CMs were differentiated by employment of inhibitory Wnt compounds. For analysis of electrophysiological properties, conventional whole-cell patch-clamp recording was used. Specifically, spontaneous action potentials, pacemaker currents (I_f), sodium (Na⁺) channel (I_Na), and calcium (Ca⁺⁺) channel currents (I_Ca) were assessed in hiPSC-CMs after exposure to Yohimbine. HiPSC-CMs expressed sarcomeric-α-actinin and MLC2V proteins, as well as exhibited ventricular-like spontaneous action potential waveform. Yohimbine inhibited frequency of hiPSC-CMs spontaneous action potentials and significantly prolonged action potential duration in a dose-dependent manner. In addition, rest potential, threshold potential, amplitude, and maximal diastolic potential were decreased, whereas APD₅₀/APD₉₀ was prolonged. Yohimbine inhibited the amplitude of I_Na in low doses (IC₅₀ = 14.2 μM, n = 5) and inhibited I_Ca in high doses (IC₅₀ = 139.7 μM, n = 5). Whereas Yohimbine did not affect the activation curves, treatment resulted in left shifts in inactivation curves of both Na⁺ and Ca⁺⁺ channels. Here, we show that Yohimbine induces direct cardiotoxic effects on spontaneous action potentials of I_Na and I_Ca in hiPSC-CMs. Importantly, these effects were not mediated by α₂-adrenoceptor signaling. Our results strongly suggest that Yohimbine directly and negatively affects electrophysiological properties of human cardiomyocytes. These findings are highly relevant for potential application of Yohimbine in patients with atrioventricular conduction disorder.