Cardiac arrhythmias

What are cardiac arrhythmias?

The heart has its own electrical system that enables its four chambers to contract in an orderly manner.

Under normal conditions, each heartbeat begins in the sinus node, a small area in the right atrium that acts as a natural pacemaker. From there, the electrical impulse first travels through the atria and then reaches the ventricles, which pump blood to the lungs and the rest of the body.

An arrhythmia occurs when this impulse is generated in the wrong place, arises at an abnormal rate, or encounters an obstruction along its path. As a result, the heart may beat too fast, too slowly, irregularly, or with beats that occur ahead of the expected rhythm.

Not all variations in heart rate constitute a medical condition. The heart normally beats faster during exercise, when running a fever or when experiencing intense emotion, and may beat more slowly during sleep or in fit individuals.

To determine whether an arrhythmia is present, it is necessary to assess the rhythm, the circumstances in which it occurs and its potential impact on circulation.

Main types of arrhythmias

Arrhythmias can be classified according to the speed of the rhythm, the area of the heart where they originate and the electrical mechanism that causes them. This distinction is important because conditions that may cause similar symptoms carry very different risks and require very different treatments.

Rhythms that are too fast

Arrhythmias with an excessively rapid heart rate are called tachycardias. They can originate in the atria or in other structures located above the ventricles. This group includes, amongst others, atrial fibrillation, atrial flutter and supraventricular tachycardias.

There are also tachycardias that originate in the ventricles. Some of these can compromise the heart’s ability to pump blood and require urgent assessment.

Rhythms that are too slow

A slow heart rate is known as bradycardia. It can be a normal adaptation during sleep or in people who are physically fit. In other cases, it is caused by the heart’s natural pacemaker generating impulses too slowly or by the electrical signal not being transmitted correctly between the heart chambers.

Bradycardia becomes a cause for concern when it causes tiredness, dizziness, exercise intolerance or loss of consciousness.

Premature beats or extrasystoles

Extrasystoles are heartbeats that occur earlier than expected. They may be felt as a skip, a strong thud or a brief pause in the chest.

They are very common and, in many people without heart disease, have no significant consequences. When they occur very frequently, appear during exertion, cause significant symptoms or are associated with a heart condition, it may be necessary to investigate them in greater detail.

Potentially serious ventricular arrhythmias

Some disorders originating in the ventricles can prevent the heart from maintaining adequate circulation. Ventricular fibrillation, for example, causes disorganised electrical activity that prevents the heart from pumping blood effectively. It leads to loss of consciousness and circulatory arrest, and therefore requires immediate resuscitation and defibrillation.

It should not be confused with atrial fibrillation. Although their names are similar, their location, consequences and treatment are different.

Why do they occur?

There is no single cause for all arrhythmias. Some are due to a localised disturbance in the electrical system. Others arise as a result of heart disease, a metabolic change, a hereditary predisposition or certain medicines.

Sometimes small electrical circuits form, causing the electrical impulse to travel repeatedly through the same area. In other cases, certain cells begin to generate signals outside the natural pacemaker, or the conduction slows down and becomes blocked at some point.

There is no single cause for all arrhythmias.

Some are caused by a localised disturbance in the electrical system. Others arise as a result of heart disease, a metabolic change, a hereditary predisposition or certain medicines.

Sometimes small electrical circuits form, causing the electrical impulse to travel repeatedly through the same area. In other cases, certain cells begin to generate signals outside the natural pacemaker, or the conduction slows down and becomes blocked at some point.

Heart diseases

Arrhythmias can occur following a heart attack or in people with heart failure, valve disease, congenital heart defects or abnormalities of the heart muscle.

The scarring and structural changes caused by these conditions can alter the path of the electrical impulse and lead to abnormal heart rhythms.

Ageing can also cause changes in the sinus node and the conduction pathways, which is why some bradycardias and blocks are more common in older people.

External or potentially reversible causes

The heart rhythm can be disrupted by thyroid disorders, significant changes in potassium or magnesium levels, anaemia, fever, infections, dehydration or obstructive sleep apnoea.

Certain medicines, heavy alcohol consumption and stimulant drugs may also play a role. Where there is a reversible cause, identifying and treating it can reduce the frequency of episodes or make them disappear altogether.

Stress, lack of sleep and caffeine may contribute to palpitations or act as triggers in some people, but they should not be regarded as universal causes. The relationship must be assessed on a case-by-case basis, without imposing unnecessary restrictions.

Congenital or hereditary rhythm disorders

Some people are born with an accessory electrical pathway that allows the electrical impulse to follow a different route to the usual one. In other cases, there are hereditary disorders that affect the electrical functioning of the heart’s cells and may predispose individuals to certain arrhythmias, even though the heart’s structure is normal.

