912-40 Assessment of Atrial Electromechanical Sequence in Patients with DDD Pacemakers

Abstract

To assess the effect of right atrial appendage pacing on atrial electromechanical sequence, we studied 20 patients (pts) with DDD pacemakers and 20 age-matched normals. Atrial motion was recorded in the anterior, lateral, posterior sites of mitral and tricuspid rings as well as central fibrous body (CFB) by 2D guided M-mode echo. Atrial electromechanical delay (EM-D), from onset of p wave or atrial pacing spike to that of atrial contraction was measured at each site; intraatrial dispersion, the time from earliest to latest onset of motion around each ring, and interatrial delay were measured. In normals, EM-D is 68 ± 7 ms at the lateral site of right atrium (RA), 81 ± 9 ms at the CFB, 94 ± 11 ms at the lateral site of left atrium (LA). In pts, EM-D at corresponding sites increased to 85 ± 22 ms, 117 ± 23 ms and 138 ± 25 ms respectively (all p < 0.01). The interatrial delay increased from 26 ± 7 ms in normals to 53 ± 18 ms in pts (p < 0.01). RA dispersion increased from 6 ± 2 ms in normals to 19 (2) in pts (p < 0.01), but LA dispersion remained unchanged. Right atrial pacing disturbs the normal coordinate sequence of RA mechanical activity, leads to a striking and variable increase in interatrial conduct time. LA contraction remains synchronous. These values should be determined in individual pts to allow optimal setting of DDD pacemakers.