What is the management for sudden onset tachycardia at rest in a patient at 28 weeks gestation?

Management of Sudden Onset Tachycardia at Rest in a 28-Week Pregnant Patient

For sudden onset tachycardia at rest at 28 weeks gestation, immediately assess hemodynamic stability: if unstable, perform immediate electrical cardioversion; if stable, attempt vagal maneuvers first, followed by IV adenosine 6 mg rapid push if vagal maneuvers fail, then IV metoprolol if adenosine is ineffective. 1, 2

Immediate Assessment and Stabilization

Determine hemodynamic stability immediately by assessing blood pressure, mental status, chest pain, dyspnea, and signs of shock. 1, 2

If Hemodynamically Unstable:

• Perform immediate electrical cardioversion using biphasic shock energy of 120-200 J with the lateral defibrillator pad placed under the breast tissue. 2
• Do not delay cardioversion due to pregnancy concerns—maternal stability is essential for fetal survival. 2
• Cardioversion is safe in all phases of pregnancy and should be used for any sustained tachycardia causing hemodynamic compromise. 1

If Hemodynamically Stable:

Follow this stepwise algorithm for supraventricular tachycardia (the most common arrhythmia in pregnancy): 1, 3

1. First-line: Vagal maneuvers (Valsalva, carotid massage, ice water immersion) to terminate the tachycardia. 1, 2

2. Second-line: IV adenosine 6 mg rapid push if vagal maneuvers fail—this is the first-choice drug and is safe in pregnancy. 1, 2, 4

3. Third-line: IV metoprolol if adenosine fails to terminate the tachycardia. 1, 2

Essential Diagnostic Workup

Obtain a 12-lead ECG during tachycardia to identify the arrhythmia type and look for pre-excitation patterns (delta waves), as AV nodal blockers are contraindicated in manifest pre-excitation. 1, 2

Perform continuous fetal monitoring to assess fetal heart rate and well-being, as maternal arrhythmias can cause fetal hypoperfusion, particularly with sustained tachycardia or atrial flutter. 1, 2

Order an echocardiogram to rule out structural heart disease, especially if arrhythmias are documented, as 15% of patients with congenital heart disease develop arrhythmias requiring treatment during pregnancy. 1, 5

Consider Holter monitoring if symptoms persist or recur to capture paroxysmal arrhythmias. 2, 5

Critical Differential Diagnoses to Exclude

Rule out peripartum cardiomyopathy (PPCM), which can present with new-onset ventricular tachycardia during the last 6 weeks of pregnancy or early postpartum period. 1, 2

Assess thyroid function to exclude thyroid storm, which can precipitate atrial fibrillation or flutter and presents with tachycardia, diaphoresis, and dyspnea. 2

Evaluate for inherited arrhythmogenic disorders by obtaining family history of sudden death, cardiomyopathy, or long QT syndrome, as these require close surveillance. 1, 5

Long-Term Prophylactic Management

If recurrent symptomatic episodes occur or tachycardia causes hemodynamic compromise, initiate prophylactic antiarrhythmic therapy: 1, 2

• First-line: Cardioselective beta-blockers (metoprolol or propranolol)—safe after the first trimester and effective for preventing recurrent SVT. 1, 2, 5

• Avoid atenolol due to fetal growth restriction risk. 2

• Second-line: Sotalol, flecainide, or propafenone if beta-blockers are ineffective or contraindicated. 1, 2

• Use amiodarone only as last resort when all other therapies have failed, at the lowest effective dose, due to fetotoxic effects including thyroid dysfunction and neurodevelopmental concerns. 1, 5

Special Considerations for Specific Arrhythmias

Atrial Flutter/Atrial Fibrillation:

• Initiate therapeutic anticoagulation with LMWH or vitamin K antagonists according to stage of pregnancy (LMWH in first and last trimester, warfarin in second trimester acceptable). 1
• Cardioversion requires prior anticoagulation for at least 3 weeks if duration ≥48 hours or unknown, or transoesophageal echocardiography to exclude left atrial thrombus. 1

Focal Atrial Tachycardia:

• Use beta-blockers and/or digoxin for rate control to prevent tachycardia-induced cardiomyopathy. 1, 2
• Approximately 30% may terminate with adenosine. 1, 2
• Consider catheter ablation only in drug-resistant and poorly tolerated cases. 1, 2

Ventricular Tachycardia:

• If stable monomorphic VT, consider IV sotalol or IV procainamide. 1
• For unstable or refractory VT, use IV amiodarone and consider ICD implantation if therapy-resistant. 1

Critical Pitfalls to Avoid

Never use AV nodal blocking agents (adenosine, beta-blockers, calcium channel blockers, digoxin) in patients with manifest pre-excitation on resting ECG, as this can precipitate ventricular fibrillation. 1, 2

Do not use beta-blockers, class I antiarrhythmics, or sotalol with caution if left or right ventricular function is impaired. 1

Monitor drug levels more carefully during pregnancy as pharmacokinetics are altered due to increased plasma volume, renal clearance, and hepatic metabolism. 2

Position patient in left lateral decubitus if symptomatic bradycardia or hypotension develops to relieve inferior vena cava compression. 2

When to Consider Catheter Ablation

Catheter ablation may be necessary for drug-refractory and poorly tolerated tachycardias, but should be postponed to the second trimester if possible and performed at an experienced center with suitable lead shielding and maximal use of zero-fluoroscopy techniques. 1, 3