Natural History of Perianal Fistulising Lesions in Patients With Elderly-onset Crohn's Disease: A Population-based Study

INTRODUCTION

Most studies of elderly-onset Crohn's disease [CD; diagnosed in patients aged 60 or over] have described a mild course. However, data on the natural history of perianal fistulising CD [pfCD] in this population are scarce. In a population-based cohort study, we described the prevalence, natural history, and treatment of pfCD in patients with elderly-onset CD vs patients with paediatric-onset CD.

METHOD

All patients diagnosed with CD at or after the age of 60 between 1988 and 2006, were included [n = 372]. Logistic regression, Cox models, and a nested case-control method were used to identify factors associated with pfCD.

RESULTS

A total of 34 elderly patients [9% of the 372] had pfCD at diagnosis. After a median follow-up of 6 years (interquartile range [IQR]: 3; 10), 59 patients [16%] had pfCD; the same prevalence [16%] was observed in paediatric-onset patients. At last follow-up, anal incontinence was more frequent in elderly patients with pfCD than in elderly patients without pfCD [22% vs 4%, respectively; p < 10-4]. Rectal CD at diagnosis was associated with pfCD: hazard ratio (95% confidence interval [CI] = 2.8 [1.6-5.0]). Although 37% of the patients received immunosuppressants and 17% received anti-tumour necrosis factor agents, 24% [14 out of 59] had a definitive stoma at last follow-up.

CONCLUSION

During the first 6 years of disease, the prevalence of pfCD was similar in elderly and paediatric patients. Rectal involvement was associated with the appearance of pfCD in elderly-onset patients. Around a quarter of patients with elderly-onset CD will have a stoma. Our results suggest that treatment with biologics should be evaluated in these patients.

Dramatic Increase in Incidence of Ulcerative Colitis and Crohn's Disease (1988-2011): A Population-Based Study of French Adolescents

OBJECTIVES

Few data are available to describe the changes in incidence of pediatric-onset inflammatory bowel disease (IBD). The aim of this study was to describe changes in incidence and phenotypic presentation of pediatric-onset IBD in northern France during a 24-year period.

METHODS

Pediatric-onset IBD (<17 years) was issued from a population-based IBD study in France between 1988 and 2011. Age groups and digestive location were defined according to the Paris classification.

RESULTS

1,350 incident cases were recorded (8.3% of all IBD) including 990 Crohn's disease (CD), 326 ulcerative colitis (UC) and 34 IBD unclassified (IBDU). Median age at diagnosis was similar in CD (14.4 years (Q1=11.8-Q3=16.0)) and UC (14.0 years (11.0-16.0)) and did not change over time. There were significantly more males with CD (females/males=0.82) than UC (females/males=1.25) (P=0.0042). Median time between onset of symptoms and IBD diagnosis was consistently 3 months (1-6). Mean incidence was 4.4/10⁵ for IBD overall (3.2 for CD, 1.1 for UC and 0.1 for IBDU). From 1988-1990 to 2009-2011, a dramatic increase in incidences of both CD and UC were observed in adolescents (10-16 years): for CD from 4.2 to 9.5/10⁵ (+126%; P<0.001) and for UC, from 1.6 to 4.1/10⁵ (+156%; P<0.001). No modification in age or location at diagnosis was observed in either CD or UC.

CONCLUSIONS

In this population-based study, CD and UC incidences increased dramatically in adolescents across a 24-year span, suggesting that one or more strong environmental factors may predispose this population to IBD.

Extra-intestinal Manifestations at Diagnosis in Paediatric- and Elderly-onset Ulcerative Colitis are Associated With a More Severe Disease Outcome: A Population-based Study

BACKGROUND AND AIMS

Data on extra-intestinal manifestations [EIM] and their impact on the disease course of ulcerative colitis [UC] in population-based cohorts are scarce, particularly in paediatric- and elderly-onset UC patients. The aims of this population-based study were to assess: 1] the occurrence of EIM in paediatric- and elderly-onset UC; 2] the factors associated with EIM; and 3] their impact on long-term disease outcome.

METHODS

Paediatric-onset [< 17 years at diagnosis] and elderly-onset UC patients [> 60 years at diagnosis] from a French prospective population-based registry [EPIMAD] were included. Data on EIM and other clinical factors at diagnosis and at maximal follow-up were collected.

RESULTS

In all, 158 paediatric- and 470 elderly-onset patients were included [median age at diagnosis 14.5 and 68.8 years, median follow-up 11.2 and 6.2 years, respectively]. EIM occurred in 8.9% of childhood- and 3% of elderly-onset patients at diagnosis and in 16.7% and 2.2% of individuals during follow-up [p < 0.01], respectively. The most frequent EIM was joint involvement [15.8% of paediatric onset and 2.6% of elderly-onset]. Presence of EIM at diagnosis was associated with more severe disease course [need for immunosuppressants or biologic therapy or colectomy] in both paediatric- and elderly-onset UC (hazard ratio [HR] = 2.0, 95% confidence interval [CI]: 1.0-4.2; and HR = 2.8, 0.9-7.9, respectively). Extensive colitis was another independent risk factor in both age groups.

CONCLUSIONS

Elderly-onset UC patients had lower risk of EIM either at diagnosis or during follow-up than paediatric-onset individuals. EIM at diagnosis predicted more severe disease outcome, including need for immunosuppressive or biologic therapy or surgery, in both paediatric- and elderly-onset UC.

Increased dopamine and serotonin metabolites in CSF during severe insulin-induced hypoglycemia in freely moving rats

The effect of insulin on dopamine (DA) and serotonin (5-HT) metabolites was determined in the cerebrospinal fluid (CSF) of the rat and compared with glucose levels in blood and CSF. CSF was continuously withdrawn from the third ventricle of freely moving rats at a constant rate of 1 ?l/min. Liquid chromatography with electrochemical detection was used for the direct assay of DA and 5-HT metabolites in the CSF. The metabolites were stable during the first hour after insulin injection (6IU/Kg). A progressive increase occurred thereafter in animals which had no access to food during the time of the experiment. The maximal effect was observed 2.5 h after insulin, with respective mean increases of 80% for dihydroxyphenylacetic acid, 47% for homovanillic acid and 33% for 5-hydroxyindolacetic acid. These increases in monoamine metabolites were not observed when rats received glucose (5g/Kg ip) 45 min after insulin or when food was made available. The period for insulin-induced increase in DA and 5-HT metabolites corresponded to a maximal fall of glucose levels both in blood and CSF although the CSF glucose decrease was delayed when compared to the fall of blood glucose. The role of brain glucose and brain insulin in the control of central DA and 5-HT metabolism is discussed.

