Learning he had a serious heart condition had a fundamental effect on Neil Critchlow.

Just a few months after having a pacemaker fitted to control the abnormally slow and unsteady beating of his heart, the 43-year-old is still coming to terms with the changes in his life.

Mr Critchlow, from Yapton, near Arundel, had been feeling unwell for at least two years but doctors told him his symptoms, which included tightness around his chest and wrists at night and difficulty sleeping on his left side, were mainly down to stress.

Earlier this year, Mr Critchlow suddenly felt extremely unwell while at work and got a colleague to take him to the nearby accident and emergency department of St Richard's Hospital in Chichester.

Shortly after he arrived, he suffered two major heart attacks and needed to be resuscitated.

Doctors carried out tests and discovered Mr Critchlow was suffering from bradycardia.

Not enough oxygen was being pumped around his body, causing dizziness and loss of consciousness.

Mr Critchlow was fitted with a pacemaker which he will now need for the rest of his life.

He said: "I was surprised to learn what was wrong with me. I never knew it had anything to do with my heart.

"This had obviously been building up for some time before I had a serious attack.

I feel very lucky."

Mr Critchlow is now planning to set up a support group or web site for people suffering from the condition.

He said: "I know it is a common condition and is treatable with the pacemaker but it has still had a huge psychological effect on me.

"I'd been going around with this condition without knowing it for several months and it was like a timebomb inside me.

"In the end, something did go off but at least I was in hospital at the time.

"I don't want to scare people, just help them be aware of the condition and the symptoms and to help them if necessary."

Experts at the British Heart Foundation say people are generally fitted with pacemakers to speed up their heart rates following damage from a heart attack or disease.

The healthy adult human heart has a regular beat which is usually within a range of 50 and 100 beats a minute.

The heart has four chambers.

The two upper chambers are called the right atrium and the left atrium (atria) and the lower chambers are the right ventricle and left ventricle.

The electrical impulses of the heart are sometimes slowed down or delayed by an interruption in the heart's normal electrical activity.

This condition is known as heart block. At its most advanced stage, called complete heart block, no electrical impulses cross from the atria to the ventricles at all.

The atria and ventricles beat independently of each other. This means, even if the atria are not beating normally, the ventricles are still able to beat at their own rate of about 40 beats a minute.

However, at this slow rate, the reduced blood flow may cause breathlessness, fainting, blackouts or even confusion.

Heart block is usually caused by heart disease or ageing of the heart. Both can affect the way the heart's natural pacemaker works and the spread of electrical activity through the heart.

If the cause of the heart block can't be fixed, a pacemaker is the next option to maintain a person's heartbeat.

The electronic circuit in the pacemaker draws energy from the batteries and transforms this into a series of electrical impulses.

These are conducted down an electrode lead to the heart. Each electrical impulse discharged by the pacemaker stimulates the heart to contract and produce a heartbeat.

Pacemakers are also sometimes recommended for people with intermittently slow and fast heart rates or irregular heart rhythms to help maintain a regular heartbeat.

A pacemaker weighs only about 20-50g and is smaller than a matchbox.

The foundation says many people find having a pacemaker allows them to get back to their normal lifestyle or greatly improves their quality of life.

People can carry on with or take up most activities and sports but contact sports such as football are not usually advised as a pacemaker could be damaged.

Anyone interested in helping Mr Critchlow start a support group or web site can contact him at neil.critchlow@virgin.net or write to him at 15 Briar Close, Church Road, Yapton BN18 0ES.