Differential strain and velocity generation along the right ventricular free wall in pulmonary hypertension

Abstract

Background: In contrast to the homogeneously distributed deformation properties within the left ventricle, the right ventricular (RV) free wall (RVFW) shows a more inhomogeneous distribution. It has been demonstrated that pulmonary hypertension (PH) results in significant RVFW mechanical delay.

Objective: To assess the effect of the degree of pulmonary arterial systolic pressure on the RVFW strain gradient and on myocardial velocity generation.

Methods: Peak longitudinal strain and velocity data were collected from three different segments (basal, mid- and apical) of the RVFW in 17 normal individuals and 31 PH patients.

Results: A total of 144 RV wall segments were analyzed. RVFW strain values in individuals without PH were higher in the mid and apical segments than in the basal segment. In contrast, RVFW strain in PH patients was higher in basal segments and diminished toward the apex. In terms of RVFW velocities, both groups showed decremental values from basal to apical segments. Basal and mid-RVFW velocities were significantly lower in PH patients than in individuals without PH.

Conclusions: PH results in significant alterations of strain and velocity generation that occurs along the RVFW. Of these abnormalities, the reduction in strain from the mid and apical RVFW segments was most predictive of PH. It is important to be aware of these differences in strain generation when studying the effect of PH on the right ventricle. Additional studies are required to determine whether these differences are due to RV remodelling.

Figure 1)

Grey-scale four-chamber apical view with the typical orientation of the regions of interest for longitudinal strain measurement. The first sample volume was placed at the right ventricle (RV) base, the second sample volume at the RV mid-wall, and the third sample volume in the apical portion of the RV free wall distal to the insertion of the moderator band. Careful positioning of the region of interest was accomplished by tracking its location in both systole and diastole. LA Left atrium; LV Left ventricle; RA Right atrium

Figure 2)

A Box plot graph showing the mean and SD strain along the right ventricular free wall (RVFW) of pulmonary hypertension (PH) and normal (No PH) patients. Strain values are statistically lower in PH patients than in normal patients, and RVFW strain in PH patients is higher in basal segments and then diminishes toward the apex, contrary to what is seen in normal patients who show higher strain in the mid and apical RVFW segments than at the base. The negative strain values represent a reduction in shortening as fibres contract longitudinally. B Box plot graph showing the mean and SD myocardial velocities along the RVFW of normal and pulmonary hypertension (PH) patients. A longitudinal reduction in myocardial velocities can be seen from basal to apical segments in both normal and PH patients but it is of greater statistical significance in PH patients