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Kingdom of Saudi Arabia
12 October 2024 | 06:08 ص
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How does the heart beat normally?
To understand how a pacemaker works, it helps to know
how the heart beats normally, and how it pumps blood
around your body.
A normal adult heart has a regular heartbeat which is
usually between 60 and 100 bpm (beats per minute)
while you are resting. When you exercise, this may go up
to a much higher rate, depending on your age and level
of fitness.
Your heart has its own ‘natural pacemaker’, called the
sinus node. This sends out regular electrical impulses
that travel through an ‘electrical pathway’ in the heart,
causing the chambers of your heart to contract and
pump the blood through the heart and out to your lungs
and the rest of your body. (See the illustration on the
next page.) This is what causes you to feel a pulse.
Why do I need a pacemaker?
If there is a problem with the electrical conduction
system in your heart, you may need to have a pacemaker
implanted. This could be because you have one of the
following conditions.
• Sick sinus syndrome (sinus node disease) is when the
sinus node (your heart’s own pacemaker) stops working
properly.
• Heart block (also called AV block or atrioventricular
block) is when there is a problem with the AV node.
There is a delay or block in the electrical impulses
travelling between the atria and the ventricles.
• Atrial fibrillation is an abnormal and often irregular heart
rhythm that originates in your atria (the top two chambers
of the heart). The rhythm may be too fast, or too slow. If
the atrial fibrillation causes your heart to beat too slowly,
you may need a pacemaker.
• Cardio-inhibitory syncope is when someone collapses
and temporarily loses consciousness. It happens when
there is a pause of a few seconds in the heart rhythm.
This can happen in people with atrial fibrillation.
• Heart failure which causes ‘dyssynchrony’, which is when
the ventricles (the bottom two chambers of the heart)
don’t pump in time with each other.
How does a pacemaker work?
A pacemaker contains a pulse generator (the pacemaker
box) and one, two or three electrode leads. These leads
are thin pieces of insulated wire that deliver electrical
impulses to and from the heart. Pacemakers with one
lead are called single-chamber pacemakers. Pacemakers
with two leads are called dual-chamber pacemakers.
Pacemakers with three leads are called bi-ventricular
pacemakers.
The pacemaker box is made up of several different
parts including the power supply (the battery) and the
electronic circuit. It contains special software and memory
so that it can monitor and store information about your
heart rhythm and heart rate. It also has a special circuit
that allows the pacemaker to be checked and altered by a
computer at the hospital.
The pacemaker is contained within a protective metal
casing. It weighs only about 20 to 50 grams (1 to 2
ounces) and is smaller than a matchbox. (See the
photo on the front cover.) Sometimes the pacemaker
is combined with an ICD (implantable cardioverter
defibrillator) – a device, similar to a pacemaker, that can
treat fast
Which type of pacemaker will I need to
have?
As a general guide, the type of pacemaker you have will
depend on the reason why you need it.
If you have sick sinus syndrome
The type of pacemaker most often used for this condition
is a dual-chamber pacemaker. For some people, a
single-chamber pacemaker may be used instead – for
example, if there is no evidence of heart block.
If you have heart block
If you have heart block, you will most probably have
a dual-chamber pacemaker inserted, although this
choice will depend on how well your sinus node (your
heart’s natural pacemaker) is working. If you have heart
block and also have chronic atrial fibrillation or another
underlying medical condition, your cardiologist may
insert a single-chamber pacemaker.
How is the pacemaker fitted?
Some people have a pacemaker implanted as a day case
(which means that you don’t need to stay in hospital
overnight), while others have an overnight stay in
hospital. Sometimes people may need to stay in hospital
for a few days.
The procedure usually takes about an hour, but it can
take longer for some people, particularly those who are
having a bi-ventricular pacemaker. It is usually done with
sedation and a local anaesthetic, so you will feel relaxed
during the procedure.
Your pacemaker will be inserted under very sterile
conditions, but you will be given some antibiotics before
and after having the procedure. This is to reduce your risk
of developing an infection.
Most pacemakers are fitted by transvenous implantation
(which is also called endocardial implantation). In a very
small number of people, epicardial implantation may be
used instead.
Will I be able to feel the pacemaker inside me?
Some people are aware of the pacemaker being there, but
get used to it quickly. You shouldn’t feel the pacemaker
working. Some people may experience a ‘twitch’ when
their pacemaker is working. If this happens, tell your
pacemaker clinic so they can change the settings to stop
this happening.
At first, your pacemaker may feel uncomfortable when
you lie in certain positions, or perhaps when wearing
certain clothes, but it can’t be damaged by either of these
things.
Can everyday equipment interfere with
my pacemaker?
Pacemakers are made to the highest standards and
are rigorously tested. As a result, problems are rare. All
pacemakers have a protective outer metal casing to
shield them from outside interference. And they have a
special circuit to detect and remove unwanted electrical
activity.
For more information about interference, read the
information booklet about your specific type of
pacemaker that you were given after you had your
pacemaker implanted. If you have any questions about
what you can and can’t do, contact your pacemaker clinic
or the pacemaker manufacturer.
At home
Electrical equipment that you use at home – such as
hairdryers and microwave ovens – will not be a problem,
as long as you use them at least 15 centimetres (6 inches)
away from your pacemaker. You should also be able to
use household tools such as drills, mowers and electric
screwdrivers, as long as they are in good condition and
well maintained.
Dr.Husam Karrar
Senior House Officer