title: Echocardiographic predictors of exercise capacity and mortality in chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Chronic obstructive pulmonary disease (COPD) reduces exercise capacity, but lung function parameters do not fully explain functional class and lung-heart interaction could be the explanation. We evaluated echocardiographic predictors of mortality and six minutes walking distance (6MWD), a marker for quality of life and mortality in COPD.
  
  
  METHODS
  Ninety COPD patients (GOLD criteria) were evaluated by body plethysmography, 6MWD and advanced echocardiography parameters (pulsed wave tissue Doppler and speckle tracking).
  
  
  RESULTS
  Mean 6MWD was 403 (± 113) meters. All 90 subjects had preserved left ventricular (LV) ejection fraction 64.3% ± 8.6%. Stroke volume decreased while heart rate increased with COPD severity and hyperinflation. In 66% of patients, some degree of diastolic dysfunction was present. Mitral tissue Doppler data in COPD could be interpreted as a sign of low LV preload and not necessarily an intrinsic impairment in LV relaxation/compliance. Tricuspid regurgitation (TR) increased with COPD severity and hyperinflation. Age (p < 0.001), BMI (p < 0.001), DLCO SB (p < 0.001) and TR (p 0.005) were independent predictors of 6MWD and a multivariable model incorporating heart function parameters (adjusted r2 = .511) compared well to a model with lung function parameters alone (adjusted r2 = .475). LV global longitudinal strain (p = 0.034) was the only independent predictor of mortality among all baseline, body plethysmographic and echocardiographic variables.
  
  
  CONCLUSIONS
  Among subjects with moderate to severe COPD and normal LVEF, GLS independently predicted all-cause mortality. Exercise tolerance correlated with standard lung function parameters only in univariate models; in subsequent models including echocardiographic parameters, longer 6MWD correlated independently with milder TR, better DLCO SB, younger age and lower BMI. We extended the evidence on COPD affecting cardiac chamber volumes, LV preload, heart rate, as well as systolic and diastolic function. Our results highlight lung-heart interaction and the necessity of cardiac evaluation in COPD.
authors.affiliation: Department of Cardiology, Rigshospitalet, University Hospital Copenhagen, Blegdamsvej 9, 2100 Copenhagen, Denmark. mikkel.schoos@gmail.com.
authors.forename: Mikkel Malby
authors.initials: MM
authors.lastname: Schoos
authors.forename: Morten
authors.initials: M
authors.lastname: Dalsgaard
authors.forename: Jesper
authors.initials: J
authors.lastname: Kjærgaard
authors.forename: Dorte
authors.initials: D
authors.lastname: Moesby
authors.forename: Sidse Graff
authors.initials: SG
authors.lastname: Jensen
authors.forename: Ida
authors.initials: I
authors.lastname: Steffensen
authors.forename: Kasper Karmark
authors.initials: KK
authors.lastname: Iversen
mesh_terms: D000368:Aged; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D015150:Echocardiography, Doppler / Q000379:methods; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging* / Q000401:mortality* / Q000503:physiopathology; D016037:Single-Blind Method; D013318:Stroke Volume / Q000502:physiology