Cerebral Blood Flow, Heart Rate, and Blood Pressure Patterns during the Tilt Test in Common Orthostatic Syndromes

Validation of the Chinese orthostatic discriminant and Severity Scale (ODSS) for detection of orthostatic intolerance syndrome

Background

Orthostatic intolerance (OI) is the inability to tolerate orthostatic stress during any postural change. The etiology of OI varies, and methods to obtain a specific diagnosis and plan appropriate treatment are important. The tools available within the Chinese context to swiftly identify orthostatic intolerance syndrome (OIS) are currently limited.

Methods

Patients with OI symptoms were included in this study and categorized into two groups based on the results of the supine-to-stand test. Those with abnormal test results were assigned to the OIS group, while those with normal test results were placed in the non-OIS group. We evaluated the internal consistency and predictive value of the Chinese Orthostatic Discriminant and Severity Scale (ODSS) by comparing patients' scores with their physiological measurements collected during orthostatic stress tests and the results of other available questionnaires, including the orthostatic Symptom Questionnaire and Orthostatic Grading Scale (OGS).

Results

Patients with OIS scored significantly higher on all three questionnaires and showed significant differences in autonomic responses during orthostatic stress tests compared with non-OIS patients. Receiver operating characteristic curve analysis showed that the orthostatic score from the ODSS had moderate predictive value for the supine test (area under the curve [AUC] = 0.754). Further subgroup analysis revealed that the orthostatic score from the ODSS had uniquely high specificity and sensitivity for identifying patients with orthostatic hypotension with abnormal cerebral blood flow (OH-U, AUC = 0.919).

Conclusions

We conclude that the Chinese version of the ODSS has sufficient reliability and validity to distinguish patients with OIS and could possibly be used as a diagnostic tool for OH-U patients. Thus, the Chinese ODSS offers a beneficial screening tool for quickly assessing whether patients have OIS that requires further clinical assessment.

Cerebral blood flow and end-tidal CO2 predict lightheadedness during head-up tilt in patients with orthostatic intolerance

Orthostatic intolerance (OI) is a common problem. Reliable markers of OI are missing, as orthostatic blood pressure and heart rate poorly correlate with orthostatic symptoms. The objective of this study was to assess the relationship between orthostatic lightheadedness and cerebral blood flow. In this retrospective study patients with OI were evaluated at the Autonomic Laboratory of the Department of Neurology, Brigham and Women's Faulkner Hospital, Boston. The 10-minute head-up tilt test was performed as a part of autonomic testing. Orthostatic lightheadedness was evaluated at every minute of the head-up tilt. Heart rate, blood pressure, capnography, and cerebral blood flow velocity (CBFv) in the middle cerebral artery using transcranial Doppler were measured. Repeated-measures design with a linear mixed-effects model was used to evaluate the relationship between orthostatic lightheadedness and hemodynamic variables. Correlation analyses were done by calculating Pearson's coefficient. Twenty-two patients with OI were compared to nineteen controls. Orthostatic CBFv and end-tidal CO2 decreased in OI patients compared to controls (p < 0.001) and predicted orthostatic lightheadedness. Orthostatic heart rate and blood pressure failed to predict orthostatic lightheadedness. The lightheadedness threshold, which marked the onset of lightheadedness, was equal to an average systolic CBFv decrease of 18.92% and end-tidal CO2 of 12.82%. The intensity of lightheadedness was proportional to the CBFv and end-tidal CO2 decline. Orthostatic lightheadedness correlated with systolic CBFv (r=-0.6, p < 0.001) and end-tidal CO2 (r=-0.33, p < 0.001) decline. In conclusion, orthostatic CBFv and end-tidal CO2 changes predict orthostatic lightheadedness and can be used as objective markers of OI.

Possible Role of Fibrinaloid Microclots in Postural Orthostatic Tachycardia Syndrome (POTS): Focus on Long COVID

Postural orthostatic tachycardia syndrome (POTS) is a common accompaniment of a variety of chronic, inflammatory diseases, including long COVID, as are small, insoluble, 'fibrinaloid' microclots. We here develop the argument, with accompanying evidence, that fibrinaloid microclots, through their ability to block the flow of blood through microcapillaries and thus cause tissue hypoxia, are not simply correlated with but in fact, by preceding it, may be a chief intermediary cause of POTS, in which tachycardia is simply the body's exaggerated 'physiological' response to hypoxia. Similar reasoning accounts for the symptoms bundled under the term 'fatigue'. Amyloids are known to be membrane disruptors, and when their targets are nerve membranes, this can explain neurotoxicity and hence the autonomic nervous system dysfunction that contributes to POTS. Taken together as a system view, we indicate that fibrinaloid microclots can serve to link POTS and fatigue in long COVID in a manner that is at once both mechanistic and explanatory. This has clear implications for the treatment of such diseases.

Effect of acute levodopa challenge test on cerebral blood flow in Parkinson's disease with the supine-to-standing transcranial Doppler test

BACKGROUND

Levodopa, a common drug that improves symptoms of Parkinson's disease (PD), can induce a reduction in blood pressure (BP); however, the effect of levodopa on cerebral blood flow (CBF) remains unclear.

