Ventricular Tachycardias

Cardiac phenotype in adolescents and young adults with long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) deficiency

PURPOSE

Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency (LCHADD) is a rare fatty acid oxidation disorder characterized by recurrent episodes of metabolic decompensation and rhabdomyolysis, as well as retinopathy, peripheral neuropathy, and cardiac involvement, such as infantile dilated cardiomyopathy. Because LCHADD patients are surviving longer, we sought to characterize LCHADD-associated major cardiac involvement in adolescence and young adulthood.

METHODS

A retrospective cohort of 16 adolescent and young adult participants with LCHADD was reviewed for cardiac phenotype.

RESULTS

Major cardiac involvement occurred in 9 of 16 participants, including sudden death, out-of-hospital cardiac arrest, acute cardiac decompensations with heart failure and/or in-hospital cardiac arrest, end-stage dilated cardiomyopathy, and moderate restrictive cardiomyopathy. Sudden cardiac arrest was more common in males and those with a history of infant cardiomyopathy.

CONCLUSION

The cardiac manifestations of LCHADD in adolescence and early adulthood are complex and distinct from the phenotype seen in infancy. Life-threatening arrhythmia occurs at substantial rates in LCHADD, often in the absence of metabolic decompensation or rhabdomyolysis. The potential risk factors identified here-male sex and history of infant cardiomyopathy-may hint at strategies for risk stratification and possibly the prevention of these events.

Abdominal compression as motion management for stereotactic radiotherapy of ventricular tachycardia

Background and purpose

Stereotactic body radiotherapy (SBRT) has emerged as a promising treatment for patients with ventricular tachycardia (VT) who do not respond to standard treatments. However, the management of respiratory motion during treatment remains a challenge. This study aimed to investigate the effect of abdominal compression (AC) on respiratory induced motion in the heart.

Materials and methods

A patient cohort of 18 lung cancer patients was utilized, where two four-dimensional computed tomography (4DCT) scans were performed for each patient, one with and one without AC. The patient setup consisted of an AC plate together with a stereotactic body frame. The left coronary artery, the left anterior descending artery, the lateral wall of the left ventricle, the heart apex, the carina, and the right and left diaphragm were delineated in max expiration and max inspiration phases in both 4DCT scans. The center of mass shift from expiration to inspiration phase was determined to assess the AC's impact on respiratory motion.

Results

A significant reduction in motion in the superior-inferior direction was found for all heart structures when AC was used. The median respiratory motion of the heart structures decreased by approximately 1-3 mm with AC in the superior-inferior direction, and approximately 60% of the patients had a motion reduction ≥3 mm in the left ventricle wall.

Conclusion

These findings suggest that AC has the potential to improve the motion management of SBRT for VT patients, by reducing the respiratory induced motion in the heart.

Evaluation of premature ventricular complexes during in-hospital ECG monitoring as a predictor of ventricular tachycardia in an intensive care unit cohort

In-hospital electrocardiographic (ECG) monitors are typically configured to alarm for premature ventricular complexes (PVCs) due to the potential association of PVCs with ventricular tachycardia (VT). However, no contemporary hospital-based studies have examined the association of PVCs with VT. Hence, the benefit of PVC monitoring in hospitalized patients is largely unknown. This secondary analysis used a large PVC alarm data set to determine whether PVCs identified during continuous ECG monitoring were associated with VT, in-hospital cardiac arrest (IHCA), and/or death in a cohort of adult intensive care unit patients. Six PVC types were examined (i.e., isolated, bigeminy, trigeminy, couplets, R-on-T, and run PVCs) and were compared between patients with and without VT, IHCA, and/or death. Of 445 patients, 48 (10.8%) had VT; 11 (2.5%) had IHCA; and 49 (11%) died. Isolated and run PVC counts were higher in the VT group (p = 0.03 both), but group differences were not seen for the other four PVC types. The regression models showed no significant associations between any of the six PVC types and VT or death, although confidence intervals were wide. Due to the small number of cases, we were unable to test for associations between PVCs and IHCA. Our findings suggest that we should question the clinical relevance of activating PVC alarms as a forewarning of VT, and more work should be done with larger sample sizes. A more precise characterization of clinically relevant PVCs that might be associated with VT is warranted.

