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

Background

• Tachycardia is most commonly caused by sinus tachycardia 

Assessment

History

• Asymptomatic

• Chest pain, syncope, palpitations

Examination

• Heart murmurs

• Oedema: pretibial, pulmonary

Investigations

• ECG

• Baseline- FBC, urea & creatinine,

• Consider calcium, magnesium, phosphate; thyroid function tests

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

• Consider troponin, d-dimer, ECHO

Diagnosis

Diagnostic criteria: Heart rate > 100

Classification 

1. 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

2. Aetiology- arrhythmia

   • Sinus tachycardia- i.e. physiologic response

   • Abnormal arrhythmia

1. Supraventricular

   • Atrial Fibrillation (AF), 

   • Atrial flutter,

   • SVT

   • WPW (AVnRT)

2. Ventricular

   • Ventricular Fibrillation (VF),

   • Ventricular tachycardia (VT)

Management

1. Unstable

   • DC cardioversion

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

2. Stable 

   • Diagnose underlying cause (arrhythmia)

   • Consider cause, e.g. sinus tachycardia- pain, dehydration, constipation, urinary retention, anxiety/ distress, inflammatory response to e.g. sepsis or illness e.g. Pulmonary Embolus 

Resources and References

1. iResus tachycardia UK Guidelines

Scope

• Body system: cardiovascular

• Specialty: cardiology

Written in 2025