What causes tachycardia in pregnancy?

Causes of Tachycardia in Pregnancy

Tachycardia in pregnancy commonly occurs due to normal physiological changes, but can also result from pathological conditions that require prompt intervention to prevent maternal and fetal morbidity and mortality. 1

Physiological Causes

• Hemodynamic Changes

  • Increased cardiac output (30-50% increase)
  • Increased heart rate (10-20 beats per minute)
  • Decreased systemic vascular resistance
  • Expanded blood volume (40-50% increase)

• Hormonal Influences

  • Direct cardiac electrophysiological effects of estrogen and progesterone
  • Altered autonomic tone with increased sympathetic activity 2

• Other Normal Pregnancy Factors

  • Emotional stress/anxiety
  • Physical exertion
  • Positional changes (especially supine position causing inferior vena cava compression) 3

Pathological Causes

Pregnancy-Specific Conditions

• Anemia - Significantly associated with sinus tachycardia 3
• Pre-eclampsia - Systemic endothelial disorder with vasospasm and reduced organ perfusion 1
• Peripartum Cardiomyopathy - Should be ruled out in women presenting with new-onset ventricular tachycardia during the last 6 weeks of pregnancy or early postpartum 1, 4

Cardiac Arrhythmias

• Supraventricular Tachycardias (SVTs)

  • Atrioventricular nodal re-entry tachycardia
  • Atrioventricular re-entry tachycardia
  • Focal atrial tachycardia
  • Atrial flutter and atrial fibrillation (rare unless structural heart disease or hyperthyroidism present) 1

• Ventricular Arrhythmias

  • Ventricular tachycardia (less common but potentially life-threatening)
  • Idiopathic right ventricular outflow tract tachycardia 1

Other Medical Conditions

• Hyperthyroidism - Can precipitate atrial fibrillation or flutter 1
• Pulmonary Embolism - Presents with tachycardia and dyspnea
• Infection/Sepsis - Systemic inflammatory response causing tachycardia
• Dehydration - Fluid depletion can trigger SVT 5
• Structural Heart Disease - Congenital heart disease, valvular heart disease, or cardiomyopathy 2

Risk Factors for Arrhythmias in Pregnancy

• Gestational Age - Most heart rhythm disturbances occur in the second trimester 3
• Multiparity - Risk increases with number of pregnancies 3
• Pre-existing Cardiac Conditions - Congenital heart disease, valvular disease, cardiomyopathy 2
• Labor and Delivery - Higher risk of arrhythmias during this period due to pain, anxiety, and hemodynamic fluctuations 2

Diagnostic Approach

When evaluating tachycardia in pregnancy:

1. Distinguish between sinus tachycardia and arrhythmias
2. Assess for hemodynamic stability
3. Look for signs of underlying conditions (anemia, thyroid disease, structural heart disease)
4. Perform ECG monitoring to identify specific arrhythmias
5. Consider echocardiography if structural heart disease is suspected

Clinical Pearls and Pitfalls

• Persistent tachycardia regardless of symptoms should always prompt clinical review and investigation 6
• Ectopic beats (both supraventricular and ventricular) become more frequent during pregnancy and may develop for the first time 1
• Fluid status assessment is important as dehydration can trigger arrhythmias in pregnancy 5
• Arrhythmias during pregnancy require a multidisciplinary approach involving cardiology, obstetrics, anesthesiology, and neonatology 7

Remember that while many cases of tachycardia in pregnancy are benign, identifying and treating pathological causes is essential for preventing adverse maternal and fetal outcomes.