What is the approach to rhythm analysis and management of arrhythmias?

Approach to Rhythm Analysis and Management of Arrhythmias

The systematic approach to rhythm analysis and management of arrhythmias requires a structured diagnostic evaluation with a 12-lead ECG during tachycardia, followed by appropriate treatment based on the specific arrhythmia mechanism identified. 1

Diagnostic Evaluation

Initial Assessment

• Obtain a 12-lead ECG during tachycardia whenever possible (without delaying treatment if hemodynamically unstable)
• At minimum, obtain a monitor strip from the defibrillator before cardioversion 1
• Use the RIRI approach (Rate, Intervals, Rhythm, Ischemia/infarction) for systematic ECG interpretation 2

Narrow QRS Complex Tachycardia (<120 ms)

• Almost always supraventricular in origin
• Differential diagnosis based on mechanism:
  • No visible P waves with regular RR intervals: Likely AVNRT (may have pseudo-R wave in V1 or pseudo-S wave in inferior leads)
  • P wave in ST segment (70 ms after QRS): Likely AVRT
  • RP interval longer than PR: Consider atypical AVNRT, PJRT, or atrial tachycardia 1
• Adenosine or carotid massage responses can aid diagnosis (record 12-lead ECG during these maneuvers)

Wide QRS Complex Tachycardia (>120 ms)

• Critical to differentiate between SVT and ventricular tachycardia (VT)
• If diagnosis cannot be confirmed, treat as VT 1
• Three main categories:
  1. SVT with bundle branch block/aberration
  2. SVT with AV conduction over accessory pathway
  3. Ventricular tachycardia

Additional Diagnostic Tools

• Ambulatory 24-hour Holter monitoring: For frequent (several episodes/week) transient tachycardias
• Event/wearable loop recorder: More useful for less frequent arrhythmias
• Implantable loop recorders: For rare symptoms (<2 episodes/month) with severe hemodynamic instability
• Exercise testing: If arrhythmia is triggered by exertion
• Echocardiography: To exclude structural heart disease 1

Management Approach

For Undocumented Arrhythmias

1. If normal ECG with symptoms of premature beats:

   • Identify and eliminate triggers (caffeine, alcohol, nicotine, recreational drugs)
   • Note that benign extrasystoles often occur at rest and decrease with exercise 1

2. For suspected paroxysmal arrhythmias:

   • Teach patients vagal maneuvers
   • Consider beta-blockers empirically (if no significant bradycardia <50 bpm)
   • Do not initiate Class I or III antiarrhythmic drugs without documented arrhythmia due to proarrhythmic risk 1, 3

For Documented Supraventricular Arrhythmias

1. Patients with pre-excitation on resting ECG and paroxysmal palpitations:

   • Presumptive diagnosis of AVRT
   • Refer to arrhythmia specialist 1

2. Patients with pre-excitation and irregular paroxysmal palpitations:

   • Suggests atrial fibrillation
   • Requires immediate electrophysiological evaluation due to risk of sudden death 1

3. For narrow complex tachycardias:

   • Refer if drug-resistant/intolerant or patient desires freedom from drug therapy 1

For Ventricular Arrhythmias

1. First-line therapy:

   • Beta-blockers for chronic ventricular arrhythmias in both structurally normal hearts and most cardiomyopathies 4
   • Particularly effective for VT related to myocardial ischemia

2. Second-line therapy:

   • Consider antiarrhythmic medications if beta-blockers ineffective/not tolerated
   • Consider catheter ablation for refractory cases 4
   • Amiodarone for persistent symptomatic VT (with careful monitoring)

3. For VT storm (life-threatening condition):

   • Correct reversible causes (electrolytes, acid-base disturbances, ischemia)
   • Maintain potassium >4.0 mEq/L and magnesium >2.0 mg/dL
   • Consider electrical cardioversion if pharmacological management fails 4

Indications for Specialist Referral

• Wide complex tachycardia of unknown origin
• Wolff-Parkinson-White syndrome (pre-excitation with arrhythmias)
• Severe symptoms during palpitations (syncope, dyspnea)
• Drug-resistant or drug-intolerant narrow complex tachycardias
• Patients desiring to be free of drug therapy 1

Special Considerations

Proarrhythmic Effects of Medications

• Antiarrhythmic drugs can cause new or worsened arrhythmias
• Flecainide can cause ventricular proarrhythmic effects ranging from increased PVCs to more severe ventricular tachycardia
• Risk appears related to dose and underlying cardiac disease
• Higher risk in patients with sustained VT, CHF, low ejection fraction, history of MI 3

Digoxin Toxicity

• Can cause both bradyarrhythmias and ventricular arrhythmias
• Treatment depends on manifestation:
  • For bradyarrhythmias: Consider DIGIBIND, atropine, or temporary pacing
  • For ventricular arrhythmias: Correct electrolyte disorders (especially hypokalemia)
  • For life-threatening toxicity: DIGIBIND and activated charcoal 5

Pitfalls to Avoid

• Relying on automatic analysis systems of 12-lead ECGs (commonly suggest incorrect diagnoses) 1
• Administering verapamil or diltiazem for wide complex tachycardia before confirming SVT (may cause hemodynamic collapse if VT) 1
• Initiating antiarrhythmic drugs without documented arrhythmia (risk of proarrhythmia) 1, 3
• Assuming stable vital signs differentiate SVT from VT (not reliable) 1
• Missing pre-excitation patterns that indicate high-risk conditions like WPW syndrome 1