Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2014 Mar 19;9(3):e92324.
doi: 10.1371/journal.pone.0092324. eCollection 2014.

Maximal cardiac output determines 6 minutes walking distance in pulmonary hypertension

Gaël Deboeck  1 , Dolores Taboada  2 , Guy Hagan  2 , Carmen Treacy  2 , Kathy Page  2 , Karen Sheares  2 , Robert Naeije  3 , Joanna Pepke-Zaba  2
Affiliations

Maximal cardiac output determines 6 minutes walking distance in pulmonary hypertension

Gaël Deboeck et al. PLoS One. .

Abstract

Purpose: The 6 minutes walk test (6MWT) is often shown to be the best predictor of mortality in pulmonary hypertension (PH) probably because it challenges the failing heart to deliver adequate cardiac output. We hypothesised that the 6MWT elicits maximal cardiac output as measured during a maximal cardiopulmonary exercise testing (CPET).

Methods: 18 patients with chronic thromboembolic pulmonary hypertension (n = 12) or pulmonary arterial hypertension (n = 6) and 10 healthy subjects performed a 6MWT and CPET with measurements of cardiac output (non invasive rebreathing device) before and directly after exercise. Heart rate was measured during 6MWT with a cardiofrequence meter.

Results: Cardiac output and heart rate measured at the end of the 6MWT were linearly related to 6MW distance (mean±SD: 490±87 m). Patients with a high NT-pro-BNP achieve a maximum cardiac output during the 6MWT, while in normal subjects and in patients with a low-normal NT-proBNP, cardiac output at the end of a 6MWT was lower than achieved at maximum exercise during a CPET. In both cases, heart rate is the major determinant of exercise-induced increase in cardiac output. However, stroke volume increased during CPET in healthy subjects, not in PH patients.

Conclusion: Maximal cardiac output is elicited by 6MWT in PH patients with failing right ventricle. Cardiac output increase is dependent on chronotropic response in patients with PH.

PubMed Disclaimer

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Cardiac output response to a 6MWT in relation with the 6MWD in 21 healthy subjects and 18 pulmonary hypertension patients.
Figure 2
Figure 2. Cardiac output measured at rest, after 3 minutes of unloaded cycling and at directly after the end of maximal CPET in 18 pulmonary hypertension patients (stripped line) and 10 healthy subjects (solid line).
Figure 3
Figure 3. Stroke volume calculated at rest, after 3 minutes of unloaded cycling and directly after the end of maximal CPET in 18 pulmonary hypertension patients (stripped line) and 10 healthy subjects (solid line).
Figure 4
Figure 4. Cardiac output measured directly after the end of a 6MWT and of a CPET in 18 pulmonary hypertension patients and 10 healthy subjects.
(-) Line of identity (where CO6MWT = COCPET).
Figure 5
Figure 5. Stroke volume calculated directly after the end of a 6MWT and of a CPET in 12 pulmonary hypertension patients and 7 healthy subjects.
(-) Line of identity (where SV6MWT = SVCPET).
Figure 6
Figure 6. Difference between cardiac output measured at the end of a CPET and of a 6MWT in relation with Ntpro-BNP level in % of the highest negative predictive value for age in 18 PH patients (* indicate patients with high creatinine level).
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Hoeper MM, Bogaard HJ, Condliffe R, Frantz R, Khanna D, et al. (2013) Definitions and diagnosis of pulmonary hypertension. J Am Coll Cardiol 62: D42–50. - PubMed
    1. Stringer W, Hansen J, Wasserman K (1997) Cardiac Output estimated non-invsively from oxygen uptake (VO2) during exercise. J Appl Physiol 1997 82: 908–912. - PubMed
    1. Naeije R (2010) The 6-min walk distance in pulmonary arterial hypertension: “Je t'aime, moi non plus”. Chest 137: 1258–60. - PubMed
    1. Mainguy V, Malenfant S, Neyron AS, Bonnet S, Maltais F, et al. (2013) Repeatability and responsiveness of exercise tests in pulmonary arterial hypertension. Eur Resp J 42: 425–434. - PubMed
    1. Sitbon O, Humbert M, Nunes H, Parent F, Garcia G, et al. (2002) Long-term intravenous epoprostenol infusion in primary pulmonary hypertension: prognostic factors and survival. J Am Coll Cardiol. 40: 780–788. - PubMed

Publication types