What is the management for a 36-week pregnant woman with palpitations, normal Thyroid-Stimulating Hormone (TSH) level, and sinus tachycardia?

Management of Sinus Tachycardia in a 36-Week Pregnant Woman

For a 36-week pregnant woman with palpitations, normal TSH, and sinus tachycardia at 128 bpm, initial management should focus on rate control with a selective beta-blocker such as metoprolol, while simultaneously investigating underlying causes. 1

Initial Assessment and Diagnosis

• Rule out structural heart disease: Echocardiography is essential to assess left ventricular function and rule out structural abnormalities
• Evaluate for other causes:
  • Anemia (complete blood count)
  • Infection/sepsis (complete blood count, C-reactive protein)
  • Pulmonary embolism (D-dimer if clinically suspected)
  • Fluid depletion/dehydration (clinical assessment, electrolytes) 2
  • Thyrotoxicosis (already ruled out with normal TSH)

Management Algorithm

Step 1: Hemodynamic Assessment

• If hemodynamically unstable: Immediate electrical cardioversion 1
• If stable: Proceed with medical management

Step 2: Rate Control (First-Line)

• Selective beta-blocker: Metoprolol is the preferred agent 1
  • Start with low dose and titrate as needed
  • Safe during pregnancy and breastfeeding 3
• Alternative: If beta-blockers are contraindicated, consider digoxin or calcium channel antagonist (diltiazem or verapamil) 1

Step 3: Monitor for Complications

• Tachycardia-induced cardiomyopathy: Although rare in pregnancy, requires urgent attention due to risk of rapid progression 4
• Fetal monitoring: Regular assessment of fetal heart rate and growth

Step 4: Long-Term Management

• Prophylactic antiarrhythmic therapy: Only if symptoms are intolerable or if tachycardia causes hemodynamic compromise 1
• Delivery planning: Establish a multidisciplinary delivery plan with cardiology, obstetrics, and anesthesiology input
• Postpartum monitoring: Continue monitoring for at least 6 months postpartum

Special Considerations

Inappropriate Sinus Tachycardia (IST)

• Consider IST if no other cause is found 4
• IST in pregnancy is associated with high rates of hospitalization and induction of labor 5
• Treatment primarily focuses on symptom management rather than aggressive rate control

Fluid Status

• Assess hydration status as dehydration can contribute to tachycardia in pregnancy 2
• Ensure adequate fluid intake and consider IV fluids if clinically dehydrated

Postpartum Management

• Continue monitoring for arrhythmias in the postpartum period
• Beta-blockers can be safely continued during breastfeeding 3

Common Pitfalls to Avoid

1. Delaying treatment: Persistent tachycardia can lead to cardiomyopathy and should be addressed promptly
2. Overlooking underlying causes: Sinus tachycardia is often secondary to another condition
3. Using inappropriate medications: Avoid amiodarone due to fetotoxic effects 1
4. Inadequate follow-up: Continue monitoring into the postpartum period as some arrhythmias may worsen after delivery

Remember that while palpitations are common in pregnancy, persistent sinus tachycardia at 128 bpm warrants thorough investigation and management to prevent maternal and fetal complications.