Abstract

Aims The 6-min walk test has been incorporated into studies on the efficacy of new therapies and into prognostic stratification for chronic heart failure patients. Firm conclusions on the usefulness of the test in clinical practice are still lacking. The aim of this study was to investigate (1) the correlation between walk test performance and standard indices of cardiac function and exercise capacity, and (2) the prognostic value of the walk test with respect to peak VdotO2and NYHA class.

Methods and Results Three hundred and fifteen chronic heart failure patients (age: 53±9 years, NYHA class: II (182), III (133)) underwent a functional evaluation and a 6-min walk test. Of these, 270 were followed-up for a minimum of 6 months (mean 387±177 days). Walked distance was 396±92m. There was no significant correlation between distance walked and central haemodynamic data. Functional capacity, as measured by ergometry, correlated moderately with distance walked (duration: r=0·48, peak VdotO2: r=0·59, anaerobic threshold: r=0·54; all P<0·001). During follow-up, 46 patients died from cardiovascular causes and 12 were urgently transplanted. Either of these events were considered end points of the study. Survival analysis was performed from a continuous walk test and peak VdotO2measurements or after categorization of (a) quartile segmentation, (b) cut-off points from the literature and (c) thresholds from receiver operating characteristic curves. At univariate survival analysis (Cox regression), the association of the walk test with survival was of significance (P=0·03, continuous variable), or borderline significance (0·05≤P≤0·1, after categorization). Peak VdotO2was always significant, indepedent of the scale used (0·005≤P≤0·03). The strongest association was found for NYHA class (P<0·001), which showed the highest sensitivity and specificity for the prediction of the event (0·64 and 0·65, respectively). When walk test performance, continuous or categorized, was entered into a multivariate model with NYHA class or peak VdotO2, it lost any significant association with survival (P>0·76 in all models with NYHA class andP >0·27 in all models with peak VdotO2).

Conclusion In moderate-to-severe chronic heart failure patients, the 6-min walk test is not related to cardiac function and only moderately related to exercise capacity. Walking performance does not provide prognostic information which can complement or substitute for that provided by peak VdotO2or NYHA class. Hence the test is of limited usefulness as a decisional indicator in clinical practice.

f1
Correspondence: Dr Cristina Opasich, Fondazione S. Maugeri, Divisione di Cardiologia, Via Ferrata 4, I-27100 Pavia, Italy.