[A new, spontaneous method for assessing sympathetic baroreflex function in humans]

In humans, assessment of the sympathetic component of the arterial baroreceptor reflex (sBRS) is usually based on microneurographic recordings of muscle sympathetic nerve activity (MSNA), while inducing reflex changes with intravenous administration of vasoactive drugs (modified Oxford method). This method has several limitations, among which its poor temporal resolution. Some studies have proposed alternative methods by using spontaneous changes in arterial pressure (AP) and MSNA, usually collected under baroreflex closed-loop conditions (AP alters MSNA while MSNA alters AP), which makes the results difficult to interpret. In rats, a method has been developed and validated (Kanbar et al., 2007 [1]), which uses oscillations of renal SNA at the frequency of the heart beat. At this frequency, the baroreflex operates under open-loop conditions because of the low-pass filter properties of the resistance vasculature. The goal of the present study was to examine whether this method is applicable in humans. Data were previously collected by Gujic et al. (2007) [2]. Briefly, MSNA and AP were recorded in 16 young healthy subjects during a 5-minute baseline resting period then during a modified Oxford test (sodium nitroprusside and phenylephrine administrations). Using the 5-minute baseline recordings, spontaneous sBRS was assessed through empirical mode decomposition over consecutive 20-second periods. Spontaneous sBRS was significantly related to pharmacological sBRS (R=0.67, n=16, P=0.004). During the 5-minute period, spontaneous sBRS exhibited variations (CV=21.7±1.7%) that were negatively correlated with AP in five subjects (R=-0.61±0.03, P<0.05) and positively correlated with MSNA in ten subjects (R=0.73±0.03, P<0.05). The new method is able to correctly estimate sBRS, and reveals the existence of previously unrecognized fast fluctuations of sBRS.

Arterial stiffness and the autonomic nervous system during the development of Zucker diabetic fatty rats

AIM

This study aimed to investigate the role played by sympathovagal balance in arterial stiffness, a common feature of insulin resistance and type 2 diabetes.

METHODS

We investigated the relationship between autonomic nervous system activity and arterial stiffness in Zucker diabetic fatty rats (ZDF: Gmi-fa/fa) and their age-matched controls (lean: ?/fa). Using simultaneous catheterization of the proximal and distal aorta, we measured intra-arterial blood pressure (BP), heart rate (HR), their variability (spectral analysis) and aortic pulse wave velocity (PWV) in a series of at least six conscious rats aged 6, 12, 18 and 24 weeks.

RESULTS

BP and PWV increased with age (P<0.001) in both strains with no differences between strains, despite the insulin resistance already present at 6 weeks in ZDF rats. HR was significantly lower (P<0.001) in ZDF than in lean rats. In ZDF compared with lean rats, the low-frequency (LF) component of the systolic BP variations and the LF/high-frequency (HF) component of the pulse interval (PI) variation ratio were reduced (P<0.01 and P<0.05, respectively), while the HF component of the PI (HF-PI) variation was raised (P<0.05). PWV was negatively correlated with HF-PI (r=-0.37, P<0.01), but not with biochemical parameters. HF-PI was an independent variable explaining the variation in PWV.

CONCLUSION

During the development of disease of ZDF rats, sympathovagal balance might account for the lack of increase in PWV.

[The best of hypertension in 2002]

This year, the writing of "Best of hypertension 2002" was completed by the coordinators of 4 working groups of the French Society of Hypertension, in various domains: (a) the working group on BAroreflex and VARiability (BAVAR): it appeared mandatory to evaluate the influence of calculation methods on the values of spontaneous baroreflex sensitivity, through an european study (The EuroBaVar collaboration study); (b) the working group on Blood Pressure Measurement, was first involved in the establishment of an international protocol for the validation of self blood pressure measurement, then validated, according to this procedure and in collaboration with the French Medicine Agency, several apparatus dedicated to the French market; (c) the working group on epidemiology: after the publication of the IHPAF study (Incidence de l'hypertension dans la population active française), which unmasked the influence of social and professional determinants on blood pressure control, this group settled down ancillary studies in French Indias, the INAPAG study (INcidence de l'hypertension artérielle dans la population Antilles-Guyane), and the PHAPPG study (Prévalence de l'hypertension artérielle dans la population précaire guadeloupéenne); finally (d) the working group for continuous medical education settled down a national diploma, entitled "Hypertension and renal and cardiovascular risk".

Non-invasive assessment of cardiovascular autonomic activity induced by brief exposure to 50% nitrous oxide in children

BACKGROUND

The use of the equimolecular mixture of oxygen and nitrous oxide is widely recommended for relief of pain in children undergoing minor procedures. Although the benefits and adverse effects of the clinical use of nitrous oxide seem well known, its effects on the autonomic nervous system have never been studied in children. The aim of this study was to evaluate changes in autonomic cardiovascular activity induced by brief exposure to 50% nitrous oxide in children. This study was based on non-invasive continuous recordings of RR-interval and non-invasive arterial pressure. Vascular and cardiac sympathetic activity and cardiac parasympathetic activity were investigated using spectral analysis of systolic arterial pressure variability (SAPV) and RR-interval variability (RRIV). In addition, the sensitivity of the spontaneous baroreflex (SBR) was assessed using the sequences and the cross-spectral analysis methods.

METHODS

Sixteen non-pre-medicated pre-pubertal children undergoing middle-ear surgery, were studied. Data analysis was performed at three points: baseline, when the end-tidal concentration of nitrous oxide was stabilized at 50%, and after withdrawing nitrous oxide. Low (0.04-0.14 Hz) and high frequency (0.2-0.6 Hz) components of the spectral power of RRIV and SAPV, and SBR sensitivity were calculated using these 2-min data epochs.

RESULTS

Our results show that brief exposure to 50% nitrous oxide in children results in: (1) absence of effect on mean AP and SAPV; (2) attenuation of the low frequency component of heart rate variability with a shift of the sympathetic-parasympathetic cardiac balance toward a parasympathetic predominance; and (3) absence of alteration of spontaneous baroreflex sensibility.

CONCLUSIONS

Unlike the results demonstrated in adults, our findings show very few cardiovascular effects of nitrous oxide in children. Furthermore, whereas in adults nitrous oxide is associated with an excitatory cardiovascular profile, in children this agent seems to be associated with a depressant cardiovascular profile. The rapid return to baseline after discontinuation of administration and the absence of baroreflex changes are positive attributes for the use of nitrous oxide in children.

Time- and frequency-domain estimation of early diabetic cardiovascular autonomic neuropathy

The risk related to cardiovascular autonomic neuropathy dysautonomia should lead to a specific assessment of this complication of diabetes. The aim of this study was to estimate the accuracy of a battery of blood pressure (BP) and heart rate (HR) variability indexes obtained in different subgroups of diabetic subjects classified according to the conventional laboratory autonomic function tests (Ewing scores). Blood pressure was measured continuously at the finger level with a Finapres monitor while subjects were in the supine position and again while they were standing. Pulse intervals were derived from BP recordings and were taken as surrogates for R-R intervals. Subjects with borderline or definite cardiovascular autonomic neuropathy showed a similar degree of alterations of both HR and BP variability (spectral measures) and in the relationship between BP and HR (cross-spectral and sequence analysis). Subjects with no evidence of cardiovascular autonomic neuropathy on the basis of the conventional tests showed an altered relationship between BP and HR. This baroreceptor-HR reflex dysfunction could represent an early stage of cardiovascular autonomic neuropathy undetected by the conventional tests. The areas under the receiver operating characteristic plots indicated that the high-frequency peak of pulse interval was highly discriminant in the supine and standing positions. The cross-spectral analysis showed the best discrimination for the gain in the high-frequency range. For the sequence analysis, the slope was the best discriminant factor for any degree of cardiovascular autonomic neuropathy. In conclusion, these estimates of baroreceptor-HR function may provide a powerful tool for assessing cardiovascular autonomic neuropathy at any stage, including the early stage, which is not detected by the conventional tests.

