Atrial contractile protein content and function are preserved in patients with coronary artery disease and atrial...

Area of Science:

• Cardiology
• Molecular Biology
• Physiology

Background:

• Atrial fibrillation (AF) is associated with impaired atrial contractility.
• The underlying mechanisms of this contractile dysfunction remain incompletely understood.
• Previous research in ventricular dysfunction suggests contractile protein alterations.

Purpose of the Study:

• To investigate whether atrial contractile dysfunction in human AF results from changes in contractile protein abundance or function.
• To compare myosin content and performance in atrial tissue from patients with AF versus normal sinus rhythm (NSR).

Main Methods:

• Atrial tissue samples were obtained from patients with chronic AF and NSR undergoing open-heart surgery.
• Myosin isoform composition and content were quantified.
• Contractile protein performance was assessed using an in-vitro motility assay.

Main Results:

• No significant differences were observed in myosin isoform expression or total myosin content between AF and NSR groups.
• Native thin filament function, assessed by calcium sensitivity and maximal activation, was similar in both groups.
• Isolated myosin from AF and NSR atria exhibited comparable unloaded shortening speeds and isometric force generation.

Conclusions:

• The contractile deficit observed in human atrial fibrillation is not attributable to alterations in myosin content.
• Contractile protein function, specifically myosin performance, is not compromised in the atria of patients with AF.
• These findings differentiate AF-related atrial dysfunction from human ventricular dysfunction, where contractile proteins are directly affected.