Competition for Intrathoracic Space Reduces Lung Capacity in Patients With Chronic Heart Failure: Population Characteristics
This retrospective analysis utilized data from 44 chronic heart failure patients from the database of the Mayo Clinic Heart Failure Service or the Cardiovascular Health Clinic (a preventive and rehabilitative center) from 2000 to 2004 (Table 1). Inclusion criteria included patients with a history of ischemic or dilated cardiomyopathy, stable heart failure symptoms (> 3 months), duration of heart failure symptoms > 1 year, left ventricular EF < 35%, body mass index (BMI) < 35 kg/m2, and nonsmokers with a smoking history < 10 pack-years. Patients were treated with standard optimized medications for heart failure at the time of the study. An equal number of control participants were recruited via advertisement from the surrounding area and were matched with the heart failure group for age, gender, and height. Control participants had normal cardiac function (EF > 50%) and were without history of hypertension, lung disease, or coronary artery disease. All participants gave written informed consent after being provided a description of study requirements. The study protocol was approved by the Mayo Clinic Institutional Review Board; all procedures followed institutional and Health Insurance Portability and Accountability Act guidelines.
All participants underwent posteroanterior and lateral chest radiography. Patients with chronic heart failure were classified into two groups based on New York Heart Association (NYHA) class as follows: class I and II, n = 26 (group A), and class III and IV, n = 18 (group B). so
The posteroanterior and lateral radiographic views were used to make volumetric estimations of the total thoracic cavity (TTC), diaphragm, cardiac, and lungs based on the assumptions of a partial ellipsoid as initially described by Barnhard and colleagues and subsequently by others. This methodology has repeatedly been shown to be valid and reliable. Briefly, volumetric measures were determined by manually tracing on a digitizing tablet (AccuGrid A43BL; Numonics Corporation; Montgomeryville, PA) the innermost edge of the intrathoracic cavity and the outermost edge of the cardiac silhouette on both radiographic views with data exported to a digitizing software program (Didger 3; Golden Software; Golden, CO) on a personal computer for off-line analysis. Coordinate data obtained from the digitizing software program were used to make linear measurements for the volumetric computation.
Table 1—Differences in Participant Characteristics Between Study Groups
Characteristics | Control Group | Group A | Group B | p Value |
Patients, No. | 44 | 26 | 18 | |
Female gender, % | 43.2 | 53.9 | 33.3 | NS |
Age, yr | 56 ± 14 | 57 ± 13 | 54 ± 14 | NS |
Height, cm | 170.8 ± 9.5 | 170.6 ± 9.4 | 174.0 ± 9.8 | NS |
Weight, kg | 75.2 ± 13.1 | 81.6 ± 16.0 | 84.7 ± 13.9 | 0.06 |
BMI, kg/m2 | 25.6 ± 2.9 | 27.9 ± 4.8t | 28.2 ± 5.6t | 0.05 |
Body surface area, m2 | 1.9 ± 0.2 | 1.9 ± 0.2 | 2.0 ± 0.2 | NS |
Smoking history, pack-yr | 2.8 ± 6.9 | 2.9 ± 6.3 | CO±CCCC | NS |
Exercise history, min/wk | 168 ± 155 | GO8±36 | CO6±85 | 0.001 |
EF, % | 62.8 ± 7.8 | 30.5 ± 11.6t | 25.6 ± 10.9t | 0.001 |
NYHA class | Class In = 15, class II n = 11 | Class III n = 10, class IV n = 8 | 0.001 |