What is the management of arrhythmias?

Management of Arrhythmias

Immediate Assessment and Stabilization

Hemodynamic stability dictates the urgency and type of intervention—unstable arrhythmias require immediate electrical cardioversion regardless of mechanism, while stable arrhythmias allow time for diagnostic evaluation and pharmacologic management. 1

Critical First Steps

• Continuous ECG monitoring and intravenous access are mandatory for all patients presenting with any cardiac arrhythmia 2
• Obtain a 12-lead ECG during tachycardia whenever possible, but do not delay cardioversion in hemodynamically unstable patients 1
• At minimum, capture a monitor strip before direct current cardioversion, even in cardiogenic shock or cardiac arrest 1

Hemodynamic Instability Indicators

• Loss of consciousness or altered mental status 1, 2
• Hypotension or cardiogenic shock 1
• Acute heart failure or pulmonary edema 1
• Ongoing chest pain refractory to medical therapy 2

Management Based on Hemodynamic Status

Hemodynamically Unstable Arrhythmias

Immediate synchronized cardioversion is the treatment of choice for any arrhythmia—supraventricular or ventricular—causing hemodynamic compromise, syncope, or refractory angina. 1, 2

Cardioversion Protocol

• Supraventricular tachycardias: Start with 50-100 J biphasic energy 1, 2
• Ventricular arrhythmias in acute heart failure: Perform early cardioversion rather than attempting pharmacologic termination 1, 2
• Synchronized mode for organized rhythms; unsynchronized (defibrillation) for ventricular fibrillation 1

Post-Cardioversion Management

• Amiodarone may be considered to prevent recurrent supraventricular arrhythmias with hemodynamic compromise after urgent electrical cardioversion 2
• Correct underlying precipitants: electrolyte abnormalities (especially potassium and magnesium), hypoxia, ischemia, and catecholamine excess 1, 3

Hemodynamically Stable Arrhythmias

Narrow QRS Complex Tachycardia (QRS <120 ms)

If the QRS is narrow and regular without visible P waves, AVNRT is the most likely mechanism; if P waves are visible in the ST segment separated from QRS by >70 ms, AVRT is most likely. 1

Acute Management Options

• Vagal maneuvers should be attempted first (Valsalva, carotid massage) 1
• Adenosine 6-12 mg rapid IV bolus can be considered for selected cases of supraventricular reentrant tachycardia 2
  • Record 12-lead ECG during adenosine administration to aid diagnosis 1
  • Contraindicated in pre-excited atrial fibrillation (Wolff-Parkinson-White with AF) 1

Pharmacologic Rate Control

• For atrial fibrillation or flutter with hemodynamic compromise, intravenous amiodarone is more effective for rate control and may restore sinus rhythm 1, 2
• Verapamil may suppress AV node-dependent reentrant SVTs, but use cautiously due to negative inotropic effects 1, 2
  • Avoid in heart failure or severe left ventricular dysfunction 1

Wide QRS Complex Tachycardia (QRS ≥120 ms)

Distinguishing ventricular tachycardia from supraventricular tachycardia with aberrancy is critical, as management differs significantly. 1

Key Diagnostic Considerations

• Patients with advanced myocardial disease often have intraventricular conduction delays, making SVT vs VT distinction challenging 1
• When in doubt, treat as ventricular tachycardia—assume VT until proven otherwise 1
• Right bundle branch block configuration does not reliably distinguish VT from SVT, especially in congenital heart disease 1

Management of Stable Ventricular Tachycardia

• Amiodarone is preferred for longer-term administration and is generally well tolerated hemodynamically 1
• Beta-blockers are first-line therapy for management of ventricular arrhythmias and prevention of sudden cardiac death 1
  • Exception: Avoid in patients with ≥2 shock risk factors (age >70, HR >110, SBP <120 mmHg) 1

Specific Arrhythmia Management

Atrial Fibrillation/Flutter in Heart Failure

In acute heart failure, atrial fibrillation or flutter may cause hemodynamic decompensation requiring aggressive therapy. 1

