ARE DOUBLE POTENTIALS MARKERS OF A SPECIFIC ZONE OF THE ATRIOVENTRICULAR JUNCTION IN THE ISOLATED RABBIT HEART

A study is made of the characteristics of the atrial potentials record ed in the Koch triangle and its proximity, their variations on modifyi ng the site of cardiac pacing, and their usefulness as markers of a di stinct zone of the AV junction. In 12 isolated and perfused rabbit hea rt preparations an analysis was made of the endocardial atrial electro grams recorded with a multiple electrode positioned in the AV junction . The electrograms were obtained during spontaneous rhythm and on paci ng at the crista terminalis (CT), interatrial septum (IAS), left atriu m, and right ventricle. Double potentials were frequently obtained. On pacing at the CT, high-low double potentials (DP [H-L]) were more fre quent (P < 0.05) in the low CT (11% +/- 4% of the electrodes) and post erior zone of the Koch triangle (6% +/- 5%), than in the IAS (1% +/- 2 %) and anterior zone of the Koch triangle (2% +/- 3%). A similar tende ncy was observed either on pacing at the left atrium or during spontan eous rhythm. During pacing at the IAS the percentages of low-high doub le potentials (DP[L-H]) were significantly higher (P < 0.05) in the lo w CT (7% +/- 6%). DP (H-L) were of low sensitivity in indicating a giv en zone; maximum sensitivity was 61% in the low CT when pacing at the CT. DP (L-H) proved even less sensitive in indicating a given zone, th ough their specificity was greater in the low CT (91%) during pacing a t the IAS. The specific zones in which the highest percentages of DP ( H-L) or DP (L-H) are obtained depend on the site of cardiac pacing. On pacing at the IAS, DP (L-H) are more specific of the low CT. During p acing at both the CT and at the IAS, DP (H-L) sensitivity in indicatin g a given zone is low.