Mechanistic Insights Into Inflammation-Induced Arrhythmias: A Simulation Study

COVID-19 and Cardiac Arrhythmias: Lesson Learned and Dilemmas

Over the last few years, COVID-19 has attracted medical attention both in terms of healthcare system reorganization and research. Among the different cardiovascular complications of the SARS-CoV-2 infection, cardiac arrhythmias represent an important clinical manifestation requiring proper therapy both in the acute and post-acute phase. The multiparametric in-hospital monitoring of COVID-19 patients frequently detects new-onset or recurrent cardiac arrhythmias. As many patients are monitored remotely from cardiology departments, this setting calls for proper arrhythmia interpretation and management, especially in critically ill patients in the intensive care unit. From this perspective, the possible pathophysiologic mechanisms and the main clinical manifestations of brady- and tachyarrhythmias in COVID-19 patients are briefly presented. The progressively increasing body of evidence on pathophysiology helps to identify the reversible causes of arrhythmias, better clarify the setting in which they occur, and establish their impact on prognosis, which are of paramount importance to orient decision making. Despite the accumulating knowledge on this disease, some dilemmas in the management of these patients may remain, such as the need to implant in the acute or post-acute phase a permanent pacemaker or cardioverter/defibrillation in patients presenting with brady- or tachyarrhythmias and lifelong oral anticoagulation in new-onset atrial fibrillation detected during SARS-CoV-2 infection.

The predictive value of pan-immune inflammatory index for early recurrence of atrial fibrillation after cryoablation

OBJECTIVE

The pan-immune inflammatory (PIV) index holds prognostic value for cardiovascular diseases. This study aimed to investigate the predictive value of the PIV index regarding recurrence of atrial fibrillation (AF) after cryoballoon ablation (CBA).

METHODS

The study included 307 patients with AF. Four inflammatory markers, namely, the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune inflammation (SII) index, and PIV index, were used as indicators. COX regression analysis was conducted to evaluate the predictive value of AF recurrence after CBA. A receiver operating characteristic (ROC) curve was plotted, and the area under the curve (AUC) was calculated to evaluate the discriminative power of the indicators.

RESULT

The PIV index [94.9 (168.9,504.9) vs. 143.2 (98.2,210.6), P < 0.01] and SII index [366.3 (256.6,491.9) vs. 569.9 (658.1,438.4), P < 0.01] were significantly higher in the recurrence group. Univariable COX regression analysis showed that these four indices, persistent AF, and left atrial diameter (LAD) were all associated with AF recurrence. In multivariable regression analysis, the PIV index, persistent AF, and LAD (all P < 0.05) were independent predictors of postoperative AF recurrence. The ROC curve analysis showed that the PIV index had a higher predictive value for AF recurrence (AUC = 0.768, P < 0.01, 95% CI: 0.696-0.840) than the SII index and NLR. Kaplan-Meier analysis showed that patients with a PIV index > 260.7 had a higher recurrence rate at 1-year follow-up (P < 0.01). Subgroup analysis indicated that PIV had a predictive value in patients with different types of AF.

CONCLUSION

PIV index may be a potential biomarker for predicting relapse in patients with AF after CBA.

Mesenchymal Stem Cells Increase Resistance Against Ventricular Arrhythmias Provoked in Rats with Myocardial Infarction

This study evaluated the role of the mesenchymal stem cells derived from adipose tissue (MSCs) in provoked ventricular arrhythmias (VAs) in animals with myocardial infarction (MI). The experimental groups were: sham, subjected to sham surgery and intramyocardial saline injection; MIV, infarcted rats subjected to intramyocardial saline injection; MI + MSCs, infarcted rats subjected to intramyocardial MSCs injection. Injections were performed two days after infarction and the arrhythmogenic inducibility experiment was performed the next day. Only 35% of the MI + MSCs group developed VAs, while the one in the MIV group was 65%. The proportion of nonsustained ventricular tachycardia, sustained tachycardia, and ventricular fibrillation was similar between the infarcted groups, but MSCs animals had shorter duration of nonsustained ventricular tachycardia. However, MSCs increased connexin 43 content in the remote area, even above the levels found in the sham group. MSCs prevented the increase of IL-1β in the different areas of the myocardium. There was higher carbonylation and content of 4-hydroxynonenal (4-HNE, a marker of lipoperoxidation) in the myocardium of infarcted rats, but MSCs attenuated the increase of 4-HNE in the infarcted area. In conclusion, MSCs have a protective effect against the development of arrhythmias, but do not imply a significant benefit for animals that have developed VAs. It is possible to think that the cardioprotection of MSCs involves anti-inflammatory/oxidative actions and improvement in the formation of communicating junctions.Graphical abstract.

