The secret life of the mitral valve

Antonio M. Calafiore*, Antonio Totaro, Nicola Testa, Cosimo Sacra, Gaetano Castellano, Stefano Guarracini, Massimo Di Marco, Sotirios Prapas, Mario Gaudino, Roberto Lorusso, Domenico Paparella, Michele Di Mauro

*Corresponding author for this work

Research output: Contribution to journal(Systematic) Review article peer-review

Abstract

In secondary mitral regurgitation, the concept that the mitral valve (MV) is an innocent bystander, has been challenged by many studies in the last decades. The MV is a living structure with intrinsic plasticity that reacts to changes in stretch or in mechanical stress activating biohumoral mechanisms that have, as purpose, the adaptation of the valve to the new environment. If the adaptation is balanced, the leaflets increase both surface and length and the chordae tendineae lengthen: the result is a valve with different characteristics, but able to avoid or to limit the regurgitation. However, if the adaptation is unbalanced, the leaflets and the chords do not change their size, but become stiffer and rigid, with moderate or severe regurgitation. These changes are mediated mainly by a cytokine, the transforming growth factor-beta (TGF-beta), which is able to promote the changes that the MV needs to adapt to a new hemodynamic environment. In general, mild TGF-beta activation facilitates leaflet growth, excessive TGF-beta activation, as after myocardial infarction, results in profibrotic changes in the leaflets, with increased thickness and stiffness. The MV is then a plastic organism, that reacts to the external stimuli, trying to maintain its physiologic integrity. This review has the goal to unveil the secret life of the MV, to understand which stimuli can trigger its plasticity, and to explain why the equation "large heart = moderate/severe mitral regurgitation" and "small heart = no/mild mitral regurgitation" does not work into the clinical practice.

Original languageEnglish
Pages (from-to)247-259
Number of pages13
JournalJournal of Cardiac Surgery
Volume36
Issue number1
Early online date1 Nov 2020
DOIs
Publication statusPublished - Jan 2021

Keywords

  • ischemia
  • ischemic adaptation
  • left ventricle
  • mitral regurgitation
  • mitral valve
  • GROWTH-FACTOR-BETA
  • TGF-BETA
  • COMPENSATORY MECHANISM
  • MESENCHYMAL TRANSITION
  • EXTRACELLULAR-MATRIX
  • HEART-FAILURE
  • LEAFLET
  • REGURGITATION
  • ANGIOTENSIN
  • ADAPTATION

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