What is the initial approach to treating tachycardia?

Initial Approach to Treating Tachycardia

The initial approach to tachycardia begins with immediate assessment of hemodynamic stability—if the patient shows signs of shock, hypotension, acute altered mental status, ischemic chest pain, or acute heart failure, proceed directly to synchronized cardioversion; if stable, obtain a 12-lead ECG to classify the rhythm by QRS width and regularity, then treat accordingly. 1

Immediate Stabilization Steps

All patients with tachycardia require:

• Attachment of cardiac monitor, blood pressure evaluation, and establishment of IV access 1
• Assessment of oxygen saturation via pulse oximetry and evaluation for signs of increased work of breathing (tachypnea, retractions, paradoxical abdominal breathing) 2, 1
• Supplementary oxygen if oxygenation is inadequate or respiratory distress is present 1
• Identification of potential reversible causes (hypoxemia, infection, dehydration, metabolic derangements, hypotension) while initiating treatment 2, 1

Algorithm Based on Hemodynamic Stability

Unstable Patients (Rate-Related Cardiovascular Compromise)

Immediate synchronized cardioversion is indicated without delay if the patient demonstrates any of the following 2, 1:

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

Key procedural points:

• Sedate the patient prior to cardioversion if conscious and time permits 1
• For unstable wide-complex tachycardia, presume ventricular tachycardia and perform immediate cardioversion 1
• Consider precordial thump for witnessed, monitored unstable ventricular tachycardia if a defibrillator is not immediately ready 1
• Do not delay cardioversion to obtain a 12-lead ECG in unstable patients 1

Stable Patients (Systematic Approach)

For stable patients, obtain a 12-lead ECG to classify the rhythm 2, 1. The classification determines treatment:

Step 1: Determine QRS Width

Narrow-Complex Tachycardia (QRS <0.12 seconds):

• If regular rhythm: Most likely AV nodal reentrant tachycardia (AVNRT) or AV reciprocating tachycardia (AVRT) 2

  • First-line treatment: Adenosine 6 mg rapid IV push followed immediately by saline flush 2, 1, 3
  • If no effect after 1-2 minutes, give 12 mg rapid IV push 2, 1, 3
  • Success rate approximately 93% 3
  • Vagal maneuvers (Valsalva, carotid sinus massage) can be attempted first and may terminate the arrhythmia 2

• If irregular rhythm: Most likely atrial fibrillation or multifocal atrial tachycardia 2

  • Initial approach involves rate control with IV diltiazem, beta-blocker, or digoxin 2
  • Beta-blockers are most effective for controlling ventricular response and accelerate conversion to sinus rhythm compared to diltiazem 2
  • Cardioversion is generally not recommended until underlying problems are corrected 2

Wide-Complex Tachycardia (QRS ≥0.12 seconds):

Treat as ventricular tachycardia unless proven otherwise 1. Most wide-complex tachycardias are ventricular in origin 2.

• If regular and monomorphic:

  • Amiodarone 150 mg IV over 10 minutes is recommended for stable ventricular tachycardia 2, 1, 4
  • Maintenance infusion: 1 mg/min for first 6 hours 2
  • Adenosine can be used for both treatment and diagnosis of regular monomorphic wide-complex tachycardia of uncertain origin, but use with caution 1
  • Alternative: Procainamide 20-50 mg/min until arrhythmia suppressed, hypotension ensues, QRS increases >50%, or maximum dose 17 mg/kg given 2

• If irregular or polymorphic: Do not administer adenosine 1

Critical Rate Threshold

Heart rates <150 beats/minute are unlikely to cause symptoms of instability unless ventricular function is impaired 2, 1. When heart rate is ≥150 beats/minute, the tachycardia is more likely the primary arrhythmia rather than a physiologic response 2.

Sinus tachycardia (gradual onset/termination, non-paroxysmal) requires treatment of the underlying cause rather than specific antiarrhythmic therapy 2, 1. Look for stressors such as fever, infection, volume loss, or dehydration 2.

Critical Safety Considerations and Pitfalls

Absolute contraindications and dangerous errors:

• Never use AV nodal blocking agents (adenosine, calcium channel blockers, beta-blockers) in pre-excited atrial fibrillation or flutter (Wolff-Parkinson-White syndrome)—this can accelerate ventricular response and precipitate ventricular fibrillation 1, 3
• Never administer verapamil or diltiazem for presumed SVT when the rhythm is actually ventricular tachycardia—this causes hemodynamic collapse or ventricular fibrillation 1
• Avoid adenosine in irregular or polymorphic wide-complex tachycardia 1
• Avoid sotalol in patients with prolonged QT interval 1
• Avoid procainamide if prolonged QT or congestive heart failure is present 2

Common management errors:

• Do not delay cardioversion in unstable patients while waiting for 12-lead ECG 1
• Do not normalize heart rate in compensatory tachycardias where cardiac output depends on rapid rate 1
• Avoid using multiple AV nodal blocking agents with overlapping half-lives, which can cause profound bradycardia 1
• Adenosine must be administered in a monitored environment due to risk of transient complete heart block and bronchospasm (contraindicated in asthmatics) 3

Special Diagnostic Considerations

If pre-excitation (delta wave) is present on baseline ECG in a patient with paroxysmal regular palpitations, this is sufficient for presumptive diagnosis of AVRT and warrants immediate referral to an arrhythmia specialist 2. If irregular palpitations occur with pre-excitation, this suggests atrial fibrillation with rapid conduction over an accessory pathway—this requires immediate electrophysiological evaluation due to risk of sudden death 2.