|
Task Force on Diagnosis and
Assessment: Identifying the Most Useful Tools
 Robyn
J. Barst, MD
New York Presbyterian Pulmonary Hypertension Center,
Columbia University College of Physicians and Surgeons,New
York, New York
A diagnostic algorithm that is accepted among experienced
centers (Pull-Out, next page)
can guide the evaluation of pulmonary hypertension. Like
all guidelines, the algorithm may be modified according
to specific clinical circumstances. Most patients are
diagnosed as the result of an evaluation of symptoms,
while others are diagnosed during screening of asymptomatic
populations at risk. Symptomatic patients should be managed
with an aggressive therapeutic strategy to reduce symptoms,
improve hemodynamics, and prolong survival. Asymptomatic
or incidentally discovered subjects should be managed
with conservative treatment (depending on the severity
of the hemodynamic abnormality), identification of reversible
underlying causes, and close monitoring for progression.
A high level of suspicion is of paramount importance
for the diagnosis of pulmonary hypertension regardless
of underlying cause. Once suspect, a methodical workup
using commonly employed diagnostic interventions allows
confirmation of the presence of pulmonary hypertension
and elucidation of its etiology. Clarification of etiology
is necessary to ensure that the proper therapeutic interventions
are implemented.
In patients with a suspicion of, or risk of, pulmonary
arterial hypertension (PAH), the physical examination
should be performed to assist in directing further evaluation
to more specific and efficient assessment for defining
the presence, severity and substrate of PAH. In addition,
an ECG should be performed to screen for a spectrum of
cardiac and arrhythmic problems. Although an ECG lacks
sufficient sensitivity to serve as an effective screening
tool for PAH, it does contribute some prognostic information
in patients with known idiopathic PAH. A chest Xray should
also be obtained to reveal features supportive of a diagnosis
of PAH and lead to diagnoses of underlying diseases.
Doppler echocardiography should be performed as an appropriate
and useful screening tool to detect clinically significant
degrees of elevated pulmonary pressure, although in some
patients it may be imprecise in determining actual pressures
(compared with invasive evaluation). In patients with
high-risk substrates, eg, systemic sclerosis, family history
of idiopathic PAH, known genetic predisposition, Doppler
echocardiography should be performed periodically, ie,
every 1 to 3 years, to screen for possible development
of clinically significant degrees of elevated pulmonary
pressure. Doppler echocardiography should also be obtained
in patients with suspected or documented pulmonary hypertension
to look for left ventricular systolic and diastolic dysfunction,
left-sided chamber enlargement, or valvular heart disease,
any of which may cause or contribute to pulmonary hypertension
and may be treatable. A contrast study during Doppler
echocardiography is also useful to look for evidence of
intracardiac shunting.
Screening for connective tissue disease and HIV infection
by serologic testing (along with appropriate history and
physical examination) should also be performed in patients
with suspected or documented pulmonary hypertension. A
ventilation-perfusion lung scan should be performed to
rule out chronic thromboembolic pulmonary hypertension;
a negative scan effectively excludes a diagnosis of chronic
thromboembolic pulmonary hypertension. Contrast-enhanced
computed chest tomography or magnetic resonance imaging
can provide useful morphologic information, but should
not be relied upon to unequivocally exclude chronic thromboembolic
pulmonary hypertension. In patients with a V/Q scan suggestive
of chronic thromboembolic pulmonary hypertension, pulmonary
angiography is required for accurate diagnosis and best
anatomic definition. Contrast enhanced computed chest
tomography or magnetic resonance imaging can be obtained
to provide complementary morphologic, functional and prognostic
information.
Pulmonary function testing and arterial blood gas measurements
should be performed to evaluate potentially contributory
ventilatory factors and diffusion abnormalities. In patients
with systemic sclerosis, pulmonary function testing should
be performed periodically, ie, every 6 to 12 months, to
detect deteriorating DLCO as a sign of progressive pulmonary
vasculopathy.
Lung biopsy is not recommended because of the risk in
patients with suspected or documented pulmonary hypertension,
except under circumstances in which a specific question
can be answered only by tissue examination. Finally, right
heart catheterization is required in patients with suspected
pulmonary hypertension to establish the diagnosis of pulmonary
hypertension and document pulmonary hemodynamics. Furthermore,
prior to initiation of medical therapy, assessment of
vasodilating capacity (during the right heart catheterization)
is required to determine the appropriate therapy for an
individual patient.
Techniques that have recently been evaluated to predict
disease severity include: assessment of right ventricular
function, using Doppler echocardiographic semi-quantitative
indices, functional class, exercise testing, ie, exercise
endurance assessed by a 6-minute walk test and exercise
tolerance assessed with cardiopulmonary exercise testing,
and demographic and hemodynamic parameters. Neurohormone
levels, such as BNP and ANP, have recently been demonstrated
to correlate with survival, and norepinephrine and endothelin-1
levels also appear to be useful parameters of disease
severity. In addition, uric acid levels have been reported
to correlate with the severity of PAH.
Some of these modalities may provide prognostic information
that is similar to that derived from invasive tests and
may be more useful and convenient in assessing treatment
efficacyover time. These newer tools may also enhance
predictive accuracy when used in combination with the
“standard” testing modalities. Many of these variables
have been shown to correlate with one another; thus, which
parameters will prove to be the most useful in assessing
disease severity requires further investigation. Importantly,
all of the above studies evaluated idiopathic PAH patients
but not patients with PAH related to connective tissue
disease, congenital heart disease, anorexigens, HIV infection,
or portal hypertension. Thus, these parameters must be
applied cautiously to PAH patients in whom comorbid factors
may contribute significantly to overall outcome, eg, in
general, patients with PAH related to connective tissue
disease have a worse prognosis than idiopathic PAH patients,
whereas patients with PAH related to congenital heart
disease have a much more slowly progressive course than
do patients with idiopathic PAH.
In conclusion, PAH is diagnosed by following a careful
series of investigations that include tests that are regarded
as essential in making the diagnosis, as well as additional
tests that may help clarify the category of pulmonary
hypertension present. Disease severity can be evaluated
by several modalities that are complementary and that
together are useful in helping to choose therapy and evaluate
the response to therapy. Close follow-up at a center specializing
in pulmonary hypertension is recommended, with careful
monitoring at frequent intervals of the course of the
disease.
|