OBJECTIVES

To observe the changes in BP and CBF during active standing before and after the acute levodopa challenge test (ALCT) and analyse the influencing factors of CBF in patients with PD.

METHODS

BP and CBF velocity were simultaneously recorded by continuous beat-to-beat non-invasive BP monitoring and transcranial Doppler at supine and orthostatic positions twice, before and after ALCT. The patients were divided into two groups according to those with increased and decreased CBF at baseline after ALCT to analyse the influencing factors.

RESULTS

We examined 64 patients with PD (59.2 ± 11.6 years, 33 males). BP decreased at all timepoints after ALCT, while there was no significant change in the magnitude of the drop in BP induced by standing. CBF was reduced after ALCT, especially within 15 s to 1 min of standing (15 s: 48.95 ± 13.50 vs. 44.93 ± 13.26, p < 0.001; 30 s: 52.46 ± 12.06 vs. 50.11 ± 12.56, p = 0.033; 1 min: 52.19 ± 11.83 vs. 50.17 ± 13.21, p = 0.044). Lower body mass index (β = -0.280, p = 0.027) was an independent factor associated with CBF reduction after ALCT.

CONCLUSIONS

Additional attention should be paid to changes in CBF and BP within 1 min after standing in patients with PD taking levodopa, especially in those with low bodyweight.

Resting heart rate (variability) and cognition relationships reveal cognitively healthy individuals with pathological amyloid/tau ratio

Introduction

Resting heart rate (HR) and heart rate variability (HRV) have been linked with cognition in the general population and in older individuals. The knowledge of this aspect of heart-brain relationship is relatively absent in older individuals with early Alzheimer's disease (AD) pathology. This study explores relationships of the HR, HRV, and cognition in cognitively healthy individuals with pathological amyloid/tau ratio (CH-PATs) in cerebral spinal fluid (CSF) compared to those with normal ratio (CH-NATs).

Methods

We examined therelationshipsbetween1) resting HR and Mini-Mental State Examination (MMSE); 2) resting HR and brain processing during Stroop interference; and 3) resting vagally mediated HRV (vmHRV) and task switching performance.

Results

Our studies showed that compared to CH-NATs, those CH-PATs with higher resting HR presented with lower MMSE, and less brain activation during interference processing. In addition, resting vmHRV was significantly correlated with task switching accuracy in CH-NATs, but not in CH-PATs.

Discussion

Thesethreedifferenttestsindicatedysfunctionalheart-brainconnections in CH-PATs, suggesting a potential cardio-cerebral dysfunctional integration.

Frontal lobe hemodynamics detected by functional near-infrared spectroscopy during head-up tilt table tests in patients with electrical burns

Significance

Electrical burns can cause severe damage to the nervous system, resulting in autonomic dysfunction with reduced cerebral perfusion. However, few studies have investigated these consequences.

Aim

To elucidate changes in prefrontal cerebral hemodynamics using functional near-infrared spectroscopy (fNIRS) during the head-up tilt table test (HUT) for patients with electrical burns.

Approach

We recruited 17 patients with acute electrical burns within 1 week after their accidents and 10 healthy volunteers. The NIRS parameters acquired using an fNIRS device attached to the forehead were analyzed in five distinct HUT phases.

Results

Based on their HUT response patterns, patients with electrical burns were classified into the group with abnormal HUT results (APG, n = 4) or normal HUT results (NPG, n = 13) and compared with the healthy control (HC, n = 10) participants. We found trends in hemodynamic changes during the HUT that distinguished HC, NPG, and APG. Reduced cerebral perfusion and decreased blood oxygenation during the HUT were found in both the NPG and APG groups. Patients with electrical burns had autonomic dysfunction compared to the HC participants.

Conclusions

Using fNIRS, we observed that acute-stage electrical burn injuries could affect cerebral perfusion.

Implementation of exercise countermeasures during spaceflight and microgravity analogue studies: Developing countermeasure protocols for bedrest in older adults (BROA)

Significant progress has been made in the development of countermeasures to attenuate the negative consequences of prolonged exposure to microgravity on astronauts’ bodies. Deconditioning of several organ systems during flight includes losses to cardiorespiratory fitness, muscle mass, bone density and strength. Similar deconditioning also occurs during prolonged bedrest; any protracted time immobile or inactive, especially for unwell older adults (e.g., confined to hospital beds), can lead to similar detrimental health consequences. Due to limitations in physiological research in space, the six-degree head-down tilt bedrest protocol was developed as ground-based analogue to spaceflight. A variety of exercise countermeasures have been tested as interventions to limit detrimental changes and physiological deconditioning of the musculoskeletal and cardiovascular systems. The Canadian Institutes of Health Research and the Canadian Space Agency recently provided funding for research focused on Understanding the Health Impact of Inactivity to study the efficacy of exercise countermeasures in a 14-day randomized clinical trial of six-degree head-down tilt bedrest study in older adults aged 55–65 years old (BROA). Here we will describe the development of a multi-modality countermeasure protocol for the BROA campaign that includes upper- and lower-body resistance exercise and head-down tilt cycle ergometry (high-intensity interval and continuous aerobic exercise training). We provide reasoning for the choice of these modalities following review of the latest available information on exercise as a countermeasure for inactivity and spaceflight-related deconditioning. In summary, this paper sets out to review up-to-date exercise countermeasure research from spaceflight and head-down bedrest studies, whilst providing support for the proposed research countermeasure protocols developed for the bedrest study in older adults.

