TRANSESOPHAGEAL ECHOCARDIOGRAPHIC ASSESSMENT OF THE CONTRIBUTION OF INTRINSIC TISSUE THICKNESS TO THE APPEARANCE OF A THICK MITRAL-VALVE INPATIENTS WITH MITRAL-VALVE PROLAPSE
Ek. Louie et al., TRANSESOPHAGEAL ECHOCARDIOGRAPHIC ASSESSMENT OF THE CONTRIBUTION OF INTRINSIC TISSUE THICKNESS TO THE APPEARANCE OF A THICK MITRAL-VALVE INPATIENTS WITH MITRAL-VALVE PROLAPSE, Journal of the American College of Cardiology, 28(2), 1996, pp. 465-471
Objectives. This prospective, blinded transesophageal echocardiographi
c study was performed to determine the relative contributions of leafl
et redundancy and overlap versus intrinsic tissue thickening as mechan
isms for the apparent increase in diastolic thickness of the mitral va
lve. Background. Increased diastolic thickness of the mitral valve has
been identified as an echocardiographic feature that predicts subsequ
ent adverse sequelae in patients with mitral valve pro lapse (MVP). Me
thods. Eleven patients with clinical and transthoracic echo cardiograp
hic evidence of MVP and 11 age-matched control subjects underwent prot
ocol transesophageal echocardiography to image the mitral valve in two
orthogonal planes and to measure its thickness in systole and diastol
e. Results. Maximal diastolic width of the slack, unloaded anterior le
aflet was significantly greater in patients with MW than in control su
bjects (mean +/- SD: 0.64 +/- 0.20 cm vs. 0.30 +/- 0.04 cm, p < 0.001)
. Similarly, diastolic posterior leaflet width was greater in patients
with MW (0.67 +/- 0.39 cm vs. 0.31 +/- 0.06 cm, p < 0.01). In contras
t, minimal systolic width of the distended pressure loaded mitral valv
e was not significantly different between patients with MVP and contro
l subjects for either the anterior (0.22 +/- 0.05 cm vs. 0.20 +/- 0.04
cm, p = NS) or the posterior (0.25 +/- 0.07 cm vs. 0.24 + 0.05 cm, p
= NS) leaflets. The percent change in leaflet width from diastole to s
ystole (%Delta W), an index of the contribution of dynamic factors (e.
g., leaflet redundancy and overlap) to the apparent increase in diasto
lic leaflet thickness, was significantly greater in patients with MW t
han in control subjects for both the anterior (%Delta W 62 +/- 13% vs.
34 +/- 16%, p < 0.001) and the posterior (%Delta W54 +/- 19% vs. 22 /- 21%, p < 0.005) leaflets. Conclusions. The apparent increase in dia
stolic mitral leaflet thickness in patients with MW versus control sub
jects is largely attributable to dynamic factors such as leaflet redun
dancy, over lap and deformation. During diastole, when the mitral leaf
lets are slack and unstressed, the leaflets appear markedly thickened
in patients with MVP. In contrast, during systole, when developed intr
aventricular pressure distends the leaflets, causing them to stretch a
nd balloon into the left atrium, the intrinsic tissue thickness is muc
h less than that measured in diastole. These findings have important i
mplications for the morphologic criteria used to diagnose MVP and the
potential pathophysiologic mechanisms for adverse sequelae in this syn
drome.