How to approach a patient with maternal tachycardia?

Approach to Maternal Tachycardia

Immediate Hemodynamic Assessment

If the patient is hemodynamically unstable (hypotension, altered mental status, chest pain, severe dyspnea), perform immediate electrical cardioversion at 120-200 J biphasic energy with the lateral pad placed under the breast tissue—do not delay for pregnancy concerns as maternal stability is essential for fetal survival. 1, 2

For stable patients, proceed with systematic evaluation and treatment as outlined below. 1, 2

Critical Red Flags Requiring Immediate Action

• Hemodynamic instability (hypotension, altered mental status, chest pain) mandates immediate cardioversion 1, 2
• Sustained tachycardia with heart rate persistently >150 bpm can cause maternal and fetal hypoperfusion 2
• New-onset ventricular tachycardia in the last 6 weeks of pregnancy or postpartum suggests peripartum cardiomyopathy until proven otherwise 1, 3
• Syncope or near-syncope with tachycardia requires emergency evaluation 3, 2
• Signs of thyroid storm (tachycardia with diaphoresis, fever, agitation) precipitating atrial fibrillation 1
• Manifest pre-excitation on ECG (WPW pattern)—never use AV nodal blockers as this can precipitate ventricular fibrillation 1, 2

Essential Differential Diagnoses

Life-Threatening Causes

• Peripartum cardiomyopathy presenting with ventricular tachycardia in late pregnancy or postpartum 1, 3
• Pulmonary embolism causing sinus tachycardia with hypoxia 4
• Obstetric hemorrhage with compensatory tachycardia 4
• Sepsis from chorioamnionitis, endometritis, or other sources 4
• Thyroid storm precipitating atrial fibrillation or flutter 1, 2

Common Arrhythmias

• Supraventricular tachycardia (SVT) occurs in 20-44% of pregnancies and is the most common arrhythmia 3, 2
• Atrial fibrillation/flutter especially in patients with structural heart disease or hyperthyroidism 1, 2
• Focal atrial tachycardia which can terminate with adenosine in 30% of cases 1
• Ventricular tachycardia rare unless structural heart disease or inherited channelopathies present 1

Diagnostic Workup for Stable Patients

Immediate Bedside Assessment

• 12-lead ECG to document rhythm, identify tachycardia type, and evaluate for pre-excitation patterns 2
• Continuous fetal monitoring to assess fetal heart rate and detect hypoperfusion 1
• Vital signs including oxygen saturation and blood pressure 4

Essential Laboratory Tests

• Thyroid function tests as hyperthyroidism occurs in 10-25% of atrial fibrillation cases 2
• Complete blood count to evaluate for anemia or infection 4
• Electrolytes including potassium and magnesium 4

Cardiac Imaging

• Echocardiogram is mandatory in any pregnant patient with documented arrhythmia to rule out structural heart disease 1, 3, 2
• Holter monitor if symptoms are intermittent to capture arrhythmia episodes 1, 3

Treatment Algorithm for Stable SVT

Step 1: Vagal Maneuvers

• Attempt vagal maneuvers first: Valsalva (bearing down for 10-30 seconds at 30-40 mmHg), carotid massage after confirming no bruit, or ice-cold wet towel to face 5, 1, 2

Step 2: IV Adenosine

• If vagal maneuvers fail, give IV adenosine 6 mg rapid push, followed by up to two 12 mg doses if ineffective 5, 1, 2
• Adenosine is safe in pregnancy with short half-life preventing fetal exposure; maternal side effects (chest discomfort, flushing) are transient 5
• Never use adenosine if pre-excitation is present on ECG 1, 2

Step 3: IV Beta-Blocker

• If adenosine fails, give IV metoprolol or propranolol as slow infusion to minimize hypotension 5, 1, 2
• Beta-blockers have extensive safety data over decades in pregnancy 5
• Avoid atenolol which is associated with fetal growth restriction 1

Step 4: IV Verapamil (Alternative)

• IV verapamil may be used if adenosine and beta-blockers fail or are contraindicated, but carries higher risk of maternal hypotension than adenosine 5

Long-Term Prophylaxis for Recurrent SVT

• Cardioselective beta-blockers (metoprolol or propranolol) are first-line for preventing recurrent episodes after the first trimester 1, 2
• Digoxin is an alternative first-line option for rate control, particularly in focal atrial tachycardia to prevent tachycardia-induced cardiomyopathy 1
• Second-line agents include sotalol, flecainida, or propafenone if first-line therapy fails 1

Special Management Considerations

Atrial Fibrillation/Flutter

• Therapeutic anticoagulation with low-molecular-weight heparin is mandatory starting at 24 weeks gestation 1, 2
• Avoid warfarin in first trimester due to teratogenicity 2
• Rate control with beta-blockers or digoxin is essential 1
• Electrical cardioversion is generally not recommended for focal atrial tachycardia due to high recurrence rates 1

Peripartum Cardiomyopathy

• Rule out in any pregnant woman with new-onset arrhythmias, especially ventricular tachycardia in the last 6 weeks of pregnancy or postpartum 1, 3
• Requires echocardiogram and specialized cardiology management 3, 2

Labor and Delivery

• Continuous cardiac monitoring during labor and delivery as arrhythmia risk increases 6
• Left lateral decubitus positioning for symptomatic bradycardia or hypotension to relieve IVC compression 1

Medications to Avoid or Use with Extreme Caution

• Amiodarone should only be used when all other therapies have failed and at the lowest effective dose due to significant fetotoxic effects (thyroid dysfunction, growth restriction) 1, 2
• Atenolol is contraindicated throughout pregnancy 1
• AV nodal blockers (adenosine, beta-blockers, calcium channel blockers) are absolutely contraindicated in patients with manifest pre-excitation on ECG 1, 2

Critical Pitfalls to Avoid

• Never delay cardioversion in unstable patients due to pregnancy concerns—maternal death means fetal death 1, 2
• Never use AV nodal blockers if WPW pattern is present on ECG as this can precipitate ventricular fibrillation 1, 2
• Do not assume all tachycardia is benign—15% of patients with congenital heart disease develop arrhythmias requiring treatment during pregnancy 1
• Monitor drug levels more carefully during pregnancy as pharmacokinetics are altered by increased volume of distribution and renal clearance 1
• Digoxin requirements may increase during pregnancy and decrease postpartum—monitor levels accordingly 6

When to Escalate Care

• Recurrent episodes despite initial management 3, 2
• Development of syncope or near-syncope 3, 2
• Sustained tachycardia causing maternal or fetal compromise 2
• Drug-refractory cases requiring consideration of catheter ablation 1
• Any signs of peripartum cardiomyopathy 1, 3