excerpted from
chapter 1 of Pulmonary
Hypertension: A Patient's Survival Guide - Third Edition
The following are typical approaches used by PH specialists,
but the diagnostic procedure will vary from doctor to doctor.
Physical exam. A routine checkup seldom discovers PH,
so it often goes undiagnosed. Because the symptoms of PH are common
to many diseases, personal and family medical histories are important.
Your doctor will use a stethoscope to listen for unusual heart
sounds such as an increase in the pulmonic component of the second
heart sound (the sound the pulmonic valve makes when it snaps
shut), an ejection click, systolic murmurs (whooshing sounds due
to the leakage of blood backwards across the tricuspid valve),
and for a gallop (a soft thud during the time the right ventricle
is filling, which indicates that ventricle is weak). Okay, this
is pretty technical stuff, but a patient who asks, “Hey,
doc, hear a systolic murmur?” is more likely to be treated
as an intelligent participant in his or her own medical treatment.
Your doctor will also feel for a right ventricular or parasternal
lift, for an enlarged (or even throbbing) liver, and for fluid
in your abdomen (ascites). Your ankles and lower legs will be
checked for swelling (edema), and the jugular vein in your neck
examined for swelling. The doctor will probably look at your fingers,
because a long period of low concentrations of oxygen in the blood
sometimes causes nail beds to take on a bluish tint ( cyanosis)
or fingers to form a small bulge at the end (clubbing).
Electrocardiogram (ECG). This is one of the first tests
done on a potential PH patient. Electrodes are stuck to your skin
and a recording is made of the electrical impulses of your heart.
The results may indicate that the right side of the heart is thickened
due to the unusual stress of high pressure, but an ECG cannot,
by itself, diagnose PH. You may be asked to take an ECG stress
test, where you pedal a stationary bike or walk on a treadmill
while you are hooked up to an ECG machine. There is a very small
risk of a heart attack or serious rhythm problem during such a
test, but trained people stand by ready to handle such emergencies
(if your doctor thinks you’ll have such problems, he/she
won’t order the test). There’s a whole science to reading
ECGs, so we won’t attempt to explain the peaks and valleys
in these jittery lines.
Blood tests are done to check on how much oxygen there
is in your blood (arterial blood gases), how your liver and kidneys
are functioning (back pressure or limited cardiac output from
severe PH can hurt them), and to find whether you have collagen
vascular disease (like lupus or scleroderma—more on this
later), thyroid problems, signs of infections, or HIV antibodies.
If you have too many red blood cells ( polycythemia), your body
may be trying to compensate for getting too little oxygen. If
a lot of carbon dioxide (CO2) is found, a reduced rate and depth
of breathing ( hypoventilation) may be the cause. (Hypoventilation
can cause a decreased concentration of oxygen in the blood that
can, in turn, cause PH or make it worse.) If your blood doesn’t
coagulate normally (if it’s too “thin,” and you
bleed too much) and you are not taking a blood thinner, this may
suggest liver disease, as does a low albumin level.
Low oxygen saturations may or may not be found in PH patients;
they are more commonly found in the sickest patients. Low oxygen
saturation in a PH patient may mean the patient’s heart is
shunting blood from the right side back to the left side, or bypassing
the air sacs of the lungs. It is possible, however, for someone
with severe PH to have normal oxygen saturation. If low saturation
is found, it can be caused by several things, including the presence
of interstitial lung disease (chronic inflammation and disruption
of the walls of the air sacs), and holes in the heart, which may
lower the oxygen saturation even if the patient has only mild
PH.
The oxygen saturation of your blood can also be measured by putting
a clothespin-like clip (a pulse oximeter) over your fingertip.
It sends a light through your skin that lets a gizmo determine
how red your blood is. More red means more oxygen in the red blood
cells, the Certsshaped blood cells that haul around the oxygen.
Sometimes an overnight sleep study with a pulse oximeter will
be done. Kids having such a test may say they have “an E.T.
finger.”
