Bradycardia DDx

Overview

• Bradycardia refers to heart rate <60/min in an adult
• Bradycardias are classified as regular or irregular, narrow complex or wide complex
• The underlying causes of bradycardia are legion

Types of bradycardia

Narrow complex bradydysrhythmias

• Regular
  • Sinus bradycardia
  • Junctional bradycardia
  • Complete AV block (junctional escape)
  • Atrial flutter with high degree block
• Irregular
  • Sinus arrhythmia, pause or arrest
  • Sinoatrial exit block (second degree)
  • Atrial fibrillation with slow ventricular response
  • Atrial flutter with variable block
  • Second degree AV block, type I
  • Second degree AV block, type II

Wide complex bradydysrhythmias

• Regular
  • Idioventricular rhythm
  • Complete AV block (ventricular escape)
  • Sinoventricular rhythm
  • Regular bradycardias with aberrancy or bundle branch block
• Irregular
  • Second degree AV block, type I
  • Second degree AV block, type II
  • Sinoatrial exit block (second degree) with bundle branch block
  • Irregular bradycardias with bundle branch block

Differential diagnosis of the underlying causes of bradycardia

• Cardiac disease
  • Myocardial ischaemia / infarction
  • Myocarditis
  • Congenital disorders
  • Cardiomyopathies
  • His-Purkinje fibre degeneration
• Hypoxia
• Electrolyte disturbance (e.g. hyperkalemia)
• Medications, poisonings and toxic exposures (e.g. digoxin, beta blockers, calcium channel blockers, amiodarone, clonidine, organophosphates)
• Hypothermia
• Hypothyroidism
• Raised intracranial pressure (Cushing response)
• Infections (e.g. Lyme disease, diphtheria, typhoid fever)
• Autoimmune (e.g. systemic lupus erythematosis)
• Infiltrative disorders (e.g. sarcoidosis, amyloidosis)
• Physiological causes (e.g. athletes, vagal stimuli)

References and Links

• ECG Library – ECG Rate
• ECG Library – Sinus Bradycardia

CCC Differential Diagnosis Series
NEURO	Anosmia, Ataxia, Blepharospasm, Bulbar and Pseudobulbar palsy, Central Pontine Myelinosis, Cerebellar Disease, Chorea, Cranial nerve lesions, Dementia, Dystonia, Exophthalmos, Eye trauma, Facial twitches, Fixed dilated pupil, Horner syndrome, Loss of vision, Meningism, Movement disorders, Optic disc abnormality, Parkinsonism, Peripheral neuropathy, Radiculopathy, Red eye, Retinal Haemorrhage, Seizures, Sudden severe headache, Tremor, Tunnel vision
RESP	Bronchial breath sounds, Bronchiectasis, High airway pressures, Massive haemoptysis, Sore throat, Tracheal displacement
CVS	Atrial Fibrillation, Bradycardia, Cardiac Failure, Chest Pain, Murmurs, Post-resuscitation syndrome, Pulseless Electrical Activity (PEA), Pulsus Paradoxus, Shock, Supraventricular tachycardia (SVT), Tachycardia, VT and VF, SVC Obstruction
GIT	Abdominal distension, Abdominal mass, Abdominal pain, Asterixis, Dysphagia, Hepatomegaly, Hepatosplenomegaly, Large bowel obstruction, Liver palpation abnormalities, Lower GI haemorrhage, Malabsorption, Medical causes of abdominal pain, Rectal mass, Small bowel obstruction, Upper GI Haemorrhage
GUT	Genital ulcers, Groin lump, Scrotal mass, Urine colour, Urine Odour, Urine transparency,
MSK	Arthritis, Shoulder pain, Wasting of the small muscles of the hand
DERM	Palmar erythema, Serious skin signs in sick patients, Thickened Tethered Skin, Leg ulcers, Skin Tumour, Acanthosis Nigricans
ENDO	Diabetes Insipidus, Diffuse Goitre, Gynaecomastia, Hirsutism, Hypoglycaemia, SIADH, Weight Loss
HAEM	Splenomegaly
PAEDS	Floppy infant
MISC	Anaphylaxis, Autoimmune associated diseases, Clubbing, Parotid Swelling, Splinter haemorrhages, Toxic agents and abnormal vitals, Toxicological causes of cardiac arrest
IMAGING	CHEST: Atelectasis, Hilar adenopathy, Hilar enlargement on CXR, Honeycomb lung, Increased interstitial markings, Mediastinal widening on mobile CXR, Pulmonary fibrosis, Pseudoinfiltrates on CXR, Pulmonary opacities on CXR, ABDO: Gas on abdominal X-ray, Kidney mass, BRAIN: Intracranial calcification, Intracranial structures with contrast, Ventriculomegaly, OTHER: Pseudofracture on X-Ray,
LABS	LOW: Anaemia, Hypocalcaemia, hypochloraemia, Hypomagnesaemia,  HIGH: Bilirubin and Jaundice, Hyperammonaemia, Hypercalcaemia, Hyperchloraemia, Hyperkalaemia, Hypermagnesaemia,  ACID BASE: Acid base disorders, Resp. acidosis, Resp. alkalosis, Creatinine, CRP, Dipstick Urinalysis, Laboratory Urinalysis, Liver function tests (LFTs), Pleural fluid analysis, Urea, Urea Creatinine Ratio, Uric acid, Urinalysis, Urine Electrolytes

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