Functional evaluation of the tachycardia patient-derived iPSC cardiomyocytes carrying a novel pathogenic SCN5A variant

Tachycardia is characterized by high beating rates that can lead to life-threatening fibrillations. Mutations in several ion-channel genes were implicated with tachycardia; however, the complex genetic contributors and their modes of action are still unclear. Here, we investigated the influence of an SCN5A gene variant on tachycardia phenotype by deriving patient-specific iPSCs and cardiomyocytes (iPSC-CM). Two tachycardia patients were genetically analyzed and revealed to inherit a heterozygous p.F1465L variant in the SCN5A gene. Gene expression and immunocytochemical analysis in iPSC-CMs generated from patients did not show any significant changes in mRNA levels of SCN5A or gross NaV1.5 cellular mislocalization, compared to healthy-derived iPSC-CMs. Electrophysiological and contraction imaging analysis in patient iPSC-CMs revealed intermittent fibrillation-like states, occasional arrhythmic events, and sustained high-paced contractions that could be selectively reduced by flecainide treatment. The patch-clamp analysis demonstrated a negative shift in the voltage-dependent activation at the patient-derived iPSC-CMs compared to the healthy control line, suggestive of a gain-of-function activity associated with the SCN5A^+/p.F1465L variant. Our patient-derived iPSC-CM model recapitulated the clinically relevant characteristics of tachycardia associated with a novel pathogenic SCN5A^+/p.F1465L variant leading to altered Na⁺ channel kinetics as the likely mechanism underlying high excitability and tachycardia phenotype.

Attenuation and Structural Transformation of Crassicauline A During Sand Frying Process and Antiarrhythmic Effects of its Transformed Products

To ensure safety and efficacy, most Aconitum herbs should be processed before clinical application. The processing methods include boiling, steaming, and sand frying. Among these methods, the transformation pathways of diterpenoid alkaloids in the process of sand frying are more complicated. Therefore, crassicauline A, a natural product with two ester bonds, was chosen as the experimental object. Consequently, a known alkaloid, together with three new alkaloids, was derived from crassicauline A. Meanwhile, the cardiotoxicity of converted products was reduced compared with their parent compound. Interestingly, some diterpenoid alkaloids have similar structures but opposite effects, such as arrhythmia and antiarrhythmic. Considering the converted products are structural analogues of crassicauline A, herein, the antiarrhythmic activity of the transformed products was further investigated. In a rat aconitine-induced arrhythmia assay, the three transformed products, which could dose-dependently delay the ventricular premature beat (VPB) incubation period, reduce the incidence of ventricular tachycardia (VT), combined with the increasing arrhythmia inhibition rate, exhibited prominent antiarrhythmic activities. Our experiments speculated that there might be at least two transformation pathways of crassicauline A during sand frying. The structure-activity data established in this paper constructs the critical pharmacophore of diterpenoid alkaloids as antiarrhythmic agents, which could be helpful in searching for the potential drugs that are equal or more active and with lower toxicity, than currently clinical used antiarrhythmic drugs.

Overexpression of the medium‑conductance calcium‑activated potassium channel (SK4) and the HCN2 channel to generate a biological pacemaker

Ion channels serve important roles in the excitation‑contraction coupling of cardiac myocytes. Previous studies have shown that the overexpression or activation of intermediate‑conductance calcium‑activated potassium channel (SK4, encoded by KCNN4) in embryonic stem cell‑derived cardiomyocytes can significantly increase their automaticity. The mechanism underlying this effect is hypothesized to be associated with the activation of hyperpolarization‑activated cyclic nucleotide‑gated channel 2 (HCN2). The aim of the present study was to explore whether a biological pacemaker could be constructed by overexpressing SK4 alone or in combination with HCN2 in a rat model. Ad‑green fluorescent protein (GFP), Ad‑KCNN4 and Ad‑HCN2 recombinant adenoviruses were injected into the left ventricle of Sprague‑Dawley rat hearts. The rats were divided into a GFP group (n=10), an SK4 group (n=10), a HCN2 group (n=10) and an SK4 + HCN2 (SK4/HCN2) group (n=10). The isolated hearts were perfused at 5‑7 days following injection, and a complete heart block model was established. Compared with the GFP group, overexpressing SK4 alone did not significantly increase the heart rate after establishment of a complete heart block model [98.1±8.9 vs. 96.7±7.6 beats per min (BPM)], The heart rates in the SK4/HCN2 (139.9±21.9 BPM) and HCN2 groups (111.7±5.5 BPM) were significantly increased compared with the GFP and SK4 groups, and the heart rates in the SK4/HCN2 group were significantly increased compared with the SK4 or HCN2 groups. In the HCN2 (n=8) and the SK4/HCN2 (n=7) groups, the shape of the spontaneous ventricular rhythm was the same as the pacing‑induced ectopic rhythm in the transgenically altered site. By contrast, these rhythms were different in the SK4 (n=10) and GFP (n=10) groups. There were no significant differences in action potential duration alternans or ventricular arrhythmia inducibility between the four groups (all P>0.05). Western blotting, reverse transcription‑quantitative PCR and immunohistochemistry analyses showed that the expression levels of SK4 and HCN2 were significantly increased at the transgene site. Biological pacemaker activity could be successfully generated by co‑overexpression of SK4 and HCN2 without increasing the risk of ventricular arrhythmias. The overexpression of SK4 alone is insufficient to generate biological pacemaker activity. The present study provided evidence that SK4 and HCN2 combined could construct an ectopic pacemaker, laying the groundwork for the development of improved biological pacing mechanisms in the future.

