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(Circulation. 2002;106:I-168.)
© 2002 American Heart Association, Inc.

Thoracic Transplantation and Mechanical Support for Congestive Heart Failure

Altered Left Ventricular Geometry Changes the Border Zone Temporal Distribution of Stress in an Experimental Model of Left Ventricular Aneurysm: A Finite Element Model Study

Pavlos Moustakidis, MD; Hersh S. Maniar, MD; Brian P. Cupps, PhD; Tarek Absi, MD; Jie Zheng, PhD; Julius M. Guccione, PhD; Thoralf M. Sundt, MD; Michael K. Pasque, MD

From the Department of Surgery, Division of Cardiothoracic Surgery (P.M., H.S.M., B.P.C., T.A., M.K.P.), and Department of Radiology, Washington University (J.Z.), St. Louis, Mo.; Department of Surgery, University of California, San Francisco, Calif. (J.M.G.); and Department of Surgery, Division of Cardiovascular Surgery, Mayo Clinic, Rochester, Minn. (T.M.S.).

Correspondence to Michael K. Pasque, MD, Division of Cardiothoracic Surgery, One Barnes-Jewish Hospital Plaza, 3103 Queeny Tower, St. Louis, MO 63110-1013. E-mail pasquem{at}msnotes.wustl.edu

Abstract

Background Left ventricular aneurysm (LVA) is a significant complication of myocardial infarction that may lead to global left ventricular (LV) dysfunction. However, the exact mechanism underlying the abnormal function has not been elucidated. In this study we tested the hypothesis that changes in LV geometry cause both an increase in wall stress and a change in the temporal distribution of stress in the LVA border zone (BZ) during systole.

Methods Transmural anteroapical infarcts were created in adult Dorsett sheep (n=8) and were allowed to mature into LVAs for 10 weeks. Animals were imaged subsequently using MRI with simultaneous recording of intraventricular pressures. Cardiac models were constructed from the MRI images at end-diastole, isovolumic systole, peak-systole and end-systole. Two short-axis slices, 1 basal and 1 apical were analyzed. The apical slice included the septal and anterior component of the aneurysm as well as the corresponding BZs and normal myocardium. Regional wall stresses were calculated using finite element analysis and compared with stresses in corresponding regions from normal control sheep (n=7).

Results In the LVA group, stress was significantly increased in the BZ at the end-diastolic, isovolumic, peak-systolic, and end-systolic instants (P<0.001 for all). In addition the temporal distribution of stress was significantly altered with maximum stress occurring at peak instead of isovolumic systole.

Conclusions Geometric changes in the LVA hearts increased wall stress and altered its temporal distribution in the BZ region. Correlation of this finding with the corresponding regional blood flow, oxygen consumption, and mechanical systolic performance may help elucidate the mechanism underlying the observed global LV dysfunction.

Key Words: ischemia • coronary disease • magnetic resonance imaging • mechanics • computers