This chapter describes the special investigations which are commonly
used to help diagnose and evaluate people suspected of having heart disease.
It is divided into two sections.
The first section deals with relatively straightforward tests. Most, or
all, of these can be performed in local district general hospitals. The second
section covers more complex investigations and also a new and important
form of treatment known as coronary angioplasty. These procedures are
undertaken at specialised regional referral hospitals which also have
facilities for cardiac surgery.
An outline is given of what is involved in all these tests and what sort
of information a doctor can derive from them. Patients are often
apprehensive about having some particular investigation. This chapter is
intended to help patients, but it is not a substitute for a frank discussion of
the investigation with the doctor. This particularly applies to those
procedures in Section 2. SECTION 1
This section covers the following investigations:-
1. The electrocardiogram
2. Exercise stress testing
3. 24-hour tape recordings
4. Echocardiography
5. Radionuclide tests 1. The electrocardiogram (ECG)
Most patients attending hospital with symptoms which might come
from the heart have an ECG recorded. Many general practitioners can also
do this. In some circumstances, e.g., before an operation, and ECG may be
done even if there is no suspicion of heart disease. ECG’s are sometimes
recorded as a part of routine health screening, but their value in this context
is rather limited. Four small metal plates called electrodes are strapped or stuck on to
each limb and on to the front of the chest. These are connected to the
recorder which picks up and amplifies the electrical signals produced
written out on paper. The machine only records signals; it does not cause
each heart-beat. A few beats are recorded from each set of electrodes and
electric shocks or in any way affect the heart. The procedure is painless.
and recent heart attacks and give information on whether the heart is
The ECG can pick up abnormalities of heart rhythm. It can detect old
it has some limitations. Sometimes ECG “abnormalities” have an entirely
enlarged or working under strain. The ECG is a simple and valuable test but
heart disease and a normal ECG. Developments have, therefore, been made
trivial and innocent cause. On the other hand, patients can have serious
to improve the value of the resting ECG and two of these are described next.
2. Exercise stress testing
Many patients feel perfectly well when resting, but develop symptoms
on exertion. The purpose of exercise testing, therefore, is to record the ECG
whilst the patients is exercising and hopefully whilst he is having the
symptoms which bother him. The test is particularly valuable in the
assessment of patients with chest pain on exertion.
Before the test, patients on heart drugs are often asked to stop taking
some of them for one or two days. The doctor will discuss this. Light
comfortable clothes and shoes should be worn. Exercise tests are supervised
by a doctor.
Several recording leads are stuck on to the chest and the patient then
exercises on either a treadmill (moving belt) or on a stationary bicycle. The
test starts off very easily and is made progressively harder either by applying
a brake to the bicycle or by increasing the speed and the gradient of the
treadmill. The blood pressure is checked at intervals. The test is stopped
when one of various “end points” is reached. These include excessive
tiredness or shortness of breath, significant changes on the ECG, worsening
chest pain or the patient’s heart rate reaching a set target. Recordings of the
ECG are made during exercise and also after stopping. The exercise is hard
work, but not an ordeal. An average duration is about twelve to fifteen
minutes. Patients are often pleasantly surprised by how much they cam
achieve. Doctors are interested in what the ECG looks like during exercise and
also in the amount of exercise which can be performed. If pain and ECO
changes occur, it may indicate that the pain comes from the heart. If this
happens at a low level of exercise, this is more serious than if it occurs at
Exercise testing can be used after a heart attack to help assess the
situation and aid in rehabilitation. When used in this way the test is less
still not 100% accurate. Rather surprisingly, misleading results are more
common in women than in men.
This technique (sometimes called Holter monitoring) involves
continuously recording the ECG over 24 hours, It is usually done as an
out-patient. It is useful in the diagnosis of symptoms, such as palpitations.
which occur intermittently but never in the doctor’s surgery!: It involves
two visits to the hospital (to have the recorder fitted and to return it).
Recording leads are stuck to the front of the chest. Wires are attached
to these and well taped down. The wires are connected to a small portable
tape recorder which is worn on a belt round the waist. The whole system is
surprisingly comfortable, quiet and unobtrusive and permits all normal daily
activities (except having a bath or shower). Patients are encouraged to
spend a normal day and indulge in any activity which might bring on their
symptoms. They are also given a simple “diary” in which to record the time
of day when any symptoms occur (make sure to state a.m. or p.m.). During
later analysis particular attention will be paid to the tape at these times so
special care in filling in the diary accurately improves the value of the test.
There are a number of variations on this type of test, depending on the
equipment used.
Information derived from ECG’s recorded over many hours is very
valuable and relevant to the patient’s daily life. This technique has shown,
for instance, that many more patients can benefit from heart pace-makers
than was originally thought. 4. Echocardiography
for echoes reflected from surrounding objects. The same principle is used in
Bats can fly in the dark by transmitting pulses of sound and listening
echocardiography. A pulse of high frequency (inaudible) sound is
transmitted through the skin of the chest by placing a probe on the chest
wall. Jelly is used to get a good contact. The probe then picks up the
echoes reflected from various parts of the heart and displays them as a
picture. By moving the probe, different parts of the heart can be seen.
Recording these images is a skilful process and takes time (up to one hour in
some cases). A more recent development of this technique (Doppler
echocardiography) measures the speed of blood flow in different parts of the
heart. The procedure is harmless and does not cause any pain.
Echocardiography has many applications both in clinical medicine and
research. It is routinely used in the assessment of patients with disease of
the heart valves. It is especially valuable in the diagnosis of heart disease in
newborn babies and infants. In these cases this painless test is easy to do,
perhaps with a little sedation, and often saves the child from more complex
and possibly dangerous procedures. Research is progressing in the use of
echocardiography to diagnose heart defects before the child is born. This is
just one example of the technological development in echocardiography
which has made such an impact on cardiology over the last ten years.
5. Radionuclide tests
These tests are more specialised than those mentioned so far. They are
particularly valuable in research but have some clinical applications as well.
A radioactive substance (isotope)is injected into the blood, often while the
patient is exercising on a bicycle or treadmill. A large “camera” is
positioned close to the chest and this picks up the gamma rays emitted by the
isotope. Pictures can be generated either of the cavity of the heart as it
empties and fills or of the blood flow to the muscular walls of the heart,
depending on the isotope used.
The isotopes decay rapidly, so the dose of radioactivity to the patient is
small i.e., comparable to that of a simple chest X-ray. The two commonest
isotopes used are technetium and thallium.