References

1
Guyatt
GH
, Thompson PJ, Berman LB. How should we measure function in patients with chronic heart and lung disease?
J Chronic Dis
 .
1985
;
28
:
517
–524
2
Lipkin
DP
, Scriven AJ, Crake T, Poole-Wilson PA. Six minute walking test for assessing exercise capacity in chronic heart failure.
BMJ
 .
1988
;
292
:
653
–655
3
Dracup
K
, Walden JA, Stevenson LW, Brecht ML. Quality of life in patients with advanced heart failure.
J Heart and Lung Transplant
 .
1992
;
11
:
273
–279
4
Paker
M
, Gheorghiade M, Young JB. Withdrawal of digoxin from patients with chronic heart failure treated with angiotensin converting enzyme inhibitors.
N Engl J Med
 .
1993
;
329
:
1
–7
5
Uretsky
BF
, Young JB, Shahidi E, Yellen LG, Harrison MC, Jolly MK. Randomized study assessing the effect of digoxin withdrawal in patients with mild to moderate chronic congestive heart failure: results of the PROVED Trial.
J Am Coll Cardiol
 .
1993
;
22
:
955
–962
6
Califf
RM
, Adams KF, McKenna WJ. A randomized trial of epoprostenol therapy for severe congestive heart failure: The Flolan International Randomized Survival Trial (FIRST).
Am Heart J
 .
1997
;
134
:
44
–54
7
Circulation
 .
1995
;
92
:
212
–218
8
Packer
M
, Bristow ML, Cohn JN. The effect of carvedilol on morbidity and mortality in patients with chronic heart failure.
N Engl J Med
 .
1996
;
334
:
1349
–1355
9
Metra
M
, Nardi M, Giubbini R, Dei Cas L. Effects of short- and long-term carvedilol administration on rest and exercise hemodynamic variables, exercise capacity and clinical conditions in patients with idiopathic dilated cardiomyopathy.
J Am Coll Cardiol
 .
1994
;
24
:
1678
–1687
10
Krum
H
, Sackner-Bernstein JD, Goldsmith RL. Double-blind, placebo-controlled study of the long-term efficacy of carvedilol in severe chronic heart failure.
Circulation
 .
1995
;
92
:
1499
–1506
11
Olsen
SL
, Gilbert EM, Renlund DG. Carvedilol improves left ventricular function and symptoms in chronic heart failure: a double-blind randomized study.
J Am Coll Cardiol
 .
1995
;
25
:
1225
–1231
12
Meyer
K
, Scwaibold M, Westbrooh S. Effects of exercise training and activity restriction on 6-minute walking test performance in patients with chronic heart failure.
Am Heart J
 .
1997
;
133
:
447
–453
13
Bittner
V
, Weiner D, Yusuf S. Prediction of mortality and morbidity with a 6-minute walk test in patients with left ventricular dysfunction.
JAMA
 .
1993
;
270
:
1702
–1707
14
Cahalin
L
, Mathier M, Semigran M, Dec W, DiSalvo T. The six-minute walk test predicts peak oxygen uptake and survival in patients with advanced heart failure.
Chest
 .
1996
;
110
:
325
–332
15
Roul
G
, Germain P, Bareiss P. Does the 6-minute walk test predict the prognosis in patients with NYHA class II or III chronic heart failure?
Am Heart J
 .
1998
;
136
:
449
–457
16
Swedberg
K
, Califf RM, Adams K. Six minute walk test gives prognostic information in severe heart failure.
J Am Coll Cardiol
 .
1995
;
25
:
329A
17
Zugck
C
, Kruger C, Durr S. Is the 6-minute walking test a reliable substitute for peak oxygen uptake in patients with dilated cardiomyopathy?
Eur Heart J
 .
2000
;
21
:
540
–549
18
Lucas
C
, Stevenson LW, Johnson W. The 6-min walk and peak oxygen consumption in advanced heart failure: aerobic capacity and survival.
Am Heart J
 .
1999
;
138
:
618
–624
19
Bittner
V
. Determining prognosis in congestive heart failure: role of the 6-minute walk test.
Am Heart J
 .
1999
;
138
:
593
–596
20
Poole-Wilson
PA
. The 6-minute walk. A simple test with clinical application.
Eur Heart J
 .
1999
;
21
:
507
–508
21
Willenheimer
R
, Erhardt LR. Value of the 6-min walk test for assessment of severity and prognosis of heart failure.
Lancet
 .
2000
;
355
:
515
–516
22
Opasich
C
, Pinna GD, Mazza A. Reproducibility of the six-minute walking test in chronic congestive heart failure patients: practical implications.
Am J Cardiol
 .
1998
;
81
:
1497
–1500
23
Hanley
JA
, McNeil BJ. A method of comparing the areas under receiver operating characteristic curves derived from the same cases.
Radiology
 .
1983
;
148
:
839
–843
24
Parmar
MKB
, Machin D. Survival analysis. A practical approach. New York: John Wiley & Sons; 1996.
25
Costanzo
MR
, Augustine S, Bourge R, Bristow M, O'Connel JB. Selection and treatment of candidates for heart transplantation. A statement for health professionals from the committee on Heart Failure and Cardiac Transplantation of the Council on Clinical Cardiology, American Heart Association.
Circulation
 .
1995
;
92
:
3593
–3612
26
Harrington
D
, Coats A. Mechanisms of exercise intolerance in congestive heart failure.
Curr Opin in Cardiol
 .
1997
;
12
:
224
–232
27
Katz
S
, Mancini D, Jondeau G. Physiological determinants of maximal and submaximal exercise capacity in normal subjects and patients with heart failure.
Heart Failure
 .
1996
;
236
:
28
Faggiano
P
, D'Aloia A, Gualeni A, Lavatelli A, Giordano A. Assessment of oxygen uptake during the 6-minute walk test in patients with heart failure: preliminary experience with a portable device.
Am Heart J
 .
1997
;
134
:
203
–206
29
Riley
M
, McParland J, Stanford CF, Nicholls DP. Oxygen consumption during corridor walk testing in chronic cardiac failure.
Eur Heart J
 .
1992
;
13
:
789
–793
30
Foray
A
, Williams D, Reemtsma K, Oz M, Mancini D. Assessment of submaximal exercise capacity in patients with left ventricular assist devices.
Circulation
 .
1996
;
Suppl II
:
II222
–226
31
Cahalin
LP
, Semigran MJ, Dec GW. Assessment of oxygen uptake during the six-minute walk test.
Chest
 .
1997
;
111
:
1465
–1466

Comments

1 Comment
The importance of cardiopulmonary exercise testing
13 May 2010
John St.Cyr, MD, PhD (with Abe Kocherial, MD; Dean MacCarter, PhD)

