Clinical Autonomic Research

Sandroni, Paola; Novak, Vera; Opfer-Gehrking, Tonette; Huck, Christine; Low, Phillip

doi: 10.1007/BF02291382pmid: 10750636

The postural tachycardia syndrome (POTS) is characterized clinically by orthostatic lightheadedness and tachycardia. When these patients perform a Valsalva maneuver, there is an excessive blood pressure increment after cessation of the maneuver (phase IV) that is sometimes associated with headaches. It is not known whether excessive phase IV is due to excessive peripheral vascular tone (an α-adrenergic mechanism) or is a manifestation of increased β-adrenergic tone (hyperadrenergic state). The authors undertook a pharmacologic study evaluating the effect of intravenous phentolamine (α-adrenergic antagonist) and propranolol (β-adrenergic antagonist) on the different phases of the Valsalva maneuver in a group of patients with POTS and age-matched normal control subjects. Patients with POTS had mean phases, when compared with controls, that were characterized by more negative II-E (p=0.07), smaller II-L (p=0.04), and significantly larger phase IV (p=0.001). The effect of phentolamine was qualitatively and quantitatively different in POTS when compared with controls. Ten mg phentolamine in controls resulted in a significant accentuation of phase II-E (p=0.001), attenuation of phase II-L (p=0.002), and increase of phase IV (57.6 vs 30.7 mm Hg; p=0.025). These changes resembled those of patients with POTS at baseline. In patients with POTS, the phase II abnormalities, already present, were further accentuated (p<0.001), and phase IV became smaller (50.6 vs 73.8 mm Hg; p=0.09). Propranolol had no significant effect on phases II-E and II-L, but significantly reduced phase IV in both controls (p<0.05) and in patients with POTS (p<0.001) and improved the headache symptoms, when present, during and after phase IV. The authors conclude that phase IV is mainly under β-adrenergic regulation and that the exaggerated phase IV in POTS is a result of a hyperadrenergic state.

Stewart, Julian

doi: 10.1007/BF02291383pmid: 10750637

Invasive arterial monitoring alters autonomic tone. The effects of intravenous (IV) insertion are less clear. The author assessed the effects of IV insertion on autonomic activity in patients aged 11 to 19 years prior to head-up tilt by measuring heart rate, blood pressure, heart rate variability, blood pressure variability, and baroreceptor gain before and after IV insertion with continuous electrocardiography and arterial tonometry in patients with orthostatic tachycardia syndrome (OTS, N=21), in patients who experienced simple fainting (N=14), and in normal control subjects (N=6). Five-minute samples were collected after 30 minutes supine. Fifteen minutes after IV insertion, data were collected again. These 5-minute samples were also collected in a separate control population without IV insertion after 30 minutes supine and again 30 minutes later. This population included 12 patients with OTS, 13 patients who experienced simple fainting, and 6 normal control subjects. Heart rate variability included the mean RR, the standard deviation of the RR interval (SDNN), and the root mean square of successive RR differences (RMSSD). Autoregressive spectral modeling was used. Low-frequency power (LFP, 0.04–0.15 Hz), high-frequency power (HFP, 0.15–0.40 Hz), and total power (TP, 0.01–0.40 Hz) were compared. Blood pressure variability included standard deviation of systolic blood pressure, LFP, and HFP. Baroreceptor gain at low frequency and high frequency was calculated from cross-spectral transfer function magnitudes when coherence was greater than 0.5. In patients with OTS, RR (790±50 msec), SDNN (54±6 msec), RMSSD (55±5 msec), LFP (422±200 ms2/Hz), HFP (846±400 ms2/Hz), and TP (1550±320 ms2/Hz) were less than in patients who experiences simple fainting (RR, 940±50 msec; SDNN, 84±10 msec; RMSSD, 91±7 msec; LFP, 880±342 ms2/Hz; HFP, 1720±210 ms2/Hz; and TP, 3228±490 ms2/Hz) or normal control subjects (RR, 920±30 msec; SDNN, 110±29 msec; RMSSD, 120±16 msec; LFP, 1600±331 ms2/Hz; HFP, 2700±526 ms2/Hz; and TP, 5400±1017 ms2/Hz). Blood pressure and blood pressure variability were not different in any group. Standard deviation, LFP, and HFP were, respectively, 5.24±0.8 mm Hg, 1.2±0.2, and 1.5±0.3 for patients with OTS; 4.6±0.4 mm Hg, 1.2±0.2, and 1.4±0.3 for patients who experienced simple fainting; and 5.55±1.0 mm Hg, 1.4±0.2, and 1.6±0.3 for normal control subjects. Baroreceptor gain at low frequency and high frequency in patients with OTS (16±4 msec/mm Hg 17±5) was comparable to that in patients who experienced simple fainting (33±4, 32±3) and that in normal control subjects (31±8, 37±9). Heart rate variability differed between patients with OTS and patients who experienced simple fainting or normal control subjects, and blood pressure and blood pressure variability were not different, but no parameter changed after IV insertion. There were no differences from the groups that did not receive IV insertions. Data suggest, at most, a limited effect of IV insertion on autonomic function in adolescents.

