J wave syndromes as a cause of malignant cardiac arrhythmias

A Matlab Toolbox for cardiac electrophysiology simulations on patient-specific geometries

In this paper, we present CardioMat, a Matlab toolbox for cardiac electrophysiology simulation based on patient-specific anatomies. The strength of CardioMat is the easy and fast construction of electrophysiology cardiac digital twins from segmented anatomical images in a general-purpose software such as Matlab. CardioMat implements a quasi-automatic pipeline that guides the user toward the construction of anatomically detailed cardiac electrophysiology models. Importantly, the CardioMat framework includes the generation of physiologically plausible fiber orientation and Purkinje networks. The main novelty of our framework is its ability to handle voxel-based geometries as produced by segmentation procedures directly, without the need for an unstructured mesh. Indeed, the CardioMat monodomain solver uses a smoothed boundary approach and runs completely on GPU for fast simulations. We employed CardioMat in different application scenarios to show its potentialities and provide preliminary assessment of the feasibility, diagnostic performance, and accuracy of the toolbox. In particular, we showed that CardioMat simulations derived from post-infarction patients hold high sensitivity, specificity, predictive value, and accuracy for localization of deceleration zones in sinus rhythm.

Quelling the Storm: A Review of the Management of Electrical Storm

Heightened sympathetic input to the myocardium potentiates cardiac electrical instability and may herald an electrical storm. An electrical storm is characterized by 3 or more episodes of ventricular tachycardia, ventricular fibrillation, or appropriate internal cardiac defibrillator shocks within 24 hours. Management of electrical storms is resource-intensive and inevitably requires careful coordination between multiple subspecialties. Anesthesiologists have an important role in acute, subacute, and long-term management. Identifying the phase of an electrical storm and understanding the characteristics of each morphology may help the anesthesiologist anticipate the management approach. In the acute phase, management of an electrical storm is aimed at providing advanced cardiac life support and identifying reversible causes. After initial stabilization, subacute management focuses on dampening the sympathetic surge with sedation, thoracic epidural, or stellate ganglion blockade. Definitive long-term management with surgical sympathectomy or catheter ablation also may be warranted. Our objective is to provide an overview of electrical storms and the anesthesiologist's role in management.

Sudden Cardiac Death Risk Stratification of the Early Repolarization Syndrome: An Updated Review of the Literature

PURPOSE OF REVIEW

Early repolarization syndrome (ERS), once thought to be innocuous, has now been shown to be responsible for ventricular arrythmias and sudden cardiac death occurrence. This review will help the clinician to identify the patients who are most at risk for arrhythmias, so that they can adopt a preventive or secondary treatment approach, either of which is still poorly defined.

RECENT FINDINGS

Patients at high risk are found to be particularly young men, with a personal or family history of syncope or sudden death, who have an inferolateral ER on the electrocardiogram, more elevated J-point, longer J-wave duration and wider J angle, a horizontal or descending ST segment, lower T/R ratio, and small and/or inverted waves. The association with a structural heart disease or another channelopathy potentiates this arrhythmic risk. Taken together, these parameters allow prediction of the malignancy of ER pattern with a certain reliability. Further research is however needed to develop concrete risk stratification algorithms and the therapeutic strategies taken in function of it.

Cardiac Morphofunctional Characteristics of Individuals with Early Repolarization Pattern: A Literature Review

The early repolarization pattern (ERP) is an electrocardiographic phenomenon characterized by the appearance of a distinct J-wave or J-point elevation at the terminal part of the QRS complex. ERP is associated with an increased risk of ventricular arrhythmias in susceptible individuals. The cardiac morphofunctional parameters in subjects with ERP have been characterized mainly by imaging techniques, which suggests that certain changes could be identified in the background of the electrical pathomechanism: however, in this regard, current data are often contradictory or insufficiently detailed. For clarification, a more comprehensive cardiac imaging evaluation of a large patient population is necessary. This review summarizes and analyses the data from the literature related to cardiac morphofunctional characteristics in individuals with ERP.

Electrocardiographic features in SCN5A mutation-positive patients with Brugada and early repolarization syndromes: a systematic review and meta-analysis

Background

Early repolarization syndrome (ERS) and Brugada syndrome (BrS) are both J-wave syndromes. Both can involve mutations in the SCN5A gene but may exhibit distinct electrocardiographic (ECG) differences. The aim of this systematic review and meta-analysis is to investigate possible differences in ECG markers between SCN5A-positive patients with ERS and BrS.

Methods

PubMed and Embase were searched from their inception to 20 October 2021 for human studies containing the search terms “SCN5A” and “variant” and “early repolarization” or “Brugada”, with no language restrictions. Continuous variables were expressed as mean±standard deviation. PR interval, QRS duration, QTc and heart rate from the included studies were pooled to calculate a mean for each variable amongst BrS and ERS patients. A two-tailed Student’s t test was then performed to for comparisons.

