Effects of acute ischemic mitral regurgitation on three-dimensional mitral leaflet edge geometry.
BACKGROUND
Improved quantitative understanding of in vivo leaflet geometry in ischemic mitral regurgitation (IMR) is needed to improve reparative techniques, yet few data are available due to current imaging limitations. Using marker technology we tested the hypotheses that IMR (1) occurs chiefly during early systole; (2) affects primarily the valve region contiguous with the myocardial ischemic insult; and (3) results in systolic leaflet edge restriction.


METHODS
Eleven sheep had radiopaque markers sutured as five opposing pairs along the anterior (A(1)-E(1)) and posterior (A(2)-E(2)) mitral leaflet free edges from the anterior commissure (A(1)-A(2)) to the posterior commissure (E(1)-E(2)). Immediately postoperatively, biplane videofluoroscopy was used to obtain 4D marker coordinates before and during acute proximal left circumflex artery occlusion. Regional mitral orifice area (MOA) was calculated in the anterior (Ant-MOA), middle (Mid-MOA), and posterior (Post-MOA) mitral orifice segments during early systole (EarlyS), mid systole (MidS), and end systole (EndS). MOA was normalized to zero (minimum orifice opening) at baseline EndS. Tenting height was the distance of the midpoint of paired markers to the mitral annular plane at EndS.


RESULTS
Acute ischemia increased echocardiographic MR grade (0.5+/-0.3 vs 2.3+/-0.7, p<0.01) and MOA in all regions at EarlyS, MidS, and EndS: Ant-MOA (7+/-10 vs 22+/-19 mm(2), 1+/-2 vs 18+/-16 mm(2), 0 vs 17+/-15 mm(2)); Mid-MOA (9+/-13 vs 25+/-17 mm(2), 3+/-6 vs 21+/-19 mm(2), 0 vs 25+/-17 mm(2)); and Post-MOA (8+/-10 vs 25+/-16, 2+/-4 vs 22+/-13 mm(2), 0 vs 23+/-13 mm(2)), all p<0.05. There was no change in MOA throughout systole (EarlyS vs MidS vs EndS) during baseline conditions or ischemia. Tenting height increased with ischemia near the central and the anterior commissure leaflet edges (B(1)-B(2): 7.1+/-1.8mm vs 7.9+/-1.7 mm, C(1)-C(2): 6.9+/-1.3mm vs 8.0+/-1.5mm, both p<0.05).


CONCLUSIONS
MOA during ischemia was larger throughout systole, indicating that acute IMR in this setting is a holosystolic phenomenon. Despite discrete postero-lateral myocardial ischemia, Post-MOA was not disproportionately larger. Acute ovine IMR was associated with leaflet restriction near the central and the anterior commissure leaflet edges. This entire constellation of annular, valvular, and subvalvular ischemic alterations should be considered in the approach to mitral repair for IMR.
Bothe
Wolfgang
W
Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, CA 94305-5247, United States.
Nguyen
Tom C
TC
Ennis
Daniel B
DB
Itoh
Akinobu
A
Carlhäll
Carl Johan
CJ
Lai
David T
DT
Ingels
Neil B
NB
Miller
D Craig
DC
D000208:Acute Disease; D000818:Animals; D003287:Contrast Media; D004195:Disease Models, Animal; D005471:Fluoroscopy; D006439:Hemodynamics; D008297:Male; D008943:Mitral Valve / Q000503:physiopathology*; D008944:Mitral Valve Insufficiency / Q000209:etiology / Q000503:physiopathology*; D017202:Myocardial Ischemia / Q000150:complications / Q000503:physiopathology*; D010210:Papillary Muscles / Q000503:physiopathology; D012756:Sheep; D013599:Systole; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology
D003287:Contrast Media