What is the appropriate evaluation and treatment for a patient presenting with tachycardia?

Evaluation and Treatment of Tachycardia

Initial Assessment: Hemodynamic Stability and QRS Width

The immediate evaluation of tachycardia must first determine hemodynamic stability, then classify by QRS width (narrow <120ms vs wide ≥120ms), as this dictates both diagnosis and treatment urgency.

Hemodynamically Unstable Patients

• Synchronized cardioversion is the immediate treatment for any hemodynamically unstable tachycardia 1
• Signs of instability include: hypotension, altered mental status, chest pain with ischemia, acute heart failure
• Do not delay for pharmacologic attempts when the patient is unstable

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Narrow-Complex Tachycardia (QRS <120ms)

Acute Management Algorithm

First-line: Vagal maneuvers 1

• Valsalva maneuver: bearing down against closed glottis for 10-30 seconds (≥30-40 mmHg pressure)
• Carotid sinus massage: 5-10 seconds of steady pressure after confirming no bruit
• Ice-cold wet towel to face (diving reflex)
• Success rate approximately 27.7% when switching between techniques

Second-line: Adenosine 1

• Adenosine is the drug of choice when vagal maneuvers fail 2
• Terminates AVNRT in ~95% of cases
• Also serves diagnostic function by unmasking atrial activity in flutter/AT
• Class I recommendation with strong evidence

Third-line: AV nodal blocking agents (for hemodynamically stable patients) 1

• Intravenous diltiazem or verapamil are reasonable alternatives 1
• Intravenous beta-blockers are reasonable but less effective than calcium channel blockers
• Critical safety warning: Never give verapamil/diltiazem in wide-QRS tachycardia of unknown etiology or pre-excited AF—risk of ventricular fibrillation 2

Important 2020 Guideline Updates 2

The ESC 2019 guidelines made significant changes:

• Downgraded verapamil/diltiazem from previous recommendations for acute narrow-QRS tachycardias
• No longer recommended: amiodarone and digoxin for acute narrow-QRS tachycardias
• Adenosine remains the preferred agent with strengthened recommendations

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Wide-Complex Tachycardia (QRS ≥120ms)

Critical Diagnostic Principle

Assume ventricular tachycardia (VT) until proven otherwise—improper treatment of VT as SVT can be lethal 3, 4

Acute Management

For hemodynamically unstable wide-complex tachycardia:

• Immediate synchronized cardioversion 1

For hemodynamically stable wide-complex tachycardia:

1. Adenosine has strengthened recommendations for both diagnostic and therapeutic use 2

   • Will terminate SVT with aberrancy
   • Will not terminate VT but helps differentiate diagnosis
   • Safe in most wide-complex tachycardias

2. Avoid these medications 2:

   • Sotalol and lidocaine are no longer recommended for acute wide-QRS tachycardias
   • Procainamide and amiodarone have been downgraded
   • Never use verapamil/diltiazem in wide-QRS of unknown etiology

Special Consideration: Pre-excited Atrial Fibrillation

Absolute contraindications 2:

• Digoxin, beta-blockers, diltiazem, verapamil, and amiodarone are contraindicated
• These agents may accelerate ventricular response and precipitate ventricular fibrillation
• Treatment requires cardioversion or procainamide

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Focal Atrial Tachycardia

For hemodynamically stable focal AT: 1

• Intravenous beta-blockers, diltiazem, or verapamil (Class I recommendation)
• Terminates or slows rate in 30-50% of cases
• Monitor for hypotension/bradycardia

For hemodynamically unstable focal AT:

• Synchronized cardioversion 1

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Key Safety Pitfalls to Avoid

1. Never give AV nodal blockers (verapamil, diltiazem, beta-blockers, digoxin, amiodarone) in pre-excited AF or wide-QRS of unknown origin 2

2. Do not use flecainide/propafenone in:

   • Left bundle branch block
   • Ischemic or structural heart disease
   • Atrial flutter cardioversion
   • Patients with ventricular dysfunction 2

3. Avoid amiodarone for acute treatment of pre-excited AF 2

4. In pregnancy (first trimester):

   • Avoid all antiarrhythmics if possible
   • If necessary: beta-1-selective blockers (not atenolol) or verapamil for non-WPW patients
   • Flecainide/propafenone only for WPW without structural heart disease 2

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Disposition Considerations

• Wide-complex tachycardia represents 0.2% of ED visits with 53% admission rate and 2.3% ED mortality 5
• 50% are primary arrhythmias, 50% are secondary to underlying medical conditions 5
• For secondary tachycardias: Failure to treat the underlying cause (sepsis, PE, hypovolemia, etc.) is a common management error—34.4% of secondary cases were discharged without adequate rate control 5
• Target heart rate <100 bpm before discharge for controlled cases