The transition of right ventricle (RV) from a compensated to decompensated state contributes to survival in pulmonary arterial hypertension (PAH). However, little is known about the significance of right atrial (RA) dysfunction on disease progression in PAH. We present a rapid assessable strain parameter that requires the automatic tracking of only 3 anatomical reference points – thus avoiding the segment contour tracking near the insertion of the anterior leaflet into the tricuspid annulus. The atrioventricular junctions (squares in Fig. 1) are selected as the tricuspid valve insertion points at the septal and free wall borders of the annulus on the 4-chamber view. The mid-point of posterior RA wall is defined as the intersection point of the RA posterior wall and the RA long-axis. The tracking system uses the method of adaptive template matching and is semi-automatic with mask selection in the initial frame as the only user input. The calculation of RA longitudinal strain (ε) at any time point (t) in the cardiac cycle from the time of minimal RA volume (time 0) is based on the Lagrange strain formula as follows: ε(t)=(L(t)-L_0)×100/L_0.
The RSA method was applied in a group of 80 PAH patients, including 58 with hemodynamically compensated RV function (PAH-C) and 22 with decompensated RV function (PAH-D), and 80 age- and gender-matched normal controls. In PAH compared to controls, significantly reduced RA strains and SRs were observed. Among PAH patients, PAH-D had significantly impaired RA strains and SRs compared to PAH-C. RA total stain and passive strain were the best parameters for differentiating PAH-D from PAH-C.
RA strain parameters investigated, which are highly reproducible and readily obtainable from post-processing of standard 4-chamber cine CMR images, are promising candidate indices for non-invasive detection of RA dysfunction, RV decompensation and monitoring of disease progression in PAH patients.