Three-Dimensional Principal Strain Analysis for Characterizing Subclinical Changes in Left Ventricular Function

Abstract

Subendocardial strain analysis is currently feasible in two-dimensional and three-dimensional (3D) echocardiography; however, there is a lack of clarity regarding the most useful strain component for subclinical disease detection. The aim of this study was to test the hypothesis that strain analysis along the direction of strongest and weakest systolic compression (referred to as principal and secondary strain, respectively) circumvents the need for multidirectional strains and provides a more simplified assessment of left ventricular subendocardial function. Strain analyses were performed by using two-dimensional and 3D echocardiography in 41 consecutive subjects with normal results on electron-beam computed tomography, including 15 controls and 26 patients with systemic hypertension. The direction of principal strain referenced the myofiber geometry obtained from diffusion tensor magnetic resonance imaging of a normal autopsied human heart. The incremental value of principal strain over multidirectional two-dimensional and 3D strain was analyzed. In healthy subjects, 50 ± 3% of the subendocardial shortening occurred in the cross-fiber direction (left-handed helical); this balance was significantly altered in patients with hypertension (P=.01). The magnitude of longitudinal and circumferential strain was similar in patients with hypertension and controls. However, the alteration of the directional contraction pattern resulted in reduced secondary strain magnitude in patients with hypertension (P=.01), and the differences were further exaggerated when the secondary strain was normalized by the principal strain magnitude (P=.004). Two-component principal and secondary strain analysis can be related to left ventricular myofiber geometry and may simplify the assessment of 3D left ventricular deformation by circumventing the need to assess multiple shortening and shear strain components.