Characteristics of Sarcomere Proteins in Myocardial Sleeves of the Superior Vena Cava and Pulmonary Veins of the Porcine Heart.

Myocardial sleeves around caval and pulmonary veins have ectopic activity, which is the main cause of atrial arrhythmias. The morphological and electrophysiological properties of this myocardium differ from those of the atria, but its mechanical activity in large animals has not been studied. We compared the phosphorylation of sarcomere proteins and the functional characteristics of myosin from the left and right atria, superior vena cava, and pulmonary veins of the porcine heart.

Interatrial Features of Length-Dependent Regulation of Myocardial Force in Paroxysmal Atrial Fibrillation in Rats.

Myocardial stretch is a factor that forms an arrhythmogenic substrate for the progression of atrial fibrillation (AF). The features of force generation remodeling during stretching in the atrial myocardium in AF remain poorly understood. In this study, we analyzed changes in active and passive tension of left and right rat atrial myocardial strips at their diastolic stretching and the slopes of the "length-tension" relationship in acetylcholine-CaCl-induced paroxysmal AF.

An Exogenous NO Donor Provokes Mechanical Alternans in Normal Rat Atria and Impairs Sarcomere Contractility in Right Atrial Cardiomyocytes in Atrial Fibrillation.

Atrial fibrillation (AF) is the most common arrhythmia worldwide. AF is associated with a deficiency in nitric oxide (NO) production, which contributes to disturbances in the electrical and mechanical function of the atrial myocardium. NO donors are considered promising for the treatment and prevention of AF, but their effects on atrial contractility are unclear.

Tropomodulin-Tropomyosin Interplay Modulates Interaction Between Cardiac Myosin and Thin Filaments.

Tropomodulin (Tmod) is an actin-binding protein that interacts with tropomyosin and the actin filament at the pointed end. The influence of Tmod on the thin filament activation in the myocardium is not clear. We studied the interactions of Tmod1 and Tmod4 with the cardiac tropomyosin isoforms Tpm1.

Mavacamten Inhibits the Effect of the N-Terminal Fragment of Cardiac Myosin-Binding Protein C with the L352P Mutation on the Actin-Myosin Interaction at Low Calcium Concentrations.

Hypertrophic cardiomyopathy (HCM)-associated mutations in sarcomeric proteins lead to the disruption of the actin-myosin interaction and its calcium regulation and cause myocardial hypercontractility. About half of such mutations are found in the gene encoding cardiac myosin-binding protein C (cMyBP-C). A new approach to normalize cardiac contractile function in HCM is the use of β-cardiac myosin function inhibitors, one of which is mavacamten.