What does an RSR (Ragged Red Spike) pattern in lead V1 on an electrocardiogram (ECG) indicate?

RSR' Pattern in Lead V1: Diagnostic Significance and Clinical Implications

An RSR' pattern in lead V1 on an electrocardiogram typically represents incomplete or complete right bundle branch block (RBBB), depending on QRS duration, and is often a normal variant in children and athletes when QRS duration is normal. 1, 2

Definition and Characteristics

• An RSR' pattern refers to a specific QRS morphology consisting of an initial small R wave, followed by an S wave, and then a terminal R' wave (r') deflection that is usually wider than the initial r wave 1, 3
• This pattern is characterized by an rSR', rsR', rSR', or rarely a qR configuration in leads V1 or V2 2
• The terminal R' wave represents delayed activation of the right ventricle due to conduction delay or block in the right bundle branch 3

Diagnostic Criteria and Classification

• Complete RBBB is diagnosed when the RSR' pattern is accompanied by:

  • QRS duration ≥120 ms in adults, >100 ms in children ages 4-16 years, and >90 ms in children <4 years of age 2, 3
  • S wave of greater duration than R wave or >40 ms in leads I and V6 2
  • Normal R peak time in leads V5 and V6 but >50 ms in lead V1 2

• Incomplete RBBB is diagnosed when:

  • Same QRS morphology criteria as complete RBBB but with QRS duration between 110-119 ms in adults 3
  • In children, when the terminal rightward deflection is <40 ms but ≥20 ms 3

• Normal variant RSR' is present when:

  • QRS duration is normal (<110 ms in adults) 1, 3
  • Particularly common in children and athletes 4, 3

Clinical Significance

• In athletes, isolated QRS voltage criteria for right ventricular hypertrophy (including RSR' pattern with normal QRS duration) is part of the normal spectrum of ECG findings and does not require further evaluation 4
• In children, an RSR' pattern in V1 and V2 with normal QRS duration is considered a normal variant 2, 3
• The presence of RSR' with prolonged QRS duration indicates conduction tissue disease affecting the right bundle branch 2

Differential Diagnosis

• The RSR' pattern in V1 may represent:
  • Incomplete or complete RBBB (most common cause) 1
  • Normal variant, especially in children and athletes 4, 3
  • Brugada syndrome (distinguished by coved ST-segment elevation ≥2 mm and terminal T-wave inversion) 1, 5
  • Right ventricular hypertrophy (RVH) 4
  • Ventricular aneurysm (when present in left surface leads) 6

Management Recommendations

• Asymptomatic patients with normal QRS duration (<110 ms) require no specific treatment, but should have routine follow-up 1
• Patients with incomplete RBBB (QRS 110-119 ms) should have annual follow-up to monitor for progression 1
• Patients with complete RBBB (QRS ≥120 ms) should be evaluated for underlying structural heart disease and monitored for development of higher-degree conduction disorders 1
• Patients with concerning features such as Brugada pattern, symptoms of syncope or pre-syncope, family history of sudden cardiac death, or evidence of progressive conduction disease should be referred to an electrophysiologist 1

Special Considerations

• The "Corrado index" (STJ/ST80 ratio <1 in normal RSR' vs >1 in Brugada) can help differentiate normal RSR' from Brugada pattern 1, 7
• A notched S wave in lead V1 with a final R' wave in right precordial accessory leads may suggest concealed RBBB 8
• In athletes, early repolarization consisting of J-point elevation with concave ST-segment elevation and peaked T-waves is present in up to 45% of Caucasian athletes and 63-91% of black athletes, and should be considered benign when present in isolation 4