Abstract Body (Do not enter title and authors here): Background: Cardiac strain analysis is an effective method for diagnosing subclinical myocardial diseases and for follow-up assessments. Echocardiography is used for noninvasive strain calculations; however current methods are limited to 2D and segmental strains, missing 3D myocardial finite deformations.
Research Question: Based on our novel method, high-resolution 4D echocardiography can accurately characterize myocardial fiber mechanics, enabling detailed mapping of fiber contraction patterns that were previously thought to be beyond the capability of this imaging modality.
Methods: The endocardial and epicardial surfaces are tracked independently throughout the cardiac cycle and combined to construct a 3D shell model composed of tetrahedral elements. The deformation gradient and 3D finite strain tensors are calculated for each of these tetrahedral elements, with end-diastole as the reference. Incompressibility is enforced by adjustments in the epicardium. The resulting principal strains and their directions provide insights into local tissue deformation. Myofibers are constructed along the direction of maximum contraction. Strain distributions are visualized using a combined LV-RV bullseye representation. The strain analysis is applied to patients diagnosed with pulmonary hypertension (PH) to assess its clinical applicability.
Results: Strain, in its general 3D form, includes three normal and three shear components—all of which are captured by this method throughout the myocardium and cardiac cycle. The three principal strain directions provide localized insights into tissue deformation: two, typically with negative strain, lie almost tangential to the myocardial surface and reflect contractile behavior; the third is across the thickness. The direction of peak contraction aligns with fiber orientation, reflecting the net mechanical function of myocytes. Analysis in healthy and pulmonary hypertension subjects reveals reduced RV principal strain and compensatory elevated LV strain, highlighting the method’s potential for early disease detection.
Conclusion: An improved 3D myocardial strain characterization using 4D echocardiography is presented, enabling in vivo assessment of dynamic fiber contraction patterns and facilitating convenient clinical comparisons across patient cohorts.