What are the treatment options for arrhythmias, specifically the use of antiarrhythmic (antiarrhythmic) medications?

Antiarrhythmic Medications for Arrhythmia Treatment

Beta-blockers are the first-line antiarrhythmic therapy for most arrhythmias, as they are effective, generally safe, and the only class proven to reduce sudden cardiac death and improve survival. 1

Treatment Algorithm by Arrhythmia Type

Ventricular Arrhythmias

For symptomatic premature ventricular contractions (PVCs) and ventricular tachycardia (VT) in structurally normal hearts:

• Start with beta-blockers or non-dihydropyridine calcium channel blockers (diltiazem, verapamil) as first-line therapy to reduce symptoms and arrhythmia burden 1
• If beta-blockers and calcium channel blockers are ineffective or not tolerated, escalate to Class IC agents (flecainide, propafenone) or sotalol for rhythm control 1
• Avoid Class I antiarrhythmics when possible due to concerns for adverse effects and proarrhythmic risk 1

For ventricular arrhythmias with structural heart disease or heart failure:

• Beta-blockers remain first-line and are the only antiarrhythmics proven to reduce mortality in post-myocardial infarction and heart failure patients 1
• Amiodarone or dofetilide are the preferred antiarrhythmics when additional rhythm control is needed, as they have demonstrated neutral effects on survival in controlled trials 1, 2
• Avoid Class IC agents (flecainide, propafenone) entirely in patients with structural heart disease due to increased mortality risk 1

Critical caveat for beta-blockers: In acute STEMI/NSTEMI patients with ≥2 shock risk factors (age >70 years, heart rate >110 bpm, systolic BP <120 mmHg), beta-blockers significantly increase risk of shock and death 1

Atrial Fibrillation (AF)

For rate control in new-onset AF:

• Beta-blockers are first-line for rate control in hemodynamically stable patients 3
• Non-dihydropyridine calcium channel blockers (diltiazem, verapamil) are alternatives for rate control 1, 3
• Digoxin should not be used as monotherapy in active patients, as it only controls rate at rest and is ineffective during exercise 3
• For patients with left ventricular ejection fraction (LVEF) ≤40%, use beta-blockers and/or digoxin, avoiding calcium channel blockers 3

For rhythm control and maintenance of sinus rhythm:

In patients WITHOUT structural heart disease:

• Flecainide, propafenone, or sotalol are first-line choices for maintaining sinus rhythm 1, 4, 5, 2
• These agents are well-tolerated with relatively low toxicity risk 1
• Amiodarone and dofetilide are second-line options when first-line agents fail 1
• Amiodarone is not appropriate as initial therapy in healthy patients due to significant organ toxicity risks 3, 6

In patients WITH structural heart disease (coronary artery disease, hypertension with left ventricular hypertrophy):

• Sotalol is preferred initially unless heart failure is present 1
• Amiodarone or dofetilide are secondary choices 1

In patients WITH heart failure:

• Amiodarone or dofetilide are the only safe options for rhythm control 1, 2, 7
• All other antiarrhythmics carry unacceptable risks in this population 1

Supraventricular Tachycardia (SVT)

For acute termination of AV nodal reentrant tachycardia:

• Adenosine is the drug of choice, given as rapid IV bolus: 3 mg initially, then 6 mg, then 12 mg maximum 1
• Adenosine has an extremely short half-life and selectively blocks AV nodal conduction 1
• Contraindicated in asthmatics due to bronchospasm risk 1
• Must be given in monitored environment as it can cause transient complete heart block 1

For chronic suppression:

• Propafenone is indicated for paroxysmal supraventricular tachycardia with disabling symptoms 4

Ventricular Tachycardia with Hemodynamic Compromise

For sustained VT causing hemodynamic instability:

• Lignocaine (lidocaine) is first-choice: 1-3 mg/kg IV bolus (100 mg for cardiac arrest), may repeat after 5-10 minutes 1
• Maintain with 2-4 mg/min infusion if successful 1
• Amiodarone is second-line: 5 mg/kg (300 mg) over 1 hour, or over 15 minutes in life-threatening situations 1
• Bretylium (5-10 mg/kg) for refractory VT unresponsive to other agents, but antiarrhythmic effect may take 20 minutes 1

Critical Safety Considerations

Proarrhythmic risks:

• All antiarrhythmics except beta-blockers can worsen the index arrhythmia 2, 8
• Class IC agents (flecainide, propafenone) are absolutely contraindicated in structural heart disease 1, 5
• QT prolongation and torsades de pointes risk with amiodarone, sotalol, and dofetilide 6

Drug interactions with amiodarone:

• Increases warfarin effect by 100% within 3-4 days; reduce warfarin dose by one-third to one-half 6
• Increases digoxin levels by 70% after one day; reduce digoxin dose by 50% or discontinue 6
• Increases quinidine levels by 33% and procainamide by 55%; reduce doses by one-third 6
• Grapefruit juice increases amiodarone levels by 50% and should be avoided 6

Electrolyte management:

• Maintain potassium >4.5 mmol/L before cardioversion or when using antiarrhythmics 1
• Correct hypokalemia and hypomagnesemia to prevent proarrhythmia 1

Contraindications:

• Cardioversion is contraindicated in digitalis toxicity due to risk of refractory ventricular arrhythmias 1
• Assess for sinus node dysfunction before cardioversion in long-standing AF 1

Monitoring Requirements

• Amiodarone requires close monitoring for organ toxicity with long-term use due to 100-day half-life 1, 6
• Flecainide has 12-27 hour half-life; overdose supportive treatments may need extended duration 5
• Dofetilide requires in-hospital initiation with continuous monitoring 1, 2