Progressive angiogenesis and lone atrial fibrillation: The expression of VEGF, bFGF and AT2 in the fibrillating human atrium

Objective: Atrial fibrillation (AF) is a progressive disease often associated with fibrosis. Angiogenic growth factors are involved in the fibrotic process. Therefore, we investigated the expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and angiotensin receptor type 2 (AT2) in the atrium in patients with paroxysmal AF (PAF), chronic AF (CAF), non-ischemic patients in sinus rhythm (NISR) and ischemic patients in SR (ISR).

Methods: Atrial tissue samples were obtained from patients with lone AF (n=26) or sinus rhythm (n=13). VEGF, bFGF and AT2 protein levels were measured by quantitative Western Blotting techniques.

Results: The bFGF protein expression was significantly and systematically increased in patients in ISR vs. lone CAF (p<0,05) and lone CAF vs. lone PAF (p<0,05). The expression of bFGF in ISR, lone PAF and lone CAF were significantly enhanced vs. NISR (p<0,001; p<0,05, p<0,01). The expression of VEGF exhibited similar results, however there was no significant differences between NISR and lone PAF. Differences in the expression of AT2 among the patient groups exhibited a similar pattern (ISR>lone CAF>lone PAF>NISR), however not significant.

Conclusion: The progression of AF from PAF to CAF is associated with an increased expression of angiogenetic growth factors. Therefore, we speculate that lone AF is sufficient to increase angiogenic growth factors driving the fibrotic process.