Extrasystoles

Synonyms: ectopic beats, premature beats, premature atrial or ventricular complexes

The normal heart rate and rhythm are determined by the sino-atrial node in the right atrium, which acts as the pacemaker for the heart. This node discharges electric current through the atria causing them to contract. The electric current then passes through the atrioventricular (AV) node which lies within the lower interatrial septum. Electrical impulses pass from here into the Purkinje's network, along the right and left bundles of His, and excite the ventricular muscles,  causing their contraction. The conduction system and myocardium have a nerve supply and are hormone sensitive (to catecholamines), which allows regulation of the heartbeat according to different activities, stress and excitement.

Extrasystoles are essentially extra beats, or contractions, which interrupt the normal regular rhythm of the heart. They occur when there is electrical discharge from somewhere in the heart other than the sino-atrial node. They are classified as atrial or ventricular extrasystoles according to their site of origin.

Epidemiology

Both atrial and ventricular extrasystoles are common at all ages.

Atrial extrasystoles

• These are common in healthy people with normal hearts. There are often seen on 24-hour Holter monitoring in over 60% of healthy adults.
• They can also occur when there is increased pressure on the atria such as in cardiac failure or mitral valve disease and may occur prior to the development of atrial fibrillation. They are exacerbated by alcohol and caffeine.

Ventricular extrasystoles

• These are common and can occur at any age.
• Premature ventricular contractions have been described in 1% of clinically normal people as detected by a standard ECG and 40-75% of apparently healthy persons as detected by 24- to 48-hour ambulatory ECG recording^[1].
• They are more common in those with structural heart disease. Ventricular extrasystoles are the most common type of arrhythmia that occurs after myocardial infarction. They may also occur in severe left ventricular (LV) hypertrophy, hypertrophic cardiomyopathy and congestive cardiac failure.

There are various classification systems for ventricular ectopics, in terms of their clinical risk, frequency or focus of origin.

Children

• Atrial extrasystoles are very common and only rarely associated with any disease.
• Ventricular extrasystoles are also common. In a structurally normal heart, they are almost always benign.
• Both are usually abolished by exercise.

Significance of extrasystoles

Extrasystoles can occur frequently in people with completely normal hearts and often do not cause any problems. However, they can also be a feature of certain cardiac diseases.

Significance of atrial extrasystoles

• Usually, atrial extrasystoles do not cause problems.
• However, a 2017 meta-analysis demonstrated that frequent premature atrial complexes were associated with an increased risk of stroke and death from all causes, cardiovascular diseases and coronary artery disease^[2].
• In some cases, runs of atrial ectopy can lead to paroxysms of atrial fibrillation .

Significance of ventricular extrasystoles

Patients without cardiac disease
Ventricular extrasystoles are often found in clinical practice. In the absence of heart disease, they are usually benign and the prognosis is thought to be good.

However, in a 2017 study 5,778 subjects who were pacemaker- and tachycardia-free received 24-hour ECG monitoring^[3]. Those who had a premature ventricular complex frequency of >12 beats per day had an increased risk of cardiac death attributable to heart failure and sudden cardiac death. The incidence rates for mortality and heart failure were significantly increased where there was a raised PVC frequency.

Patients with cardiac disease
In the presence of significant structural heart disease, frequent ventricular extrasystoles indicate an increased risk of sudden cardiac death, and specialist advice should be sought.

Risk factors for extrasystoles

• Can occur in normal hearts, where the prevalence of extrasystoles increases with age.
• Hypertension.
• Heart disease, including acute myocardial infarction, valvular heart disease, cardiomyopathy, ventricular hypertrophy and cardiac failure.
• Electrolyte disturbances, including hypokalaemia, hypomagnesaemia, hypercalcaemia.
• Drugs, including digoxin, aminophylline, tricyclic antidepressants, cocaine, amfetamines.
• Alcohol excess.
• Infection.
• Stress.
• Surgery.
• Hyperthyroidism.
• Possibly, central sleep apnoea is linked to ventricular ectopics.
• Stimulants such as caffeine may have a role, although this has not been proven for ventricular extrasystoles.

Presentation

May be a coincidental finding on a routine ECG.

Possible symptoms

• Palpitations are the main reported symptom:
  • There is an awareness of a change in the force, rate or rhythm of the heartbeat.
  • Extrasystoles usually occur after a normal heartbeat and are followed by a pause until the normal heart rhythm returns. Therefore, they may be felt as 'missed' or 'skipped' beats or 'feeling the heart has stopped'.
  • Alternatively, they can be felt as a thud or strange sensation like a somersault in the chest, or as extra beats. They can be uncomfortable and cause significant anxiety in some people.
• Symptoms are usually worse at rest and may disappear with exercise. Symptoms which increase on exercise are more worrying and significant.
• Other possible symptoms:
  • Syncope or near syncope (dizziness).
  • Atypical chest pain.
  • Fatigue.
  • There are case reports in which chronic cough ± syncope were the presenting symptoms of extrasystoles.

