Mechanisms of blood pressure alterations in response to the Valsalva maneuver in postural tachycardia syndrome

Functional and 123I-MIBG scintigraphy assessment of cardiac adrenergic dysfunction in diabetes

OBJECTIVES

To assess the agreement between clinical cardiovascular adrenergic function and cardiac adrenergic innervation in type 2 diabetes patients (T2D).

METHODS

Thirty-three patients with T2D were investigated bimodally through (1) a standardized clinical cardiovascular adrenergic assessment, evaluating adequacy of blood pressure responses to the Valsalva maneuver and (2) 123I-meta-iodobenzylguanidine (MIBG) scintigraphy assessing myocardial adrenergic innervation measured as early and delayed heart heart/mediastinum (H/M) ratio, and washout rate (WR).

RESULTS

T2D patients had significantly lower early and delayed H/M-ratios, and lower WR, compared to laboratory specific reference values. Thirteen patients had an abnormal adrenergic composite autonomic severity score (CASS > 0). Patients with abnormal CASS scores had significantly higher early H/M ratios (1.76 [1.66-1.88] vs. 1.57 [1.49-1.63], p < 0.001), higher delayed H/M ratios (1.64 [1.51:1.73] vs. 1.51 [1.40:1.61] (p = 0.02)), and lower WR (-0.13(0.10) vs -0.05(0.07), p = 0.01). Lower Total Recovery and shorter Pressure Recovery Time responses from the Valsalva maneuver was significantly correlated to lower H/M early (r = 0.55, p = 0.001 and r = 0.5, p = 0.003, respectively) and lower WR for Total Recovery (r = -0.44, p = 0.01).

CONCLUSION

The present study found impairment of sympathetic innervation in T2D patients based on parameters derived from MIBG cardiac scintigraphy (low early H/M, delayed H/M, and WR). These results confirm prior studies. We found a mechanistically inverted relationship with favourable adrenergic cardiovascular responses being significantly associated unfavourable MIBG indices for H/M early and delayed. This paradoxical relationship needs to be further explored but could indicate adrenergic hypersensitivity in cardiac sympathetic denervated T2D patients.

Baroreflex sensitivity is associated with markers of hippocampal gliosis and dysmyelination in patients with psychosis

PURPOSE

Hippocampal dysfunction plays a key role in the pathology of psychosis. Given hippocampal sensitivity to changes in cerebral perfusion, decreased baroreflex function could contribute to psychosis pathogenesis. This study had two aims: (1) To compare baroreflex sensitivity in participants with psychosis to two control groups: participants with a nonpsychotic affective disorder and participants with no history of psychiatric disease; (2) to examine the relationship between hippocampal neurometabolites and baroreflex sensitivities in these three groups. We hypothesized that baroreflex sensitivity would be reduced and correlated with hippocampal neurometabolite levels in participants with psychosis, but not in the control groups.

METHODS

We assessed baroreflex sensitivity during the Valsalva maneuver separated into vagal and adrenergic components. Metabolite concentrations for cellular processes were quantitated in the entire multivoxel hippocampus using H¹-MR spectroscopic (MRS) imaging and were compared with baroreflex sensitivities in the three groups.

RESULTS

Vagal baroreflex sensitivity (BRS-V) was reduced in a significantly larger proportion of participants with psychosis compared with patients with nonpsychotic affective disorders, whereas participants with psychosis had increased adrenergic baroreflex sensitivity (BRS-A) compared with participants with no history of psychiatric disease. Only in psychotic cases were baroreflex sensitivities associated with hippocampal metabolite concentrations. Specifically, BRS-V was inversely correlated with myo-inositol, a marker of gliosis, and BRS-A was positively correlated with energy dependent dysmyelination (choline, creatine) and excitatory activity (GLX).

CONCLUSIONS

Abnormal baroreflex sensitivity is common in participants with psychosis and is associated with MRS markers of hippocampal pathology. Future longitudinal studies are needed to examine causality.

Skin Biopsy and Quantitative Sudomotor Axon Reflex Testing in Patients With Postural Orthostatic Tachycardia Syndrome

PURPOSE

No formal diagnostic criteria exist for the neuropathic subtype of postural orthostatic tachycardia syndrome (POTS). Skin biopsy and quantitative sudomotor axon reflex testing (QSORT) are preferred methods of assessment for autonomic small fiber neuropathy (SFN). This study characterizes the utility of these testing methods at a tertiary center and identifies clinical features associated with abnormal testing.

