What are the causes of tachycardia?

Causes of Tachycardia

Tachycardia (heart rate >100 bpm) is caused by a wide range of physiological, pathological, and pharmacological factors, with the most common pathological causes including pyrexia, hypovolemia, anemia, and infections. 1

Classification of Tachycardias

Tachycardias can be broadly classified into:

1. Sinus Tachycardia

• Physiological causes:

  • Physical exertion
  • Emotional stress and anxiety
  • Pain
  • Pregnancy

• Pathological causes: 1

  • Fever/pyrexia
  • Hypovolemia
  • Anemia
  • Infections
  • Hypoxia
  • Acidosis
  • Thyroid disorders (hyperthyroidism)
  • Heart failure

• Pharmacological causes: 1

  • Stimulants (caffeine, alcohol, nicotine)
  • Prescribed medications (salbutamol, aminophylline, atropine, catecholamines)
  • Recreational/illicit drugs (amphetamines, cocaine, ecstasy, cannabis)
  • Anticancer treatments (particularly anthracyclines like doxorubicin and daunorubicin)

2. Supraventricular Tachycardias (SVTs)

• Atrioventricular nodal reentrant tachycardia (AVNRT) 2, 3
• Atrioventricular reentrant tachycardia (AVRT) including Wolff-Parkinson-White syndrome 2, 3
• Atrial tachycardia 3
• Atrial flutter
• Atrial fibrillation
• Sinus node reentrant tachycardia 1
• Postural orthostatic tachycardia syndrome (POTS) 1

3. Ventricular Tachycardias (VTs)

• Structural heart disease: 4

  • Coronary artery disease/myocardial infarction
  • Dilated cardiomyopathy
  • Hypertrophic cardiomyopathy
  • Arrhythmogenic right ventricular cardiomyopathy (ARVC)
  • Valvular heart disease
  • Congenital heart disease

• Primary electrical disorders: 4

  • Long QT syndrome
  • Short QT syndrome
  • Brugada syndrome
  • Catecholaminergic polymorphic ventricular tachycardia

• Other causes:

  • Electrolyte abnormalities (hypokalemia, hypomagnesemia)
  • Drug toxicity (particularly digitalis) 1
  • Idiopathic VT (no detectable cause) 4

Clinical Presentation

Tachycardias often present with: 2, 5

• Palpitations (including pulsation in the neck)
• Chest pain
• Lightheadedness or dizziness
• Dyspnea (shortness of breath)
• Diaphoresis (sweating)
• Syncope (fainting)
• In severe cases, sudden cardiac death 5

Complications

Persistent tachycardia can lead to:

• Tachycardia-induced cardiomyopathy 6
• Heart failure 6
• Neurological complications 5
• Hemodynamic instability 7

Diagnostic Approach

The American College of Cardiology and American Heart Association recommend: 7

• 12-lead ECG assessment (essential for diagnosing the specific type of tachycardia)
• Laboratory evaluation including:
  • Complete blood count (to identify anemia)
  • Basic metabolic panel (for electrolyte abnormalities)
  • Thyroid function tests
  • Toxicology screen when appropriate

Management Considerations

The approach to management depends on:

1. Hemodynamic stability of the patient 7
2. Type of tachycardia
3. Underlying cause

For hemodynamically unstable patients, immediate synchronized cardioversion is recommended 7.

For stable patients with SVT, vagal maneuvers followed by adenosine are first-line treatments 7, 3.

Long-term management may include:

• Treatment of underlying causes
• Beta-blockers or calcium channel blockers 7, 3
• Antiarrhythmic medications
• Catheter ablation for recurrent episodes 7, 3

Important Caveats

• Tachycardia is often misdiagnosed as anxiety or panic disorder, leading to delayed diagnosis 2
• Verapamil should never be used in wide-complex tachycardia due to risk of hemodynamic deterioration 7
• In patients with Wolff-Parkinson-White Syndrome and atrial fibrillation, verapamil, diltiazem, and adenosine should be avoided 7
• Tachycardia-induced heart failure is potentially reversible with appropriate treatment of the underlying arrhythmia 6