Anti-arrhythmic therapy in patients with non-ischemic cardiomyopathy

Stereoselective block of the hERG potassium channel by the Class Ia antiarrhythmic drug disopyramide

Potassium channels encoded by human Ether-à-go-go-Related Gene (hERG) are inhibited by diverse cardiac and non-cardiac drugs. Disopyramide is a chiral Class Ia antiarrhythmic that inhibits hERG at clinical concentrations. This study evaluated effects of disopyramide enantiomers on hERG current (IhERG) from hERG expressing HEK 293 cells at 37 °C. S(+) and R(-) disopyramide inhibited wild-type (WT) IhERG with IC50 values of 3.9 µM and 12.9 µM respectively. The attenuated-inactivation mutant N588K had little effect on the action of S(+) disopyramide but the IC50 for the R(-) enantiomer was ~ 15-fold that for S(+) disopyramide. The enhanced inactivation mutant N588E only slightly increased the potency of R(-) disopyramide. S6 mutation Y652A reduced S(+) disopyramide potency more than that of R(-) disopyramide (respective IC50 values ~ 49-fold and 11-fold their WT controls). The F656A mutation also exerted a stronger effect on S(+) than R(-) disopyramide, albeit with less IC50 elevation. A WT-Y652A tandem dimer exhibited a sensitivity to the enantiomers that was intermediate between that of WT and Y652A, suggesting Y652 groups on adjacent subunits contribute to the binding. Moving the Y (normally at site 652) one residue in the N- terminal (up) direction in N588K hERG markedly increased the blocking potency of R(-) disopyramide. Molecular dynamics simulations using a hERG pore model produced different binding modes for S(+) and R(-) disopyramide consistent with the experimental observations. In conclusion, S(+) disopyramide interacts more strongly with S6 aromatic binding residues on hERG than does R(-) disopyramide, whilst optimal binding of the latter is more reliant on intact inactivation.

Arrhythmogenic Left Ventricular Cardiomyopathy: From Diagnosis to Risk Management

PURPOSE OF REVIEW

Left ventricular arrhythmogenic cardiomyopathy (ALVC) is a rare and poorly characterized cardiomyopathy that has recently been reclassified in the group of non-dilated left ventricular cardiomyopathies. This review aims to summarize the background, diagnosis, and sudden cardiac death risk in patients presenting this cardiomyopathy.

RECENT FINDINGS

Although there is currently a lack of data on this condition, arrhythmogenic left ventricular dysplasia can be considered a specific disease of the left ventricle (LV). We have collected the latest evidence about the management and the risks associated with this cardiomyopathy.

SUMMARY

Left ventricular arrhythmogenic cardiomyopathy is still poorly characterized. ALVC is characterized by fibrofatty replacement in the left ventricular myocardium, with variable phenotypic expression. Diagnosis is based on a multiparametric approach, including cardiac magnetic resonance (CMR) and genetic testing, and is important for sudden cardiac death (SCD) risk stratification and management. Recent guidelines have improved the management of left ventricular arrhythmogenic cardiomyopathy. Further studies are necessary to improve knowledge of this cardiomyopathy.

Antiarrhythmic Sotalol, Occlusion/Occlusion-like Syndrome in Rats, and Stable Gastric Pentadecapeptide BPC 157 Therapy

We focused on the first demonstration that antiarrhythmics, particularly class II and class III antiarrhythmic and beta-blocker sotalol can induce severe occlusion/occlusion-like syndrome in rats. In this syndrome, as in similar syndromes with permanent occlusion of major vessels, peripheral and central, and other similar noxious procedures that severely disable endothelium function, the stable gastric pentadecapeptide BPC 157-collateral pathways activation, was a resolving therapy. After a high dose of sotalol (80 mg/kg intragastrically) in 180 min study, there were cause-consequence lesions in the brain (swelling, intracerebral hemorrhage), congestion in the heart, lung, liver, kidney, and gastrointestinal tract, severe bradycardia, and intracranial (superior sagittal sinus), portal and caval hypertension, and aortal hypotension, and widespread thrombosis, peripherally and centrally. Major vessels failed (congested inferior caval and superior mesenteric vein, collapsed azygos vein). BPC 157 therapy (10 µg, 10 ng/kg given intragastrically at 5 min or 90 min sotalol-time) effectively counteracted sotalol-occlusion/occlusion-like syndrome. In particular, eliminated were heart dilatation, and myocardial congestion affecting coronary veins and arteries, as well as myocardial vessels; eliminated were portal and caval hypertension, lung parenchyma congestion, venous and arterial thrombosis, attenuated aortal hypotension, and centrally, attenuated intracranial (superior sagittal sinus) hypertension, brain lesions and pronounced intracerebral hemorrhage. Further, BPC 157 eliminated and/or markedly attenuated liver, kidney, and gastrointestinal tract congestion and major veins congestion. Therefore, azygos vein activation and direct blood delivery were essential for particular BPC 157 effects. Thus, preventing such and similar events, and responding adequately when that event is at risk, strongly advocates for further BPC 157 therapy.

Inherited cardiac diseases, pluripotent stem cells, and genome editing combined-the past, present, and future

Research on mechanisms underlying monogenic cardiac diseases such as primary arrhythmias and cardiomyopathies has until recently been hampered by inherent limitations of heterologous cell systems, where mutant genes are expressed in noncardiac cells, and physiological differences between humans and experimental animals. Human-induced pluripotent stem cells (hiPSCs) have proven to be a game changer by providing new opportunities for studying the disease in the specific cell type affected, namely the cardiomyocyte. hiPSCs are particularly valuable because not only can they be differentiated into unlimited numbers of these cells, but they also genetically match the individual from whom they were derived. The decade following their discovery showed the potential of hiPSCs for advancing our understanding of cardiovascular diseases, with key pathophysiological features of the patient being reflected in their corresponding hiPSC-derived cardiomyocytes (the past). Now, recent advances in genome editing for repairing or introducing genetic mutations efficiently have enabled the disease etiology and pathogenesis of a particular genotype to be investigated (the present). Finally, we are beginning to witness the promise of hiPSC in personalized therapies for individual patients, as well as their application in identifying genetic variants responsible for or modifying the disease phenotype (the future). In this review, we discuss how hiPSCs could contribute to improving the diagnosis, prognosis, and treatment of an individual with a suspected genetic cardiac disease, thereby developing better risk stratification and clinical management strategies for these potentially lethal but treatable disorders.

Targeted Medical Therapies for Hypertrophic Cardiomyopathy

PURPOSE OF REVIEW

The management of hypertrophic cardiomyopathy (HCM) has changed considerably over the years, although molecular therapies targeting core mechanisms of the disease are still lacking. This review provides an overview of the contemporary medical approach to patients with HCM, and of promising novel developments hopefully soon to enter the clinical arena.

RECENT FINDINGS

Our perception of therapeutic targets for medical therapy in HCM is rapidly evolving. Novel approaches include myocardial metabolic modulation, late sodium current inhibition, and allosteric myosin inhibition, actively pursued to reduce and hopefully prevent the development of severe HCM phenotypes, improve symptom control, and preserve patients from disease-related complications. Clinical management of patients with HCM should be guided by in-depth knowledge of the complex mechanisms at the energetic, metabolic, and electrophysiologic level. Until new experimental therapies become available, tailored management of modifiable disease manifestations should be pursued, including lifestyle counseling and prevention of comorbidities.