What are the implications and management of an Rsr pattern in lead V1 on an electrocardiogram (ECG) in a patient?

RSR' Pattern in Lead V1: Clinical Significance and Management

The clinical significance of an RSR' pattern in V1 depends entirely on QRS duration: if QRS is <110 ms in adults, it is a benign normal variant requiring no workup; if QRS is ≥120 ms, it represents complete right bundle branch block (RBBB) requiring evaluation for underlying cardiac pathology. 1, 2

Diagnostic Approach Based on QRS Duration

Normal Variant (QRS <110 ms)

• When QRS duration is normal (<110 ms in adults, <100 ms in children 4-16 years, <90 ms in children <4 years), the RSR' pattern is a benign normal variant that requires no further evaluation. 1, 2
• This is particularly common in children, young adults, and athletes, where isolated QRS voltage criteria with RSR' pattern is part of the normal ECG spectrum. 1, 3
• No echocardiography, stress testing, or additional workup is indicated in asymptomatic individuals with normal QRS duration. 2

Incomplete RBBB (QRS 110-119 ms in adults)

• The same RSR' morphology criteria apply, but QRS duration falls between 110-119 ms in adults (90-100 ms in children 4-16 years). 4, 2
• New-onset incomplete RBBB warrants echocardiography to assess for structural heart disease, right ventricular pressure/volume overload, or conduction system disease. 2

Complete RBBB (QRS ≥120 ms in adults)

Complete RBBB is diagnosed when all of the following criteria are met: 4, 3

• QRS duration ≥120 ms in adults (>100 ms in children 4-16 years, >90 ms in children <4 years)
• RSR', rsR', rSR', or rarely qR pattern in leads V1 or V2, with the 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

Complete RBBB indicates conduction tissue disease affecting the right bundle branch and requires echocardiography to evaluate for underlying structural heart disease. 2, 3

Alternative Pathological Causes to Consider

When RSR' pattern exists with wide QRS but doesn't meet RBBB criteria, consider: 5, 6

• Myocardial infarction scar: RSR' with wide QRS (≥110 ms) unrelated to typical RBBB or LBBB pattern may represent terminal conduction delay within impaired tissue surrounding infarct scar, with high specificity for myocardial infarction. 5
• Brugada syndrome: Life-threatening condition that can present with RSR' pattern in V1-V2; look for coved ST-segment elevation. 6
• Arrhythmogenic right ventricular dysplasia: Can present with RSR' pattern; consider in patients with ventricular arrhythmias or family history. 6
• Right ventricular hypertrophy: May show RSR' pattern with other voltage criteria for RVH. 1
• Posterior myocardial infarction: Can produce prominent R wave in V1 mimicking RSR' pattern. 7

Critical Pitfalls to Avoid

• Never use the terms "RSR'" or "normal RSR'" interchangeably, as this creates confusion and potential misinterpretation. 2, 3
• Incorrect lead placement (V1 recorded too high or too far right) can create a false RSR' pattern; verify proper lead placement before making clinical decisions. 2
• In patients over 30 years with new RSR' pattern and wide QRS, always consider underlying cardiopulmonary disease rather than dismissing as benign variant. 8
• The height of the terminal R' wave matters: when R' is higher than the initial R wave in patients over 30 years, it is associated with cardiopulmonary disease in 5.9% of cases. 8

Management Algorithm

For asymptomatic patients with RSR' in V1:

1. Measure QRS duration precisely
2. If QRS <110 ms → benign normal variant, no workup needed 1, 2
3. If QRS 110-119 ms → incomplete RBBB, obtain echocardiogram if new-onset 2
4. If QRS ≥120 ms → complete RBBB, obtain echocardiogram to evaluate for structural disease 2, 3
5. If wide QRS but atypical for RBBB → consider myocardial scar, obtain echocardiogram and consider cardiac MRI 5

For symptomatic patients (syncope, cardiac arrest, palpitations):

• Obtain echocardiogram regardless of QRS duration 2
• Consider Brugada syndrome evaluation with provocative testing if appropriate clinical context 6
• Evaluate for arrhythmogenic right ventricular dysplasia if ventricular arrhythmias present 6