What is the algorithm for managing adult tachycardia?

Adult Tachycardia Management Algorithm

Initial Assessment: Determine Hemodynamic Stability

The first critical decision is whether the patient is hemodynamically stable or unstable—this determines whether you proceed with immediate cardioversion or stepwise pharmacologic management. 1

Signs of Hemodynamic Instability (Proceed to Immediate Cardioversion):

• Acute altered mental status or loss of consciousness 1, 2
• Ischemic chest discomfort 1
• Acute heart failure 1
• Hypotension or signs of shock 1
• Syncope 1

Critical caveat: If heart rate is <150 bpm without ventricular dysfunction, the tachycardia is more likely secondary to an underlying condition rather than the primary cause of instability 1

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Pathway 1: UNSTABLE Patient (Immediate Action Required)

Proceed directly to synchronized cardioversion without attempting vagal maneuvers or medications. 1, 3, 4

Synchronized Cardioversion Protocol:

• Initial energy: 50-100 J biphasic 4
• Increase dose stepwise if initial shock fails 4
• Perform after adequate sedation/anesthesia when possible 1, 4
• Have resuscitation equipment immediately available 4

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Pathway 2: STABLE Patient (Stepwise Approach)

Step 1: Classify the Tachycardia (Narrow vs. Wide QRS)

Obtain a 12-lead ECG to determine QRS duration, but do not delay treatment if patient becomes unstable 1

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NARROW-COMPLEX Tachycardia (QRS <0.12 seconds)

First-Line: Vagal Maneuvers

Vagal maneuvers are the recommended first-line intervention and should be attempted immediately in all hemodynamically stable patients. 1, 3, 4

Technique (perform with patient supine):

• Modified Valsalva maneuver (most effective): Patient bears down against closed glottis for 10-30 seconds (equivalent to 30-40 mmHg), then immediately lie flat with legs elevated 1, 4
• Carotid sinus massage: After confirming absence of bruit, apply steady pressure over right or left carotid sinus for 5-10 seconds 1
• Ice-cold wet towel to face: Alternative vagal maneuver based on diving reflex 1, 3
• Success rate: 27.7% when switching between techniques; modified Valsalva achieves ~43% success 3, 4

Never apply pressure to the eyeball—this is dangerous and abandoned. 1

Second-Line: Adenosine

If vagal maneuvers fail, adenosine is the next intervention with 90-95% effectiveness for terminating SVT. 1, 3, 4

Adenosine Dosing Protocol:

• First dose: 6 mg rapid IV push via large peripheral vein, followed immediately by 20 mL saline flush 1, 4
• Second dose: 12 mg if first dose ineffective 1
• Have electrical cardioversion equipment immediately available 4

Adenosine Dose Adjustments:

• Reduce to 3 mg for patients taking dipyridamole, carbamazepine, or with transplanted heart 4
• Larger doses may be needed with theophylline, caffeine, or theobromine 4

Adenosine Contraindications and Warnings:

• Contraindicated in asthma patients—can cause severe bronchoconstriction 4
• Brief side effects occur in ~30% of patients but last <1 minute 3
• Serves dual purpose: therapeutic and diagnostic by unmasking atrial activity in atrial flutter or atrial tachycardia 1, 3

Third-Line: AV Nodal Blocking Agents

If adenosine fails or is contraindicated, use intravenous diltiazem, verapamil, or beta blockers. 1, 3

Calcium Channel Blockers (Diltiazem or Verapamil):

• Effectiveness: 64-98% conversion rate for SVT 1
• Diltiazem dosing: Slow infusion up to 20 minutes may lessen hypotension risk 1
• Mechanism: Slows AV nodal conduction and prolongs AV nodal refractoriness 5
• Diltiazem is more effective than beta blockers for terminating SVT 1

Beta Blockers:

• Reasonable alternative with excellent safety profile 1
• Less effective than diltiazem but safer in certain populations 1

