Patients with
coronary artery blockages may have minimal symptoms
and an unremarkable or unchanged EKG while at rest.
Alternatively, patients with no heart disease may
have fairly convincing symptoms and a suspicious EKG.
Both groups may benefit from a cardiac stress test
during which exercise or a chemical substance is used
to stress the heart and expose hidden heart disease
or to help rule it out. .
The heart may be stressed by having
a patient exercise on a treadmill or a stationary
bicycle. If the patient is unable to exercise secondary
to physical limitations such as severe arthritis,
artificial limbs, generalized weakness, paralysis,
unsteady gait, etc., the physician may choose a pharmacological
or chemical form of test. In the latter case, a medication
is given intravenously to perform a nearly comparable
degree of cardiac stress. If possible, some form of
pharmacological stress testing may be combined with
a brief period of treadmill exercise.
Stress testing, particularly those employing exercise,
help reveal the following:
- The length of exercise demonstrates physical tolerance
and conditioning.
- Extreme and inappropriate shortness of breath,
chest discomfort, dizziness and unexpected weakness
may suggest underlying heart disease.
- The blood pressure is recorded at intervals during
stress (in the beginning and usually at three minute
intervals, if stable). It may be checked more frequently
if the patient's blood pressure response to exercise
is abnormal.
- High blood pressure during exercise may provide
an early clue or indication about this problem.
Normally, the systolic (upper reading) blood pressure
may rise up to 200 during extreme or peak exercise,
while the diastolic (lower reading) remains below
90. Patients with inadequately controlled high blood
pressure usually display high diastolic readings
during exercise.
- A drop in blood pressure during exercise may indicate
heart disease.
- Exercise may provoke arrhythmias (pronounced a-rhyth-me-yaz)
or irregular heart rhythm which may not be seen
at rest and may or may not point to heart disease.
- The EKG is constantly monitored during exercise
and recorded on paper at intervals (usually every
minute) and compared to the EKG obtained at rest.
Changes in the ST segment and T waves may indicate
heart disease.
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The equipment in a
typical cardiac stress test lab is demonstrated above
(left). The picture shows a treadmill. However, some
labs may be equipped with a stationary bicycle. The
EKG monitor and paper recorder plus the blood pressure
cuff is also shown. The RISK of cardiac stress testing
is very small. However, since it is carried out in
patients with known or suspected heart disease, almost
every lab is also equipped with emergency cardiac
drugs and resuscitative equipment. It is emphasized
that these are precautionary measures that are rarely
needed.
PREPARATION: Do not eat three hours
before the test. However, it is acceptable to use
small amounts of liquid, particularly if it is needed
with medications. A heavy meal prior to stress testing
may cause nausea, and is discouraged. Depending upon
the time of the day that the stress test is conducted,
diabetics will need special instructions about the
use and dose of insulin. Also check with your doctor's
office about taking your usual medications before
the test. Specific medications may be held for 24
hours prior to the test to achieve more accurate results.
Wear comfortable clothes and walking shoes or sneakers
that would be suitable for exercise.
A trained technician or nurse will
place small sticky patches on your chest. These are
known as electrodes and are attached to wires that
transmit the electrical activity of your heart to
the EKG monitor and recorder. A wrap may be placed
around your waist to hold the cables in place.
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An EKG is then recorded
on paper. This is known as the RESTING EKG and serves
as a baseline. Additional recordings will be made
during and following exercise. The physician will
pay particular attention to changes in the pattern
of the EKG (ST segments and T waves, heart rate, and
the presence of an abnormal heart rhythm).
During stress
testing, the heart rhythm is constantly displayed
on a heart monitor. This allows the physician to keep
an eye on the patient's heart rate, and to watch out
for telltale EKG changes and irregular heart rhythm.
When a treadmill or stationary
bicycle stress testing is conducted, it is continued
until the patient achieves a target heart rate (based
upon age). However, it may be stopped early if the
patient develops significant symptoms (chest pain,
extreme shortness of breath, weakness, leg fatigue,
dizziness, etc.), serious irregular heart rhythm or
marked elevation of blood pressure. It is emphasized
the majority of patient's do not develop these problems.
Fatigue, as would be expected after a good workout,
is the only residual complaint.
