Author/Editor		Šinkovec, Matjaž
Title		Dipiridamol in nastanek vazovagalne sinkope
Type		monografija
Place		Ljubljana
Publisher		Medicinska fakulteta
Publication year		1999
Volume		str. 105
Language		slo
Abstract		Introduction. Adenosine is one of potential chemical mediators involved in the pathogenesis of vasovagal syncope. It is not clear whether this vasodepressory and cardioinhibitory reflex response is the primary adenosine effect or the secondary effect of its sympathoexcitation. The primary effect of exogenous adenosine is probably sympathoexcitation, however we have no such data for endogenous adenosine. It is possible that local accumulation of endogenous adenosine somewhere in the circulation could induce (directly or through afferent neural system) arterial hypotension and bradycardia. Hypothesis. We examined the hypothesis that endogenous adenosine is a primary trigger of vasovagal syncope in human being. Syncope, induced with orthostatic stress during head-up tilt-table test, was a model of spontaneously occurring vasovagal syncope. We were expecting more positive head-up tilt-table test results after application of dipyridamole than without it - in examinees with a history of vasovagal syncope. Namely, dipyridamole enhances the effects of endogenous adenosine (blocks the adenosine transport). We were trying to prevent syncope with theophylline, a competitive adenosine receptor blocker. Because it is difficult to measure local adenosine concentration, we analyzed the haemodynamic and power-spectral heart-rate variability changes. Immediate vasodepressory and cardioinhibitory responses may have suggested a primary endogenous adenosine effect. Subjects. Three groups were studied. The first consisted of 19 clinically healthy volunteers without history of syncope; average age 30 years. The second consisted of 28 volunteers with typical history of vasovagal syncope and negative head-up tilt-table test; average age 34 years. The third consisted of 25 volunteers with typical history of vasovagal syncope and positive head-up tilt-table test; average age 34 years. (trunc. at 2000 chars)
Descriptors		DIPYRIDAMOLE SYNCOPE, VASOVAGAL THEOPHYLLINE ADULT ELECTROCARDIOGRAPHY BLOOD PRESSURE HEART RATE HYPOTENSION BRADYCARDIA FOURIER ANALYSIS