What is the management approach for an asymptomatic patient with sinus rhythm and a short PR interval?

Management of Asymptomatic Sinus Rhythm with Short PR Interval

Asymptomatic patients with sinus rhythm and a short PR interval (<120 ms) require no specific intervention but need evaluation to exclude Wolff-Parkinson-White syndrome and other pre-excitation patterns that could predispose to sudden cardiac death. 1

Initial Evaluation

The key distinction is whether the short PR interval represents:

• Pre-excitation syndrome (WPW): Look for delta waves on the 12-lead ECG, which indicate ventricular pre-excitation via an accessory pathway 1, 2
• Enhanced AV nodal conduction: Short PR with normal QRS morphology and no delta waves 1, 3
• Pseudo-RBBB pattern: An rSr' complex in lead V1 may be the sole manifestation of a left-sided accessory pathway, even without classic delta waves 2

Critical ECG Features to Assess

Carefully examine the ECG for:

• Delta waves: Slurred upstroke of the QRS complex indicating pre-excitation 1
• QRS duration and morphology: Normal narrow QRS (<120 ms) suggests enhanced AV nodal conduction rather than accessory pathway 1
• Lead V1 morphology: Pseudo-partial RBBB (rSr' pattern) may indicate a concealed left-sided accessory pathway 2

Risk Stratification

Low-Risk Features (No Further Action Required)

• Short PR interval with normal QRS morphology and no delta waves 1
• No family history of sudden cardiac death 4, 5
• No associated bradycardia or conduction abnormalities 5

High-Risk Features (Require Further Evaluation)

• Any evidence of delta waves suggesting WPW syndrome, even if intermittent 1, 6
• Short PR combined with bradycardia (heart rate <60 bpm), which has been associated with malignant ventricular arrhythmias in children 5
• Family history of sudden cardiac death, syncope, or supraventricular tachycardia 4
• Pseudo-RBBB pattern in V1 that may indicate concealed accessory pathway 2

Management Algorithm

For Asymptomatic Patients WITHOUT Delta Waves

No intervention is required. 1 These patients have enhanced AV nodal conduction, which is a benign finding. However:

• Provide reassurance that this is a normal variant 1
• Document the finding for future reference 1
• No routine follow-up ECGs are necessary unless symptoms develop 1

For Patients WITH Delta Waves (WPW Pattern)

Even if asymptomatic, these patients require risk stratification because pre-excited atrial fibrillation can cause sudden cardiac death 2:

• Refer to electrophysiology for risk stratification 2
• Consider electrophysiologic study (EPS) to assess accessory pathway properties, particularly if the patient is young or engaged in competitive athletics 7
• Radiofrequency ablation should be discussed as a curative option, especially for high-risk pathways 2

Special Considerations

Athletes: In asymptomatic athletes, even PR intervals of 200-400 ms are considered normal variants and require no evaluation 1. However, a short PR (<120 ms) with delta waves still warrants evaluation for WPW syndrome 1

Pediatric patients: The combination of short PR, bradycardia, and any history of syncope represents a high-risk syndrome for malignant ventricular arrhythmias and sudden death 5. These patients require immediate electrophysiology referral 5

Common Pitfalls to Avoid

• Missing subtle delta waves: Carefully examine all 12 leads, as delta waves may be prominent in some leads and absent in others 6
• Overlooking pseudo-RBBB in V1: This pattern may be the only ECG manifestation of a left-sided accessory pathway 2
• Dismissing short PR in the presence of bradycardia: This combination, particularly in young patients, has been associated with high risk of sudden death 5
• Assuming all short PR intervals are benign: While enhanced AV nodal conduction is benign, pre-excitation syndromes carry risk of sudden death and require evaluation 1, 2

When to Refer to Electrophysiology

Refer for EP consultation if:

• Any delta waves are present, even if intermittent 2, 6
• Pseudo-RBBB pattern in V1 suggesting concealed accessory pathway 2
• Short PR combined with bradycardia, especially in children or young adults 5
• Family history of sudden cardiac death or documented accessory pathways 4
• Patient develops palpitations, syncope, or documented supraventricular tachycardia 7, 4