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BILATERAL
LEG EDEMA: A
MARKER FOR SLEEP
APNEA?
CLEVELAND--Should patients who present with bilateral leg edema be screened for underlying obstructive sleep apnea (OSA)? Yes, suggest the authors of a recent study showing that OSA appears to be common in patients with isolated, unexplained pulmonary hypertension who initially present with bilateral leg edema.[1] The finding supports that of an earlier study, which found a link between bilateral leg edema and isolated pulmonary hypertension.[2]
"The
study has important implications for the diagnosis and evaluation
of pulmonary hypertension, as well as for the evaluation
of leg edema," Robert P. Blankfield, MD, told PULMONARY
REVIEWS. "Most cardiologists
and pulmonologists do not consider obstructive sleep apnea
to be a cause of pulmonary hypertension. Consequently, OSA
is usually not considered in the differential diagnosis
of pulmonary hypertension, and sleep studies are typically
not ordered when pulmonary hypertension is identified,"
Dr. Blankfield noted.
"If this study's findings
apply to the general population, then OSA may be the most
common cause of pulmonary hypertension, at least in patients
with leg edema," he said. Furthermore, "failure
to consider OSA as a possible cause of pulmonary hypertension
and failure to order a polysomnogram might lead physicians
to erroneously conclude that a patient's primary diagnosis
is pulmonary hypertension, when, in fact, the correct diagnosis
may be pulmonary hypertension secondary to OSA," Dr.
Blankfield said.
Dr. Blankfield,
principal investigator, and his colleagues studied 15 patients
ages 41 to 81 years, most of whom were obese and had mild
pitting edema. All patients had echocardiographic evidence
of pulmonary hypertension (defined as a pulmonary artery
pressure of greater than 30 mm Hg), but none of the patients
had echocardiographic evidence of left ventricular dysfunction
or any clinically apparent pulmonary disease.
OSA
AND LEG EDEMA
OSA, which
was present in nine of the 15 patients, was the most common
condition associated with bilateral leg edema, followed
by systemic hypertension. All six of the hypertensive patients
also had OSA.
"Although
the majority of studies have found that obstructive sleep
apnea does not correlate well with hypertension, this study
demonstrated a strong relationship between obstructive sleep
apnea and hypertension," said Dr. Blankfield.
ECHOCARDIOGRAPHY
Echocardiography
may have an important role in the evaluation of leg edema,
the authors suggested. "Leg edema in conjunction with
an elevated pulmonary artery pressure (greater than 30 mm
Hg) should raise suspicion of sleep apnea," said Dr.
Blankfield.
"However,
in some patients who have leg edema, echocardiography may
not allow an estimation of the pulmonary artery pressure.
This occurs commonly in obese patients. Consequently, if
the echocardiogram is unable to provide an estimation of
the pulmonary artery pressure, I suggest referring the patient
for a sleep study to check for sleep apnea," he added.
For patients
with bilateral pedal edema who lack symptoms of heart failure
(such as orthopnea, paroxysmal nocturnal dyspnea, and dyspnea
on exertion), the most cost-effective strategy may be to
bypass the echocardiogram and refer the patient to a sleep
laboratory, Dr. Blankfield said.
OSA
LINKED TO PULMONARY HYPERTENSION
Dr. Blankfield
believes that edema associated with obstructive sleep apnea
is extremely common. "In my primary care practice,
I have over two dozen patients who have leg edema who have
OSA," he said. "There is nothing unique about
my practice. Other primary care physicians who care for
adults have similar patients, in similar numbers, most of
whom are incorrectly diagnosed as having another condition,
typically venous insufficiency, as the cause of their edema.
Leg edema associated with OSA is the third most common cardiovascular
condition that I see. It is exceeded in frequency by systemic
hypertension and coronary artery disease but clearly exceeds
strokes and congestive heart failure," said Dr. Blankfield.
"Indeed,
it is my opinion that edema associated with OSA represents
a circumstance akin to the discovery that H pylori
causes peptic ulcer disease. Just as Heliobacter pylori
turned out to be a common infection that went unrecognized
for decades, so will edema associated with OSA eventually
be recognized as a common condition that long went unrecognized,"
predicted Dr. Blankfield.
"Unfortunately,
almost none of the research literature on PPH [primary pulmonary
hypertension] includes sleep studies. As an example, previous
studies which identified a relationship between appetite
suppressants and PPH did not include sleep evaluations as
part of the protocol," he said.
"Obese
patients are at risk for OSA, and these individuals use
weight loss medications. If the results of our study are
generalizable, then the relationship between weight loss
medications and PPH is thrown into question," he continued.
Whether
obstructive sleep apnea causes pulmonary hypertension remains
to be proven. "If one could demonstrate that effectively
treating OSA decreases or normalizes pulmonary artery pressure,
we could prove that obstructive sleep apnea causes pulmonary
hypertension," concluded Dr. Blankfield.
--Deborah
L. O'Connor
References
1. Blankfield RP, Hudgel DW, Tapolyai AA, Zyzanski SJ. Bilateral
leg edema, obesity, pulmonary hypertension, and obstructive
sleep apnea. Arch Intern Med. 2000;160:2357-2362.
2. Blankfield RP, Finkelhor RS, Alexander JJ, et al. Etiology
and diagnosis of bilateral leg edema in primary care. Am
J Med. 1998;105:192-197.
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