What does an RSR (Ragged S wave and R prime wave) pattern in leads V1 and V2 on an electrocardiogram (ECG) indicate?

RSR' Pattern in V1 and V2: Clinical Significance and Evaluation

An RSR' pattern in leads V1 and V2 on an electrocardiogram most commonly represents incomplete or complete right bundle branch block (RBBB), but can also indicate other cardiac conditions requiring further evaluation depending on QRS duration and associated ECG findings.

Definition and Diagnostic Criteria

The RSR' pattern consists of:

• An initial small R wave
• A subsequent S wave
• A terminal R' wave (often notched or slurred)

The American Heart Association/American College of Cardiology/Heart Rhythm Society guidelines define the criteria for RBBB as follows 1:

Complete RBBB:

• QRS duration ≥120 ms in adults
• RSR', rSR', or rSR pattern in leads V1 or V2
• R' or r' deflection usually wider than the initial R wave
• S wave of greater duration than R wave or >40 ms in leads I and V6
• Normal R peak time in leads V5 and V6 but >50 ms in lead V1

Incomplete RBBB:

• Same QRS morphology criteria as complete RBBB
• QRS duration between 110-119 ms in adults

Clinical Significance

The clinical significance of an RSR' pattern varies based on QRS duration and associated findings:

1. Normal Variant (QRS <110 ms)

• In children and adolescents up to age 16, an RSR' pattern in V1-V2 with normal QRS duration is considered a normal variant 1
• This pattern may also be seen in healthy adults, particularly when leads are placed higher than normal position 2

2. Incomplete RBBB (QRS 110-119 ms)

• May be a normal finding in otherwise healthy individuals
• Can be associated with underlying structural heart disease
• Requires clinical correlation with symptoms and other findings

3. Complete RBBB (QRS ≥120 ms)

• May indicate conduction system disease
• Can be associated with:
  • Coronary artery disease
  • Cardiomyopathies
  • Congenital heart disease
  • Pulmonary hypertension
  • Cor pulmonale

4. Other Pathological Conditions

• Myocardial infarction scar: An RSR' pattern unrelated to typical RBBB can indicate myocardial infarction scar tissue 3
• Brugada syndrome: A specific RSR' pattern with ST elevation in V1-V2 may indicate Brugada syndrome 4
• Arrhythmogenic right ventricular cardiomyopathy (ARVC): May present with RSR' pattern and other ECG abnormalities 5

Evaluation Algorithm

Step 1: Measure QRS Duration

• <110 ms: Likely normal variant, especially in children/young adults
• 110-119 ms: Incomplete RBBB
• ≥120 ms: Complete RBBB or other pathology

Step 2: Assess for Associated ECG Findings

• ST segment elevation or depression
• T wave inversions
• Pathological Q waves
• Axis deviation
• Other conduction abnormalities

Step 3: Clinical Correlation

• Asymptomatic with isolated finding:

  • QRS <110 ms: No further evaluation needed
  • QRS 110-119 ms: Consider baseline echocardiogram
  • QRS ≥120 ms: Echocardiogram recommended

• Symptomatic (syncope, palpitations, dyspnea) or with concerning family history:

  • Comprehensive cardiac evaluation regardless of QRS duration
  • Echocardiogram to assess for structural heart disease
  • Consider cardiac MRI if suspicion for ARVC or other cardiomyopathy 5
  • Exercise stress test if coronary artery disease is suspected

Step 4: Follow-up

• Isolated incomplete RBBB: No specific follow-up if no structural heart disease
• Complete RBBB: Regular ECG monitoring for progression to higher degrees of heart block 5
• RSR' with structural heart disease: Annual ECG and appropriate disease-specific follow-up

Special Considerations

1. Lead Placement: High placement of precordial leads can produce RSR' patterns that mimic pathology 2

2. Age Considerations: RSR' patterns are more common in children and may be normal variants until age 16 1

3. Differential Diagnosis: When evaluating RSR' patterns, consider:

   • Normal variant
   • RBBB (incomplete or complete)
   • Brugada syndrome
   • ARVC
   • Myocardial infarction scar 6, 3

4. Pitfalls to Avoid:

   • Misinterpreting normal variants as pathology, especially in young patients
   • Overlooking lead placement issues that can produce RSR' patterns
   • Failing to correlate ECG findings with clinical presentation and other diagnostic tests

By following this systematic approach, clinicians can appropriately evaluate and manage patients with RSR' patterns in leads V1 and V2, ensuring proper identification of both benign variants and potentially significant cardiac conditions.