Heart rhythm disturbances

Symptoms and causes

What is it?

Heartbeats follow successively in a regular tempo. At rest, the heart beats 60-70 times a minute. With exertion, the heart beats a lot faster to compensate for an increased need for oxygen: 150-180 times a minute.

The heart's function is driven by an electrical impulse. Any abnormality of this electrical activity can lead to arrhythmias (heart rhythm disturbances).

The most common disturbances are an abnormally slow heart rate (bradycardia), an abnormally fast heart rate (tachycardia) and an irregular heart rate (arrhythmia). Most heart rhythm disturbances are only uncomfortable or bothersome. Only a minority of them are life-threatening.

Some heart rhythm disturbances are the result of a congenital defect in the heart's electrical system. For other heart rhythm disturbances, no specific cause can be identified.

Symptoms

Heart rhythm disturbances often go unnoticed and are only discovered by accident during a routine examination. They often lead to palpitations, dizziness or even loss of consciousness (syncope).

Types of heart rhythm disturbances:

Atrioventricular block

When the communication of electrical signals from the anterior chambers to the heart chambers is temporarily or permanently interrupted, it leads to a quite slow or sometimes irregular heart rhythm. The most common symptoms are fatigue, shortness of breath, dizziness and loss of consciousness (syncope). If the conduction disturbance is the result of a treatment with medication, it is often preventable. If it is not, then an implanted pacemaker is necessary.

Anterior chamber tachycardia (atrial tachycardia)

In the heart's anterior chamber, fast electrical impulses are formed that temporarily override the heart rhythm and make the heart beat a regular 140-190 beats per minute. The heart rhythm disturbance starts and stops abruptly. Sometimes, the periods come quite frequently. The heart rhythm disturbance is usually brief and does not cause problems. In this case, no treatment is necessary. With long-lasting and very bothersome episodes, treatment with medications or even an ablation may be recommended.

An ablation is recommended when tachycardia happens frequently, if it causes significant symptoms and if anti-arrhythmia treatment has not proven effective or is not desired. The chance of a successful ablation of this heart rhythm disturbance is somewhat lower than for other supraventricular tachycardias.

AV nodal tachycardia (AVNRT)

This heart rhythm disturbance can only occur if an extra conduction pathway is present in the AV node. In this case, the electrical current may remain circulating in the junction between the anterior chambers and the chambers. This results in the rapid and simultaneous contraction of the anterior chambers and chambers.

Patients who have this condition feel their heart thumping and experience a feeling of tightness in their throat. Sometimes they feel dizzy, but only rarely do they tend to lose consciousness.

The preferred treatment is an ablation of the extra conduction pathway in the AV node. The chance of a permanent AV block (and thus the need for a pacemaker implant) after the ablation of an AV nodal tachycardia is 0.5%.

Wolf-Parkinson-White-syndrome

Wolff Parkinson White syndrome is a congenital defect in which there is an extra electrical connection, in addition to the AV node, between the anterior chambers and the heart chambers. In certain circumstances, this 'accessory' conduction pathway can lead to a 'circle tachycardia' (re-entry tachycardia): an electrical impulse will continue circulating in a circuit made up of the anterior chambers, the AV node, the chambers and the accessory bundle.

If an atrial fibrillation occurs, the atrial impulses are also transmitted to the chambers very rapidly using the accessory bundle. This can lead to a life-threatening atrial or ventricle fibrillation.

An accessory bundle qualifies for electrophysiological testing or possible ablation:

in case of a tachycardia
in case of a syncope
in case the accessory bundle keeps transmitting with high heart rates
with at-risk professions

Atrial flutter

Rapid but regular electrical circuits in the anterior chambers can arise around the atrioventricular valves, around the exit of the pulmonary veins and around (surgical) scarring. Whether or not they cause symptoms depends on the velocity with which the electrical impulses are transmitted to the chambers using the AV node.

The treatment of atrial flutter has the following three goals:

prevent heart failure by optimising the ventricular response to the atrial flutter
prevent clot formations in the heart, thereby reducing the risk of heart attack and stroke
repair the sinus rhythm This can be achieved through medication, an electrical cardioversion or an ablation.

Atrial fibrillation

Atrial fibrillation (AF) is one of the most common heart rhythm disturbances. They are created by rapid impulses coming from the pulmonary veins that discharge into the left atrium. These impulses then circulate in total chaos, causing the atria to ‘flutter’. Whether or not it causes symptoms depends on the velocity with which the electrical impulses are transmitted to the chambers over the AV node.