Even if the blood gas or oximeter test shows normal oxygen levels,
your doctor may want to take a closer look and see how your oxygen
saturation is while you are exercising or sleeping. Many PH patients
who have normal oxygen saturations at rest will require supplemental
oxygen when up and about, when doing more strenuous activities,
or while sleeping.
At the PHA conference in 2002, a patient asked a panel of doctors
why, when she was well saturated with oxygen, she was still short
of breath. The doctors said that although a lack of oxygen can
make you short of breath, shortness of breath is usually related
more to right-heart failure and cardiac output than to how much
oxygen is bound to the red blood cells. For example, when you
start climbing a flight of stairs, even if your blood is “fully
loaded” with all the oxygen it needs, the blood stream doesn’t
deliver the oxygen to where it is needed in time to prevent breathlessness.
Chest x-rays can reveal an enlarged right ventricle and
enlarged pulmonary arteries (the main pulmonary artery leading
from the right ventricle of the heart to the lungs, and the first
left and right branches of that artery). If the smaller, peripheral
blood vessels are not visible in the lungs in an x-ray (or angiogram),
“pruning” of the vasculature tree might have occurred,
which is a sign of PH. This means that as the vessels go further
out from the right heart towards the lungs, they quickly taper
(narrow down).
Your doctor can also look at the x-ray for clues that suggest
emphysema or interstitial fibrous disease of the lungs. PH caused
by chronic blood clots can be suggested by triangular or wedgeshaped
patches of scar tissue in the lungs
downstream from suspected clots where almost no blood vessels
are seen on the x-ray.
Doppler Echocardiogram. This procedure is painless and
is often used both to make a preliminary diagnosis and to later
monitor a patient’s condition. In their February 2002 Journal
of Respiratory Diseases article, “A Systematic Approach
to Pulmonary Hypertension,” Gordon Yung and Lewis Rubin (both
at UC San Diego) emphasize that a chest x-ray and echocardiography
should be done “whenever this [PH] diagnosis is suspected.”
Doppler-echocardiography can also show that a patient has congenital
heart disease, which may have caused the patient’s PH. Here’s
what to expect: a technician will put some sticky-backed electrodes
(patches) on your skin. You lie on your side in a darkened room
while the technician uses bouncing sound waves (sonar, or ultrasound)
to make a moving image of your heart (the machine works a lot
like a fisherman’s depth and fish finder, and is the same
machine that obstetricians use to take pictures of a fetus developing
in a mother’s uterus). A chilly “transducer” (it
looks like a microphone attached to a cable) is pressed against
your chest, along with some clear jelly to enhance the transducer’s
ability to pick up sound waves. The microphone first sends the
sound waves into your body and then picks up their echoes when
they hit internal surfaces like a heart
valve.
Because some PH patients may have an elevated PAP only while
exercising, many experts do exercise echoes while their patient
is exercising, usually on a semi-erect or supine bicycle. When
an exercise echo is done immediately after the patient stops exercising,
the results are less accurate.
As far as is known, it does not harm the body to have these high-frequency
sound waves pass through it. No x-rays or needles are involved
in this procedure. This is why the procedure is called “noninvasive.”
During the echo, a record is made of things like whether the right
chambers of the heart are enlarged, the thickness of the wall
of the right ventricle, any structural heart abnormalities (such
as narrowed heart valves or congenital heart disease), or any
abnormal amounts of fluid around the heart.
As mentioned, in PH patients, the right chambers of the heart
are often enlarged and weakened. The muscular walls of the right
ventricle are thicker than normal because it is working too hard.
If the dividing wall between the two ventricles bows into the
space of the left ventricle, this is another indication that the
PH is severe (see the MRI scan illustration on p. 6). A smaller-than-normal
leftventricle is also a sign of severe PH.
An echo can reveal whether the right ventricle is contracting
well or poorly. Cardiac output can be estimated from an echo,
although the measurement is not always accurate.
