Computational Investigation of Transmural Differences in Left Ventricular Contractility

Area of Science:

• Cardiovascular Physiology
• Computational Biology
• Biomedical Imaging

Background:

• Left ventricular (LV) myocardial contractility is crucial for cardiac pump function.
• Previous ex vivo studies indicated variations in cardiomyocyte force generation across LV myocardial layers.
• The in vivo distribution of myocardial contractile force remains incompletely understood.

Purpose of the Study:

• To investigate the in vivo transmural distribution of myocardial contractility.
• To develop and validate a noninvasive computational approach for assessing myocardial contractility.
• To compare in vivo findings with ex vivo experimental data.

Main Methods:

• Utilized animal-specific finite element (FE) models combined with magnetic resonance imaging (MRI) and pressure catheterization.
• Employed numerical optimization to determine transmural distributions of maximum isometric tension (Tmax) and reference sarcomere length (lR).
• Tested four cases with varying transmural Tmax and/or lR distributions.

Main Results:

• The best computational model fit to in vivo MRI-derived deformation occurred with distinct Tmax values across subendocardium, midmyocardium, and subepicardium, alongside transmurally varying lR.
• Calculated systolic strain from the best-fit FE model closely matched MRI data.
• Midmyocardial contractile force was found to be greater than in other transmural layers, aligning with ex vivo findings.

Conclusions:

• The proposed noninvasive computational approach can effectively predict the transmural distribution of myocardial contractility.
• FE models incorporating nonuniform myocardial contractility provide a more accurate representation of LV function.
• This method can be applied to study the impact of transmural changes in heart disease.