Spectral decomposition of cerebrovascular and cardiovascular interactions in patients prone to postural syncope and healthy controls

We present a framework for the linear parametric analysis of pairwise interactions in bivariate time series in the time and frequency domains, which allows the evaluation of total, causal and instantaneous interactions and connects time- and frequency-domain measures. The framework is applied to physiological time series to investigate the cerebrovascular regulation from the variability of mean cerebral blood flow velocity (CBFV) and mean arterial pressure (MAP), and the cardiovascular regulation from the variability of heart period (HP) and systolic arterial pressure (SAP). We analyze time series acquired at rest and during the early and late phase of head-up tilt in subjects developing orthostatic syncope in response to prolonged postural stress, and in healthy controls. The spectral measures of total, causal and instantaneous coupling between HP and SAP, and between MAP and CBFV, are averaged in the low-frequency band of the spectrum to focus on specific rhythms, and over all frequencies to get time-domain measures. The analysis of cardiovascular interactions indicates that postural stress induces baroreflex involvement, and its prolongation induces baroreflex dysregulation in syncope subjects. The analysis of cerebrovascular interactions indicates that the postural stress enhances the total coupling between MAP and CBFV, and challenges cerebral autoregulation in syncope subjects, while the strong sympathetic activation elicited by prolonged postural stress in healthy controls may determine an increased coupling from CBFV to MAP during late tilt. These results document that the combination of time-domain and spectral measures allows us to obtain an integrated view of cardiovascular and cerebrovascular regulation in healthy and diseased subjects.

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.

Determination of Heart Rate Changes using Simulated Head Up Tilt Test for Syncope Patient Assessment

Home-based self-training can be beneficial to neurocardiogenic patients, particularly for those who experience a decreased heart rate during the clinical head up tilt test (HUT). Many patients, however, may not be able to attend a clinic and/or attend clinics which lack HUT devices. Individualized heart rate prediction based on a simulated HUT (sHUT) model may address this gap in clinical practice. The proposed sHUT model aims to predict whether home-based self-training is an appropriate beneficial intervention based on the calculated decrease in heart rate from the model. The results obtained with the model are in agreement with previous clinical findings with greater than 80% accuracy in identifying patients who could benefit from home training. The predicted home-based training efficacy of syncope against the control group had a corresponding p-value of p<0.0001. Based on these results, physicians may be able to recommend home training as part of online or telemedicine consultation.Clinical Relevance- The simulated Head Up Tilt model predicts the patient-specific efficacy of tilt-training for patients at home diagnosed with syncope.

Dyspnea in Chronic Low Ventricular Preload States

Dyspnea in low-preload states is an underrecognized but growing diagnosis in patients with unexplained dyspnea. Patients can often experience debilitating symptoms at rest and with exertion, as low measured preload often leads to decreased cardiac output and ultimately dyspnea. In the present article, we performed a review of the literature and a multidisciplinary evaluation to understand the pathophysiology, diagnosis, and treatment of dyspnea in low-preload states. We explored selected etiologies and suggested an algorithm to approach unexplained dyspnea. The mainstay of diagnosis remains as invasive cardiopulmonary exercise testing. We concluded with a variety of nonpharmacological and pharmacological therapies, highlighting that a multifactorial approach may lead to the best results.

Tilt Test: A Review

SUMMARY

This review recapitulates the head-up tilt test, which is commonly used for evaluation of orthostatic syndromes and dysautonomia. Tilt test evaluates autonomic system responses to orthostatic stress. Established tilt testing includes monitoring of heart rate and blood pressure; adding capnography and cerebral blood flow monitoring expands its diagnostic yield and allows assessing cerebral blood flow regulation. Common syndromes detectable by the tilt test are neurally mediated syncope (vasodepressor, cardiovagal, or mixed), orthostatic hypotension, postural orthostatic tachycardia syndrome, hypocapnic cerebral hypoperfusion, and orthostatic cerebral hypoperfusion syndrome. This review describes relevant physiology, tilt test protocols, diagnostic criteria for orthostatic syndromes, grading test results, diagnostic accuracy, limitations of the tilt test, and safety considerations.

