Correlation between hemodynamic parameters and intra-arterial septum motion in DeBakey Type III aortic dissections...

Outcome prediction in DeBakey Type III aortic dissections (AD) remains challenging. Large variations in AD morphology, physiology and treatment exist. A patient-specific approach towards a detailed understanding of the distinct features of each single case might be needed to account for this variation. In particular, an improved characterization of hemodynamic parameters in addition to geometrical quantities may yield deeper insight into this complex disease. Advances in cardiovascular magnetic resonance imaging (CMR) have resulted in pulse sequences that provide time-resolved information of blood velocities, aortic wall motion and, with the administration of exogenous intravenous contrast bolus, contrast passage timings. Here we provide a combined approach in a group of 10 AD patients using 2D phase contrast magnetic resonance imaging (2D pcMRI) and Time-resolved Angiography With Interleaved Stochastic Trajectories (TWIST) to quantify blood velocities, flow rates, maximum signal enhancement from exogenous contrast and time to maximum signal enhancement in the true lumen (TL) and false lumen (FL). The FL-TL dynamic pressure gradient was derived from 2D pcMRI velocity measurements. These hemodynamic parameters were correlated with dynamic parameters for the intra-arterial septum (IS) wall motion derived from 2D pcMRI. A strong positive correlation was found between the TL-FL dynamic pressure gradient and maximum IS extension (R=0.76) as well as with maximum IS contraction (R=-0.51) Taking the ratio of maximum extension to maximum contraction, the correlation increased to R= 0.81. The ratio of TL to FL volumetric flow rate showed a high correlation with the difference in FL-TL times to maximum enhancement (R=0.87) illustrating that higher flow in the TL will result in delayed contrast arrival in the FL and vice versa. Analogous, the TL to FL ratio of maximum enhancement correlated with the TL to FL ratio of the maximum volumetric flow rate (R=0.85). 2D pcMRI and 4D MRA in combination with exogenous intravenous contrast bolus allows characterization of hemodynamics in DeBakey type III AD. High correlations between IS wall motion, TL and FL pressure differences, flows and times to maximum enhancement were found. An extension of our analysis to follow-up imaging examinations are warranted to establish the potential for hemodynamic parameters determined with CMR as a marker for clinical outcome in longitudinal studies.