The echo also measures the amount of blood flowing through the
heart valves. For example, when the right ventricle of a person
with PH contracts, some blood does not go into the pulmonary artery,
as it should, but leaks (jets) backwards through the tricuspid
valve, into the right atrium (tricuspid regurgitation). The Doppler
principle (the same principle that explains why the sound from
a train’s horn coming toward you is different from the sound
when it is going away from you) allows an estimation to be made
of the severity of the PH. The speed with which blood cells jet
backwards through the tricuspid valve depends on the pressure
difference between the ventricle and atrium. This pressure difference
is a reflection of the pressure in the pulmonary artery.
After the test, mathematical calculations usually allow an expert
to estimate your
systolic pulmonary artery pressure (PAP). It cannot be measured
on everyone. Note that echocardiograms give an estimate of systolic
PAP, which is often 30 to 50 percent higher than your mean PAP.
To calculate your mean PAP you need to know your diastolic PAP
as well, which is only obtainable from an echo if there is leakage
in the pulmonary valve (much less common than tricuspid regurgitation).
Even then, it is not always reliable. The only way to get exact
measurements is with a cardiac catheterization (see below).
How does your echo compare to those of other PH patients?
A study at the University of Michigan of 51 PPH patients who had
echoes found that, at the time of their diagnosis, 96 percent
already had a systolic PAP of over 60 mg Hg, 92 percent had an
enlarged right atrium, 98 percent an enlarged right ventricle,
and 76 percent had reduced right ventricle systolic function (a
weakened right heart).
Echocardiograms are pretty accurate for most patients, but not
as precise as cardiac catheterizations. The echo numbers may be
off slightly or by a great degree. When pressures are really high
(above 100 mmHg) they may be more likely to deviate. Because echoes
are less risky—and more pleasant for the patient than catheterizations—some
doctors may use them to monitor a PH patient. There are situations,
however, where repeated catheterizations are essential.
If an echocardiogram is done by a technician without special
training and/or
experience with PH patients, the results can be way off. Anecdotes
abound of patients who were falsely told they did or did not have
PH on the basis of poorly done echoes. This means you need to
ask about the technician’s training and experience (and also
that of the doctor who will be interpreting the tests). An echo
cannot be properly interpreted without clinical information from
your specialist. Experts can also use these echoes to look for
heart disease that may have contributed to your PH. For instance,
if your left atrium is too big, it may be that you have high pulmonary
venous pressures. You might have heart valve problems, or congenital
heart disease. To look for the latter, you’ll probably have
a “bubble” study done during your echo, which uses agitated
salt water, pushed into your veins via an IV, to look for blood
flowing through places that it shouldn’t (such as holes in
the heart). This is called shunting.
If shunting looks likely, your doctor may order transesophageal
echocardiography to get better pictures of what is going on, because
the esophagus (the tube from your throat to your stomach) is close
to your heart. This isn’t a whole lot of fun, because you
have to swallow a probe, a long narrow tube with a small echo
microphone on the end. It’s very low risk, however, and the
use of sedation and local anesthesia can make you comfortable
during the procedure. If it’s your child undergoing this,
plan a treat like ice cream afterwards—after the throat-numbing
medicine wears off!
Computed tomography (CT or CAT scans) uses a computer
hooked up to an x-ray machine that rapidly rotates around you
taking pictures from many angles. The computer translates these
images into detailed, 3-D “slices” of your body, revealing
much that can’t be seen by an ordinary x-ray. CT scans are
getting better and better as a diagnostic tool, and can detect
blood clots in the large arteries of your lungs, yield information
about your heart, and diagnose lung disease. CT scans can sometimes
find other causes for your symptoms, such as pulmonary fibrosis
or emphysema (these diseases can lead to PH). A CT scan may reveal
blood clot (chronic thromboembolic) problems (although a negative
scan doesn’t completely rule out such clots), blocked pulmonary
veins (venoocclusive
disease), tumors, inflamed vessels, or mediastinal fibrosis (there’s
more on these
causes of PH in Chapter 3). Some PH specialists are now using
ultrafast CT scans (called electron-beam tomography or EBT) in
addition to echocardiograms, to monitor changes in the size of
a patient’s right atrium and right ventricle. These scanners
take their pictures faster than conventional CT scanners and thus
can better “freeze” the heart in motion.
