Initial Management of Tachycardia
The initial management of tachycardia requires immediate assessment of hemodynamic stability and determination of the QRS complex width to guide appropriate treatment. 1
Assessment of Hemodynamic Stability
First, determine if the patient is stable or unstable:
Unstable Patient (Signs of Instability)
- Altered mental status
- Ischemic chest discomfort
- Acute heart failure
- Hypotension
- Signs of shock
Management for unstable patients:
- Immediate synchronized cardioversion (Class I, LOE B) 1
- For witnessed, monitored unstable ventricular tachycardia, precordial thump may be considered if a defibrillator is not immediately ready (Class IIb, LOE C) 1
- In select cases of regular narrow-complex tachycardia with unstable signs, a trial of adenosine before cardioversion may be reasonable (Class IIb, LOE C) 1
Stable Patient
For stable patients, proceed with the following algorithm:
1. Determine QRS Complex Width
Narrow Complex Tachycardia (QRS <0.12 seconds)
Possible diagnoses:
- Sinus tachycardia
- Atrial fibrillation
- Atrial flutter
- AV nodal reentry tachycardia (AVNRT)
- Accessory pathway-mediated tachycardia (AVRT)
- Atrial tachycardia
- Multifocal atrial tachycardia (MAT)
- Junctional tachycardia (rare in adults) 1
Wide Complex Tachycardia (QRS ≥0.12 seconds)
Possible diagnoses:
- Ventricular tachycardia (VT)
- Supraventricular tachycardia with aberrancy
- Pre-excited tachycardias (Wolff-Parkinson-White syndrome)
- Ventricular paced rhythms 1
2. Determine Regularity of Rhythm
Regular Narrow Complex Tachycardia
- First-line: Vagal maneuvers 2
- If unsuccessful: Adenosine IV
- First dose: 6 mg rapid IV push, followed by NS flush
- Second dose: 12 mg if required 1
- If adenosine fails: Consider calcium channel blockers or beta-blockers 1
Irregular Narrow Complex Tachycardia
- Likely atrial fibrillation, atrial flutter, or multifocal atrial tachycardia
- Rate control with AV nodal blocking agents (beta-blockers, calcium channel blockers)
- Caution: Avoid AV nodal blocking drugs in pre-excited atrial fibrillation or flutter (Class III, LOE C) 1
Regular Wide Complex Tachycardia
- Presume ventricular tachycardia until proven otherwise
- For stable patients with regular monomorphic wide-QRS tachycardia:
- IV adenosine may be reasonable for both treatment and diagnosis (Class IIb, LOE B) 1
- Amiodarone: 150 mg IV over 10 minutes, followed by maintenance infusion of 1 mg/min for 6 hours 1, 2
- Procainamide: 20-50 mg/min until arrhythmia suppressed, hypotension occurs, QRS increases >50%, or maximum dose of 17 mg/kg given 1
Irregular Wide Complex Tachycardia
- May be atrial fibrillation with aberrancy, pre-excited atrial fibrillation, or polymorphic VT/torsades de pointes
- Do not give adenosine for irregular or polymorphic wide-complex tachycardia 1
3. Identify and Treat Underlying Causes
Common underlying causes of tachycardia:
- Hypoxemia (provide supplemental oxygen if needed)
- Hypovolemia
- Fever/infection
- Pain
- Anemia
- Hyperthyroidism
- Heart failure
- Pulmonary embolism 1, 2
Important Considerations and Pitfalls
- Heart rate significance: Tachycardia is more likely to be the primary cause of symptoms when rate exceeds 150 beats per minute 1
- Avoid combination of AV nodal blocking agents with longer duration of action to prevent profound bradycardia 1
- Caution with pre-excited atrial fibrillation: AV nodal blocking drugs can accelerate ventricular response and cause ventricular fibrillation 2
- Persistent tachycardia risks: Can lead to tachycardia-induced cardiomyopathy if left untreated 2
- Diagnostic accuracy: Automatic analysis systems of 12-lead ECGs are unreliable for arrhythmia diagnosis 1
By following this algorithmic approach, clinicians can effectively manage tachycardia while minimizing risks and optimizing outcomes for patients.