Three-dimensional biventricular strains in pulmonary arterial hypertension patients using hyperelastic warping

Abstract

Background and objective: Evaluation of biventricular function is an essential component of clinical management in pulmonary arterial hypertension (PAH). This study aims to examine the utility of biventricular strains derived from a model-to-image registration technique in PAH patients in comparison to age- and gender-matched normal controls.

Methods: A three-dimensional (3D) model was reconstructed from cine short- and long-axis cardiac magnetic resonance (CMR) images and subsequently partitioned into right ventricle (RV), left ventricle (LV) and septum. The hyperelastic warping method was used to register the meshed biventricular finite element model throughout the cardiac cycle and obtain the corresponding biventricular circumferential, longitudinal and radial strains.

Results: Intra- and inter-observer reproducibility of biventricular strains was excellent with all intra-class correlation coefficients > 0.84. 3D biventricular longitudinal, circumferential and radial strains for RV, LV and septum were significantly decreased in PAH patients compared with controls. Receiver operating characteristic (ROC) analysis showed that the 3D biventricular strains were better early markers (Area under the ROC curve = 0.96 for RV longitudinal strain) of ventricular dysfunction than conventional parameters such as two-dimensional strains and ejection fraction.

Conclusions: Our highly reproducible methodology holds potential for extending CMR imaging to characterize 3D biventricular strains, eventually leading to deeper understanding of biventricular mechanics in PAH.

Keywords: Biventricular strain; Cardiac magnetic resonance; Hyperelastic warping; Pulmonary arterial hypertension.

Fig. 1.

CMR images including short-axis images from apex to basal, and 2-, 3- and 4-chamber long-axis images.

Fig. 2.

Overall framework of quantifying the biventricular circumferential, longitudinal and radial strains.

Fig. 3.

Reconstruction of biventricular mesh: (A) segmentation of contours of LV, RV and septum; (B) Surface reconstruction; (C) Biventricular geometry (D) Biventricular mesh; (E) Partition of region (Red: right ventricle; Green: septum; Blue: left ventricle). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 4.

Measurement of the septal displacement in 4-chamber view as the boundary condition: (A) End-systole; (B) End-diastole; (C) Apply the displacement of septal on the model.

Fig. 5.

Registration of the meshed model with images for strain-time curves (A) meshed model with CMR image; (B) circumferential strain orientation; (C) circumferential strain-time curve; (D) longitudinal strain orientation; (E) longitudinal strain-time curve; (F) radial strain orientation; (G) radial strain-time curve.

Fig. 6.

Regional circumferential strain for middle short-axis slice by two-dimensional feature tracking.