How does a Regular
Stress Test work?
When is a Regular Stress Test ordered?
How is a Treadmill Stress Test
Preparing for the test?
How safe is it?
What is the reliability of the test?
How quickly will I get the results?
How does a Regular Stress
Test Work? Patients with coronary artery
blockages may have minimal symptoms and an unremarkable
or unchanged EKG while at rest. However, symptoms
and signs of heart disease may become unmasked by
exposing the heart to the stress of exercise. During
exercise, healthy coronary arteries dilate (develop
a more open channel) than an artery that has a blockage.
This unequal dilation causes more blood to be delivered
to heart muscle supplied by the normal artery. In
contrast, narrowed arteries end up supplying reduced
flow to it's area of distribution. This reduced flow
causes the involved muscle to "starve" during
exercise. The "starvation" may produce symptoms
(like chest discomfort or inappropriate shortness
of breath), and the EKG may produce characteristic
abnormalities. Most commonly, a motorized treadmill
is used for exercise, while a stationary bicycle is
used in some exercise laboratories.
When is a Regular Stress Test ordered?
A regular stress test is considered in the following
- Patients with symptoms or signs that are suggestive
of coronary artery diseases (CAD).
- Patients with significant risk factors for CAD.
- To evaluate exercise tolerance when patients have
unexplained fatigue and shortness of breath.
- To evaluate blood pressure response to exercise
in patients with borderline hypertension.
- To look for exercise-induced serious irregular
that the regular stress test is heavily dependent
upon interpretation of EKG changes produced by exercise.
Therefore, the reliability drops drastically if there
are significant EKG changes at rest (for example in
patients with long standing high blood pressure, an
artificial cardiac pacemaker, use of medications like
digitalis, or presence of a bundle branch block pattern,
etc.). In all such cases, the physician will usually
order an Echo Stress Test or a Nuclear Stress Test,
particularly if he or she is suspecting coronary artery
disease. However, a regular stress may be sufficient
in stable patients or those with a low suspicion of
coronary artery disease who are being assessed for
exercise tolerance (for example, prior to undergoing
a structured exercise or rehab program).
How is a Regular Treadmill
Stress Test Performed? The patient is brought
to the exercise laboratory where the heart rate and
blood pressure are recorded at rest. Sticky electrodes
are attached to the chest, shoulders and hips and
connected to the EKG portion of the Stress test machine.
A 12-lead EKG is recorded on paper. Each lead of the
EKG represents a different portion of the heart, with
adjacent leads representing a single wall. For example:
- Leads 2, 3, and aVF = bottom or inferior portion
of the heart.
- Leads V1 and V2 = septum or partition of the heart.
- Leads V3, V4, V5 and V6 = anterior or front portion
of the heart.
- Leads 1 and aVL = superior or top and outer left
portion of the heart.
- Lead aVR looks at the cavity of the heart and
has almost no clinical value in identifying coronary
Three of the EKG leads are
also constantly displayed on the treadmill monitor.
Each lead representing a different wall. The physician
has the option of selecting different combinations
The treadmill is then started at a relatively slow
"warm-up" speed. The treadmill speed and
it's slope or inclination are increased every three
minutes according to a preprogrammed protocol (Bruce
is the commonest protocol in the USA, but several
other protocols are perfectly acceptable). The protocol
dictates the precise speed and slope. Each three minute
interval is known as a Stage (Stage 1, Stage 2, Stage
3, etc. Thus a patient completing Stage 3 has exercised
for 3 x 3 = 9 minutes). The patient's blood pressure
is usually recorded during the second minute of each
Stage. However, it may be recorded more frequently
if the readings are too high or too low.
As noted earlier, the EKG
is constantly displayed on the monitor. It is also
recorded on paper at one minute intervals. The physician
pays particular attention to the heart rate, blood
pressure, changes in the EKG pattern, irregular heart
rhythm, and the patient's appearance and symptoms.
The treadmill is stopped when the patient achieves
a target heart rate (this is 85% of the maximal heart
rate predicted for the patient's age). However, if
the patient is doing extremely well at peak exercise,
the treadmill test may be continued further. The test
may be stopped prior to achievement of the target
heart rate if the patient develops significant chest
discomfort, shortness of breath, dizziness, unsteady
gait, etc., or if the EKG shows alarming changes or
serious irregular heart beats. It may also be stopped
if the blood pressure (BP) rises or falls beyond acceptable
limits. Please note that the systolic BP (upper number)
may normally rise to 200 at peak exercise. At the
same time, the diastolic BP (lower number) remains
unchanged or falls to a slight degree. In contrast,
the BP of patients with hypertension or high BP will
show a rise of both systolic and diastolic readings.
The latter may rise above 90 - 100.
Preparing for the
Regular Stress Test:
The following recommendations are "generic"
for all types of cardiac stress tests:
- Do not eat or drink for three hours prior to the
procedure. This reduces the likelihood of nausea
that may accompany strenuous exercise after a heavy
meal. Diabetics, particularly those who use insulin,
will need special instructions from the physician's
- Specific heart medicines may need to be stopped
one or two days prior to the test. Such instructions
are generally provided when the test is scheduled.
- Wear comfortable clothing and shoes that are suitable
- An explanation of the test is provided and the
patient is asked to sign a consent form.
- How long does the entire test take? A patient
should allow approximately one hour for the entire
test, including the preparation.
How safe is a Regular
Treadmill Stress Test? The risk of the stress
portion of the test is very small and similar to what
you would expect from any strenuous form of exercise
(jogging in your neighborhood, running up a flight
of stairs, etc.). As noted earlier, experienced medical
staff is in attendance to manage the rare complications
like sustained irregular heart beats, unrelieved chest
pain or even a heart attack.
What is the reliability
of a Regular Stress Test? If a patient is
able to achieve the target heart rate, a regular treadmill
stress test is capable of diagnosing important disease
in approximately 67% or 2/3 rd of patients with coronary
artery disease. The accuracy is lower (about 50%)
when patients have narrowing in a single coronary
artery or higher (greater than 80%) when all three
major arteries are involved. Approximately 10% of
patients may have a "false-positive" test
(when the result is falsely abnormal in a patient
without coronary artery disease).
How quickly will I
get the results and what will it mean? The
physician conducting the test will be able to give
you the preliminary results before you leave the exercise
laboratory. However, the official result may take
a few days to complete. The results of the test may
help confirm or rule out a diagnosis of heart disease.
In patients with known coronary artery disease (prior
heart attack, known coronary blockages, previous treatment
with angioplasty, stents or bypass surgery, etc.),
the study will help confirm that the patient is in
a stable state, or that a new blockage is developing.
The results may influence your physician's decision
to change your treatment or recommend additional testing
such as cardiac catheterization, Echo Stress test,
or a nuclear stress test.