What is the differential diagnosis and management for a pregnant female experiencing episodic palpitations?

Differential Diagnosis of Episodic Palpitations in Pregnancy

Most palpitations in pregnancy are benign, caused by atrial or ventricular premature complexes or sinus tachycardia, but new-onset ventricular tachycardia and supraventricular arrhythmias requiring investigation for structural heart disease must be ruled out. 1

Benign Arrhythmias (Most Common)

• Atrial or ventricular premature complexes are the most frequent cause of palpitations during pregnancy and typically require only reassurance 1
• Sinus tachycardia is extremely common due to increased cardiac output and sympathetic tone during pregnancy 1
• These benign arrhythmias warrant elimination of stimulants including caffeine, smoking, and alcohol rather than pharmacotherapy 1

Supraventricular Tachycardias

• Paroxysmal supraventricular tachycardia (SVT) occurs in 20-44% of pregnancies, with symptomatic exacerbation common in those with pre-existing arrhythmias 1, 2
• Atrioventricular nodal re-entry tachycardia (AVNRT) and atrioventricular re-entry tachycardia (AVRT) are the most common mechanisms of SVT in pregnancy 1
• Atrial flutter is poorly tolerated and can cause fetal hypoperfusion, particularly in patients with structural heart disease 1
• Atrial fibrillation is rare during pregnancy unless structural heart disease or hyperthyroidism is present 1

Ventricular Arrhythmias

• New-onset ventricular tachycardia (VT) may present during pregnancy, often related to elevated catecholamines, and is of significant concern 1
• Idiopathic VT from the right ventricular outflow tract (RVOT) can occur in structurally normal hearts and responds to verapamil or beta-blockers 1
• Idiopathic fascicular left VT typically does not respond to beta-blockers but may be treated with verapamil 1
• Risk of recurrent VT is substantially higher in patients with previous VT and structural heart disease 1

Structural Heart Disease

• Peripartum cardiomyopathy should be ruled out in any woman presenting with new-onset VT during the last 6 weeks of pregnancy or postpartum period 1, 2
• Hypertrophic cardiomyopathy (HCM) with left ventricular outflow tract obstruction can present with arrhythmias during pregnancy 1
• Congenital heart disease increases arrhythmia risk, with sustained tachycardia developing in up to 15% of these patients during pregnancy 1
• Valvular heart disease and cardiomyopathy can precipitate arrhythmias due to the hemodynamic burden of pregnancy 3, 4

Inherited Arrhythmia Syndromes

• Long QT syndrome (LQTS) carries substantial risk of cardiac events in the postpartum period (40 weeks after delivery), requiring continued beta-blocker therapy 1
• Catecholaminergic polymorphic ventricular tachycardia (CPVT) requires beta-blocker therapy throughout pregnancy and postpartum 1
• Wolff-Parkinson-White syndrome may present with palpitations at young age associated with fast heart rate 5
• Patients with family history of sudden death, cardiomyopathy, or inherited arrhythmia syndromes warrant close surveillance 1, 2

Non-Cardiac Causes

• Hyperthyroidism/thyroid storm can precipitate atrial fibrillation or flutter with associated tachycardia 2, 6
• Pulmonary disease including pulmonary embolism should be considered in the differential 3
• Metabolic disturbances including hypokalemia of pregnancy can promote arrhythmias 4
• Mitral valve prolapse is frequently associated with palpitations in women 5

Essential Diagnostic Workup

• 12-lead ECG should be obtained immediately to confirm narrow versus wide complex tachycardia and evaluate for pre-excitation patterns or conduction abnormalities 2, 6
• Holter monitoring is appropriate to detect arrhythmias if symptoms continue or are episodic 2, 6
• Echocardiography must be performed to rule out structural heart disease, particularly peripartum cardiomyopathy, in any patient with documented arrhythmias 2, 6
• Thyroid function tests should be assessed to rule out hyperthyroidism as a precipitant 2, 6
• Continuous fetal monitoring is essential during any arrhythmia episode, as maternal arrhythmias can cause fetal hypoperfusion 2, 7

Critical Red Flags Requiring Urgent Evaluation

• Syncope or presyncope with palpitations warrants immediate investigation for ventricular arrhythmias or heart block 1
• Hemodynamic instability during tachycardia episodes requires immediate electrical cardioversion 1, 2
• Personal or family history of sudden cardiac death mandates close surveillance with prompt investigation 1, 2
• Palpitations associated with chest pain, dyspnea, or diaphoresis may indicate serious underlying pathology 2

Common Pitfalls to Avoid

• Never dismiss palpitations as "normal pregnancy changes" without proper evaluation, particularly if new-onset or associated with concerning symptoms 2
• Do not use AV nodal blocking agents (adenosine, beta-blockers, calcium channel blockers) in patients with manifest pre-excitation on ECG, as this can precipitate ventricular fibrillation 1, 2, 7
• Avoid atenolol for any arrhythmia in pregnancy due to potential harmful fetal effects 2, 6
• Reserve amiodarone only as last resort when all other therapies have failed, using the lowest effective dose due to fetal toxicity including thyroid dysfunction and growth restriction 1