Post-exercise Body Cooling: Skin Blood Flow, Venous Pooling, and Orthostatic Intolerance

Athletes and certain occupations (e.g., military, firefighters) must navigate unique heat challenges as they perform physical tasks during prolonged heat stress, at times while wearing protective clothing that hinders heat dissipation. Such environments and activities elicit physiological adjustments that prioritize thermoregulatory skin perfusion at the expense of arterial blood pressure and may result in decreases in cerebral blood flow. High levels of skin blood flow combined with an upright body position augment venous pooling and transcapillary fluid shifts in the lower extremities. Combined with sweat-driven reductions in plasma volume, these cardiovascular alterations result in levels of cardiac output that do not meet requirements for brain blood flow, which can lead to orthostatic intolerance and occasionally syncope. Skin surface cooling countermeasures appear to be a promising means of improving orthostatic tolerance via autonomic mechanisms. Increases in transduction of sympathetic activity into vascular resistance, and an increased baroreflex set-point have been shown to be induced by surface cooling implemented after passive heating and other arterial pressure challenges. Considering the further contribution of exercise thermogenesis to orthostatic intolerance risk, our goal in this review is to provide an overview of post-exercise cooling strategies as they are capable of improving autonomic control of the circulation to optimize orthostatic tolerance. We aim to synthesize both basic and applied physiology knowledge available regarding real-world application of cooling strategies to reduce the likelihood of experiencing symptomatic orthostatic intolerance after exercise in the heat.

Transient Orthostatic Hypertension During Head-Up Tilt Test in Young Adults: A Phenotype of Blood Pressure Variability

PURPOSE

The mechanisms underlying orthostatic hypertension (OHT) remain poorly understood. The authors evaluated the cardiovascular, cerebrovascular dynamics, and autonomic response to head-up tilt test (HUTT) in young adults with symptoms of orthostatic intolerance and transient OHT.

METHODS

Forty-four female subjects were included (34 ± 13 years old) and categorized in three groups after a 30-minute 70° passive HUTT: symptomatic patients with OHT (surge of systolic blood pressure ≥20 mm Hg for at least 5 minutes at any given time during HUTT), orthostatic intolerance (symptomatic patients without orthostatic blood pressure changes), and healthy asymptomatic control subjects.

RESULTS

At baseline, OHT patients had lower systolic blood pressure than orthostatic intolerance patients (103 ± 8 vs. 116 ± 10 mm Hg, p < 0.01) and lower baroreflex sensitivity than control subjects (15.8 ± 8.3 vs. 27.1 ± 11.7 ms/mm Hg, p = 0.01). On tilt, cardiac output decreased in OHT patients from 6.1 ± 1.4 L/minute during baseline to 5.2 ± 0.8 L/minute after 10 minutes of HUTT (p = 0.01). In OHT patients at 30 minutes of HUTT, sympathetic efferent heart activity was higher (77.4 ± 14.9 normalized units or nu) than orthostatic intolerant patients (63.5 ± 11.8 nu, p = 0.02) and control subjects (65.8 ± 11.2 nu, p = 0.05). Cerebrovascular resistance in OHT was higher than control subjects after 30 minutes (2.2 ± 0.8 vs. 1.6 ± 0.3 cm/second, respectively, p = 0.02).

CONCLUSIONS

This study demonstrates that transient OHT can occur at any given time during HUTT. These patients exhibit a decrease in cardiac output and a hyperadrenergic response to tilt.

Too much of a good thing: a case report of traumatic drop attacks and syncope due to orthostatic hypertension

Background

Orthostatic hypertension (OHT) is the clinical opposite to orthostatic hypotension and is an under-recognized and poorly understood clinical phenomenon. Patients may experience disabling symptoms such as dizziness, chest pain, and shortness of breath. In addition, OHT is associated with important clinical outcomes such as silent cerebral infarcts and cognitive decline.

Case summary

We present the case of a 67-year-old female who experienced frequent drop attacks with and without transient loss of consciousness causing various injuries. A range of standard diagnostic procedures did not yield an explanation for her symptoms but head-up tilt (HUT) testing showed OHT and induced most of her symptoms. Upon initiation of doxazosin, an alpha-blocking drug, she was free of symptoms and blood pressure response was normal on the repeat HUT test.

Discussion

To our knowledge, this is the first report of syncope due to OHT. Orthostatic hypertension is a heterogeneous condition and may occur in young, otherwise healthy individuals but also in older patients with cardiovascular comorbidities. It is thought that symptoms occur because of excessive venous pooling (causing a drop in cardiac output) or adrenergic hypersensitivity (resulting in cerebral vasoconstriction or acute rise in cardiac afterload). Since our patient had a marked response to an alpha-blocking agent, we think baroreflex hypersensitivity is the most likely cause of her complaints. Though syncope is probably rare, OHT should be regarded as a possible explanation of orthostatic symptoms.

