What is the appropriate management for a 28 weeks pregnant woman presenting with tachycardia, diaphoresis, and shortness of breath?

Management of Tachycardia, Diaphoresis, and Shortness of Breath at 28 Weeks Gestation

This patient requires immediate evaluation for hemodynamic stability, followed by a stepwise approach starting with vagal maneuvers, then IV adenosine if unsuccessful, and immediate electrical cardioversion if hemodynamically unstable. 1, 2

Immediate Assessment and Stabilization

Determine Hemodynamic Stability

• If hemodynamically unstable (hypotension, altered mental status, chest pain, or signs of shock): perform immediate electrical cardioversion using the same protocol as non-pregnant patients with biphasic shock energy of 120-200 J 3, 1
• Cardioversion is not contraindicated in pregnancy and should be used for any sustained tachycardia causing hemodynamic instability that threatens fetal security 3
• The lateral defibrillator pad should be placed under the breast tissue 3

If Hemodynamically Stable: Stepwise Treatment Algorithm

1. First-line: Attempt vagal stimulation maneuvers 3, 1, 4
2. Second-line: If vagal maneuvers fail, administer IV adenosine (terminates approximately 30% of atrial tachycardias and most supraventricular tachycardias) 3, 1, 4
3. Third-line: If adenosine fails, administer IV metoprolol (cardioselective beta-blocker) 1, 2, 4

Critical Differential Diagnoses to Rule Out

Life-Threatening Conditions Requiring Urgent Intervention

• Pulmonary embolism: Pregnancy is a hypercoagulable state; tachycardia, diaphoresis, and dyspnea are classic presenting symptoms 5
• Peripartum cardiomyopathy: Can present with new-onset ventricular tachycardia during the last 6 weeks of pregnancy or postpartum 3
• Thyroid storm: Hyperthyroidism can precipitate atrial fibrillation or flutter and presents with tachycardia, diaphoresis, and dyspnea 3, 4
• Pheochromocytoma: Rare but can cause myocardial infarction, arrhythmias, and the triad of symptoms described; diagnose with 24-hour urine catecholamines 6
• Cardiac tamponade: Can present with tachycardia and dyspnea; requires urgent echocardiography 7

Arrhythmia-Specific Considerations

• Supraventricular tachycardias occur in 20-44% of pregnancies and are the most common arrhythmia 2, 5
• Atrial fibrillation/flutter are rare unless structural heart disease or hyperthyroidism is present 3, 4
• Ventricular tachycardia is uncommon but life-threatening; verapamil-sensitive idiopathic left ventricular tachycardia can present at 28 weeks with wide complex tachycardia 8

Essential Diagnostic Workup

Immediate Testing

• 12-lead ECG: Identify rhythm, look for pre-excitation patterns (avoid AV nodal blockers if present), assess for ischemia or structural abnormalities 1, 2
• Echocardiogram: Rule out structural heart disease, assess ventricular function, evaluate for peripartum cardiomyopathy, and exclude pericardial effusion 1, 2, 5
• Continuous fetal monitoring: Assess fetal heart rate and well-being, as maternal arrhythmias can cause fetal hypoperfusion 3, 1

Additional Laboratory Studies

• Thyroid function tests (TSH, free T4) to exclude hyperthyroidism 3, 4
• Serum electrolytes, particularly potassium and magnesium (hypokalemia of pregnancy can promote arrhythmias) 4
• Complete blood count and D-dimer if pulmonary embolism suspected 5
• 24-hour urine catecholamines and metanephrines if pheochromocytoma suspected (especially if hypertensive) 6

Follow-up Monitoring

• Holter monitor for 24-48 hours if symptoms persist or recur to capture arrhythmia episodes 1, 2

Long-Term Management and Prophylaxis

First-Line Prophylactic Therapy

• Cardioselective beta-blockers (metoprolol or propranolol) are first-line for preventing recurrent supraventricular tachycardia 3, 1, 2
• Beta-blockers should be used with caution in the first trimester but are generally safe thereafter 3

Second-Line Options

• Digoxin can be used for rate control in combination with beta-blockers 3, 1
• Sotalol, flecainide, or propafenone may be considered if first-line agents fail 3, 1

Medications to Avoid or Use with Extreme Caution

• Amiodarone: Only use when all other therapies have failed and at the lowest effective dose due to fetotoxic effects including neonatal hypothyroidism (9% of newborns), hyperthyroidism, and goiter 3, 1
• Verapamil: Can cause fetal bradycardia and maternal constipation; use only if beta-blockers are contraindicated 3, 4
• AV nodal blocking agents: Contraindicated if pre-excitation is present on ECG 3, 1

Special Considerations for Pregnancy

Pharmacokinetic Changes

• Drug levels need to be monitored more carefully during pregnancy as pharmacokinetics are altered 3
• If gentamicin is required (for endocarditis), levels must be checked with particular care due to risk of fetal deafness 3

Anticoagulation Requirements

• If atrial fibrillation or flutter is documented and duration is ≥48 hours or unknown, therapeutic anticoagulation with LMWH or warfarin (depending on trimester) is required for at least 3 weeks before and 4 weeks after cardioversion 3, 1
• For AF <48 hours duration without thromboembolic risk factors, IV heparin or therapeutic LMWH may be given peri-cardioversion 3

Invasive Procedures During Pregnancy

• Catheter ablation: Should only be considered for drug-refractory and poorly tolerated tachycardias, using echocardiographic guidance with maximal shielding and minimal fluoroscopy 3, 1
• Pacemaker or ICD implantation: Can be performed at any stage of pregnancy using echo guidance, preferably single-chamber devices if fetus is beyond 8 weeks gestation 3

Critical Pitfalls to Avoid

• Do not delay cardioversion in hemodynamically unstable patients due to concerns about pregnancy; maternal stability is essential for fetal survival 3
• Do not use AV nodal blockers (adenosine, beta-blockers, calcium channel blockers) in patients with manifest pre-excitation on ECG as this can precipitate ventricular fibrillation 3, 1
• Do not miss underlying structural heart disease: Always obtain echocardiogram in pregnant patients with documented arrhythmias 1, 2, 5
• Do not attribute all symptoms to pregnancy: This presentation could represent pulmonary embolism, thyroid storm, or other life-threatening conditions 5, 4, 6
• Do not use magnesium sulfate beyond 5-7 days: Continuous use can cause fetal abnormalities including hypocalcemia, skeletal demineralization, and osteopenia 9

When to Escalate Care

Immediate Emergency Department Transfer Required For:

• Recurrent episodes of tachycardia with symptoms 1, 2
• Development of syncope or near-syncope 2
• Worsening dyspnea or chest pain 2
• Any signs of hemodynamic instability (hypotension, altered mental status) 3, 2
• Sustained tachycardia not responding to initial management 3, 5