The treatment for atrial fibrillation has three goals:

prevent heart failure by optimising the ventricular response to the atrial fibrillation
prevent clot formations in the heart, thereby reducing the risk of heart attack and stroke Medications can help reduce the blood's capacity to coagulate.
repair the sinus rhythm This can be achieved through medication, an electrical cardioversion or an ablation.

Ventricular tachycardia

Ventricular tachycardia happens when there is rapid electrical activity in the heart muscle. Although this heart rhythm disturbance occurs in a normal heart, it is usually caused by a previous heart attack or by heart muscle disease. Due to the rapid and uncoordinated contraction of the ventricles, blood cannot be circulated efficiently. A ventricular tachycardia can turn into a life-threatening ventricular fibrillation.

The patient usually experiences sudden dizziness or loss of consciousness. Treatment may consist of medication, a cardioversion, an ablation or implantation of a defibrillator.

Ventricular fibrillation

Ventricular fibrillation is total electrical chaos in the heart chambers. The heart's pumping function stops as a result of this chaos. This leads to cardiac arrest. Ventricular fibrillation usually occurs in the event of sudden damage to the heart muscle, such as a heart attack.

Ventricular fibrillation can be treated with an external defibrillator while administering resuscitation (cardiac massage, ventilation). Recurrent cardiac arrest can be prevented by implanting aninternal defibrillator.

Extra systoles

Extra systoles are redundant heartbeats that disturb the normal heart rhythm of the pacemaker cells (sinus node). The cells that generate the extra systoles can be located in the atrium or in a ventricle. Most extra systoles are more bothersome than dangerous. Sometimes, though, they can be early symptoms of serious heart disease. They are usually palpable as a (perceptible) short interruption of the heartbeat, followed by a harder beat.

Extra systoles are only treated with medication if they are extremely uncomfortable for the patient. Ventricular extra systoles are sometimes considered for ablation if they are numerous (a minimum of 30% of the total number of heartbeats), such that they lead to heart failure or if there are complaints of the heart pounding.

Brugada syndrome

Brugada syndrome is a congenital condition with an increased risk of sudden heart death. If one of the parents is a carrier of the gene, there is a one in two chance that a child will have the syndrome. The incidence varies from five to 50 per 10,000.

The syndrome can manifest as dizziness, sudden syncope or even sudden death, even at a young age. The condition is characterised by an abnormal electrocardiogram, which is sometimes only detected after provocative testing.

Symptomatic patients must be protected with an implanted internal defibrillator.

Arrythmogenic right ventricular dysplasia/cardiomyopathy

If the wall of the right ventricle is fatty or if there are fibrous changes, it is more susceptible to developing a ventricular tachycardia that can lead to a pounding heart, dizziness, syncope, heart failure and even sudden death.

The condition is hereditary and follows a progressive trajectory with symptoms first arising during adolescence. The incidence is estimated at 1 per 5000, and is higher among athletes.

The diagnosis is made based on multiple measures: electrocardiogram, Holter monitor, medical imaging using electrocardiography and MRI and a biopsy that can show tissue degeneration.

Treatment consists of medication, ablation and protective treatment by implanting an internal defibrillator.

Long QT syndrome

Long QT syndrome includes conditions characterised by an abnormality in the electrocardiogram: a lengthened interval between the QRS wave and the end of the T wave. The root cause is an abnormal influx of electrolytes to the heart cells, which make them susceptible to life-threatening heart rhythm disturbances, such as ventricular tachycardia or fibrillation.

The condition can be inherited as a genetic condition or it may develop as a result of certain medications.

If the cause cannot be managed, the implantation of a defibrillator should be considered.

Diagnosis and treatment

How do we make a diagnosis?

For useful advice related to how to manage a heart rhythm disturbance, it is crucial to record this disturbance. This is done with the help of:

the electrocardiogram for heart rhythm disturbances that are always present
a stress test (cycling test) for disturbances that are only present with physical activity
a rhythm recording of one or multiple days: Holter or Event recorder
a sleep study to detect sleep apnoea syndrome
a multi-year rhythm recording: internal recorder, for a heart rhythm disturbance that only occurs once in a while
electrophysiological testing: if it is not possible to record a heart rhythm disturbance, the disturbance can sometimes be detected and analysed with catheters in the heart.

Treatment

Numerous heart rhythm disturbances are harmless and do not require treatment. Others can be well managed with medications or with an electrical cardioversion. For other heart rhythm disturbances, devices must be implanted in or around the heart: pacemakers and defibrillators.

For some patients, an ablation may treat the electrical system of the heart itself.