Diffuse optical assessment of cerebral-autoregulation in older adults stratified by cerebrovascular risk

Diagnosis of cerebrovascular disease (CVD) at early stages is essential for preventing sequential complications. CVD is often associated with abnormal cerebral microvasculature, which may impact cerebral-autoregulation (CA). A novel hybrid near-infrared diffuse optical instrument and a finger plethysmograph were used to simultaneously detect low-frequency oscillations (LFOs) of cerebral blood flow (CBF), oxy-hemoglobin concentration ([HbO₂ ]), deoxy-hemoglobin concentration ([Hb]) and mean arterial pressure (MAP) in older adults before, during and after 70° head-up-tilting (HUT). The participants with valid data were divided based on Framingham risk score (FRS, 1-30 points) into low-risk (FRS ≤15, n = 13) and high-risk (FRS >15, n = 11) groups for developing CVD. The LFO gains were determined by transfer function analyses with MAP as the input, and CBF, [HbO₂ ] and [Hb] as the outputs (CA ∝ 1/Gain). At resting-baseline, LFO gains in the high-risk group were relatively lower compared to the low-risk group. The lower baseline gains in the high-risk group may attribute to compensatory mechanisms to maintain stronger steady-state CAs. However, HUT resulted in smaller gain reductions in the high-risk group compared to the low-risk group, suggesting weaker dynamic CAs. LFO gains are potentially valuable biomarkers for early detection of CVD based on associations with CAs.

[Prediction of syncope with nonlinear dynamic analysis during head-up tilt in vasovagal syncope patients]

OBJECTIVE

To quantify the relationship between cerebral blood flow velocity and peripheral blood pressure during hypotension period, aiming to predict the brain hypotension before symptomatic occurrence.

METHODS

Twenty vasovagal syncope (VVS) patients who had a previous clinical history were selected in groups and 20 pair-matched control subjects underwent 70° tilt-up test. The subjects remained supine for 30 minutes before recordings when Doppler probes, electrodes and Finapres device were prepared. After continuous baseline recordings for 10 min, the subjects underwent head up tilt (HUT) test (70°), and were standing upright for 30 minutes or until syncope was imminent. For ethical reasons, the subjects were turned back to supine position immediately after SBP dropped to ≥20 mmHg, when their consciousness persisted. The point of syncope was synchronized for all the subjects by the point SBP reached the minima. Their beat-to-beat blood pressures (BP) were recorded continuously and bilateral middle cerebral artery (MCA) flow velocities were obtained with two 2 MHz Doppler probes from a transcranial Doppler ultrasonography (TCD) system. A nonlinear dynamic method--multimodal pressure flow (MMPF) analysis was introduced to access cerebral autoregulation during different time intervals. We introduced a new indicator--syncope index (SI), which was extracted from blood flow velocity (BFV) signal to evaluate the variation of cerebral vascular tension, and could reflect the deepness of dicrotic notch in BFV signal.

RESULTS

Compared with the syncope index of the baseline value at the beginning of the tilt test, SI in VVS group showed significantly lower when the VVS occurred (0.16±0.10 vs.0.27±0.10,P<0.01),while there was no significant difference in syncope index between the control group at the end of the tilt test and the baseline value at the beginning of the tilt test. For those VVS patients, pulse index and resistance index had no significant change. Syncope index decreased significantly 3 minutes before the point of syncope (0.23±0.07 vs.0.29±0.07,P<0.01).

CONCLUSION

Dynamic regulation is exhausted when vasovagal syncope occurred. Tension decrease of small vessels could have some relationship with loss of the cerebral autoregulation capability. The proposed syncope index could be a useful parameter in predicting syncope of VVS patients since it decreased significantly up to 3 minutes earlier from the point of syncope.

Association of Orthostatic Hypotension Timing With Clinical Events in Adults With Diabetes and Hypertension: Results From the ACCORD Trial

OBJECTIVE

To determine the effects of orthostatic hypotension (OH) measurement timing on its associations with dizziness, falls, fractures, cardiovascular disease (CVD), and mortality.

METHODS

We analyzed OH measurements from the Action to Control Cardiovascular Risk in Diabetes BP trial, which evaluated two blood pressure (BP) goals (systolic BP [SBP] < 120 mm Hg vs. SBP < 140 mm Hg) and incident CVD among adults with diabetes and hypertension. Seated BP was measured after 5 minutes of rest at baseline and follow-up visits (12 months, 48 months, and exit). Standing BP was measured 3 consecutive times (M1-M3) after standing, starting at 1 minute with each measurement separated by 1 minute. Consensus OH was defined as a drop in SBP ≥ 20 mm Hg or diastolic BP (DBP) ≥ 10 mm Hg. Participants were asked about orthostatic dizziness, recent falls, and recent fractures, and underwent surveillance for CVD events and all-cause mortality.

RESULTS

There were 4,268 participants with OH assessments over 8,450 visits (mean age 62.6 years [SD = 6.6]; 46.6% female; 22.3% black). Although all measures of consensus OH were significantly associated with dizziness, none were associated with falls, and only M2 (~3 minutes) was significantly associated with fractures. No measurements were associated with CVD events, but later measurements were significantly associated with mortality. BP treatment goal did not increase risk of OH regardless of timing. Associations were not consistently improved by the mean or minimum of M1-M3.

CONCLUSION

In this population of adults with hypertension and diabetes, neither single time nor set of measurements were clearly superior with regard to outcomes. These findings support the use of a flexibly timed, single measurement to assess OH in clinical practice.

CLINICAL TRIALS REGISTRATION

Trial Number NCT00000620.

