What is the initial management for symptomatic tachycardia?

Initial Management of Symptomatic Tachycardia

If the tachycardic patient is unstable with severe signs and symptoms related to the arrhythmia (acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or other signs of shock), perform immediate synchronized cardioversion with prior sedation in the conscious patient. 1

Immediate Assessment

• Assess hemodynamic stability first by evaluating for rate-related cardiovascular compromise: acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or other signs of shock. 1
• Provide supplementary oxygen and support airway/ventilation if needed, as hypoxemia commonly causes tachycardia. 1
• Attach cardiac monitor, evaluate blood pressure, and establish IV access immediately. 1
• Obtain a 12-lead ECG to define the rhythm, but do not delay cardioversion if the patient is unstable. 1

Critical Decision Point: Stable vs. Unstable

For UNSTABLE Patients (Hemodynamically Compromised)

Proceed immediately to synchronized cardioversion (Class I, LOE B). 1

• Sedate the conscious patient before cardioversion. 1
• Have resuscitation capabilities including DC cardioversion/defibrillation immediately available. 2
• Important caveat: With ventricular rates <150 bpm in the absence of ventricular dysfunction, the tachycardia is more likely secondary to an underlying condition rather than the cause of instability. 1

For STABLE Patients (Hemodynamically Stable)

The approach depends on whether the tachycardia is narrow-complex or wide-complex:

Narrow-Complex Tachycardia (QRS <0.12 seconds)

First-line interventions:

1. Vagal maneuvers (Class I, LOE B-R): 1

   • Valsalva maneuver: Patient bears down against closed glottis for 10-30 seconds (equivalent to 30-40 mm Hg pressure) in supine position. 1
   • Carotid sinus massage: Apply steady pressure over carotid sinus for 5-10 seconds after confirming absence of bruit. 1
   • Ice-cold wet towel to face (diving reflex). 1

2. Adenosine if vagal maneuvers fail (Class I, LOE B-R): 1

   • First dose: 6 mg rapid IV push followed by NS flush. 1
   • Second dose: 12 mg if required. 1
   • Terminates AVNRT in approximately 95% of patients and regular narrow-complex SVT in 90-95% of cases. 1
   • Have electrical cardioversion available as adenosine may precipitate atrial fibrillation with rapid ventricular response. 1

3. Alternative pharmacologic agents if adenosine fails or is contraindicated (Class IIa, LOE B-R): 1

   • IV diltiazem or verapamil for hemodynamically stable patients. 1
   • IV beta blockers are reasonable but less effective than calcium channel blockers. 1
   • Critical contraindication: Do not use diltiazem, verapamil, or beta blockers if pre-excitation (WPW) is present, as these may cause life-threatening acceleration of ventricular rate if atrial fibrillation develops. 1, 2

4. Synchronized cardioversion if pharmacologic therapy fails or is contraindicated (Class I, LOE B-NR). 1

Wide-Complex Tachycardia (QRS ≥0.12 seconds)

Assume ventricular tachycardia until proven otherwise, as improper treatment has potentially lethal consequences. 1, 3

For regular, monomorphic wide-complex tachycardia in stable patients:

1. IV procainamide (Class I recommendation for hemodynamically stable monomorphic VT): 1, 4

   • 20-50 mg/min until arrhythmia suppressed, hypotension develops, QRS widens >50%, or maximum dose of 17 mg/kg given. 1, 4
   • Maintenance infusion: 1-4 mg/min. 1
   • Avoid if prolonged QT or CHF present. 1

2. IV amiodarone as alternative: 1

   • 150 mg over 10 minutes, may repeat if VT recurs. 1
   • Follow with maintenance infusion of 1 mg/min for first 6 hours. 1

3. IV adenosine may be considered for undifferentiated regular stable wide-complex tachycardia (Class IIb, LOE B): 1

   • Relatively safe for both treatment and diagnosis. 1
   • Never use for irregular or polymorphic wide-complex tachycardia, as it may cause degeneration to ventricular fibrillation (Class III, LOE C). 1

4. Synchronized cardioversion if medications fail or patient becomes unstable. 1

Special Considerations and Pitfalls

• Do not use verapamil for wide-complex tachycardia unless known to be supraventricular origin (Class III, LOE B). 1, 2
• IV diltiazem and IV beta-blockers should not be administered together or in close proximity (within a few hours). 2
• For patients with pre-excited atrial fibrillation (atrial fibrillation with WPW), avoid AV nodal blocking agents (adenosine, diltiazem, verapamil, beta blockers, digoxin) as they may cause life-threatening ventricular rates; use immediate cardioversion if unstable or IV procainamide or ibutilide if stable. 1, 2
• Sinus tachycardia (rate typically <150 bpm, gradual onset/termination) requires treatment of underlying cause, not the rhythm itself. 1
• At rates <150 bpm, consider whether tachycardia is secondary to underlying condition (fever, dehydration, shock) rather than primary arrhythmia. 1