What is the best management approach for a pregnant patient experiencing paroxysmal tachycardia?

Management of Paroxysmal Tachycardia in Pregnancy

For hemodynamically unstable paroxysmal tachycardia in pregnancy, perform immediate electrical cardioversion without delay; for stable patients, attempt vagal maneuvers first, followed by IV adenosine 6 mg rapid push if unsuccessful, then IV metoprolol if adenosine fails. 1, 2

Immediate Assessment and Stabilization

Hemodynamic Status Determines Treatment Urgency

• If the patient demonstrates hemodynamic instability (hypotension, altered mental status, chest pain, or signs of shock), perform immediate electrical cardioversion using biphasic shock energy of 120-200 J with the lateral defibrillator pad placed under the breast tissue. 1, 2
• Maternal stability is essential for fetal survival—never delay cardioversion due to pregnancy concerns, as cardioversion is not contraindicated in pregnancy and should be used for any sustained tachycardia causing hemodynamic instability. 1, 2
• Continuous fetal monitoring is essential during any arrhythmia episode, as maternal arrhythmias can cause fetal hypoperfusion. 1

For Hemodynamically Stable Patients

Follow this stepwise algorithm for acute termination of supraventricular tachycardia:

1. First-line: Vagal maneuvers (Valsalva maneuver, carotid massage, or ice-cold wet towel to face). 1, 2

2. Second-line: IV adenosine 6 mg rapid push, followed by up to two 12 mg doses if ineffective—adenosine is safe in pregnancy with a short half-life preventing fetal exposure and can terminate approximately 30% of atrial tachycardias. 1, 3

3. Third-line: IV metoprolol or propranolol as a slow infusion to minimize hypotension if adenosine fails. 1, 2

4. Alternative: IV verapamil may be used if adenosine and beta-blockers fail or are contraindicated, though it carries higher risk of maternal hypotension than adenosine. 1, 2

Long-Term Prophylaxis for Recurrent Episodes

• Cardioselective beta-blockers (metoprolol or propranolol) are first-line for preventing recurrent supraventricular tachycardia, with extensive safety data after the first trimester. 1, 2
• Avoid atenolol for any arrhythmia in pregnancy. 1
• If beta-blockers are ineffective, second-line options include sotalol, flecainide, or propafenone in the absence of structural heart disease. 1, 2
• Drug therapy should begin as late in pregnancy as possible and use the lowest effective dose, though beta-blockers used in the first trimester may cause intrauterine growth retardation. 2, 4

Critical Diagnostic Considerations

Rule Out Structural Heart Disease and High-Risk Conditions

• Obtain a 12-lead ECG immediately to confirm narrow complex tachycardia and evaluate for pre-excitation patterns or conduction abnormalities. 1, 5
• Perform echocardiography to rule out structural heart disease, particularly peripartum cardiomyopathy, which can present with new-onset ventricular tachycardia during the last 6 weeks of pregnancy or postpartum. 1, 5
• Holter monitoring is appropriate if symptoms continue to detect paroxysmal arrhythmias. 1, 5
• Assess for hyperthyroidism, as thyroid storm can precipitate atrial fibrillation or flutter with associated tachycardia. 6

Assess Family and Personal Cardiac History

• Personal history of previous arrhythmias, structural heart disease, or congenital heart disease increases risk of sustained tachycardia during pregnancy. 5
• Family history of sudden cardiac death, cardiomyopathy, or inherited arrhythmia syndromes (long QT syndrome, catecholaminergic polymorphic ventricular tachycardia) warrants close surveillance and continuation of beta-blocker therapy throughout pregnancy and the 40-week postpartum period. 2, 5

Management of Ventricular Tachycardia

• For sustained ventricular tachycardia with hemodynamic instability, immediate electrical cardioversion is recommended. 2
• For hemodynamically stable monomorphic sustained VT, consider IV sotalol or procainamide for acute conversion. 2
• IV amiodarone should be considered only when hemodynamically unstable, refractory to electrical cardioversion, or not responding to other drugs—use at the lowest effective dose due to fetal toxicity (FDA Category D). 2, 1
• For long-term management of idiopathic sustained VT, oral metoprolol, propranolol, or verapamil is recommended. 2

Special Pregnancy Considerations and Drug Safety

FDA Pregnancy Categories for Antiarrhythmic Drugs

• Category B (remote chance of fetal harm): Sotalol, lidocaine. 2
• Category C (potential benefits outweigh risk): Quinidine, adenosine, metoprolol, propranolol, verapamil, diltiazem, digoxin, flecainide, propafenone. 2
• Category D (positive evidence of risk): Phenytoin, amiodarone—use only when all other therapies have failed. 2, 1

Pharmacokinetic Alterations

• Drug levels need more careful monitoring during pregnancy as pharmacokinetics are altered by increased blood volume, cardiac output, and renal clearance. 1
• Position the patient in left lateral decubitus for symptomatic bradycardia or hypotension to relieve inferior vena cava compression. 1

Critical Pitfalls to Avoid

• Never use AV nodal blockers (adenosine, beta-blockers, calcium channel blockers) in patients with manifest pre-excitation on ECG, as this can precipitate ventricular fibrillation. 1
• Do not dismiss tachycardia as "normal pregnancy changes" without proper evaluation, as serious arrhythmias and structural disease can present similarly. 6
• Avoid amiodarone except as last resort due to fetal toxicity including thyroid dysfunction and growth restriction. 2, 1
• Do not use methylxanthines (caffeine, aminophylline, theophylline) in patients who experience seizures in association with adenosine administration. 2, 3
• Discontinue adenosine if patient develops persistent or symptomatic high-grade AV block, severe respiratory difficulties, or persistent hypotension. 3

When Conservative Management is Appropriate

• Most palpitations during pregnancy are benign, caused by atrial or ventricular extrasystoles or sinus tachycardia. 2, 6
• When benign arrhythmias are confirmed, provide reassurance and advise avoidance of stimulants such as caffeine, smoking, and alcohol. 2, 7
• No drug therapy is usually needed for supraventricular or ventricular premature beats if asymptomatic. 7, 4

Catheter Ablation Considerations

• Catheter ablation should be considered before pregnancy if the pregnancy is planned and the patient has symptomatic recurrent tachycardia. 2
• During pregnancy, catheter ablation may be considered only for drug-refractory and poorly tolerated tachycardias, though this should be reserved for special cases. 2, 1