For this reason, it is important to inform your doctor if there is a family history of sudden death at a young age, fainting episodes of unknown cause, or hereditary heart rhythm disorders.

Most common symptoms

Some arrhythmias cause no discomfort and are discovered incidentally during an examination, an electrocardiogram or monitoring carried out for another reason. When symptoms do occur, the most common is an abnormal sensation of the heartbeat. The person may feel that their heart is racing, beating more strongly, stopping for a moment or beating irregularly.

The following may also occur:

• Fatigue or reduced exercise tolerance.

• Dizziness or a feeling of unsteadiness.

• Shortness of breath.

• Chest tightness or discomfort.

• A feeling of faintness.

• Temporary loss of consciousness.

Symptoms depend on the heart rate, the duration of the episode and the heart’s ability to maintain adequate circulation. The intensity of the palpitations does not always reflect the severity. An isolated premature beat may be felt very clearly, whilst some significant arrhythmias produce hardly any symptoms.

Therefore, these sensations must be interpreted in conjunction with the heart rhythm recording and the heart’s overall condition.

How they are diagnosed

Diagnosis is not simply a matter of checking whether the heart is beating fast or slow.

The aim is to identify the rhythm involved, where it originates and what effect it has on circulation. To do this, it is essential to link the symptoms to a recording of the heart’s electrical activity.

Medical history and examination

The assessment begins by asking the patient what they notice, when the episodes occur, how long they last and whether they start or stop abruptly.

It is also important to find out whether they occur at rest, during exercise, upon waking, after eating or whilst sleeping, and whether they are accompanied by dizziness, chest pain, shortness of breath or loss of consciousness.

The doctor will also review any previous medical conditions, medications, use of stimulants and family history of arrhythmias or sudden death.

Electrocardiogram

An electrocardiogram records the heart’s electrical activity via electrodes placed on the skin.

It can identify an arrhythmia if it is present during the test and detect certain abnormalities that predispose a person to developing one.

However, the standard recording lasts only a few seconds. When episodes are intermittent, an electrocardiogram carried out between two episodes may be completely normal.

Ambulatory monitoring

The type of monitoring is chosen according to the frequency of symptoms. A Holter monitor records the heart rhythm continuously for one or more days and is usually used when episodes are frequent.

When symptoms occur less regularly, event recorders or longer-term monitors may be used. If episodes are very infrequent but clinically significant — for example, fainting spells with no clear cause — an implantable recorder placed under the skin may be considered.

Put simply, the less frequent the symptoms, the longer the monitoring period may need to be.

Other tests

An echocardiogram examines the structure and mechanical function of the heart. It does not directly detect an intermittent arrhythmia, but it can reveal conditions that contribute to its occurrence or affect its severity.

Blood tests can be used to check for anaemia, thyroid disorders, kidney problems or changes in mineral levels.

A stress test can be useful when symptoms occur during exercise or when it is important to understand how the heart rhythm responds to exertion.

In selected cases, an electrophysiological study is carried out. Using catheters inserted into the heart, the specialist directly records the electrical activity, locates specific abnormal circuits and, in some cases, performs ablation during the same procedure.

Wristwatches and personal devices

Some watches and wearable devices can record the heart rate or produce a simple electrocardiogram (ECG) trace whilst symptoms are present.

These recordings can provide useful information, but they are no substitute for a medical assessment. They may trigger false alarms, fail to detect certain arrhythmias or prevent the precise identification of their mechanism.

Warning signs

Palpitations or an irregular heart rhythm require urgent medical attention when accompanied by:

• Fainting or loss of consciousness.

• Chest pain or tightness.

• Severe or sudden shortness of breath.

• Severe dizziness, confusion or marked weakness.

• A sudden deterioration in general condition.

These symptoms do not in themselves prove that a serious arrhythmia is present, but they may indicate that the heart is not maintaining adequate circulation. If you encounter an unconscious person who is not breathing normally, you must call the emergency services and begin the appropriate resuscitation procedures.

How are they treated?

Not all arrhythmias require treatment. Some simply need to be monitored, particularly when they do not cause any significant symptoms, do not affect the heart’s function and are not associated with an increased risk of complications. The decision depends on the type of arrhythmia identified, its duration and frequency, any symptoms, the presence of heart disease and the individual’s risk.

Medicines

Medicines can be used to reduce an excessively high heart rate, decrease the frequency of episodes or help maintain a stable heart rhythm.

The choice depends on the type of arrhythmia and the condition of the heart. A drug that is suitable for one person may be ineffective or contraindicated for another, so these treatments require individualised prescription and monitoring.

For some atrial arrhythmias, anticoagulation is considered to reduce the risk of stroke. This recommendation depends on the individual’s characteristics and risk, not merely on the detection of an irregular rhythm.

