the conditions that cause SADS can be inherited it is important that, if
you are a blood relative in the immediate family of someone who has died
of SADS, you are evaluated for signs of these diseases, particularly the
There may also have been other sudden or suspicious
deaths in your family, including cot deaths, suggesting that there may be
an underlying inheritable condition. Below, we explain what is involved in
the evaluation and describe the tests you may need to have.
is vital that a clear history of the victim and his or her death is
established, using the family’s and friends’ recollections as well as
the reports of the coroner, pathologist, GP and police.
For example, fits brought on by exercise can
be due to an underlying channelopathy such as
Long QT Syndrome (LQTS) or Catecholaminergic polymorphic ventricular
tachycardia (CPVT), or a sudden cardiac death during sleep may have been
caused by sodium channel LQTS or Brugada Syndrome. It is also important to
find out about any medications and any potentially dangerous drugs that
the person may have taken before they died.
doctor may ask you if you have ever had symptoms such as blackouts or
palpitations as these may suggest underlying heart disease.
CRY Patron Lawrence Okoye has an ECG and Echo
medical examination may help to discover if there is an inheritable
structural heart disease in the family. For example, if there is mitral
valve prolapse with leakage from the valve this will cause a ‘murmur’
that a doctor can hear through a stethoscope.
doctor may suggest that you have some of the tests we describe below.
marked with a
non-invasive. ‘Non-invasive’ means that it does not involve
penetrating the skin or body
is the most basic test. It involves taping electrical leads onto your
legs, arms and chest to take readings of the electrical activity of your
These are printed out onto a piece of paper for the doctor to
examine. If the first ECG does not show any sign of a channelopathy, the
test can be repeated later.
leads from the ECG machine are taped to the chest, legs and arms and a
recording is made of the electrical activity of the heart.
averaged ECG *
is an ECG that adds together the electrical readings from at least 250
heartbeats so that any very subtle variations can be seen – for example
if the electrical impulses in the heart are being conducted more slowly.
It is useful for diagnosing Brugada Syndrome, PCCD or ARVC.
called an ‘echo’.
test uses ultrasound waves to look at the structure of the heart. It is
useful for people whose ECG shows changes that could be caused either by a channelopathy or
by uninherited heart disease that has damaged the heart – for example a
previous heart attack that you may not have even been aware of.
echocardiogram can also detect inheritable conditions such as
cardiomyopathy and mitral valve prolapse.
operator puts some clear gel on your chest and then places an ultrasound
probe on it. The probe sends ultrasound beams into your body and their
reflections are detected and used to generate images of the heart.
see different parts of your heart on a screen as the probe is moved around
on your chest.
The test is similar to the ultrasound scan that is used to
examine a pregnant woman’s unborn baby. It is completely painless
called an Exercise ECG.
test is the same as the ECG described on page 00 but is recorded before,
during and after a period of time spent exercising on a treadmill or an
exercise bike. This allows the doctor to examine any changes in the
electrical patterns that occur with exercise, and analyse any
abnormalities. This test is particularly useful in detecting some of the
features that are characteristic LQTS or CPVT.
hospitals may also ask you to do a cardiopulmonary exercise test. This
test analyses the efficiency of the heart muscle by measuring the amounts
of oxygen your body uses during exercise.
leads from the ECG machine are taped to your body and you are monitored
while you exercise either on an exercise bike or treadmill.
you are having a ‘cardiopulmonary exercise test’, your doctor will ask
you to breathe in and out of a special piece of equipment while you are
doing the exercise, in order to monitor how efficiently your body uses
oxygen. If the efficiency of your
heart is low, this may suggest that you have cardiomyopathy (inefficient
pumping action of the heart).
Holter is a recording device that comes in two different forms:
a small portable tape recorder
a small digital device the shape of a pager.
wear the device on a belt round your waist. Four or six ECG leads from the
device are taped to your chest. The device records the electrical activity
of your heart for 24 to 48 hours, or for up to 7 days if a digital one is
used. The doctor can then analyse the electrical activity and rhythm of
your heart to find out if you have any arrhythmias (for example, the
arrhythmias typical of LQTS and CPVT), or some of the other features
characteristic of LQTS.
Holter monitor is attached by 4 or 6 electrical leads to your body. It
monitors your heart’s electrical activity over a period of time.
and event recorder *
are more sophisticated versions of the basic Holter. Whenever you have an
attack of symptoms, you can activate the device to record your heart’s
rhythm. (You can also do this with the digital Holter.) The advantage of
the cardiomemo is that it doesn’t have any leads, so you can just place
it on your chest when you get symptoms, without having to put any leads in
flecainide and adenosine tests)
may be asked to have this test if your doctor suspects Brugada Syndrome.
