In a healthy 37‑year‑old woman with a sinus rhythm ECG showing a short PR interval (106 ms), narrow QRS and normal QTc, what is the significance and recommended management?

Short PR Interval in an Asymptomatic Young Woman

In this healthy 37-year-old woman with a short PR interval (106 ms) but no symptoms, no delta waves, and normal QRS duration, reassurance and observation are appropriate—this represents a benign ECG variant that requires no treatment unless symptoms develop.

ECG Analysis and Significance

Your patient's ECG shows:

• Short PR interval (106 ms): Below the normal lower limit of 120 ms 1
• Normal narrow QRS (82 ms): Rules out ventricular pre-excitation 1
• Normal QTc (441 ms): No concerning repolarization abnormality
• Regular sinus rhythm at 82 bpm: Normal rate

Key Diagnostic Distinction

The critical finding is the absence of a delta wave with a narrow QRS complex. 2, 3

• A short PR interval with a wide QRS and delta wave indicates Wolff-Parkinson-White (WPW) syndrome—a potentially life-threatening condition requiring specialist referral 2, 3
• A short PR interval with a narrow QRS and no delta wave (as in your patient) represents either:
  • Enhanced AV nodal conduction (most common) 1
  • Lown-Ganong-Levine pattern (controversial entity)
  • Normal variant in a young, healthy individual

Management Approach

For Asymptomatic Patients (Current Presentation)

No intervention is required. 1

• The ACC/AHA guidelines emphasize that management depends entirely on the presence of symptoms, not ECG findings alone 1
• If the surface ECG shows no evidence of pre-excitation (delta wave) and the patient has no symptoms, no further diagnostic testing is necessary 1

If Symptoms Develop

Screen for precipitating factors first: 1

• Excessive caffeine intake
• Alcohol consumption
• Nicotine use
• Recreational drug use
• Hyperthyroidism

If palpitations occur: 1

• Teach vagal maneuvers (Valsalva, carotid massage)
• Consider empirical beta-blocker therapy only if significant bradycardia (<50 bpm) has been excluded 1
• Do NOT initiate class I or class III antiarrhythmic drugs without documented arrhythmia due to proarrhythmia risk 1

If paroxysmal tachycardia is documented: 1

• Refer for electrophysiology study and/or catheter ablation
• Catheter ablation has >95% success rate for accessory pathway-mediated tachycardias 2, 3

Critical Pitfalls to Avoid

Do Not Confuse with WPW Syndrome

The presence of a delta wave is the defining feature of ventricular pre-excitation. 2, 3

• Your patient has a narrow QRS (82 ms), which excludes significant pre-excitation 1
• WPW patients have wide QRS complexes (typically >110 ms) with visible delta waves 2
• WPW carries risk of sudden cardiac death if atrial fibrillation develops with rapid conduction over the accessory pathway 2, 3

Do Not Over-Investigate

• Routine electrophysiology studies are not indicated in asymptomatic patients with short PR intervals and narrow QRS complexes 1
• Event monitors or Holter monitoring are only useful if the patient reports symptoms suggestive of arrhythmia 1

Do Not Prescribe Antiarrhythmics Empirically

Antiarrhythmic drugs should never be initiated without documented arrhythmia due to the risk of proarrhythmia, which can be life-threatening 1

Follow-Up Recommendations

• Reassure the patient that this ECG finding is benign in the absence of symptoms
• Educate about symptoms that should prompt evaluation: sudden-onset regular palpitations, lightheadedness, syncope, or chest discomfort 1, 3
• Obtain a 12-lead ECG during any future tachycardia episode to establish the diagnosis before initiating treatment 1, 3
• No restrictions on activity or lifestyle are necessary 1