The causal relationship between sarcopenia-related traits and ECG indices - A mendelian randomization study

BACKGROUND

Sarcopenia is a common geriatric condition closely associated with cardiovascular diseases and other health issues. This study aims to investigate the causal relationship between sarcopenia-related traits and electrocardiogram(ECG) indices.

METHODS

We conducted a comprehensive analysis utilizing summary data from genome-wide association studies (GWAS) associated with sarcopenia-related traits, including hand grip strength, lean body mass, and walking pace. ECG indices included PR interval, PP interval, ST duration, QRS duration and T wave duration. The primary analytical method employed was the inverse variance-weighted method (IVW).

RESULTS

According to our study findings, we identified a significant association between sarcopenia-related traits and ECG indices. Specifically, we observed a positive correlation between increased muscle mass and certain ECG indices. For instance, increased limb muscle mass (including left arm, right arm, left leg, and right leg) was associated with prolonged PR interval and QRS duration. This suggests that enhancing muscle mass may impact the timing of cardiac electrical activity. Additionally, increased whole-body fat-free mass showed similar associations with cardiac electrical activity.

CONCLUSION

Sarcopenia-related traits have a unidirectional causal relationship with ECG indices, indicating that sarcopenia affects cardiac electrical activity.

A dynamic online nomogram predicting post-traumatic arrhythmias: A retrospective cohort study

BACKGROUND

A nomogram is a visualized clinical prediction models, which offer a scientific basis for clinical decision-making. There is a lack of reports on its use in predicting the risk of arrhythmias in trauma patients. This study aims to develop and validate a straightforward nomogram for predicting the risk of arrhythmias in trauma patients.

METHODS

We retrospectively collected clinical data from 1119 acute trauma patients who were admitted to the Advanced Trauma Center of the Affiliated Hospital of Zunyi Medical University between January 2016 and May 2022. Data recorded included intra-hospital arrhythmia, ICU stay, and total hospitalization duration. Patients were classified into arrhythmia and non-arrhythmia groups. Data was summarized according to the occurrence and prognosis of post-traumatic arrhythmias, and randomly allocated into a training and validation sets at a ratio of 7:3. The nomogram was developed according to independent risk factors identified in the training set. Finally, the predictive performance of the nomogram model was validated.

RESULTS

Arrhythmias were observed in 326 (29.1%) of the 1119 patients. Compared to the non-arrhythmia group, patients with arrhythmias had longer ICU and hospital stays and higher in-hospital mortality rates. Significant factors associated with post-traumatic arrhythmias included cardiovascular disease, catecholamine use, glasgow coma scale (GCS) score, abdominal abbreviated injury scale (AIS) score, injury severity score (ISS), blood glucose (GLU) levels, and international normalized ratio (INR). The area under the receiver operating characteristic curve (AUC) values for both the training and validation sets exceeded 0.7, indicating strong discriminatory power. The calibration curve showed good alignment between the predicted and actual probabilities of arrhythmias. Decision curve analysis (DCA) indicated a high net benefit for the model in predicting arrhythmias. The Hosmer-Lemeshow goodness-of-fit test confirmed the model's good fit.

CONCLUSION

The nomogram developed in this study is a valuable tool for accurately predicting the risk of post-traumatic arrhythmias, offering a novel approach for physicians to tailor risk assessments to individual patients.

Stretch of the papillary insertion triggers reentrant arrhythmia: an in silico patient study

Background

The electrophysiological mechanism connecting mitral valve prolapse (MVP), premature ventricular complexes and life-threatening ventricular arrhythmia is unknown. A common hypothesis is that stretch activated channels (SACs) play a significant role. SACs can trigger depolarizations or shorten repolarization times in response to myocardial stretch. Through these mechanisms, pathological traction of the papillary muscle (PM), as has been observed in patients with MVP, may induce irregular electrical activity and result in reentrant arrhythmia.