Genetic influences on cardiovascular responses to an acoustic startle stimulus in rats

1. The aim of the present study was to assess the cardiovascular differences among five inbred rat strains (n=16 per strain), including spontaneously hypertensive rats (SHR), Wistar Kyoto (WKY) rats, Wistar Furth (WF) rats, Fischer (F344) rats and Lewis (Lew) rats and the usual outbred Wistar (W) rat strain (n=25). 2. These strains were compared under resting conditions for blood pressure (BP) and heart rate (HR) levels and for their baroreceptor-HR reflex sensitivity. In addition, their responses to an acoustic startle stimulus were measured. 3. A consistent rise in BP was observed among the groups as a result of the noise stimulus. This rise in systolic BP (SBP) averaged (+/-SEM) 37 +/- 2 mmHg in the SHR and 34 +/- 4 mmHg in F344 rats, while the response was only 23 +/- 3 mmHg in WKY rats. Pulse pressure (PP) was increased following noise in all groups. The delay for the BP response for all groups combined was 1.6 +/- 0.1 s. 4. Most animals had minimal HR variations, except F344 rats, responding with a 42 +/- 13 b.p.m. decrease 3.0 s after the stimulus (i.e. 1.3 s after the maximal 34 +/- 4 mmHg SBP rise). 5. The highest SBP (160 +/- 3 mmHg) and diastolic BP (104 +/- 3 mmHg) were observed in inbred SHR. Other groups were normotensive. Resting PP was elevated for SHR (56 +/- 2 mmHg) compared with the other groups (40 +/- 2 mmHg). The highest HR was found in F344 and WF rats, with 389 +/- 11 and 372 +/- 7 b.p.m., respectively. The lowest HR was observed in SHR and Lewis rats, with 335 +/- 7 and 323 +/- 7 b.p.m., respectively. The least sensitive baroreflex function was observed in SHR (0.8 +/- 0.1 b.p.m./mmHg) compared with the other strains (1.4 +/- 0.2 b.p.m./mmHg). 6. The present study confirms the importance of genetic factors on the cardiovascular responses of rats to a noise startle stimulus. Two inbred normotensive rat strains, namely F344 and WKY rats, which exhibit a substantial difference in pressor response to noise, may be used to unravel the mechanisms of sympathetic activation.

Effects of drugs on the autonomic control of short-term heart rate variability

The autonomic nervous system links the brain and the heart. Efferent links in the neural control of the heart consist of sympathetic and parasympathetic (vagal) fibers innervating the sinus node. Because sympathetic and vagal firing alter spontaneous sinus node depolarization, cardiac rate and rhythm convey information about autonomic influences on the heart. The easy availability of ECG rendered possible the assessment of sinus rhythm as an index of autonomic outflow. The frequency-domain approach uses non-invasive recordings and appears to provide a quantitative evaluation of the autonomic modulation of cardiovascular function. Spectral profiles resulting from vagal or sympathetic blockades at the cardiac (or vascular) level might be used as references to unravel the mechanism of action of the drug under examination. A more comprehensive assessment will be obtained if spectral analysis is used as a complement to existing techniques applied for describing the neurohumoral status of patients (microneurographic recordings, norepinephrine spillover). This review also reports some pitfalls encountered in variability studies.

Effects of carbodiimide crosslinking conditions on the physical properties of laminated intestinal submucosa

Functional tissue engineering of load-bearing repair tissues requires the design and production of biomaterials that provide a remodelable scaffold for host infiltration and tissue regeneration while maintaining the repair function throughout the remodeling process. Layered constructs have been fabricated from chemically and mechanically cleaned porcine intestinal collagen using ethyl-3(3-dimethylamino) propyl carbodiimide (EDC) and an acetone solvent. By varying the concentration of the crosslinker from 1 to 10 mM and the solvent from 0 to 90% acetone, the strength, stiffness, maximum strain, thermal stability, lamination strength, and suture retention strength can be adjusted. These parameters have either functional importance or the potential to modify the remodeling kinetics, or they have both. This study investigates the interdependence of these parameters, the specific effects that variations in concentration can achieve, and how the two crosslinking variables interact. The results demonstrate that there is substantial latitude in the design of these constructs by these straightforward crosslinking modifications. These data provide the basis for studying the in vivo response to crosslinking conditions that will supply the requisite strength while still allowing host cell infiltration and remodeling.

Intense endurance training on heart rate and blood pressure variability in runners

Physical training with incomplete recovery times can produce significant fatigue. A study of cardiovascular responses showed that there is a sympathetic and a parasympathetic form of fatigue.

PURPOSE

The purpose of this experimentation was to measure the effects of intense endurance training on autonomic balance through a spectral analysis study of the heart rate (HR) and systolic blood pressure (SBP).

METHODS

Eight elite runners were tested twice: after a relative rest period (RRP) of 3 wk and after an 12-wk intense training period (ITP) for endurance. At the end of each phase, the subjects were tested by means of a VO2max test and a tilt-table test.

RESULTS

The resting heart rate (HR) variability was lower (P < 0.001) in the intensive training phase. Likewise, there were differences in the low-frequency (0.04-0.150 Hz; LF) and high-frequency (0.150-0.500 Hz; HF) components and the LF/HF ratio of the HR spectral analysis. The LF spectral power was significantly lower in the supine position (P < 0.05) during ITP. Upright tilting was accompanied by a 22.6% reduction in HF values during the rest period, whereas in ITP the HF spectral power rose by 31.2% (P < 0.01) during tilt, characterizing a greater parasympathetic system control. Sympathetic control represented by the LF/HF ratio regressed markedly (P < 0.01) in response to the tilt test in ITP.

CONCLUSIONS

The spectral analysis of SBP in the high frequencies shows that the changes in cardiac parameters are coupled with a decrease in sympathetic vasomotor control (-18%) and a reduction in diastolic pressure (-3.2%) in the response to the tilt test at the end of ITP. Spectral analysis could be a means of demonstrating impairment of autonomic balance for the purpose of detecting a state of fatigue that could result in overtraining.

Effects of aerobatics flight on oxygen consumption and heart rate control: influence on autonomic cardiovascular regulation during recovery

Oxygen consumption (VO2) and blood pressure regulation were measured on five pilots during and after normal training aerobatics flights of a mean duration of 35 min. The acceleration vector along the longitudinal axis of the body (Gz) ranged from + 6.5 Gz to -3.5 Gz. VO2 was continuously monitored by a miniature telemetric system (K2). Heart rate (fc), the abdominal muscle electromyogram (EMG) and Gz levels were recorded synchronously on a magnetic tape recorder. A tilt test was performed pre- and post-flight to evaluate fc and blood-pressure variability. The left forearm blood flow was measured by strain-gauge plethysmography. The mean VO2 during flight was 1.2 l x min(-1), with a peak VO2 of 2.1 l x min x fc ranged between 55 and 165 beats x min(-1) and showed a progressive increase under the effect of + Gz, with a sudden fall during -Gz. The abdominal muscle EMG indicated the occurrence of muscle contraction under Gz load. Maximal responses were observed during the Gz phase. Comparison between pre- and post-flight data showed lower post-flight systolic blood pressure with higher fc. Before flight, upright tilt induced a significant increase in low/ high frequency fc, as assessed using spectral analysis. This change was suppressed after flight. In summary, these data show that aerobatics flight leads to enhanced energy expenditure, mainly because of increased skeletal muscle work. The post-flight tilt test showed that aerobatic flight favors parasympathetic drive and, consequently, modifies blood pressure regulation during recovery. This action may decrease + Gz tolerance to a second aerobatics flight performed shortly after the first.