Atypical Prodromal Symptoms Help to Distinguish Patients With Psychogenic Nonsyncopal Collapse Among Youth Referred for Fainting

BACKGROUND

Distinguishing patients with psychogenic nonsyncopal collapse (PNSC), a conversion disorder that resembles syncope, can pose a difficult clinical challenge. Using the open-ended question "what does it feel like to faint?," the present study aimed to characterize how patients with PNSC perceive and communicate the prodromal symptoms associated with their attacks by comparing narratives between patients with PNSC and those with syncope.

METHODS

During a 42-month database-type study of tilt-table diagnoses, all patients with a history of fainting were asked the open-ended question. Symptom descriptions were compared, qualitatively and quantitatively, between patients with PNSC and those with tilt-induced syncope (n = 121 in both cohorts).

RESULTS

Twenty-nine patients (24%) diagnosed with PNSC and eight (6.6%) diagnosed with syncope either denied having any prodromal symptoms or could not recall any symptoms (P < 0.001). Among patients who reported prodromal symptoms, patient narratives led to the formation of 26 symptom categories. Symptom frequencies differed between cohorts in 19 of the symptom categories (each P value <0.05). Qualitative differences in the descriptions of symptoms were often present, even when symptom frequencies did not differ. More patients with PNSC described atypical symptoms than patients with syncope, 54 of 92 (58.7%) versus eight of 113 (7.1%), P < 0.001.

CONCLUSIONS

Symptom narratives can help to distinguish patients with PNSC from those with syncope. The use of a single, open-ended question as a screening tool for conversion disorder has immediate clinical relevance because it can be instituted easily in a busy clinical setting.

Is ivabradine a wonder drug for atypical POTS?

Syncope is a sudden loss and gain of consciousness. Traditionally, it is caused by the abnormalities of neurological, cardiac or vasovagal systems. We present a case of a 19-year-old woman presenting with recurrent syncopal episodes with no apparent cause. Examination and investigations were unremarkable for any aetiology except positive tilt tests for postural orthostatic tachycardia syndrome. The purpose of this report is to make physicians aware of the unique presentation of this rare aetiology with recurrent syncopal episodes and the novel management approach.

Autonomic Disorders

Autonomic complaints are frequently encountered in clinical practice. They can be due to primary autonomic disorders or secondary to other medical conditions. Primary autonomic disorders can be categorized as orthostatic intolerance syndromes and small fiber neuropathies; the latter are associated with autonomic failure, pain, or their combinations. The review outlines orthostatic intolerance syndromes (neurally mediated syncope, orthostatic hypotension, postural tachycardia syndrome, inappropriate sinus tachycardia, orthostatic cerebral hypoperfusion syndrome, and hypocapnic cerebral hypoperfusion) and small fiber neuropathies (sensory/autonomic/mixed, acute/subacute/chronic, idiopathic/secondary, inflammatory and noninflammatory). Several specific autonomic syndromes (diabetic neuropathy, primary hyperhidrosis, paroxysmal sympathetic hyperactivity, autonomic dysreflexia), neurogenic bladder, and gastrointestinal motility disorders are discussed as well.

Associations Between Autonomic and Orthostatic Self-report and Physician Ratings of Orthostatic Intolerance in Youth

PURPOSE

There is no known biological marker or physical assessment to diagnose chronic fatigue syndrome (CFS), leaving physicians to heavily rely on self-report measures regarding the symptoms associated with CFS. Common symptoms of CFS include difficulty sleeping, joint pain, headaches, sore throat, cognitive dysfunction, physical exhaustion, dizziness, and nausea. Because of the overlap among CFS symptoms and autonomic functioning, we examined the association between 2 self-report measures of orthostatic and autonomic symptoms and a physician's report of autonomic functioning (measures of changes in blood pressure and pulse) to further understand the association among autonomic functioning within individuals with symptoms of CFS.

METHODS

With data from an ongoing study, we used independent t tests and Pearson correlation tests to assess the association among the orthostatic domain from the DePaul Symptom Questionnaire, Autonomic Symptom Checklist composite scores, and the physician's assessment of orthostatic intolerance obtained from a sample of 191 participants, 42 who were healthy controls.

FINDINGS

No significant demographic differences were found between the CFS-like group and the healthy controls. Results indicate a significant correlation between orthostatic and autonomic functioning (r = 0.58) and a correlation with a low effect size among autonomic functioning and physician measures of orthostatic functioning (r = -0.01 to 0.29). However, fewer correlations were found between self-reported symptoms of orthostatic functioning and the physician's measures of orthostatic functioning.

IMPLICATIONS

These results suggest that although orthostatic dysfunction is reported in children and adolescents with CFS-like symptoms, the physical measures of autonomic functioning in this study were unable to detect these symptoms.

