Atrial structure, function and arrhythmogenesis in aged and frail mice.

Area of Science:

• Cardiology
• Gerontology
• Physiology

Background:

• Atrial fibrillation (AF) is common in older adults, but aging is heterogeneous.
• Individual health status varies significantly among chronologically aged individuals, ranging from fit to frail.
• A frailty index (FI) can quantify health status differences in aging populations.

Purpose of the Study:

• To investigate the effects of aging and frailty on atrial function and the propensity for atrial arrhythmias.
• To utilize a mouse model and a frailty index to assess age-related changes in the atria.

Main Methods:

• Aged and young mice were assessed using a frailty index.
• Electrocardiography (ECG) was used to measure P wave duration and PR intervals.
• High-resolution optical mapping evaluated atrial conduction velocity and action potential duration.
• Histological analysis examined interstitial fibrosis and extracellular matrix remodeling regulators.

Main Results:

• Aged mice exhibited greater frailty and longer-lasting AF compared to young mice.
• P wave duration and PR intervals were longer in aged mice, with significant variability correlated to FI scores.
• Reduced atrial conduction velocity and action potential duration were observed in aged hearts, correlating with FI.
• Increased interstitial fibrosis and altered extracellular matrix remodeling were found in aged mice, also linked to frailty.

Conclusions:

• Aging induces structural and functional atrial changes, creating a substrate for atrial arrhythmias.
• Frailty is a key determinant of atrial dysfunction and arrhythmogenesis in aging.
• Health status heterogeneity, identifiable by FI, significantly influences age-related atrial changes and arrhythmia susceptibility.