[Effect of body position on the ability to initiate paroxysmal supraventricular reentry tachycardias and on the conduction system properties of the reentry circuit].

The obtainability as well as the maintenance and termination of paroxysmal supraventricular reentry tachycardias depend upon the interaction of the individual components of the reentry circle, in which cases the properties of the pathway are influenced by the changing preponderance of the sympathetic and parasympathetic tonus and thus also by the body position. In 29 investigations by means of highly frequent and programmed transoesophageal atrial stimulation the influence of the body position on the initiation possibility of the paroxysmal supraventricular tachycardia and on the pathway properties of the individual components of the reentry circle are analysed. The investigations were performed either in the standing position or in lying position, in 16 patients for the objectivation of anamnestically reported paroxysms of tachycardia and in 13 patients for the therapy control after medicamentous stabilisation. In 6 patients supraventricular reentry tachycardias could be initiated only in standing position, in lying position only a few echo systoles appeared. In 9 patients in whom we obtained a tachycardia both in standing position and in lying position in upright posture an in most cases clear increase of the frequency of tachycardia was found. The evocation mode of the tachycardia was partly alleviated in the standing position, but also rendered difficult in several cases. It seems to be indicated to repeat the investigation under orthostatic conditions, when an adequate anamnesis of the tachycardia is present and an initiation possibility in lying position is lacking, or when a great subjective impairment in a paroxysm of tachycardia is reported and there is a relatively low frequency of tachycardia in lying position.