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Limited ability to activate protein C confers left atrial endocardium a thrombogenic phenotype: a role in

Jorge Cerveró1, Ramón Montes, Francisco España

  • 1Division of Cardiovascular Sciences, Centre for Applied Medical Research, University of Navarra, Avenida Pío XII, 55, 31008 Pamplona, Spain.

Stroke
|June 25, 2011
PubMed

Insights

Left atrial tissue shows impaired protein C activation due to lower thrombomodulin expression, increasing cardioembolic stroke risk. This finding helps explain why thrombi form in the left atrium during atrial fibrillation.

Area of Science:

  • Cardiovascular Research
  • Hemostasis and Thrombosis
  • Biomedical Science

Background:

  • Atrial fibrillation is a primary risk factor for cardioembolic stroke.
  • Thrombus formation predominantly occurs in the left atrial appendage, but the underlying reasons are unclear.
  • Understanding differential thrombogenicity between atrial chambers is crucial for stroke prevention.

Purpose of the Study:

  • To compare protein C activation capacity between the right and left atria.
  • To investigate the expression levels of thrombomodulin and endothelial protein C receptor in the endocardium of both atria.
  • To elucidate the mechanisms behind the higher thrombogenicity of the left atrial appendage.

Main Methods:

  • Ex vivo assessment of protein C activation in atrial tissues from 6 non-human primates (Macaca fascicularis).
  • Immunofluorescence staining to quantify thrombomodulin and endothelial protein C receptor expression on the endocardium.
  • Comparative analysis of protein C activation and receptor expression between right and left atria.

Main Results:

  • Protein C activation capacity was significantly reduced by half in the left atrium compared to the right atrium (P=0.028).
  • Thrombomodulin expression was significantly lower in the left atrial endocardium (52.5±19.9 AU) than in the right atrial endocardium (72.1±18.8 AU) (P=0.028).
  • No significant difference was observed in the expression of endothelial protein C receptor between the two atria.

Conclusions:

  • Reduced protein C activation in the left atrium, linked to diminished thrombomodulin expression, may underlie its increased thrombogenicity.
  • These findings offer a potential explanation for the higher incidence of thrombus formation in the left atrial appendage.
  • This research contributes to understanding the pathophysiology of cardioembolic stroke in atrial fibrillation.
Abstract

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