METHODS

Medical records of 2658 patients undergoing tilt table testing at a single institution between June 2018 and December 2020 were reviewed. Patients with postural orthostatic tachycardia syndrome were included for analysis of intraepidermal nerve fiber density (IENFD), sweat output, comorbidities, symptoms, measures of cardiovascular autonomic function, and serum antibody levels.

RESULTS

356 patients (90% female, mean age 31 ± 10) met the diagnostic criteria for postural orthostatic tachycardia syndrome. Of 211 patients who underwent quantitative sudomotor axon reflex testing, 70 (33%) demonstrated reduced sweat output. These patients were more likely to demonstrate sympathetic impairment during the Valsalva maneuver. Of 80 patients who underwent skin biopsies, 19 (24%) demonstrated reduced intraepidermal nerve fiber density. These patients tended to be older and have reduced heart rate variability during deep breathing. Neither test was associated with specific serum antibodies, symptoms, or comorbidities, though there was a trend toward higher rates of comorbid autoimmune disease in patients with abnormal testing.

CONCLUSION

A subset of patients with postural orthostatic tachycardia syndrome have evidence of small fiber neuropathy. These patients tend to have impaired cardiovascular autonomic function but are otherwise similar to patients with no evidence of small fiber neuropathy.

Preferential impairment of parasympathetic autonomic function in type 2 diabetes

OBJECTIVE

Cardiovascular autonomic neuropathy is a known complication in type 2 diabetes (T2D). However, the extent of sympathetic dysfunction and its relation to blood pressure (BP) dysregulation is insufficiently studied. We therefore assessed the cardiovascular sympathetic function using a standardized autonomic test-battery.

RESEARCH DESIGN AND METHODS

Forty T2D patients (mean age and duration of diabetes ±SD, 65.5 ± 7.3 and 9.5 ± 4.2 years) and 40 age- and gender-matched controls were examined through autonomic testing, assessing cardiovascular responses to deep breathing, Valsalva maneuver and tilt-table testing. Additionally, 24-hour oscillometric BP and self-reported autonomic symptoms on COMPASS-31 questionnaire was recorded.

RESULTS

Patients with T2D had reduced parasympathetic activity with reduced deep breathing inspiratory:expiratory-ratio (median [IQR] T2D 1.11 [1.08-1.18] vs. controls 1.18 [1.11-1.25] (p = 0.01)), and reduced heart rate variability (p < 0.05). We found no differences in cardiovascular sympathetic function measured through BP responses during the Valsalva maneuver (p > 0.05). 24-hour-BP detected reduced night-time systolic BP drop in T2D (9.8 % ± 8.8 vs. controls 15.8 % ± 7.7 (p < 0.01)) with more patients having reverse dipping. Patients with T2D reported more symptoms of orthostatic intolerance on the COMPASS-31 (p = 0.04).

CONCLUSIONS

Patients with T2D showed reduced parasympathetic activity but preserved short-term cardiovascular sympathetic function, compared to controls, indicating autonomic dysfunction with predominantly parasympathetic impairment. Despite this, T2D patients reported more symptoms of orthostatic intolerance in COMPASS-31 and had reduced nocturnal BP dipping, indicating that these are not a consequence of cardiovascular sympathetic dysfunction.

Cardiovascular Autonomic Regulation, ETCO2 and the Heart Rate Response to the Tilt Table Test in Patients with Orthostatic Intolerance

Chronic orthostatic intolerance (COI) is defined by changes in heart rate (HR), blood pressure (BP), respiration, symptoms of cerebral hypoperfusion and sympathetic overactivation. Postural tachycardia syndrome (POTS) is the most common form of COI in young adults and is defined by an orthostatic increase in heart rate (HR) of ≥ 30 bpm in the absence of orthostatic hypotension. However, some patients referred for evaluation of COI symptoms do not meet the orthostatic HR response criterion of POTS despite debilitating symptoms. Such patients are ill defined, posing diagnostic and therapeutic challenges. This study explored the relationship among cardiovascular autonomic control, the orthostatic HR response, EtCO₂ and the severity of orthostatic symptoms and fatigue in patients referred for evaluation of COI. Patients (N = 108) performed standardized testing protocol of the Autonomic Reflex Screen and completed the Composite Autonomic Symptom Score (COMPASS-31) and the Fatigue Severity Scale (FSS). Greater severity of COI was associated with younger age, larger phase IV amplitude in the Valsalva maneuver and lower adrenal baroreflex sensitivity. Greater fatigue severity was associated with a larger reduction in ETCO₂ during 10 min of head-up tilt (HUT) and reduced low-frequency (LF) power of heart rate variability. This study suggests that hemodynamic changes associated with the baroreflex response and changes in EtCO₂ show a stronger association with the severity of orthostatic symptoms and fatigue than the overall orthostatic HR response in patients with COI.

