Cardiac arrhythmias

Introduction

Arrhythmias are disorders of cardiac rate, rhythm and conduction.
They can be classified as bradyarrhythmias (heart rate < 60 per minute) and tachyarrhythmias (heart rate > 100 per minute).
Bradyarrhythmias include sinus bradycardia, sinus pauses and atrioventricular blocks.
The tachyarrhythmias can further be classified into supraventricular and ventricular arrhythmias, based on their site of origin.
Tachyarrhythmias include atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia, ventricular tachycardia and ventricular fibrillation.
Prior to drug treatment of a suspected cardiac arrhythmia, a 12-lead ECG must be done to confirm the rhythm abnormality.
It is dangerous to use an antiarrhythmic drug without doing an ECG.
Refer symptomatic patients to hospital immediately.
The choice of drug treatment depends on the type of arrhythmia and severity of symptoms.

Causes of Cardiac arrhythmias

The causes of Cardiac arrhythmias include the following:

  1. Rheumatic heart disease
  2. Other valvular heart diseases
  3. Hypertensive heart disease
  4. Ischaemic heart disease
  5. Thyrotoxicosis
  6. Hypothyroidism
  7. Cardiomyopathies
  8. Complete heart block
  9. Electrolyte abnormalities particularly hypokalaemia
  10. Pericardial disease
  11. Drugs
  12. Smoking, alcohol, coffee, tea, etc.
  13. Pulmonary embolism.
  14. Post cardiac surgery
  15. Idiopathic

Symptoms of Cardiac arrhythmias

  • Palpitations
  • Dizziness
  • Chest discomfort/pain
  • Fatigue
  • Difficulty in breathing
  • Sudden collapse
  • Sudden death

Signs of Cardiac arrhythmias

  • Rate may be fast, slow or normal
  • Pulse
  • Rhythm

Regular

  • Sinus tachycardia
  • Sinus bradycardia
  • Complete heart block
  • Supraventricular tachycardia
  • Ventricular tachycardial

Regularly irregular

  • Supraventricular or ventricular ectopic beats

Irregularly irregular 

  • Atrial fibrillation
  • Atrial fibrillation Atrial flutter (with variable atrio-ventricular block)
  • Multiple supraventricular or ventricular ectopic beats
  • Pulse deficit (apical rate faster than radial pulse rate; seen in fast atrial fibrillation or flutter)
  • Hypotension or blood pressure may be unrecordable
  • Signs of heart failure (may be present)

Investigations

  • 12-lead ECG
  • Serum electrolytes (including magnesium, calcium)
  • Thyroid function tests
  • Chest X-ray
  • Ambulatory ECG (Holter)
  • Echocardiography

Treatment for Cardiac arrhythmias

Objectives

The treatment objectives of Cardiac arrhythmias include the following

  1. To control ventricular rate
  2. To restore sinus rhythm
  3. To relieve symptoms
  4. To improve functional capacity and quality of life
  5. To prevent or treat associated complications
  6. To treat the underlying condition e.g. thyrotoxicosis
  7. To prevent stroke or systemic thromboembolism
  8. To reduce morbidity and mortality

Non-pharmacological treatment

  • Reassure the patient
  • Avoid excessive intake of alcohol, coffee or tea and stop smoking (if these are possible precipitating factors)
  • Massage of the carotid sinus on one side for a few seconds. This may terminate an attack of paroxysmal supraventricular tachycardia
  • Electrical cardioversion

Pharmacological treatment

A. Fast atrial fibrillation or atrial flutter-for rate control

1st Line Treatment
Evidence Rating: [A]
Atenolol, oral,
Adults: 50-100 mg daily
Children:

  • 12-18 years; 25-50 mg daily
  • 1 month-12 years; 12.5-50 mg daily

Neonates: Refer to a paediatrician

Or

Bisoprolol, oral,
Adults: 2.5-10 mg daily
Children: Safety not establised in children

Or

Metoprolol tartrate, oral,
Adults: 50-100 mg 8 or 12 hourly daily (max. 300 mg daily)
Children

  • 12-18 years; 50 mg 8 or 12 hourly daily (max. 300 mg daily)
  • < 12 years; refer to a paediatrician

Note

Avoid if beta-blockers are contraindicated e.g. bronchial asthma, hypotension

Or

Verapamil, oral,
Adults: 40-120 mg 6-8 hourly (max. 480 mg daily)
Children: Refer to a paediatrician
Note

Avoid use in patients already on beta-blocker

2nd Line Treatment
Evidence Rating: [A]
Digoxin, oral,
Adults: 125-250 micrograms daily
Children: Refer to a paediatrician

B. Fast atrial fibrillation or atrial flutter-for rhythm control

This is required to restore sinus rhythm.

Refer to a cardiologist, physician specialist or paediatrician as appropriate.

C. Paroxysmal supraventricular tachycardia

1st Line Treatment
Evidence Rating: [A]
Atenolol, oral,
Adults: 50-100 mg daily
Children:

  • 12-18 years;
  • 1 month-12 years;
  • Neonates: Refer to a paediatrician

Or

Bisoprolol, oral,

  • Adults 2.5-10 mg daily

Children: Safety not established in children

Or

Metoprolol tartrate, oral,
Adults: : 50-100 mg 8 or 12 hourly daily (max. 300 mg daily)
Children

  • 12-18 years; 50 mg 8 or 12 hourly daily (max. 300 mg daily)
  • <12 years; refer to a paediatrician

Note

Avoid if beta-blockers are contraindicated e.g. bronchial asthma, hypotension

Or

Verapamil, oral,
Adults: 40-120 mg 6-8 hourly (max. 480 mg daily)
Children: Refer to a paediatrician
Note

Avoid use in patients already on beta-blocker

 
2nd Line Treatment.
Evidence Rating: [A]
Digoxin, oral,
Adults: 125-250 micrograms daily
Children: Refer to a paediatrician

D. Prevention of stroke or systemic thromboembolism in atrial fibrillation or flutter

Patients should be given long-term anticoagulation.
(See options for long-term anticoagulation on ‘DVT‘ or ‘Pulmonary Embolism‘).

Referral Criteria

Refer all patients to a cardiologist, physician specialist or paediatrician for further evaluation and management after the initial treatment.
All symptomatic patients, as well as those who cannot have an ECG done or interpreted, or who present with heart failure, should be referred immediately.