title: Competition for intrathoracic space reduces lung capacity in patients with chronic heart failure: a radiographic study.
abstract: BACKGROUND
  The purpose of this study was to determine the influence of changes in cardiac size on total lung volume in patients with chronic heart failure compared to control subjects.
  
  
  METHODS
  Forty-four patients and age-, gender-, and height-matched control participants were recruited. All participants underwent posteroanterior and lateral chest radiography for volumetric estimations of the total thoracic cavity (TTC), diaphragm, heart, and lungs. To assess the relationship between chronic heart failure severity and cardiac enlargement, patients with chronic heart failure were classified into groups based on New York Heart Association class, as follows: class I and II, n = 26 (group A); class III and IV, n = 18 (group B).
  
  
  RESULTS
  There was no difference between the groups for TTC volume (TTCV) [p = 0.56]. Cardiac volumes were significantly different between all groups for both the absolute volumes (p < 0.001) were calculated as a percentage of TTCV (p < 0.001), with the largest cardiac volumes in group B (twice the volume of healthy control subjects). When expressed as a percentage of TTCV, there also was a clear reduction in lung volumes as a function of disease severity (p < 0.001).
  
  
  CONCLUSIONS
  The present study demonstrates a close relationship between the severity of heart failure and cardiac size. These changes in cardiac size within a closed thoracic cavity may pose significant constraints on the lungs, resulting in reductions in lung volumes that likely play a major role in the restrictive breathing patterns often reported in patients with chronic heart failure.
authors.affiliation: Division of Cardiovascular Diseases, Department of Internal Medicine, Gonda 5-369, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Olson
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Beck
authors.forename: Jacob B
authors.initials: JB
authors.lastname: Johnson
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Johnson
mesh_terms: D006332:Cardiomegaly / Q000145:classification* / Q000000981:diagnostic imaging; D005260:Female; D006333:Heart Failure / Q000145:classification* / Q000000981:diagnostic imaging; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D013902:Radiography, Thoracic; D012720:Severity of Illness Index