Ectopic beats / Extrasystoles

Electrical discharge originating from somewhere in the heart other than the sinoatrial node, resulting in systolic contraction of the heart.

Background/Epidemiology

  • Extra beats which interrupt the heart’s regular rhythm.
  • They can either originate from the atrium or ventricle
  • They can be associated with
    • underlying cardiovascular disease e.g. hypertension, coronary/ischaemic heart disease etc (see below)
    • electrolyte disturbances e.g. hypokalaemia, hypomagnesaemia, hypercalcaemia
    • drugs e.g. digoxin, TCAs, cocaine, amfetamines
    • alcohol
    • infection
    • stress; hyperthyroidism; caffeine
    • surgery

Atrial ectopics

  • Common in normal, healthy individuals (up to 60% of us will have at least one in 24 hours)
    • Can also occur when there is increased pressure on the atria e.g. cardiac failure, mitral disease.  If multiple, they can somewhat imitate atrial fibrillation.  They may also precede AF in some cases.

Ventricular ectopics

  • Also relatively common in normal individuals.  In the absence of cardiac disease, most ventricular extrasystoles are harmless.  However, some may be a sign of strain on the heart and ventricular extrasystoles during an exercise test may be concerning.  In those with frequent ectopics, ventricular function may be impaired.
    • More common in patients with structural heart disease e.g. post-MI, LVH, hypertrophic cardiomyopathy and congestive cardiac failure
    • Can be dangerous, particularly in patients with prolonged QT- may cause VT with Torsades de Pointes

Presentation

  • They may be an incidental finding on ECG (routine or otherwise) and the patient may be completely asymptomatic
  • Palpitations– usually describe a ‘skipped’ or a ‘missed’ beat (or ‘my heart stops’) followed by a pounding beat/thud (sometimes described as a somersault beat)
    • NB the thud/pounding beat my be the only thing they notice and can describe an ‘extra’ beat
    • Sometimes, patients also feel anxious.
  • Mostly, symptoms appear at rest and can be relieved by exertion.
    • The opposite is often a concerning history
  • Make sure to ask about other (cardiac/chest) symptoms e.g.
    • syncope/presyncope
    • chest pain
    • shortness of breath
    • coughing
  • Also check for any cardiac risk factors

Investigation

  • ECG
    • Atrial ectopic beats may appear as an abnormal P wave e.g inverted, which occurs earlier than expected (NB this may be hidden within the QRS complex of the preceding beat)
      • It may or may not result in transmission to the ventricles (and subsequent QRS formation)
        • If it does, the QRS is narrow
      • There is usually a prolonged duration between it and the next P wave (‘my heart stops’- this gives extra time for the heart to fill during diastole and the next beat is felt more forcefully, though this is not necessarily due to the heart working harder)
    • Ventricular ectopics appear as wide QRS complex with abnormal morphology, occurring prematurely i.e. earlier than would be expected for the next sinus impulse
      • There are also discordant ST segment and T wave changes
        • Abnormal repolarisation activity in which the ST segment and T wave are directed opposite to the main vector of the QRS complex (also seen in LBBB, paced rhythms and VT)
      • A full compensatory pause is also seen
      • PVC arising from the right ventricle have a LBBB morphology (dominant S wave in V1 (looks like W)- often with ST elevation and upright T waves); whilst those arising from the left ventricle have a RBBB morphology (dominant R wave in V1 (looks like M)- often with ST depression and T wave inversion)
      • Ventricular ectopics can occur in groups
        • Bigeminy- every two beats
        • Trigeminy- every three beats
        • Quadrigeminy- every four beats
        • Couplet- two in a row
        • Triplet- three in a row
  • It may be worth measuring TFTs, LFTs (alcohol), U&Es (electrolytes) and FBC (infection)
  • Ambulatory ECG e.g. 24 hour holter monitor or event recorder may be useful in picking up the abnormal activity if it is not present during the consultation
  • Other tests e.g. echocardiography, ETT etc are only really warranted if there are symptoms of chest pain or signs on examination

Management

  • Patients with no cardiac problems and no symptoms (or minor symptoms) can be reassured.  Reducing caffeine intake is recommended.
  • Atrial extrasystoles
    • If symptoms are troublesome, betablockers may be useful
  • Ventricular extrasystoles
    • For those without cardiac problems, but have problematic symptoms- generally no treatment is required, but regular follow-up, possibly with assessment of LV function (echo), is recommended
    • If frequent, unifocal and worse (e.g. causing VT) on exertion, consider catheter ablation
    • For those with cardiac disease, beta-blockers may be helpful (but may already be taken for cardiac problems)
      • Consider implantable defibrillators if at high risk
      • Catheter ablation may also be an option
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