While you are having an ECG test you will be given an injection of
ajmaline or flecainide (antiarrhythmic drugs). The test may show changes
on the ECG that are typical of one of the channelopathies.
fine plastic tube is inserted into a vein at the front of your elbow. The
drug is injected over a short period of time (5-10 minutes) and you will
be monitored for 20 minutes or a few hours afterwards, depending on the
drug used. There is, however, a risk in 1 in 200 Brugada Syndrome carriers
or their immediate blood relatives of causing a potentially
life-threatening arrhythmia during the injection. The test is therefore
always performed with appropriate facilities to protect patients from this
risk. Ajmaline is preferable as it lasts a shorter period of time in the
(another short-acting chemical) is given under the same circumstances if
is considered a possible diagnosis.
Magnetic Resonance (CMR) scan *
is a special kind of scan used to examine the structure of the heart and
the nature of its muscle. It uses a Magnetic Resonance scanner that
creates intense fluctuating magnetic fields around your body while you are
inside the scanner. This generates the signals that make up the pictures
produced. It is very useful for detecting the presence of fat and scarring
in the heart muscle that is associated with ARVC.
angiography and electrophysiological study (EPS)
on the results of the above tests, your doctor may suggest that you have
other tests such as coronary angiography or an electrophysiological study
(EPS). Both these tests are performed in an X-ray laboratory that allows
the body and any medical tools (such as cardiac catheter tubes or pacing
wires)to be seen using an X-ray
camera. You will be asked to lie down on a special moving table and will
be given a local anaesthetic in your groin. The doctor will then place
fine tubes, called cardiac catheters or electrodes, into blood vessels in
your groin. These are gently passed through to the heart.
coronary angiography the coronary arteries (the arteries that supply blood
to the heart muscle) are injected with a dye to reveal any furring or
blockages – coronary artery disease. (The ECG changes that are
characteristic of Brugada Syndrome or LQTS can sometimes be caused by
coronary artery disease.)
EPS (electrophysiological study) involves placing electrical leads inside
the heart to analyse its electrical properties and induce arrhythmias. It
may be useful in diagnosing Wolff-Parkinson-White Syndrome(WPW)and PCCD and
deciding on what treatment to give people with Brugada Syndrome. If the
extra pathway seen in WPW is detected at EPS it can be treated there and
then by ‘burning’ it away using high frequency radio waves. This
procedure is called ‘RF ablation’.
are other tests that may be used to provoke ECG features in LQTS such as
‘cold pressor tests’. A stimulus such as placing your hands in
ice-cold water can bring out the ECG features of the condition. This does
not appear to increase significantly the likelihood of making a diagnosis
but is still used at some centres.
testing is used to identify other common conditions that can cause
blackouts – such as Vasovagal Syndrome or simple fainting
– that tend to particularly affect young women and girls but have a very
low risk of causing sudden death. These symptoms are very similar to the
symptoms of more rare and potentially life-threatening conditions like the channelopathies, so it is important to discover the cause of the blackouts
so that the doctor can give appropriate treatment.
While you lie flat on a
table, your blood pressure, pulse and ECG are monitored. The table is then
tilted to an angle of 60 to 75 degrees and monitoring is continued. If
nothing happens, a spray of a substance called GTN is given under your
tongue as a stimulus and you will be monitored for another 10-15 minutes.
The table will then be returned to the flat position and the leads
disconnected. The whole test takes around 45 minutes. If your blood
pressure falls at the same time as you suffer your usual symptoms, this
means that you have Vasovagal Syndrome or a related condition.
most of the inherited conditions known to cause SADS, mutations of
specific genes have been detected and are thought to cause a specific
disease. So in principle, if we could identify these mutations, we would
be able to make a diagnosis in any DNA sample including any obtained from
SADS victims at their autopsy or from their relatives who have given
blood. Unfortunately this cannot be done at the moment because we don’t
have complete knowledge of all the genes involved in any condition.
example, only 6 in every 10 people known to have LQTS have mutations of
known identified genes. Also, many variations in the DNA code are found in
a large number of people and do not necessarily cause any disease. Most
families with LQTS have mutations specific to them (‘private’
mutations) which can also make it difficult to decide whether it is the
mutation that is causing the disease or not. As research progresses, more
genes will be identified and there will be better tools to decide whether
the impact of a mutation causes a disease.