Magnetic resonance imaging (MRI) scans for PH have also
improved. Like CT scans, they are noninvasive (nothing goes inside
your body). Magnetic fields and radio waves produce pictures of
your heart and arteries; no radiation is involved and the procedure
is not thought to involve any risk. It’s painless, but expensive.
The pictures look sort of like xrays, but can often show some
tissues x-rays miss.
An MRI might be ordered to look for large blood clots (although
it can’t totally rule
them out), problems with the structure of pulmonary arteries,
the size and shape of the right ventricle, the thickness of the
wall of the right ventricle (which correlates, in an MRI, with
mean PAP) and other relevant things. Your mean PAP can be estimated
from information obtained with an MRI.
Here’s what happens: you lie inside a big white tube to
have the test, and listen to queer noises, some of which sound
like tennis shoes tumbling in a dryer. Some machines’ walls
are open on the side, and some are closed. If your facility has
one of the latter and you get claustrophobic, it helps to put
on a sleep mask or drape a folded towel across your eyes. Remove
all metal objects before the test; the magnets used are powerful.
They will rip earrings from your ears and you will not be able
to pull them off the magnet. Also, don’t get within 50 feet
of the magnet with your credit cards—they will be instantly
demagnetized. If you have a pacemaker or war shrapnel buried inside
you, you can’t have this test. By accompanying her daughter
to such a scan, one mom learned for the first time about her daughter’s
body piercings.
Nuclear scan (a.k.a. ventilation / perfusion scan or V/Q scan).
This is done to take a look at the plumbing in your lungs and
see if the trouble could lie in the large or the small vessels.
The Q of V/Q: a radioactive isotope is injected into a
peripheral vein, and your chest is then scanned for radioactivity.
It is usually done on an outpatient basis. The isotope’s
movement in the pulmonary arteries is tracked from outside your
body by special cameras (sort of like Geiger counters). Your doctor
looks for areas where blood flow is blocked or reduced by clots.
If none are found, it means the problem is probably in the small
vessels. If significant blockages (clots) are found in the larger
arteries, this can be good news, because chronic thromboembolic
disease can often be cured by surgery. Therefore, these clots
should be looked for in all PH patients. If your V/Q scan is normal,
you can usually (not always) rule out chronic thromboembolic disease.
The V of V/Q: in this procedure you breathe in a little
radioactive gas and let it fill the airways of your lungs. Doctors
can then compare the blood flow in your lungs’ arteries with
the airflow through adjacent airways. If it’s PH that’s
causing your problems, the airflow will probably be fairly normal
in areas where blood flow is low due to occluded arteries. Occasionally,
what looks like thromboembolic disease on a V/Q scan may turn
out to be a tumor or inflammation in a pulmonary artery, something
pressing on an artery, or pulmonary veno-occlusive disease (a
rare disease where fibers gunk up small pulmonary veins).
Pulmonary function tests. These tests measure how much
air your lungs can hold, how much air moves in and out of them,
and their ability to exchange oxygen and carbon dioxide. They
may be done to assess the severity of your PH and glean clues
as to its cause.
In one test, you breathe in until it hurts, then expel that breath
as fast and thoroughly as you can. This reveals your lung volume.
The lungs of many persons with PH process a slightly smaller volume
of air, probably because the PH makes them stiffer. (If the volume
found is less than 70 percent of normal, something other than
PH may be causing the reduction in volume.)
In another test, you breathe in and out as deep and fast as you
can. It can be quite stressful, especially when the technician
is yelling at you to try harder.
Pulmonary function tests can also tell if there is a blockage
in the trachea, a nerve problem, or a muscular weakness that contributes
to breathing difficulties, and whether you hyperventilate (blow
off too much carbon dioxide, making you lightheaded).