Critical Safety Warnings for AV Nodal Blockers:

• Do NOT use in:
  • Wide-complex tachycardia of uncertain etiology 4
  • Pre-excited atrial fibrillation (WPW syndrome) 1, 3, 4
  • Suspected systolic heart failure 1, 4
  • Ventricular tachycardia 1
• Risk: May cause hemodynamic collapse, accelerated ventricular rate, or precipitate ventricular fibrillation 1, 4

Fourth-Line: Synchronized Cardioversion

If pharmacologic therapy fails or is contraindicated in stable patients, proceed to synchronized cardioversion. 1

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WIDE-COMPLEX Tachycardia (QRS ≥0.12 seconds)

Critical Decision Point: Assume Ventricular Tachycardia Until Proven Otherwise

Wide-complex tachycardia should be presumed to be ventricular tachycardia (VT) and treated accordingly—improper treatment can be lethal. 1, 6

Differential Diagnosis:

• Ventricular tachycardia (most common) 1
• SVT with aberrancy 1
• Pre-excited tachycardia (WPW syndrome) 1
• Ventricular paced rhythms 1

Management Based on Regularity:

Regular Wide-Complex Tachycardia (Likely VT or SVT with aberrancy):

If stable and rhythm cannot be definitively identified, adenosine is relatively safe for both diagnosis and treatment (Class IIb). 1

However, adenosine should NOT be given for:

• Unstable patients 1
• Irregular wide-complex tachycardia 1
• Polymorphic wide-complex tachycardia 1

Antiarrhythmic Therapy for Stable VT:

First-line options (in order of preference based on evidence):

1. Amiodarone: 150 mg IV over 10 minutes; repeat as needed up to maximum 2.2 g/24 hours 1

   • Most effective for preventing recurrent monomorphic VT 1
   • Higher doses (300 mg) associated with increased hypotension 1

2. Procainamide: 20-50 mg/min until arrhythmia suppressed, hypotension occurs, QRS increases >50%, or maximum 17 mg/kg given 1

   • Maintenance infusion: 1-4 mg/min 1
   • Avoid if prolonged QT or CHF 1

3. Sotalol: 1.5 mg/kg IV over 5 minutes 1

   • Relatively safe and effective 1
   • Avoid in patients with prolonged QT interval 1

4. Lidocaine: Second-line agent, less effective than above options 1

Irregular Wide-Complex Tachycardia:

Likely atrial fibrillation with aberrancy, pre-excited atrial fibrillation, or polymorphic VT/torsades de pointes 1

For pre-excited atrial fibrillation:

• Use ibutilide or IV procainamide 3
• Do NOT use calcium channel blockers, beta blockers, or digoxin—may enhance accessory pathway conduction and precipitate ventricular fibrillation 3, 4

Unstable Wide-Complex Tachycardia:

Proceed immediately to unsynchronized defibrillation if polymorphic VT/VF, or synchronized cardioversion if monomorphic VT. 1

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Special Considerations

Automatic Tachycardias (Not Responsive to Cardioversion):

• Ectopic atrial tachycardia 4
• Multifocal atrial tachycardia 4
• Junctional tachycardia 4
• Management: Rate control with AV nodal blocking agents, not cardioversion 4

Common Pitfalls to Avoid:

• Treating sinus tachycardia as primary arrhythmia when it's secondary to underlying condition (fever, dehydration, etc.) 1
• Using AV nodal blockers in pre-excited rhythms 3, 4
• Delaying cardioversion in unstable patients to attempt pharmacologic therapy 1, 4
• Misdiagnosing anxiety/panic disorder when SVT is the actual cause 7

Long-Term Management:

• All patients treated for SVT should be referred to a heart rhythm specialist 8
• Oral verapamil or diltiazem recommended for ongoing AVNRT management 1
• Catheter ablation is potentially curative and should be considered for recurrent SVT 1, 7, 8