6 min Walking Test:η σημασία του στην κλινική πράξη

Καρακώστας ΓεώργιοςΔιευθυντής Καρδιολογικής Κλινικής, Γ.Ν. Κιλκίς

Definition

The 6 minute walking test (6MWT) is a

sub-maximal exercise test used to evaluate

the functional capacity in patients with

cardiovascular and pulmonary diseases.

Background

• The 6MWT was first described by Balke in 1963, mostly to evaluatethe exercise capacity in healthy populations.

• For years it was used to evaluate patients with chronic respiratorydiseases.

• Guyatt in 1985 and Lipkin in 1986 reported that the 6MWT canidentify the most compromised patients suffering from heartfailure.

• Bittner in 1993 reported that the distance walked during the6MWT is a strong and independent predictor of mortality andmorbidity in patients with left ventricular dysfunction.

Indications Evaluation of functional capacity Chronic obstructive pulmonary disease Heart failure Cystic fibrosis Peripheral vascular disease Older subjects

Evaluation of effects of therapeutic interventions Chronic obstructive pulmonary disease Heart failure Lung resection Lung volume reduction surgery Pulmonary rehabilitation Pulmonary hypertension

Prognostic stratification Heart failure Chronic obstructive pulmonary disease Primary pulmonary hypertension

Contraindications for walking tests (1) Absolute Acute myocardial myocardial infarction (3-5 days)

Unstable Angina

Exercise induced uncontrolled arrythmias

Active endocarditis, Acute myocarditis or pericarditis

Uncontrolled heart failure and pulmonary oedema

Acute pulmonary embolus

Thrombosis of lower extremeties

Suspected dissecting aneurysm

Acute respiratory failure

Acute non cardiopulmonary disorder that may affect exercise performance or be aggravated by exercise (i.e. infection, renal failure, thyrotoxicosis)

Mental impairment leading to inability to cooparate

Contraindications for walking tests (2)

Relative Resting heart rate > 120 bpm

Systolic blood pressure > 180 mmHg

Diastolic blood pressure > 100 mmHg

Left main coronary stenosis or its equivalent

Severe aortic stenosis

Tachyarrhythmias or Bradyarrhythmias

Advanced pregnancy

Severe orthopaedic impairment that prevents walking

ERS/ATS (2014)

Indentifying a space for the 6MWT• A 30 meters long corridor, straight, with no obstacles with a level

floor.

• The space should be quiet enough for the participant to clearlyhear your instructions.

• Any clock or timers should not be visible to the participant.

• A chair should be available for the participant to test during orafter the test.

• There should be easy access to a telephone and appropriateequipment in case of emergency. The person administrating thetest is not necessarily a physician, but he should be trained inbasic life support.

Required Equipment

• Two cones to mark the turning points at the either end

• Stopwatch or countdown timer

• Measuring tape

• Pen and paper

Before the test

• The participant should wear comfortable clothing and appropriate footwear.

• He should continue with his normal medical treatment.

• If he usually walks with an aid, he should use it during the test.

• If he usually uses a GTN spray, chronic oxygen or any other inhaler, he should have them with him and use them during the test if necessary.

Instructions• The text approved by the ATS is the following:

“The object of this test is to walk as far as possible for 6 minutes. You

will walk back and forth in this hallway. Six minutes is a long time to

walk, so you will be exerting yourself. You will probably get out of

breath or become exhausted. You are permitted to slow down, to stop,

and to rest as necessary. You may lean against the wall while resting,

but resume walking as soon as you are able. You will be walking back

and forth around the cones. You should pivot briskly around the cones

and continue back the other way without hesitation. Now I’m going to

show you. Please watch the way I turn without hesitation. Remember

that the object is to walk AS FAR AS POSSIBLE for 6 minutes, but don’t

run or jog. Start now, or whenever you are ready.”ATS 2002

Performing the 6MWT

• Set the timer to 6 minutes.

• Demonstrate by walking one lap yourself.

• Start the timer as soon as the participant starts walking

• Record the number of laps.

• Record the additional distance walked from the final

partial lap.

• Calculate the total distance.

Reasons for immediate stopping

• Chest pain

• Intolerable dyspnea

• Leg cramps

• Staggering

• Diaphoresis

• Pale or ashen appearance

ATS 2002

Encouragement

• Encouragement significantly increases the distance

walked.

• Participants are told when 2, 4, and 6 minutes have

elapsed.

• Words like ‘‘keep up the good work’’ or ‘‘you’re doing

fine’’ are provided with even voice at 1 minute

intervals.

Can Med Assoc J. 1985 ; 132(8): 919–923.

Reproducibility• The degree of reproducibility of a diagnostic or prognostic

indicator is one of the factors that can determine its use in clinical practice.

CLINICS 2008;63(2):201-6

The Borg Scale

• The Borg Scale is a frequently used quantitative measure of

perceived exertion during physical activity.

•The participant is asked to grade his level of shortness of

breath and of fatigue.

Borg G. Borg’s Perceived Exertion and Pan Scales. Champaign, IL: Human Kinetics, 1998.

