Relationship between surface electrocardiogram characteristics and endocardial activation sequence in patients with typical atrial flutter

Objectives: The relationships that exist between endocardial and surface el ectrocardiogram (ECG) activity in patients with AF1 have not been satisfact orily delineated. The aim of the study was to determine the relationships t hat exist between the atrial endocardial activity and the surface ECG in pa tients with atrial flutter (AFI). Methods: In 40 patients with AFI, a 64-electrode basket catheter (BC) was d eployed in the right atrium (RA). A decapolar catheter was inserted into th e coronary sinus (CS) to record from the left atrium. The temporal relation ship between endocardial and surface ECG activity was determined by means o f electronic calipers. Results: In counterclockwise AFl, the activation of the lateral wall of RA coincided with the positive deflections in lead I, V1 and V6 and the upstro ke component in inferior leads. Plateau duration in lead III (121+/-27 ms) correlated strongly with isthmus conduction time (117+/-23 ms) (r=0.91). Se ptal and left atrial conduction coincided with negative components in lead I. inferior leads and V6 and positive deflections in leads aVL and VI. In c lockwise AFl, the F wave was notched in all ECG leads. The first component resulted from the activation of the septum and posterior wall of the RA. Th e second component was coincident with activity recorded in CS electrograms . The interval between the two deflections (60+/-18 ms) correlated strongly with interatrial conduction time (57+/-19 ms) (r=0.84). Interatrial conduc tion interval was prolonged during AFl as compared to sinus rhythm (60+/-18 ms vs 43+/-13 ms, p=0.04). Activation of the lateral wall of RA coincided with the negative components in lead I, inferior leads and V6. Conclusions: The electrical activity in surface ECC; closely correlates wit h conduction in specific: parts of the atria. Polarity of the F wave in an ECG lend is determined by a resultant of opposing activities from the later al wall of the RA and the left atrium.