Results

A total of 328 studies were identified. After full-text screening, 12 studies met our inclusion criteria and were included in this present study. One hundred and four ERS patients (mean age 30.86±14.45) and 2000 BrS patients (mean age 36.17±11.39) were studied. Our meta-analysis found that ERS patients had shorter QRS duration (90.40±9.97 vs. 114.79±20.10, P = 0.0001) and shorter corrected QT intervals (QTc) with borderline significance (393.63±40.04 vs. 416.82±37.43, P = 0.052). By contrast, no significant differences in baseline heart rate (65.15±18.78 vs. 76.06±18.78, P = 0.068) or PR intervals (197.40±34.69 vs. 191.88±35.08, P = 0.621) were observed between ERS and BrS patients.

Conclusion

BrS patients with positive SCN5A mutations exhibited prolonged QRS, indicating conduction abnormalities, whereas ERS patients with positive SCN5A mutations showed normal QRS. By contrast, whilst QTc intervals were longer in BrS than in ERS SCN5A positive patients, they were within normal limits. Further studies are needed to examine the implications of these findings for arrhythmic risk stratification.

Predictive effect of J waves on cardiac compression and clinical prognosis of esophageal tumors: a retrospective study

Background

The J wave syndromes (JWS) could be observed in patients with mediastinal tumors, though few studies have verified the statistical correlation between J waves and cardiac compression by tumors. This study aimed to investigate the relationship between J waves and cardiac compression by esophageal tumor and to compare the prediction of J waves on clinical prognosis with that of cardiac compression by esophageal tumor.

Methods

We enrolled 273 patients (228 males, 45 females; mean 63.8±7.5 years) with esophageal tumors admitted to Shanghai Chest Hospital between August 2016 and November 2020. The J wave was defined as a J-point elevation of ≥0.1 mV in a 12-lead electrocardiogram (ECG) and classified into multiple types. Chest computed tomography (CT) was reviewed to clarify the anatomical relationship between the heart and the esophageal tumor. The prognosis of severe cardiac events and survival status were followed up through medical history, examination records and telephone records.

Results

J waves were present in 141 patients among all 273 cases. The sensitivity and specificity of cardiac compression by the tumor for J waves were 78.1% and 67.3%, respectively. The odds ratio (OR) of cardiac compression by the tumor to J waves was 7.33 [95% confidence interval (CI): 4.21-12.74; P<0.001]. The Kappa coefficient between J waves and cardiac compression was 0.44±0.05. The significance association between J waves and cardiac compression was independent from other clinical variables (P<0.001). Decreased J wave amplitude was correlated with the disappearance of cardiac compression during follow-up (P=0.03). Patients with J waves had a higher risk of severe cardiac events than those without J waves (OR =2.84, 95% CI: 1.22-6.63; P=0.01). During the follow-up period, we found that the presence of J waves [hazard ratio (HR) =2.28; 95% CI: 1.35-3.84; P=0.002] and cardiac compression by the tumor (HR =2.51; 95% CI: 1.51-4.17; P<0.001) were both negatively correlated with the survival time of patients.

Conclusions

The presence of J waves could be used as an effective mean to predict the mechanical impact of esophageal tumor on the heart, and played an important role in predicting the survival of patients.

Electrocardiographic Findings, Arrhythmias, and Left Ventricular Involvement in Familial ST-Depression Syndrome

BACKGROUND

Familial ST-depression syndrome is an inherited disease characterized by persistent, nonischemic ST-deviations, and risk of arrhythmias and heart failure. We aimed at further characterizing the ECG, arrhythmias, and structural characteristics associated with this novel syndrome.

METHODS

Retrospective analysis of data from consecutive families with familial ST-depression Syndrome in Denmark. ECG features, prevalence and type of arrhythmias, occurrence of systolic dysfunction, and medium-term outcome were analyzed.

RESULTS

Forty affected individuals (43% men; mean age at diagnosis 49.1 years) from 14 apparently unrelated families with ≥2 affected members were included. Autosomal dominant inheritance was observed in all families. The ECG phenotype seemed to develop in prepuberty and the ST-deviations were persistent and most pronounced in leads V4/V5/II, respectively. Serial ECG analyses showed stable to slow progression of the ECG phenotype. Exercise accentuated the ST-deviations with a maximum difference between rest/stress (mean) of -117 μV in lead V5. During a mean follow-up of 9.3±7.1 years 5 (13%) patients developed sustained ventricular arrhythmias or (aborted) sudden cardiac death, 10 (25%) developed atrial fibrillation, 2 (5%) other supraventricular arrhythmias, and 10 (25%) were diagnosed with left ventricular ejection fraction ≤50%. The ventricular arrhythmias were polymorphic with relatively short-coupled premature ventricular contractions at onset (300-360 ms); no QT prolongation was observed. Seven patients had at least one catheter ablation; 5 for supraventricular arrhythmias and 2 for ventricular arrhythmias. Males experienced more arrhythmic end points than females (P<0.01).

