Regional wall motion and strain analysis across stages of Fontan reconstruction by magnetic resonance tagging

Abstract

To determine whether systolic regional wall deformation and motion, which may be used as an index of mechanical function, change with surgical intervention in patients with a functional single ventricle, a noninvasive magnetic resonance tagging technique was used to examine 33 such patients at all stages of Fontan reconstruction. The systolic motion of the intersection points was tracked to determine regional twist and radial shortening. Finite strain analysis was applied to the grid lines, and principal E1 strains were derived. The results were as follows. 1) Fontan and prebidirectional cavopulmonary anastomosis (hemiFontan) groups had the highest compressive strains, and regional heterogeneity of strain was least in the Fontan group. 2) Fontan patients had endocardial/epicardial strain different from the other surgical subgroups as well as the normal left ventricle, while the pre- and post-hemiFontan groups had basal/apical short-axis strain different from Fontan patients and normal subjects. 3) Functional single left ventricles had a different strain distribution across wall regions and surgical subgroup from functional single right ventricles. 4) Contrary to the normal human adult studied by the same method, which twists uniformly counterclockwise, 31 of 33 single ventricles, regardless of ventricular morphology or surgical subgroup, twisted counterclockwise in one region, clockwise in another, and met at a "transition zone" of no twist, which had the highest strains of all regions. 5) Radial contraction was greatest in the superior walls and least at the inferior walls of single-ventricle patients regardless of morphology. In the Fontan group, the inferior walls moved paradoxically. In conclusion, markedly different strain characteristics are noted at each stage of Fontan reconstruction, across various wall regions, and between ventricular morphological groups. Differences in regional wall motion were demonstrated in functional single ventricles throughout Fontan reconstruction regardless of morphology, and differences in associated strains and radial contraction were noted across various wall regions and surgical subgroups. These may play an important role in the energetics of the heart and the long-term viability of the single ventricle.