[Comparison of different stimulation procedures of the calculation of so-called sinoatrial conduction time]

The results of the premature individual atrial stimulation for calculating the so-called sinuatrial conduction times (SACT) were compared with those in double-manifold atrial stimulation (n = 160), frequent atrial stimulation (n = 50) and ventricular individual and double-manifold stimulation (n = 14), respectively. Premature atrial individual stimulation and atrial double-manifold stimulation in these cases gave corresponding, closely correlating results for the SACT-calculation. In frequent atrial stimulation were calculated considerably longer as well as (more infrequently) clearly shorter conduction times. Calculation errors are on the one hand thinkable due to lacking, on the other hand due to repeated sinus node depolarisation with the possibility of overdrive suppression and overdrive excitation (sinus node depression and sinus node acceleration) since the method does not allow a control of the sinus node depolarisation performed. Also in modified calculation of the SACT with consideration of the duration of spontaneous periods after stimulation the correlation to the results of the individual stimulation was relatively loose. After ventricular stimulation (and following ventriculo-atrial stimulus conduction) essentially shorter sinuatrial conduction times could be calculated than in the atrial place of stimulation. As a rule, the poststimulatory spontaneous interval showed an abbreviation compared with the duration of periods before the stimulation, in which cases the haemodynamic relations changed due to ventricular stimulation might explain the increase of frequency.