Autonomic Dysfunction in Autism Spectrum Disorder

Background: There have been previous reports of enhanced sympathoexcitation in autism spectrum disorder (ASD). However, there has been no formal investigation of autonomic dysfunction in ASD. Also, the joint hypermobile form of Ehlers-Danlos syndrome (hE-DS) that maybe overrepresented in ASD and orthostatic related autonomic dysfunction. This study examined the comorbidity of ASD, autonomic dysfunction and hE-DS in two UK autonomic national referral centers. Proven, documented and globally accepted clinical autonomic investigations were used to assess neuro-cardiovascular autonomic function in a cohort of ASD subjects and in age-matched healthy controls. Methods: Clinical data from 28 referrals with a confirmed diagnosis of ASD over a 10-year period were compared with 19 age-matched healthy controls. Autonomic function was determined using methods established in the centers previously described in detail. Results: 20/28 ASD had a diagnosed autonomic condition; 9 had the postural tachycardia syndrome (PoTS), 4 PoTS and vasovagal syncope (VVS), 3 experienced presyncope, 1 essential hyperhidrosis, 1 orthostatic hypotension, 1 VVS alone and 1 a combination of PoTS, VVS and essential hyperhidrosis. 16/20 ASD with autonomic dysfunction had hE-DS. In ASD, basal heart rate and responses to orthostatic tests of autonomic function were elevated, supporting previous findings of increased sympathoexcitation. However, sympathetic vasoconstriction was impaired in ASD. Conclusion: Intermittent neuro-cardiovascular autonomic dysfunction affecting heart rate and blood pressure was over-represented in ASD. There is a strong association with hE-DS. Autonomic dysfunction may further impair quality of life in ASD, particularly in those unable to adequately express their experience of autonomic symptoms.

Influence of repetitions on the Valsalva maneuver

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Changes in pressor and heart rate patterns occur when performing consecutive Valsalva maneuvers.

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Valsalva ratio may not be a reliable index to evaluate cardiovagal responses.

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Repeating the Valsalva maneuver more than 4 times is not recommended.

Objective

In autonomic units, patients perform several short Valsalva maneuvers (VMs) while learning the procedure. The effects of repeated VMs on cardiovascular elicited responses were assessed.

Methods

14 healthy volunteer subjects were selected (aged 22–26). VMs were performed every 3 min up to 6 times in a reclined sitting position. Changes in blood pressure (BP), heart rate (HR) and baroreflex sensitivity indexes were evaluated. Subjects were classified according to their adrenergic response patterns.

Results

VMs repetitions evoked a progressive decrease in BP during phases II and III and a reduced increase in mean BP at late phase II. Increased bradycardia at early phase II and IV was also observed. Last two VMs showed a significant increase in Valsalva ratio, while other indexes remained unaltered. Subjects with balanced adrenergic responses presented extended pressure recovery time from the third repetition and lower BP values than those with augmented or suppressed adrenergic responses.

Conclusions

Significant changes in BP and HR at certain phases were observed when consecutive VMs were performed in young subjects in a reclined position. The most affected baroreflex index was the Valsalva ratio. Adrenergic response patterns showed differences that should be considered in order to avoid false positives.

Significance

We recommend not repeating the VM more than 4 times and revisiting the role and reliability of the Valsalva ratio.

