What is the approach to managing a patient with tachycardia?

Approach to Tachycardia

Immediate Assessment: Stability Determines Everything

If the patient is hemodynamically unstable (altered mental status, ischemic chest pain, acute heart failure, hypotension, or shock), proceed immediately to synchronized cardioversion without delay for pharmacologic therapy or additional diagnostic workup. 1, 2

• Hemodynamic instability is the single most critical decision point—cardioversion takes priority over all other interventions 1
• For rates <150 bpm without ventricular dysfunction, the tachycardia is more likely secondary to an underlying condition rather than the primary cause of instability 1

Initial Stabilization Steps (For Stable Patients)

Assess oxygenation first, provide supplementary oxygen if needed, attach cardiac monitor, establish IV access, and obtain a 12-lead ECG during tachycardia whenever possible—but do not delay treatment if the patient becomes unstable. 1, 2

• Check and correct potassium, magnesium, and calcium immediately, as electrolyte disorders commonly precipitate tachyarrhythmias 2, 3
• Hypoxemia is a common cause of tachycardia—look for increased work of breathing (tachypnea, retractions, paradoxical abdominal breathing) 1

Classification: Narrow vs. Wide Complex

For Narrow QRS Complex Tachycardia (QRS <120 ms)

Begin with vagal maneuvers (Valsalva, carotid massage, facial immersion in cold water) in the supine position as first-line intervention for regular narrow complex tachycardia. 1, 2

• If vagal maneuvers fail, adenosine is the first-line pharmacological therapy 1, 2

  • First dose: 6 mg rapid IV push followed by NS flush 1
  • Second dose: 12 mg if required 1
  • Avoid in severe asthma; use with caution in patients on theophylline (may require higher doses) or dipyridamole (potentiates effect) 1

• Alternative agents include IV calcium channel blockers (verapamil, diltiazem) or beta-blockers if adenosine is contraindicated 1

For Wide QRS Complex Tachycardia (QRS ≥120 ms)

Assume all wide complex tachycardia is ventricular tachycardia (VT) until proven otherwise—misdiagnosis can be fatal if treated as supraventricular tachycardia (SVT). 3

Diagnostic Clues Favoring VT:

• QRS width >140 ms with RBBB pattern or >160 ms with LBBB pattern 1
• RS interval >100 ms in any precordial lead 1
• Negative concordance in precordial leads (diagnostic for VT) 1
• Presence of ventricular fusion beats (diagnostic for VT) 1
• QR complexes indicating myocardial scar 1
• History of previous myocardial infarction strongly suggests VT 1

Treatment for Stable Monomorphic VT:

For patients without severe heart failure or acute MI, IV procainamide is the preferred first-line agent. 2, 3

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

For patients with impaired left ventricular function, severe heart failure, or acute MI, amiodarone 150 mg IV over 10 minutes is the preferred agent. 2, 3, 4

• Follow with maintenance infusion of 1 mg/min for first 6 hours 1
• Amiodarone has a better safety profile in structural heart disease but is less ideal for early conversion compared to procainamide 3

IV adenosine may be considered for undifferentiated regular stable wide complex tachycardia as it is relatively safe and can help diagnose the underlying rhythm. 2, 3

• If the rhythm terminates with adenosine, this suggests SVT with aberrancy rather than VT 3
• Use with extreme caution: may produce VF in patients with coronary artery disease and AF with rapid ventricular rate in pre-excited tachycardias 1

Critical Pitfalls to Avoid

Never use calcium channel blockers (verapamil, diltiazem) for wide complex tachycardia of unknown origin—they can cause hemodynamic collapse if the rhythm is VT. 3

• Do not use concomitant IV calcium channel blockers and beta-blockers due to potentiation of hypotensive and bradycardic effects 3
• Do not delay cardioversion in unstable patients to attempt pharmacologic conversion or obtain additional diagnostic studies 2, 3

Special Situations

Sinus Tachycardia

No specific drug treatment is required for sinus tachycardia—instead, identify and treat the underlying physiologic stimulus (fever, anemia, hypotension, dehydration). 1

• Upper rate of sinus tachycardia is age-related (approximately 220 minus patient's age in years) 1

Polymorphic VT with Long QT (Torsades de Pointes)

IV magnesium is the primary treatment for torsades de pointes. 3

• Consider overdrive pacing or IV isoproterenol for polymorphic VT accompanied by bradycardia or pauses 3

Pre-excited Tachycardias (Wolff-Parkinson-White)

Immediate referral to an arrhythmia specialist is warranted, as ablation is potentially curative. 1, 2, 5

• Irregular palpitations with baseline pre-excitation strongly suggest AF, which requires immediate electrophysiological evaluation due to risk of sudden death 1

Post-Stabilization Management

All patients with documented wide complex tachycardia require ICU/CCU admission and immediate cardiology/electrophysiology consultation. 2, 3

All patients with wide complex tachycardia of unknown origin should be referred to an arrhythmia specialist for consideration of electrophysiology study and possible catheter ablation. 2, 3

• Patients with narrow complex tachycardias and drug resistance, intolerance, or desire to be free of drug therapy should also be referred 1, 2
• Catheter ablation should be considered for refractory sustained monomorphic VT 2