R Wave Equal to S Wave in Lead V2: Normal Variant
An R wave equal to the S wave in lead V2 (R/S ratio = 1) represents the normal transition zone and is not abnormal. This finding typically indicates the transitional lead where R wave progression shifts from predominantly negative to predominantly positive complexes across the precordial leads.
Understanding Normal R Wave Progression
In the precordial leads, the R wave normally increases in amplitude from V1 to V6, while the S wave decreases. Lead V2 commonly serves as part of the transition zone where:
- R and S waves may be approximately equal (R/S ratio ≈ 1)
- This represents normal electrical transition from right to left ventricular forces
- The transition typically occurs between V2 and V4 in most individuals 1
When Equal R and S Waves Become Significant
While an R/S ratio of 1 in V2 is generally normal, context matters:
Consider Pathology If:
- Right ventricular hypertrophy: Look for R/S ratio ≥1 specifically in V1 (not V2), along with right axis deviation and tall R waves in V1 1
- Posterior MI: R/S ratio ≥1 in V1-V2 with R wave duration ≥40 ms suggests lateral/posterior infarction 2
- Bundle branch blocks: Complete RBBB shows rsr', rsR', or rSR' patterns in V1-V2, not simply equal R and S waves 3, 4
Key Distinguishing Features:
Normal variant in V2:
- Isolated finding
- Normal QRS duration (<110 ms)
- Normal axis
- Appropriate R wave progression in other leads
- Lead V3 typically shows dominant R wave
Pathologic patterns:
- Abnormalities extend to V1 or multiple leads
- Associated QRS prolongation (≥120 ms for complete blocks)
- Axis deviation present
- Additional ECG abnormalities (ST changes, Q waves)
Common Pitfalls to Avoid
Don't confuse V2 with V1: The critical R/S ratio for RVH is in V1, not V2. An R/S ratio ≥1 in V1 with appropriate clinical context suggests RVH, but the same finding in V2 is often normal 1
Check lead placement: Precordial lead misplacement by even 2 cm can create diagnostic errors. Verify proper electrode positioning, especially if the finding seems inconsistent with clinical presentation 5, 6
Consider the entire ECG: Don't interpret V2 in isolation. Examine the complete R wave progression from V1-V6, QRS duration, axis, and presence of other abnormalities 7, 8
Clinical Approach
If you encounter R=S in lead V2:
- Verify this is truly V2 (not mislabeled V1)
- Check QRS duration (should be <110 ms if normal)
- Examine V1: R/S ratio should be <1 in normal hearts
- Examine V3-V4: Should show dominant R waves
- Assess for right axis deviation (would suggest RVH)
- Look for other ECG abnormalities
No further workup is needed if the patient is asymptomatic with normal QRS duration, normal axis, and appropriate R wave progression in adjacent leads. This represents normal cardiac electrical transition.