Tagged cine magnetic resonance imaging with a finite element model can predict the severity of retrosternal adhesions prior to redo cardiac surgery

Adhesion severity scores were determined by tagged cine MRI sequences. Scores were determined visually on the basis of the dynamics of the lattices overlaid on the sternum and the anterior aspect of the right ventricle. 0, No adhesion (lattices appeared deranged during the systolic phase as a consequence of displacement of the anterior aspect of the right ventricle); 1, mild adhesion (lattices were distorted to a limited extent during the systolic phase); 2, severe adhesion (lattices on the anterior aspect of the right ventricle remained unchanged over a cardiac cycle).

Analysis of strain at the surface of the right ventricle by tagged cine MRI sequences and a finite element model. A, Eighteen nodes were selected on the posterior plane of the sternum and the surface of the right ventricle. Nodes 1 to 9 were on the sternum, and nodes 10 to 18 were on the right ventricle. B, Representative distribution of strain in the retrosternal area. In the upper image, the triangles delineated with dotted lines are the diastolic elements (ie, before displacement of the nodes) and those delineated with solid lines are the systolic elements (ie, after displacement of the nodes). In the lower image, the fields subject to the highest levels of strain are colored red, and those subject to the lowest levels of strain are colored blue.

Inverse correlation between mean strain at the surface of the right ventricle and intraoperative adhesion score (r = −0.78, P < .01). Strain was calculated preoperatively by tagged cine MRIs and a finite element model. Intraoperative adhesion scores were determined visually by a surgeon who was blinded to the preoperative MRI assessments.

A, Correlation between intraoperative adhesion score and time to initiation of cardiopulmonary bypass (CPB) (r = 0.64, P < .01). B, Inverse correlation between time to initiation of CPB and mean strain at the surface of the right ventricle (r = −0.76, P < .01, y = 75.6 − 248log(x). Time to initiation of CPB is an indirect measure of the time required for lysis of adhesions. Strain was calculated preoperatively by tagged cine MRIs and a finite element model. Intraoperative adhesion scores were determined visually by a surgeon who was blinded to the preoperative MRI assessments.