• Vagotonic measures rarely work in acute heart failure 1
• Poorly tolerated SVT should be treated with synchronous cardioversion at 50-100 J biphasic 1, 2
• Intravenous amiodarone, alone or with electrical cardioversion, is effective for rate control and achieving cardioversion 1

Nonsustained Ventricular Tachycardia (NSVT)

Asymptomatic NSVT should not be treated with antiarrhythmic medication, as there is no evidence that suppression improves prognosis in heart failure patients. 1

• NSVT occurs in 30-80% of chronic heart failure patients on 24-hour monitoring 1
• If NSVT causes symptoms requiring therapy, amiodarone is the safest agent 1, 2

Drug-Induced Arrhythmias

When drug-induced arrhythmias are suspected, withdraw the offending agent immediately and exclude other arrhythmogenic substrates. 1, 4

High-Risk Medications

• QT-prolonging drugs: Antiarrhythmics (sotalol, quinidine), antibiotics (quinolones, macrolides), antipsychotics, methadone 1, 4
• Sodium channel blockers: Should not be used in patients with prior myocardial infarction or sustained VT 1
• Bradyarrhythmia-inducing drugs: Digoxin, beta-blockers, calcium channel blockers (verapamil, diltiazem) 1, 5

Management of Torsades de Pointes

• Discontinue offending drug and correct electrolyte abnormalities (maintain K+ >4.5 mEq/L, Mg2+ >2 mg/dL) 1
• Intravenous magnesium and temporary pacing are useful 1
• Isoproterenol can increase heart rate and shorten action potential duration 1

Critical Drug Interactions with Amiodarone

Amiodarone inhibits CYP3A4, CYP2C9, CYP2D6, CYP1A2, and p-glycoprotein, resulting in numerous clinically significant drug interactions. 5

Essential Dose Adjustments

• Digoxin: Reduce dose by 50% and monitor levels closely (amiodarone increases digoxin levels by 70%) 5
• Warfarin: Reduce dose by one-third to one-half (amiodarone increases INR by 100% after 3-4 days) 5
• Quinidine/Procainamide: Reduce dose by one-third 5
• Flecainide: Adjust dose downward when co-administered 5

Contraindicated Combinations

• Avoid grapefruit juice (increases amiodarone AUC by 50% and Cmax by 84%) 5
• Exercise caution with beta-blockers and calcium channel blockers due to potentiation of bradycardia, sinus arrest, and AV block 5

Long-Term Management Considerations

When Antiarrhythmic Drugs Are Insufficient

Catheter ablation may be appropriate adjunctive therapy in selected patients with recurrent arrhythmias. 1

• Success rates vary by arrhythmia type and underlying cardiac anatomy 1
• Particularly challenging in congenital heart disease and post-surgical patients 1
• Should be performed at experienced centers with advanced three-dimensional mapping equipment 1

ICD Therapy Indications

ICD therapy is indicated for secondary prevention in patients with prior cardiac arrest or sustained VT, and for primary prevention in selected high-risk patients with reduced ejection fraction. 1

• Amiodarone, sotalol, and/or beta-blockers may be considered as pharmacologic alternatives when ICD therapy is not feasible 1
• Combination therapy should be reserved for life-threatening ventricular arrhythmias incompletely responsive to single agents 5

Common Pitfalls to Avoid

• Never initiate Class I or III antiarrhythmics without documented arrhythmia due to proarrhythmic risk 1
• Do not use sodium channel blockers in patients with prior MI or LV hypertrophy >1.4 cm 1
• Avoid treating asymptomatic premature beats or NSVT with antiarrhythmics—address precipitating factors instead (caffeine, alcohol, nicotine, hyperthyroidism) 1
• When adding antiarrhythmics to amiodarone, start at half the usual recommended dose 5
• Distinguish between benign extrasystoles (worse at rest, improve with exercise) and pathologic arrhythmias 1