Mechanism of mitral leaflet excursion.
Dent, John M., William D. Spotnitz, Stanton P. Nolan, Ananda R.
Jayaweera, William P. Glasheen, Sanjiv Kaul.
From the Divisions of Cardiovascular Medicine and Thoracic and
Cardiovascular Surgery, University of Virginia School of Medicine,
Charlottesville, Virginia
APStracts 2:0328H, 1995.
The factors that influence the extent of mitral leaflet open ing (MLO)
and closure (MLC) have not been defined. We hypothesized that: a)
Left ventricular (LV) systolic function determines the rate of
increase of the early diastolic left atrial (LA)-LV pres sure
gradient which is responsible for the extent of MLO; b) LV systolic
function also determines the rate of change of the early systolic LV
-LA pressure gradient which determines the degree of MLC; and, c) the
extents of MLO and MLC during LV systolic dysfunc tion are not
principally mediated via tethering of the leaflets to the submitral
apparatus. Accordingly in 6 dogs (Group I) global LV function was
changed by altering left main coronary artery flow and LA pressure
was held relatively constant. LV end-systolic dimension and peak
positive LV dP/dt correlated best with the degrees of MLO and MLC,
with average correlation coefficients of 0.88 and 0.68, and 0.86 and
0.72, respectively. Transient sudden increase in LA pressure did not
change mitral valve kinetics. Although transecting the submitral
apparatus in 3 dogs (Group II) resulted in flailing of the mitral
leaflets during normal LV systolic function, the ex tents of MLO and
MLC during LV systolic dysfunction were still in fluenced by LV
systolic function. It is concluded that LV systolic function
determines the extent (both opening and closure) of mitral leaflet
excursion and that the latter is not necessarily mediated via
traction through the submitral apparatus during LV systolic
dysfunction.
Received 20 December 1994; accepted in final form 6 July 1995.
APS Manuscript Number H119-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 August 1995.