What is the management for a 28-week pregnant woman presenting with tachycardia and shortness of breath?

Management of Tachycardia and Shortness of Breath at 28 Weeks Gestation

Immediate cardioversion is indicated if this patient demonstrates hemodynamic instability (hypotension, altered mental status, severe dyspnea), while stable patients should undergo urgent cardiac evaluation with ECG, continuous monitoring, and echocardiography to identify the arrhythmia type and guide treatment. 1, 2

Immediate Assessment and Stabilization

Determine Hemodynamic Stability

• 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—maternal stability is essential for fetal survival and cardioversion should never be delayed due to pregnancy concerns. 1, 3
• If hemodynamically stable: Proceed with diagnostic workup while maintaining continuous cardiac and fetal monitoring. 2, 4

Critical Differential Diagnoses to Rule Out Immediately

• Peripartum cardiomyopathy: Can present with new-onset ventricular tachycardia during the last 6 weeks of pregnancy or postpartum, though this patient at 28 weeks is earlier than typical presentation. 3
• Thyroid storm: Can precipitate atrial fibrillation or flutter and presents with tachycardia, diaphoresis, and dyspnea—check thyroid function tests urgently. 2, 3
• Pulmonary embolism: Pregnant patients can develop hypoxemia rapidly due to decreased functional residual capacity and increased oxygen demand. 2
• Tachycardia-induced cardiomyopathy: Persistent unexplained sinus tachycardia in pregnancy may mask underlying focal atrial tachycardia and can rapidly deteriorate into cardiomyopathy. 5

Essential Diagnostic Workup

Cardiac Evaluation

• 12-lead ECG immediately: Look for pre-excitation patterns (delta waves), QRS width and morphology, and fusion beats to differentiate supraventricular from ventricular tachycardia. 2, 4
• Continuous cardiac monitoring: Document the arrhythmia type, onset/termination pattern (abrupt suggests paroxysmal SVT, gradual suggests sinus tachycardia), and heart rate during episodes. 2, 4
• Echocardiogram urgently: Rule out structural heart disease, assess left ventricular function (ejection fraction), and evaluate for peripartum cardiomyopathy—particularly critical if arrhythmias are documented. 2, 4
• Holter monitor if symptoms are intermittent: To capture arrhythmia episodes if not present during initial evaluation. 4

Obstetric Evaluation

• Continuous fetal monitoring: Assess fetal heart rate and well-being, as maternal arrhythmias can cause fetal hypoperfusion. 3
• Assess for preterm labor: Given the gestational age and potential for uterine contractions. 4

Treatment Algorithm Based on Arrhythmia Type

For Supraventricular Tachycardia (Most Common in Pregnancy, 20-44% Incidence)

Acute conversion in stable patients:

1. First-line: Vagal maneuvers (Valsalva, carotid massage). 1, 2
2. Second-line: IV adenosine if vagal maneuvers fail (safe and effective in pregnancy). 1, 2, 4
3. Third-line: IV metoprolol or propranolol if adenosine fails. 1, 4, 3
4. Alternative: IV verapamil may be considered, though less preferred than beta-blockers. 1

Long-term prophylaxis for recurrent SVT:

• First-line: Oral metoprolol or propranolol (cardioselective beta-blockers are safe after first trimester). 1, 3
• Second-line: Oral sotalol or flecainide if beta-blockers fail. 1, 3
• Avoid atenolol: Should not be used for any arrhythmia in pregnancy. 1

For Ventricular Tachycardia (Rare Unless Structural Heart Disease Present)

• If unstable: Immediate electrical cardioversion. 1, 3
• If stable and monomorphic: IV sotalol or procainamide. 1
• Consider verapamil-sensitive idiopathic left ventricular tachycardia: Look for fusion beats with right bundle branch pattern on ECG—this responds specifically to verapamil. 6

For Atrial Fibrillation/Flutter

• Rate control: Digoxin or beta-blockers. 1, 3
• Anticoagulation: Therapeutic HBPM or vitamin K antagonists depending on gestational age. 3
• Cardioversion: Generally not recommended for focal atrial tachycardia due to high recurrence, but appropriate for atrial fibrillation if indicated. 3

Critical Pitfalls to Avoid

• Never use AV nodal blockers (adenosine, beta-blockers, calcium channel blockers) if manifest pre-excitation is present on ECG: This can precipitate ventricular fibrillation. 3
• Do not delay cardioversion in unstable patients due to pregnancy concerns: Cardioversion is safe at any gestational age and maternal stability is paramount. 1, 3
• Monitor drug levels carefully: Pharmacokinetics are altered during pregnancy, requiring more frequent monitoring. 3
• Avoid amiodarone unless all other therapies have failed: Use only at the lowest effective dose due to fetotoxic effects including thyroid dysfunction. 3
• Do not assume benign sinus tachycardia: Persistent unexplained tachycardia may mask focal atrial tachycardia with risk of rapid deterioration to cardiomyopathy. 5

When to Escalate Care

Immediate emergency department referral if:

• Recurrent episodes of tachycardia with dizziness or dyspnea. 4
• Syncope or near-syncope with palpitations (suggests serious arrhythmia). 2, 4
• Signs of hemodynamic instability (hypotension, altered mental status). 2, 3
• Oxygen saturation <92% on room air. 2
• Evidence of heart failure on echocardiogram (reduced ejection fraction). 4, 5

Special Pregnancy Considerations

• Left lateral decubitus positioning: For symptomatic bradycardia or hypotension to relieve inferior vena cava compression. 1
• Avoid grapefruit juice: If calcium channel blockers are used, as it significantly increases drug levels. 7
• Multidisciplinary team approach: Cardiology, maternal-fetal medicine, and anesthesiology should coordinate care, especially if delivery is considered as therapeutic option. 5, 8
• Catheter ablation: Can be performed with zero-fluoroscopy technique in selected refractory cases during pregnancy. 3, 8