ABOUT STRESS TESTS
Most cardiologists believe that stress tests can be used to detect the presence
of coronary artery disease in patients believed to be at increased risk whether
or not they have symptoms such as chest pain. The stress part of such tests is
commonly carried out on a treadmill or bicycle ergometer while recording an
electrocardiogram, a nuclear imaging procedure or an echocardiogram. Because
some patients are unable to exercise on a treadmill, a drug is administered
intravenously to these individuals to increase their heart rate. This is
called a pharmacological stress test. Regardless of which stress is used, the
goal of the stress test is to increase the patient's heart rate to a
predetermined rate that is determined by the patient's age. It is believed by
most doctors that if the test is abnormal, then this means the patient has
obstructive coronary artery disease of sufficient degree to interfere with flow
of blood to the heart muscle. When this happens, the heart muscle is said to
Ischemia does not occur at normal heart rates in most patients because at rest,
with a normal heart rate, the heart muscle's need for blood is comparatively
small, and the amount of obstruction of the coronary arteries is not great
enough to reduce the flow of blood to the heart muscle. During stress,
however, when the heart rate speeds up, and the heart has to work harder, the
heart muscle requires a great deal of extra blood to generate the energy needed
to perform the extra work. Now, the obstruction to the coronary arteries may
be great enough, to prevent the blood flow from increasing, and the heart
muscle will become ischemic. Think of a 4 lane freeway with one or two blocked
lanes. When traffic is light there will be no slowing of traffic. During rush
hour, however, marked slowing of traffic will take place.
Ischemia produces distinctive changes in an electrocardiogram, in a nuclear
perfusion study, and in the contraction of the heart muscle that can be seen on
an echocardiogram. When these tests are abnormal, most cardiologists
immediately assume that one or more coronary arteries are severely obstructed,
and that coronary artery bypass surgery or angioplasty will be necessary to
eliminate the blockage.
Little or no consideration is given to the possibility that there may be other
reasons for the test being positive. Nor is there consideration of the fact
that if there is obstructive coronary artery disease, it may have been present
in silent form for years, and that there is another cause for both the
patient's chest pain and for the test becoming abnormal. Indeed, there are
multiple reasons to explain why stress tests become abnormal, and those reasons
have nothing to do with the coronary arteries being obstructed. Failure to
consider these other explanations in patients with coincidental and
asymptomatic coronary artery disease has resulted in hundreds of thousands of
such patients undergoing unnecessary angiograms, angioplasty or coronary artery
bypass surgery every year!
OTHER EXPLANATIONS FOR POSITIVE STRESS TESTS
The most common cause of abnormal stress tests in the absence of obstructive
coronary artery disease is hypertension. Blood pressure invariably rises
during stress tests, particularly so in those patients who have hypertension.
Both the patient and doctor are often unaware of the hypertension because such
patients frequently have relatively normal blood pressures at rest. However,
their blood pressures will rise to very high levels during stress.
The mechanism of how hypertension can cause chest pain and ischemia of the
heart muscle is similar to the changes that occur when a blood pressure cuff is
inflated while taking someone's blood pressure. Air is pumped into the cuff
until the pressure in the cuff exceeds the pressure within the artery. When
that happens the pressure within the cuff is transmitted to the tissues of the
arm to the brachial artery causing it to collapse. In fact, in case of injury
to an extremity from an accident, a blood pressure cuff can be inflated above
the arterial pressure. It will now act like a tourniquet and stop any bleeding
that might be present.
In the case of the heart, the elevated pressure within the circulatory system
during a stress test is transmitted back to the heart's chambers, specifically
the cavity of the left ventricle. If that amount of pressure were transmitted
to the inside of the stomach, it would inflate the stomach like a balloon.
However, the heart muscle is too thick to be distended. In addition, the tough
membrane around the heart known as the pericardium will prevent the heart from
becoming larger. Consequently, the high pressure within the cavity of the left
ventricle is transferred directly to the heart muscle in the same way the
pressure within a blood pressure cuff is transmitted to the arm and brachial
Depending upon the amount of elevation of the blood pressure within the cavity
of the left ventricle, the small blood vessels within the heart muscle will all
be compressed causing a reduction in the amount of blood that can reach the
heart muscle cells. If the reduction in blood flow is great enough, the heart
muscle will become ischemic causing the stress test to become abnormal, and the
patient to experience chest pain. Numerous research studies, particularly in
the European medical journals, have reported patients with high blood pressure,
chest pain, abnormal stress tests, and normal coronary angiograms. In other
words, the abnormal stress test is not due to blockages within the main
A second important reason why stress tests are often artifactually abnormal is
the marked increase in heart rate that takes place, by design, in patients
undergoing such testing. A little bit of background information is necessary
to understand what happens when the heart rate speeds up. In a subject with a
heart rate of 60, each heart beat lasts for one second. Approximately 0.3
second is occupied by the contraction of the heart. The remaining 0.7 second
is for the relaxation of the heart. While all tissues of the body receive
blood continuously throughout both contraction and relaxation of the heart,
this cannot occur within the heart muscle itself while the heart is contracting
for reasons described in the preceding paragraph. In other words, the high
pressure that is generated within the cavity of the left ventricle to provide
the pressure to circulate the blood, prevents any flow of blood within the
heart muscle itself. Thus, blood can only flow within the heart muscle while
the heart is relaxing. The actual amount of time available for the heart
muscle to receive its blood supply is a little less than 0.7 second.
