hERG Blockade by Iboga Alkaloids

The iboga alkaloids are a class of naturally occurring and synthetic compounds, some of which modify drug self-administration and withdrawal in humans and preclinical models. Ibogaine, the prototypic iboga alkaloid that is utilized clinically to treat addictions, has been associated with QT prolongation, torsades de pointes and fatalities. hERG blockade as IKr was measured using the whole-cell patch clamp technique in HEK 293 cells. This yielded the following IC50 values: ibogaine manufactured by semisynthesis via voacangine (4.09 ± 0.69 µM) or by extraction from T. iboga (3.53 ± 0.16 µM); ibogaine’s principal metabolite noribogaine (2.86 ± 0.68 µM); and voacangine (2.25 ± 0.34 µM). In contrast, the IC50 of 18-methoxycoronaridine, a product of rational synthesis and current focus of drug development was >50 µM. hERG blockade was voltage dependent for all of the compounds, consistent with low-affinity blockade. hERG channel binding affinities (Ki) for the entire set of compounds, including 18-MC, ranged from 0.71 to 3.89 µM, suggesting that 18-MC binds to the hERG channel with affinity similar to the other compounds, but the interaction produces substantially less hERG blockade. In view of the extended half-life of noribogaine, these results may relate to observations of persistent QT prolongation and cardiac arrhythmia at delayed intervals of days following ibogaine ingestion. The apparent structure–activity relationships regarding positions of substitutions on the ibogamine skeleton suggest that the iboga alkaloids might provide an informative paradigm for investigation of the structural biology of the hERG channel

Left ventricular myocardial work in patients with severe aortic stenosis

Background: Left ventricular myocardial work (LVMW) is a novel method to assess left ventricular (LV) function using pressure-strain loops that takes into consideration LV afterload. The estimation of LV afterload in patients with severe aortic stenosis (AS) may be challenging, and no study so far has investigated LVMW in this setting. The aim of this study was to develop a method to calculate LVMW in patients with severe AS and to analyze its relationship with heart failure symptoms.Methods: Indices of LVMW were calculated in 120 patients with severe AS who underwent transcatheter aortic valve replacement and invasive LV and aortic pressure measurements. LV systolic pressure was also derived by adding the mean aortic valve gradient to the aortic systolic pressure. LV global longitudinal strain and echocardiography-derived LV systolic pressure were then incorporated to construct pressure-strain loops of the left ventricle.Results: An excellent correlation was observed between LVMW indices calculated using the invasive and echocardiography-derived LV systolic pressure. Patients in New York Heart Association functional class III or IV (n = 97 [73%]) had lower LV global longitudinal strain, LV global work index, LV global constructive work, and right ventricular free wall strain compared with those in New York Heart Association functional class I or II. In contrast to LV global longitudinal strain, LV global work index (odds ratio per 100 mm Hg% increase, 0.91; 95% CI, 0.85-0.98; P = .012) and LV global constructive work showed independent associations with New York Heart Association functional class III or IV heart failure symptoms.Conclusions: The calculation of echocardiography-based LVMW indices is feasible in patients with severe AS. In particular, LV global work index and global constructive work showed independent associations with heart failure symptoms and may provide additional information on myocardial remodeling and function in patients with severe AS.Cardiolog

Cell identity and nucleo-mitochondrial genetic context modulate OXPHOS performance and determine somatic heteroplasmy dynamics

Heteroplasmy, multiple variants of mitochondrial DNA (mtDNA) in the same cytoplasm, may be naturally generated by mutations but is counteracted by a genetic mtDNA bottleneck during oocyte development. Engineered heteroplasmic mice with nonpathological mtDNA variants reveal a nonrandom tissue-specific mtDNA segregation pattern, with few tissues that do not show segregation. The driving force for this dynamic complex pattern has remained unexplained for decades, challenging our understanding of this fundamental biological problem and hindering clinical planning for inherited diseases. Here, we demonstrate that the nonrandom mtDNA segregation is an intracellular process based on organelle selection. This cell type-specific decision arises jointly from the impact of mtDNA haplotypes on the oxidative phosphorylation (OXPHOS) system and the cell metabolic requirements and is strongly sensitive to the nuclear context and to environmental cues

Arrhythmic risk prediction in arrhythmogenic right ventricular cardiomyopathy : external validation of the arrhythmogenic right ventricular cardiomyopathy risk calculator

Aims: Arrhythmogenic right ventricular cardiomyopathy (ARVC) causes ventricular arrhythmias (VAs) and sudden cardiac death (SCD). In 2019, a risk prediction model that estimates the 5-year risk of incident VAs in ARVC was developed (ARVCrisk.com). This study aimed to externally validate this prediction model in a large international multicentre cohort and to compare its performance with the risk factor approach recommended for implantable cardioverter-defibrillator (ICD) use by published guidelines and expert consensus. Methods and results: In a retrospective cohort of 429 individuals from 29 centres in North America and Europe, 103 (24%) experienced sustained VA during a median follow-up of 5.02 (2.05-7.90) years following diagnosis of ARVC. External validation yielded good discrimination [C-index of 0.70 (95% confidence interval-CI 0.65-0.75)] and calibration slope of 1.01 (95% CI 0.99-1.03). Compared with the three published consensus-based decision algorithms for ICD use in ARVC (Heart Rhythm Society consensus on arrhythmogenic cardiomyopathy, International Task Force consensus statement on the treatment of ARVC, and American Heart Association guidelines for VA and SCD), the risk calculator performed better with a superior net clinical benefit below risk threshold of 35%. Conclusion: Using a large independent cohort of patients, this study shows that the ARVC risk model provides good prognostic information and outperforms other published decision algorithms for ICD use. These findings support the use of the model to facilitate shared decision making regarding ICD implantation in the primary prevention of SCD in ARVC

2022 ESC guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: developed by the task force for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death of the European Society of Cardiology (ESC) endorsed by the Association for European Paediatric and Congenital Cardiology (A

Cardiolog