What is the recommended treatment for a 28-week pregnant woman experiencing tachycardia and diaphoresis?

Management of Tachycardia and Diaphoresis at 28 Weeks Gestation

For a pregnant woman at 28 weeks with tachycardia and diaphoresis, begin with vagal maneuvers, followed by intravenous adenosine if vagal maneuvers fail, then intravenous metoprolol if adenosine is ineffective, while immediately performing electrical cardioversion if hemodynamic instability develops at any point. 1, 2

Immediate Assessment and Stabilization

Determine Hemodynamic Stability

• If hemodynamically unstable (hypotension, altered mental status, chest pain, severe dyspnea): perform immediate electrical cardioversion 3, 1
• Electrical cardioversion is safe during pregnancy and should not be delayed when indicated 4, 5

If Hemodynamically Stable: Stepwise Treatment Algorithm

Follow this exact sequence: 1, 2

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

2. Second-line: Intravenous adenosine if vagal maneuvers fail 1, 2

   • Adenosine is the drug of choice for acute termination of supraventricular tachycardia in pregnancy 4, 5
   • Terminates approximately 30% of atrial tachycardias 3, 1

3. Third-line: Intravenous metoprolol if adenosine fails 1, 2

   • Cardioselective beta-blockers are first-line for rate control 3, 2

Diagnostic Workup

Essential Cardiac Evaluation

• 12-lead ECG to identify the specific arrhythmia type and evaluate for pre-excitation or structural abnormalities 2
• Holter monitor if symptoms persist or recur to capture paroxysmal arrhythmias 1, 2
• Echocardiogram to rule out structural heart disease, particularly tachycardia-induced cardiomyopathy 2, 6
  • This is critical: focal atrial tachycardia can cause rapidly deteriorating cardiomyopathy during pregnancy 6

Rule Out Non-Cardiac Causes

• Thyroid function tests to exclude hyperthyroidism, which commonly causes atrial fibrillation/flutter in pregnancy 3
• Electrolytes, particularly potassium (hypokalemia of pregnancy can promote arrhythmias) 5

Long-Term Management Based on Arrhythmia Type

For Supraventricular Tachycardia (Most Common)

• Prophylactic therapy with oral metoprolol (cardioselective beta-blocker) as first-line 3, 2, 5
• If beta-blockers are ineffective: consider sotalol, flecainide, or propafenone 3, 1
• Do not use AV nodal blocking agents if pre-excitation is present on ECG 1

For Focal Atrial Tachycardia

• Rate control with beta-blockers and/or digoxin to prevent tachycardia-induced cardiomyopathy 3, 1
• For symptomatic cases: flecainide, propafenone, or sotalol 3, 1
• Catheter ablation should be considered for drug-resistant cases causing hemodynamic compromise 3, 1

For Atrial Fibrillation/Flutter (Rare Without Structural Disease)

• Therapeutic anticoagulation with LMWH is mandatory 3, 1
• Electrical cardioversion if hemodynamically unstable 3
• For stable patients: consider IV ibutilide or flecainide for pharmacological conversion 3

For Ventricular Tachycardia

• Idiopathic right ventricular outflow tract VT: verapamil or beta-blockers 3
• For hemodynamically stable monomorphic VT: IV sotalol or procainamide 3
• For unstable or refractory VT: IV amiodarone (despite fetotoxicity, use when other options fail) 3, 1

Critical Safety Considerations

Drug Selection Hierarchy

• Safest options: Adenosine, digoxin, metoprolol, propranolol 4, 5
• Second-line: Sotalol, flecainide, propafenone, verapamil 3, 4
• Use only when other therapies fail: Amiodarone (fetotoxic effects including thyroid dysfunction and growth restriction) 3, 1

Important Pitfalls to Avoid

• Do not dismiss persistent sinus tachycardia - it may mask underlying focal atrial tachycardia and lead to rapidly deteriorating cardiomyopathy 6
• Avoid beta-blockers in first trimester if possible (risk of intrauterine growth restriction) 4
• Eliminate stimulants: caffeine, smoking, alcohol 4, 5

When to Escalate Care

Immediate emergency department referral if: 2

• Recurrent episodes of tachycardia with diaphoresis
• Development of syncope, near-syncope, or chest pain
• Shortness of breath or signs of heart failure
• Any hemodynamic instability

Red Flags Requiring Urgent Evaluation

• Persistent unexplained tachycardia despite treatment (consider tachycardia-induced cardiomyopathy) 6
• Personal or family history of sudden cardiac death (requires close surveillance for inherited arrhythmogenic disorders) 3, 1
• New-onset arrhythmia in last 6 weeks of pregnancy (rule out peripartum cardiomyopathy) 3