CLINICAL AND ELECTROPHYSIOLOGICAL CHARACTERISTICS OF ATRIAL STANDSTILL

To clarify the clinical and electrophysiological characteristics of at rial standstill (AS) we studied 11 patients (7 males and 4 females), w hose average age was 62 years and who were followed over a period of 4 -179 months. Underlying heart disease was present in nine patients and two cases were idiopathic. Major clinical symptoms in the 11 cases in cluded Adams-Stokes attacks, and dyspnea on exertion. In the standard 12-lead ECGs obtained on admission, the P wave was absent in six cases . Atrial flutter (AF) was noted in 3, atrial fibrillation (Af) in 1, a nd multifocal atrial tachycardia in 1. In some cases, the ECG initiall y showed AF or Af, and was transformed after several years into ectopi c atrial tachycardia or an ectopic atrial rhythm with ct markedly decr eased amplitude of the P wave. Finally, the P wave disappeared over a prolonged period. When intracardiac mapping was performed, the atrial electrograms tended to diminish at the site of high, mid-lateral right atrium (RA). Electrograms were remained present in the vicinity of th e tricuspid valve (TV) annulus. A repeated mapping and pacing study co nducted in two patients revealed that the ''silent'' area spread towar d the lower site of RA. During the average follow-up period of 64 mont hs, four patients died. The interval until death in one patient with m yocarditis was 6 months, and in another with dilated cardiomyopathy (D CM) it was 8 months. It appears that the atrial muscular lesion starts in the high lateral RA and progresses toward the lower RA, then to th e vicinity of the TV annulus. A diffuse and progressive disturbance ma y occur not only in the atrial muscle, but also in the atrioventricula r conduction system in patients with AS who had progressive myocarditi s or DCM.