Turpeinen, Anu; Kuikka, Jyrki; Vanninen, Esko; Yang, Jiwei; Uusitupa, Matti

doi: 10.1007/BF02291384pmid: 10750638

Carnitine derivatives may have beneficial effects on cardiac and nerve function in patients with diabetes. The aim of this study was to investigate the effect of acetyl-L-carnitine (ALC) on myocardial sympathetic nervous function as measured with123I-meta-iodobenzyl guanidine (MIBG) and single-photon emission tomography (SPET) in 19 patients with diabetes (placebo group,n=6; ALC group,n=13) at the beginning and at the end of a 1-year randomized, placebo-controlled, doubleblind trial. The coefficient of variation for the MIBG analysis was 4%. In patients who were given a placebo, global myocardial MIBG uptake deteriorated during the study (MIBG uptake 1-year follow-up/baseline, 0.86±0.05, mean±standard error of mean), whereas in patients treated with ALC, MIBG uptake did not change significantly (1-year follow-up/baseline, 1.07±0.08; p=0.03 between the groups). On the basis of these preliminary data, we conclude that long-term treatment with ALC may be of potential value in preventing the progressive loss of myocardial sympathetic nervous function in patients with diabetes. MIBG-SPET is a sensitive and thus valuable method in assessing the development of myocardial sympathetic nervous dysfunction.

Glück, Thomas; Degenhardt, Eva; Schölmerich, Jürgen; Lang, Bernhard; Grossmann, Johannes; Straub, Rainer

doi: 10.1007/BF02291385pmid: 10750639

The purpose of this article is to examine the prevalence, degree, and natural course of pupillary neuropathy (PANP), cardiovascular autonomic neuropathy (CANP), and sensorimotor neuropathy (SNP) and to study the impact of disease stage and medication on neuropathy in 61 consecutive patients with HIV. PANP, CANP, and SNP were assessed by standardized test procedures. Overall prevalence of PANP, CANP, and SNP were 66%, 15%, and 15%, respectively. The maximal pupillary area (pupillary measure, p<0.0001) and the lying-to-standing ratio (cardiovascular measure, p<0.0001) were abnormal as compared with control subjects. The changes in CD4+ T-lymphocytes and respiratory sinus arrhythmia percentile during 2 years of follow-up correlated significantly (r=0.758, p=0.007). Patients with CANP were more often in an advanced disease stage than patients without CANP (p=0.004). SNP, but not PANP or CANP, was associated with the intake of the neuropathogenic drugs dideoxycytidine, dideoxyinosine, and 2′,3′ didehydro-2′,3′ dideoxythymidine (p<0.05). Autonomic and sensorimotor neuropathy are frequent in patients with HIV, and progression of CANP may put patients at risk for unexpected cardiorespiratory arrest.