For whatever reason evolution has made the heart the way it is, when the heart
rate speeds up, it does so more at the expense of the time available for
relaxation than for contraction. Accordingly, at a heart rate of 150 per
minute, each heart beat lasts only about 0.4 second. Contraction now takes
about 0.2 second and relaxation also takes only about 0.2 second. That's not a
lot of time---hardly enough time for the heart muscle to receive the amount of
blood it requires to work that hard. What happens? The muscle becomes
ischemic regardless of whether there is any blockage in the subject's coronary
The third reason why heart muscle may become ischemic during a stress test in
the absence of significant obstructive coronary artery disease is similar to
what happens when a telephone switchboard literally becomes overloaded with
incoming calls during a catastrophe. All the calls cannot get through because
of circuit overload. All of us develop coronary artery disease as we get
older---it is an aging phenomena. If there are areas of narrowing, the heart
rapidly adapts and grows new blood vessels around the narrowed artery through a
process called angiogenesis. In a sense the heart puts in its own bypasses.
This is the same process that grows new blood vessels for cancer cells and
tumors within the body, since such growths cannot survive without a blood
supply. Indeed, one of the ways of treating cancer is to destroy its blood
The network of new vessels that grow around narrowed coronary arteries, are
known as collateral vessels, and are too small to be seen on an angiogram.
Nevertheless, such vessels not only allow a normal flow of blood to the heart
muscle, but ensure normal contraction of the heart muscle as well. This
network of collateral vessels that develop around obstructed coronary arteries
keep the heart muscle well oxygenated as long as the heart rate is not too
high. Incidentally, these small vessels cannot be seen on an angiogram, and
this explains why cardiologists often tell patients their arteries are blocked
and they are in danger of a heart attack. Since the angiogram technique does
not allow visualization of either these small vessels nor the heart muscle they
supply, and since there is no blockage of blood flow, such interpretations are
often grossly inaccurate and unwarranted.
Like a telephone switchboard that becomes overloaded, or in the same way that
multiple small roads cannot carry the volume of traffic that a four lane
freeway can, these small vessels are also limited in the amount of blood they
can carry. Accordingly, at very rapid heart rates, when the heart muscle
requires large increases in blood to perform the increased work it must do, the
circulatory system is unable to keep up with the increased load. This causes
the heart muscle to become ischemic, the stress test to become abnormal, and
the victim to have chest pain.
Now combine reasons one, two and three, and it should be obvious that not only
are stress tests unreliable to detect coronary artery disease, they should
never be used! In medical terms, stress tests that are carried out to extremes
of heart rate and blood pressure increases cause physiological ischemia. If I
put my hands around your neck and choke you until you turn blue, and take an
electrocardiogram, and it is abnormal, it does not mean you have heart disease
anymore than if you were to get short of breath after you ran up five flights
of stairs. This, then, is physiological ischemia. Pathological ischemia would
be present if ordinary activities such as walking across a room or getting
dressed produced chest pain or shortness of breath. But one doesn't have of
undergo a stress test to find out that information.
The tragedy of all of this is that the most commonly used noninvasive test for
the detection of coronary artery disease leads to an even more inaccurate
invasive test-the coronary angiogram. Massive amounts of medical studies over
the past 45 years have testified to the inaccuracy of angiograms. Yet they
continue to be used upon an unsuspecting and uninformed public, are proclaimed
to be the "gold standard" and like a black hole that sucks everything in, even
light, stress tests continue to suck patients into undergoing unnecessary
interventions, procedures, and surgery that are not only not effective but kill
more people than they save.
ALTERNATIVE TO STRESS TESTS----MECHANOCARDIOGRAPHY
BACKGROUND: One of the techniques the Noninvasive Heart Center uses to study
the heart is called mechanocardiography, or the science of studying the
mechanical function of the heart. To put things in perspective, the heart may
be likened to an automobile. An automobile has two systems: (1) an electrical
system for the lights, horn, ignition, radio, etc, and a mechanical system for
turning the wheels. Similarly, the heart has two systems: (1) an electrical
system for electrically activating the heart so it can beat once a second, and
(2) a muscle system to contract and pump blood from the heart's chambers,
followed by relaxation so that it can fill with blood for the next heart beat.
One would not check the voltage of a car battery to determine the performance
of a car. Similarly, an electrocardiogram cannot be used to study the function
and performance of the heart. For example, an individual might have a terrible
looking electrocardiogram but be able to play basketball or run a marathon
race. Conversely, a patient might have chest pain with walking less than a
block due to coronary artery disease, but have a completely normal
electrocardiogram. Experience has taught us that survival and prognosis are
not related to the electrical output of the heart (the electrocardiogram) any
more than the voltage of a battery will predict the life of a car.
