Diastolic biomechanics in normal infants utilizing MRI tissue tagging

Background-Most of what is known about diastolic function in normal infants is derived from flow and pressure measurements. Little is known about regi onal diastolic strain and wall motion. Methods and Results-Magnetic resonance tissue tagging was performed in 11 n ormal infants to determine regional diastolic strain and wall motion. Track ing diastolic motion of the intersection points and finite strain analysis yielded regional rotation, radial displacement, and E-1 and E-2 strains at 3 short-axis levels (significance was defined as P<0.05), E-2 "circumferent ial lengthening" strains were significantly greater at the lateral wall, re gardless of short-axis level, whereas E-1 "radial thinning" strains were si milar in all wall regions at all short-axis levels. In general, no differen ces were noted in strain dispersion within a wall region or in endocardial/ epicardial strain at all short-axis levels, At all short-axis levels, septa l radial motion was significantly less than in other wall regions, No signi ficant differences in radial wall motion between short-axis levels were not ed. Rotation was significantly greater at the apical short-axis level in al l wall regions than in other short-axis levels, and it was clockwise. At th e atrioventricular valve, septal and anterior walls rotated slightly clockw ise, whereas the lateral and inferior walls rotated counterclockwise. Conclusions-Diastolic biomechanics in infants are not homogeneous. The late ral walls are affected most by strain, and the septal walls undergo the lea st radial wall motion. Apical walls undergo the most rotation. These normal data may help in the understanding of diastolic dysfunction in infants wit h congenital heart disease.