Y. NING1, M. Fahrenholtz1, K. Brown2, E. Steen1, M. Kang2, L. Masri1, L. Wadhwa1, S. Balaji1, K. Grande-Allen2, S. Keswani1 1Texas Children’s Hospital,Pediatrics,Houston, TX, USA 2Rice University,Bioengineering,Houston, TX, USA
Introduction:
Discrete subaortic stenosis (DSS) features the formation of an obstructive fibrous tissue lesion in the left ventricular outflow tract, and while the standard of care is surgical resection, lesions recur in 25-30% of all patients, delineating an “aggressive” phenotype. Here, we define unique histologic parameters that discriminate non-aggressive from aggressive DSS lesions and are consistent with preoperative LVOT gradients, which are known prognostic signs of recurrence.
Methods:
Human DSS patient tissues (n=7) were obtained from the TCH Congenital Heart Biorepository in accordance with IRB protocols. We compared tissue samples from 4 non-aggressive and 3 aggressive recurrent lesions from DSS patients by immunohistochemical staining of cardiac fibroblast DDR2. Next, cell density (H&E), mature/immature collagen ratio (Herovici), and percent DDR2+ cells/HPF were quantified. Lastly, each variable tested was normalized to the ranged set and then combined to generate a DSS aggressiveness score (DAS). Preoperative echocardiographic reports were obtained for all DSS patients whose tissues were analyzed and assessed for mean LVOT gradient. Data was reported as mean ± standard deviation. Statistical analysis was performed using Student’s t-test in which p ≤ 0.05 values were considered significant.
Results:
A differential DDR2 staining was observed between non-aggressive tissues (36.3±27.4% positive/field area) and aggressive tissues, which had almost no measurable expression of DDR2 (1.94±1.90%, p < 0.05). DSS tissues stained by H&E showed significant differences in cell density between aggressive (130±28 cells/image field) and non-aggressive lesions (50±15 cells/field; p < 0.01). Although we observed high variability in both groups, aggressive tissues had increased immature to mature collagen ratios in comparison to non-aggressive ones. Qualitatively, aggressive tissues were more likely to have thin, highly disorganized collagen bundles, whereas non-aggressive tissues had more and thicker collagen bundles. Overall, there was a significant DAS difference between aggressive and non-aggressive tissues (1.94 ±0.46 vs 0.59 ±0.48, p < 0.01) in which the score correlated with the recurrence prediction based on LVOT gradient. Our scoring model will be validated by larger patient sample cohorts.
Conclusion:
Our data underscore histologic features that discriminate aggressive from non-aggressive DSS tissues, which can be quantitatively converted to produce score values that correlate with known predictors of recurrence. This score system may provide a useful means to improve monitoring of aggressive DSS patients.