Carbon monoxide diffusing capacity test (DLCO). A DLCO
estimates how well oxygen is transferred from your lungs’
air sacs into your blood. Because it’s hard to measure this
movement using oxygen itself, carbon monoxide (CO) is substituted.
You breathe in a little CO, hold your breath for 10 seconds, and
then exhale into a CO detector. If no CO is detected, it means
it was well absorbed by your lungs (and that oxygen would be well
absorbed, too). If CO is still found in the air you breathe out,
then it wasn’t transferred well from the lungs’ air
sacs into the blood vessels surrounding them. Patients with IPAH,
familial PH, or PH due to chronic thromboembolism often do not
exchange quite as much oxygen as they should. However, many lung
diseases other than PH can also cause a poor diffusing capacity.
A normal test strongly suggests that a patient’s PH is not
caused by pulmonary fibrosis, emphysema, etc. Your ability to
exchange oxygen usually correlates with your pulmonary vascular
resistance, NYHA or WHO class, and your ability to do physical
work, but not necessarily with the severity of your pulmonary
artery pressures. Researchers at Harbor-UCLA Medical Center say
that measuring DLCO (and, to a lesser extent, lung volume) can
help specialists evaluate patients who complain of breathlessness
and fatigue. If a patient is not exchanging oxygen well, it can
make a doctor think more seriously about PH,
so that PH may be discovered several years earlier than it might
otherwise be.
If you have limited systemic sclerosis or scleroderma (see Chapter
3), the higher your PAP, the lower you can expect your DLCO to
be. Your doctor will probably want to repeat a DLCO test once
or twice a year to see if your pulmonary vessels are becoming
more damaged.
Exercise tolerance tests. Your doctor might ask you to walk on
a treadmill or give you a 6-minute walk test to find your exercise
tolerance level. A healthy person should be able to walk at least
500 meters in 6 minutes; someone with moderate PH might manage
only 300-400 meters. Children might be asked to ride a stationary
bicycle.
Because our symptoms vary from day-to-day, are these tests accurate?
Doctors say that if you haven’t just gotten off an airplane
from a flight to Australia, or stood in line for hours the day
before, the test results are reproducible to within about a 15
percent variation. If you are being tested as a participant in
a drug trial, you will be given a series of exercise tolerance
tests to get an accurate baseline. Your weight, physical conditioning
(or lack thereof), lack of effort, and PH may all affect how well
you do on the tests.
Cardiopulmonary exercise testing (CPET). CPET is used
to tell your specialist how sick you are, and also to see what
effects treatments have had upon your condition. In a CPET, you
breathe into a mouthpiece (maybe while riding a stationary bicycle
or walking on a treadmill) while an ECG is being done. Although
not painful, it’s not a glamorous procedure. Wear exercise
clothes and sneakers. Because your nose is pinched shut and your
mouth is clenched around a tube, you may drool a lot. The bicycle
seat can be politely described as uncomfortable in spots. Ask
for a gel pad if the seat is too hard. If you feel panicky about
having to breathe through a mouth tube, try pretending you are
snorkeling. If you are feeling tired the day you take exercise
tests, you may find them exhausting in more than one sense, and
may want to arrange for somebody to drive you home afterwards.
Polysomnogram. This is a combination of tests done if
sleep apnea is suspected. (Sleep apnea is when you episodically
stop breathing at night.) The tests monitor brain wave activity
(with an electroencephalogram or EEG), the
amount of oxygen in your blood (with a pulse oximeter), the movement
of air in and out a nostril as you breathe, and the up and down
movement of your chest wall.
Right-heart catheterization. This is still one of the
most accurate and useful tests for PH, and the only test that
directly measures the pressure inside the pulmonary arteries.
