REGIONAL WALL-MOTION AND STRAIN ANALYSIS ACROSS STAGES OF FONTAN RECONSTRUCTION BY MAGNETIC-RESONANCE TAGGING

To determine whether systolic regional wall deformation and motion, wh ich may be used as an index of mechanical function, change with surgic al intervention in patients with a functional single ventricle, a noni nvasive magnetic resonance tagging technique was used to examine 33 su ch patients at all stages of Fontan reconstruction. The systolic motio n of the intersection points was tracked to determine regional twist a nd radial shortening. Finite strain analysis was applied to the grid l ines, and principal E(1) strains were derived. The results were as fol lows. 1) Fontan and prebidirectional cavopulmonary anastomosis (hemiFo ntan) groups had the highest compressive strains, and regional heterog eneity of strain was least in the Fontan group. 2) Fontan patients had endocardial/epicardial strain different from the other surgical subgr oups as well as the normal left ventricle, while the pre- and post-hem iFontan groups had basal/apical short-axis strain different from Fonta n patients and normal subjects. 3) Functional single left ventricles h ad a different strain distribution across wall regions and surgical su bgroup from functional single right ventricles. 4) Contrary to the nor mal human adult studied by the same method, which twists uniformly cou nterclockwise, 31 of 33 single ventricles, regardless of ventricular m orphology 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 wa s greatest in the superior walls and least at the inferior walls of si ngle-ventricle patients regardless of morphology. In the Fontan group, the inferior walls moved paradoxically. In conclusion, markedly diffe rent strain characteristics are noted at each stage of Fontan reconstr uction, across various wall regions, and between ventricular morpholog ical groups. Differences in regional wall motion were demonstrated in functional single ventricles throughout Fontan reconstruction regardle ss of morphology, and differences in associated strains and radial con traction 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.