Occur in healthy people as well as those with heart disease.

In the absence of associated cardiac disease, have a benign prognosis.

If palpitation due to awareness of supraventricular extrasystoles is suspected, arrange:

• 24-h ECG monitoring to establish relation to symptoms, quantify frequency and assess for paroxysmal atrial fibrillation.
• Echocardiography to assess cardiac structure and function.

May occur in healthy people, but are more strongly associated with heart disease than supraventricular extrasystoles.

If palpitation due to awareness of ventricular extrasystoles is suspected, arrange:

• 24-h ECG monitoring to establish relation to symptoms, quantify frequency, and determine if monomorphic or polymorphic.
• Echocardiography to assess cardiac structure and function.
• Exercise ECG to establish effort tolerance, assess response of ventricular extrasystoles to exercise and whether ventricular tachycardia can be induced, and screen for ischaemic heart disease.

May reflect sinoatrial disorder with associated paroxysmal atrial fibrillation.

Look for other features of Wolff-Parkinson-White (WPW) syndrome: delta wave, widened QRS complex.

If WPW present, discuss management with a cardiologist before discharge.

Consider pulmonary hypertension or pulmonary embolism.

Consider Brugada syndrome (ECG shows RBBB pattern with coved or saddle back ST-elevation in leads V1-V3).

May reflect structural heart disease or conducting system disease.

Arrange echocardiography.

• Severe hypertension
• Aortic valve disease
• Hypertrophic cardiomyopathy

Usually reflect previous myocardial infarction (with associated risk of ventricular tachycardia (Chapter 40)).

May also be seen in hypertrophic cardiomyopathy or WPW syndrome (pseudoinfarct pattern).

• Right ventricular hypertrophy
• RBBB
• WPW syndrome
• Posterior myocardial infarction
• Duchenne muscular dystrophy with cardiomyopathy
• Normal variant

Long QT interval may reflect congenital channelopathy (long QT syndrome) or acquired disorder (due to drugs (see http://www.sads.org.uk/drugs-to-avoid/), or metabolic disorder (e.g. hypokalaemia or hypocalcaemia)), or a combination of these factors

QT interval >500ms is associated with high risk of polymorphic ventricular tachycardia (torsade de pointes) (Chapter 41).

Short QT interval may reflect congenital channelopathy (short QT syndrome) or acquired disorder (e.g. due to acidosis, hyperkalaemia or hypercalcaemia), or a combination of these factors

Short QT syndrome is associated with atrial and ventricular arrhythmias.

• Structural heart disease (e.g. severe aortic stenosis)
• Cardiomyopathies
• Acute coronary syndrome
• Myopericarditis
• Subarachnoid haemorrhage
• Stress cardiomyopathy