Advantages of the method

• Easy to administer

• Easy to repeat

• Does not require expensive equipment

• Does not require advanced training for technicians

• Has a good correlation with objective measures of effort

tolerance, such as oxygen uptake at the peak of exercise

• Well tolerated because it is similar to the activities of

daily living

Limitations of the method

• Does not determine peak oxygen uptake

• Does not provide specific information on the function of

each of the different organs and systems involved in

exercise

• Does not diagnose the cause of dyspnea on exertion

• Does not evaluate the causes or mechanisms of exercise

limitation

• Results can be affected by a number of factors ATS 2002

6MWT sources of Variability (1)

Factors reducing the 6MWT :

Shorter height

Older age

Higher body weight

Female sex

Impaired cognition

A shorter corridor

Pulmonary disease

Cardiovascular disease

Musculoskeletal disorders

6MWT sources of Variability (2)

Factors increasing the 6MWT :

Taller height

Male sex

Encouragement

A patient who has previously performed the test

Medication for a disabling disease taken just before the test

Oxygen supplementation in patients with exercise-induced hypoxemia

Normal values

AM J RESPIR CRIT CARE MED 1998;158:1384–1387

6MWT

• Evaluation of functional capacity

• Evaluation of effects of therapeutic interventions

• Prognostic stratification

Correlation of 6MWT and NYHA Functional class in PPH

Am J Respir Crit Care Med. 2000;161(2,pt 1):487-492

Am Heart J 1997;133:447– 53.

Variation in distancewalked during the 6MWTat baseline, after threeweeks of physical trainingand after three weeks ofactivity restriction in agroup of patients withstable heart failure.

Change in 6MWT distance with common treatments

in COPD from randomized controlled trials

• ICS, inhaled corticosteroids; LABA, long-acting beta agonist; LVRS, lung volume reduction surgery; PRehab, Pulmonary Rehabilitation; SABA, short-acting beta agonist.

• *P < 0.05 versus control.

Internal Medicine Journal 2009;39: 495–501

Change in 6MWT distance with common treatments

in heart failure from randomized controlled trials

• BB, beta-adrenergic blockers; CPAP, continuous positive airway pressure; CRT, cardiac resynchronisationtherapy• *P < 0.05 versus control

Internal Medicine Journal 2009;39: 495–501

Effects of therapeutic interventions on 6MWT

o The dashed line shows thevariations of distance walkedduring 6MWT observed inpatients with stable heart failurein whom drug dosages wereunchanged in short-term.

o The continuous line shows thebehavior of distance walked inheart failure patients in whomdosages of diuretics andvasodilators have been graduallyincreased as tolerated.

Am J Cardiol 1998;81:1370– 2.

• The PAVE trial prospectively compared chronic biventricular pacing to rightventricular pacing in patients undergoing ablation of the AV node for managementof atrial fibrillation with rapid ventricular rates.

• The results are most positive in those with low EFs. There is very little differencein those with preserved LV function.

≤

J Cardiovasc Electrophysiol. 2005 ;16:1160-5

Galie N, Ghofrani HA, Torbicki A, et al. N Engl J Med 2005; 353:2148-57.

REVATIO: SUPER- 16-Minute Walk Distance

Galiè N et al. Circulation 2009;119:2894-2903

TADALAFIL: PHIRST6-Minute Walk Distance

PlaceboTadalafil 2.5 mgTadalafil 10 mgTadalafil 20 mgTadalafil 40 mg

70

60

50

40

30

20

10

0

4 8 12 160

Ch

ange

in 6

MW

D (

m)

Weeks

p<0.001

p<0.05

p<0.05

RIOCIGUAT: PATENT-16-Minute Walk Distance

Ghofrani HA et al. N Engl J Med 2013;369:330-40.

+36 m

VOLIBRIS: ARIES 1&26-Minute Walk Distance

p vs placebo

20

0

10

30

40

50

60

70

80 +45p<0.001

+53p<0.001

5 mg 10 mg

Συνδυασμένη δόση ambrisentan

Pla

ceb

o-c

orr

ect

ed

6

MW

D (

me

tre

s)

Galiè N et al Circulation 2008;117:3010-3019

MACITENTAN: SERAPHIN6-Minute Walk Distance

Macitentan 3 mg Macitentan 10 mg

Placebo-corrected change in 6MWD from baseline at Month 6

Baseline-adjusted meanOverallFC I/IIFC III/IV

18 m [-2, 37]6 m [-19, 32]33 m [2, 63]

p = 0.04p = 0.58p = 0.02

23 m [4, 42]12 m [-8, 33]37 m [5, 69]

p < 0.01p = 0.18p < 0.01

[Confidence limits 97.5%]

Pulido T, et al. N Engl J Med 2013; 369: 809-18.Pulido T, et al. N Engl J Med 2013; 369: 809-18.Pulido T, et al. N Engl J Med 2013; 369: 809-18.

Median change in 6MWD (m) from baseline

Vertical bars represent 95% CIs. Stratified Wilcoxon Rank Sum analysis. Worst rank scores were used for missing data following death or adjudicated hospitalisation; otherwise, LOCF imputation was used.

Week 24Combination: +49.0m

Pooled mono: +23.8m (p<0.001)

Ambrisentan mono: +27.0m (p<0.001)

Tadalafil mono: +22.7m (p=0.003)

Med

ian

ch

ange

fro

m b

asel

ine

(m)

Time (weeks)

AMBRISENTAN&TADALAFIL: AMBITION STUDY 6MWD: change from baseline to week 24

Primary Analysis Set

N. Galiè, et al. N Engl J Med 2015;373:834-44

Prognostic value of 6MWT

European Heart Journal 2007;28:560-568

Kaplan-Meier curveshowing survival basedon 6MWT distance inolder patients with CHF.

European Heart Journal 2007;28:560-568

Risk of death at 24months based on6MWT in patientswith > mild LVSD.

Am J Respir Crit Care Med. 2000;161(2,pt 1):487-492

J Heart Lung Transplant 2015;34:362–368

Kaplan-Meier survival estimates based on absolute 6MWT distance thresholds at165 m and 440 m, and all possible 6MWD thresholds.

Patients with PAH

The 6MWT distance & resting SO2 predict outcomein adult patients with Eisenmenger syndrome

International Journal of Cardiology 2013;168:4784–4789

Predicted survival at 3-years