What is the recommended evaluation and management of tachyarrhythmias in stable versus unstable patients?

Evaluation and Management of Tachyarrhythmias

Immediate Assessment: Determine Hemodynamic Stability

The first and most critical decision is whether the patient is hemodynamically unstable—if yes, proceed immediately to synchronized cardioversion without delay for additional workup or pharmacologic therapy. 1, 2

Signs of Instability (Rate-Related)

• Acute altered mental status 1
• Ischemic chest discomfort 1
• Acute heart failure 1
• Hypotension or signs of shock 1, 2
• Note: With rates <150 bpm and no ventricular dysfunction, instability is more likely secondary to an underlying condition rather than the tachycardia itself 1

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Management of UNSTABLE Tachyarrhythmias

Immediate Synchronized Cardioversion

• Perform synchronized cardioversion immediately for any hemodynamically unstable tachycardia 1, 2
• Deliver at maximum output initially 3
• Establish IV access and administer sedation if the patient is conscious, but do not delay cardioversion if the patient is extremely unstable 1
• If rhythm deteriorates to ventricular fibrillation or polymorphic VT, switch to unsynchronized defibrillation 3

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Management of STABLE Tachyarrhythmias

Initial Steps for All Stable Patients

• Provide supplementary oxygen if hypoxemic or increased work of breathing 1
• Attach cardiac monitor, evaluate blood pressure, establish IV access 1
• Obtain 12-lead ECG immediately during tachycardia to characterize rhythm, but do not delay treatment if patient becomes unstable 1, 2
• Check and correct potassium, magnesium, and calcium immediately, as electrolyte disorders commonly precipitate tachyarrhythmias 4, 2, 3

Narrow QRS Complex Tachycardia (QRS <120 ms)

First-Line: Vagal Maneuvers

• Perform vagal maneuvers with patient in supine position as first-line intervention 1, 2
• Valsalva maneuver: bear down against closed glottis for 10-30 seconds (equivalent to 30-40 mm Hg) 1
• Carotid massage: apply steady pressure over carotid sinus for 5-10 seconds after confirming absence of bruit 1
• Ice-cold wet towel to face (diving reflex) 1
• Success rate approximately 27.7% with vagal maneuvers 1

Second-Line: Adenosine

• Adenosine is the first-line pharmacologic agent for narrow complex tachycardia 1, 2, 3
• Dose: 6 mg rapid IV push, followed by 12 mg if needed 3
• Terminates AVNRT in approximately 95% of patients 1
• Record ECG during administration—response aids diagnosis even if arrhythmia doesn't terminate 1
• Avoid adenosine in severe bronchial asthma 1
• Potential adverse effect: transient AF in 1-15% of patients 1

Alternative Agents (If Adenosine Fails or Contraindicated)

• IV diltiazem or verapamil are reasonable alternatives for hemodynamically stable patients 1
• IV beta blockers (e.g., esmolol, metoprolol) are reasonable but less effective than calcium channel blockers 1
• Critical: Ensure absence of VT or pre-excited AF before giving calcium channel blockers or beta blockers, as these can cause hemodynamic collapse 1, 3

If Pharmacologic Therapy Fails

• Synchronized cardioversion is recommended when drugs fail to terminate tachycardia or are contraindicated 1

Wide QRS Complex Tachycardia (QRS ≥120 ms)

Critical Principle: Assume Ventricular Tachycardia Until Proven Otherwise

• When VT cannot be definitively distinguished from SVT with aberrancy, treat as VT 3
• Never use verapamil, diltiazem, or other AV-nodal blockers for wide complex tachycardia of uncertain etiology—these can precipitate hemodynamic collapse 2, 3

Stable Monomorphic Wide Complex Tachycardia

For patients WITHOUT severe heart failure or acute MI:

• Procainamide is the first-line agent: up to 10 mg/kg IV at 50-100 mg/min over 10-20 minutes 1, 2, 3, 5
• Procainamide demonstrates the greatest efficacy among antiarrhythmic options 3, 5
• Monitor blood pressure and ECG during infusion 5

For patients WITH severe heart failure, acute MI, or impaired LV function:

• Amiodarone is the preferred agent: 150 mg IV over 10 minutes, repeat as needed 1, 2, 3
• Amiodarone is safer than procainamide in patients with structural heart disease 1

Alternative agent:

• Sotalol 1.5 mg/kg IV over 5 minutes may be considered, but avoid if QT interval is prolonged 1, 3

Irregular Wide Complex Tachycardia (Pre-excited AF)

• DC cardioversion is recommended 1
• If hemodynamically stable, IV ibutilide or flecainide is appropriate 1

Polymorphic VT

• With prolonged QT: IV magnesium as first-line therapy; consider pacing or IV isoproterenol if bradycardia or pause-dependent triggers present 3
• With normal QT: IV beta-blockers (for ischemic or catecholaminergic VT) or isoproterenol may be effective 3
• Immediate cardioversion required if hemodynamically unstable 3

Sinus Tachycardia

• No specific drug treatment required—therapy directed toward identification and treatment of underlying cause 1
• Common causes: fever, hypovolemia, anemia, hypoxia, hyperthyroidism, drugs (stimulants, caffeine, cocaine) 1
• Do not "normalize" heart rate in compensatory tachycardia with poor cardiac function, as cardiac output may be rate-dependent 1

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Critical Pitfalls to Avoid

• Never delay cardioversion in unstable patients to attempt pharmacologic conversion 2, 3
• Never use calcium channel blockers or adenosine for wide complex tachycardia unless definitively proven to be SVT 1, 2, 3
• Never combine antiarrhythmic agents (especially amiodarone and procainamide) due to additive toxicity 3
• Never use adenosine for irregular or polymorphic wide complex tachycardia—can trigger ventricular fibrillation 3
• Use extreme care with concomitant IV calcium channel blockers and beta blockers due to potentiation of hypotensive/bradycardic effects 1

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Post-Conversion Management and Disposition

Immediate Post-Conversion

• Maintain continuous cardiac monitoring for recurrence 3
• If tachycardia recurs despite initial termination, consider IV amiodarone to prevent further episodes 3

Referral and Follow-up

• All patients with wide complex tachycardia of unknown origin require referral to an arrhythmia specialist 1, 2
• All patients with documented NSVT or sustained VT require cardiology/electrophysiology consultation 4
• Patients with WPW syndrome (pre-excitation and arrhythmias) should be referred for further evaluation 1
• Referral indicated for drug resistance, intolerance, or patients desiring freedom from lifelong drug therapy 1
• Urgent catheter ablation recommended for scar-related heart disease with incessant VT or electrical storm 3

Admission Criteria

• All patients with documented wide complex tachycardia require ICU/CCU admission 2
• Recurrent episodes or structural heart disease 4
• Single brief episode in structurally normal heart may be managed as outpatient with appropriate cardiology follow-up 4