Assessment of autonomic cardiovascular changes associated with recovery from anaesthesia in children: a study using spectral analysis of blood pressure and heart rate variability

Recovery from anaesthesia is associated with large changes in cardiovascular autonomic activity, which are poorly documented in children. This study was undertaken to investigate the cardiovascular autonomic activity in anaesthetized and recovering children, using a noninvasive approach based on spectral analysis of heart rate (HR) and blood pressure (BP) variability. Ten children (aged 5-13 years) undergoing major surgery were studied. Continuous HR and BP were recorded using a noninvasive device during deep anaesthesia and recovery. Spectral analysis was used to determine the main oscillatory components of HR and BP signals. For each power spectrum, the frequency components were identified as follows (i): the low frequency (LF) component (0.04-0.14 Hz) both parasympathetically and sympathetically mediated for HR and corresponding to vasomotor sympathetic modulation for BP; and (ii) the high frequency (HF) component (0.2-0.6 Hz) parasympathetically mediated for HR, and reflecting mechanical influence of ventilation on cardiac output for BP. In addition, the LF : HF ratio for HR, reflecting the cardiac sympathovagal balance, was calculated. Under deep anaesthesia, HR variability and BP variability were very low and mainly due to mechanical influence of intermittent positive pressure ventilation. Conversely, the recovery period was associated with a marked increase of HR and BP overall variability. Compared to anaesthesia, spectral analysis of HR and BP revealed that the LF component of BP and HR spectra increased 40-fold during recovery; the LF : HF ratio of HR was also increased during recovery (0.1 +/- 0.1 versus 1.3 +/- 1.2, P=0.008). The results of this study demonstrate that the recovery period is associated with an increase of cardiovascular sympathetic drive in children after major surgery.

Relationship between pulse interval and respiratory sinus arrhythmia: a time- and frequency-domain analysis of the effects of atropine

Respiratory sinus arrhythmia (RSA) estimation is commonly used as a non-invasive index of cardiac vagal tone. To test this relationship, vagal tone was augmented or blocked using atropine. The study was carried out using 14 healthy volunteers, following beta-adrenoceptor blockade (10 mg bisoprolol per os) and during controlled respiration (0.25 Hz) in order to limit the confounding effects of cardiac sympathetic tone and respiration pattern changes. Atropine was slowly infused intravenously over a 30-min period up to a vagolytic cumulative dose of 0.04 mg/kg. The instant vagal tone was compared to the instant RSA value obtained from a time-/frequency-domain analysis of pulse interval (PI). RSA and PI varied in the same direction with an initial increase corresponding to the early vagomimetic effect of atropine followed by a decrease during the vagolytic phase. The comparative percentage fluctuations of RSA and PI over this large vagal tone range indicate that RSA is more sensitive (about twofold) than PI in reflecting fluctuations around the set point. This dissociated behaviour of PI and heart rate variability could be important to our understanding of the circulatory changes that result from fluctuations in vagal inputs to the sinus node.

Central ring electrode for trapping and excitation/detection in Fourier transform ion cyclotron resonance mass spectrometry

The use of a central trapping ring electrode for Fourier transform ion cyclotron resonance (FTICR) mass spectrometry is demonstrated. Ions are trapped with an oppositely biased static potential superimposed on both the excite and detect electrodes and maintained throughout the experiment, including the application of a dipolar rf excite waveform and the image current ion detection event. The use of a central trapping electrode for FTICR coupled with an open cell design retains the advantages of high ion throughput and gas conductance, while simplifying the electrode geometry and reducing the overall dimensions of the cell. This allows the central trapping electrode to be of utility in volume-limited vacuum chambers including FTICR instrument miniaturization. Presented here are the preliminary experimental results using the central trapping electrode as an FTICR cell in which the excitation and detection electrodes also create a trapping depression to constrain the z-axis motion of the ions. The cell overcomes the principle limitation of an earlier single trapping electrode design by producing a 91% effective potential well depth compared to 19% for the single trapping electrode and 33% for standard open cells. This allows the central trapping electrode configuration to achieve an order of magnitude improvement in ion capacity compared to more conventional open cell designs.

Antihypertensive monotherapy and cardiovascular responses to an acoustic startle stimulus

To determine contribution of the autonomic nervous system to cardiovascular reactivity to noise, acoustic startle stimulus (110 dB, 1-20 kHz, 0.150 s) was administered to 35 subjects (19 women, 16 men) with mild essential hypertension. Among these patients, 10 were unmedicated and 25 were receiving long-term monotherapy (10 were taking 100 mg atenolol, 5 were taking 10 mg prazosin, and 10 were taking 50 mg losartan daily). Polygraphic recordings were obtained in supine position. Blood pressure (BP) and heart rate (HR) levels were stable until the noise was administered. In the unmedicated group BP and HR were elevated during the first 10 s. BP returned to resting levels after this period. The calculated hemodynamic indexes showed a biphasic change in total peripheral resistance (TPR), with an overall vasoconstriction associated with the BP rise phase, preceding a delayed vasodilation. The lowest HR changes were observed in the beta-blocker group with increases of 6 beats/min and 3 beats/min after the first and second noise stimulations, compared with 10 beats/min and 5 beats/min in the unmedicated group. Prazosin significantly reduced the BP rises to 7 mm Hg and 6 mm Hg for systolic BP and diastolic BP after the first stimulation compared with 22 mm Hg and 17 mm Hg in the untreated group (p < 0.01). The second stimulation after prazosin determined -5 mm Hg and 1 mm Hg changes for systolic BP and diastolic BP respectively, compared to rises of 13 mmHg for systolic BP and 10 mmHg for diastolic BP in the untreated group (p < 0.01). The hemodynamic percentage changes resulting from the first stimulation indicated prazosin markedly reduced the noise-induced rise in TPR (p < 0.05). No effect of beta-blocker was detectable using percentage changes. The rises in BP were amplified in the losartan-treated subjects compared with the other groups. Because of a low resting TPR in this group, the percentage changes in TPR resulting from noise were amplified in the subjects treated with the AT1 receptor antagonist. In conclusion the acoustic startle stimulus appeared as a simple and reliable procedure for inducing transient increases due to a rise in TPR. Cardiovascular responses differed according to the antihypertensive monotherapy, with a limited effect of noise in the prazosin-treated group.

A novel injectable collagen matrix: in vitro characterization and in vivo evaluation

We present here a unique engineered collagen formulation that is injectable and compacts into a porous viscoelastic solid after implantation, achieving completely focal application without cross-linking. This implant provides a cohesive continuously porous matrix, as demonstrated by permeability and compression experiments. Those experiments also provide initial mechanical characterization of the material and establish the ability to modify these essential properties by design. Further, the short-term compaction and long-term stability of the implant in vivo in terms of both physical and histological responses are assessed in an animal model to demonstrate the mechanism of action and long-term persistence of this novel material.