Vagal and Sympathetic Function in Neuropathic Postural Tachycardia Syndrome

The diagnosis of neuropathic postural tachycardia syndrome (POTS) requires research techniques not available clinically. We hypothesized that these patients will have impaired vagal and sympathetic cardiovascular control that can be characterized with clinical autonomic tests. We included 12 POTS patients with possible neuropathic subtype because of normal plasma norepinephrine and no increase in upright blood pressure. We compared them to 10 healthy subjects. We assessed hemodynamics, heart rate and blood pressure variability, baroreflex sensitivity, raw and integrated muscle sympathetic nerve activity, and blood volume. To understand the vagal/sympathetic control, we dissected the phase 2 of Valsalva maneuver (VM) into early (VM2e) and late (VM2l). POTS' upright heart rate increased 43±3 bpm. Patients had normal plasma volume but reduced red blood cell volume (1.29 L versus predicted normal values 1.58 L; P=0.02). Vagal indices of heart rate variability, HF_RRI (430±130 versus 1680±900; P=0.04), PNN50, and root mean squared of successive differences were lower in POTS. Patients showed a decrease in vagal baroreflex sensitivity (VM2e; P=0.04). In POTS, integrated muscle sympathetic nerve activity was lower at rest (12±1.5 versus 20±2 burst/min; P=0.004) and raw muscle sympathetic nerve activity spike analysis showed blunted responses during VM2e, despite a greater drop in systolic blood pressure (34±5 in POTS and 14±6 mm Hg in controls; P=0.01). This cohort of POTS patients enriched for possible neuropathic subtype had lower resting muscle sympathetic nerve activity, impaired vagal cardiac control, and exaggerated drop in blood pressure in response to VM and a delay in the sympathetic cardiovascular responsiveness during hypotensive challenge.

The Valsalva manoeuvre: physiology and clinical examples

The Valsalva manoeuvre (VM), a forced expiratory effort against a closed airway, has a wide range of applications in several medical disciplines, including diagnosing heart problems or autonomic nervous system deficiencies. The changes of the intrathoracic and intra-abdominal pressure associated with the manoeuvre result in a complex cardiovascular response with a concomitant action of several regulatory mechanisms. As the main aim of the reflex mechanisms is to control the arterial blood pressure (BP), their action is based primarily on signals from baroreceptors, although they also reflect the activity of pulmonary stretch receptors and, to a lower degree, chemoreceptors, with different mechanisms acting either in synergism or in antagonism depending on the phase of the manoeuvre. A variety of abnormal responses to the VM can be seen in patients with different conditions. Based on the arterial BP and heart rate changes during and after the manoeuvre several dysfunctions can be hence diagnosed or confirmed. The nature of the cardiovascular response to the manoeuvre depends, however, not only on the shape of the cardiovascular system and the autonomic function of the given patient, but also on a number of technical factors related to the execution of the manoeuvre including the duration and level of strain, the body position or breathing pattern. This review of the literature provides a comprehensive analysis of the physiology and pathophysiology of the VM and an overview of its applications. A number of clinical examples of normal and abnormal haemodynamic response to the manoeuvre have been also provided.

The utility of Valsalva maneuver in the diagnoses of orthostatic disorders

The objective of this study was to assess hemodynamic responses and baroreflex sensitivity (BRS) indexes during Valsalva maneuver (VM) and head-up tilt (HUT) testing in orthostatic intolerance (OI). Patients with neurogenic orthostatic hypotension (NOH, n = 26), postural tachycardia syndrome (n = 26) and symptomatic OI (n = 14) were compared with healthy population (control, n = 107) and inappropriate sinus tachycardia (n = 7). Hemodynamic assessment included patterning and quantification with vagal and adrenergic BRS (BRSa/BRSa1). In NOH, cardiovagal systolic blood pressure (SBP) decrements in VM and HUT were correlated (r = 0.660, P < 0.001); a "V" pattern of VM indicated α-BRSa failure. Yet BRSa1 did not reveal changes vs. control (P > 0.05) or was not applicable in 60% of NOH. In symptomatic OI, compared with control, cardiovagal SBP decrements were larger (P < 0.05); higher BRSa1 contradicted higher adrenergic index (Composite Autonomic Severity Score). Overshoot in phase IV dipped below baseline or dropped ≥ 10 mmHg over 8 s in postural tachycardia syndrome ("N" pattern), but by 3 s in inappropriate sinus tachycardia ("M" pattern). Visualization of distinct VM patterns allows primary evaluation of autonomic dysfunction and differentiation of the various forms of OI. BRSa1 evaluation is compromised by pathological SBP patterns. VM patterning is a valuable nonpostural supplement to HUT capable of detecting and differentiating OI.

