No abstract

Aims To analyse the long-term outcome of the largest reported cohort of patients presenting asystole during head-up tilt test. (80 ) n=198)) influenced the time to the syncopal episode (13 (6·5, 20·5) vs 2 (1, 6·5) min, P=0,0005) but not the duration of the asystole. During this period, therapy for asystole featured three different stages: first patients were treated with pacemakers; later drug therapy (metoprolol and/or etilefrine) was recommended; lastly (from 1995), no specific treatment was given. In a cohort age-and gender-matched study, those patients without were compared to those with asystole in a 2:1 basis. During 40·7 months of follow-up (17·7, 66·8), 12 patients (20·6%) with asystole had syncopal recurrences. Furthermore, 34 patients (28·8%) without asystole presented syncopal episodes during a follow-up of 51·6 months (29·3, 73·1) (P=ns). The Kaplan-Meier analysis in patients with and without asystole showed a mean time free of recurrence of 92·6 6 months vs 82·6 4·7 months (P=ns). The previous number of syncopes had a significant relationship with recurrences (P=0·002), but not therapy. There were no cardiac related deaths. Methods and Results Conclusions(1) Asystole during head-up tilt test does not imply a malignant outcome and syncope recurrence is low; (2) pacemaker or drug therapy do not significantly influence outcome which correlates to the previous number of syncopal episodes but not to gender, age, asystole occurrence, asystole duration and timing to asystole during head-up tilt test; (3) tilting protocol (angle) might influence time to and incidence of asystole during head-up tilt test.

To facilitate the quantitative analysis of post-occlusive reactive hyperaemia (PORH), measured with laser-Doppler perfusion monitoring (LDPM) on extremities, we present a flow model for the dynamics of the perfusion of the tissue during PORH, based on three parameters: two time constants (tau1 and tau2) and the ratio of the maximum flux and the resting flux. With these three constants quantitative comparisons between experiments will be possible and, therefore, we propose to adopt this approach as future standard. For this reason, we also developed a computer program to perform the fit of the model to measured data.

Laser Doppler perfusion monitoring (LDPM) is a noninvasive technique for monitoring skin microcirculation. The aim of this article was to investigate the influence of fiber separation on clinical LDPM measurements. A dual-channel LDPM system was used in combination with a probe that consists of two sets of detection fibers, at 0.2 and 1.0 mm from the illuminating fiber. Measurements were performed at the big toe of 8 healthy subjects and 11 subjects who had vascular disorders. In most cases, fluxes detected at both fiber distances showed very similar fluctuations. For each fiber separation, flux values of healthy subjects and patients were not significantly different. Furthermore, skin temperature (range: 22-34 degrees C) influenced the toe's pulp microcirculation markedly, increasing similarly at both probe separations, with a higher flux at a separation of 1.0 mm than at 0.2 mm. The flux ratio signal, obtained by dividing the flux at 0.2 mm by the flux at 1.0 mm, was significantly different between the two groups (p &< 0.05). In conclusion, the flux detected in vivo by means of LDPM, is influenced by the distance between the optical fibers. Use of the flux ratio with a multiseparation probe deserves attention as it is a possible marker for discriminating normal tissue perfusion from pathological skin tissue perfusion, independently from tissue temperature.

Laser Doppler flux signals show temporal fluctuations caused by physiological phenomena like heartbeat, respiration, and local variation of vascular tonus, vasomotion. This study investigates the influence of fiber arrangement, equipment and two probe locations on the variations in laser Doppler flux signals in five frequency bands in the absence of provocations. Two probes with detecting optical fibers at several distances from the illuminating source were used, as well as instruments from two manufacturers. The results show that normalization of the filtered flux signals with the mean flux leads to an enormous decrease of the influence of fiber distance. The difference between instruments is small after normalization. Some influence of probe location remains after normalization. Development of a standard method for normalization of the variations in laser Doppler signals is recommended.