Intermittent preexcitation indicates "a low-risk" accessory pathway: Time for a paradigm shift?

Area of Science:

• Cardiology
• Electrophysiology
• Medical Diagnostics

Background:

• Accessory pathways (APs) can cause preexcitation, a pattern seen on electrocardiograms (ECGs).
• Intermittent loss of this pattern can complicate diagnosis.
• Electrophysiological studies (EPS) are often used to evaluate APs.

Observation:

• Three patients with intermittent preexcitation on resting ECGs underwent EPS.
• Despite apparent poor conduction, fast anterograde conduction was documented in all cases.
• Shortest preexcited RR intervals ranged from 200-240 ms during atrial fibrillation or pacing with isoproterenol.

Findings:

• Intermittent preexcitation on standard ECGs lacks specificity for diagnosing APs with long refractory periods.
• Observed fast conduction contradicts the assumption of a poorly conducting AP based solely on intermittent findings.
• The phenomenon cannot substitute for a comprehensive electrophysiological study.

Implications:

• Relying solely on intermittent preexcitation for diagnosis can be misleading.
• Electrophysiological study remains essential for definitive assessment of accessory pathways.
• Accurate diagnosis is critical for appropriate patient management and risk stratification.