Characterisation of sleep disturbances in postural orthostatic tachycardia syndrome: a polysomnography-based study

BACKGROUND AND AIM

Postural orthostatic tachycardia syndrome (PoTS) has been frequently associated with sleep disturbances but objective sleep data are lacking. In addition, although regional autonomic denervation has been described, less is known about autonomic nervous activity overnight in these patients.

PATIENTS/METHODS

A full polysomnography and heart rate variability were performed on 37 patients diagnosed with PoTS . In addition, a multiple sleep latency test (MSLT) was conducted on a subgroup of patients with excessive daytime sleepiness.

RESULTS

The polysomnographic data did not show major pathological findings except the percentage spent in rapid eye movement (REM) sleep which was slightly reduced at 18.4%. The MSLT did not confirm excessive daytime sleepiness as median mean sleep latency was 14.4 min (11.8-17.5). When comparing patients with and without subjective daytime sleepiness, it was found that the latter had a reduced parasympathetic activation at night as expressed by the average high frequency [6936.5 ms(2) (6028.2-8675.5) vs. 4689.5 (3922.7-7685.2) p < 0.05].

CONCLUSION

Patients with PoTS do not exhibit polysomnographic findings consistent with relevant sleep pathologies nor objective daytime sleepiness. Subjective daytime sleepiness is associated with enhanced activation of the parasympathetic nervous system.

Sleep disturbances and autonomic dysfunction in patients with postural orthostatic tachycardia syndrome

Many patients with postural tachycardia syndrome (PoTS) suffer from fatigue, daytime sleepiness, and sleeping disturbances. The objective of this study was to compare subjective and objective sleep quality of PoTS patients with a group of healthy controls. All patients completed a Pittsburgh Sleep Quality Index questionnaire and the Epworth Sleepiness Scale. The patients sleep architecture, heart rate, and heart rate variability (HRV) measurements were taken during one night at the sleep laboratorium. All data was collected at the Sleep Unit, at Helios Klinikum Wuppertal. Thirty-eight patients diagnosed with PoTS were compared to 31 healthy controls, matched in age and gender. Patients with PoTS reached significantly higher scores in sleep questionnaires, which means that they were more sleepy and had a lower sleep quality. Polysomnography showed a significantly higher proportion of stage 2 sleep. The results of HRV analysis in different sleep stages confirmed changes in autonomic activity in both groups. PoTS patients, however, showed a diminished variability of the low-frequency (LF) band, high-frequency (HF) band, and LF/HF ratio in different sleep stages. It can therefore be gathered that PoTS could be considered as potential differential diagnosis for sleep disturbances since PoTS patients had a subjective diminished sleep quality, reached higher levels of daytime sleepiness, and showed a higher proportion of stage 2 sleep. PoTS patients showed furthermore a reduction of LF/HF ratio variability in different sleep stages.

Structural and functional small fiber abnormalities in the neuropathic postural tachycardia syndrome

OBJECTIVE

To define the neuropathology, clinical phenotype, autonomic physiology and differentiating features in individuals with neuropathic and non-neuropathic postural tachycardia syndrome (POTS).

METHODS

Twenty-four subjects with POTS and 10 healthy control subjects had skin biopsy analysis of intra-epidermal nerve fiber density (IENFD), quantitative sensory testing (QST) and autonomic testing. Subjects completed quality of life, fatigue and disability questionnaires. Subjects were divided into neuropathic and non-neuropathic POTS, defined by abnormal IENFD and abnormal small fiber and sudomotor function.

RESULTS

Nine of 24 subjects had neuropathic POTS and had significantly lower resting and tilted heart rates; reduced parasympathetic function; and lower phase 4 valsalva maneuver overshoot compared with those with non-neuropathic POTS (P<0.05). Neuropathic POTS subjects also had less anxiety and depression and greater overall self-perceived health-related quality of life scores than non-neuropathic POTS subjects. A sub-group of POTS patients (cholinergic POTS) had abnormal proximal sudomotor function and symptoms that suggest gastrointestinal and genitourinary parasympathetic nervous system dysfunction.

CONCLUSIONS AND RELEVANCE

POTS subtypes may be distinguished using small fiber and autonomic structural and functional criteria. Patients with non-neuropathic POTS have greater anxiety, greater depression and lower health-related quality of life scores compared to those with neuropathic POTS. These findings suggest different pathophysiological processes underlie the postural tachycardia in neuropathic and non-neuropathic POTS patients. The findings have implications for the therapeutic interventions to treat this disorder.

