A novel method for quantifying in-vivo regional left ventricular myocardial contractility in the border zone of a myocardial infarction.
Homogeneous contractility is usually assigned to the remote region, border zone (BZ), and the infarct in existing infarcted left ventricle (LV) mathematical models. Within the LV, the contractile function is therefore discontinuous. Here, we hypothesize that the BZ may in fact define a smooth linear transition in contractility between the remote region and the infarct. To test this hypothesis, we developed a mathematical model of a sheep LV having an anteroapical infarct with linearly-varying BZ contractility. Using an existing optimization method (Sun et al., 2009, "A Computationally Efficient Formal Optimization of Regional Myocardial Contractility in a Sheep With Left Ventricular Aneurysm," J. Biomech. Eng., 131(11), pp. 111001), we use that model to extract active material parameter T(max) and BZ width d(n) that "best" predict in-vivo systolic strain fields measured from tagged magnetic resonance images (MRI). We confirm our hypothesis by showing that our model, compared to one that has homogeneous contractility assigned in each region, reduces the mean square errors between the predicted and the measured strain fields. Because the peak fiber stress differs significantly (~15%) between these two models, our result suggests that future mathematical LV models, particularly those used to analyze myocardial infarction treatment, should account for a smooth linear transition in contractility within the BZ.
Departments of Surgery and Bioengineering, University of California, San Francisco, CA 94143, USA. likchuan@berkeley.edu
Lik Chuan
LC
Lee
Jonathan F
JF
Wenk
Doron
D
Klepach
Zhihong
Z
Zhang
David
D
Saloner
Arthur W
AW
Wallace
Liang
L
Ge
Mark B
MB
Ratcliffe
Julius M
JM
Guccione
D000818:Animals; D001794:Blood Pressure; D020342:Finite Element Analysis; D006352:Heart Ventricles / Q000503:physiopathology*; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000503:physiopathology*; D012756:Sheep; D013314:Stress, Mechanical