In an otherwise healthy woman within the first six weeks postpartum presenting with tachycardia, what is the initial assessment and management approach?

Tachycardia Management in Post-Pregnancy

Immediate Assessment and Stabilization

In a healthy postpartum woman presenting with tachycardia within six weeks of delivery, immediately assess hemodynamic stability and perform electrical cardioversion without delay if the patient shows any signs of instability, as maternal stabilization is critical and cardioversion is not contraindicated in the postpartum period. 1, 2

Hemodynamic Assessment

• Perform immediate electrical cardioversion using biphasic shock energy of 120-200 J with the lateral defibrillator pad placed under the breast tissue if the patient demonstrates hypotension, altered mental status, severe dyspnea, or chest pain. 1, 2
• Position the patient in left lateral decubitus if symptomatic bradycardia or hypotension occurs, as this relieves inferior vena cava compression that can persist in the early postpartum period. 1, 2

Critical Diagnostic Workup

• Obtain a 12-lead ECG immediately to differentiate narrow complex supraventricular tachycardia from wide complex tachycardia and identify pre-excitation patterns. 2, 3
• Perform echocardiography urgently to rule out peripartum cardiomyopathy, which can present with new-onset ventricular tachycardia during the last 6 weeks of pregnancy or up to 5 months postpartum. 2, 4
• Check thyroid function tests, as thyroid storm can precipitate atrial fibrillation or flutter with associated tachycardia in the postpartum period. 2
• Assess for signs of postpartum hemorrhage, sepsis, venous thromboembolism, and anemia—all common causes of postpartum tachycardia that require specific management. 4

Management Algorithm for Stable Supraventricular Tachycardia

First-Line Interventions

• Attempt vagal maneuvers first (Valsalva, carotid massage, or ice-cold wet towel to face) for stable narrow complex tachycardia. 1, 2, 5
• If vagal maneuvers fail, administer IV adenosine 6 mg rapid push, followed by up to two 12 mg doses if ineffective, as adenosine has a short half-life and extensive safety data. 1, 2, 5

Second-Line Pharmacologic Options

• If adenosine fails to convert the rhythm, administer IV metoprolol or propranolol as a slow infusion to minimize hypotension. 1, 2, 5
• IV verapamil may be considered if adenosine and beta-blockers fail, though it carries higher risk of maternal hypotension than adenosine. 1, 2

Long-Term Prophylaxis

• For recurrent supraventricular tachycardia requiring chronic suppression, prescribe oral metoprolol or propranolol as first-line therapy, as cardioselective beta-blockers have extensive safety data. 1, 2, 5
• If digoxin or beta-blockers fail, consider oral sotalol or flecainide as second-line agents. 1, 5
• Never use atenolol for any arrhythmia in postpartum women due to potential harmful effects. 1, 2

Management of Ventricular Tachycardia

• Perform immediate electrical cardioversion for any sustained ventricular tachycardia, whether stable or unstable. 1, 2
• For hemodynamically stable monomorphic sustained VT, IV sotalol or procainamide may be considered for acute conversion. 1, 2
• Use IV amiodarone only when the patient is hemodynamically unstable and refractory to electrical cardioversion, as amiodarone should be reserved as a last resort. 2, 5

Critical Pitfalls to Avoid

• Never delay cardioversion in hemodynamically unstable patients due to concerns about breastfeeding or postpartum status—maternal stability is the priority. 1, 2
• Do not use AV nodal blockers (adenosine, beta-blockers, or calcium channel blockers) in patients with manifest pre-excitation on ECG, as this can precipitate ventricular fibrillation. 2
• Do not dismiss tachycardia as "normal postpartum changes" without proper evaluation, as serious conditions like peripartum cardiomyopathy, pulmonary embolism, and sepsis commonly present in this window. 4
• Avoid amiodarone except as a last resort, and if the patient is breastfeeding, counsel regarding temporary cessation during amiodarone therapy. 1, 5

Special Postpartum Considerations

• Monitor drug levels more carefully in the early postpartum period, as pharmacokinetics rapidly change as blood volume and cardiac output return to baseline. 2
• Assess for postpartum-specific causes including obstetric hemorrhage (overt or concealed), endometritis, mastitis, urinary tract infection, and wound infection—all of which can present with compensatory sinus tachycardia. 4
• Consider procalcitonin and D-dimer testing if sepsis or venous thromboembolism are suspected, though interpret with caution as reference ranges differ in the immediate postpartum period. 4