In the same way that the electrocardiogram cannot provide information about the
heart's function, neither will listening to the heart with a standard
stethoscope provide this kind of information. The diseased heart does develop
abnormal sounds and murmurs. Unfortunately, in all but the most advanced
states of disease, those abnormal sounds and murmurs are of such low or high
frequencies that they cannot be heard by the human ear.
As a result of these limitations, a variety of noninvasive procedures have
evolved over the years. One of these procedures is called mechanocardiography
and enables doctors to obtain mechanical and functional information about how
the heart contracts and relaxes on a moment to moment basis throughout the
cardiac cycle. This is accomplished by the graphic recording of physiological
and pathological events from the heart by external recording instruments that
are placed directly over the heart and blood vessels.
Such instruments record the exact moment the pressure begins to rise within the
left ventricle as the cardiac muscle begins its contraction, the moment the
heart valves (the mitral and tricuspid valves) close, and the force with which
they close, the duration of time in milliseconds it takes for the heart to
generate the required pressure to force the aortic valve (the exit valve) open,
the precise moment the aortic valve opens and allows blood to leave the heart,
the duration of time it takes for blood to be ejected from the heart, the exact
moment the aortic valve closes allowing the heart to relax, the duration, also
in milliseconds, of how long it takes for the heart to relax, the amount of
time required for the initial filling of the heart, the relative pressure
required to do this, and the relative amount of pressure and time required for
contraction of the left atrium.
In addition, the analog readout provides an accurate picture of how well, or
how poorly the ventricle is contracting. At the same time, the instrument
records other physiological or pathological events of the heart's contraction
and relaxation such as any abnormal sounds or heart murmurs, how rapidly blood
is ejected into the circulation, and whether there is any obstruction to blood
flow at the aortic valve. The duration of these various intervals of the
cardiac cycle reflect the performance of the heart in the same way that timing
how long it takes for a car to go from zero to 60 miles an hour is a reflection
of the performance of a car. In a like manner, how long it takes for an engine
to start after turning the key in an ignition, how long it takes to accelerate,
how long it takes to brake or stop each reflect different components of a car's
Similarly, the duration of the various phases of the contraction and relaxation
of the heart reflect the performance or function of a different part of that
heart. For example, a heart that takes 375 milliseconds rather than the normal
300 milliseconds to eject its quota of blood during a single heart beat has an
entirely different problem, and requires a different treatment than a heart
that takes 175 milliseconds to relax instead of the normal 100 milliseconds.
Yet, both abnormalities may cause identical symptoms. Thus, modern technology
can serve as an early warning system to identify component failure and correct
it, rather than to wait for total failure of the whole heart, as is currently
being done. In the former instance, specific drug treatment can be selected.
In contrast, most conventional methods of examination do not become abnormal
until there is total system failure. When drug therapy is recommended with
total system failure, there is little understanding of what specifically is
wrong, and what specific drug should be used to counteract it. Instead, the
doctor guesses, and often, unfortunately, guesses wrong.
Another important group of noninvasive tests that are now incorporated into the
technique of mechanocardiography is echocardiography, including color and
spectral Doppler. The following data is just some of the information that can
be obtained from this cardiac imaging group of tests.
- Localized abnormalities of motion of heart muscle due to obstructive coronary artery disease.
- Flow of blood in heart muscle.
- Thickness of heart's muscular walls.
- Presence of scar formation from prior heart attacks.
- Dimensions of the heart's chambers.
- Blood clots within the heart's chambers.
- Structure and motion of its valves.
- Obstruction or leakage of valves.
- Presence of calcium in heart valves.
- Heart murmurs: their origin, and the volume, velocity and pattern of blood flow through each valve.
- Systolic and diastolic heart function.
- Fraction of blood ejected each beat.
- Presence of tumors and congenital heart defects.
The parameters that are measured are placed in a database for that patient.
The information can be used in a stand alone fashion to evaluate the function
of the patient's heart and to arrive at a predicted prognosis. At future
office visits, repeat recordings are obtained and compared to prior recordings.
The patient's medical program is then adjusted accordingly.
The various parameters that are recorded by this technology allow a doctor
experienced in their interpretation to identify heart disease at a very early
stage long before symptoms or complications appear. He also may determine how
advanced the patient's disease is, track its progression, determine the effect
of drug treatment, modify that treatment to optimize it, and identify
unpredictable changes in cardiac function so that they can be reversed. The
information provided allows almost all patients to avoid future coronary artery
bypass surgery, angioplasty, heart attacks, congestive heart failure, and
unexpected cardiac death.
In summary, most cardiologists depend upon a stress test and only the angiogram
to provide the necessary information on which to make a decision as to how a
patient should best be treated. Both kinds of tests are highly inaccurate, and
lead to unnecessary interventions with angioplasty, stents and bypass surgery
all of which have their own set of complications. Noninvasive tests, in
contrast, are vastly more informative, far less costly, very safe, and can be
repeated as often as necessary to track a patient's disease.