Magnetic field focused ion accumulation for an internal bore liquid chromatography electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer using a central trapping electrode

Presented is the application and evaluation of a magnetic field focusing central trapping electrode ion accumulation cell for a capillary liquid chromatography electrospray Fourier transform ion cyclotron (LC-ESI/FTICR) mass spectrometer. The ESI source and accumulation cell are located within the magnetic field to confine the radial motion of the ions, eliminating the need for elaborate focusing optics to transport the ions to the low-pressure analyzer cell for analysis. The central trapping electrode accumulation cell increases sensitivity by providing the necessary potential well in a confined volume to capture ions currently lost during the detection event of LC/FTICR experiments. With this electrode geometry the time needed to gate the ions into the analyzer cell is reduced and pump down delays are minimized. The decreased scan time improves LC resolution and increases the number of mass spectral scans per eluted component while maintaining appropriate base pressures for high performance ESI/FTICR. Results achieved with the central trapping electrode accumulation cell include an effective duty cycle increase from 10% to 40%, a S/N increase by a factor of 30, and a mass resolution increase of 80%.

Early detection of cardiovascular autonomic neuropathy in diabetic pigs using blood pressure and heart rate variability

Cardiac autonomic neuropathy is a common complication in insulin dependent diabetes mellitus. Nevertheless, little is known about when this impairment occurs during the time course of the disease. Analysis of blood pressure (BP) and heart rate (HR) variability could be used to detect early signs of autonomic alteration. To test this proposal, twelve sexually mature male Yucatan miniature pigs were equipped with an arterial catheter for telemetric BP analysis, and with a venous access. BP and HR were recorded together with respiratory movements while the animals were resting in a sling. After the first recording session performed when the pigs were 5 months old, streptozotocin (STZ) was used to induce diabetes in seven pigs, while the five others were controls. BP and HR were measured 3 and 6 months after the onset of diabetes and at a similar age in the controls. BP and HR oscillated at the respiratory range (0.19 Hz). Spectral analysis showed this respiratory component was the main determinant of the short-term variability of BP and HR. Atropine increased HR and BP and markedly diminished the respiratory sinus arrhythmia. Propranolol diminished HR and the respiratory peak of HR. A reduced respiratory oscillation of BP paralleled the diminution of the respiratory peak of HR. Baroreceptor-HR reflex was estimated using injections of phenylephrine and nitroprusside, and by cross-spectral analysis between BP and HR. Atropine shifted the curve to higher HR values, while propranolol reduced the level of the upper plateau. Atropine decreased both the coherence and gain of the cross-spectral analysis. STZ injection resulted in a type 1 diabetes. At 3 months, diabetic pigs exhibited low levels of BP and a reduced overall variability of HR and BP. Spectral analysis indicated the respiratory sinus arrhythmia was markedly reduced. In addition, the sensitivity of the baroreceptor-HR reflex was reduced. At a latter stage of diabetes these alterations were marked and the level of the resting HR was increased. These data demonstrate the dual (vagal and sympathetic) control of HR in pigs and the dominant role of respiration in the genesis of HR and BP fluctuations. The spectral and cross-spectral analysis of BP and HR were altered after 3 months of diabetes and could be proposed as early detectors of cardiac autonomic neuropathy.

Effects of an auditory startle stimulus on blood pressure and heart rate in humans

OBJECTIVE

To describe the effects of an auditory startle stimulus on blood pressure (BP) and heart rate (HR) in humans.

DESIGN AND METHODS

Twenty-five volunteers, including nine untreated hypertensive subjects, were studied in the supine position. Polygraphic recordings were obtained for finger BP, R-R interval using ECG, respiratory movements using a thoracoabdominal belt and for electrooculomyogram using adhesive electrodes. Haemodynamic estimations were derived by modelling flow from the noninvasive BP signal. A background noise of 55 dB was administered through headphones and two acoustic startle stimuli (110 dB, 1-20 kHz, 0.15 s) were generated at 5-min intervals during the tele-expiratory phase. The sham stimulation (0 dB, event marker) was compared with the effects of the noise stimulus (one-way ANOVA with repeated measures followed by a protected t test for multiple comparisons).

RESULTS

A biphasic cardiovascular profile was observed in response to noise stimulation. Blood pressure and HR increases were combined in the early response (0-10 s) observed after the immediate motor contraction (blink). The average systolic BP rise was 18.7+/-2.7 mmHg (peak at 5.1 s) and the average HR increase was 10.8+/-1.1 bpm (peak at 3.4 s) for the first stimulus. These effects were highly significant compared with the sham response (P < 0.01). The second stimulus elicited BP and HR rises of a lesser amplitude (P < 0.01). The delayed response (10-30 s) corresponded with a moderate BP decrease. The haemodynamic indexes suggest that the early rise in blood pressure reflects a rise in total peripheral resistance.

CONCLUSION

This is the first description of the BP response to an acute loud noise in humans. The early (within 10 s) BP and HR rises may depend upon the autonomic component of the startle reflex. One application of this test could be the discrimination of the different classes of antihypertensive drugs according to their sites of action.

Blood pressure variability in established L-NAME hypertension in rats

METHODS

Blood pressure variability was evaluated in conscious Wistar control rats and rats with established L-NAME hypertension (20 mg/kg per 24 h, 4 weeks).

RESULTS

Final systolic arterial pressure was 185+/-5 and 132+/-4 mm Hg in the Nomega-nitro-L-arginine methyl ester (L-NAME)-treated and control rats, respectively. The standard deviation of systolic arterial pressure in the L-NAME group was 70% greater than in the control rats, indicating a significant increase in the overall variability. Arterial pressure in the L-NAME rats exhibited aperiodical, abrupt rises and falls and data was grossly non-stationary. Blood pressure variability was therefore evaluated using Poincaré plot analysis. The variance of the difference (delta) between two successive values of systolic arterial pressure, determined for time intervals of 0.2 to 5 s (0.2 s increment), was always significantly higher in the L-NAME group compared with untreated animals. The variance of delta systolic arterial pressure increased with the time interval and plateaued for time intervals of 2.4 and 1.4 s in hypertensive and normotensive rats, respectively. These differences vanished when the sudden events oberved in L-NAME rats were omitted in the construction of Poincaré plots. Acute administration of prazosin (1 mg/kg), but not losartan (10 mg/kg) markedly reduced the variance of delta systolic arterial pressure in hypertensive rats.

CONCLUSIONS

Nitric oxide participates in the control of arterial pressure variability. The sympathetic nervous system seems to be a major determinant of the increased short-term variability of arterial pressure in this model.

