Tachycardia

Exam Cram

• Tachycardia is defined as a heart rate > 100

• Tachycardias are classified by their arrhythmia, sinus tachycardia being the most common

• Sinus tachycardia is caused by infection, dehydration, pain, anxiety or immune reaction

• Management: DC cardioversion if ongoing ischaemia, hypotension, heart failure or syncope; otherwise as per arrhythmia

Outline

Assessment

History

• Asymptomatic

• Chest pain, syncope, palpitations

Examination

• Heart murmurs

• Oedema: pretibial, pulmonary

Investigations

• ECG

• Baseline- FBC, urea & creatinine,

• Wider causes: calcium, magnesium, phosphate; thyroid function tests

• Consider septic screen: blood & urine cultures, CXR, viral PCR, CRP/ PCT

• Consider cardiac: troponin, d-dimer, ECHO

Diagnosis

Diagnostic criteria: Heart rate > 100

Classification 

1. Aetiology- arrhythmia

• Supraventricular

  • Sinus tachycardia

  • Atrial Fibrillation (AF), 

  • Atrial flutter,

  • SVT

  • WPW (AVnRT)

• Ventricular

  • Ventricular Fibrillation (VF),

  • Ventricular tachycardia (VT)

2. Severity

   • Unstable (1/4 features)

     1. SBP < 90 or diastolic < 60

     2. Ischaemia (ongoing chest pain)

     3. Ongoing (pre)syncope

     4. Acute heart failure- e.g. pulmonary oedema

   • Stable

Management

1. Unstable

   • DC cardioversion

   • Peri-arrest buzzer, HDU/ resus setting, senior support

2. Stable 

   • As per underlying cause (arrhythmia)

Resources and References

Written in 2025