Published Online
on November 27, 2006

A more recent version of this article appeared on December 12, 2006

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Submitted on August 8, 2006
Revised on September 27, 2006
Accepted on October 5, 2006

Theoretical Impact of the Injection of Material Into the Myocardium. A Finite Element Model Simulation

Samuel T. Wall BS;, Joseph C. Walker PhD, Kevin E. Healy PhD, Mark B. Ratcliffe MD, and Julius M. Guccione PhD^*

From the University of California at Berkeley/San Francisco, Joint Graduate Group in Bioengineering (S.T.W., J.C.W., K.E.H., M.B.R., J.M.G.); Departments of Material Science and Engineering (K.E.H.) and Bioengineering (K.E.H.), University of California at Berkeley; Department of Surgery, University of California at San Francisco (M.B.R., J.M.G.); and Veterans Affairs Medical Center, San Francisco, Calif (M.B.R., J.M.G.).

^* To whom correspondence should be addressed. E-mail: Julius.Guccione{at}med.va.gov.

Background--To treat cardiac injuries created by myocardial infarcts, current approaches seek to add cells and/or synthetic extracellular matrices to the damaged ventricle to restore function. Because definitive myocardial regeneration remains undemonstrated, we propose that cardiac changes observed from implanted materials may result from altered mechanisms of the ventricle.

Methods and Results--We exploited a validated finite element model of an ovine left ventricle with an anteroapical infarct to examine the short-term effect of injecting material to the left ventricular wall. The model’s mesh and regional material properties were modified to simulate expected changes. Three sets of simulations were run: (1) single injection to the anterior border zone; (2) therapeutic multiple border zone injections; and (3) injection of material to the infarct region. Results indicate that additions to the border zone decrease end-systolic fiber stress proportionally to the fractional volume added, with stiffer materials improving this attenuation. As a potential therapy, small changes in wall volume (4.5%) reduce elevated border zone fiber stresses from mean end-systole levels of 28.2 kPa (control) to 23.3 kPa (treatment), similar to levels of 22.5 kPA computed in remote regions. In the infarct, injection improves ejection fraction and the stroke volume/end-diastolic volume relationship but has no effect on the stroke volume/end-diastolic pressure relationship.

Conclusions--Simulations indicate that the addition of noncontractile material to a damaged left ventricular wall has important effects on cardiac mechanics, with potentially beneficial reduction of elevated myofiber stresses, as well as confounding changes to clinical left ventricular metrics.

Key words: heart failure • infarction • mechanics • myocardium • stress

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