What is the initial approach for managing tachycardia in Advanced Cardiovascular Life Support (ACLS)?

ACLS Management of Tachycardia

The initial approach to tachycardia in ACLS begins with immediate assessment of hemodynamic stability: if the patient shows signs of instability (altered mental status, chest pain, acute heart failure, hypotension, or shock) with a heart rate typically ≥150 bpm, proceed directly to synchronized cardioversion; if stable, provide oxygen, obtain IV access and a 12-lead ECG, identify the rhythm, and treat the underlying cause. 1

Initial Assessment and Stabilization

Assess for hemodynamic instability first — this determines whether you have seconds or minutes to act:

• Evaluate oxygenation immediately: Look for tachypnea, intercostal retractions, suprasternal retractions, and paradoxical abdominal breathing 1
• Provide supplemental oxygen if oxyhemoglobin saturation is inadequate or work of breathing is increased 1
• Attach cardiac monitor, establish IV access, and obtain blood pressure 1
• Obtain 12-lead ECG to define the rhythm, but do not delay cardioversion if the patient is unstable 1

Critical Decision Point: Stable vs. Unstable

Unstable Tachycardia (Immediate Action Required)

Proceed to immediate synchronized cardioversion if the patient demonstrates rate-related cardiovascular compromise with any of these signs: 1

• Acute altered mental status
• Ischemic chest discomfort
• Acute heart failure
• Hypotension or signs of shock

Important caveat: When heart rate is <150 bpm, symptoms are unlikely to be caused primarily by the tachycardia unless ventricular function is impaired — in this case, the tachycardia is more likely secondary to an underlying condition 1

Exception for narrow-complex SVT: If the patient is not hypotensive and has a regular narrow-complex SVT, adenosine may be administered while preparing for synchronized cardioversion 1

Stable Tachycardia (Time for Systematic Approach)

When the patient is stable, determine if the tachycardia is:

1. Primary cause of symptoms, or
2. Secondary response to underlying conditions (fever, dehydration, anemia, hypotension) 1

Rhythm-Specific Management

Sinus Tachycardia

Do not treat sinus tachycardia with antiarrhythmics — it is a physiologic response to an underlying condition 1

• Heart rate >100 bpm but typically within age-predicted maximum (approximately 220 minus patient's age) 1
• Direct therapy toward identifying and treating the underlying cause (fever, anemia, hypotension/shock) 1
• Critical pitfall: When cardiac function is poor, cardiac output depends on rapid heart rate; "normalizing" the rate can be detrimental 1

Narrow-Complex Regular Tachycardia (SVT)

First-line treatment sequence: 1

1. Vagal maneuvers (Valsalva, carotid massage) 1
2. Adenosine 6 mg rapid IV push followed by 20 mL saline flush; if ineffective, give 12 mg 1
   • Success rates: 78-96% for AVNRT and AVRT 1
   • Administer via proximal IV as rapid bolus 1
   • Contraindicated in asthma (may cause bronchospasm) 1
   • Have defibrillator ready: May precipitate atrial fibrillation, which can be very rapid in patients with WPW 1

Second-line agents (if adenosine fails or recurs): 1

• IV diltiazem or verapamil: 64-98% conversion rate 1

  • Use only in hemodynamically stable patients 1
  • Do not use if VT or pre-excited AF suspected — may cause hemodynamic collapse or accelerated ventricular rate leading to VF 1
  • Avoid in suspected systolic heart failure 1

• IV beta-blockers: Reasonable alternative 1

Synchronized cardioversion is recommended if pharmacologic therapy is ineffective or contraindicated 1

Wide-Complex Tachycardia

Assume ventricular tachycardia until proven otherwise — this is the safest approach 1, 2

For stable monomorphic VT: 1

• IV procainamide (20-50 mg/min) is reasonable for initial treatment when early slowing and termination are desired 1

  • Stop if: arrhythmia suppressed, hypotension develops, QRS widens >50%, or maximum dose 17 mg/kg reached 1
  • Avoid if prolonged QT or CHF 1

• IV amiodarone (150 mg over 10 minutes) is reasonable for hemodynamically unstable VT, refractory to cardioversion, or recurrent despite other agents 1

• IV lidocaine may be reasonable specifically for ischemia-related VT, but is less effective than procainamide or amiodarone 1

For unstable or polymorphic VT: Immediate defibrillation 1

Polymorphic VT (Torsades de Pointes)

If long QT interval present during sinus rhythm: 1

1. Stop all QT-prolonging medications immediately 1
2. Correct electrolyte abnormalities (especially hypokalemia, hypomagnesemia) 1
3. IV magnesium is first-line treatment 1
4. Consider pacing or IV isoproterenol if associated with bradycardia or pause-dependent 1
5. Avoid isoproterenol in familial long QT syndrome 1

If normal QT interval: Most commonly due to myocardial ischemia — treat with IV amiodarone and beta-blockers 1

Synchronized Cardioversion Technique

When cardioversion is indicated: 1

• Establish IV access before cardioversion if possible 1
• Administer sedation if patient is conscious 1
• Do not delay if patient is extremely unstable 1
• Shock delivery is timed (synchronized) with QRS complex to avoid the relative refractory period when shock could produce VF 1

Common Pitfalls to Avoid

• Never assume narrow-complex tachycardia is benign — assess hemodynamic stability first 1
• Never give calcium channel blockers or beta-blockers for wide-complex tachycardia unless VT is definitively ruled out 1
• Never treat compensatory sinus tachycardia with rate-control agents — this can precipitate cardiovascular collapse 1
• Never delay cardioversion in unstable patients to obtain a 12-lead ECG 1
• Always have defibrillator ready when giving adenosine — may precipitate rapid AF in WPW 1