1357800 - Assessment of Left Ventricular Hemodynamic Forces in Pediatric Heart Transplant Patients

Heart transplant patients are at risk for sub-clinical and clinical rejection, which are often mild, focal and repetitive leading to myocardial fibrosis. These patients may have alter biomechanical properties despite having normal ejection fraction. Cardiac magnetic resonance (CMR) is a sensitive tool to identify both myocardial tissue parameters, and regional functional assessment; however, the unique biomechanical properties of the left ventricle (LV) cannot be assessed through conventional CMR techniques. Novel biomechanical parameters such as cine-derived hemodynamic force (HDF) may serve as early indicator for insidious biomechanical dysfunction¹. Thus, we investigated HDF through cine derived wall motion in the LV as a novel biomarker of myocardial dysfunction in post-transplant patients.



Methods: A retrospective analysis of CMR studies from 13 heart transplanted patients (8 of whom had clinical or biopsy proven rejection and 5 with no evidence of rejection) and 11 controls was performed. Feature-tracking (Qstrain, Medis) was performed on short-axis and long-axis cine images to capture LV wall motion.  A novel technique based on diffeomorphic mapping was used to reconstruction three-dimensional LV kinematic models to calculate the global HDF vector and work (dot product of HDF and distance) throughout the cardiac cycle (Figure 1).  The magnitude of HDF across the cardiac cycle was further separated into three directions for analysis: apical-basal, lateral-septal, and anterior-posterior directions.


Results:

There was no significant difference in LV ejection fraction between transplant patients and controls (54+/- 6% vs 58+/- 4%, p > 0.05). Post-transplant hearts demonstrated reduction in systolic apical-basal (p=0.05) and lateral-septal (p=0.04) HDF when compared to controls with normal hearts (Figure 2). Post-transplant hearts also had reduction in systolic work performed by the LV (p=0.01) in comparison to controls. Interestingly, amongst transplant patients, there was no significant difference between the subgroups with active rejection versus those not being treated for rejection.



Conclusion:

Three-dimensional kinematic models of the LV could be used to measure altered HDF in pediatric transplant patients.  Further studies are needed to identify HDF and LV kinematics as potential markers for early transplant rejection and markers of overall long-term outcomes.