How should acute supraventricular tachycardia be managed in a hypotensive patient?

Management of Acute Supraventricular Tachycardia in a Hypotensive Patient

Proceed directly to synchronized cardioversion for any patient with supraventricular tachycardia presenting with hypotension, as this represents hemodynamic instability requiring immediate electrical therapy. 1, 2

Defining Hemodynamic Instability

Your patient meets criteria for hemodynamic instability based on hypotension alone. Additional signs that would also mandate immediate cardioversion include: 2

• Systolic blood pressure <90 mmHg (your patient)
• Syncope or altered mental status
• Signs of myocardial ischemia (chest pain with ST-segment changes)
• Acute pulmonary edema or severe heart failure
• Signs of shock

Immediate Management Algorithm

Step 1: Prepare for Synchronized Cardioversion

Synchronized cardioversion is the Class I, Level B recommendation for hemodynamically unstable SVT, with initial energy of 50-100 J. 2 This achieves near 100% termination of SVT in unstable patients. 3, 2

• Have defibrillator and emergency equipment immediately available 4
• Provide procedural sedation if the patient is conscious 2
• Ensure continuous ECG monitoring and frequent blood pressure measurement 4

Step 2: Consider One Dose of Adenosine (Optional, Only If Specific Criteria Met)

If the tachycardia is regular with a narrow QRS complex and the patient is not in frank shock, you may attempt one dose of adenosine 6 mg rapid IV push before cardioversion. 2, 5 However, this is optional and should not delay cardioversion. 1, 3

Critical safety requirement: Cardioversion equipment must be immediately available at bedside because adenosine can precipitate atrial fibrillation with rapid ventricular response, potentially triggering ventricular fibrillation. 2, 5

Adenosine achieves 90-95% success for AVNRT and orthodromic AVRT even in unstable patients. 2, 5 If you attempt adenosine:

• Administer 6 mg rapid IV push through a large proximal vein 3, 2
• Follow immediately with 20 mL saline flush 3
• If no conversion within 1-2 minutes, give 12 mg IV push 2
• Do not give a third dose in an unstable patient—proceed to cardioversion 2

Step 3: What NOT to Do in Hypotensive SVT

Never administer calcium channel blockers (diltiazem, verapamil) or beta-blockers to hypotensive patients—these can precipitate cardiovascular collapse. 3, 2

• Diltiazem and verapamil are absolutely contraindicated in hemodynamically unstable SVT 2
• IV metoprolol will worsen hypotension 2
• These agents are only appropriate for hemodynamically stable patients 1, 4

Special Diagnostic Considerations

Rule Out Pre-Excited Atrial Fibrillation

If the ECG shows irregular wide-complex tachycardia or you suspect Wolff-Parkinson-White syndrome with atrial fibrillation: 2

• Proceed immediately to synchronized cardioversion without attempting adenosine 2
• Do not use any AV nodal blocking agents (adenosine, calcium channel blockers, beta-blockers, digoxin) as these may enhance accessory pathway conduction and precipitate ventricular fibrillation 2

Obtain 12-Lead ECG

A 12-lead ECG during tachycardia is essential to differentiate SVT from ventricular tachycardia and identify pre-excitation. 3 A narrow QRS complex confirms supraventricular origin (likely AVNRT or orthodromic AVRT). 2

Post-Cardioversion Management

After successful cardioversion, anticipate: 2

• Premature atrial or ventricular complexes that may reinitiate tachycardia 2
• Have antiarrhythmic drugs ready to prevent acute reinitiation if recurrence occurs 2
• Continue continuous cardiac monitoring 3

Common Pitfalls to Avoid

1. Do not attempt vagal maneuvers in hypotensive patients—these waste time and are ineffective in unstable SVT. Vagal maneuvers are only for hemodynamically stable patients. 1, 3

2. Do not use procainamide—this is indicated for pre-excited atrial fibrillation, not regular narrow-complex SVT, and is too slow-acting for a patient in shock. 2

3. Do not delay cardioversion to obtain additional history, perform extensive workup, or attempt multiple medication trials. 1, 2

4. Do not confuse "low blood pressure" with "stable but anxious"—true hypotension (<90 mmHg systolic) mandates immediate cardioversion regardless of patient appearance. 2