What does an RSR' pattern in leads V1 and V2 on an electrocardiogram (EKG) indicate?

RSR' Pattern in V1 and V2 on EKG: Significance and Interpretation

An RSR' pattern in leads V1 and V2 on an electrocardiogram most commonly indicates right bundle branch block (RBBB) when the QRS duration is prolonged, or may represent a normal variant when QRS duration is normal, especially in children.

Definition and Characteristics

• RSR' pattern refers to a specific QRS complex morphology consisting of an initial small R wave, followed by an S wave, and then a second R wave (R') in leads V1 and V2 1
• The R' or r' deflection is usually wider than the initial R wave according to established criteria 1
• This pattern is one of the hallmark features of right bundle branch block when accompanied by appropriate QRS duration criteria 1

Diagnostic Criteria for Complete RBBB

• QRS duration ≥120 ms in adults, >100 ms in children ages 4-16 years, and >90 ms in children <4 years of age 1
• RSR', rsR', rSR', or rarely a qR pattern in leads V1 or V2 1
• S wave of greater duration than R wave or >40 ms in leads I and V6 1
• Normal R peak time in leads V5 and V6 but >50 ms in lead V1 1

Diagnostic Criteria for Incomplete RBBB

• Same QRS morphology criteria as complete RBBB but with a QRS duration between 110-119 ms in adults 1
• In children, incomplete RBBB may be diagnosed when the terminal rightward deflection is <40 ms but ≥20 ms 1
• May be present in the absence of heart disease, particularly when lead V1 is recorded higher than or to the right of normal position 1

Normal Variant Considerations

• In children, an RSR' pattern in V1 and V2 with a normal QRS duration is considered a normal variant 1
• The terms "RSR" and "normal RSR" are not recommended to describe such patterns due to potential misinterpretation 1
• High placement of precordial leads can produce an RSR' pattern that may be mistaken for pathology 2

Pathological Significance

• Beyond RBBB, an RSR' pattern may indicate:
  • Cardiac sarcoidosis (when accompanied by fragmented QRS) 3
  • Brugada syndrome (requires specific ST segment characteristics) 4, 2
  • Ventricular aneurysm (when present in left surface leads) 5
  • Arrhythmogenic right ventricular dysplasia 4
  • Myocardial scarring in coronary artery disease 6

Clinical Implications

• The presence of RSR' with prolonged QRS duration indicates conduction tissue disease affecting the right bundle branch 1
• When RSR' is accompanied by fragmented QRS in patients with pulmonary sarcoidosis, it should prompt further evaluation for cardiac involvement 3
• RSR' pattern with normal QRS duration in adults may warrant further investigation to rule out pathology, especially in the presence of symptoms 4
• In asymptomatic individuals, especially children, with normal QRS duration, an RSR' pattern is often benign 1

Common Pitfalls and Caveats

• Misplacement of precordial leads (especially high placement) can produce an RSR' pattern that mimics pathology 2
• Normal variants can be misinterpreted as pathological after clinical events such as syncope or cardiac arrest of unknown cause 4
• The RSR' pattern alone is insufficient for diagnosing specific cardiac conditions and should be interpreted in clinical context 4, 3
• In children, the RSR' pattern with normal QRS duration should not be misinterpreted as pathological 1