Border zone geometry increases wall stress after myocardial infarction: contrast echocardiographic assessment.
After myocardial infarction (MI), the border zone expands chronically, causing ventricular dilatation and congestive heart failure (CHF). In an ovine model (n = 4) of anteroapical MI that results in CHF, contrast echocardiography was used to image short-axis left ventricular (LV) cross sections and identify border zone myocardium before and after coronary artery ligation. In the border zone at end systole, the LV endocardial curvature (K) decreased from 0.86 +/- 0.33 cm(-1) at baseline to 0.35 +/- 0.19 cm(-1) at 1 h (P < 0.05), corresponding to a mean decrease of 55%. Also in the border zone, the wall thickness (h) decreased from 1.14 +/- 0.26 cm at baseline to 1.01 +/- 0.25 cm at 1 h (P < 0.05), corresponding to a mean decrease of 11%. By Laplace's law, wall stress is inversely proportional to the product K. h. Therefore, a 55% decrease in K results in a 122% increase in circumferential stress; a 11% decrease in h results in a 12% increase in circumferential stress. These findings indicate that after MI, geometric changes cause increased dynamic wall stress, which likely contributes to border zone expansion and remodeling.
Jackson
Benjamin M
BM
Department of Surgery and the Harrison Department of Surgical Research, Hospital of the University of Pennsylvania, Philadelphia 19104, USA.
Gorman
Joseph H
JH
Salgo
Ivan S
IS
Moainie
Sina L
SL
Plappert
Theodore
T
St  John-Sutton
Martin
M
Edmunds
L Henry
LH
Gorman
Robert C
RC
D000818:Animals; D003287:Contrast Media; D004452:Echocardiography; D006321:Heart / Q000503:physiopathology*; D008955:Models, Cardiovascular; D009203:Myocardial Infarction / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D012756:Sheep; D013314:Stress, Mechanical
D003287:Contrast Media