Pulse rate variability is not a surrogate for heart rate variability

To investigate the differences between heart rate (HR) variability and pulse rate (PR) variability, short-term variability of finger pulse wave and ECG signals were studied in 10 children with a fixed ventricular pacemaker rhythm (80 beats/min). Ten healthy children in sinus rhythm served as a reference population. Distal PR and HR were measured continuously using a Finapres device and an ECG respectively. Power spectra for HR and PR were calculated in both the supine and orthostatic positions. In paced subjects, PR spectra exhibited the characteristic respiratory peak, although the HR spectra were flat. Similarly, in healthy children the respiratory fluctuations were more pronounced when calculated from the finger pulse wave signal compared with the ECG signal. The overestimation of HR respiratory fluctuation resulting from distal PR measurement was more pronounced in the standing position; however, this postural effect was demonstrated only in healthy subjects. We observed mechanical respiratory modulation of distal PR independent of classical HR modulations. Our results suggest a mechanical respiratory influence via cardiac output and aortic transmural pressure changes on pulse wave velocity. We conclude that respiratory PR variability does not precisely reflect respiratory HR variability in standing healthy subjects and in patients with low HR variability. Consequently, HR modulation should be studied using the ECG signal rather than the distal pulse wave signal. However, when ECG recording is not available, the distal pulse wave is an acceptable alternative.

Short-term variability of blood pressure and heart rate in Guillain-Barré syndrome without respiratory failure

The effect of Guillain-Barré syndrome (GBS) on the short-term variability of blood pressure and heart rate was evaluated in six patients presenting with a moderate form of the syndrome, i.e. unable to stand up unaided and without respiratory failure, at the height of the disease and during recovery. The patients were compared with six age-matched healthy volunteers. During the acute phase of the syndrome, GBS patients exhibited a significant heart rate elevation (+26 beats/min compared with healthy subjects), but the acceleratory response to atropine, or to 60 degrees head-up tilt, was maintained. Resting plasma noradrenaline levels were high in acute GBS, but the secretory response to tilt was preserved. Desensitization to noradrenaline was observed in acute GBS with a reduced pressor action of this alpha-adrenoceptor agonist. Blood pressure levels were normal and head-up tilt did not induce orthostatic hypotension in this moderate form of GBS. Power spectral analysis demonstrated marked alterations in cardiovascular variability. The overall heart period variability was markedly reduced with the reduction predominantly in the high-frequency (respiratory) range (-73%). The low-frequency component of heart period variability was also reduced (-54%). This cardiovascular profile of moderate GBS at the height of the disease could result from a demyelination of the reflex loop controlling respiratory oscillations in heart rate and from a desensitization of the arterial tree to an elevated plasma noradrenaline. Sympathetic nervous activation may contribute to the high resting heart rate in acute GBS.

Assessment of short-term blood pressure variability in anesthetized children: a comparative study between intraarterial and finger blood pressure

OBJECTIVE

Continuous blood pressure (BP) measurement provides instantaneous information on hemodynamic status, and allows for assessment of sympathetic modulation of vasomotor tone using spectral analysis. As an alternative to intraarterial blood pressure (IABP) measurement, the Finapres, a photoplethysmographic device, allows for non-invasive continuous measurement of finger blood pressure (FBP). This study was designed to evaluate the accuracy of spectral measurements of FBP variability in children during anesthesia and recovery. For this purpose, reliability of BP measurement and short-term BP variability assessed by FBP were calculated and compared with IABP.

METHODS

Finger blood pressure was compared with IABP from the ipsilateral radial artery, in 14 children undergoing major surgery. Sixty-seven simultaneous recordings of both signals were performed during anesthesia and 32 during recovery period. The accuracy of the FBP was determined by measuring its bias and precision according to the Bland and Altman method. To assess the ability of the FBP to follow short term BP variability, bias of total spectral power and bias of the 3 main spectral components (LF, MF, HF) were calculated. Transfer functions between invasive and non-invasive signals were calculated.

RESULTS

The average bias of SBP measurement was 3.8 +/- 7.4 mmHg during anesthesia and 2.2 +/- 6.7 mmHg during recovery. During anesthesia overall variability and spectral components of FBP and IABP were similar with both techniques; while during recovery, a selective amplification of the low frequencies (< 0.15 Hz) of FBP was observed. Frequency response analysis of the pressure waveform, showed a high coherence between both signal with a gain of 0.96 +/- 0.52 mmHg FBP/ mmHg IABP under anesthesia, and of 0.74 mmHg FBP/ mmHg IABP during recovery.

CONCLUSIONS

The differences evidenced between FBP and IABP spectral profiles might result from specific physiological properties of digital arteries, which are sympathetic effectors. This study supports the use of FBP in children to assess non-invasively the vascular sympathetic component of the autonomic nervous system during anesthesia and recovery.

Autonomic contribution to the blood pressure and heart rate variability changes in early experimental hyperthyroidism

OBJECTIVE

To study the interaction between autonomic nervous activity and thyroid hormones in the control of heart rate (HR) and blood pressure (BP).

DESIGN AND METHODS

Thyrotoxicosis was produced by injections of L-thyroxine (0.5 mg/kg/day for five days). Blockers were atropine (0.5 mg/kg), atenolol (1 mg/kg) or prazosin (1 mg/kg). Eight animals were studied in each group. Spectral analyses was performed using continuous BP time series obtained in conscious rats.

RESULTS

Thyroxine treatment was sufficient to induce a significant degree of tachycardia (423+/-6 vs 353+/-4 bpm, P < 0.001, unpaired Student's t test), systolic BP elevation (142+/-3 vs 127+/-2 mmHg, P < 0.001) and cardiac hypertrophy (1.165+/-0.017 vs 1.006+/-0.012 g, P < 0.001). The intrinsic HR was markedly increased after treatment with thyroxine (497+/-16 vs 373+/-10 bpm, P < 0.05). Vagal tone was positively linearly related to intrinsic HR (r = 0.84, P< 0.01). Atenolol neither modified HR nor BP variability in rats with hyperthyroidism. The thyrotoxicosis was associated with a reduction of the 0.4 Hz component of BP variability (modulus 1.10+/-0.07 vs 1.41+/-0.06 mmHg, P < 0.01). Prazosin was without effect on this 0.4 Hz component in hyperthyroid animals.

CONCLUSIONS

These data show a functional diminution of the vascular and cardiac sympathetic tone in early experimental hyperthyroidism. The marked rise in the intrinsic HR could be the main determinant of tachycardia. The BP elevation may reflexly induce vagal activation and sympathetic (vascular and cardiac) inhibition.

Acute effects of bisoprolol on respiratory sinus arrhythmia

Respiratory sinus arrhythmia (RSA) is often quantified by computing the spectra of heart period (HP) or of its reciprocal heart rate (HR) at the respiratory frequency. This study was undertaken to describe the effect of an acute beta-blockade achieved with bisoprolol on RSA, obtained during a calibrated breathing (breathing frequency 0.25 Hz, tidal volume VT 500 or 700 mL) in 15 normal volunteers, using a double-blind, placebo-controlled, cross-over method. The two heart signals were computed and the RSA values were compared to the individual estimates of vagal tone obtained using an additional atropine injection. The difference between the HP (or HR) value obtained after beta-blockade and the HP (or HR) value observed following the double blockade (bisoprolol plus atropine) was taken as an index of cardiac vagal tone. Bisoprolol administration resulted in a significant reduction in HR reaching 60.3 +/- 1.4 bpm at VT of 500 mL (compared to 70.5 +/- 1.8 bpm with placebo, P < 0.001). Changes in HP were also significant with an increase in HP reaching 1004.5 +/- 22.2 msec at this controlled VT (compared to 860.3 +/- 21.5 msec with placebo, P < 0.001). Similar changes were observed at a VT of 700 mL. The relationship between RSA in bpm and vagal tone was not significant for HR while a significant positive relationship was observed between RSA in msec and vagal tone for the two respiratory patterns (r = 0.65 for a tidal volume of 500 mL, P < 0.01, and r = 0.62 for 700 mL, P < 0.05). This demonstrates that the detection of the variability effect highly depends upon the unit. The parallelism between vagal tone and RSA supports the view that the HF component of HRV in msec quantifies the vagal tone. The increased RSA during beta-blockade could well reflect this vagotonic effect of this class of drugs.