The Valsalva maneuver: screening for drug-induced baroreflex dysfunction

OBJECTIVE

Many drugs can interfere with baroreflex mechanisms thereby impairing blood pressure control, but few have undergone sufficient testing. The state of affairs may be explained by the lack of simple and inexpensive screening tests.

METHODS

In eleven healthy men, we tested the hypothesis that a simple Valsalva maneuver could detect drug-induced changes in baroreflex function that have previously been described using more elaborate and invasive methodologies. They performed Valsalva maneuvers after selective pharmacological inhibition of the norepinephrine transporter (NET) in a placebo-controlled, double-blind, randomized, crossover fashion. Patients with severe autonomic failure served as positive controls.

RESULTS

NET inhibition profoundly augmented the blood pressure decrease during phase II and attenuated the blood pressure overshoot in phase IV compared with placebo. Furthermore, NET inhibition increased the heart rate response during the Valsalva maneuver.

INTERPRETATION

The Valsalva maneuver recapitulated complex alterations in baroreflex regulation during NET inhibition. Thus, this simple and inexpensive test could be employed as a screening tool for drug-induced baroreflex dysfunction.

Tuba players reproduce a Valsalva maneuver while playing high notes

Playing wind instruments requires expiratory efforts. Blowing low notes on a tuba means a low resistance to expiration while playing high notes requires a strenuous expiratory strain. The resulting high intrathoracic pressure may reproduce a Valsalva maneuver. Ten tuba players were asked to blow medium loud long (15 seconds) notes at three different pitches (low, middle, and high) and to perform Valsalva maneuvers at 10, 40, and 60 mmHg. Blood pressure (BP) was measured continuously with a Finapres monitor. The four classic phases of the Valsalva maneuver were reproduced with the notes. The expiratory effort produced systolic BP and pulse pressure falls reaching about 24 mmHg with the high note or the Valsalva 60. BP and pulse pressure falls were linearly related to stroke volume reductions. Reflex heart rate (HR) changes were inversely related to BP falls, with maximal increases for the high notes (24 beats/minute) and Valsalva 60 (33 beats/minute). High baroreflex sensitivity was associated with a high HR response. Total peripheral resistance was reflexly elevated to counteract cardiac output reductions. During rebreathing, BP overshoots reached 30 mmHg for the high note and 53 mmHg for the Valsalva 60. Altogether, these findings indicate that blowing notes on a tuba reproduces the cardiovascular changes seen with a Valsalva maneuver with the effects of blowing high notes being close to a classic (40 mmHg) Valsalva maneuver. In addition, the baroreflex sensitivity might be a predictor of the ability to surmount the BP intolerance that could occur during wind instrument playing.

HAEMODYNAMIC CONTRIBUTIONS TO THE PATHOGENESIS OF PREECLAMPSIA AND ECLAMPSIA

Current hypotheses regarding the origins of preeclampsia have focused on the “Two stage model”. This model suggests that the primary steps in the pathophysiologic sequence of preeclampsia are initiated by abnormal placentation including the classic finding of abnormal trophoblast invasion of maternal decidual spiral arteries. The second stage of the sequence includes the elaboration of a single or multiple substances from these disordered placentas which contribute to the generalized maternal systemic illness, eventually manifesting as endothelial injury, hypertension and proteinuria. Recent studies have focused on the role of pro and anti-angiogenic peptides as potential placentally derived aetiologic agents in this pathophysiologic sequence, although other placental products have been highlighted in recent research. Despite the fact that this modeling of preeclampsia has widespread support significant limitations to this hypothesis can be identified.

Cardiac denervation in postural tachycardia syndrome

Myocardial 123I-Meta-iodobenzylguanidine uptake was markedly reduced in a patient with postural tachycardia syndrome (POTS). This finding suggests that loss of sympathetic autonomic neurons in the heart may play a role in the etiology of POTS.

Hipertensión arterial episódica asociada al síndrome de taquicardia postural ortostática

We report the case of a 17-year-old woman who presented to the emergency department on several occasions due to palpitations, tachycardia, syncope, short spells of dizziness and light-headedness with complete spontaneous recovery, and hypertension. The patient had been evaluated by several specialists, and multiple complementary examinations had revealed no abnormalities that could explain the symptoms. Due to suspicion of orthostatic intolerance or postural orthostatic tachycardia syndrome with hypertension, the patient underwent a 60-degree tilt table test, which confirmed the diagnosis. The patient was successfully treated with bisoprolol. The physiopathological mechanisms, diagnosis, and treatment of this syndrome are reviewed.