E letter

The importance of cardiopulmonary exercise testing

We authors found the recent published article by Guazzi et al, entitled Six minute walk and cardiopulmonary exercise testing (CPX) in chronic heart failure: a comparative analysis on clinical and prognostic insights in Circ Heart Fail1, to have interesting implications for providing a more quantitative measure for outcomes in heart failure. Methods used in the diagnosis and assessing therapy efficacy have played a role in heart failure patients. The 6 minute walk is a common test employed to generally assess activity status in heart failure patients. However, we agree with the authors that limitations exist with this diagnostic method, including an inadequate assessment for potential mechanisms accounting for dyspnea and fatigue in these patients. Opasich et al. stated that the 6 minute walk test has limited usefulness as a decisional indicator in clinical practice.2 The use of CPX offers a more physiological assessment in measuring meaningful variables that relate to prognosis, exercise limitations and potential explanations accounting for the clinical symptoms. Further, ventilatory efficiency, a measured CPX parameter, has repeatedly shown by numerous investigations to be the most powerful and independent predictor of mortality in heart failure; and therefore, modalities directed at measuring and evaluating ventilatory efficiency should strongly be considered in treating heart failure patients.3

Cardiopulmonary exercise testing has been used for decades and continues to attract attention and interest as an important tool for its diagnostic, therapeutic and risk level assessment for patients with heart, lung and or peripheral vascular or skeletal muscle abnormalities, as reflected by clinical symptoms during exercise. The obtained measurements from CPX provide a more true evaluation of the interaction between the heart, lungs and peripheral musculature in delivering oxygen and removing carbon dioxide during exercise. Besides its use as a diagnostic, CPX has been used in assessing potential benefits of treatment options by measuring physiological parameters during either sub-maximal or symptom limited exercise.

Numerous heart failure studies have reported the benefits of using CPX in assessing heart failure patients. For example, CPX has been utilized in demonstrating both subjective and objective benefits with supplemental D-ribose in patients with heart failure.4 Dyspnea, a frequent symptom of heart failure, can be easily quantified by assessing the ventilation efficiency slope during moderate exercise. Therapies reflecting a reduction in this slope may improve clinical outcomes, including improved exercise tolerance. MacCarter et al also reported the benefits of D-ribose using CPX in chronic obstructive pulmonary disease.5 Niazi et al reported that CPX provides the means for a more succinct interpretation of AV interval optimization in heart failure patients, which clinically was reflected in improved breathing efficiency.6 These studies using CPX as an assessment tool in both normal and disease states further demonstrates the importance of this technology. With the escalating incidence of patients with heart failure, and the impact of heart failure on healthcare costs, efforts to aid in both the diagnostic capabilities and ongoing assessment of therapies in these patients must have strong consideration. Cardiopulmonary exercise testing may just provide the needed tool to accomplish this goal in not only heart failure, but also in other cardiopulmonary diseases, such as pulmonary hypertension, and in healthy individuals undergoing stressful conditions.

Abe Kocheril, MD University of Illinois College of Medicine Chicago, IL J.A. St.Cyr, MD, PhD Jacqmar, Inc. Minneapolis, MN Dean MacCarter, PhD Heart and Health: a prevention center Denver, CO

References

1 Guazzi M, Dickstein K, Vicenti M, Arena R. Six-minute walk test and cardiopulmonary exercise testing in patients with chronic heart failure: A comparative analysis on clinical and prognostic insights. Circ Heart Fail 2009;2:549-555.

2 Opasich C, Pinna GD, Mazza A, Febo O, Riccardi R, Riccardi PG, Capomolla S, Forni G, Cobelli F, Tavazzi L. Sic-minute walkinf performance in patients with moderate-to-severe heart failure; is it a useful indicator in clinical practice? Eur Heart J 2201;22(6):488-96.

3 Arena R, Myers J, Asiam SS, Varughese EB, Peberdy MA. Peak VO2 and VE/VCO2 slope in patients with heart failure. A prognostic comparison. Am Heart J 2004;147:354-360.

4 MacCarter K, Vijay N, Washam M, Shecterle L, Sierminski H, St.Cyr JA. D-ribose aids advanced ischemic heart failure patients. Int J Cardiol 2009;137:79-80.

5 MacCarter DJ, Shecterle LM, St.Cyr JA. D-ribose benefits COPD. The Internet Journal of Pulmonary Medicine 2007;7.

6 Niazi IK, MacCarter D, Unger R, Lanzaroti C, Phan N, Shanker A. Heart Rhythm J 2006;3:P6-87.

Conflict of Interest:

Dr. Kocheril uses cardiopulmonary exercise testing in his practice. Dr. MacCarter is an employee of a cardiopulmonary exercise testing company. Dr. St.Cyr has no competing interests.

Submitted on 13/05/2010 8:00 PM GMT