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Although cardiopulmonary exercise testing (CPET)
is discussed in the ACCP chapter, the actual recommendation
is really for 6- minute walk testing. Dr Oudiz, how do
feel about this? Would CPET be a better endpoint for clinical
trials?
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 Ronald
J. Oudiz, MD
Associate Professor of Medicine, UCLA School
of Medicine
Director, Liu Center for Pulmonary Hypertension
Division of Cardiology, Harbor-UCLA Medical Center
Torrance, California
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I believe that both the ACCP recommendations1
and the proceedings of the 2003 Venice consensus meeting2
have predominantly relied on the 6-minute walk test as
the exercise test of choice, mostly because it has been
the endpoint used in nearly all of the recent multicenter
trials of PAH treatments. The most recent multicenter
therapeutic trial using CPET as the primary endpoint was
the STRIDE 1 (sitaxsentan) trial.3 Oddly
enough, CPET did not perform as well as an endpoint as
did its surrogate, the 6-minute walk test. One question
that we are addressing is why the surrogate outperformed
CPET. We suspect that the answer is related to inexperience
in interpretation of the CPET studies (in patients with
PAH) at the individual study sites and/or the fact that
a core CPET lab was not used. Going forward, as newer
therapies and strategies for combination therapies are
being considered, the pulmonary hypertension community
is aware of the need for a better, perhaps more sensitive
endpoint than the 6-minute walk test as a useful clinical
marker of disease severity, mainly to better assess response
to therapy in clinical trials. I believe that CPET can
be useful in this regard, in that it provides physiologic
data regarding disease severity,4,5 the
mechanism of improvement (or deterioration) in response
to therapeutic interventions,6 as well
as prognostic data.4,5
How often should the 6-minute walk or other exercise
testing be performed?
We generally have patients undergo exercise testing at
all regular follow-up visits. We do both 6-minute walk
tests and CPET. Unless there is a clinical change, we
do not do CPET more often than twice a year. If there
is a change in clinical status in the interim, we often
do CPET to confirm the change and determine its physiologic
nature.
References
McGoon M, Gutterman D, Steen V, Barst
R, McCrory DC, Fortin TA, Loyd JE; American College of
Chest Physicians. Screening, early detection, and diagnosis
of pulmonary arterial hypertension: ACCP evidencebased
clinical practice guidelines. Chest. 2004;126:14S-34S.
Hoeper MM, Oudiz RJ, Peacock A, Tapson
VF, Haworth SG, Frost AE, Torbicki A. End points and clinical
trial designs in pulmonary arterial hypertension: clinical
and regulatory perspectives. J Am Coll Cardiol. 2004;43:S48-S55.
3. Barst RJ, Langleben D, Frost A, Horn
EM, Oudiz R, Shapiro S, McLaughlin V, Hill N, Tapson VF,
Robbins IM, Zwicke D, Duncan B, Dixon RA, Frumkin LR.
Sitaxsentan therapy for pulmonary arterial hypertension.
Am J Respir Crit Care Med. 2004;169:441-7.
4. Wensel R, Opitz C, Anker SD, et al.
Assessment of survival in patients with primary pulmonary
hypertension: importance of cardiopulmonary exercise testing.
Circulation. 2002;106:319-24.
5. Sun X-G, Oudiz RJ, Hansen, JE, Wasserman,
K. Exercise pathophysiology in primary pulmonary vascular
hypertension. Circulation. 104:429-35, 2001.
6. Hoeper MM, Taha N, Bekjarova A, Gatzke
R, Spiekerkoetter E. Bosentan treatment in patients with
primary pulmonary hypertension receiving nonparenteral
prostanoids. Eur Respir J. 2003;22:330-4.
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