[Influence of atrial contraction on stroke volume in pacemaker stimulation]

The contribution of the atrial systole to the stroke volume was studied in 12 patients with implanted pacemakers by means of impedance-cardiography. P-ST-intervals between 70 and 200 msec. increased the stroke volume as compared with systoles without preceding P-waves. A maximal stroke volume was observed with a P-ST-interval of 130 msec. The increase of the stroke volume by 33% justifies the application of atrial triggered pacemakers in selected cases, mainly in younger patients despite of the technical limitations of these pacemaker systems.