In a pregnant patient presenting to the emergency department with palpitations and sinus tachycardia on electrocardiogram, what further assessment and management are indicated?

Evaluation and Management of Sinus Tachycardia in Pregnant Patients

Immediate Assessment

In a pregnant patient with palpitations and documented sinus tachycardia on ECG, you must first assess hemodynamic stability and then systematically evaluate for underlying causes before considering this a primary arrhythmia. 1

Hemodynamic Stability Assessment

• If the patient is hemodynamically unstable (hypotensive, altered mental status, chest pain, severe dyspnea, signs of shock), perform immediate electrical cardioversion using biphasic shock energy of 120-200 J with the lateral defibrillator pad placed under the breast tissue, as maternal stability is essential for fetal survival. 1, 2

• If the patient is hemodynamically stable, proceed with systematic evaluation of secondary causes before considering primary sinus node dysfunction. 1

Essential Diagnostic Workup

Rule Out Secondary Causes (Most Critical Step)

Sinus tachycardia in pregnancy is almost always secondary to an underlying condition that requires treatment. 3, 4 You must systematically exclude:

• Hypovolemia/Dehydration: Check orthostatic vital signs, assess mucous membranes, review fluid intake, and consider IV fluid challenge if clinically indicated. 5

• Anemia: Order complete blood count, as anemia is one of the most frequent causes of sinus tachycardia in pregnancy. 5

• Infection/Fever: Check temperature, white blood cell count, urinalysis (UTI is common in pregnancy), and consider other sources if febrile. 5

• Pulmonary Embolism: Assess for risk factors (immobility, prior DVT, thrombophilia), check oxygen saturation, and consider D-dimer with clinical probability assessment, as PE is a leading cause of maternal mortality. 5

• Thyroid Storm/Hyperthyroidism: Order TSH and free T4, as thyroid disorders can precipitate tachycardia and present with diaphoresis and dyspnea. 2, 6

• Peripartum Cardiomyopathy: This must be ruled out in any pregnant woman presenting with new-onset tachycardia, particularly during the last 6 weeks of pregnancy or postpartum, as it can present with ventricular or supraventricular tachycardia. 2, 6

Cardiac Evaluation

• Obtain a 12-lead ECG to confirm sinus rhythm, measure QTc interval, and look for any pre-excitation patterns or other conduction abnormalities. 2, 6

• Perform echocardiography to rule out structural heart disease, assess ventricular function, and evaluate for peripartum cardiomyopathy, especially if arrhythmias are documented or symptoms persist. 1, 2

• Consider Holter monitoring if symptoms are recurrent or if you suspect paroxysmal arrhythmias rather than persistent sinus tachycardia. 1

Fetal Assessment

• Initiate continuous fetal monitoring to assess fetal heart rate and well-being, as maternal tachycardia can cause fetal hypoperfusion, particularly if sustained. 5, 2, 6

Management Algorithm

If Secondary Cause Identified

• Treat the underlying condition (rehydrate for hypovolemia, transfuse for severe anemia, antibiotics for infection, anticoagulation for PE, etc.) as this will resolve the tachycardia. 5

• Reassess heart rate after treating the underlying cause before considering any antiarrhythmic therapy. 5

If No Secondary Cause Found (True Inappropriate Sinus Tachycardia)

This is a diagnosis of exclusion and relatively uncommon. 3, 4, 7

• For symptomatic patients with persistent inappropriate sinus tachycardia, cardioselective beta-blockers (metoprolol 50-100 mg twice daily or propranolol 80-160 mg daily in long-acting form) are first-line therapy after the first trimester. 1, 2

• Avoid atenolol as it is associated with fetal growth restriction. 2

• If beta-blockers are ineffective or contraindicated, consider digoxin, sotalol, or flecainida as second-line agents. 1, 2

• Ivabradine is mentioned in non-pregnancy literature for IST but lacks safety data in pregnancy and should be avoided. 3

Critical Pitfalls to Avoid

• Do not diagnose inappropriate sinus tachycardia without thoroughly excluding all secondary causes, as this is almost always a diagnosis of exclusion and secondary causes are far more common in pregnancy. 3, 4

• Do not delay cardioversion in hemodynamically unstable patients due to concerns about pregnancy—maternal stability is essential for fetal survival. 1, 2

• Do not use AV nodal blocking agents if pre-excitation is present on ECG, as this can precipitate ventricular fibrillation. 1, 2

• Do not assume benign sinus tachycardia without ruling out peripartum cardiomyopathy, especially in late pregnancy or postpartum. 2, 6

Disposition and Follow-Up

• Admit for observation if secondary causes remain unclear, if symptoms are severe, or if fetal monitoring shows concerning patterns. 1

• Discharge with close outpatient follow-up if a benign secondary cause is identified and treated, symptoms resolve, and fetal monitoring is reassuring. 1

• Provide clear return precautions: recurrent palpitations, syncope, chest pain, shortness of breath, or decreased fetal movement should prompt immediate return to the ED. 2