CONCLUSIONS

The familial ST-depression ECG phenotype is stable to slowly progressive after medium-term follow-up. Clinically, both supra- and ventricular arrhythmias are common; as are some degree of left ventricular systolic dysfunction. Familial ST-depression represent a novel inherited cause of polymorphic ventricular tachycardia.

Distinct Features of Probands With Early Repolarization and Brugada Syndromes Carrying SCN5A Pathogenic Variants

BACKGROUND

Two major forms of inherited J-wave syndrome (JWS) are recognized: early repolarization syndrome (ERS) and Brugada syndrome (BrS).

OBJECTIVES

This study sought to assess the distinct features between patients with ERS and BrS carrying pathogenic variants in SCN5A.

METHODS

Clinical evaluation and next-generation sequencing were performed in 262 probands with BrS and 104 with ERS. Nav1.5 and Kv4.3 channels were studied with the use of patch-clamp techniques. A computational model was used to investigate the protein structure.

RESULTS

The SCN5A+ yield in ERS was significantly lower than in BrS (9.62% vs 22.90%; P = 0.004). Patients diagnosed with ERS displayed shorter QRS and QTc than patients with BrS. More than 2 pathogenic SCN5A variants were found in 5 probands. These patients displayed longer PR intervals and QRS duration and experienced more major arrhythmia events (MAE) compared with those carrying only a single pathogenic variant. SCN5A-L1412F, detected in a fever-induced ERS patient, led to total loss of function, destabilized the Nav1.5 structure, and showed a dominant-negative effect, which was accentuated during a febrile state. ERS-related SCN5A-G452C did not alter the inward sodium current (INa) when SCN5A was expressed alone, but when coexpressed with KCND3 it reduced peak INa by 44.52% and increased the transient outward potassium current (Ito) by 106.81%.

CONCLUSIONS

These findings point to SCN5A as a major susceptibility gene in ERS as much as it is in BrS, whereas the lower SCN5A+ ratio in ERS indicates the difference in underlying electrophysiology. These findings also identify the first case of fever-induced ERS and demonstrate a critical role of Ito in JWS and a higher risk for MAE in JWS probands carrying multiple pathogenic variants in SCN5A.

Susceptibility to Ventricular Arrhythmias Resulting from Mutations in FKBP1B, PXDNL, and SCN9A Evaluated in hiPSC Cardiomyocytes

BACKGROUND

We report an inherited cardiac arrhythmia syndrome consisting of Brugada and Early Repolarization Syndrome associated with variants in SCN9A, PXDNL, and FKBP1B. The proband inherited the 3 mutations and exhibited palpitations and arrhythmia-mediated syncope, whereas the parents and sister, who carried one or two of the mutations, were asymptomatic.

METHODS AND RESULTS

We assessed the functional impact of these mutations in induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) derived from the proband and an unaffected family member. Current and voltage clamp recordings, as well as confocal microscopy analysis of Ca2+ transients, were evaluated in hiPSC-CMs from the proband and compared these results with hiPSC-CMs from undiseased controls. Genetic analysis using next-generation DNA sequencing revealed heterozygous mutations in SCN9A, PXDNL, and FKBP1B in the proband. The proband displayed right bundle branch block and exhibited episodes of syncope. The father carried a mutation in FKBP1B, whereas the mother and sister carried the SCN9A mutation. None of the 3 family members screened developed cardiac events. Action potential recordings from control hiPSC-CM showed spontaneous activity and a low upstroke velocity. In contrast, the hiPSC-CM from the proband showed irregular spontaneous activity. Confocal microscopy of the hiPSC-CM of the proband revealed low fluorescence intensity Ca2+ transients that were episodic in nature. Patch-clamp measurements in hiPSC-CM showed no difference in I Na but reduced I Ca in the proband compared with control. Coexpression of PXDNL-R391Q with SCN5A-WT displayed lower I Na density compared to PXDNL-WT. In addition, coexpression of PXDNL-R391Q with KCND3-WT displayed significantly higher I to density compared to PXDNL-WT.

CONCLUSION

SCN9A, PXDNL, and FKBP1B variants appeared to alter spontaneous activity in hiPSC-CM. Only the proband carrying all 3 mutations displayed the ERS/BrS phenotype, whereas one nor two mutations alone did not produce the clinical phenotype. Our results suggest a polygenic cause of the BrS/ERS arrhythmic phenotype due to mutations in these three gene variants caused a very significant loss of function of I Na and I Ca and gain of function of I to.