It should be done in all patients at least once, to get a definitive
diagnosis (unless there is some special safety reason for not
doing so). If your doctor has good reason to suspect PH, but PH
didn’t show up on a resting or exercise echo, then a right-heart
catheterization might be called for. Because of the accuracy of
this test, some doctors use it not only to diagnose, but also
to monitor their PH patients. When combined with the injection
of contrast dye (pulmonary angiography) it can tell whether chronic
thromboembolic disease is causing your PH.
A right-heart catheterization, vasodilator study, and maybe an
angiogram are usually done while you are awake, because the docs
need your cooperation in taking deep breaths and such. Children
and some adults might be sedated to make them less anxious. You
have to spend a long time lying on a hard table (thus earning
the appellation “patient”) but most find the procedures
more uncomfortable than painful.
I was allowed to watch from behind a clear plastic “lead”
screen, to protect from x-rays, while Lisa had her catheter put
in. She was covered from head to toe with sterile paper and cloth
drapes; only her pink face was visible. Even the machines close
to her were covered with sterile plastic. The doctor at the University
of Washington worked fast and confidently. He used a small portable
x-ray machine called a fluoroscope that let him see exactly where
the catheter was going. The catheter, a thin, flexible tube with
a small inflatable balloon on the tip (a Swan-Ganz catheter) was
inserted into Lisa through a vein in her neck (often a groin vein
is used) and threaded all the way through the right side of her
heart and into her pulmonary artery, where it immediately started
measuring her pressures ( hemodynamics). Lisa said the experience
felt more like tugging and pressure than pain.
A cardiac cath gives your doctor your systolic, diastolic, and
mean PAP, right atrial pressure, cardiac output, and pulmonary
capillary wedge pressure. (The narrowing of the small arteries
may make wedge pressures inaccurate, however.) Pulmonary vascular
resistance(PVR) is then calculated from the other numbers and
is an index of how much resistance to blood flow through pulmonary
blood vessels is present.
Cardiac caths are also a way of finding congenital defects in
the heart, such as a hole between heart chambers or the large
arteries that isn’t supposed to be there. (Unfortunately,
a cardiac cath does not detect every type of congenital heart
disease.)
For a pulmonary angiogram, sometimes done at the same
time as the cardiac cath, x-ray dye is injected through the catheter
and then an x-ray is taken of the pulmonary arteries to see whether
the vascular tree has been “pruned” or blocked by blood
clots. This is the very best way to define the anatomy of such
clots. (If a lung scan or CT scan has excluded clots in the lungs
as a cause, an angiogram is often not necessary.)
Left-heart catheterization. Similar to a right-heart cath,
but with the catheter inserted via an artery rather than a vein,
this test allows measurements of pressures on the left side of
the heart, and is also done to take pictures of the heart and
the coronary arteries (a coronary antiogram). In PH patients it
is usually done to exclude the possibility that abnormal pressures
in the left heart are causing, or contributing to, the elevation
of a patient’s PAP.
Heart catheterizations are usually safe if done by a physician
with experience working on PH patients. But there are risks involved.
Although most complications are minor, and most hospitals are
well equipped to deal with them, there is still a tiny risk of
infection (less than one in a thousand), and of various uncommon
problems (including heart attack, stroke, bleeding, or even death).
The 1993 and 2000 editions of the Mayo Clinic Heart Bookdiscuss
cardiac caths in general as well as the somewhat greater risks
associated with catheterizing arteries (where the blood pressure
is higher than in veins), which include bleeding, bruising, clotting,
and the risk of a hole being accidentally poked through the artery
or the heart.
Talk over the risks and the benefits with your doctor. Ask how
many PH patients he or she has catheterized. If a doctor has little
experience doing right-heart caths, the risk of complications
may be higher than with a more experienced doc.
Vasodilator study (a.k.a. acute vasodilator challenge).
If you have PH, you’d much rather take a pill (such as a
calcium channel blocker, or CCB) than undergo more complicated
therapy. Therefore, while the catheter is still in place, doctors
can evaluate your response to drugs that relax your pulmonary
arteries. Sometimes, some doctors will skip this step on certain
types of patients who are unlikely to respond well and/or are
unlikely to tolerate CCBs: those who have connective tissue disease,
advanced Class IV symptoms, significant right ventricular failure,
or who are rapidly deteriorating.
