flat waist sign

A flattening of the left cardiac border due to rotation of the heart in atelectasis of the left lower lobe
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

flat waist sign

Imaging A loss of concavity of the left cardiac border, seen on a plain AP chest film, which corresponds to a slight anterior, right and oblique rotation of the heart, seen in left lower lobe collapse of the lung.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.