Shortly
after moving to the scenic mountain forests of western Arizona, near the border
with New Mexico, a friend of mine, a middle-aged woman in previous good health,
began to experience progressively worsening shortness of breath with exertion. She
had been vigorously active helping her partner tend acreage, and she was unable
to keep up this effort. The
altitude of this land is over 7,000 feet above sea level.
She
was evaluated by her family physician:
a thorough physical exam, a chest x-ray, and ECG and screening
laboratory tests were normal. He
found no cause for her dyspnea.
Her
symptoms worsened, and she was referred for pulmonary function tests that were
interpreted as normal. The
arterial blood gases were normal for the altitude.
She
saw a cardiologist who performed an echocardiogram. The valves were normal; the ejection fraction was greater
than 60%. There was mild pulmonary
hypertension. She was considered
to have become a victim of her own imagination.
I
talked to her partner, and I reviewed her medical records, and I suggested that
she might have high-altitude pulmonary hypertension, and I recommended that
they should try living at a lower altitude. This idea was resisted until winter when they vacationed in
Florida: after a few days at sea
level her dyspnea greatly diminished and then disappeared; it returned when
they returned to the mountains.
Her
pulmonary artery pressures were never measured, but based on her medical
history, I felt, more likely than not, that she had high altitude induced
pulmonary hypertension.
It
turns out that some humans are more susceptible to hypoxic pulmonary
hypertension than is the general population; perhaps
she was one of these individuals.
Susceptibility
to constriction of the pulmonary arteries when exposed to reduced levels of
oxygen is modeled by a dramatically
instructive animal condition known as Brisket Disease of Cattle.
Cattle
ranchers with herds in the Rocky Mountains are well acquainted with Brisket
Disease of Cattle. As their herds are moved from lower winter pastures that are less than five thousand feet to the high altitude
pastures above 7,000 feet in the spring and summer. There, some of the herd, as
many as twenty per-cent, develop high altitude pulmonary hypertension and as a consequence
failure of the right side of the heart.
In
cattle the congested state caused by right heart failure does not cause
swelling of the ankles and legs, known in humans by the archaic term dropsy, instead
the fluid gravitates to their most dependent part, the brisket.
Beefeaters
recognize the brisket as that cut of meet from the chest muscles, the
pectoralis major and minor. The
brisket is the preferred cut for barbecued beef and is used as well for corned-beef
and pastrami.
Above, The Bovine Brisket
Below, a Bovine with Brisket Disease
Colorado
ranchers take brisket disease seriously because of its grave economic
consequences, and in the spring a veterinarian goes up to the high altitude pastures
with the herd. The vet then
does a right heart catheterization on each of the bovines,
and if the pulmonary artery pressure is at all elevated, these animals are returned to lowland pastures and feed.
Well,
my friend never developed overt right heart failure with dropsy, and she was
never interested in getting a right-heart catheterization, but the
ameliorization of her dyspnea when she lived at sea level, convinced her to
avoid the mountains, and they moved to Iowa altitude 1,503 feet above the sea
level.
Recently,
while on vacation from their new home they returned to visit old friends in the
mountains. In a few days her dyspnea
returned, and they promptly returned to Iowa. Her dyspnea again disappeared.