Cardioversion

Electrical cardioversion involves delivering a controlled, synchronised shock to restore a normal heart rhythm. It is carried out under monitoring and usually involves brief sedation. It may be used for certain atrial arrhythmias or when a rapid heart rhythm compromises circulation.

It is not suitable for all rhythm disorders and, in some cases, must be planned in conjunction with measures designed to prevent the formation or displacement of blood clots.

Catheter ablation

Catheter ablation enables a small area of tissue or an electrical circuit responsible for the arrhythmia to be located and modified. Catheters are usually inserted via a vein in the groin and guided to the heart. Once the source has been identified, energy is applied to interrupt the abnormal circuit.

For some types of tachycardia, it can offer a very effective solution. For other arrhythmias, it can reduce the frequency of episodes and improve symptoms, although there is a possibility that they may recur and that other treatments may need to be continued.

Implantable devices

A pacemaker monitors the heart’s rhythm and delivers small electrical pulses when it detects that the heart is beating too slowly. It is used to treat certain disorders of the sinus node or the electrical conduction system. It is not implanted solely because of a low heart rate, but only when there is a clinical indication based on the type of disorder and its symptoms.

The implantable cardioverter-defibrillator continuously monitors the heart rhythm and can treat certain dangerous ventricular arrhythmias by means of rapid pacing or an electric shock. Its aim is to prevent sudden death in people at high risk. It is not used for common palpitations or for most atrial arrhythmias.

If the episodes persist, it may be necessary to review the diagnosis, extend the monitoring period or consider a different approach. Increasing the medication is not always the solution.

Progression and possible complications

There is no single prognosis for all arrhythmias. Some occur in isolation and do not progress. Others cause intermittent episodes separated by long periods of normal heart rhythm, whilst some may become persistent or recur after treatment.

Possible complications depend on the type of arrhythmia and any associated conditions.

These include loss of consciousness, impaired heart function, heart failure, stroke in certain atrial arrhythmias, and cardiac arrest in some ventricular arrhythmias. These consequences are not specific to all arrhythmias, nor should they be considered inevitable.

Identifying the specific rhythm allows the actual risk to be assessed and helps to avoid both underestimating the risk and causing unnecessary concern.

In which conditions or situations are they particularly important?

Arrhythmias require particular attention when they occur in people who have previously had a heart attack, have heart failure, heart muscle disease, congenital heart defects or valve disorders.

They must also be carefully assessed during pregnancy, in people who take part in high-intensity sport, or where there is a family history of sudden death or inherited electrical heart disorders. The association with hyperthyroidism, sleep apnoea and certain medicines is particularly relevant because identifying these can alter treatment.

In people with atrial fibrillation, managing hypertension, obesity, diabetes, sleep apnoea and high alcohol consumption forms part of the overall management, in addition to specific treatment for the arrhythmia.

Which specialist treats arrhythmias

Primary care practitioners can carry out an initial assessment, look into possible triggers, request an electrocardiogram and determine whether a cardiological assessment is necessary.

The cardiologist identifies the type of arrhythmia, assesses its impact on the heart and determines whether follow-up, drug treatment or a specific procedure is required.

An electrophysiologist is a cardiologist who specialises in the heart’s electrical system and rhythm disorders. Their involvement is particularly important when more advanced monitoring, an electrophysiological study, ablation or the implantation of devices such as a pacemaker or a defibrillator is required.

At our hospital, we have an Electrophysiology and Arrhythmias Unit, specialising in the diagnosis and treatment of heart rhythm disorders. Its team of cardiologists, who are experts in electrophysiology, assess each case individually to determine which tests, follow-up or treatment are most appropriate.

Where there is an associated heart condition, a possible hereditary cause or another condition that may influence the arrhythmia, care can be coordinated with other specialist departments to provide a comprehensive approach.

Living with an arrhythmia

Being diagnosed with an arrhythmia does not necessarily mean that your heart is seriously ill or that you need to restrict all activity. Many people can lead an active life with regular check-ups or simple treatment. For others, identifying and treating the condition significantly improves symptoms and reduces the risk of complications.

It is helpful to know the specific name of the arrhythmia and to understand which symptoms are part of the condition. Where advised by your specialist, you can make a note of the duration of the episodes, the circumstances in which they occur and any associated discomfort.

Medication should not be stopped or altered without consulting a doctor, even if the episodes have ceased. It is also advisable to seek advice before taking decongestants, stimulants or supplements that may affect heart rhythm.

Not everyone needs to stop exercising, give up coffee or avoid certain activities. Recommendations should be tailored to the diagnosis, proven triggers and the condition of the heart.

Many people with arrhythmias can lead a stable and fulfilling life. The important thing is not to monitor every heartbeat, but to understand what the condition is, what follow-up is required and which symptoms warrant a more rapid assessment.