Novel secretome-driven arrhythmogenic mechanisms in atrial cardiomyopathy

Atrial fibrillation (AF) represents a significant clinical challenge, yet the molecular mechanisms driving arrhythmogenicity in atrial cardiomyopathy remain incompletely understood.

We analyzed serum samples from 23 well-characterized patients (mean age 68±1.7 years) with persistent AF and preserved left ventricular ejection fraction (55.6±2.3%). All patients underwent comprehensive evaluation including invasive left atrial pressure measurement (8.6±0.97 mmHg), left atrial strain analysis (reservoir: 21.1±5.1%, conduit: -12.6±1.5%, contraction: -8.7±4.4%), and left atrial volume index assessment (39.7±2.9 ml/m²). High-density 3D electroanatomic mapping using multipolar catheters was performed to determine left atrial voltage as a surrogate for fibrosis, revealing low voltage areas (<0.5 mV) in 28.2±9.7% of the left atrium. Proteomic analysis was performed on 88 samples collected from both coronary sinus and arterial blood during atrial fibrillation and sinus rhythm, using an Exploris 480 mass spectrometer in nanoflow-DIA mode. Functional validation was conducted using isolated mouse heart preparations exposed to patient serum under varying pacing conditions (100-1000 bpm).

Proteomic analysis identified 719 protein groups, with 504 showing >80% valid values after filtering. Notable findings included differential expression of YWHAZ/YWHAE (14-3-3 proteins) and MMP9, suggesting altered regulation of cellular signaling and structural remodeling pathways during atrial fibrillation as compared to sinus rhythm in the same patient. Functional studies using patient serum and multi-electrode arrays demonstrated proarrhythmic effects of the atrial fibrillation proteome in hearts with pre-existing arrhythmic susceptibility. Even when including hearts without baseline arrhythmias, there was a trend toward increased AF episodes and longer AF duration upon exposure to atrial fibrillation proteome as compared to sinus rhythm proteome.

Our findings identify novel secretome-based mechanisms potentially contributing to AF pathogenesis, particularly involving 14-3-3 protein signaling and matrix remodeling pathways. The comprehensive patient characterization, including invasive pressure measurements, detailed atrial functional assessment, and high-density voltage mapping, strengthens the clinical relevance of these molecular insights, which may offer new therapeutic targets for atrial cardiomyopathy and associated arrhythmias.