How do you manage short RP versus long RP tachycardia?

Management of Short RP versus Long RP Tachycardia

The management of short RP versus long RP tachycardias should follow a structured approach based on the specific mechanism, with vagal maneuvers and adenosine as first-line treatments for acute termination, followed by mechanism-specific therapies including catheter ablation for recurrent cases. 1

Understanding Short RP vs Long RP Tachycardias

Definitions and Mechanisms

• Short RP tachycardias: P wave is closer to the preceding QRS complex than the subsequent QRS complex

  • Typical AVNRT (most common): P wave appears at the end of QRS complex as a pseudo S wave in inferior leads and pseudo R' in V1 1
  • Orthodromic AVRT: P wave visible in early part of ST-T segment 1
  • RP interval < 90 ms on surface ECG 1

• Long RP tachycardias: P wave is closer to the subsequent QRS complex

  • Atrial tachycardia (AT): P wave morphology differs from sinus rhythm, usually seen near end of T wave 1
  • Atypical AVNRT ("fast-slow"): uncommon variant 1
  • Permanent form of junctional reciprocating tachycardia (PJRT): uses accessory pathway with decremental retrograde conduction 1

Diagnostic Approach

1. Obtain 12-lead ECG during tachycardia to determine:

   • Regularity of ventricular rate
   • Presence and location of P waves relative to QRS complexes
   • RP interval measurement 1

2. Differential diagnosis algorithm:

   • Regular narrow QRS tachycardia with visible P waves:
     • If RP < PR (short RP): Evaluate if RP < 90 ms
       • If yes: Likely AVNRT
       • If no: Likely AVRT
     • If RP > PR (long RP): Likely atrial tachycardia or PJRT 1

Acute Management

For Both Short RP and Long RP Tachycardias:

1. First-line treatments (Class I recommendations):

   • Vagal maneuvers (Valsalva, carotid sinus massage) 1, 2
   • Adenosine (6-12 mg IV rapid bolus) if vagal maneuvers fail 1, 2

2. If hemodynamically unstable:

   • Synchronized cardioversion (Class I recommendation) 1

3. If hemodynamically stable but first-line treatments fail:

   • IV diltiazem or verapamil (Class IIa recommendation) 1
   • IV beta-blockers (metoprolol, esmolol) 2

Response to Treatment as Diagnostic Tool:

• Short RP tachycardias (AVNRT, AVRT): Usually terminate with adenosine or vagal maneuvers 1, 3
• Long RP tachycardias:
  • AT: May temporarily slow with adenosine but often recurs immediately 4
  • PJRT: May terminate with adenosine but frequently recurs 4

Long-term Management

Short RP Tachycardias:

1. AVNRT:

   • Pharmacologic: Beta-blockers or non-dihydropyridine calcium channel blockers 2
   • Definitive: Catheter ablation (slow pathway modification) with >95% success rate 2

2. AVRT:

   • Pharmacologic: Beta-blockers, calcium channel blockers, or class IC agents 2
   • Definitive: Catheter ablation of accessory pathway with >95% success rate 2

Long RP Tachycardias:

1. Atrial Tachycardia:

   • Pharmacologic: Class IC agents, beta-blockers, or verapamil; amiodarone if others fail 5
   • Definitive: Catheter ablation with 80-95% success rate 5

2. PJRT:

   • Pharmacologic: Often resistant to medications 4, 6
   • Definitive: Catheter ablation of the decremental accessory pathway 4, 6

3. Atypical AVNRT:

   • Pharmacologic: Similar to typical AVNRT 2
   • Definitive: Slow pathway ablation 4

Special Considerations

• Tachycardia-mediated cardiomyopathy: More common with incessant long RP tachycardias, especially PJRT 2, 6
• Recurrent symptomatic episodes: Consider early referral for electrophysiology study and catheter ablation 2
• Diagnostic pitfalls:
  • Misdiagnosing wide-complex tachycardia as SVT when it could be ventricular tachycardia 2
  • Failing to recognize that SVT persisting for weeks to months can lead to cardiomyopathy 2

Treatment Algorithm

1. Acute episode:

   • Vagal maneuvers → Adenosine → IV calcium channel blockers/beta-blockers → Synchronized cardioversion

2. Recurrent episodes:

   • Document mechanism (short vs long RP)
   • For infrequent, well-tolerated episodes: PRN medications
   • For frequent, symptomatic episodes: Daily medications or catheter ablation
   • For incessant tachycardias (especially long RP): Early consideration of catheter ablation

Catheter ablation has become the definitive treatment of choice for most recurrent SVTs due to high success rates (80-95%) and low complication rates 2, 5.