Transcatheter Aortic Heart Valves: Histological Analysis Providing Insight to Leaflet Thickening and Structural Valve Degeneration

JACC Cardiovasc Imaging. 2019 Jan;12(1):135-145. doi: 10.1016/j.jcmg.2018.06.028. Epub 2018 Nov 15.

Abstract

Objectives: This study investigated processes causing leaflet thickening and structural valve degeneration (SVD).

Background: Although transcatheter aortic valve replacement (TAVR) has changed the treatment of aortic stenosis, concerns remain regarding SVD, potentially related to valve thrombosis and thickening, based on studies using computed tomography (CT). Detailed histological analyses are provided to help attain insights into these processes.

Methods: Explanted transcatheter heart valves (THVs) were evaluated for thrombosis, fibrosis, and calcification for quantification of leaflet thickness. Immunohistochemical and microscopy approaches were used to investigate SVD-associated mechanisms.

Results: THVs (n = 23) were obtained from 22 patients (median 81 years of age; 50% male) from 0 to 2,583 days post TAVR. Maximal leaflet thickness increased relative to implant duration (ρ = 0.427; p = 0.027). THVs explanted after >2 years were thicker than those explanted after <2 years (p = 0.007). All THVs had adherent thrombus on both aortic and ventricular sides, which beyond 60 days was seen in combination with fibrosis and beyond 4 years had calcification. Early thrombus formation (<60 days) occurred despite rapid endothelialization with an abnormal hyperplastic phenotype. Fibrosis was observed in 6 patients on both the aortic and the ventricular THV surfaces, remodeled over time, and was associated with matrix metalloproteinase-1 expression. Five THVs showed overt calcification associated with adherent thrombus and fibrosis.

Conclusions: There is a time-dependent degeneration of THVs consisting of thrombus formation, endothelial hyperplasia, fibrosis, tissue remodeling, proteinase expression, and calcification. Future investigation is needed to further understand these mechanisms contributing to leaflet thickening and SVD.

Keywords: TAVR; leaflet thrombosis; structural valve degeneration; transcatheter heart valves.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Aortic Valve / enzymology
  • Aortic Valve / pathology*
  • Aortic Valve / surgery*
  • Calcinosis / etiology
  • Calcinosis / pathology
  • Device Removal
  • Endothelial Cells / pathology
  • Female
  • Fibrosis
  • Heart Valve Prosthesis*
  • Humans
  • Male
  • Matrix Metalloproteinase 1 / metabolism
  • Prosthesis Design
  • Prosthesis Failure*
  • Registries
  • Retrospective Studies
  • Thrombosis / etiology
  • Thrombosis / pathology
  • Time Factors
  • Transcatheter Aortic Valve Replacement / adverse effects
  • Transcatheter Aortic Valve Replacement / instrumentation*
  • Treatment Outcome

Substances

  • MMP1 protein, human
  • Matrix Metalloproteinase 1