Possible signs

• There may be none.
• Variable or decreased intensity of heart sounds; the augmented beat following a dropped beat may be heard.
• Variable pulse rhythm.
• Visible jugular pulse (cannon a wave) from loss of AV synchrony.

Assessment

History

• Detailed history of the presenting symptom - including onset, duration, associated symptoms and recovery.
• Check for other cardiac symptoms including chest pain, breathlessness, syncope or near syncope (eg, dizziness), and arrhythmia symptoms (eg, sustained fast palpitations).
• If there is history of syncope, note that:
  • Exertional syncope should always raise alarm of a sinister cause.
  • Rapid recovery after the syncopal event, without confusion or drowsiness, is characteristic of cardiac syncope.
• Family history - for early cardiac disease or sudden death.
• Previous cardiac disease or coronary heart disease (CHD) risk factors.

Examination

• Cardiovascular system including blood pressure, heart murmurs and any signs of cardiac failure.

Investigations

In patients presenting with palpitations initial investigations are^[4]:

• Resting 12-lead ECG.
• FBC and TFTs.
• Electrolytes.

Other investigations:

• Serum calcium and magnesium.
• If symptoms have a long duration (many hours), advise the patient to attend their GP surgery or A&E for a 12-lead ECG during the next episode.
• Ambulatory ECG monitoring:
  • If symptoms are short-lived but frequent (>2-3 times per week), use a 24-hour Holter monitor.
  • If symptoms are short-lived and infrequent (<1 per week), use an event monitor or transtelephonic recorder.
• Echocardiography - to assess LV function and heart structure.
• Exercise stress testing - the relation of extrasystoles to exercise may have prognostic importance.
• Further non-invasive cardiac imaging may be required.

ECG findings

Atrial extrasystoles
These are premature P waves which look different from a normal P wave. They may be hidden in the ST segment or T wave of the preceding sinus beat. They may be followed either by a normal QRS complex, or the PR interval may be prolonged, or the impulse may not be conducted at all.

Ventricular extrasystoles
These are wide, abnormally shaped QRS complexes. Extrasystoles occurring at every second or third beat are called bigeminy or trigeminy respectively.

For examples see the ECG library (link provided under 'Further reading & references', below).

Which patients need referral?

In the context of palpitations or suspected arrhythmia, referral to secondary care is required for^[5]:

• Urgent symptoms (eg, chest pain, breathlessness or loss of consciousness) usually merit admission for assessment.
• Syncope or near syncope (especially exertional syncope - red flag).
• Symptoms suggesting a pathological tachycardia - eg, if there is an accurate description of very rapid heartbeat with sudden onset and offset.
• Significant ECG abnormality.
• Significant cardiac disease.
• Significant underlying problem - eg, endocrine or metabolic disorder, infection.
• Family history of sudden death or heart disease at a young age:
  • Unexplained sudden death at age >30, and all sudden deaths at age <30, should trigger cardiovascular evaluation of first-degree relatives (for heritable arrhythmias or cardiomyopathies).
  • A family history of early cardiac disease (age <40) suggests possible increased cardiac risk and further assessment may be warranted.
• Also refer if symptoms are troublesome, so that treatment options can be considered.

The urgency of referral depends on clinical judgement, taking into account the frequency and duration of symptoms and other medical conditions. Discussion with a specialist may be helpful if there is uncertainty about the urgency or usefulness of referral. Usually, refer to an arrhythmia clinic, if available.

Management

As an overview:

• Low-risk patients with no other cardiac problems and no symptoms (or minor symptoms only) can be reassured.
• Other patients (those with cardiac disease, cardiac risk or significant symptoms) will usually need further assessment, treatment or follow-up.
• Treatment options are:
  • Drugs - beta-blockers (eg, atenolol, metoprolol).
  • Radiofrequency catheter ablation of the ectopic focus (in suitable cases).
  • Patients with a high intake of caffeine or other stimulants may be advised to try reducing their intake, to see whether or not this improves their symptoms or the extrasystoles.

Management of atrial extrasystoles

• Manage cardiovascular risk factors and give lifestyle advice^[5].
• If symptoms are troublesome, try beta-blockers (atenolol or metoprolol).
• Atrial extrasystoles arising from the pulmonary veins may be treatable by the procedure of pulmonary vein isolation. 

Management of ventricular extrasystoles

This depends on^[5]:

• Whether there is underlying heart disease.
• The frequency of the extrasystoles and whether ventricular tachycardia has been documented.
• The frequency and severity of symptoms.

Lifestyle advice

Advise about driving and work if appropriate.

The Driver and Vehicle Licensing Agency (DVLA) regulations state that:

For Group 1 entitlement, driving must cease if the arrhythmia has caused or is likely to cause incapacity. Driving may be permitted when the underlying cause has been identified and controlled for at least four weeks.

For Group 2 entitlement, the driver is disqualified from driving if the arrhythmia has caused or is likely to cause incapacity. Driving may be permitted when the arrhythmia is controlled for at least three months.