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Figure 4. Structure and Mechanisms of AF
e most common sites of origin for non-PV atrial triggers include the posterior wall of
the LA, the superior vena cava, the crista terminalis, the fossa ovalis, the coronary sinus
(CS), the Eustachian ridge, the ligament of Marshall, and adjacent to the AV valve annuli.
e le atrial fractionated atrial potentials (FAP) are usually located in 4 areas: 1) Le
atrial appendage Ridge FAP area (between LAA and le PVs); 2) Superior Le FAP area;
3) Infero-Posterior FAP area; and 4) Anterior Right FAP area. Sites exhibiting a positive
HFS response (transient AV block, increase in mean R-R interval >50% during AF)
identify the 5 major GP (Marshall Tract GP, Superior Le GP, Anterior Right GP, Inferior
Le GP, and Inferior Right GP.
