Paradoxic decrease in ischemic mitral regurgitation with papillary muscle dysfunction - Insights from three-dimensional and contrast echocardiographywith strain rate measurement
E. Messas et al., Paradoxic decrease in ischemic mitral regurgitation with papillary muscle dysfunction - Insights from three-dimensional and contrast echocardiographywith strain rate measurement, CIRCULATION, 104(16), 2001, pp. 1952-1957
Citations number
35
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
Background-Ischemic mitral regurgitation (MR) was first ascribed to papilla
ry muscle (PM) contractile dysfunction. Current theories include apical lea
flet tethering caused by left ventricular (LV) distortion, but PM dysfuncti
on is still postulated and commonly diagnosed. PM contraction, however, par
allels apical tethering, suggesting the hypothesis that PM contractile dysf
unction can actually diminish MR due to ischemic distortion of the inferior
base alone.
Methods and Results-We therefore occluded the proximal circumflex circulati
on in 7 sheep while maintaining PM perfusion, confirmed by contrast echocar
diography. By 3D echocardiography, we measured the tethering distance betwe
en the ischemic medial PM tip and anterior annulus and LV ejection volume t
o give MR (by subtracting flowmeter LV outflow). In 6 sheep without initial
MR, inferior ischemia alone produced PM tip retraction with restricted lea
flet closure and mild-to-moderate MR (regurgitant fraction, 25.2 +/-2.8%).
Adding PM ischemia consistently decreased MR and tethering distance (5.2 +/
-0.3 to 1.4 +/-0.3 mL; +3.8 +/-0.5 min to -2.2 +/-0.7 turn axially relative
to baseline; P <0.001) as PM strain rate decreased from +0.78 +/-0.07 per
second (contraction) to -0.42 +/-0.06 per second (elongation, P <0.001) and
leaflet tenting decreased. In one sheep, prolapse and MR resolved with int
erior ischemia and recurred with PM ischemia.
Conclusions-PM contractile dysfunction can paradoxically decrease MR from i
nferobasal ischemia by reducing leaflet tethering to improve coaptation. Th
is emphasizes the role of geometric factors in ischemic MR mechanism and po
tential therapy.