Aoki, Mitsuhiro; Thilo, Kai; Burchill, Peter; Golding, John; Gresty, Michael

doi: 10.1007/BF02291386pmid: 10750640

This study explored the cardiovascular responses to illusions of self-motion (vection) induced in normal subjects according to the hypothesis that vection may be a model for vertigo in vestibular disease. Responses were obtained from 10 men who were exposed to rapid tilts of 20° and 30° rolling from the upright position down to the right or left shoulder. These responses were compared with those evoked during the illusion of roll-tilt vection provoked by a torsionally rotating visual field. Comparisons were made between 10-second data epochs before and after stimulus onset. In response to vection, blood pressure (BP) in the radial artery rose consistently in six subjects, and in all of these, a pressor response to real tilt was also observed. The remaining four subjects consistently had decreased BP in response to vection, and their BPs were affected little by tilt. Subjects whose BP increased with vection and tilt may have been dominated by tendency to arousal, whereas those whose BP decreased may reveal the more appropriate response to tilt from the upright position, which is a decrease in BP. This may reflect individual stereotypes and differences in the relative contributions of somatosensory and vestibular control of autonomic regulation.

Gordon, Victor; Opfer-Gehrking, Tonette; Novak, Vera; Low, Phillip

doi: 10.1007/BF02291387pmid: 10750641

A variety of approaches have been used to alleviate symptoms in postural tachycardia syndrome (POTS). Drugs reported to be of benefit include midodrine, propranolol, clonidine, and phenobarbital. Other measures used include volume expansion and physical countermaneuvers. These treatments may influence pathophysiologic mechanisms of POTS such as α-receptor dysfunction, β-receptor supersensitivity, venous pooling, and brainstem center dysfunction. The authors prospectively studied hemodynamic indices and symptom scores in patients with POTS who were acutely treated with a variety of interventions. Twenty-one subjects who met the criteria for POTS were studied (20 women, 1 man; mean age, 28.7±6.8 y; age range, 14–39 y). Patients were studied with a 5-minute headup tilt protocol, ECG monitoring, and noninvasive beat-to-beat blood pressure monitoring, all before and after the administration of an intervention (intravenous saline, midodrine, propranolol, clonidine, or phenobarbital). The hemodynamic indices studied were heart rate (ECG) and systolic, mean, and diastolic blood pressure. Patients used a balanced verbal scale to record any change in their symptoms between the tilts. Symptom scores improved significantly after the patients received midodrine and saline. Midodrine and propranolol reduced the resting heart rate response to tilt (p<0.005) and the immediate and 5-minute heart rate responses to tilt (p<0.002). Clonidine accentuated the immediate decrease in blood pressure on tilt up (p<0.05). It was concluded that midodrine and intravenous saline are effective in decreasing symptoms on tilt in patients with POTS when given acutely. Effects of treatments on heart rate and blood pressure responses generally reflected the known pharmacologic mechanisms of the agents.

Lieshout, Johannes; Harkel, A.; Wieling, Wouter

doi: 10.1007/BF02291388pmid: 10750642

Treatment with head-up tilt sleeping and low-dose fludrocortisone effectively minimizes orthostatic symptoms and increases orthostatic blood pressure in patients with neurogenic orthostatic hypotension. The aim of the present study was to examine whether the improvement in orthostatic blood pressure during combined treatment with low-dose fludrocortisone and nocturnal head-up tilt in patients with neurogenic orthostatic hypotension can be attributed to expansion of plasma volume or to increased total peripheral resistance.

Mathias, Christopher; Deguchi, Kazushi; Bleasdale-Barr, Katharine; Smith, Shelagh

doi: 10.1007/BF02291389pmid: 10750643

This report describes an 11-year-old girl with recurrent syncope beginning at the age of 2 1/2 years. Her paternal grandmother, father, and three of her five natural siblings had similar symptoms, often linked to emotional upsets. There were three adopted children from a single family, and none of these had syncope. Prior to referral there was an increase in attacks, some with convulsions, but with no other features of epilepsy. Vasovagal syncope was confirmed. However, continuous electroencephalogram, blood pressure, and heart rate recordings during attacks indicated that in some episodes there was neither cardiovascular change nor epileptiform activity, implying feigned syncope (pseudosyncope) with pseudoseizures. A psychological origin was sought, found, and in part rectified. The separation of vasovagal syncope from pseudosyncope, in the context of the family history, is discussed.

Schatz, Irwin

doi: 10.1007/BF02291390pmid: N/A

doi: 10.1007/BF02291391pmid: N/A