Cerebral Syncope: Insights from Valsalva Maneuver

BACKGROUND AND PURPOSE

Cerebral syncope refers to a loss of consciousness associated with cerebral vasoconstriction in the absence of systemic hypotension. The diagnosis of cerebral syncope could be established by the head-up tilt test (HUT) and transcranial Doppler ultrasonography. Valsalva maneuver (VM) permitted assessment of cerebral autoregulatory function by provoking blood pressure (BP) changes. To develop a path-physiological approach for vasomotor reactivity of cerebral syncope, the authors combined these maneuvers (HUT/transcranial Doppler/VM).

METHODS

Using transcranial Doppler ultrasonography, we simultaneously recorded systemic arterial BP in the radial artery and flow velocities in both middle cerebral arteries (MCAFV) in 10 cerebral syncope patients (4 males and 6 females, 35.24 +/- 4.5 years old) during the Valsalva maneuver.

RESULTS

The characteristic changes in BP (phases I-IV) were seen in all subjects, accompanying distinct changes in cerebral blood flow velocity. The BP/heart rate responding to VM was within normal limit in all subjects. There was no orthostatic hypotension. Instead, BP increased during the tilting test in 2 subjects (20.00%). The MCAFV dropped 25.4 +/- 2.3% from baseline. Abnormal flattening of MCAFV during late phase II (IIb), the paradoxical drop of flow velocity despite restoration of BP, was noted in 9 subjects (90.00%).

CONCLUSION

During VM there are complex changes in relevant cardiovascular and cerebrovascular variables within a short time span. The paradoxical drop of MCAFV during phase IIb was the result of complex parameters. Among them, a failure in cerebrovascular resistance reduction and even paradoxical vasoconstriction might further compromise cerebral perfusion pressure and lead to syncope.

The Valsalva manoeuvre--cardiovascular effects and performance technique: a critical review

Variations in the technique of the Valsalva manoeuvre (VM) have been shown to greatly influence the pattern of cardiovascular response (CVR) to the test. Intra-strain tachycardia, post-strain bradycardia, Valsalva ratio, and baroreflex sensitivity decrease in proportion to an increase in lung volume and a decrease in strain pressure at VM. In conditions of completely expanded lungs and low strain pressure many subjects reveal an intra-strain bradycardic response to VM instead of the usual tachycardic one. Intra-strain arterial hypotension and post-strain hypertension decrease with decrease in strain pressure. The changes in heart rate and blood pressure during an expiratory VM are greater than the responses observed during completition of an inspiratory VM. The rate of the deep inspiration prior to strain has an impact particularly on phase I of the VM. The magnitude of the CVR correlates with the strain duration, particularly at high levels of strain pressure, and depends on the baseline level of the cardiovascular parameters and their variations. The paper discusses the possible mechanisms of different CVRs to variations in the technique of the VM. Some practical recommendations are suggested.

Splanchnic hyperemia and hypervolemia during Valsalva maneuver in postural tachycardia syndrome

Prior work demonstrated dependence of the change in blood pressure during the Valsalva maneuver (VM) on the extent of thoracic hypovolemia and splanchnic hypervolemia. Thoracic hypovolemia and splanchnic hypervolemia characterize certain patients with postural tachycardia syndrome (POTS) during orthostatic stress. These patients also experience abnormal phase II hypotension and phase IV hypertension during VM. We hypothesize that reduced splanchnic arterial resistance explains aberrant VM results in these patients. We studied 17 POTS patients aged 15-23 yr with normal resting peripheral blood flow by strain gauge plethysmography and 10 comparably aged healthy volunteers. All had normal blood volumes by dye dilution. We assessed changes in estimated thoracic, splanchnic, pelvic-thigh, and lower leg blood volume and blood flow by impedance plethysmography throughout VM performed in the supine position. Baseline splanchnic blood flow was increased and calculated arterial resistance was decreased in POTS compared with control subjects. Splanchnic resistance decreased and flow increased in POTS subjects, whereas splanchnic resistance increased and flow decreased in control subjects during stage II of VM. This was associated with increased splanchnic blood volume, decreased thoracic blood volume, increased heart rate, and decreased blood pressure in POTS. Pelvic and leg resistances were increased above control and remained so during stage IV of VM, accounting for the increased blood pressure overshoot in POTS. Thus splanchnic hyperemia and hypervolemia are related to excessive phase II blood pressure reduction in POTS despite intense peripheral vasoconstriction. Factors other than autonomic dysfunction may play a role in POTS.

