Introduction: Coarctation repair is associated with a high risk of hypertension in later life, even in the absence of arch re-obstruction. Novel biomechanical markers are needed to understand the mechanism. We hypothesised that young adults after coarctation repair exhibit abnormal wall shear stress at the repair site, due to subtle abnormalities in arch geometry and vascular mechanics, that would correlate with central aortic pressure.
Methods: Sixteen young adults (mean age 28±8yrs) without re-obstruction after childhood coarctation repair underwent flow-sensitive four-dimensional (4D) MRI of the aortic arch at 1.5T, in addition to conventional anatomic and flow imaging. From four retrospectively positioned aortic planes, peak and mean wall shear-stress (WSS) was assessed. Peak aortic velocity, arch dimensions and z-scores, and central aortic pressure were measured.
Results: Mean absolute time-averaged WSS ranged between 0.37±0.06 N/m2 at the ascending aorta and 0.46±0.08 N/m2 at the upper descending aorta. Brachial systolic pressure ranged between 102-145mmHg, with estimated central systolic pressure between 88-129mmHg. Mean WSS at the distal transverse arch, but not at other arch sites, correlated with both central systolic (R=0.55, P=0.02) and pulse pressures (R=0.78, P<0.001), whereas aortic arch dimensions, z-scores and peak recorded velocities did not.
Conclusions: In young adults after coarctation repair, distal transverse arch WSS was highly correlated with central aortic pressures, even though conventional MRI arch measurements were not. Elevated WSS at the site of coarctation repair may play a role in the development of early-onset hypertension.