mitralization

[mī′trə-lĭ-zāshən]
n.
  1. A straightening of the left heart border in a chest x-ray because of increased prominence of the convexity formed by the main pulmonary artery and its left main branch or the left atrial appendage or both.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.