What is the recommended work‑up for a patient with sinus rhythm and a short PR interval on the electrocardiogram suggestive of a pre‑excitation syndrome?

Workup for Sinus Rhythm with Short PR Interval

A short PR interval (<120 ms) without a delta wave is most commonly a benign variant—especially in young, athletic males—but requires careful evaluation to exclude Wolff-Parkinson-White syndrome, Lown-Ganong-Levine syndrome, or underlying structural heart disease such as hypertrophic cardiomyopathy or Fabry disease. 1, 2

Step 1: Confirm the ECG Findings

• Measure the PR interval precisely in lead II, V3, or V5; a PR <120 ms defines a short interval. 2
• Inspect all 12 leads carefully for a delta wave—a slurred upstroke of the QRS complex—which, if present with QRS duration >120 ms, establishes a WPW pattern and mandates comprehensive risk stratification. 1, 2, 3
• Verify QRS duration: A normal QRS (<120 ms) without a delta wave suggests either a benign variant or Lown-Ganong-Levine syndrome; a wide QRS with a delta wave confirms WPW. 2, 3

Step 2: Obtain a Focused Clinical History

• Symptoms of tachyarrhythmia: Ask specifically about palpitations, syncope or near-syncope, chest discomfort during palpitations, and episodes lasting >30 minutes. 1, 2, 4
• Family history: Inquire about pre-excitation syndromes, cardiomyopathy, or sudden cardiac death in young first-degree relatives. 1, 2
• Athletic participation: Document the level and intensity of competitive sports, as this influences risk stratification and clearance decisions. 1, 2

Step 3: Perform Transthoracic Echocardiography

• Rule out structural heart disease including Ebstein anomaly, hypertrophic cardiomyopathy, glycogen-storage cardiomyopathy (PRKAG2-related familial WPW), and left ventricular hypertrophy. 1, 2, 5
• Fabry disease should be considered if left ventricular hypertrophy is present, especially with multisystem symptoms (renal, dermatologic, neurologic). 2, 5

Step 4: Non-Invasive Risk Stratification

Exercise Stress Testing (First-Line)

• Abrupt, complete loss of pre-excitation at higher heart rates indicates a long anterograde refractory period of the accessory pathway and low risk of sudden death, permitting continued athletic participation. 1, 2, 4
• Persistent pre-excitation during exercise suggests a shorter refractory period and warrants further evaluation with electrophysiological study. 1, 2

24-Hour Holter Monitoring

• Intermittent pre-excitation on ambulatory monitoring suggests a low-risk pathway (≈90% positive predictive value) and may obviate the need for stress testing. 2, 4
• Document paroxysmal tachyarrhythmias and monitor QTc trends over time. 1, 2

Pharmacological Testing (Optional)

• Vagal maneuvers, intravenous adenosine, or verapamil may unmask latent WPW features by slowing or blocking AV-node conduction when the diagnosis is uncertain. 1, 2
• Caution: Adenosine is contraindicated in pre-excited atrial fibrillation (wide QRS ≥120 ms) as it may precipitate ventricular fibrillation. 2, 4

Step 5: Electrophysiological Study (When Indicated)

• Refer for EP study if:
  • Non-invasive testing is inconclusive (persistent pre-excitation during exercise). 1, 2
  • The patient is a competitive athlete in moderate/high-intensity sports, regardless of stress-test results, because catecholamine surges may shorten pathway refractory periods. 2, 4
  • Symptomatic tachyarrhythmias are documented (palpitations, syncope). 1, 2, 4
• EP study determines:
  • Inducibility of AV re-entrant tachycardia. 1, 2
  • Shortest pre-excited RR interval during induced atrial fibrillation; an interval ≤250 ms (≥240 bpm) defines a high-risk pathway warranting catheter ablation. 2, 4
  • Accessory pathway effective refractory period <240 ms. 4

Step 6: Management Based on Findings

If WPW Pattern Is Confirmed (Short PR + Delta Wave + Wide QRS)

• Catheter ablation is the definitive therapy, achieving >95% acute success with <1% risk of complete heart block. 2, 4
• High-risk features mandating ablation (Class I):
  • Shortest pre-excited RR ≤250 ms during atrial fibrillation. 2, 4
  • Symptomatic tachycardia (palpitations, syncope). 2, 4
  • Competitive athletes in moderate/high-intensity sports. 2, 4

If Isolated Short PR Without Delta Wave

• Asymptomatic with normal echocardiogram and low-risk stress test: The short PR is likely a benign variant; periodic surveillance with repeat ECG and clinical review is sufficient. 1, 2
• Symptomatic or structural heart disease suspected: Further evaluation with echocardiography and consideration of rate-controlling agents (beta-blockers, calcium-channel blockers) for supraventricular tachycardia. 2, 5

Critical Pitfalls to Avoid

• Do not dismiss a WPW pattern as benign, even in asymptomatic patients, because sudden death can be the first manifestation in approximately 50% of cardiac arrest cases. 2, 4
• Never administer AV-nodal blocking agents (beta-blockers, calcium-channel blockers, digoxin, adenosine) in WPW patients presenting with atrial fibrillation and a wide QRS (≥120 ms), as these drugs can facilitate rapid conduction through the accessory pathway and precipitate ventricular fibrillation. 2, 4
• Ensure proper ECG calibration and use age-appropriate PR interval norms, particularly in pediatric populations. 5
• Do not attribute a short PR to "athletic heart" without first excluding WPW by carefully evaluating for a delta wave. 2, 5

Summary Algorithm

1. Measure PR interval and inspect for delta wave on 12-lead ECG. 2, 3
2. Obtain symptom and family history focused on palpitations, syncope, and sudden death. 1, 2
3. Perform echocardiography to exclude structural heart disease. 1, 2, 5
4. Exercise stress testing: Loss of pre-excitation = low risk; persistent pre-excitation = EP study. 1, 2, 4
5. 24-hour Holter: Intermittent pre-excitation = low risk. 2, 4
6. EP study if stress test inconclusive, competitive athlete, or symptomatic. 1, 2, 4
7. Catheter ablation for confirmed high-risk WPW; observation for benign isolated short PR. 2, 4