Methods

Based on a patient with MVP and mitral annulus disjunction, we modeled the effect of excessive PM traction in a detailed medical image-derived ventricular model by activating SACs in the PM insertion region. By systematically varying the onset of SAC activation following sinus pacing, we identified vulnerability windows for reentry with 1 ms resolution. We explored how reentry was affected by the SAC reversal potential ( E SAC ) and the size of the region with simulated stretch (SAC region). Finally, the effect of global or focal fibrosis, modeled as reduction in tissue conductivity or mesh splitting (fibrotic microstructure), was investigated.

Results

In models with healthy tissue or fibrosis modeled solely as CV slowing, we observed two vulnerable periods of reentry: ForE SAC of -10 and -30 mV, SAC activated during the T-wave could cause depolarization of the SAC region which lead to reentry. ForE SAC of -40 and -70 mV, SAC activated during the QRS complex could result in early repolarization of the SAC region and subsequent reentry. In models with fibrotic microstructure in the SAC region, we observed micro-reentries and a larger variability in which times of SAC activation triggered reentry. In these models, 86% of reentries were triggered during the QRS complex or T-wave. We only observed reentry for sufficiently large SAC regions ( > = 8 mm radius in models with healthy tissue).

Conclusion

Stretch of the PM insertion region following sinus activation may initiate ventricular reentry in patients with MVP, with or without fibrosis. Depending on the SAC reversal potential and timing of stretch, reentry may be triggered by ectopy due to SAC-induced depolarizations or by early repolarization within the SAC region.

What Do We Know So Far About Ventricular Arrhythmias and Sudden Cardiac Death Prediction in the Mitral Valve Prolapse Population? Could Biomarkers Help Us Predict Their Occurrence?

PURPOSE OF THE REVIEW

To summarize currently available data on the topic of mitral valve prolapse (MVP) and its correlation to the occurrence of atrial and ventricular arrhythmias. To assess the prognostic value of several diagnostic methods such as transthoracic echocardiography, transesophageal echocardiography, cardiac magnetic resonance, cardiac computed tomography, electrocardiography, and electrophysiology concerning arrhythmic episodes. To explore intra and extracellular biochemistry of the cardiovascular system and its biomarkers as diagnostic tools to predict rhythm disturbances in the MVP population.

RECENT FINDINGS

MVP is a common and mainly benign valvular disorder. It affects 2-3% of the general population. MVP is a heterogeneous and highly variable phenomenon with three structural phenotypes: myxomatous degeneration, fibroelastic deficiency, and forme fruste. Exercise intolerance, supraventricular tachycardia, and chest discomfort are the symptoms that are often paired with psychosomatic components. Though MVP is thought to be benign, the association between isolated MVP without mitral regurgitation (MR) or left ventricle dysfunction, with ventricular arrhythmia (VA) and sudden cardiac death (SCD) has been observed. The incidence of SCD in the MVP population is around 0.6% per year, which is 6 times higher than the occurrence of SCD in the general population. Often asymptomatic MVP population poses a challenge to screen for VA and prevent SCD. Therefore, it is crucial to carefully assess the risk of VA and SCD in patients with MVP with the use of various tools such as diagnostic imaging and biochemical and genetic screening.

Targeting NLRP3 signaling reduces myocarditis-induced arrhythmogenesis and cardiac remodeling

BACKGROUND

Myocarditis substantially increases the risk of ventricular arrhythmia. Approximately 30% of all ventricular arrhythmia cases in patients with myocarditis originate from the right ventricular outflow tract (RVOT). However, the role of NLRP3 signaling in RVOT arrhythmogenesis remains unclear.

METHODS

Rats with myosin peptide-induced myocarditis (experimental group) were treated with an NLRP3 inhibitor (MCC950; 10 mg/kg, daily for 14 days) or left untreated. Then, they were subjected to electrocardiography and echocardiography. Ventricular tissue samples were collected from each rat's RVOT, right ventricular apex (RVA), and left ventricle (LV) and examined through conventional microelectrode and histopathologic analyses. In addition, whole-cell patch-clamp recording, confocal fluorescence microscopy, and Western blotting were performed to evaluate ionic currents, intracellular Ca2+ transients, and Ca2+-modulated protein expression in individual myocytes isolated from the RVOTs.

