Extrasystoles

Extrasystoles were first described in 1890 by Sir James Mackenzie when he observed that the chambers of the heart could beat out of their correct order.¹

The normal heart rate and rhythm is 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 atrio-ventricular node which lies within the lower interatrial septum. Electrical impulses pass from here along the right and left bundles of His and excite the ventricular muscles causing their contraction. The sino-atrial node has a nerve supply and is hormone sensitive which allows regulation of the heart beat 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. Atrial extrasystoles occur when the discharge arises from the atria and ventricular extrasystoles occur when the discharge arises from the ventricles.

These are common in healthy people with normal hearts, especially with advancing age. They can also occur when there is increased pressure on the atria such as in cardiac failure or mitral valve disease and, in such cases, may occur prior to the development of atrial fibrillation. They are exacerbated by alcohol and caffeine.²

These can occur in people with normal hearts but are more commonly found in those with structural heart disease. They are the commonest type of arrhythmia that occurs after myocardial infarction. They may also occur in severe left ventricular hypertrophy, hypertrophic cardiomyopathy and congestive cardiac failure.²

Extrasystoles can occur frequently in people with completely normal hearts. In themselves, they do not cause any problems. However, they can also be a feature of certain cardiac disease. Usually, ventricular extrasystoles have no significance but rarely, they may induce ventricular fibrillation and can be associated with sudden cardiac death.

Structurally normal hearts

The British Heart Foundation Factfile from March 2005 states that ventricular ectopics, in the absence of structural heart disease or a family history of sudden death, are benign and do not require specialist intervention or specific drug therapy.³ Another source states that long-term follow-up of normal people with many extrasystoles reveals that they have the same life expectancy as normal people with no extrasystoles.² However, their prognostic significance is a matter of controversy. If extrasystoles, in people with otherwise normal hearts, occur during exercise and in the recovery period after exercise, an increased mortality risk does seem to exist.^4,5 A recent danish study has also shown that apparently healthy, middle-aged and elderly subjects with frequent ventricular premature complexes, defined as ≥ 30/hour, have a poor prognosis.⁶

Structurally abnormal hearts

In those with structurally abnormal hearts, the presence of ventricular extrasystoles does seem to impact mortality. Frequent ectopy marks an increased risk of sudden cardiac death and specialist advice should be sought.³ Those with more than 10 extrasystoles per hour after myocardial infarction have an increased risk of mortality, particularly sudden death. Frequent extrasystoles also have a negative prognosis in congestive cardiac failure.²

• Can occur in normal hearts where the prevalence of extrasystoles increases with age
• Acute myocardial infarction
• Structural heart disease, including valvular heart disease, cardiomyopathy, severe ventricular hypertrophy
• Congestive cardiac failure
• Electrolyte disturbances, including hypokalaemia, hypomagnesemia, hypercalcaemia
• Drugs, including digoxin, aminophylline, tricyclic antidepressants, cocaine, amphetamines
• Caffeine excess
• Alcohol excess
• Infection
• Stress
• Surgery
• Hyperthyroidism

• Palpitations are the main reported symptom. There is an awareness of a change in the force, rate or rhythm of the heart beat. Extrasystoles usually occur after a normal heart beat and are followed by a pause until the normal heart rhythm returns. Therefore, they may be felt as 'missed' or 'skipped' beats. Alternatively, they can be felt as a thud or strange sensation like a somersault in the chest. Other people may experience one or two extra heart beats. They can be uncomfortable and cause significant anxiety in some people.
• Light-headedness and syncope
• Atypical chest pain
• Fatigue
• As a coincidental finding on a routine ECG

• 12 lead ECG: The extrasystoles will only be picked up if they are occurring at the time that the ECG is performed.
• Ambulatory ECG monitoring: It is more likely that ambulatory ECG monitoring will pick up the extrasystoles.
• Echocardiography: This provides information about ventricular function and heart structure and can detect valvular and other abnormalities.
• Electrolyte levels: Including potassium, calcium and magnesium.
• Thyroid function tests: Hyperthyroidism should be treated if detected.
• Exercise stress testing: This may be needed if ischaemic heart disease is suspected or there is an exercise-induced arrhythmia.

ECG findings

In atrial extrasystoles there is a premature P wave which looks different from a normal P wave and may be hidden in the ST segment or T wave of the preceding sinus beat. It may be followed by either a normal QRS complex, or the PR interval may be prolonged, or the impulse may not be conducted at all.²

The ECG findings in ventricular extrasystoles show wide, bizarre-looking QRS complexes that are not preceded by a P wave.²

Structurally normal hearts

• Reassurance: In someone with an otherwise normal heart, the key management principle is reassurance that extrasystoles are not dangerous.
• Avoidance of caffeine, nicotine and alcohol: This may help reduce the frequency and sometimes abolish the extrasystoles.
• Drug treatment: Anxiolytic drugs may be helpful. Beta-blockers and calcium channel blockers may be needed in some symptomatic people. Care must be taken as the risk of treatment may outweigh the benefits as anti-arrhythmic drugs may actually be pro-arrhythmic. Specialist advice should be taken.
• Catheter ablation of the ectopic focus: This is rarely used and only if symptoms warrant.

Hearts with structural abnormalities

• Treatment of the underlying heart disease: This is the main priority, for example reperfusion after myocardial infarction and optimal treatment for congestive cardiac failure.
• Electrolyte balance: This should be monitored and corrected as necessary.
• Blood pressure: This should be controlled.
• Anti-arrhythmic drug treatment: The Cardiac Arrhythmia Suppression Trial was started with the aim of looking at the effects of arrhythmia suppression after myocardial infarction. It was terminated early after preliminary results showed that the suppression of ventricular arrhythmias did not improve survival and, in fact, caused an increase in mortality. The drugs involved in this trial were flecainide, encainide and moricizine.⁸ Beta-blockers are currently the drug of choice for the prophylaxis and treatment of arrhythmias post myocardial infarction.⁹
• Implantable cardiac defibrillators: These may be needed in patients deemed to be at high risk of sudden cardiac death.

Avoidance of aggravating factors such as stress, caffeine, alcohol and nicotine.