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By: Ikedi Ani-okoye

Abnormal heart rate

Abnormal heart rate or rhythm, also known as arrhythmia, can cause palpitations and breathlessness. Occasional awareness 01 one's heartbeat is a normal reaction to fear or excitement, or it may be a sign of too much coffee or alcohol. Frequent palpitations may indicate disease, so this should always be investigated by a doctor.

Arrhythmias are common after a heart attack, when the heart muscle is in a state of Irritability; this is what often causes the heart to stop working altogether, otherwise known as cardiac arrest.

Everyone occasionally feels their heart "leap" - hopefully from love rather than fear, and sometimes for no apparent reason at all. That sudden thump or feeling that the heart has missed a beat is called a palpitation. This is only worrying when it becomes more than an occasional symptom. Frequent palpitations may be an indication of an illness, such as an overactive thyroid or heart disease. However, panic attacks and anxiety may also be the cause of palpitations, as may be over-indulgence in coffee, cigarettes, alcohol or illegal drugs.

Types of arrhythmia

Heart rate and rhythm may be eitilcr too high or too low. The most serious type of arrhythmia is ventricular fibrillation, which is caused by too high a heart rate in the ventricles (the lower heart chambers). This is the most common cause of death after a heart attack. In ventricular fibrillation, the heart "quivers", rather than

Cardiac arrest

A life-threatening emergency situation, cardiac arrest occurs when the heart stops beating. The most common cause is a heart attack, but there are many other causes. After a car accident, cardiac arrest may occur because of massive blood loss, or a collapsed lung. Cardiac arrest may occur in a pulmonary embolism, a condition in which blood clots form in the lungs. Electrocution or a lightning strike injury may cause a cardiac arrest. Asthmatics may have a cardiac arrest during a severe asthma attack.

Cardiopulmonary Resuscitation

Cardiopulmonary resuscitation is not a definitive life-saving treatment for cardiac arrest, and can only keep blood pumping around the body until specialized help is available. The only effective treatment is "defibrillation", in which a high-energy electric shock is applied to the chest wall. The sooner this is done after cardiac arrest, the more likely that the heart will return to a normal rhythm and resume pumping blood around the body.

Until recently defibrfilators could only be used by trained paramedics and doctors. However, a new development has been launched in some areas. This is the automated external defibrillietor, which requires some training but is much more user-friendly than the hospital types, and prompts the correct sequence of actions for its use.

The rescuer needs to recognize that cardiac arrest may have occurred, and then to attach two sticky pads to the chest wall and switch on the machine. Such equipment is already kept at some busy public places, such as sports stadia, leisure centres and airports. This new ttechnology means that the average citizen, with minimal training, will be able to save a life.

How the heart rate is regulated

Heart is a muscle that contracts and relaxes continuously and rhythmically between 60 and 80 times a minute, on average, throughout our lives. Heart muscle is unique because it has its own conduction system so it contracts without any outside control Chemicals such as adrenaline or caffeine can alter the heart rate, as can anxiety, or a drop in blood pressure.

Each contraction of the heart muscle is controlled from within, by the conduction system. This system comprises groups of cells that charge up and fire spontaneously. One group of cells, called the sinoatrial (S/A) node, sets the rhythm for the rest of the heart - it acts as the heart's internal pacemaker. An electrical wave spreads from the S/A node through the atria, until it reaches a second node called the atrioventricular node. It then continues through a right and left branch, until it reaches the outermost parts of the heart. This contains specialized Purkinje fibres a wiring system that transmits the impulses.