Arruda criteria for localization of wpw pathways step vise easy to und

Arruda criteria for localization of wpw pathways step vise easy to understand

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Arruda criteria WPW accessory pathway localization stepwise algorithm ECG

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Arruda algorithm WPW pathway localization delta wave V1 II aVF steps explained

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https://www.slideshare.net/slideshow/localization-of-wpw-acc…

Here is the complete, stepwise breakdown of the Arruda Criteria for WPW accessory pathway (AP) localization - one of the most accurate ECG algorithms available (sensitivity ~90%, specificity ~99%).

Arruda Criteria - WPW Accessory Pathway Localization

Background

Developed by Arruda et al. (1998) correlating 12-lead ECG with successful RF ablation sites
Uses the initial 20 ms of delta wave polarity in leads I, II, aVF, and V1
Delta wave classified as: Positive (+), Negative (-), or Isoelectric (+/-)
Also uses R:S ratio in V1 and lead III
Localizes the AP to 10 positions around the tricuspid and mitral annuli

The 4 Steps

STEP 1 - Is it a Left Free Wall Pathway?

Look at: Lead I and Lead V1

Finding	Interpretation
Delta wave in Lead I is negative or isoelectric	→ LEFT Free Wall pathway
OR R wave > S wave amplitude in V1 (R > S in V1)	→ LEFT Free Wall pathway

If either of these is present → proceed to aVF to pinpoint left side location (Step 2).

If neither → move to Step 3 (septal or right free wall).

STEP 2 - Pinpoint the Left Free Wall Pathway

Look at: Lead aVF (only if Step 1 positive)

aVF Delta Wave	Location
Positive	Left Lateral / Left Anterolateral
Isoelectric or Negative	Left Posterior / Left Posterolateral

Summary: Left side + aVF positive = anterolateral; aVF negative/iso = posterolateral

STEP 3 - Septal Pathways (if Step 1 negative)

Look at: Lead V1

V1 Delta Wave	Interpretation
Negative or Isoelectric	→ SEPTAL pathway - now check aVF
Positive	→ RIGHT Free Wall pathway - go to Step 4

If V1 is Negative/Isoelectric → Check aVF:

aVF Delta Wave	Location
Negative	Posteroseptal - Tricuspid annulus (right posteroseptal)
Isoelectric	Posteroseptal - Could be tricuspid OR mitral annulus
Positive	Anteroseptal / Right Anterior Paraseptal / Midseptal (tricuspid annulus)

Tip: A "±" in aVF means you can't distinguish right vs left posteroseptal by ECG alone - EP study needed.

STEP 4 - Right Free Wall Pathway

Look at: Lead aVF (only after V1 is Positive and left side was excluded in Step 1)

aVF Delta Wave	Proceed to...	Location
Positive	-	Right Anterior / Right Anterolateral
Isoelectric or Negative	Check Lead II

If aVF is Isoelectric/Negative → Check Lead II:

Lead II Delta Wave	Location
Positive	Right Lateral
Isoelectric	Right Posterior / Right Posterolateral

Summary Flowchart (Text Version)

START
│
├─ Lead I negative/iso OR R>S in V1?
│   YES → LEFT FREE WALL
│          aVF (+) → Left Lateral / Anterolateral
│          aVF (-/±) → Left Posterior / Posterolateral
│
│   NO ↓
│
├─ V1 negative/iso?
│   YES → SEPTAL
│          aVF (-) → Right Posteroseptal
│          aVF (±) → Right or Left Posteroseptal
│          aVF (+) → Anteroseptal / Midseptal
│
│   NO (V1 positive) → RIGHT FREE WALL
│          aVF (+) → Right Anterior / Anterolateral
│          aVF (-/±) → check Lead II
│                       II (+) → Right Lateral
│                       II (±) → Right Posterior / Posterolateral

10 AP Locations Identified

#	Location	Abbreviation
1	Left Lateral / Anterolateral	LAL
2	Left Posterior / Posterolateral	LPL
3	Right Posteroseptal (tricuspid)	RPS
4	Left or Right Posteroseptal (ambiguous)	PS ±
5	Anteroseptal	AS
6	Midseptal	MS
7	Right Anterior Paraseptal	RAPS
8	Right Anterior / Anterolateral	RAL
9	Right Lateral	RL
10	Right Posterior / Posterolateral	RPL

Key Points to Remember

Lead I + V1 are your first filters - they split left free wall from everything else
aVF is the most-used secondary lead - it appears in all 3 branches
V1 negative always means septal before assuming right-sided
The original paper used only the first 20 ms of the delta wave - not the entire QRS
Isoelectric delta in aVF at the septal step is the one "gray zone" where ECG can't distinguish right vs left posteroseptal
Right-sided APs tend to have wider QRS (~145 ms) than left-sided (~131 ms)

The original Arruda et al. paper is published in PACE (1998), PMID 9475572, and remains a reference standard for pre-ablation planning.

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