RESULTS

The LV ejection fraction was lower and premature ventricular contraction frequency was higher in the experimental group than in the control group (rats not exposed to myosin peptide). Myocarditis increased the infiltration of inflammatory cells into cardiac tissue and upregulated the expression of NLRP3; these observations were more prominent in the RVOT and RVA than in the LV. Furthermore, experimental rats treated with MCC950 (treatment group) improved their LV ejection fraction and reduced the frequency of premature ventricular contraction. Histopathological analysis revealed higher incidence of abnormal automaticity and pacing-induced ventricular tachycardia in the RVOTs of the experimental group than in those of the control and treatment groups. However, the incidences of these conditions in the RVA and LV were similar across the groups. The RVOT myocytes of the experimental group exhibited lower Ca2+ levels in the sarcoplasmic reticulum, smaller intracellular Ca2+ transients, lower L-type Ca2+ currents, larger late Na+ currents, larger Na+-Ca2+ exchanger currents, higher reactive oxygen species levels, and higher Ca2+/calmodulin-dependent protein kinase II levels than did those of the control and treatment groups.

CONCLUSION

Myocarditis may increase the rate of RVOT arrhythmogenesis, possibly through electrical and structural remodeling. These changes may be mitigated by inhibiting NLRP3 signaling.

Computational analysis of long QT syndrome type 2 and the therapeutic effects of KCNQ1 antibodies

Objective

Long QT interval syndrome (LQTS) is a highly dangerous cardiac disease that can lead to sudden cardiac death; however, its underlying mechanism remains largely unknown. This study is conceived to investigate the impact of two general genotypes of LQTS type 2, and also the therapeutic effects of an emerging immunology-based treatment named KCNQ1 antibody.

Methods

A multiscale virtual heart is developed, which contains multiple biological levels ranging from ion channels to a three-dimensional cardiac structure with realistic geometry. Critical biomarkers at different biological levels are monitored to investigate the remodeling of cardiac electrophysiology induced by mutations.

Results

Simulations revealed multiple important mechanisms that are hard to capture via conventional clinical techniques, including the augmented dispersion of repolarization, the increased vulnerability to arrhythmias, the impaired adaptability in tissue to high heart rates, and so on. An emerging KCNQ1 antibody-based therapy could rescue the prolonged QT interval but did not reduce the vulnerable window.

Conclusions

Tiny molecular alterations can lead to cardiac electrophysiological remodeling at multiple biological levels, which in turn contributes to higher susceptibility to lethal arrhythmias in long QT syndrome type 2 patients. The KCNQ1 antibody-based therapy has proarrhythmic risks notwithstanding its QT-rescuing effects.

In silico mechanisms of arsenic trioxide-induced cardiotoxicity

It has been found that arsenic trioxide (ATO) is effective in treating acute promyelocytic leukemia (APL). However, long QT syndrome was reported in patients receiving therapy using ATO, which even led to sudden cardiac death. The underlying mechanisms of ATO-induced cardiotoxicity have been investigated in some biological experiments, showing that ATO affects human ether-à-go-go-related gene (hERG) channels, coding rapid delayed rectifier potassium current (I _Kr ), as well as L-type calcium (I _CaL ) channels. Nevertheless, the mechanism by which these channel reconstitutions induced the arrhythmia in ventricular tissue remains unsolved. In this study, a mathematical model was developed to simulate the effect of ATO on ventricular electrical excitation at cellular and tissue levels by considering ATO's effects on I _Kr and I _CaL . The ATO-dose-dependent pore block model was incorporated into the I _Kr model, and the enhanced degree of ATO to I _CaL was based on experimental data. Simulation results indicated that ATO extended the action potential duration of three types of ventricular myocytes (VMs), including endocardial cells (ENDO), midmyocardial cells (MCELL), and epicardial cells (EPI), and exacerbated the heterogeneity among them. ATO could also induce alternans in all three kinds of VMs. In a cable model of the intramural ventricular strand, the effects of ATO are reflected in a prolonged QT interval of simulated pseudo-ECG and a wide vulnerable window, thus increasing the possibility of spiral wave formation in ventricular tissue. In addition to showing that ATO prolonged QT, we revealed that the heterogeneity caused by ATO is also an essential hazard factor. Based on this, a pharmacological intervention of ATO toxicity by resveratrol was undertaken. This study provides a further understanding of ATO-induced cardiotoxicity, which may help to improve the treatment for APL patients.