There is a lot of heated discussion over which drug is best to
use for the vasodilator test. Epoprostenol, iloprost, nitric oxide,
adenosine (a potent vasodilator with biochemical features virtually
identical to epoprostenol), sildenafil, and CCBs have all been
used. Nitric oxide, iloprost, and even epoprostenol can easily
be administered through a facemask or nasal cannula. Because inhaled
gases affect only your pulmonary system and quickly leave your
body, they are increasingly being used (although inhaled epoprostenol
is an “off-label” use). The other PH drugs enter your
body through an IV, although CCBs may also be given as pills.
CCBs are seldom used any more in this test because they hang
around in the system too long and are more likely to cause shock
or prolonged hypotension in those who don’t respond well.
Although most patients who respond well to one vasodilator will
also respond well to the others, there are exceptions. Some patients
who do not respond to nitric oxide may respond to prostacyclin.
Some who do not respond to CCBs may respond to prostacyclin, adenosine,
or nitric oxide. If you do respond well to prostacyclin, adenosine,
or nitric oxide, you are more likely to respond well to CCB pills.
The test drug is tried in higher and higher doses, pausing at
each dose to see how you are reacting. When a significant response
occurs, or the side effects get bad, the test is considered complete.
By noting changes in lung pressures and cardiac output in response
to a vasodilator, your doctor can determine the best drug for
you and the best starting dose. Even if you do not respond well
to these
drugs during the short test, over a longer period you might benefit
from epoprostenol or bosentan just as much as someone who does
respond.
Doctors can’t agree on what constitutes “vasoreactivity”
or a good (“acute”) response. In the past, it has been
somewhere in the neighborhood of a 15-30 percent decline in PVR.
But recently, Dr. Olivier Sitbon in (Université Paris-Sud,
Clamart, France) showed that for a patient to have a really good
response, their mean PAP should fall to 40 mm Hg or even lower
while being given the vasodilator.
If you are being tested at a facility that is not a PH center
(PHA doesn’t recommend this), make sure your doctors know
that a decrease in your PVR might not be accompanied by a decrease
in your PAP if your cardiac output goes up. Maybe 10 to 15 percent
of IPAH patients have a good response to a vasodilator. Even fewer
patients with secondary PH have a good response. But among children,
30 to 35 percent are vasoreactive.
Not surprisingly, the lucky few are called “responders.”
Why do they respond? It is thought that in the early stages of
PH, the structural changes to pulmonary arteries are likely to
be less, and you are more likely to respond well. If you have
really severe PH, the damage to your small pulmonary arteries
probably goes well beyond the muscle layer of the vessels, which
relaxes in response to vasodilators. The vessel wall becomes stiff
and less able to relax.
Responders are usually sent home with CCB pills. The Mayo Clinic
sends home 10 to 15 percent of the PH patients they test with
such pills. (Sometimes, before they go home and while the cath
is still in place, their dose is adjusted.) But responders with
right-heart failure and high right-atrial pressures (equal to
or greater than 20 mm Hg) are often started on epoprostenol or
bosentan in spite of their good hemodynamic response. After being
sent home, responders are carefully monitored. Over time (weeks,
months) the dose is usually gradually increased if the patient
can tolerate it.
Lung biopsies are only done now in
special circumstances, because they yield too
little information for the risk involved.
New tests for PH in the future? If you’ve read this
far, you’re probably thinking that better ways are needed
to diagnose PH and determine the disease’s likely course
in different patients. You are right. We need a test that is easy,
that can be done in a standard way at any treatment center with
reproducible results, that correlates well with survival, that
doesn’t hurt much, and that doesn’t cost a lot. That’s
wishing for a lot, and is probably more than any one test could
ever do given all the types of PH. But improvements over the present
diagnostic system are both needed and possible.
