Tachycardia DDx

Overview

• Tachycardia refers to heart rate >100/min in an adult.
• Tachycardias are classified as regular or irregular, narrow complex or wide complex
• The underlying causes of tachycardia are legion

Types of tachycardia

Narrow complex tachycardias

• Regular
  • Sinus tachycardia
  • Atrial tachycardia
  • Atrial flutter
  • Supraventricular tachycardia
  • AVNRT
  • Orthodromic AVRT
  • Narrow complex VT (fascicular tachycardia)
• Irregular
  • Tachycardia with PACs, PJCs, PVCs
  • Atrial fibrillation
  • Atrial flutter with variable block
  • Atrial tachycardia with variable block
  • Multifocal atrial tachycardia
  • Paroxysmal atrial tachycardia
  • Digoxin toxicity

Wide complex tachycardias

• Regular
  • Monomorphic VT
  • Ventricular flutter
  • Antidromic AVRT
  • Pacemaker tachycardia
  • Accelerated idioventricular rhythm (AIVR)
  • Sodium channel blocker toxicity (e.g. tricyclic antidepressants, cocaine)
  • Hyperkalemia
  • Post-electrical cardioversion
  • Ischaemia
  • Regular tachycardia with aberrancy, bundle branch block or pre-excitation syndromes
• Irregular
  • Polymorphic VT (torsades de pointes)
  • Irregular VT
  • Ventricular fibrillation
  • Irregular tachycardia with aberrancy, bundle branch block or pre-excitation syndromes
  • Atrial fibrillation or flutter with pre-excitation syndromes

Underlying Causes of Tachycardia

Cardiac dysrhythmia

Non-cardiac causes

• Anemia
• Anxiety
• Dehydration
• Electrolyte imbalance (especially hypokalemia and hypomagnesemia)
• Fever/ sepsis
• Hyperthyroidism
• Hypoglycemia
• Ischemia
• Metabolic disorders
• Pain
• Poisoning and toxic exposure
• Pulmonary embolism
• Respiratory disease (e.g. pneumonia, pneumothroax)
• Shock
• Trauma
• Withdrawal syndromes

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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