Contribution of the autonomic nervous system to blood pressure and heart rate variability changes in early experimental hyperthyroidism

A great deal of uncertainty persists regarding the exact nature of the interaction between autonomic nervous system activity and thyroid hormones in the control of heart rate and blood pressure. We now report on thyrotoxicosis produced by daily intraperitoneal (i.p.) injection of L-thyroxine (0.5 mg/kg body wt. in 1 ml of 5 mM NaOH for 5 days). Control rats received i.p. daily injections of the thyroxine solvent. In order to estimate the degree of autonomic activation in hyperthyroidism, specific blockers were administered intravenously: atropine (0.5 mg/kg), prazosin (1 mg/kg), atenolol (1 mg/kg) or the combination of atenolol and atropine. A jet of air was administered in other animals to induce sympathoactivation. Eight animals were studied in each group. The dose and duration of L-thyroxine treatment was sufficient to induce a significant degree of hyperthyroidism with accompanying tachycardia, systolic blood pressure elevation, increased pulse pressure, cardiac hypertrophy, weight loss, tachypnea and hyperthermia. In addition, the intrinsic heart period observed after double blockade (atenolol + atropine) was markedly decreased after treatment with L-thyroxine (121.5+/-3.6 ms vs. 141.2+/-3.7 ms, P < 0.01). Of the autonomic indices, vagal tone (difference between heart period obtained after atenolol and intrinsic heart period) was negatively linearly related to intrinsic heart period (r = 0.71, P < 0.05). Atenolol modified neither the heart period nor blood pressure variability in rats with hyperthyroidism and in these rats the jet of air did not significantly affect the heart period level. The thyrotoxicosis was associated with a reduction of the 0.4 Hz component of blood pressure variability (analyses on 102.4 s segments, modulus 1.10+/-0.07 vs. 1.41+/-0.06 mm Hg, P < 0.01) and prazosin was without effect on this 0.4 Hz component in these animals. These data show a functional diminution of the vascular and cardiac sympathetic tone in early experimental hyperthyroidism. The marked rise in the intrinsic heart rate could be the main determinant of tachycardia. The blood pressure elevation may reflexly induce vagal activation and sympathetic (vascular and cardiac) inhibition.

Heart rate control of blood pressure variability in children: a study in subjects with fixed ventricular pacemaker rhythm

1. To investigate the influence of heart rate variability on blood pressure variability, short-term variability in heart rate and blood pressure was studied in 10 children with fixed ventricular pacemaker rhythm (80 beats/min). Ten healthy children, in sinus rhythm, served as a reference population. 2. Arterial blood pressure and heart rate were measured continuously using a finger arterial device and an ECG respectively. Power spectra for heart rate and blood pressure (systolic and diastolic) were calculated in both supine and orthostatic positions. In addition, acute changes in blood pressure and heart rate during active standing were studied. 3. Healthy children exhibited considerable heart rate variability, which was slightly more pronounced in the supine position, while children with a fixed ventricular rate had no heart rate variability in either position. 4. Despite the differences in heart rate variability, mean systolic blood pressure and its variability profiles were poorly affected by the suppression of heart rate variability. The lack of autonomic control on the sinus node was associated with a reduction in magnitude of the changes in systolic blood pressure variability induced by orthostatic posture. 5. The suppression of heart rate fluctuations induced a noticeable decrease in diastolic blood pressure fluctuations, which was most conspicuous in the children with fixed cardiac rhythm when in the supine position. This may be explained by the lack of diastolic blood pressure fluctuations, physiologically due to heart rate fluctuations through the run-off effect: the longer the cardiac cycle, the greater the diastolic pressure decay. These results may challenge the classical theory of baroreflex-mediated diastolic blood pressure control described in adult patients. 6. During active standing, the early drop in systolic blood pressure was greater in subjects with fixed ventricular rhythm. A rise in heart rate of 36 beats/min was observed in the healthy subjects in response to active standing. 7. We conclude that in normal children, heart rate fluctuations increase the blood pressure variability rather than buffering it. However, during acute orthostatic stress, the abrupt baroreflex-mediated heart rate rise may partly compensate for the reduction in blood pressure.

[Short-term variability of blood pressure]

The regulation of blood pressure (BP) is traditionally described in terms of homeostasis, and indicates that BP although being continuously perturbed by external stimulations always displays the tendency to come back toward a reference set point. Experimental and clinical studies indicate that these fluctuations occurring around the average present a source of complementary information on the mechanism of cardiovascular control. Recently a wide variety of algorithm and models have been proposed to study the cardiovascular system through new technics of continuous non invasive BP or heart rate (HR) measurements. They give new insites for the evaluation of hypertensive patients and relevance to the understanding of the role of the disorder of the tonic regulation of BP, rather than its short-term variability or reactivity. However, if available data unequivocally indicate that the analysis of variability is a useful tool, the interpretation of those data in clinical trials is not always optimal because there is lot of interaction between BP, HR and other biological signals, and furthermore the use of laboratory data introduces problems to predict what happens on daily life ambulatory conditions.

Anger expression and cardiovascular reactivity to mental stress: a spectral analysis approach

The cardiovascular reactivation to a recently described videogame task i.e. a maze test was evaluated in the time and frequency-domain using finger blood pressure (BP) measurement in 25 subjects on no medication, including 6 subjects with mild hypertension. Prior to BP measures subjects completed the items of the State-Trait Anger Expression Inventory questionnaire corresponding to the trait anger and anger expression scales. The BP recording session was divided into resting, test and recovery periods. A detrending procedure was applied to each recording prior to the fast Fourier transform. Systolic BP (SBP) and heart rate (HR) were increased during the test. The mid-frequency (MF, 0.1 Hz) components of SBP and HR variability were also elevated during the stressful period. In resting conditions SBP levels of subjects with low trait anger was lower than in subjects with high trait anger (128 +/- 4 mmHg, n = 14 versus 148 +/- 4 mmHg, n = 11, P < 0.01, Student t test). Nevertheless the average SBP increase due to the stress was of similar magnitude in these two subgroups (14 mmHg). A significant negative relationship was observed between anger-out expression score and the MF SBP variation (r = 0.46, P < 0.05). A significant negative relation was found between anger-in mode of expression and the HR peak during the test (r = 0.43, P < 0.05). In conclusion, our data suggest that individuals who are often in anger-provoking situations (high trait anger) should have heightened BP. Two different patterns of cardiovascular responses (SBP variability and HR levels) were observed for the outward and inward mode of expression of anger. This may reflect a different psychological control of HR levels and BP variability.

