Novel Descriptors of Coronary Wall Properties Measured by OCT at Baseline Are Associated with CAV-Related Intimal Thickening One Year after Heart Transplant

Purpose Cardiac Allograft Vasculopathy (CAV) is a frequent complication of heart transplantation (HTx). To help identify patients at risk of cardiac graft failure, early determination of coronary wall thickening is of major importance. Using highly automated 3D segmentation of coronary wall layers, novel indices of intimal and medial roughness are reported. Ability of these indices obtained at 1 month (1M) to predict intimal thickening 12 months (12M) after HTx was studied. Methods Lumen surface, intimal and media layers (as depicted by OCT) were identified using our multi-surface graph-based LOGISMOS segmentation method, reported earlier. Automated results were adjusted by experts utilizing our Just-Enough-Interaction approach. Intimal thickness (IT) was determined for each image frame of the OCT pullback obtained 1M and 12M after HTx. CAV risk was quantified as average OCT-frame-specific intimal thickening (IT12M - IT1M) after 1M—12M image registration. Intimal (medial) roughness IR (MR), reflecting the circumferential variability of the intimal (medial) outer surface, was computed as the average distance between the thin-plate spline fitted to the intimal (medial) surface and the regional peaks of individual surface points. As such, smooth (rough) intimal or medial surface would be represented by small (large) IR or MR values. Results Associations between frame-based IR or MR at 1M and frame-based IT progression were studied in 116 patients for which 1M and 12M OCT pullbacks (538 frames each) were acquired. Mixed effect analysis with individual patient as grouping factor was employed. IR and MR determined at 1M were strongly associated with IT progression 12M after HTx (IR: β=-9.49, p=0.004; MR: β=-9.76, p=0.001). In a patient-level analysis using Pearson's correlation test, the negative association was further confirmed between 1M roughness and IT progression in the per-patient-most-progressing 3 mm-long vessel segment (IR: R=-0.28, p=0.002; MR: R=-0.28, p=0.002). Conclusion Our new descriptors of intimal and medial roughness derived from fully 3D segmentation of coronary wall layers in OCT image pullbacks 1 month after HTx were associated with CAV-related progression of intimal thickness at 12 months. As such, IR and MR indices showed CAV-onset prediction ability as early as 1 month after HTx.