HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 296/6/H1766    most recent 00120.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Itoh, A. Articles by Ingels, N. B. PubMed PubMed Citation Articles by Itoh, A. Articles by Ingels, N. B., Jr.

Active stiffening of mitral valve leaflets in the beating heart

¹Department of Cardiothoracic Surgery, School of Medicine, and ²Department of Mechanical Engineering, Stanford University, Stanford, California; ⁴Department of Cardiovascular Physiology and Biophysics, Research Institute of The Palo Alto Medical Foundation, Palo Alto, California; and ³Department of Management and Engineering, Linköping University, Linköping, Sweden

Submitted 4 February 2009 ; accepted in final form 3 April 2009

The anterior leaflet of the mitral valve (MV), viewed traditionally as a passive membrane, is shown to be a highly active structure in the beating heart. Two types of leaflet contractile activity are demonstrated: 1) a brief twitch at the beginning of each beat (reflecting contraction of myocytes in the leaflet in communication with and excited by left atrial muscle) that is relaxed by midsystole and whose contractile activity is eliminated with β-receptor blockade and 2) sustained tone during isovolumic relaxation, insensitive to β-blockade, but doubled by stimulation of the neurally rich region of aortic-mitral continuity. These findings raise the possibility that these leaflets are neurally controlled tissues, with potentially adaptive capabilities to meet the changing physiological demands on the heart. They also provide a basis for a permanent paradigm shift from one viewing the leaflets as passive flaps to one viewing them as active tissues whose complex function and dysfunction must be taken into account when considering not only therapeutic approaches to MV disease, but even the definitions of MV disease itself.

anterior mitral valve leaflet; finite-element analysis; elastic modulus; mitral leaflet contractile tissue; electrical stimulation; β-receptor blockade