A novel approach to devise the therapy for ventricular fibrillation by epicardial delivery of lidocaine using active hydraulic ventricular attaching support system: An experimental study in rats

Active hydraulic ventricular attaching support system (ASD) placed around the heart is not only a novel, nontransplant surgical device used for epicardial administration of drugs like lidocaine, but also a promising treatment option for ventricular fibrillation (VF) and arrhythmias. We hypothesize that lidocaine in 5 mg/kg dose released by ASD significantly improves the VF in the rat model. Sprague-Dawley (SD) rats were selected and were divided into four groups, intravenous injection (IV), epicardial infusion (EI), ASD, and control. ASD group was further divided into four subgroups for different lidocaine doses (i) ASD+A group (10 mg/kg), (ii) ASD+B group (5 mg/kg), (iii) ASD+C group (1 mg/kg), and (iv) ASD+D group (0.1 mg/kg). VF was induced with calcium chloride injection and was confirmed by electrocardiogram (ECG) in all the groups. VF was treated with different doses of lidocaine using different modes of administration. Data were analyzed using the SPSS 19.0 Chi-square tests and one-way analysis of variance (ANOVA). The Kaplan-Meier curve for OS was compared to the Logrank test based on the survival time. P < 0.05 was considered as statistically significant. ASD + B group (5 mg/kg) showed significantly reduced sgroup. The time of first sinus rhythm recovered (15.96 ± 21.77 min) and ▵T-SOD in plasma (-42.02 ± 26.99 U/mL) was significantly different than that of control, IV, and EI groups. ▵T-SOD in plasma for all ASD-treated groups was smaller than the control and IV groups. This study proves that ASD with 5 mg/kg lidocaine dose appears as a promising therapeutic platform for treating VF in rats. Furthermore, ASD may also have potential for treating VF or other cardiovascular disease with different therapeutic agents. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1722-1731, 2019.

Amplitude screening improves performance of AMSA method for predicting success of defibrillation in swine model

PURPOSE

A novel amplitude screening method, termed Optimal Amplitude Spectrum Area (Opt-AMSA) with the aim of improving the performance of the Amplitude Spectrum Area (AMSA) method, was proposed to optimize the timing of defibrillation. We investigated the effects of the Opt-AMSA method on the prediction of successful defibrillation when compared with AMSA in a porcine model of ventricular fibrillation (VF).

METHOD

60 male domestic pigs were untreated in the first 10 min of VF, then received cardiopulmonary resuscitation (CPR) for 6 min. Values of Opt-AMSA and AMSA were calculated every minute before defibrillation. Linear regression was used to evaluate the correlation between Opt-AMSA and AMSA. Receiver Operating Characteristic (ROC) analysis was conducted for the two methods and to compare their predictive values.

RESULTS

The values of both AMSA and Opt-AMSA gradually decreased over time during untreated VF in all animals. The values of both methods of defibrillation were slightly increased after the implementation of CPR in animals that were successfully resuscitated, while there were no significant changes in either method in those who ultimately failed to resuscitate. The significant positive correlation between Opt-AMSA and AMSA was shown by Pearson correlation analysis. ROC analysis showed that Opt-AMSA (AUC = 0.87) significantly improved the performance of AMSA (AUC = 0.77) to predict successful defibrillation (Z = 2.27, P < 0.05).

CONCLUSION

Both the Opt-AMSA and AMSA methods showed high potential to predict the success of defibrillation. Moreover, the Opt-AMSA method improved the performance of the AMSA method, and may be a promising tool to optimize the timing of defibrillation.