An abnormal heart rate and/or rhythm of the heartbeat is called an arrhythmia, the most dangerous of which – ventricular fibrillation – is usually the end result of a heart attack.
However, a heart rate outside the usual range is not always a cause for concern. For example, everyone’s heart rate increases if they get excited or take exercise. Cause for greater concern is a rapid irregular heartbeat, although many people experience the odd irregularity and it has no significance. Arrhythmias of the heart’s upper chambers, the atria, are nowhere near as serious as irregularities in the beat of the ventricles, the lower and more powerful chambers.
There are two types of arrhythmias: tachycardias, in which the heart rate is too high, and bradycardias, in which the rate is too low.
What Are The Causes of Arrhythmias?
Most arrhythmias are caused by disease of the heart or its blood vessels. The most common underlying disorder is coronary artery disease. Less common causes include various heart valve disorders and inflammation of the heart muscle. Causes of arrhythmias that originate outside the heart include an overactive thyroid and a lack of potassium. Some drugs, such as bronchodilators and digitalis drugs, may cause arrhythmias, as may caffeine and tobacco.
What Are The Symptoms of Arrhythmias?
Symptoms do not always develop but if they do their onset is usually sudden and include:
- palpitations (awareness of an irregular heartbeat)
- light-headedness, sometimes leading t© loss of consciousness
- shortness of breath
- pain in the chest or neck like angina.
What Might Be Done for Arrhythmias?
- Electrocardiography (ECO).
- ECG over 24 hours to track the arrhythmia.
- Ambulatory ECG – a wearable device that’s worn for 24 hours and detects intermittent arrhythmias.
What Is The Treatment of Arrhythmias?
- Anti-arrhythmic drugs, such as digoxin, beta-blockers, calcium-channel blockers, amiodarone, flecainide and propafenone.
- Cardioversion (defibrillation) – restoration of a regular heart rhythm by passing an electrical current through the heart under
a general anaesthetic.
- Cardiac pacemaker.
Cardiac pacemakers stimulate the heart to maintain a regular heartbeat. Some pacemakers act continually, others send an impulse only when the heart rate falls too low.
A pacemaker is inserted just under the skin and stitched into position in the chest wall, usually under local anaesthesia. Two wires from the pacemaker are passed into the large vein above the heart (superior vena cava). One wire is guided into the right atrium and the other into the right ventricle.
The latest pacemakers have batteries that last 8-10 years and are not affected by interference from radar and microwaves.
This X-ray photograph from the back shows a cardiac pacemaker in position in the chest wall just below the right shoulder.