What is the approach to managing tachyarrhythmias in patients?

Approach to Tachyarrhythmias

Initial Assessment: Hemodynamic Stability Determines Everything

If the patient is hemodynamically unstable (hypotensive, altered mental status, chest pain, signs of shock or acute heart failure), proceed immediately to synchronized cardioversion without delay for pharmacologic therapy or additional diagnostic workup. 1, 2, 3

• Obtain at minimum a monitor strip before cardioversion, even in cardiac arrest, but do not delay treatment 1
• Sedation with etomidate 0.2-0.3 mg/kg IV may be used for conscious patients 3
• For in-hospital cardiac arrest, immediate defibrillation at maximum output is preferred over CPR first, as sustained ventricular tachyarrhythmia is more likely 1

Classification by QRS Width: The Critical First Decision

Narrow QRS Complex (<120 ms): Almost Always Supraventricular

For hemodynamically stable narrow QRS tachycardia, begin with vagal maneuvers in the supine position as first-line intervention. 1, 2

• If vagal maneuvers fail, adenosine is the first-line pharmacological therapy 1, 2
• Obtain a 12-lead ECG during adenosine administration or carotid massage to aid diagnosis 1
• If no P waves are visible and RR interval is regular, AVNRT is most likely; if P wave is present in ST segment separated from QRS by >70 ms, AVRT is most likely 1

Critical pitfall: Never use AV nodal blocking agents (calcium channel blockers, beta-blockers, adenosine) if pre-excitation is suspected, as they may accelerate ventricular response and cause hemodynamic collapse 2, 3

• For irregular narrow QRS tachycardia suggesting pre-excited atrial fibrillation, proceed directly to synchronized cardioversion 1, 2
• Avoid concomitant IV calcium channel blockers and beta-blockers due to potentiation of hypotensive and bradycardic effects 2

Wide QRS Complex (≥120 ms): Assume Ventricular Tachycardia Until Proven Otherwise

Any wide QRS tachycardia should be presumed to be ventricular tachycardia if the diagnosis is unclear, as misdiagnosis can be fatal if treated as SVT. 2, 3

For Stable Monomorphic VT:

IV procainamide is the preferred first-line agent for stable monomorphic VT in patients without severe heart failure or acute MI. 1, 2, 3

• Procainamide is more effective than amiodarone for early slowing and termination of VT 3
• Monitor blood pressure closely during infusion, particularly if any degree of heart failure is present 3

Amiodarone 150 mg IV over 10 minutes is the preferred agent if there is any concern for impaired left ventricular function, severe heart failure, or acute MI. 1, 2, 3, 4

• Amiodarone has a better safety profile in structural heart disease but is less ideal for early conversion 3
• Most patients require 48-96 hours of IV amiodarone therapy until ventricular arrhythmias are stabilized 4

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
• Avoid adenosine in severe asthma; it may precipitate atrial fibrillation in 1-15% of cases 3

For Polymorphic VT (Torsades de Pointes):

IV magnesium is the primary treatment for polymorphic VT with long QT syndrome. 2, 3

• Overdrive pacing or IV isoproterenol may be considered if accompanied by bradycardia or pauses 2, 3
• IV beta-blockers may be effective for ischemic VT or catecholaminergic VT 2, 3

Absolute contraindication: Calcium channel blockers (verapamil, diltiazem) are absolutely contraindicated for wide complex tachycardia of unknown origin, as they can cause hemodynamic collapse if the rhythm is VT 3

Essential Diagnostic Workup for Stable Patients

Obtain a 12-lead ECG immediately during tachycardia whenever possible, but do not delay treatment if hemodynamically unstable. 1, 2

• Look for evidence of prior MI, QRS width >140ms with RBBB or >160ms with LBBB, and pre-excitation pattern 5
• Check and correct potassium, magnesium, and calcium immediately, as electrolyte disorders commonly precipitate tachyarrhythmias 2, 5, 3

For patients with documented sustained SVT, echocardiography should be performed to exclude structural heart disease. 1

• Ambulatory 24-hour Holter recording is useful for frequent (several episodes per week) transient tachycardias 1
• Event or wearable loop recorders are more useful for less frequent arrhythmias 1
• Implantable loop recorders may be helpful for rare symptoms (<2 episodes per month) with severe hemodynamic instability 1

Special Populations and Referral Indications

All patients with wide complex tachycardia of unknown origin should be referred to an arrhythmia specialist after successful termination. 1, 2, 3

Immediate referral to an arrhythmia specialist is mandatory for:

• Any wide complex tachycardia of unknown origin 1
• Wolff-Parkinson-White syndrome (pre-excitation with arrhythmias) due to potential for lethal arrhythmias 1
• Narrow complex tachycardias with drug resistance or intolerance 1
• Severe symptoms (syncope, dyspnea) during palpitations 1

Management Without ECG Documentation

If symptoms suggest arrhythmia but no ECG documentation exists, eliminate precipitating factors first: excessive caffeine, alcohol, nicotine, recreational drugs, and screen for hyperthyroidism. 1

• Teach patients to perform vagal maneuvers 1
• Beta-blockers may be prescribed empirically if significant bradycardia (<50 bpm) has been excluded 1

Critical pitfall: Do not initiate class I or class III antiarrhythmic drugs without documented arrhythmia due to risk of proarrhythmia 1

Post-Stabilization Management

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

• Consider electrophysiology study and possible catheter ablation once stabilized 2, 3
• Invasive electrophysiological investigation with subsequent catheter ablation may be used for diagnosis and therapy in cases with clear history of paroxysmal regular palpitations 1
• Urgent catheter ablation is recommended for refractory sustained monomorphic VT 1