Cerebral Perfusion Monitoring Using Near-Infrared Spectroscopy During Head-Up Tilt Table Test in Patients With Orthostatic Intolerance

The head-up tilt table test (HUT) is one of the primary clinical examinations for evaluating orthostatic intolerance (OI). HUT can be divided into three phases: dynamic tilt phase (supine to tilt up), static tilt phase (remain tilted at 70°), and post tilt phase (tilt down back to supine position). Commonly, blood pressure (BP) and heart rate (HR) are monitored to observe for OI symptoms, but are indirect measurements of cerebral perfusion and can lead to inaccurate HUT evaluation. In this study, we implemented a 108-channel near-infrared spectroscopy (NIRS) probe to characterize HUT performance by monitoring cerebral hemodynamic changes for healthy controls (HCs), OI patients with normal HUT results, and OI patients with positive HUT results: vasovagal syncope (VS), postural orthostatic tachycardia syndrome (POTS), orthostatic hypotension (OH), and orthostatic hypertension (OHT). By the end of the static tilt phase, OI patients typically did not show a complete recovery back to baseline cerebral oxygenation and total blood volume compared to HCs. We characterized the return to cerebral homeostasis by polynomial fitting total blood volume changes and determining the inflection point. The OI patients with normal HUT results, VS, OH, or OHT showed a delay in the return to cerebral homeostasis compared to the HC group during HUT.

Orthostatic hypotension and dementia incidence: links and implications

Orthostatic hypotension (OH) is a common condition, particularly in patients with α-synucleinopathies such as Parkinson's disease, and has a significant impact on activities of daily living and quality of life. Recent data suggest an association with cognitive impairment. Herein, we review the evidence that OH increases the odds of incident mild cognitive impairment and dementia. Potential mechanisms underlying the putative relationship are discussed, including cerebral hypoperfusion, supine hypertension, white matter hyperintensities, and neurodegeneration. Finally, we highlight the challenges with respect to treatment and the negative impact on the quality of life and long-term prognosis presented by the coexistence of OH and dementia. Large population-based studies have reported that OH is associated with about a 20% increased risk of dementia in the general population, while smaller cohort studies suggest an even greater effect in patients with α-synucleinopathies (3- to 7-fold higher than controls). Ultimately, OH exposure is difficult to quantify, predominantly limited to pressure regulation during a one-time orthostatic challenge, and the causative association with dementia may turn out to be bidirectional, especially in α-synucleinopathies. Early diagnosis and treatment of OH may improve long-term prognosis.

Signs of autonomic arousal precede tilt-induced psychogenic nonsyncopal collapse among youth

Characterizing the physiologic changes leading up to psychogenic nonsyncopal collapse (PNSC) may help to elucidate the processes that cause paroxysmal functional neurological symptom disorders and to clinically distinguish PNSC from syncope. Thus, we aimed to characterize preictal sweat rate, heart rate, and systolic blood pressure changes among patients with tilt-induced PNSC compared to patients with tilt-induced neurally mediated syncope. The presence of increased preictal sweating was compared between groups. Heart rates and systolic blood pressures were compared from the recumbent and tilted baselines to the periods 120 s and 30 s prior to PNSC and syncope. Patients with PNSC (n = 44) were more likely than patients with syncope (n = 44) to have preictal increases in sweating, n = 31 (70.5%) versus n = 21 (47.7%), p = 0.03, although all patients with syncope eventually developed a sweat response. Comparing the recumbent baseline to the period 30 s prior to PNSC, blood pressure (112 ± 9 versus 129 ± 13 mmHg, p < 0.001) and heart rate (76 ± 12 versus 119 ± 22 bpm, p < 0.001) increased. Similarly, comparing the tilted baseline to the period 30 s prior to PNSC, blood pressure (118 ± 12 versus 129 ± 13 mmHg, p < 0.001) and heart rate (95 ± 15 versus 119 ± 22 bpm, p < 0.001) increased. Preictal blood pressure and heart rate differed significantly between patients with PNSC and patients with syncope. In conclusion, signs of autonomic arousal (increased sweating, heart rate, and blood pressure) often precede tilt-induced PNSC. Sweating prior to fainting may not be useful in distinguishing PNSC from neurally mediated syncope.

Orthostatic Hypotension and Symptoms in the AASK Trial

BACKGROUND

Multiple definitions are used to characterize orthostatic hypotension (OH), but the degree to which these definitions correspond with orthostatic symptoms is unknown.

METHODS

We analyzed data from African American Study of Kidney Disease and Hypertension (AASK), a randomized trial of African Americans with hypertension and kidney disease, to characterize the relationship between OH definitions and self-reported syncope, dizziness, or light-headedness. Orthostatic changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), or heart rate (HR) were determined each visit after standing 2:45 minutes. OH was defined using the consensus definition (a drop in SBP ≥20 mm Hg or DBP ≥10 mm Hg) or an often used clinical substitute based on HR (an increase ≥20 bpm).

RESULTS

Among 1,094 participants (mean age 54.5 ± 10.7 years, 38.9% female), there were 52,636 visits (mean 48/person). Mean resting SBP, DBP, and HR at baseline were 147.7 ± 22.3 mm Hg, 92.2 ± 13.4 mm Hg, and 71.1 ± 11.7 bpm, respectively. While the OH consensus definition was associated with syncope (odds ratio 2.49; 95% confidence interval: 1.13, 5.51), dizziness (1.89; 1.53, 2.33), and light-headedness (1.84; 1.52, 2.23), the clinical HR definition was only associated with dizziness (1.28; 1.07, 1.52). None of the OH components (SBP, DBP, or HR) reflected a natural threshold in the prevalence of symptoms; definitions using each of the 3 components were highly specific (≥96%) with low sensitivity (1-5%).

