ECG Atrial Enlargement Criteria (left and right)
ECG criteria for atrial enlargement, the atrial companion to the LVH voltage criteria.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- P duration, lead II
- 130 ms
- P amplitude, V1
- 2 mm
Result: P wave analysis - criteria met for BOTH left and right atrial enlargement.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Left
- Any one of: P duration in lead II 120 ms or more; a notched limb-lead P with peaks 40 ms or more apart; a V1 terminal negative deflection 40 ms or more long AND 1 mm or more deep.
- Morris index
- The product of the V1 terminal deflection duration and depth. Both halves are needed; one alone neither meets nor excludes it.
- Right
- P amplitude greater than 2.5 mm in lead II, or greater than 1.5 mm in V1.
- Careful
- The thresholds are NOT symmetric. Left-sided are or-more; right-sided are strictly greater. A P of exactly 2.5 mm in lead II does not meet the right criterion.
- Scope
- Sensitivity for the left criteria is about 50% at about 90% specificity. A normal P wave does not rule enlargement out; an echocardiogram measures what this infers.
What you enter
- P duration, lead II
- Notch inter-peak
- V1 terminal force duration
- V1 terminal force depth
- P amplitude, lead II
- P amplitude, V1
How this is calculated
Morris JJ, Estes EH, Whalen RE, Thompson HK, McIntosh HD. P-wave analysis in valvular heart disease. Circulation. 1964;29:242-252 (P terminal force). Standard left and right atrial P wave criteria as taught in the University of Utah ECG learning modules. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.