Autonomic dysfunction in peripheral nerve disease

Autonomic neuropathies are inherited or acquired neuropathies in which autonomic nerve fibers are selectively or disproportionately affected. Generally, sympathetic and parasympathetic fibers are both affected but there are exceptions. Acquired cases can be autoimmune; due to diabetes, amyloidosis, drugs, or toxins; or idiopathic. Autoimmune autonomic neuropathy is often subacute, sometimes associated with a neoplasm, and associated with high titers of antibody to ganglionic nicotinic acetylcholine receptor in about half of the severe cases. The molecular basis of inherited autonomic neuropathies is better known, including recent identification of the loci and genes of hereditary sensory and autonomic neuropathies types I, III, and IV. The inherited amyloid neuropathies are due to mutations of three proteins: transthyretin, apolipoprotein A1, and gelsolin. Non-invasive autonomic testing complements clinical and electrophysiological characterization of the autonomic neuropathies.

Relationship of plasma volume to sympathetic tone in nulliparous women

OBJECTIVE

We sought to determine whether resting supine plasma volume is related to sympathetic tone in healthy young nulligravid normotensive women.

STUDY DESIGN

Forty women were examined in the midfollicular phase. Alpha-adrenergic tone was estimated by an examination of the late phase II blood pressure response to the Valsalva maneuver. Resting heart rate was examined to evaluate the balance of sympathetic and parasympathetic input. Plasma catecholamines were measured during supine rest. Plasma volume was estimated by Evans blue dilution.

RESULTS

Plasma volume corrected for body surface area was correlated inversely to late phase II blood pressure response to the Valsalva maneuver (r = -0.31, P <.05) and was correlated directly to the cardiac R-R interval (r = 0.41, P <.01). There was no relationship of plasma volume corrected for body surface area to mean arterial pressure (r = -0.13, P not significant). We found no significant relationship of plasma epinephrine concentration (r = -0.05, P =.76) or plasma norepinephrine (r = -0.09, P =.60) with plasma volume corrected for body surface area.

CONCLUSION

We conclude that plasma volume is related inversely to both an estimate of alpha-adrenergic activation and heart rate. These findings are consistent with an adaptive physiologic response that is aimed at the maintenance of blood pressure in the face of reduced plasma volume.

Brain responses associated with the Valsalva maneuver revealed by functional magnetic resonance imaging

The Valsalva maneuver, a test frequently used to evaluate autonomic function, recruits discrete neural sites. The time courses of neural recruitment relative to accompanying cardiovascular and breathing patterns are unknown. We examined functional magnetic resonance imaging signal changes within the brain to repeated Valsalva maneuvers and correlated these changes with physiological trends. In 12 healthy subjects (age, 30-58 yr), a series of 25 volumes (20 gradient echo echo-planar image slices per volume) was collected using a 1.5-Tesla scanner during a 60-s baseline and 90-s challenge period consisting of three Valsalva maneuvers. Regions of interest were examined for signal intensity changes over baseline and challenge conditions in cardiorespiratory-related regions. In addition, whole brain correlations between signal intensity and heart rate and airway load pressure were performed on a voxel-by-voxel basis. Significant signal changes, correlated with the time course of load pressure and heart rate, emerged within multiple areas, including the amygdala and hippocampus, insular and lateral frontal cortices, dorsal pons, dorsal medulla, lentiform nucleus, and fastigial and dentate nuclei of the cerebellum. Signal intensities peaked early in the Valsalva maneuver within the hippocampus and amygdala, later within the dorsal medulla, pons and midbrain, and deep cerebellar nuclei, and last within the lentiform nuclei and the lateral prefrontal cortex. The ventral pontine signals increased during the challenge, but not in a fashion correlated to load pressure or heart rate. Sites showing little or no correlation included the vermis and medial prefrontal cortex. These data suggest an initiating component arising in rostral brain areas, a later contribution from cerebellar nuclei, basal ganglia, and lateral prefrontal cortex, and a role for the ventral pons in mediating longer term processes.