In a young, athletic male with an isolated short PR interval on a 12‑lead electrocardiogram, what is the clinical significance and what evaluation and management steps are recommended?

Short PR Interval in Young Athletic Males

Although a short PR interval (<120 ms) without delta wave can be a normal variant in athletes, it requires careful evaluation because it may reflect ventricular pre-excitation syndrome (Lown-Ganong-Levine syndrome) or underlying structural heart disease such as hypertrophic cardiomyopathy or Fabry's disease. 1

Clinical Significance

The isolated short PR interval carries different implications depending on associated ECG findings:

• Short PR with delta wave (slurred QRS upstroke) and widened QRS (>120 ms) indicates Wolff-Parkinson-White syndrome, which carries risk of sudden cardiac death due to rapid conduction of atrial fibrillation across the accessory pathway potentially leading to ventricular fibrillation 2, 3

• Isolated short PR without delta wave may represent either a benign normal variant (particularly common in athletes) or Lown-Ganong-Levine syndrome, requiring careful evaluation to exclude underlying structural disease 1, 2

• The short PR occurs due to either enhanced AV nodal conduction, shortened His-Purkinje conduction time, or an accessory pathway that bypasses the AV node 2, 4

Evaluation Algorithm

Step 1: Detailed History

Specifically assess for:

• Symptoms: palpitations, syncope, near-syncope, chest pain during palpitations, or episodes lasting >30 minutes 1, 5
• Family history: pre-excitation syndromes, cardiomyopathy, or sudden death in young relatives 1

Step 2: Echocardiography

Perform transthoracic echocardiography to exclude:

• Hypertrophic cardiomyopathy 1
• Ebstein anomaly 1
• Glycogen storage cardiomyopathy (PRKAG2-related familial WPW) 1

Step 3: Exercise Testing

• Assess for intermittent loss or sudden disappearance of pre-excitation pattern during exercise, which suggests a long anterograde refractory period of the accessory pathway and thus low risk of sudden death 1, 5
• Exercise testing helps unmask latent pre-excitation and assess arrhythmic risk 1

Step 4: 24-Hour Holter Monitoring

• Evaluate for paroxysmal tachyarrhythmias and assess QTc prolongation over time 1, 5
• Document any intermittent pre-excitation, which indicates lower risk 5

Step 5: Pharmacological Testing (if latent pre-excitation suspected)

• Vagal maneuvers, intravenous adenosine, or verapamil can unmask typical WPW ECG features by slowing or blocking conduction over the AV node 1

Risk Stratification for WPW Syndrome

High-risk features requiring specialist referral and electrophysiological study:

• Shortest pre-excited RR interval <250 ms during atrial fibrillation 2, 5
• History of symptomatic tachycardia or syncope 2, 5
• Multiple accessory pathways 2, 5
• Presence of Ebstein's anomaly 2
• Accessory pathway refractory period <240 ms 5

Low-risk indicators:

• Intermittent loss of pre-excitation on ambulatory monitoring 5
• Abrupt loss of pre-excitation during exercise testing 1, 5

Management Recommendations

For Confirmed WPW Syndrome (short PR with delta wave):

Athletes with diagnosed ventricular pre-excitation should be referred to a specialist for electrophysiological study (either transesophageal or intracardiac) to assess inducibility of AV re-entrant tachycardia and refractoriness of the accessory pathway, which influences eligibility for athletic competition, risk stratification, and therapy including catheter ablation. 1

• Catheter ablation is first-line definitive treatment for symptomatic patients with success rates of 95-98.5% and major complication rates of only 0.1-0.9% 5
• For high-risk WPW (shortest pre-excited RR interval ≤250 ms), catheter ablation is recommended 2

For Isolated Short PR Without Delta Wave:

• If asymptomatic with normal echocardiogram and no high-risk features on exercise testing or Holter monitoring, this may represent a benign normal variant in athletes 1, 2
• Continue periodic surveillance with repeat ECG and clinical assessment 1

Critical Pitfalls to Avoid

• Never use AV nodal blocking agents (digoxin, diltiazem, verapamil, beta-blockers) in pre-excited atrial fibrillation, as these are absolutely contraindicated due to risk of accelerating conduction through the accessory pathway and precipitating ventricular fibrillation 5

• Cardiac arrest is the first manifestation of WPW in approximately half of cases, emphasizing the critical importance of proper identification and risk stratification even in asymptomatic individuals 2

• Non-invasive tests are inferior to invasive electrophysiological assessment for determining sudden cardiac death risk in WPW syndrome 2

• Patients with altered refractory periods may be predisposed to reentrant AV nodal tachycardias even without a history of arrhythmias 4, 6