[Spectrum analysis of heart rate and arterial systolic pressure after heart transplantation in children]

The aim was to examine the short-term variability of blood pressure (BP) and heart rate (HR) in 19 children who had received heart transplants and in 8 normal control children. BP was determined by a finger arterial pressure device. We examined the power spectra for HR and systolic blood pressure (SBP) in the supine and standing posture. In the transplanted children we could distinguish two groups (groups A and B) in whom HR variability differed, though in both it was greatly reduced compared to controls (group C). In group A there were no significant fluctuations in the mid frequency (MF) range for HF. Gain of the relationship between SBP and HR was very low and there were virtually no HR changes associated with passive tilting. By contrast, in group B transplant patients the HR variability, as assessed by standard deviation was about half that of normal controls. The power spectra attenuation was greater in the high frequency (HF) than in the MF bands. On standing the latter became enhanced, but not the HF variability. The findings suggest some reinnervation involving cardiac sympathetic fibres to a greater degree than the fast-responding vagal fibres. Time since operation was a critical factor for reinnervation since all subjects from group B were transplanted more than 44 months prior to the recording. We conclude that in a proportion of children who have received heart transplantation there is a delayed reinnervation of the heart, which probably involves sympathetic effectors rather than the vagus.

Effect of autonomic blockade on heart rate and blood pressure in sleep apnea syndrome

To determine the impact of the autonomic nervous system on hemodynamic responses to sleep apnea we studied 7 male patients (48 +/- 6 years, BMI = 29.7 +/- 2.9 kg/m2) with an apnea index = 33 + 11/h. In two hypertensives, therapy was withdrawn 2 weeks before the study. During a full night polysomnography EEG, EOG, EMG, respiration, oximetry, heart rate (HR) and blood pressure (BP) (Finapres 23OOE) were recorded. Placebo and 3 short-acting autonomic blockers were randomly i.v. administered: antimuscarinic (atropine 1 mg, A), beta 1 blocker (esmolol 40 mg, E), alpha blocker (nicergoline 2.5 mg, N). A total of 367 obstructive apneas in NREM sleep were studied. With atropine, HR was increased at the beginning of apnea (P1)(74.5 +/- 2 bpm vs 65.4 +/- 2 bpm with placebo) and at the end apnea (P3) (76.6 +/- 1.9 bpm vs 67.1 +/- 1.76 bpm). At the resumption of breathing (RB), HR still increased (83.5 +/- 1.5 bpm vs 80.1 +/- bpm). Nicergoline had no significant effect on HR but significantly decreased SBP (117.8 +/- 1.4 mmHg vs 127 +/- 1.6 with placebo, p < 0.001). Nevertheless, the rise in BP from P3 to RB remained significant (p < 0.001). Esmolol significantly decreased HR at P1 (68.1 +/- 1.9 bpm vs 73.9 +/- 1.9 bpm) and at RB (75.9 +/- 1.9 vs 81.6 +/- 1.8). With A, the rise in HR at end-apnea (P3) suggests a vagal hyperactivity during this phase which is blunted at resumption when HR is unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular reactivity to a new mental stress test: the maze test

The response to the maze test was studied in 31 subjects on no medication, including seven subjects with mild essential hypertension. Beat-by-beat finger blood pressure (BP) was measured with a Finapres device. Pulse interval from which heart rate (HR) was derived was obtained from the BP signal. A period of 5 min baseline was used to define resting levels of systolic BP and HR using 20-s averaged values for the calculation of the 95% confidence limit of the two variables. The average test duration was 10 min. During this period a series of video-displayed mazes had to be solved with easy mazes preceding difficult ones. No subject had been exposed to the test before. The maximal BP elevation associated with the test was 27 mmHg. The HR response averaged 11 beats/min. Significant elevations were observed for half the test duration. No significant relationship between these two responses was observed and some subjects exhibited isolated systolic BP or HR responses. When indices obtained during this active mental stress were compared to resting values, positive correlations were observed. When the resting standard deviation (SD) of systolic BP was higher the systolic response was greater. A similar relationship was observed for HR. In addition, when the systolic BP level at rest was higher, the systolic BP reactivity index was greater. However, systolic BP or HR at baseline were not predictive of the systolic BP or HR responses. This study demonstrates the applicability of a new test to assess cardiovascular reactivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Spectral analysis of systolic blood pressure and heart rate oscillations related to respiration

1. Non-invasive assessment of short-term systolic blood pressure (SBP) and heart rate (HR) variability was obtained with the plethysmographic finger blood pressure measurement device. Respiration was measured with a respiratory inductive plethysmograph, which was calibrated prior to each study. 2. The effects of breathing pattern on the respiratory (high frequency, HF) component of the SBP or HR spectrum were analysed by Fourier transform. 3. Our quantification of the changes in the HF (respiratory) peak of the HR or SBP spectrum with changes in tidal volume (VT) and breathing frequency (BF) indicates that the modulus of this component may be predicted for any combination of depth and frequency of breathing. 4. The modulus of this HF component for the HR or SBP spectrum was linearly related to the respiratory sinus arrhythmia (RSA) or to the SBP oscillation related to respiration.

Spectral analysis of systolic blood pressure and heart rate after heart transplantation in children

1. The aim of the study was to examine the short-term variability in blood pressure and heart rate in 19 children who had received heart transplants and in eight normal control children. 2. Blood pressure was determined by a finger arterial pressure device. We examined the power spectra for heart rate and systolic blood pressure in the supine and tilted positions. In addition, we studied the acute changes in blood pressure and heart rate during active standing. 3. In the transplanted children we could distinguish two groups (groups A and B) in whom heart rate variability differed, although in both it was greatly reduced compared with controls (group C). In group A there were no significant fluctuations in the mid-frequency range for heart rate. The gain of the relationship between systolic blood pressure and heart rate was very low and there were virtually no heart rate changes associated with passive tilting. 4. By contrast, in group B transplant patients the heart rate variability, as assessed by standard deviation, was about half that of normal controls. The power spectra attenuation was greater in the high-frequency than in the mid-frequency bands. On passive tilting the latter became enhanced, but not the high-frequency variability. On active standing the tachycardic response was about half that of controls. The findings suggest some reinnervation involving cardiac sympathetic fibres to a greater degree than the fast-responding vagal fibres. 5. In both groups A and B the drop in systolic blood pressure observed early in active standing was about 4-6 times as great as in controls.(ABSTRACT TRUNCATED AT 250 WORDS)

[Reproducibility of short-term variability indicators of blood pressure]

The aim of this study was to estimate the degree of reproducibility of blood pressure (BP) variability profile between 2 clinic visits. We recruited 15 untreated subjects (6 hypertensives, 9 normotensives) from the outpatient clinic. This group had undergone at least one BP measurement by the same investigator (A.G.). The subjects underwent 5-min BP monitoring (Finapres) during standing and after a rest in a supine position, at 10 AM and at 23 degrees C in a quiet room. Measurements were repeated after 7 days. A fast Fourier transform algorithm was used for analysis. There was no order effect with no difference between visits 1 and 2. Coefficients of variation (CV) for systolic BP, diastolic BP and heart rate were 9, 6 and 12%. High CVs of 20% were observed for the overall variability (total power) and the low frequency (LF, Mayer wave) component of BP. However the normalized LF (LF/total area) exhibited a acceptable CV of 15%. In conclusion the BP variability profile differences observed between visits might reflect intrasubject effect. This should be considered for assessing BP variability profile and for drug trial design.