CONCLUSIONS

While the consensus definition was more strongly associated with symptoms, OH definitions did not reflect natural thresholds in symptoms and were insensitive. This implies that the absence of OH using either consensus or clinical definitions does not exclude orthostatic symptoms, which has implications for evaluating clinical events like falls.

CLINICAL TRIALS REGISTRATION

Trial Number: NCT01206062 (clinicaltrials.gov).

Patterns of Orthostatic Blood Pressure Changes in Patients with Orthostatic Hypotension

Background and Purpose

The objective of this study was to determine the patterns of blood pressure (BP) changes during the head-up tilt (HUT) test, particularly in terms of its clinical significance for patients with orthostatic hypotension (OH).

Methods

OH was divided into four categories based on systolic BP changes occurring within the first 10 minutes of the HUT test: sustained orthostatic hypotension (SOH), progressive orthostatic hypotension (POH), orthostatic hypotension with partial recovery (OHPR), and transient orthostatic hypotension (TOH).

Results

In total, 151 patients were analyzed: 65 with SOH, 38 with POH, 21 with OHPR, and 27 with TOH. POH patients exhibited the greatest reduction in systolic BP after HUT and were also the most likely to develop symptoms requiring early termination of the HUT test (42.1%, p<0.001). Additionally, SOH patients exhibited smaller heart-rate variation with deep breathing values (p=0.003) and Valsalva ratios (p=0.022) compared to POH patients. The sweat volume was greatest in OHPR patients.

Conclusions

Clinical characteristics, including the findings of autonomic function tests, differed between the OH patient groups. This might reflect differences in the underlying pathophysiologic mechanisms. Determining the patterns of BP changes during the HUT test may facilitate the development of effective management strategies in patients with OH.

Cardiovascular and Cerebral Hemodynamics in Asymptomatic Healthy Subjects With/Without Abnormal Head-up Tilt Test Versus Recurrent Fainters

PURPOSE

The aim of this study was to compare hemodynamic and autonomic responses during head-up tilt test (HUTT) between healthy volunteers and patients with a history of fainting and confirmed vasovagal syncope. We hypothesize that the autonomic and hemodynamic physiologic responses remain intact during orthostatic stress in people without previous fainting and negative HUTT, but deteriorate similarly in patients with recurrent vasovagal syncope and in asymptomatic healthy subjects who develop a vasovagal response during HUTT.

METHODS

The study included 57 asymptomatic healthy volunteers (42% women, mean age 23.7 ± 3.6 years) categorized as negative HUTT (n = 41) and positive HUTT (n = 16). They were compared with 14 patients (50% women, mean age 24.2 ± 6.1 years) with previous spontaneous recurrent syncope and inducible vasovagal response during HUTT. Cerebral and cardiovascular hemodynamic variables were assessed noninvasively during the HUTT in each participant.

RESULTS

In all patients with recurrent syncope, tilt was positive after a mean delay of 15.6 ± 8.6 minutes and did not differ from the time to syncope observed after 19.6 ± 6.9 minutes in asymptomatic healthy subjects with a positive test. A significant decrease throughout the tilting was observed in the blood pressure, peripheral resistances, cerebral blood flow, and vascular efferent sympathetic regulation in both groups of subjects with a positive test.

CONCLUSIONS

This study shows that there are subjects, without a history of syncope, who have a positive HUTT with hemodynamic and autonomic responses alike to patients with confirmed vasovagal syncope, precluding them to be selected as controls in vasovagal syncope studies.

Transcranial Doppler in autonomic testing: standards and clinical applications

When cerebral blood flow falls below a critical limit, syncope occurs and, if prolonged, ischemia leads to neuronal death. The cerebral circulation has its own complex finely tuned autoregulatory mechanisms to ensure blood supply to the brain can meet the high metabolic demands of the underlying neuronal tissue. This involves the interplay between myogenic and metabolic mechanisms, input from noradrenergic and cholinergic neurons, and the release of vasoactive substrates, including adenosine from astrocytes and nitric oxide from the endothelium. Transcranial Doppler (TCD) is a non-invasive technique that provides real-time measurements of cerebral blood flow velocity. TCD can be very useful in the work-up of a patient with recurrent syncope. Cerebral autoregulatory mechanisms help defend the brain against hypoperfusion when perfusion pressure falls on standing. Syncope occurs when hypotension is severe, and susceptibility increases with hyperventilation, hypocapnia, and cerebral vasoconstriction. Here we review clinical standards for the acquisition and analysis of TCD signals in the autonomic laboratory and the multiple methods available to assess cerebral autoregulation. We also describe the control of cerebral blood flow in autonomic disorders and functional syndromes.