What is the initial approach to managing arrhythmia (irregular heart rhythm)?

Initial Management of Arrhythmia

The initial approach to managing arrhythmia depends critically on hemodynamic stability: unstable patients require immediate synchronized cardioversion or defibrillation, while stable patients allow time for rhythm identification via 12-lead ECG and targeted pharmacologic or electrical therapy based on the specific arrhythmia type. 1, 2

Immediate Assessment

Assess hemodynamic stability first by checking for adverse signs including:

• Systolic blood pressure ≤90 mmHg
• Altered mental status or signs of shock
• Chest pain suggesting myocardial ischemia
• Heart failure symptoms (pulmonary edema, dyspnea)
• Heart rate extremes (typically >150 bpm for tachycardia or <40 bpm for bradycardia) 1, 2

Obtain 12-lead ECG documentation of the rhythm during the arrhythmia episode, though this should not delay cardioversion in hemodynamically unstable patients 2

Hemodynamically Unstable Arrhythmias

For any unstable arrhythmia, perform immediate cardioversion without delay for diagnostic workup 2

Unstable Tachyarrhythmias

• Provide sedation if the patient is conscious before cardioversion 1
• Deliver synchronized DC cardioversion using the following energy levels 3, 1:
  • Atrial fibrillation: 120-200 J biphasic initially, increase stepwise if unsuccessful
  • Atrial flutter/SVT: 50-100 J initially, increase stepwise if unsuccessful
  • Monomorphic VT with pulse: 100 J initially, then 200 J, then 360 J
  • Polymorphic VT or pulseless VT: Treat as VF with unsynchronized high-energy shocks (defibrillation)

Unstable Bradyarrhythmias

• Administer atropine 0.5 mg IV (up to 3 mg total) for bradycardia <40 bpm or bradycardia with signs of cardiac failure 1
• Prepare immediately for temporary cardiac pacing if the patient has 1:
  • Pauses >3 seconds
  • Mobitz type II heart block
  • Type II heart block with anterior MI
  • Previous asystole

Hemodynamically Stable Arrhythmias

Supraventricular Tachycardia (SVT)

For stable narrow complex tachycardia (QRS <120ms), attempt vagal maneuvers first (Valsalva maneuver or unilateral carotid sinus massage if no carotid bruit) 3, 1, 2

If vagal maneuvers fail, administer adenosine 3, 1:

• 6 mg rapid IV push through large vein (antecubital) followed by 20 mL saline flush
• If no conversion in 1-2 minutes, give 12 mg rapid IV push
• Maximum dose: 12 mg
• Must be given in monitored environment (ICU or emergency department) as it can cause transient complete heart block 1
• Contraindicated in asthmatics due to bronchospasm risk 1

If adenosine fails or is contraindicated, use verapamil 5-10 mg IV over 60 seconds 1, but note:

• Contraindicated if β-blockers have been taken (risk of profound bradycardia/hypotension) 1
• Contraindicated in Wolff-Parkinson-White syndrome (may precipitate VT/VF) 1

Stable Ventricular Tachycardia

For stable monomorphic VT, lidocaine is first-line antiarrhythmic 1:

• 50 mg IV over 2 minutes
• Repeat every 5 minutes to total dose of 200 mg
• Maintenance infusion at 2 mg/min 1

If VT is refractory to lidocaine, use amiodarone 1:

• 5 mg/kg (300 mg) IV over one hour for stable patients
• Over 15 minutes in life-threatening situations
• Maintenance infusion at 0.5 mg/min (720 mg/24 hours) 4

For refractory VT not responding to other agents, consider bretylium 5 mg/kg diluted with 100 mL dextrose, with possible further dose of 10 mg/kg 1

Newly Discovered Atrial Fibrillation

The decision between rate control versus rhythm control depends on symptom severity and patient characteristics 3

For asymptomatic or minimally symptomatic AF:

• Accept permanent AF with rate control and antithrombotic therapy
• Avoid antiarrhythmic drugs if potential toxicity outweighs benefit (e.g., older patients without thromboembolism risk factors with readily controlled ventricular rate) 3

For symptomatic AF requiring rhythm control:

• Ensure adequate anticoagulation and rate control before cardioversion 3
• For AF >3 months duration, consider initiating antiarrhythmic medication before cardioversion to reduce early recurrence (brief therapy, e.g., 1 month) 3

Drug selection for rhythm control in recurrent paroxysmal AF is based on underlying cardiac structure 3:

• No/minimal structural heart disease: Flecainide, propafenone, or sotalol as first-line (well tolerated, minimal extracardiac toxicity) 3
• Heart failure: Amiodarone or dofetilide (safety data support these agents) 3
• Ischemic heart disease without HF: Sotalol first-line (beta-blocking activity plus antiarrhythmic efficacy); amiodarone and dofetilide as secondary agents 3
• Hypertension without LV hypertrophy: Flecainide or propafenone first-line (don't prolong QT); amiodarone, dofetilide, or sotalol as secondary choices 3
• LV hypertrophy (wall thickness ≥1.4 cm): Amiodarone first-line (relative safety compared to other agents that may cause torsades de pointes) 3

Critical Considerations

Restore atrioventricular synchrony promptly in hemodynamically unstable patients, as rhythm disturbances significantly impact cardiac output and systemic perfusion 3

Correct underlying precipitants including electrolyte abnormalities (particularly potassium and magnesium), hypoxia, acid-base disturbances, and acute illness 3, 1

Assess thromboembolism risk in AF patients using CHA2DS2-VASc score to guide anticoagulation decisions 3

For pre-excited AF (Wolff-Parkinson-White syndrome):

• Immediate DC cardioversion if hemodynamically compromised 3
• Use IV procainamide or ibutilide if stable 3
• Never use AV nodal blockers (amiodarone, adenosine, digoxin, calcium channel blockers) as they accelerate ventricular rate and are potentially harmful 3

Administer all IV drugs via large vein followed by 20 mL saline bolus to aid delivery to central circulation 1

Use volumetric infusion pumps for amiodarone administration (not drop counters, which may underdose by up to 30%) and administer through central venous catheter when possible 4