Inter-Regulation of Kv4.3 and Voltage-Gated Sodium Channels Underlies Predisposition to Cardiac and Neuronal Channelopathies

Background: Genetic variants in voltage-gated sodium channels (Na_v) encoded by SCNXA genes, responsible for I_Na, and K_v4.3 channels encoded by KCND3, responsible for the transient outward current (I_to), contribute to the manifestation of both Brugada syndrome (BrS) and spinocerebellar ataxia (SCA19/22). We examined the hypothesis that K_v4.3 and Na_v variants regulate each other’s function, thus modulating I_Na/I_to balance in cardiomyocytes and I_Na/I_(A) balance in neurons. Methods: Bicistronic and other constructs were used to express WT or variant Na_v1.5 and K_v4.3 channels in HEK293 cells. I_Na and I_to were recorded. Results: SCN5A variants associated with BrS reduced I_Na, but increased I_to. Moreover, BrS and SCA19/22 KCND3 variants associated with a gain of function of I_to, significantly reduced I_Na, whereas the SCA19/22 KCND3 variants associated with a loss of function (LOF) of I_to significantly increased I_Na. Auxiliary subunits Na_vβ1, MiRP3 and KChIP2 also modulated I_Na/I_to balance. Co-immunoprecipitation and Duolink studies suggested that the two channels interact within the intracellular compartments and biotinylation showed that LOF SCN5A variants can increase K_v4.3 cell-surface expression. Conclusion: Na_v and K_v4.3 channels modulate each other’s function via trafficking and gating mechanisms, which have important implications for improved understanding of these allelic cardiac and neuronal syndromes.

Prevalence and Significance of an Early Repolarization Electrocardiographic Pattern and Its Mechanistic Insight Based on Cardiac Magnetic Resonance Imaging in Patients With Acute Myocarditis

BACKGROUND

An early repolarization electrocardiographic (ER-ECG) pattern is caused by various pathophysiological conditions and is reported to be a predictor of life-threatening ventricular tachyarrhythmias. However, little evidence has been reported on the prevalence and significance of the ER-ECG pattern in acute myocarditis. This study aimed to investigate the prevalence and significance of the ER-ECG pattern and its mechanistic insight based on the cardiac magnetic resonance findings in patients with acute myocarditis.

METHODS

Thirty patients (23 men; 39.2±19.1 years) with a diagnosis of acute myocarditis by a clinical presentation between March 2011 and April 2018 were retrospectively evaluated. The patients were divided into 2 groups depending on the presence of an ER-ECG pattern on admission.

RESULTS

Nine cases had an ER-ECG pattern, which was defined as terminal QRS notching or slurring with an amplitude of >0.1 mV in at least 2 inferior or lateral leads (early repolarization [ER] group), whereas the remaining 21 cases had broad ST-segment elevation or pathological Q waves (non-ER group). The cardiac troponin T level was significantly higher in the non-ER group than ER group (3.2±4.3 versus 0.9±1.2 ng/mL; P=0.036). The ECG changes returned to baseline along with the normalization of the cardiac biomarkers. Nine of the 21 non-ER group patients, but none of the 9 ER group patients, developed a fulminant course and lethal ventricular tachyarrhythmias. T2-weighted cardiac magnetic resonance showed high-intensity signals over the entire transmural left ventricle in the non-ER group, whereas they were localized to the left ventricular epicardium in the ER group.

CONCLUSIONS

The ER-ECG pattern in acute myocarditis was transient and reversible and was not associated with a worse prognosis. Inflammation/swelling localized to the left ventricular epicardium because of acute myocarditis might provide a mechanistic insight into the ER-ECG pattern.

Electrophysiological Basis for Early Repolarization Syndrome

During last centuries, Early Repolarization pattern has been interpreted as an ECG manifestation not linked to serious cardiovascular events. This view has been challenged on the basis of sporadic clinical observations that linked the J-wave with ventricular arrhythmias and sudden cardiac death. The particular role of this characteristic pattern in initiating ventricular fibrillation has been sustained by clinical descriptions of a marked and consistent J-wave elevation preceding the onset of the ventricular arrhythmia. Until now, Early Repolarization syndrome patients have been evaluated using ECG and theorizing different interpretations of the findings. Nonetheless, ECG analysis is not able to reveal all depolarization and repolarization properties and the explanation for this clinical events. Recent studies have characterized the epicardial substrate in these patients on the basis of high-resolution data, in an effort to provide insights into the substrate properties that support arrhythmogenicity in these patients. An overview for the current evidence supporting different theories explaining Early Repolarization Syndrome is provided in this review. Finally, future developments in the field directed toward individualized treatment strategies are examined.