system
Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Aged, Atrial Appendage, Atrial Fibrillation, Atrial Function, Right, Atrial Myosins, Calcium, Chronic Disease, Coronary Artery Disease, Female, Humans, Isometric Contraction, Male, Middle Aged, Myocardial Contraction.
user
Are atrial contractile protein content and function preserved in patients with coronary artery disease and atrial fibrillation? Context: Atrial fibrillation (AF) causes atrial contractile dysfunction. The focus of this study was to determine whether the contractile deficit of human AF is the result of altered contractile protein abundance and/or function. Atrial tissue from patients with chronic AF undergoing open-heart surgery was compared with the tissue from patients in normal sinus rhythm (NSR). Myosin isoform composition and content were determined. Intact native thin filament and cardiac myosin contractile protein performance were independently assessed in an in-vitro motility assay. Myosin isoform expression and total myosin content were not different between AF and NSR. Calcium-activated native thin filament function was similar between AF and NSR as measured by calcium sensitivity and maximal activation. Myosin isolated from the atria of AF and NSR groups showed similar unloaded shortening speeds and isometric force generation.
assistant
Unlike human ventricular dysfunction where contractile protein function is directly affected, the contractile deficit of AF is not the result of alterations in myosin content or contractile protein function. Final Decision: yes